Nanozymes for Environmental Engineering [1 ed.] 3030682293, 9783030682293

Table of contents :
Preface
Contents
About the Editors
Chapter 1: Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes for Target Specific Binding, Sensing ...
1.1 Introduction
1.1.1 Functionalization of Nanomaterials Using Amino Acids
1.2 Synthesis of Amino Acids Functionalized Nanoparticles
1.2.1 Amino Acids Mediated Synthesis of Nanoparticles
1.2.2 Post-functionalization of Nanoparticles Using Amino Acids
1.3 Optical Properties of Amino Acid Functionalized Nanoparticles
1.3.1 Optical Properties of Metal Nanoparticles - Surface Plasmon Resonant Absorption
1.3.2 Optical Properties of Semiconductor Nanoparticles - Fluorescence Properties
1.3.3 Chiro-optical Properties of Amino Acids Functionalized Semiconductor Nanoparticles
1.4 Thermodynamics of Amino Acids Binding on Nanoparticles Surface
1.5 Substrate Specific Binding - Electrostatic and Chiral
1.5.1 Protein and DNA Binding to Nanoparticles Surface
1.5.2 Enantioselective Binding and Chiral Separation
1.6 Amino Acids Functionalized Nanoparticles in Sensing Applications
1.6.1 Colorimetric Sensing
1.6.2 Fluorescence Sensing
1.7 Catalytic Role as Nanozymes
1.7.1 Metal Nanoparticles Containing Nanozyems
1.7.2 Metal Oxide Nanoparticles Containing Nanozymes
1.8 Conclusion and Prospects
References
Chapter 2: Thermal Decomposition Routes for Magnetic Nanoparticles: Development of Next-Generation Artificial Enzymes, Their P...
2.1 Introduction
2.2 Nanoparticle Synthesis
2.2.1 Nanoparticle Reaction Kinetics
2.2.2 Nanoparticle Reaction Mechanism
2.3 Reaction Conditions
2.3.1 Reaction Temperatures
2.3.2 Iron Oleate Precursors
2.3.3 Surfactant Quality
2.3.4 Surfactants and Additives
2.3.5 Heating Rate and Reflux Time (Including Aging Factor)
2.4 Structural and Magnetic Properties
2.4.1 Nanoparticle Shape
2.4.2 Nanoparticle Phase
2.4.3 Nanoparticle Magnetism
2.5 Biological Applications - The Importance of Phase Transfer
2.6 Conclusion
References
Chapter 3: Nanozymes: Emerging Nanomaterials to Detect Toxic Ions
3.1 Introduction
3.2 Detection of Hg2+ Using Nanozymes
3.2.1 Based on Target Promoted Activity
3.2.2 Based on Target Inhibited Activity
3.2.3 Based on Other Mechanisms
3.3 Detection of Ag+ Using Nanozymes
3.3.1 Based on Target Inhibited Activity
3.3.2 Based on Target Promoted Activity
3.4 Detection of Arsenate/Arsenite Using Nanozymes
3.5 Detection of Pb2+ Using Nanozymes
3.6 Detection of [Cr2O7]2- Using Nanozymes
3.7 Detection of Halide Ions Using Nanozymes
3.8 Detection of Phosphates Using Nanozymes
3.9 Detection of S-containing Species Using Nanozymes
3.10 Detection of Other Ions Using Nanozymes
3.11 Trends and Challenges
3.12 Conclusions
References
Chapter 4: Applications of Nanozymes in Wastewater Treatment
4.1 Introduction
4.2 Importance of Enzymes in Wastewater Treatment
4.3 Nanoparticles as Enzyme Mimics
4.3.1 Iron Nanoparticles as Nanozymes
4.3.2 Manganese Nanoparticles as Nanozymes
4.3.3 Copper Nanoparticles as Nanozymes
4.3.4 Gold Nanoparticles as Nanozymes
4.3.5 Platinum Nanoparticles as Nanozymes
4.3.6 Hybrid Nanozymes
4.4 Conclusions and Future Scope
References
Chapter 5: Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic Activity of NanoZymes
5.1 Introduction
5.2 NanoZymes
5.3 Aptamers
5.4 NanoZymes for Pollutants Detection
5.4.1 Heavy Metal
5.4.2 Pathogens
5.4.3 Organic Pollutants
5.4.3.1 Toxins
5.4.3.2 Antibiotics
5.4.3.3 Pesticides
5.4.3.4 Dyes
5.5 Summary and Future Prospects
References
Chapter 6: Nanozyme-Based Sensors for Pesticide Detection
6.1 Introduction
6.2 Chemical Classification of Pesticides
6.2.1 Organochlorines
6.2.2 Organophosphates
6.2.3 Carbamates
6.2.4 Pyrethroids
6.2.5 Others
6.2.5.1 Acetamiprid
6.2.5.2 Atrazine
6.3 Nanozyme Based Sensors
6.3.1 Organophosphorus Pesticide Sensors
6.3.1.1 Acetylcholinesterase-Based Sensor with Oxidase-Mimic Nanozyme
6.3.1.2 Acetylcholinesterase Based Sensor with Peroxidase-Mimic Nanozyme
6.3.1.3 Colorimetric or Fluorometric Inhibition in the Absence of Another Natural Enzyme
6.3.1.4 Chemiluminescent Sensor Array for Multiple Pesticide Detection
6.3.1.5 Chemiluminescence Switching Assay
6.3.1.6 Nanozyme-Based Immunoassays
6.3.1.7 Nanozyme Aptasensors
6.3.1.8 Phosphatase-Mimic Nanozymes - A Dual Role
6.3.1.9 Electrochemical Sensors
6.3.2 Acetamiprid Sensors
6.3.3 Atrazine Sensors
6.4 Conclusion
References
Chapter 7: Metal-Based Nanozyme: Strategies to Modulate the Catalytic Activity to Realize Environment Application
7.1 Introduction
7.2 Strategies to Modulate the Activities of Nanozymes
7.2.1 pH
7.2.2 Temperature
7.2.3 Size
7.2.4 Shape
7.2.5 Light
7.2.6 Surface Modification
7.2.7 Surface Charge
7.3 Metallic Nanoparticles
7.3.1 Gold Nanoparticles
7.3.2 Silver Nanoparticles
7.3.3 Platinum Nanoparticles
7.3.4 Palladium Nanoparticles
7.4 Bimetallic Nanoparticles
7.5 Trimetallic Nanoparticles
7.6 Modulators for Enhancing the Catalytic Efficiency of Nanozymes
7.6.1 Metal Ions
7.6.2 Adenosine Supplements
7.6.3 Oligonucleotides
7.6.4 Chemical Compounds
7.7 Environmetal Application of Metallozyme
7.7.1 Pesticides Detection
7.7.2 Antibiotic Residues
7.7.3 Phenolic Residues
7.7.4 Pathogens
7.7.5 Toxic Ions
7.8 Conclusion and Future Prospects
References
Chapter 8: Nanozymes in Environmental Protection
8.1 Introduction
8.2 Toxic Ions Detection
8.2.1 Heavy Metal Ions Detection
8.2.2 Toxic Anions Detection
8.3 Organic Pollutants Degradation
8.3.1 Organic Compounds Degradation
8.3.2 Nerve Agents Degradation
8.4 Biofilm Formation Inhibition
8.5 Summary and Outlook
References

Citation preview

Environmental Chemistry for a Sustainable World 63

Hemant Kumar Daima Navya PN Eric Lichtfouse   Editors

Nanozymes for Environmental Engineering

Environmental Chemistry for a Sustainable World Volume 63

Series Editors Eric Lichtfouse , Aix Marseille University, CNRS, IRD, INRA, Coll France, CEREGE, Aix en Provence, France Jan Schwarzbauer, RWTH Aachen University, Aachen, Germany Didier Robert, CNRS, European Laboratory for Catalysis and Surface Sciences, Saint-Avold, France

Environmental chemistry is a fast developing science aimed at deciphering fundamental mechanisms ruling the behaviour of pollutants in ecosystems. Applying this knowledge to current environmental issues leads to the remediation of environmental media, and to new, low energy, low emission, sustainable processes. The topics that would be covered in this series, but not limited to, are major achievements of environmental chemistry for sustainable development such as nanotech applications; biofuels, solar and alternative energies; pollutants in air, water, soil and food; greenhouse gases; radioactive pollutants; endocrine disruptors and other pharmaceuticals; pollutant archives; ecotoxicology and health risk; pollutant remediation; geoengineering; green chemistry; contributions bridging unexpectedly far disciplines such as environmental chemistry and social sciences; and participatory research with end-users. The books series will encompass all scientific aspects of environmental chemistry through a multidisciplinary approach: Environmental Engineering/Biotechnology, Waste Management/Waste Technology, Pollution, general, Atmospheric Protection/ Air Quality Control/Air Pollution, Analytical Chemistry. Other disciplines include: Agriculture, Building Types and Functions, Climate Change, Ecosystems, Ecotoxicology, Geochemistry, Nanochemistry, Nanotechnology and Microengineering, Social Sciences. The aim of the series is to publish 2 to 4 book per year. Audience: Academic/Corporate/Hospital Libraries, Practitioners / Professionals, Scientists / Researchers, Lecturers/Tutors, Graduates, Type of books (edited volumes, monographs, proceedings, textbooks, etc.). Edited volumes: List of subject areas the series will cover: • Analytical chemistry, novel methods • Biofuels, alternative energies • Biogeochemistry • Carbon cycle and sequestration • Climate change, greenhouse gases • Ecotoxicology and risk assessment • Environmental chemistry and the society • Genomics and environmental chemistry • Geoengineering • Green chemistry • Health and environmental chemistry • Internet and environmental chemistry • Nanotechnologies • Novel concepts in environmental chemistry • Organic pollutants, endocrine disrupters • Participatory research with end-users • Pesticides • Pollution of water, soils, air and food • Radioactive pollutants • Remediation technologies • Waste treatment and recycling • Toxic metals

More information about this series at http://www.springer.com/series/11480

Hemant Kumar Daima • Navya PN Eric Lichtfouse Editors

Nanozymes for Environmental Engineering

Editors Hemant Kumar Daima Amity Center for Nanobiotechnology and Nanomedicine (ACNN) Amity University Rajasthan Jaipur, Rajasthan, India

Navya PN Department of Biotechnology Bannari Amman Institute of Technology Erode, Tamilnadu, India

Eric Lichtfouse Aix Marseille University, CNRS, IRD, INRA, Coll France, CEREGE Aix en Provence, France

ISSN 2213-7114 ISSN 2213-7122 (electronic) Environmental Chemistry for a Sustainable World ISBN 978-3-030-68229-3 ISBN 978-3-030-68230-9 (eBook) https://doi.org/10.1007/978-3-030-68230-9 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

This book is dedicated to my research team and students

Preface

Protection of the environment is essential because pollution has become a global problem with many adverse effects on life and ecosystems. For that, remediation strategies and techniques have been designed, yet they are still limited. Here, the recent development of nanotechnology opens a new vista for environmental remediation. In particular, nanomaterials displaying enzyme-like activities, named “nanozymes,” appear very promising for environmental monitoring, contaminant detection, microbial management, and degradation of organic pollutants. Nanomaterials including metallic, metal oxides, and carbon-based nanoparticles with nanozymes activities have been synthesized. These nanozymes have similar activities as natural peroxidase, oxidase, superoxide dismutase, and catalase enzymes. Nanozymes have several advantages, yet they suffer from several limitations such as low catalytic efficiency, less substrate selectivity, biocompatibility, and lack of engineering of the active sites. This book reviews the latest developments and applications of nanozymes in environmental science. In Chap. 1, Selvakannan et al. review the physicochemical properties which confer enzyme properties to nanomaterials, using techniques such as surface modification with amino acids. They also present applications of amino acidfunctionalized nanomaterials to sensing, substrate specific binding to chiral separation (Fig. 1). Singh and Daima present in Chap. 2 the synthesis of iron oxide nanoparticles by thermal decomposition of iron oleate precursor and their biological applications as nanozymes using phase transfer mechanisms. They focus on reaction mechanism and parameters such as temperature, heating rate, reflux time, and addition of surfactants and additives. In Chap. 3, Niu et al. review nanozymes as detectors of Hg2+, Ag+, arsenate/arsenite, Pb2+, [Cr2O7]2
, halide ions, phosphates, and S-containing species based on activity modulation. Removal of contaminants from wastewater using nanozymes is then discussed by Yata in Chap. 4, with emphasis on mechanisms. In Chap. 5, Kalyani et al. explain the principle of the aptamer-nanozyme sensing and present applications in nanozyme-based sensing of pollutants. Detection of pesticides in food and environmental samples by molecularly imprinted polymers vii

viii

Preface

Fig. 1 Amino acids functionalized inorganic nanoparticles and their characteristic physio-chemical properties. Asp aspartic acid, Cys cysteine, Lys lysine, Hys hystidine, Trp tryptophan, Tyr tyrosine

and aptamer-based nanozyme sensors is further outlined by Prasad et al. in Chap. 6, with focus on nanozyme-based sensing platforms to be used on-site. These platforms offer a significant advantage over conventional sensors that rely on bulky equipment. In Chap. 7, Bhagat et al. present metal-based nanozymes and their applications for theranostics, and for removal and detection of organic pollutants. Here, they devote a section to strategies for improving the catalytic efficiency of metallic nanozymes. The final chapter by Zhang and Hu reviews representative nanozymes for pollutants detection, organic pollutants degradation, and biofilm inhibition. We extend our congratulations to all the authors; we sincerely thank them for accepting our invitation. Their commitment and contribution has gathered scattered information into comprehensive chapters to produce this book. Further, we acknowledge all reviewers who have provided valuable suggestions to improve the quality of the chapters. We further thank the team of Springer Nature for their substantial support and cooperation to produce this book. We hope that this book will serve to

Preface

ix

update the knowledge and be helpful to students, engineers, professors, scientists, and policy makers. At the end, we must acknowledge almighty “God” and members of our families, who have provided the motivation and strength to work on the book since its conception. Jaipur, Rajasthan, India Erode, Tamilnadu, India Aix en Provence, France

Hemant Kumar Daima Navya PN Eric Lichtfouse

Contents

1

2

Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes for Target Specific Binding, Sensing and Catalytic Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Selvakannan Periasamy, Deepa Dumbre, Libitha Babu, Srinivasan Madapusi, Sarvesh Kumar Soni, Hemant Kumar Daima, and Suresh Kumar Bhargava Thermal Decomposition Routes for Magnetic Nanoparticles: Development of Next-Generation Artificial Enzymes, Their Phase Transfer and Biological Applications . . . . . . . . . . . . . . . Mandeep Singh and Hemant Kumar Daima

1

35

3

Nanozymes: Emerging Nanomaterials to Detect Toxic Ions . . . . . . . . Xiangheng Niu, Xin Li, and Xuechao Xu

71

4

Applications of Nanozymes in Wastewater Treatment . . . . . . . . . . . Vinod Kumar Yata

95

5

Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic Activity of NanoZymes . . . . . . . . . . . . . . 111 Neeti Kalyani, Bandhan Chatterjee, and Tarun Kumar Sharma

6

Nanozyme-Based Sensors for Pesticide Detection . . . . . . . . . . . . . . . 145 Sanjana Naveen Prasad, Vipul Bansal, and Rajesh Ramanathan

7

Metal-Based Nanozyme: Strategies to Modulate the Catalytic Activity to Realize Environment Application . . . . . . . . . . . . . . . . . . . 177 Stuti Bhagat, Juhi Shah, and Sanjay Singh

8

Nanozymes in Environmental Protection . . . . . . . . . . . . . . . . . . . . . . 213 Sheng Zhang and Yihui Hu

xi

About the Editors

Hemant Kumar Daima is an Indian scientist, academician, and administrator. He is a professor at Amity University Rajasthan, India, in-charge of Amity University Science & Instrumentation Center-II (AUSIC-II), founding member and coordinator of Amity Center for Nanobiotechnology and Nanomedicine (ACNN), and “honorary visiting scientist” at RMIT University, Australia. Dr. Daima has expertise in designing nanoparticles with controlled physicochemical properties by employing green chemistry routes. He has demonstrated the importance of surface functionalization to control corona of nanomaterials, which dictates nanomaterials interaction at nano-bio interface. His research findings have revealed guiding principles involved in rational nanoparticle design strategies for biomedical applications. Currently, Dr. Daima’s team is working on the development of functional organic and inorganic nanomaterials for drug/gene delivery, biosensors, management of multi-drug resistant (MDR) bacteria, nanozyme activities, and medical devices. Dr. Daima is editorial board member and reviewer of leading international publishers in the field of nanotechnology, nanotoxicology, and nanomedicine, with >50 peer-reviewed, high-impact publications to date. Dr. Daima has presented his research worldwide, and he is member of several scientific/professional bodies. He is a recipient of numerous international fellowships/ awards and has established the Nano-Bio Interfacial

xiii

xiv

About the Editors

Research Laboratory (NBIRL) to undertake highquality fundamental and applied research. He obtained his MSc (biotechnology) from the University of Rajasthan, India, PhD (nanobiotechnology) from RMIT University, Australia. Email: [email protected], [email protected]

Navya PN is working as assistant professor at Bannari Amman Institute of Technology, Erode, India. Previously, she has worked as assistant professor at Siddaganga Institute of Technology, India. After receiving an international scholarship, she is planning to move to Japan for her research activities. She holds an MTech degree from Manipal University, India, and a BE from Siddaganga Institute of Technology, India. Navya’s research interests are development of biocompatible nanoparticles with suitable functionalization for a range of biomedical, environmental, and industrial applications. She has published several high-impact research papers in journals of international repute. She is a cofounder of Nano-Bio Interfacial Research Laboratory (NBIRL). Navya is member of several professional bodies, editor of Nanoscience in Medicine (Springer Nature), and reviewer for prestigious journals in the field of nanotechnology. Navya is recipient of numerous international fellowships/awards including Sakura Exchange Fellowship in Science from JST, Japan, and research fellowship from UNSW Sydney, Australia, as well as MEXT scholarship of Japan.

Eric Lichtfouse is an environmental chemist working at the University of Aix-Marseille, France. He has invented carbon-13 dating, a method allowing to measure the relative age of organic molecules occurring in different temporal pools of complex media. Dr. Lichtfouse is teaching scientific writing and communication and has published the book Scientific Writing for Impact Factors, which includes a new tool – the Micro-Article – to identify the novelty of research results. He is founder and chief editor of scientific journals and series in environmental chemistry and agriculture. Dr. Lichtfouse has founded the European

About the Editors

xv

Association of Chemistry and the Environment. He is a recipient of the Analytical Chemistry Prize by the French Chemical Society, the Grand Prize of the Universities of Nancy and Metz, and a Journal Citation Award by the Essential Indicators. https://scholar.google.fr/citations? user¼MOKMNegAAAAJ, https://cv.archives-ouvertes. fr/eric-lichtfouse Email: [email protected]

Chapter 1

Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes for Target Specific Binding, Sensing and Catalytic Applications Selvakannan Periasamy, Deepa Dumbre, Libitha Babu, Srinivasan Madapusi, Sarvesh Kumar Soni, Hemant Kumar Daima, and Suresh Kumar Bhargava

Abstract The design and synthesis of surface engineered functional inorganic nanomaterials for environmental applications is a long-standing goal of biomimetic research. Further developments in using nanomaterials for environmental engineering applications rely upon their surface modification, efficient sensing, stability under harsh conditions, biocompatibility, and less adverse environmental impact. Therefore, in this chapter, we review the amino acid functionalized inorganic nanomaterials, class of emerging materials that can address the afore-mentioned challenges to realize their environmental applications. These nanomaterials structurally mimic the characteristics of natural enzymes chirality, molecular recognition catalytic properties as well as possess the inherent electronic, optical, and catalytic properties of nanoparticles. First, we discuss about various synthetic aspects currently practiced for the synthesis of amino acids functionalized inorganic nanomaterials including metals, metal oxides, semiconductors, and clays. Rationale behind in synthesizing these class of materials is elucidated based on their characteristic chiro-optical properties that present a unique combination of chirality driven optical properties of amino acids with the surface plasmon resonant absorption and photoluminescent properties of metal and semiconductor nanoparticles. The chapter also highlights the nature of interaction and thermodynamic aspects of bonding between amino acid and nanoparticles, studied using isothermal titration calorimetric and spectroscopic

S. Periasamy (*) · D. Dumbre · L. Babu · S. Madapusi · S. K. Soni · S. K. Bhargava Centre for Advanced Materials and Industrial Chemistry, School of Science, RMIT University, Melbourne, VIC, Australia e-mail: [email protected] H. K. Daima (*) Amity Center for Nanobiotechnology and Nanomedicine (ACNN), Amity University Rajasthan, Jaipur, Rajasthan, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 H. K. Daima et al. (eds.), Nanozymes for Environmental Engineering, Environmental Chemistry for a Sustainable World 63, https://doi.org/10.1007/978-3-030-68230-9_1

1

2

S. Periasamy et al.

techniques. Subsequently, detailed description of the molecular and ion recognition properties of these materials originate from the amino acid shell that can selectively bind the specific molecular or ion targets and biomolecules are provided. Focusing on the recognition and optical properties of these materials, this chapter summarizes the recent progress in using these materials as chiral separation, molecular and ion sensing. Finally, presence of amino acid shell on the surface of nanoparticles are demonstrated to provide enzyme like catalytic activities such as nanozymes and various kinds of nanozyme applications of these materials have been compiled and discussed their potential as suitable substitutes to the natural enzymes. This chapter compiles the applications of amino acid functionalized nanomaterials ranging from nanozyme, sensing, substrate specific binding to chiral separation and discussed in detail. To prove the fact that the inherent physicochemical properties of these nanomaterials make them as analogues of natural enzymes, also endow them with unparalleled advantages and extensive prospects in environmental science and engineering. Keywords Amino acids · Functionalized nanoparticles · Synthetic nanozymes · Target specific binding · Sensing · Catalytic applications

Abbreviations CD C-dots CdS CdTe CeO2 nanoparticles CuO nanoparticles DOPA Fe3O4 nanoparticles FTIR H2O2 HRP ITC MoS2 NIR NMR PVA SEM SERS SPR TEM TEOS TiO2 nanoparticles TMB

Circular dichroism Carbon dots Cadmium sulfide Cadmium telluride Cerium dioxide nanoparticles Copper oxide nanoparticles 3,4-dihydroxy-phenylalanine Iron oxide nanoparticles Fourier-transform infrared spectroscopy Hydrogen peroxide Horseradish peroxidase Isothermal titration calorimetric Molybdenum disulphide Near-infrared Nuclear magnetic resonance Poly vinylalcohol Scanning electron microscope Surface enhanced Raman scattering Surface plasmon resonance Transmission electron microscopy Tetraethylorthosilicate Titanium dioxide nanoparticles 3,30 ,5,50 -Tetramethylbenzidine

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

UV ZnO ZnS

1.1

3

Ultra-violet Zinc oxide Zinc sulfide

Introduction

Size, shape, composition and morphology dependant optical, electronic, magnetic, structural and redox properties of inorganic nanoparticles (including metals, metal oxides and clays) makes them unique building blocks, which can be self-assembled into super structures and devices that has been applied for catalysis, energy storage, sensors and biomedical devices (El-Sayed 2001; Parak et al. 2003; Daniel and Astruc 2004). These nanoparticles have very high surface to volume ratio, that drives the self-assembly of organic molecules on the vacant surface sites of these nanoparticles, which are generally referred as monolayer protected nanoparticles or clusters (Templeton et al. 2000). The role of these organic molecules is very important in interfacing these nanomaterials to any of the afore-mentioned applications because the nature of these molecules and their interaction with the nanoparticle surface provides an understanding, how the nanoparticle surface needs to be engineered for the specific application (Kango et al. 2013; Yin and Talapin 2013). Addition of these molecules during the synthesis of nanoparticles have two main objectives, apart from the final application. Firstly, addition of these molecules to the nanoparticles in their growth phase control the size of the nanoparticles and direct the shape of the nanoparticles by selective binding to certain crystalline phases (Thomas and Kamat 2003). Secondly, these molecules function as the new modified surface of these monolayer protected nanoparticles, irrespective of the nanoparticles chemical composition (Shenhar and Rotello 2003; Thomas and Kamat 2003). The monolayer of molecules bound to the nanoparticles surface provide the surface chemical functional groups that are responsible for hydrophobicity/hydrophilicity, adsorption behavior on surfaces, self-assembly and other kinetic phenomenon (Templeton et al. 2000; Sastry et al. 2002). Overall, these molecules control the stability of the nanoparticles, their self-assembly into large super structures, their binding with other molecules/ions, their collective interaction of nanoparticles eventually and their application. Therefore, the nature of these molecules and their interaction with the nanoparticles, play a vital role in designing nanomaterials for specific applications. Initially, long chain alkane thiols and carboxylic acids were used to functionalize metal and metal oxide nanoparticles, respectively. These nanoparticles were strongly hydrophobic and less reactive due to the long hydrocarbon surface because functionalization of these hydrocarbon chains is synthetically demanding. Subsequently, terminally functionalized thiol containing molecules were used, so that the terminal group was available for further reactivity and self-assembly. The main challenge here is to synthesise these bi-functional molecules, which usually multi-step chemical reactions. Moreover, the terminal

4

S. Periasamy et al.

functional group in these bi-functional molecules was either amine or carboxylic acid group. These molecules were known to enhance the polarity of nanoparticles, but these nanoparticles were not stable in different solvents and different pH. Immobilizing biomolecules on the surface of these nanoparticles were shown as less efficient due to the other competing interactions between the nanoparticles itself for further functionalization (Sastry et al. 2002, 2005). Biological macromolecules such as lipids, proteins and sugars have been used to functionalize the nanoparticles, but non-specific interactions may lead the aggregation of nanoparticles. Therefore, Sastry et al. have introduced amine containing surfactants to functionalize nanoparticles, wherein they demonstrated that amine groups interact with the nanoparticles electrostatically and provided scope Again, these surfactant functionalized nanoparticles were hydrophobic in nature due to the presence of hydrocarbon chains on the surface, which restricts the usage of these materials for biological applications. Sastry et al. developed new synthetic procedures using amino acids like tryptophan, tyrosine, aspartic acid and lysine to functionalize these nanoparticles (Mandal et al. 2002, Selvakannan et al. 2003, 2004a, b), to improve the nanoparticles dispersion in polar solvents. Moreover, the presence of amino acid shell provides the nanoparticles surface polar and water dispersible, more importantly “protein or enzyme-like” nanozyme renders these particles biocompatible. In particular, the surface functionalization of nanoparticles in biological applications is very much critical. In this context, using amino acids to functionalize nanomaterials is considered as a potential way of interfacing these nanoparticles for biological applications. Paolo Scrimin’s et al. also started using proteins and later amino acids to functionalize metal nanoparticles and using them as ‘nanozymes’, term that refers to the catalytic role provided by the cooperativity interaction between the nanoparticles and amino acids (Pasquato et al. 2004, 2005; Guarise et al. 2008; Chen et al. 2016). The main advantage of functionalizing metal nanoparticles with amino acids has led to the development of hybrid bionanomaterials that synergistically incorporate the electronic and optical properties of the former and the recognition and catalytic properties of the later. Amino acids functional groups, their chirality, optical properties combined with nanoparticles properties have led to numerous biotechnological applications such as affinity separations, biosensing, bioreactors, and the construction of biofuel cells. As shown in Fig. 1.1, electrostatic interactions between the nanoparticles and amino acids control their self-assembly, their ability to bind of biomolecules to nanoparticles, amphoteric nature and pH dependent charge variation makes these amino acids as the best candidates for surface modification of nanoparticles and thus making useful bio-conjugates (Chakraborty et al. 2018). The conjugation between the nanoparticles and biomolecules brought about due to their similar dimensions helps in tailoring the nanoparticle surface in a variety of ways thereby creating surface specific receptors to bind different molecules (Scrimin and Prins 2011). In general, biomolecules possess very high specificities in binding to the counter molecules due to their molecular recognition properties. The utilization of the surface chemistry of metal nanoparticles to anchor biomolecules provides a general route for the development of biosensors for

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

5

Fig. 1.1 Amino acids functionalized inorganic nanoparticles and their characteristic physiochemical properties

analytical applications with enhanced sensitivities and detection limits (Scrimin and Prins 2011).

1.1.1

Functionalization of Nanomaterials Using Amino Acids

Biological macromolecules including peptides, proteins, enzymes and nucleic acids have been demonstrated to functionalize pre-formed nanoparticles (postfunctionalization) or can help in converting the metal ion precursors into their metal or metal oxide nanoparticles (direct functionalization) and protect the nanoparticles as-formed. The macro-molecular nature of these biomolecules can sterically protect the nanoparticles from aggregation, while electrostatic interactions between the functional groups of these molecules and the surface bound metal ions, stabilize the nanoparticles from aggregation. Due to the small size, amino acids can functionalize and stabilize the nanoparticles mainly through electrostatic

6

S. Periasamy et al.

Fig. 1.2 Chemical structure of various kinds of amino acids and range of nanomaterials that can be produced or functionalised with amino acids. The functional chemical groups of the amino acid side chain are also shown

interactions. The various functional groups, variation of isoelectric point between 3–10 and structural conformations of amino acids, provide very good control to selectively bind the precursors for the size/shape-controlled synthesis of nanoparticles. Amino acids can be used to functionalize the preformed nanoparticles (postfunctionalization) (Selvakannan et al. 2003), through their amine, carboxylic and other side groups. These amino acids can be used during the synthesis of nanoparticles (direct functionalization) (Mandal et al. 2002; Selvakannan et al. 2004a, b), wherein all these functional groups can help in reduction of metal ion precursors or hydrolyse the precursors. In cases of layered materials, these amino acids occupy the interlayer positions, by exchanging with similar charge interlayer ions. As shown in Fig. 1.2, amino acids are zwitterionic and having amine, carboxylic and other functional groups, therefore, these molecules can interact with different kinds of metal, metal oxide and clay nanoparticles. The isoelectric points of these amino acids vary between 3 to 10.5, as illustrated in Fig. 1.2, therefore they can electrostatically bind with the oppositely surface charged nanoparticles. Moreover, presence of additional carboxylic, amine, phenolic, hydroxyl and thiol groups in

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

7

these amino acids provide a choice to selectively bind to these nanoparticles of specific composition. Moreover, presence of aromatic and imidazole groups can enhance the self-assembly of these nanoparticles through pi-pi stacking. Except glycine, all these amino acids are chiral, therefore, due to the presence of these molecules and lack of structural orientation, they exhibit chiral optical properties as well as chirality to the surface. Tryptophan exhibit fluorescence, which is usually used as marker for proteins, therefore their inherent optical properties could provide another handle to tune their optical properties. More importantly these molecules provide functional groups, which can selectively recognize the specific metal ions or molecules, which can be useful in target specific binding of ions and molecules. At the same time, this binding can cause the change in the electronic and optical properties of the nanoparticles, which can be used in chemical and biological sensing. Amino acids functionalized nanoparticles have enzyme-like surface, therefore presence of amino acids in a structurally locked condition can provide the catalytic surface. In combination with catalytically active nanoparticles, these cooperative systems tend to have interesting optical, sensing, catalytic and target specific binding applications. pH dependant charge variation of these amino acids led to the high surface charge density, which was the main reason for the high zeta potential of these nanoparticles and their stability (Sastry et al. 2005). Many biological applications, rapid adsorption of serum proteins and other antibodies on the surface of nanoparticles causes aggregation and amino acids functionalized nanoparticles can overcome the adsorption of proteins induced aggregation. Thus, the presence of amino acids shell on the surface of nanoparticles can enhance the circulation time within the biological fluids. Therefore, amino acids functionalization of nanoparticles provides multiple ways of modifying the surface for any tailor-made application.

1.2

Synthesis of Amino Acids Functionalized Nanoparticles

Wet chemical methods are the commonly used procedure for the synthesis of amino acids functionalized nanoparticles. Amino acids can be added during the formation of nanoparticles (direct functionalization), wherein the role of amino acid involves in mediating the nanoparticles formation from their precursors as well as control the size and shape of the nanoparticles by binding to the nanoparticles surface. Amino acids can be added to the pre-formed nanoparticles (post functionalization), wherein amino acids can replace the surface bound ions/molecules and bind to the nanoparticles surface. All the amino acids can be used for this purpose, however the chemical composition of nanoparticles and its interaction with the specific amino acid dictates the choice of amino acid and the synthesis methods.

8

1.2.1

S. Periasamy et al.

Amino Acids Mediated Synthesis of Nanoparticles

Amino acids mediated synthesis of nanoparticles is a direct way of functionalizing the nanoparticles during their synthesis itself. Metal nanoparticles are usually prepared by reduction of their metal ions using a chemical reducing agents in the presence of surfactants, polymers, or other biomolecules. Trisodium citrate, sodium borohydride, hydrazine, and phosphine are the common chemical reducing agents and presence of these reducing agents or their by-products tend to co-exist with the nanoparticles surface and they contaminate the surface (Daniel and Astruc 2004). Therefore, using amino acids as reducing and functionalizing molecules could be an environmentally benign and green approach of making metal nanoparticles. Selvakannan et al. and Daima et al. have used amino acids tyrosine, tryptophan and aspartic acid for this purpose and demonstrated the formation of stable gold, silver nanoparticles, core-shell and alloy nanoparticles (Mandal et al. 2002; Selvakannan et al. 2003, 2004a, b; Daima et al. 2013, 2014) (Fig. 1.3a).

Fig. 1.3 (a) Tryptophan and tyrosine mediated reduction of gold and silver ions to form their nanoparticles and representation of respective amino acid on the surface of gold, and silver nanoparticles (Daima et al. 2013, 2014; Selvakannan et al. 2013b) (b) Lysine mediated synthesis of star shaped anisotropic particles and the vials containing nanoparticles; Reprinted with permission from (Plascencia-Villa et al. 2015) Copyright (2015) American Chemical Society (c) Histidine functionalized Au10 clusters (Yang et al. 2011) Copyright 2011, Royal Society of Chemistry (d) Amino acids functionalized silica spheres; (e) D and L forms of phenylalanine functionalized CeO2 nanoparticles synthesis (f) Amino acids functionalised CuO nanoparticle (El-Trass et al. 2012) Copyright 2012, Elsevier (g) Arginine amino acids functionalized anisotropic titanium dioxide (TiO2) nanoparticles synthesis (Wang et al. 2014) Copyright 2014, Royal Society of Chemistry (h) Amino acid functionalized C-dots (Sarkar et al. 2015) Copyright 2015, Royal Society of Chemistry (i) Scheme for amino acids intercalation into hydrotalcites (Vaz and Nunes 2010) Copyright 2010, Royal Society of Chemistry

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

9

Amino acids like aspartic acid, lysine, tryptophan, and tyrosine have additional functional groups along with the amine and carboxyl groups, thus provides an alternative route to synthesize nanoparticles with functionalized surfaces. All these nanoparticles were found to be highly stable even after complete evaporation of water and can be readily redispersed in water. This clearly demonstrates the amino acid functionalization can help in stabilizing the particles even in the absence of water. Amino acid lysine was shown to direct the nanoparticles growth on preformed gold seeds to synthesize anisotropic gold nanoparticles (Plascencia-Villa et al. 2015). The amount of seeds and lysine controls the anisotropic growth of the nanoparticles (Fig. 1.3b). Histidine amino acid was shown to produce few atom Au clusters (Yang et al. 2011), which exhibit interesting fluorescent properties (Fig. 1.3c). This simple procedure involves addition of histidine to chloroaurate ions which led to the formation of water-soluble, monodisperse, and bluish green emitting Au10 nanoclusters. Amino acid histidine reduces the gold ions and protect the as-formed gold nanoclusters.

1.2.2

Post-functionalization of Nanoparticles Using Amino Acids

Amino acids lysine, phenyl alanine, and cysteine do not have the ability to reduce metal ions, therefore these amino acids were used to functionalize the pre-formed metal nanoparticles. Addition of amino acids to pre-formed nanoparticles that were functionalized by citrate ions led to the substitution of those ions by amino acids, resulted in the formation of amino acid functionalized nanoparticles. Thiol functional group of cysteine and amine group of lysine along with carboxylic acid group of these amino acids generally bind to the nanoparticles surface(Selvakannan et al. 2004b; Zhu et al. 2012; Ma et al. 2020). Semiconductor, metal oxide and silica nanoparticles synthesis: Few amino acids (lysine, arginine, histidine) have more than one amine functional group, which are usually referred as cationic or basic amino acids. At physiological pH, all these amino acids can be easily protonated and attain the positive charge. Silica nanoparticles are usually prepared by the base mediated hydrolysis of silica precursors including tetraethylorthosilicate (TEOS) or sodium metasilicate. Cationic amino acids tend to promote silica hydrolysis, which resulted in the formation of amino acid functionalized silica nanoparticles. Removal of amino acid lead to the formation of mesoporous silica (Selvakannan et al. 2013a) and it was observed in few cases that the resultant silica retain the chirality left by the amino acid (Lacasta et al. 2011). Arginine amino acid was used to hydrolyse the tetraethylorthosilicate and this reaction led to the formation of uniform sized silica nanoparticles functionalized with amino acids (Wang et al. 2010) (Fig. 1.3d). Similarly, post chemical functionalization (amidation approach) of poly (acrylic acid) functionalized cerium dioxide (CeO2) nanoparticles led to the formation of D- and

10

S. Periasamy et al.

L- phenylalanine functionalized ceria nanoparticles, as illustrated in Fig. 1.3e. Fourier-transform infrared spectroscopy (FTIR) analysis of the resultant materials showed the presence of these amino acids on the surface of ceria nanoparticles (Sun et al. 2017) and their binding with ceria surface. Similarly, copper oxide nanoparticles were also made by the arginine amino acid mediated hydrolysis of its precursor. Electrostatic interaction between the amino acid arginine and the as-formed copper oxide (CuO) nanoparticles stabilise the nanoparticles (El-Trass et al. 2012) (Fig. 1.3f). Most of the semiconductor nanoparticles or quantum dots synthesis procedures use organic solvents for their synthesis because polar solvents tend to quench the nanoparticles fluorescence. Moreover, these hydrophobic nanoparticles were difficult to be dispersed in polar solvents, therefore it restricts their applications in biological imaging (Jaiswal and Simon 2004). Amino acids functionalization is known to improve the semiconductor nanoparticles and quantum dots dispersion in polar solvents without quenching the fluorescence. Amino acids have multiple functional groups, which can selectively bind certain metal ions and subsequent hydrolysis, or reduction of these metal ions led to the formation of semi-conductor nanoparticles. Cadmium sulfide (CdS), zinc sulfide (ZnS, Li et al. 2004), titanium dioxide (TiO2), zinc oxide (ZnO) are the commonly used semiconductor nanoparticles, which are usually prepared from their precursor in the presence of amino acids. Titanium dioxide nanoparticles were prepared by amino acid mediated hydrolysis of titanium isopropoxide (Fig. 1.3g) and the resultant nanoparticles were found to be anisotropic. Due to the strong interaction between amino acids and metal ions, these amino acids can control the kinetics of nanoparticles formation and the size of the nanoparticles. Histidine amino acid is known to chelate zinc and cadmium ions therefore, histidine stabilized zinc sulfide and cadmium sulfide (Yadav et al. 2010) nanoparticles were synthesised with uniform size and these nanoparticles were found to be highly fluorescent. Chelation of these metal ions form a stable complex and nanoparticles formation form this complex precursor was the main mechanism that these nanoparticles were stable against agglomeration. Functionalization of layered materials by intercalation: Layered materials such as clays can be functionalized using amino acids by rehydrating the oxides obtained after calcination of clays at high temperatures (< 500  C). These oxide materials can be rehydrated under alkaline medium to restore the layered structure and this approach is the commonly used method to obtain functionalized clay materials. Amino acids intercalation of layered hydrotalcites were achieved by rehydrating the calcined hydrotalcites in the presence of amino acids (Fig. 1.3h). Amino acids such as phenylalanine and tryptophan were intercalated within the interlayer and these amino acid functionalized nanomaterials can be used as host for metal ions (Vaz and Nunes 2010). Apart from these inorganic nanomaterials, amino acids have been used to functionalize layered graphene materials and carbon dots (C-dots). Carbon dots are another class of semiconductor nanoparticles, which were prepared from citrate precursor and subsequent functionalization with amino acids led to formation of

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

11

amino acids functionalized fluorescent carbon dots (Sarkar et al. 2015), as shown in Fig. 1.3i.

1.3

Optical Properties of Amino Acid Functionalized Nanoparticles

Metal (Jain et al. 2008; Xiao and Yeung 2014) and semiconductor nanoparticles (Green 2004; Jaiswal and Simon 2004) have been used in biological imaging including the optical and fluorescent imaging, as immunoprobes and Surface Enhanced Raman Scattering (SERS) substrates (Zhang et al. 2011). Due to the tuneable and superior optical properties of these materials in wide spectral range, if compared to the organic dyes, makes them more efficient in their use as optical and fluorescent probes. The combination of unique optical properties with the size of biological macromolecules, these nanoparticles are considered as promising candidates for the label free biological imaging. Amino acids are chiral and lightresponsive; thus, the amino acids functionalized nanomaterials provide an efficient approach to make functional nanomaterials, which can be made photo-responsive. For applications of such materials in biological imaging and targeting biological molecules, it is very important to understand the optical properties of the amino acid functionalized nanoparticles. Tailoring the optical properties of metal and semiconductor nanoparticles by organized packing of amino acid chromophores offers exciting opportunities to the design of materials with novel electrical, optical, and photophysical properties.

1.3.1

Optical Properties of Metal Nanoparticles – Surface Plasmon Resonant Absorption

Metal nanoparticles have interesting optical and electronic properties, which can be modified by the organized assembly of amino acids present on the surface. Metal nanoparticles exhibit intense optical absorptions in the visible and near-infrared (NIR) spectral region of electromagnetic spectrum, called surface plasmon resonance (SPR) absorption. The size, shape, chemical composition, dispersed media and their aggregation are the major factors that control the position of surface plasmon resonance absorption from visible to near-infrared region (El-Sayed 2001). Surface plasmon resonant absorption of these metal nanoparticles have higher extinction coefficients (ε > 108 M1 cm1) than the absorption cross-section of those organic dyes currently used for imaging. This strong absorption in the visible region arises when the collective surface plasmon frequency of the electrons in the metal nanoparticles is in-resonant with the frequency of the incident electromagnetic radiation. The position and the width of this surface plasmon resonant absorption

12

S. Periasamy et al.

band are highly sensitive to the surroundings and thus surface modification of nanoparticles with any functionalizing molecule and changes in the dispersion media leads to observable colour changes. Few amino acids have strong chemical interaction with the metal nanoparticles surface, which have some charge transfer interactions, therefore, the resulting optical properties are different from the commonly prepared metal nanoparticles (Selvakannan et al. 2003, 2004a, b, 2013b). In the previous section, it has been discussed that the amino acids were used to reduce the gold and silver ions to form gold and silver nanoparticles as well as some amino acids are shown to functionalize the preformed metal nanoparticles. The interesting aspect is when the composition of the nanoparticles was the same, the presence of different amino acids on the surface led to the change in its surface plasmon resonant absorption maxima. This is partly because of the amino acids’ specific interaction with nanoparticles, size as well as the aggregation of nanoparticles. Daima et al. has developed amino acid mediated synthesis of gold, silver and their bimetallic nanoparticles (Daima et al. 2013, 2014). The surface plasmon resonant absorption of silver nanoparticles gradually shifted in the case of bimetallic nanoparticles and the shift was found to be correlated to the relative composition of silver versus gold in the nanoparticle’s composition. Again, for the same composition of bimetallic nanoparticles but with different amino acids shell, the surface plasmon resonant absorption maxima were found to be different (Fig. 1.4a). These results clearly indicate that optical properties of metal nanoparticles strongly depend on the nature of amino acids present on the surface of the nanoparticles and the chemical composition of the nanoparticles. Knecht and his co-workers studied the changes in the surface plasmon resonant absorption by partially introducing the different amino acids on the pre-formed gold nanoparticles (Sethi et al. 2011). Cysteine, arginine, histidine, and alanine were the four amino acids used for the study. To citrate functionalized gold nanoparticles, addition of these four amino acids partially replace the citrate ions from the surface and the selfassembly process was controlled by the extent of ligand substitution and their strength of binding. To validate this concept, surface plasmon resonance study was carried out on a plain gold surface, by passing citrate, alanine, histidine, arginine, and cysteine consecutively and estimate the sensor response. Except cysteine, all the other amino acids binding to the gold surface was reversible, that shows the strong binding of cysteine with the gold surface. Dissociation time of the bound amino acids from the gold surface was calculated, where arginine and histidine dissociation time from the surface was higher as compared to citrate and alanine. Overall, this study concluded that amino acids binding to the nanoparticles strongly depends on the side functional groups of amino acid and their interaction with the specific nanoparticle’s composition. This eventually controls the aggregation and the optical properties of the nanoparticles (Fig. 1.4b). Anisotropic nanoparticles exhibit longitudinal and transverse plasmon resonances as compared to the only one surface plasmon resonant absorption observed in the case of spherical gold nanoparticles. Presence of amino acids during the synthesis of gold nanoparticles, direct the growth of anisotropic structures through its interactions

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

13

Fig. 1.4 (a) UV-visible spectra of gold and silver nanoparticles and their bimetallic nanoparticles of different composition showing changes in surface plasmon resonance with respect to composition (Daima 2013); (b) Surface Plasmon resonant spectra of different amino acids interaction with gold surface and their kinetics (Sethi et al. 2011) Copyright 2011, Royal Society of Chemistry; (c) UV-visible spectra of lysine functionalized star shaped gold nanoparticles along with their scanning electron microscope (SEM) image (Plascencia-Villa et al. 2015) Copyright 2015, American Chemical Society; (d) Fluorescence emission spectra of tryptophan functionalized anisotropic gold nanoparticles and white light emission (Kasture et al. 2010) Copyright 2010, Elsevier; (e) Fluorescence spectra of amino acid functionalized copper oxide nanoparticles and their lifetime measurements (El-Trass et al. 2012) Copyright 2012, Elsevier; (f) Fluorescence spectra of histidine functionalized cadmium sulfide nanoparticles (Yadav et al. 2010) Copyright 2010 Elsevier; (g) UV-visible, transmission electron microscopy (TEM) images of cysteine functionalized gold nanorods and their chiro-optical properties (Zhu et al. 2012) Copyright 2012, American Chemical Society; (h) Cysteine modified cadmium telluride (CdTe) quantum dots, their electronic level modification and their chiro-optical properties (Li et al. 2020) Copyright 2020, American Chemical Society

with the metal ions. Recently, Plascencia-Villa and his co-workers have used lysine amino acids involvement during the synthesis of star shaped anisotropic nanoparticles. By controlling the synthesis procedure, the surface plasmon resonant absorption of these nanoparticles can be tuned from visible to near-infrared radiation (Plascencia-Villa et al. 2015).

1.3.2

Optical Properties of Semiconductor Nanoparticles – Fluorescence Properties

Fluorescence properties: Semiconductor nanoparticles exhibit fluorescent property both in the UV and visible region and again the size, shape, chemical composition,

14

S. Periasamy et al.

and their aggregation can control the fluorescence emission and its quenching (Trindade et al. 2001). Since fluorescent phenomenon of semi-conductor nanoparticles are highly sensitive, these nanoparticles are used in biological imaging significantly (Green 2004). Fluorescent nanoparticles are being considered as potential alternatives to the dyes generally used for bio-labelling and as solid-state emitters. As compared to the organic dyes, these nanoparticles have tuneable emission and narrow width, essential attributes for any kind of bio-imaging applications. However, these nanoparticles were found to be toxic and have poor solubility in water (Jaiswal and Simon 2004), these nanoparticles surface modification using amino acids can improve their biocompatibility and solubility in water without compromising its fluorescent behaviour. Surface bound amino acid, upon binding with any other metal ion or biomolecule can enhance or quench the fluorescence, therefore this study of substrate specific binding, can be reflected as changes in their fluorescent emission (Wei and Wang 2013; Williams et al. 2014; Liu et al. 2020). Presence of amino acids on the surface of such nanoparticles exhibit unusual surface enhanced fluorescence phenomena. Tryptophan amino acid exhibit fluorescence in the UV region and these fluorescent properties were found to be modified in the presence of nanoparticles. Prasad and his co-workers have shown tryptophan functionalized anisotropic gold nanoparticles (Fig. 1.4d) exhibiting strong white light emission (Kasture et al. 2010). Another report demonstrated that tryptophan functionalized gold nanoparticles were used for deep ultra-violet imaging and the multilayers of tryptophan on the surface of nanoparticles were found to be responsible for the deep ultra-violet emission (Pajovic et al. 2015). In general, presence of metal nanoparticles usually quenches the fluorescence, but here the fluorescence property of tryptophan amino acid enhanced upon the presence of anisotropic gold nanoparticles. Tapan Ganguly and his co-workers studied the fluorescence of amino acid tryptophan, when it was bound to the zinc oxide semiconductor nanoparticles surface (Mandal et al. 2009). Tryptophan fluorescence was quenched when it binds with the zinc oxide nanoparticles through electrostatic interactions. This was probably due to the complex formation between tryptophan and zinc oxide nanoparticles and its presence was demonstrated by using steady-state and timeresolved spectroscopic studies. El-Kemary and his co-workers have synthesized copper oxide nanoparticles, which were functionalized with a cationic (arginine) and anionic amino acid (aspartic acid), respectively (El-Trass et al. 2012). Arginine amino acid was found to electrostatically bind with the nanoparticles surface, while aspartic acid did not bind due to the similar charge of the nanoparticles (Fig. 1.4e). In contrast, Yadav et al. used amino acid histidine to functionalize the cadmium sulfide semiconductor nanoparticles (Fig. 1.4f) during their formation by sonochemical process (Yadav et al. 2010). Histidine amino acid have strong affinity to bind cadmium ions, therefore its presence controls the size of nanoparticles. These histidine functionalized cadmium sulfide nanoparticles were found to have strong fluorescence due to the confinement effect. Carbon dots functionalized with amino acids were demonstrated to exhibit strong fluorescence emitting in the visible region and have used for biological imaging (Sarkar et al. 2015). Muley and his co-workers

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

15

have used L-alanine and L-arginine amino acids to functionalize the cadmium sulfide nanoparticles. An interesting observation from this study is that as the concentration of alanine increased, there was an increase in the band gap of cadmium sulfide nanoparticles. Also, dispersion of the alanine functionalized nanoparticles into poly vinylalcohol (PVA) thin films exhibit non-linear absorption by two-photon absorption processes (Talwatkar et al. 2014). Stereo-isomers of amino acids also found to have significant effect in the optical properties of nanoparticles. L and D forms of cysteine amino acid were used to functionalize cadmium telluride nanoparticles and in both cases thiol groups of both isomers bind to the nanoparticles surface, however, their optical properties were found to be different (Gao et al. 2018).

1.3.3

Chiro-optical Properties of Amino Acids Functionalized Semiconductor Nanoparticles

Except glycine, all the amino acids are chiral, therefore all these chiral amino acids can be able rotate the polarized light. As a result of the unique combination of amino acids chirality with the optical properties of nanoparticles, these nanoparticles exhibit new kind of chiroptical properties. The resultant chiro-optical nano systems can extend the scope of current optically active components used in optical devices. Chiral molecules including amino acids exhibit different absorption to right and lefthanded components of circularly polarized light, which is usually measured by circular dichroism (CD) technique. Many of these chiral molecules exhibit strong circular dichroism absorption in the UV range, while inorganic nanoparticles exhibit strong absorption and emission in the visible region of the spectrum. Selforganization of the chiral amino acids on the surface of nanoparticles render the nanomaterial surface chiral and the surface plasmon resonance absorption or fluorescence emission of nanomaterials can shift the circular dichroism absorption in the visible region. By controlling the optical activity and chirality in the Visible-NearInfrared region, applications of these amino acid functionalized nanoparticles can be realized in developing optical devices, chiral catalysts and enantiospecific separation. Zhiyong Tang and his co-workers have developed this concept by selfassembling gold nanorods using cysteine amino acid and this linear super structures exhibit interesting optical properties (Zhu et al. 2012). Gold nanorods exhibit transverse and longitudinal surface plasmon resonance, aspect ratio of the gold nanorods direct the position of longitudinal surface plasmon resonance. Binding of cysteine led to the observation circular dichroism response in the Near-InfrarRed and the Ultra-Violet spectral region (Fig. 1.4g). Therefore, manipulation of circular dichroism response of cysteine can be brought into visible region and aspect ratio can tune this Circular Dichroism response from visible to near-infrared region. Similar phenomenon was also observed in the case of cysteine capped cadmium telluride nanoparticles (Fig. 1.4h) wherein cysteine binding to the cadmium telluride

16

S. Periasamy et al.

surface shifted the fluorescence emission and circular dichroism absorption (Li et al. 2020).

1.4

Thermodynamics of Amino Acids Binding on Nanoparticles Surface

In the previous sections, it was demonstrated that how amino acid functionalized nanoparticles can be synthesized through different chemical methods. These nanoparticles were found to be stable even after complete evaporation of water. To utilize these nanoparticles for specific applications, require a deeper understanding of the nanoparticle-amino acids interactions. These interactions are strongly dependant on the nanoparticle’s composition, amino acids functional groups and the solvent, therefore specific interactions between the nanoparticles and amino acids will usually vary. In addition, multiple interactions between the nanoparticles and amino acids such as hydrogen bonding, electrostatic interaction, hydrophobic pi-pi interactions, and acid-base interactions add to their complexity (Sastry et al. 2002). Importantly, the thermodynamic aspects of nanoparticle-amino acid interactions clearly play a vital role in controlling the interactions. Physical parameters such as pH, temperature, ionic strength, and other physicochemical interactions are the major parameters that control the thermodynamics of binding of an amino acid on a nanoparticle surface. As amino acids have multiple functional groups, these molecules tend to undergo competitive adsorption on the nanoparticles surface, which is usually controlled by the pH of the medium and the nanoparticles. Therefore, it is very important to estimate the strength and nature of these amino acidnanoparticles interaction experimentally to construct, how the afore-mentioned parameters influence the binding interaction. Isothermal titration calorimetry is an experimental technique that measures the binding interactions by measuring the heat of the reaction. This technique has been used to study various biomolecular interactions such as protein-protein interactions, protein-DNA interactions, protein-lipid interactions, protein-metal ion interactions, and drug-enzyme interactions (Ladbury and Chowdhry 1996). Sastry and his co-workers have used Isothermal titration calorimetric technique to study the interaction between the nanoparticles and the amino acids (Joshi et al. 2004). To the aqueous dispersion of gold nanoparticles, two kinds of amino acids were added, and their heats of interaction were calculated as a function of pH. Appearance of exothermic peaks upon the addition of amino acids clearly indicated the strong interaction between the gold nanoparticles and the amino acids. Aspartic acid (acidic) and lysine (basic) amino acids were used for this purpose and heats of interaction were calculated at physiological and alkaline pH. As the vacant sites progressively got occupied, the exotherm interactions became smaller and smaller that eventually saturated. At neutral pH, it was observed that aspartic acid binds strongly to the gold nanoparticles, while at alkaline pH,

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

17

Fig. 1.5 (a) Isothermal titration calorimetric studies of amino acids binding to gold nanoparticles at different pH (Joshi et al. 2004) Copyright 2004, American Chemical Society; (b) NMR spectral studies on amino acid lysine binding to gold nanoparticles at different pH and their Transmission Electron Microscopic images (Selvakannan et al. 2003) Copyright 2003, American Chemical Society; (c) Protein binding to the amino acids functionalized nanoparticles and their isothermal titration calorimetric studies (De et al. 2007). Copyright 2007, American Chemical Society

lysine binds strongly. These studies indicated that amine groups are responsible for the binding and protonated stage when it binds electrostatically to the negatively charged gold nanoparticles. In contrast, unprotonated amine group interact with the gold ions through its lone pair of electrons present in the amine group (Fig. 1.5a). As mentioned earlier, nanoparticles interaction with amino acids depends upon the nature of amino acid and the working pH of the medium. As amino acids have different kinds of functional group, their interaction with nanoparticles of varying composition are different. Therefore, it is important to identify the nature of interaction between amino acids and the nanoparticles that control the available terminal functional groups present on the surface of the nanoparticles. UV-Visible and nuclear magnetic resonance (NMR) spectroscopic analysis of lysine capped gold nanoparticles at different pH, provide a better understanding about these interactions (Selvakannan et al. 2003). Addition of lysine to gold nanoparticles, led to the broadening of surface plasmon resonant absorption band and red shifted. This was probably due to aggregation of nanoparticles, because of their surface modification by lysine amino acid (Fig. 1.5b). However, the lysine-capped gold colloidal solution was stable for months with little evidence of further aggregation. Proton nuclear magnetic resonance studies of pure lysine and after its capping with the gold nanoparticles was carried out to understand the chemical interaction between them. Both proton nuclear magnetic resonant spectra were found to be different and major changes were observed to the protons coordinated to the α-carbon of the

18

S. Periasamy et al.

amino acid and the carbon attached to the second amine group in the amino acid. From the nuclear magnetic resonance and isothermal titration calorimetric studies, it was concluded that amine group binds to the nanoparticles surface. The broadening of the terminal NH2 group peak is most likely due to formation of hydrogen bonds with surface bound lysine molecules of neighbouring gold nanoparticles. Hydrogen bond formation between the terminal amine groups with its neighbouring molecules were shown to be pH dependant. This result suggests that the binding of lysine to the gold nanoparticle surface occurs via the α-amine group in the amino acid while the terminal amine group forms hydrogen bonds with the carboxylic acid groups of surface-bound lysine molecules on neighbouring gold nanoparticles. This also agrees well with the observed broadening of the surface plasmon resonant band, as discussed in UV-visible absorption spectral studies of nanoparticles earlier. Isothermal titration calorimetric studies were followed to understand the silver nanoparticles and tyrosine amino acid and again it was proved that the pH of the medium dictates the binding of different groups to the silver nanoparticles. At neutral pH, carboxylic acid group binds to the silver nanoparticles, while at higher pH, phenol group binds with the silver nanoparticles (Selvakannan et al. 2004b). Sadler and co-workers have demonstrated that amino acid glycine form a coordination covalent bond with chloroaurate ions, the precursor for the gold nanoparticles (Zou et al. 1999). In general, chemical reduction of chloroaurate ions led to the formation of gold nanoparticles, which retain certain fraction of unreduced chloroaurate ions on its surface. Lysine molecules when added to the borohydride reduced gold nanoparticles, the unreduced chloroaurate ions bound to the nanoparticle surface bind with the lysine molecules, like the mechanism proposed by Sadler and co-workers. Rotello and his co-workers have also used isothermal titration calorimetric technique to study the amino acid functionalized nanoparticles with the α-chymotrypsin protein (Bayraktar et al. 2007; De et al. 2007; You et al. 2008). Thermodynamic aspects of the nanoparticle binding interaction with the protein was found to be dependent on the hydrophobic pockets of the protein and the amino acids used for the functionalization. Another recent work have studied the interaction of various amino acids binding with mesoporous silica (Gao et al. 2016), and they observed that electrostatic interaction was found to be the main driving force for the binding of amino acid to the silica surface. Another study demonstrated that the nature of amino acid controls its adsorption on the silica surface. As the silica surface is hydrophilic, the study demonstrated that the adsorption of glutamic acid and arginine were found to be dependent on the surface charge of silica material and pH. In contrast, hydrophobic amino acid such as phenylalanine did not show such pH dependence but depends upon the hydrophobic nature of the silica material (Gao et al. 2008). Overall, pH, temperature, the nature of amino acids and nanoparticles composition controls the nature of interaction and binding, which was supported by the calorimetric measurements and other spectroscopic techniques.

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

1.5

19

Substrate Specific Binding – Electrostatic and Chiral

Applications of metal nanoparticles in bioimaging, therapeutics and diagnostics have become an active field of research. To render these nanoparticles surfaces with desirable functional properties, it is very important to tailor the nanoparticles surface to specifically bind with the target biomolecules and understand their interaction. Amino acids functionalized gold nanoparticles surfaces are considered as promising materials for modelling of protein surfaces. Therefore, these materials can bind with various biomacromolecules including DNA and proteins. Their sizes are similar to the biological macromolecules and presence of amino acids on the surface can specifically bind with specific proteins. Such specific recognition of proteins can enhance our understanding on protein-protein interactions, which form the basis of many cellular processes including modulation of enzyme activity, DNA transcription and cell adhesion. Self-assembly of amino acids on the surface of nanoparticles render the nanoparticles surface very similar to protein or enzyme surfaces because of the presence of multiple functional groups, able to interact with other biomolecules through their hydrogen bonds. Presence of amino acid shell on the surface of nanoparticles also exhibit molecular interactions like the phenomenon observed in protein-protein interactions. Another advantage of these amino acid functionalized nanoparticles enables their uptake and activity within the cells.

1.5.1

Protein and DNA Binding to Nanoparticles Surface

Vincent Rotello and his co-workers have used functionalized nanoparticles that are having terminal amino acid functional groups to investigate how the amino acid surface on the nanoparticles can function as a receptor for the protein binding (You et al. 2005a, b, 2006, 2008). α-Chymotrypsin protein was chosen as the target protein and a series of amino acid functionalised nanoparticles were studied for their interaction with α-Chymotrypsin. Amino acids having hydrophobic components (leucine and valine), additional carboxylate anions (aspartic and glutamic acids) and the hydrogen bonding functionality (glycine and asparagine) were used for this study. Nanoparticles-protein binding were studied using gel electrophoresis, circular dichroism, and enzyme inhibition assays. Electrostatic interaction between the nanoparticles surface and the protein was shown to be driving force for the binding interaction, therefore the surface charge density of the amino acids plays a key role. Also, the presence of hydrophobic and hydrophilic groups of amino acids were found to affect the secondary structure. The same group extended the similar approach to develop a nanoparticles platform that can be shown as effective DNA receptors (Fig. 1.6a). The electrostatic interaction controls the binding interaction between the various amino acid functionalized nanoparticles and α-Chymotrypsin protein, which is essentially the charge complementarity between the multiple functional groups

20

S. Periasamy et al.

Fig. 1.6 (a) Schematic representation of binding between amino acid functionalized nanoparticles and DNA (Ghosh et al. 2008) Copyright 2008, American Chemical Society; change in Circular Dichroism spectra of DNA by nanoparticles (Ghosh et al. 2007) Copyright 2007, John Wiley and Sons; (b) Glutamic acid modified gold nanoparticles and its binding with the protein (Wangoo et al. 2008) Copyright 2008, Elsevier; (c) Optical rotation of pure (R)- and (S)-PO and in the presence of gold and cysteine functionalized gold nanoparticles (Shukla et al. 2010) Copyright 2010, American Chemical Society; (d) UV-Visible absorption spectra of L-cysteine functionalized nanoparticles, after their interaction with R-naproxen and S-naproxen: schematic representation of binding of R-naproxen with nanoparticles is also shown (Keshvari et al. 2015) Copyright 2015, Royal Society of Chemistry

between the amino acids on the nanoparticles surface and the α-Chymotrypsin protein. To develop a DNA receptor, surface of the nanoparticles needs to be positively charged as DNA is negatively charged. Lysine, cationic amino acid, when it is present on the surface of the nanoparticles, these nanoparticles can be considered to bind the DNA (Ghosh et al. 2008). These studies indicated that secondary structure of DNA was affected, when it binds with the nanoparticles surface because nanoparticles tend to electrostatically bind with the DNA and these compete with the hydrogen bonded interactions in the DNA and distort the secondary structure (Fig. 1.6a). The nature of terminal amino acid controls its binding and extent of distortion with DNA. Similarly, Wangoo et al. has synthesized glutamic acid mediated formation of gold nanoparticles and these nanoparticles were observed to have negative zeta potential due to the carboxylate ions (Wangoo et al. 2008). The protonated amine groups of protein tend to bind with these glutamic acid functionalized gold nanoparticles electrostatically. Fluorescence quenching and circular dichroism studies indicated conformational changes in the protein structure, upon binding with glutamic acid functionalized gold nanoparticles (Fig. 1.6b).

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

1.5.2

21

Enantioselective Binding and Chiral Separation

Amino acids are chiral in nature and they retain their chirality even after they bind with the nanoparticles surface. Thus, the organized assembly of amino acids on the surface of nanoparticles render these nanoparticles surface enantioselective. The fact that these chiral nanoparticles interact enantiospecifically with chiral adsorbates is a key step toward achieving enantiospecific catalysis, separations, and sensing. Nanoparticles are known to have very high surface-to-volume ratio, therefore equipping their surface with chiral amino acids, combines efficiency and separation of enantiomers or stereoisomers from a racemic mixture. This concept was studied and demonstrated by using amino acid functionalized nanoparticles in separating a racemic mixture (Shukla et al. 2010). D and L forms of cysteine amino acid were used to functionalize the gold nanoparticles. Their separation ability can be monitored by the optical rotation measurements (Fig. 1.6c). A racemic mixture containing (R)- and (S)-propylene oxide was allowed to interact with D and L-cysteine functionalized gold nanoparticles and the specific rotation of polarized light was a measure of chiral separation. These studies confirm the chiral separation ability of these nanoparticles by selectively adsorbing one enantiomer of propylene oxide and leaving the other enantiomer in the solution. Histidine functionalized gold nanoparticles have been shown as efficient in separating R- and S- naproxen from a racemic mixture (Keshvari et al. 2015). Simple colorimetric approach and UV-Visible spectral studies demonstrated the selective interaction of nanoparticles surface with only one stereoisomer (Fig. 1.6d).

1.6

Amino Acids Functionalized Nanoparticles in Sensing Applications

Developing analytical probes that can detect and sense rapidly any chemical or biochemicals, toxins, metal ions and gases with high level sensitivity is a current topic of interest today. Significant efforts have been made to solve the global health issues and other environmental concerns that world is facing today. The main desirable features of such sensor platforms include the portable analytical instrumentation, less sample preparation procedures, rapid analysis and easy to read results (Scrimin and Prins 2011; Song et al. 2019; Liu et al. 2020). Colorimetric sensor systems are the important candidates and can have all the afore-mentioned desirable features for the development of portable, rapid analytical platforms. Recent developments in visible light fluorescent probes and surface enhanced Raman scattering (SERS) substrates enable the estimation of analytes even if they are present in ultra-trace levels (Zhang et al. 2019). This was the main reason that colorimetric, fluorescent, and surface enhanced Raman scattering probes based chemical and biomolecular sensing received a great deal of attention today. The essential element for such efficient sensing platform must have a recognition and

22

S. Periasamy et al.

signalling component. Amino acid functionalized nanoparticles are the excellent choice as sensors as these materials have amino acids as a recognition component and the nanoparticles as a signalling component. From the available pool of twenty amino acids and the vast variety of inorganic nanoparticles, there are various kinds of sensor can be developed to sense wide variety of chemicals, biochemicals and toxic metal ions. Amino acids shell provides the nanoparticle surface “enzyme-like”, which were shown to exhibit highly specific molecular and ion recognition as well as their ability to recognize stereoisomers, as an important pre-requisite for developing substrate specific sensor platforms. Inorganic nanoparticles have interesting optical properties which exhibit instantaneous optical response upon binding with target substrate (Zhang et al. 2019). This rapid response combined with the option of quantitative analysis enable these nanoparticle-based sensors a viable alternative to other expensive techniques such as radioisotope labelling and clinical assays. In the following sections, the efficacy of colorimetric and fluorescent based sensing capability of amino acid functionalized nanoparticles will be discussed in detail.

1.6.1

Colorimetric Sensing

Surface plasmon resonant absorptions of gold, silver and copper nanoparticles in the visible and near-infrared region are highly sensitive to their surface and any changes on the surface can show measurable changes in their surface plasmon resonant absorption. The surface bound amino acids bind with the suitable substrate, that generally lead to the aggregation of nanoparticles, which eventually shift the position of surface plasmon resonant absorption and the colour of the nanoparticle’s solution (Sener et al. 2014). Many of the heavy metal ions present in the water resources can cause serious environmental and health concerns, even if they are present at very low concentrations. Functionalized gold and silver nanoparticles undergo aggregation in the presence of those metal ions and concentration of those metal ions control the extent of aggregation of nanoparticles. In most of the cases, these nanoparticles do not have any specific metal ion selectivity, rather the aggregation depends on the charge complementarity between the surface charge of the metal nanoparticles and metal ion charges. Therefore, many of these systems lack cross-selectivity when multiple ions of similar charge were present. The affinity between the functional groups and metal ions follow the hard acid-hard base and soft-acid-soft base theory, wherein soft acids prefer soft bases and hard acids prefer hard bases. Amino acids have functional groups that includes soft and hard acids; thus, they have an additional metal ion selectivity, and the cross-sensitivity can be improved. Adil Denzli and his co-workers have developed this concept and used amino acid functionalized nanoparticles as rapid and sensitive probes for various metal ions (Fig. 1.7a and b) without the need of any spectroscopic technique (Sener et al. 2014). Using this colorimetric approach, amino acid functionalized nanoparticles can selectively and simultaneously sense Hg2+, Cd2+, Fe3+, Pb2+, Al3+, Cu2+, and Cr3+ with excellent

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

23

Fig. 1.7 (a) Basis of colorimetric approach of detecting metal ions using amino acids functionalized gold nanoparticles (Sener et al. 2014) Copyright 2014, American Chemical Society; (b) Colorimetric amino acids functionalized metal nanoparticles sensor array response against various metal ions (Sener et al. 2014) Copyright 2014, American Chemical Society; (c) Selective detection of Fe3+ ions using amino acids functionalized graphene (Ma et al. 2016) Copyright 2016, Elsevier; (d) Fluorescence microscopic images of HeLa cells upon incubation with CDiso, CDgly and CDval (left)) and with PCDiso, PCDgly and PCDval (right) (Sarkar et al. 2015) Copyright 2015, Royal Society of Chemistry; (e) Fluorescence spectra of tyrosine functionalized silver nanoparticles and their quenching by the addition of Co2+ and Cu2+ ions (Contino et al. 2016) Copyright 2016, Elsevier; (f) Fluorescent emission spectra of tryptophan functionalized gold nanoparticles (Pajovic et al. 2015) Copyright 2015, Elsevier

selectivity. Binding of these different metal ions by different amino acids and the resultant aggregation of nanoparticles were the basis of this colorimetric way of sensing these many metal ions. Amino acids were found to bind with few metal ions by carboxylic acid groups, few ions by amine group and few ions by thiol group and sometimes the aromatic side chain also involve in the binding of metal ions. Size of the amino acids, their packing on the nanoparticles surface and surface charge of the nanoparticles is also responsible for their high selectivity of metal ions by different pathways. Imidazole side group of histidine amino acid has strong affinity towards copper ions, Guo et al. developed a highly selective copper ion sensor using histidine functionalized gold nanoclusters. Upon binding with Cu2+ ions, the inherent catalytic activity of these nanozymes were reduced, but the activity was restored in the absence of copper ions (Liu et al. 2017). These results indicate that the sensing performance of these clusters also modulate the catalytic properties, which can be used to quantitatively estimate the amount of copper ions. These nanoclusters were found to have similar activity like peroxidase enzyme, wherein oxidation of an organic substrate 3,30 ,5,50 -Tetramethylbenzidine (TMB) into the formation of a coloured product was considered as measure of its peroxidase activity.

24

1.6.2

S. Periasamy et al.

Fluorescence Sensing

Semiconductor nanoparticles, quantum dots and carbon dots are the nanomaterials exhibit fluorescence, as mentioned in the optical properties of these materials. Binding of target molecules or metal ions led to quench the fluorescence or enhance the fluorescence, depending upon the concentration of the analyte molecule or ion. Amino acid functionalized graphene oxide nanosheets exhibit a bright blue fluorescence, which started quenching upon the addition of Fe3+ ions selectively (Ma et al. 2016). Based on the quenching efficiency of fluorescence, a highly selective and sensitive fluorescent probe for Fe3+ ions were developed (Fig. 1.7c). Yongxin Li has developed cysteine amino acid functionalized ZnO nanoparticles and used them as fluorescent probes to detect nucleic acid (Li et al. 2004). A novel synchronous fluorescence intensity enhancement was used to quantitively measure when nucleic acids started interacting with the cysteine functionalized zinc sulfide nanoparticles. Carbon dots functionalized with amino acids were shown as fluorescent materials and this fluorescence has been utilized as fluorescence-based imaging systems. Das and his co-workers synthesized carbon dots using citric acid source along with functionalized amino acids including isoleucine, valine, and glycine, which renders these carbon dots biocompatible and water-soluble (Sarkar et al. 2015). These blue emitting carbon dots were used as fluorescent optical probe to image HeLa cells (Fig. 1.7d). Annalinda Contino et al. have developed a quantitative sensor towards copper and cobalt ions by using surface plasmon resonance (SPR) and fluorescence properties of tyrosine functionalized silver nanoparticles (Fig. 1.7e). Specifically, fluorescence-based sensor sensitivity towards these ions were found to be 40 parts per billion (ppb), which is considered as very high sensitivity. The binding of tyrosine with these ions lead to the changes in the fluorescence intensity and that change was correlated to the copper and cobalt ions concentration (Contino et al. 2016). Vladimir Djokovich and his co-workers used tryptophan functionalized gold nanoparticles as deep Ultra-violet fluorescent probes for imaging of bacterial cells (Pajovic et al. 2015). Multi-layers of tryptophan were the origin for the fluorescence and the gold nanoparticles did not quench the fluorescence from these multilayers. Auto-fluorescence from the bacteria is the main interfering factor in deep Ultraviolet imaging, while these nanoparticles fluorescence was distinctly different from the auto fluorescence (Fig. 1.7f). The presence of amino acids shell on the surface of nanoparticles was found to enhance the uptake of these nanoparticles and improves the biocompatibility of the nanoparticles.

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

1.7

25

Catalytic Role as Nanozymes

Many inorganic nanoparticles including metals and metal oxides, exhibit catalytic properties, which mimic the function of natural enzymes and these “enzyme like” properties of these materials have been exploited in therapeutics, biosensors, bio-analysis, and environmental remediation (Liang and Yan 2019). The specific kind of nanomaterials that show enzyme like activity are termed as nanozymes and received great deal of attention recently. Various kinds of nanozymes have been developed and demonstrated their potential similar to the naturally occurring enzymes such as catalases, peroxidases, oxidases and laccases (Lin et al. 2014; Monnappa et al. 2017; Zhou et al. 2017; Wu et al. 2018; Huang et al. 2019; Zhang et al. 2019). However, these nanoparticles lack the specific molecular targeting, characteristic to the natural enzymes. Presence of amino acids shell on the surface of the nanoparticles renders their surface “enzyme like” because of chirality of the amino acids, selective interaction with substrates are similar to the chiral and structural recognition of the enzymes. Thus, amino acid functionalized nanoparticles are the perfect candidates, to be considered as nanozymes because they combine the redox properties of nanoparticles and substrate selectivity of the enzymes. Developing such inorganicorganic nanomaterials that mimic the natural enzymes provide new direction for the construction of artificial nanozymes. Many of the natural enzymes are unstable under different physical conditions such as pH, temperature, and pressure etc., however amino acid functionalized nanoparticles are considered as promising alternatives. These nanoparticles were found to be stable even after complete evaporation of water as well as stability over varying pH and temperature. All the amino acids also have multi-valent system, when they were assembled on the surface of redox active nanoparticles, their collective properties combined with multivalent nature of amino acids lead to the catalytic activity.

1.7.1

Metal Nanoparticles Containing Nanozyems

Amino acid cysteine functionalized gold nanoparticles have been demonstrated to mimic the peroxidase enzyme by Qu and his co-workers (Zhou et al. 2018). These nanoparticles were confined within the channels of mesoporous silica to prevent aggregation and these channels also enable the diffusion of reactants and products to access the nanozymes. 3,4-dihydroxy-phenylalanine (DOPA) was used as substrate and cysteine functionalized gold nanoparticles catalytically oxidize 3,4-dihydroxyphenylalanine, similar to naturally available peroxidase enzymes (Fig. 1.8a). In addition, cysteine amino acids shell on the surface of gold nanoparticles exhibit chiral recognition, evidenced from their relative affinity to the chiral substrates. D-cysteine and L-cysteine were used to functionalize the nanoparticles, wherein D-cysteine functionalized gold nanoparticles show affinity towards

26

S. Periasamy et al.

Fig. 1.8 (a) Mesoporous silica supported cysteine functionalized gold nanoparticles in DOPA oxidation (Zhou et al. 2018) Copyright 2018, John Wiley and Sons; (b) Cu2+ ions concentration dependant nanozyme activity (Liu et al. 2017) Copyright 2017, Elsevier; (c) Amino acids functionalized nanoparticles and their role in 3,30 ,5,50 -Tetramethylbenzidine(TMB) oxidation (Daima 2013)

L-3,4-dihydroxy-phenylalanine substrate, while L-cysteine functionalized nanoparticles show affinity towards D-3,4-dihydroxy-phenylalanine. The chirality of the amino acids shell provides the specific molecular/ion/substrate recognition and induce aggregation through hydrogen bonded interaction. Combined with the redox properties of the nanoparticles, these nanoparticles have been shown to mimic the peroxidase enzymes. The reaction kinetics studies, and the calculated activation energies supported the mechanism of substrate selectivity and the observed activity. Like enzymes, addition of metal ions (co-factors) also tune the observed nanozyme activity of these amino acid functionalized nanoparticles. The multi-dentate nature of amino acids and their ability to bind other metal ions was found to have strong influence by enhancing or decreasing the nanozyme activity. Rong Guo and his co-workers have demonstrated the peroxidase activity of histidine functionalized gold nanoparticles, which were completely reduced when the surface bound histidine binds to copper ions (Fig. 1.8b), but its activity was restored when copper ions were removed from its surface (Liu et al. 2017).

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

27

Daima et al. observed that composition of the metal nanoparticles plays a vital role in controlling the nanozyme activity and demonstrated while studying the peroxidase kind of activity using these nanoparticles. Amino acids tyrosine and tryptophan were used to functionalize gold, silver and bimetallic nanoparticles of gold and silver of varying fraction (Fig. 1.8c). Under the same amount of metal composition and amino acid, silver nanoparticles tend to exhibit higher peroxidase activity. These results clearly suggest that nanoparticles core did not remain as passive support to amino acids, it involves the catalytic steps of the substrate. Silver nanoparticles were found to have strong peroxidase activity, as compared to gold nanoparticles.

1.7.2

Metal Oxide Nanoparticles Containing Nanozymes

Histidine amino acid is one of the active sites in horseradish peroxidase (HRP) enzyme, therefore its presence on the surface of redox active Fe3O4 nanoparticles were found to enhance the nanozyme activity, as observed by Xiyun Yan and his co-workers (Fan et al. 2017). Here the enhanced activation comes from the hydrogen binding interaction between the hydrogen peroxide (H2O2) and the histidine present on the iron oxide surface (Fig. 1.9a). These nanozymes also mimic the catalase enzyme from its enhanced affinity towards hydrogen peroxide, which again was due to the surface modification of iron oxide nanoparticles. When pure iron oxide nanoparticles or alanine capped iron oxide nanoparticles were used, their nanozyme

Fig. 1.9 (a) Histidine functionalized iron oxide (Fe3O4) nanoparticles and their nanozyme activity (Fan et al. 2016) Copyright 2016, Royal Society of Chemistry (b) Amino acids functionalized CeO2 nanoparticles and their nanozyme activity (Sun et al. 2017) Copyright 2017, John Wiley and Sons (c) Cysteine functionalized MoS2 nanoparticles nanozyme activity against TMB oxidation (Zhang et al. 2018) Copyright 2018, American Chemical Society

28

S. Periasamy et al.

activity towards hydrogen peroxide were found to be lower than the histidine capped iron oxide nanoparticles. These results support the substrate recognition of histidine on the surface of iron oxide nanoparticles retained, while the redox properties of iron oxide nanoparticles activate the hydrogen peroxide molecule. Ceria or cerium oxide nanoparticles are very well known for their redox properties and oxygen exchange characteristics. Xiaogang Qu and his co-workers have used 8 different kinds of amino acids functionalized ceria nanoparticles and these nanoparticles exhibit oxidase, superoxide dismutase and catalase like properties. Enantiomers of 3,4-dihydroxy-phenylalanine (DOPA) were used as substrate and arginine, lysine, histidine, tryptophan, tyrosine, glutamic acid, alanine, phenyl alanine amino acids were used to functionalize the ceria nanoparticles. Phenylalanine functionalized ceria nanoparticles exhibit higher catalytic activity as compared to other amino acid functionalized ceria nanoparticles. Moreover, activity was different between the two enantiomeric forms of ceria nanoparticles. Detailed kinetics of D-Phenyl alanine functionalized nanoparticles towards D and L forms of 3,4-dihydroxyphenylalanine demonstrated that selectivity of L-isomer 3.12  103 s1 was found to be higher than D isomer 1.94  103 s1. These studies again demonstrated that ceria active site combined with chiral recognition site of phenylalanine amino acid exhibited the enhanced activity towards nanozyme mediated oxidation of 3,4-dihydroxy-phenylalanine (Fig. 1.9b). Two-dimensional transition metal chalcogenides such as molybdenum disulphide (MoS2) are the novel semiconductor nanoparticles, which have received significant attention in the recent past. These 2D semiconductors functionalized with amino acids, exhibit interesting chiroptical properties. Weili Wei and his co-workers have shown that these nanoparticles exhibit peroxidase kind of activity and the chiral amino acids such as cysteine exhibit enantioselectivity. Pure molybdenum disulphide sheets and cysteine functionalized nanosheets did not show such activity (Fig. 1.9c). Interestingly addition of copper ions turn on the nanozyme activity (Zhang et al. 2018). In general, the enzyme activity of natural enzymes in the presence of metal ions either enhanced or reduced. In this case, cysteine capped molybdenum disulphide nanoparticles in the presence of copper ions catalyze the oxidation of L-tyrosine. Again, the chirality of cysteine and tyrosine play a key role in substrate selectivity. From the above-mentioned studies, all these amino acid functionalized nanoparticles have been demonstrated to catalyze mainly redox reactions because the inorganic nanoparticles are well-known redox catalysts. However, there is a large scope to extend the application of these materials as nanozymes towards other reactions including hydrolysis, ligation, and transesterification reactions.

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

1.8

29

Conclusion and Prospects

In this book chapter, we have provided an insight on various aspects of amino acids functionalized nanoparticles ranging from their synthesis, optical properties, interactions between amino acids and nanoparticles to environmental engineering applications including chiral separation, ion sensing and nanozymes. The use of amino acid conjugation to nanoparticles is an interesting area to develop a biocompatible, nanostructured chiral surface, recognition motifs towards proteins and DNA bioconjugates by using simple synthetic methods. Therefore, a variety of nanomaterials have been designed to mimic the characteristics of natural enzymes, which makes materials as bridge between nanomaterials and biological sciences. Chiral amino acids organized on the surface of the nanoparticles create a chiral nanostructured surface and these materials exhibit unique chiro-optical properties. The nanostructured chiral surface renders the surface enantioselective, which let these nanomaterials to separate enantiomers from their racemic mixture. In addition, the amino acid shell composition controls its binding to specific protein, DNA, and other biomolecules, therefore substrate specific recognition can be used to study protein and DNA nanoparticle interactions. Also, the nature of amino acids presents on the nanoparticles surface and its ability to bind any selective ions or molecules, led these materials as novel colorimetric, fluorescent, and chiral probes. Finally, the synergistic combination of catalytic properties of nanomaterials and recognition properties of amino acids can make these materials as effective nanozymes. Taken together, amino acids functionalized inorganic nanomaterials will have a great potential to be specifically used for environmental applications such as molecular and ion sensing, stable enzyme analogues, suitable biocompatibility, and less environmental impact. These functional nanomaterials provide a better scope to develop next generation smart materials and sensing platforms for biological and environmental engineering applications.

References Bayraktar H, You C-C, Rotello VM, Knapp MJ (2007) Facial control of nanoparticle binding to cytochrome c. J Am Chem Soc 129(10):2732–2733 Chakraborty A, Boer JC, Selomulya C, Plebanski M (2018) Amino acid functionalized inorganic nanoparticles as cutting-edge therapeutic and diagnostic agents. Bioconjug Chem 29 (3):657–671 Chen JLY, Pezzato C, Scrimin P, Prins LJ (2016) Chiral Nanozymes – gold nanoparticle-based Transphosphorylation catalysts capable of Enantiomeric discrimination. Chem Eur J 22 (21):7028–7032 Contino A, Maccarrone G, Zimbone M, Reitano R, Musumeci P, Calcagno L, Oliveri IP (2016) Tyrosine capped silver nanoparticles: a new fluorescent sensor for the quantitative determination of copper(II) and cobalt(II) ions. J Colloid Interface Sci 462:216–222

30

S. Periasamy et al.

Daima HK (2013) Towards fine-tuning the surface corona of inorganic and organic nanomaterials to control their properties at nano-bio interface. PhD Thesis, RMIT University Melbourne https://researchbank.rmit.edu.au/view/rmit:160416 Daima HK, Selvakannan PR, Kandjani AE, Shukla R, Bhargava SK, Bansal V (2014) Synergistic influence of polyoxometalate surface corona towards enhancing the antibacterial performance of tyrosine-capped Ag nanoparticles. Nanoscale 6(2):758–765 Daima HK, Selvakannan PR, Shukla R, Bhargava SK, Bansal V (2013) Fine-tuning the antimicrobial profile of biocompatible gold nanoparticles by sequential surface functionalization using polyoxometalates and lysine. PLoS One 8(10):e79676 Daniel M-C, Astruc D (2004) Gold nanoparticles: assembly, supramolecular chemistry, quantumsize-related properties, and applications toward biology, catalysis, and nanotechnology. Chem Rev 104(1):293–346 De M, You C-C, Srivastava S, Rotello VM (2007) Biomimetic interactions of proteins with functionalized nanoparticles: a thermodynamic study. J Am Chem Soc 129(35):10747–10753 El-Sayed MA (2001) Some interesting properties of metals confined in time and nanometer space of different shapes. Acc Chem Res 34(4):257–264 El-Trass A, El Shamy H, El-Mehasseb I, El-Kemary M (2012) CuO nanoparticles: synthesis, characterization, optical properties and interaction with amino acids. Appl Surf Sci 258 (7):2997–3001 Fan K, Wang H, Xi J, Liu Q, Meng X, Duan D, Gao L, Yan X (2017) Optimization of Fe3O4 nanozyme activity via single amino acid modification mimicking an enzyme active site. Chem Commun (Camb) 53(2):424–427 Gao J, Fei X, Li G, Jiang Y, Li S (2018) The effects of QD stabilizer structures on pH dependence, fluorescence characteristics, and QD sizes. J Phys D Appl Phys 51(28):285101 Gao Q, Xu W, Xu Y, Wu D, Sun Y, Deng F, Shen W (2008) Amino acid adsorption on Mesoporous materials: influence of types of amino acids, modification of Mesoporous materials, and solution conditions. J Phys Chem B 112(7):2261–2267 Gao X, Chen Z, Yao Y, Zhou M, Liu Y, Wang J, Wu WD, Chen XD, Wu Z, Zhao D (2016) Direct heating amino acids with silica: a universal solvent-free assembly approach to highly nitrogendoped Mesoporous carbon materials. Adv Funct Mater 26(36):6649–6661 Ghosh PS, Han G, Erdogan B, Rosado O, Krovi SA, Rotello VM (2007) Nanoparticles featuring amino acid-functionalized side chains as DNA receptors. Chem Biol Drug Des 70(1):13–18 Ghosh PS, Kim C-K, Han G, Forbes NS, Rotello VM (2008) Efficient gene delivery vectors by tuning the surface charge density of amino acid-functionalized gold nanoparticles. ACS Nano 2 (11):2213–2218 Green M (2004) Semiconductor quantum dots as biological imaging agents. Angew Chem Int Ed Engl 43(32):4129–4131 Guarise C, Manea F, Zaupa G, Pasquato L, Prins LJ, Scrimin P (2008) Cooperative nanosystems. J Pept Sci 14(2):174–183 Huang Y, Ren J, Qu X (2019) Nanozymes: classification, catalytic mechanisms, activity regulation, and applications. Chem Rev 119(6):4357–4412 Jain PK, Huang X, El-Sayed IH, El-Sayed MA (2008) Noble metals on the nanoscale: optical and photothermal properties and some applications in imaging, sensing, biology, and medicine. Acc Chem Res 41(12):1578–1586 Jaiswal JK, Simon SM (2004) Potentials and pitfalls of fluorescent quantum dots for biological imaging. Trends Cell Biol 14(9):497–504 Joshi H, Shirude PS, Bansal V, Ganesh KN, Sastry M (2004) Isothermal titration calorimetry studies on the binding of amino acids to gold nanoparticles. J Phys Chem B 108 (31):11535–11540 Kango S, Kalia S, Celli A, Njuguna J, Habibi Y, Kumar R (2013) Surface modification of inorganic nanoparticles for development of organic–inorganic nanocomposites—a review. Prog Polym Sci 38(8):1232–1261

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

31

Kasture M, Sastry M, Prasad BLV (2010) Halide ion controlled shape dependent gold nanoparticle synthesis with tryptophan as reducing agent: enhanced fluorescent properties and white light emission. Chem Phys Lett 484(4–6):271–275 Keshvari F, Bahram M, Farshid AA (2015) Gold nanoparticles biofunctionalized (grafted) with chiral amino acids: a practical approach to determining the enantiomeric percentage of racemic mixtures. Anal Methods 7(11):4560–4567 Lacasta S, Sebastián V, Casado C, Mayoral Á, Romero P, Larrea Á, Vispe E, López-Ram-de-Viu P, Uriel S, Coronas J (2011) Chiral imprinting with amino acids of ordered Mesoporous silica exhibiting Enantioselectivity after calcination. Chem Mater 23(5):1280–1287 Ladbury JE, Chowdhry BZJC (1996) Sensing the heat: the application of isothermal titration calorimetry to thermodynamic studies of biomolecular interactions. Chem Biol 3(10):791–801 Li G, Fei X, Liu H, Gao J, Nie J, Wang Y, Tian Z, He C, Wang J-L, Ji C, Dan O, Yang G (2020) Fluorescence and optical activity of chiral CdTe quantum dots in their interaction with amino acids. ACS Nano 14(4):4196–4205 Li Y, Chen J, Zhu C, Wang L, Zhao D, Zhuo S, Wu Y (2004) Preparation and application of cysteine-capped ZnS nanoparticles as fluorescence probe in the determination of nucleic acids. Spectrochim Acta A Mol Biomol Spectrosc 60(8):1719–1724 Liang M, Yan X (2019) Nanozymes: from new concepts, mechanisms, and standards to applications. Acc Chem Res 52(8):2190–2200 Lin Y, Ren J, Qu X (2014) Catalytically active nanomaterials: a promising candidate for artificial enzymes. Acc Chem Res 47(4):1097–1105 Liu Y, Ding D, Zhen Y, Guo R (2017) Amino acid-mediated ‘turn-off/turn-on’ nanozyme activity of gold nanoclusters for sensitive and selective detection of copper ions and histidine. Biosens Bioelectron 92:140–146 Liu Y, Wang X, Wei H (2020) Light-responsive nanozymes for biosensing. Analyst (Cambridge, U. K.): Ahead of Print Ma J, Qiu J, Wang S (2020) Nanozymes for catalytic Cancer immunotherapy. ACS Appl Nano Mater 3(6):4925–4943 Ma Q, Song J, Wang S, Yang J, Guo Y, Dong C (2016) A general sensing strategy for detection of Fe3+ by using amino acid-modified graphene quantum dots as fluorescent probe. Appl Surf Sci 389:995–1002 Mandal G, Bhattacharya S, Ganguly T (2009) Nature of interactions of tryptophan with zinc oxide nanoparticles and L-aspartic acid: a spectroscopic approach. Chem Phys Lett 472(1–3):128–133 Mandal S, Selvakannan PR, Phadtare S, Pasricha R, Sastry M (2002) Synthesis of a stable gold hydrosol by the reduction of chloroaurate ions by the amino acid, aspartic acid. Proc. – Indian Acad. Sci. Chem Sci 114(5):513–520 Monnappa KJS, Firdose N, Shree GM, Nath K, Navya PN, Daima HK (2017) Influence of amino acid corona, metallic core and surface functionalisation of nanoparticles on their in-vitro biological behaviour. Int J Nanotechnol 14(9–11):816–832 Pajovic JD, Dojcilovic R, Bozanic DK, Kascakova S, Refregiers M, Dimitrijevic-Brankovic S, Vodnik VV, Milosavljevic AR, Piscopiello E, Luyt AS, Djokovic V (2015) Tryptophanfunctionalized gold nanoparticles for deep UV imaging of microbial cells. Colloids Surf B Biointerfaces 135:742–750 Parak WJ, Gerion D, Pellegrino T, Zanchet D, Micheel C, Williams SC, Boudreau R, Gros MAL, Larabell CA, Alivisatos AP (2003) Biological applications of colloidal nanocrystals. Nanotechnology 14(7):R15–R27 Pasquato L, Pengo P, Scrimin P (2004) Functional gold nanoparticles for recognition and catalysis. J Mater Chem 14(24):3481–3487 Pasquato L, Pengo P, Scrimin P (2005) Nanozymes: functional nanoparticle-based catalysts. Supramol Chem 17(1–2):163–171 Plascencia-Villa G, Torrente D, Marucho M, Jose-Yacaman M (2015) Biodirected synthesis and Nanostructural characterization of anisotropic gold nanoparticles. Langmuir 31(11):3527–3536

32

S. Periasamy et al.

Sarkar S, Das K, Ghosh M, Das PK (2015) Amino acid functionalized blue and phosphorous-doped green fluorescent carbon dots as bioimaging probe. RSC Adv 5(81):65913–65921 Sastry M, Rao M, Ganesh KN (2002) Electrostatic assembly of nanoparticles and biomacromolecules. Acc Chem Res 35(10):847–855 Sastry M, Swami A, Mandal S, Selvakannan PR (2005) New approaches to the synthesis of anisotropic, core-shell and hollow metal nanostructures. J Mater Chem 15(31):3161–3174 Scrimin P, Prins LJ (2011) Sensing through signal amplification. Chem Soc Rev 40(9):4488–4505 Selvakannan PR, Mandal S, Phadtare S, Gole A, Pasricha R, Adyanthaya SD, Sastry M (2004a) Water-dispersible tryptophan-protected gold nanoparticles prepared by the spontaneous reduction of aqueous chloroaurate ions by the amino acid. J Colloid Interface Sci 269(1):97–102 Selvakannan PR, Mandal S, Phadtare S, Pasricha R, Sastry M (2003) Capping of gold nanoparticles by the amino acid lysine renders them water-dispersible. Langmuir 19(8):3545–3549 Selvakannan PR, Mantri K, Tardio J, Bhargava SK (2013a) High surface area au-SBA-15 and au-MCM-41 materials synthesis: tryptophan amino acid mediated confinement of gold nanostructures within the mesoporous silica pore walls. J Colloid Interface Sci 394:475–484 Selvakannan PR, Ramanathan R, Plowman BJ, Sabri YM, Daima HK, O’Mullane AP, Bansal V, Bhargava SK (2013b) Probing the effect of charge transfer enhancement in off resonance mode SERS via conjugation of the probe dye between silver nanoparticles and metal substrates. Phys Chem Chem Phys 15(31):12920–12929 Selvakannan PR, Swami A, Srisathiyanarayanan D, Shirude PS, Pasricha R, Mandale AB, Sastry M (2004b) Synthesis of aqueous Au core-Ag shell nanoparticles using tyrosine as a pH-dependent reducing agent and assembling phase-transferred silver nanoparticles at the air-water interface. Langmuir 20(18):7825–7836 Sener G, Uzun L, Denizli A (2014) Colorimetric sensor Array based on gold nanoparticles and amino acids for identification of toxic metal ions in water. ACS Appl Mater Interfaces 6 (21):18395–18400 Sethi M, Law W-C, Fennell WA, Prasad PN, Knecht MR (2011) Employing materials assembly to elucidate surface interactions of amino acids with Au nanoparticles. Soft Matter 7 (14):6532–6541 Shenhar R, Rotello VM (2003) Nanoparticles: scaffolds and building blocks. Acc Chem Res 36 (7):549–561 Shukla N, Bartel MA, Gellman AJ (2010) Enantioselective separation on chiral Au nanoparticles. J Am Chem Soc 132(25):8575–8580 Song W, Zhao B, Wang C, Ozaki Y, Lu X (2019) Functional nanomaterials with unique enzymelike characteristics for sensing applications. J Mater Chem B 7(6):850–875 Sun Y, Zhao C, Gao N, Ren J, Qu X (2017) Stereoselective nanozyme based on ceria nanoparticles engineered with amino acids. Chem Eur J 23(72):18146–18150 Talwatkar SS, Tamgadge YS, Sunatkari AL, Gambhire AB, Muley GG (2014) Amino acids (L-arginine and L-alanine) passivated CdS nanoparticles: synthesis of spherical hierarchical structure and nonlinear optical properties. Solid State Sci 38:42–48 Templeton AC, Wuelfing WP, Murray RW (2000) Monolayer-protected cluster molecules. Acc Chem Res 33(1):27–36 Thomas KG, Kamat PV (2003) Chromophore-functionalized gold nanoparticles. Acc Chem Res 36 (12):888–898 Trindade T, O’Brien P, Pickett NL (2001) Nanocrystalline semiconductors: synthesis, properties, and perspectives. Chem Mater 13(11):3843–3858 Vaz PD, Nunes CD (2010) A new role for layered double hydroxides hybrid materials-uptake and delivery of small molecules into the gas phase. New J Chem 34(3):541–546 Wang J, Katahara JK, Kumamoto A, Tohei T, Sugawara-Narutaki A, Shimojima A, Okubo T (2014) Synthesis of string-bean-like anisotropic titania nanoparticles with basic amino acids. RSC Adv 4(18):9233–9235 Wang J, Sugawara A, Shimojima A, Okubo T (2010) Preparation of anisotropic silica nanoparticles via controlled assembly of Presynthesized spherical seeds. Langmuir 26(23):18491–18498

1 Amino Acids Functionalized Inorganic Metal Nanoparticles: Synthetic Nanozymes. . .

33

Wangoo N, Bhasin KK, Mehta SK, Suri CR (2008) Synthesis and capping of water-dispersed gold nanoparticles by an amino acid: bioconjugation and binding studies. J Colloid Interface Sci 323 (2):247–254 Wei H, Wang E (2013) Nanomaterials with enzyme-like characteristics (nanozymes): nextgeneration artificial enzymes. Chem Soc Rev 42(14):6060–6093 Williams TJ, Reay AJ, Whitwood AC, Fairlamb IJS (2014) A mild and selective Pd-mediated methodology for the synthesis of highly fluorescent 2-arylated tryptophans and tryptophancontaining peptides: a catalytic role for Pd0 nanoparticles? Chem Commun (Camb) 50 (23):3052–3054 Wu J, Li S, Wei H (2018) Integrated nanozymes: facile preparation and biomedical applications. Chem Commun (Camb) 54(50):6520–6530 Xiao L, Yeung ES (2014) Optical imaging of individual Plasmonic nanoparticles in biological samples. Annu Rev Anal Chem 7(1):89–111 Yadav RS, Mishra P, Mishra R, Kumar M, Pandey AC (2010) Growth mechanism and optical property of CdS nanoparticles synthesized using amino-acid histidine as chelating agent under sonochemical process. Ultrason Sonochem 17(1):116–122 Yang X, Shi M, Zhou R, Chen X, Chen H (2011) Blending of HAuCl4 and histidine in aqueous solution: a simple approach to the Au10 cluster. Nanoscale 3(6):2596–2601 Yin Y, Talapin D (2013) The chemistry of functional nanomaterials. Chem Soc Rev 42 (7):2484–2487 You C-C, Agasti SS, De M, Knapp MJ, Rotello VM (2006) Modulation of the catalytic behavior of α-chymotrypsin at monolayer-protected nanoparticle surfaces. J Am Chem Soc 128 (45):14612–14618 You C-C, Agasti SS, Rotello VM (2008) Isomeric control of protein recognition with amino acidand dipeptide-functionalized gold nanoparticles. Chem Eur J 14(1):143–150 You C-C, De M, Han G, Rotello VM (2005a) Tunable inhibition and denaturation of α-chymotrypsin with amino acid-functionalized gold nanoparticles. J Am Chem Soc 127 (37):12873–12881 You C-C, De M, Rotello VM (2005b) Contrasting effects of exterior and interior hydrophobic moieties in the complexation of amino acid functionalized gold clusters with α-chymotrypsin. Org Lett 7(25):5685–5688 Zhang H, He H, Jiang X, Xia Z, Wei W (2018) Preparation and characterization of chiral transitionmetal Dichalcogenide quantum dots and their enantioselective catalysis. ACS Appl Mater Interfaces 10(36):30680–30688 Zhang R, Zhou Y, Yan X, Fan K (2019) Advances in chiral nanozymes: a review. Microchim Acta 186(12):782 Zhang Y, Hong H, Myklejord DV, Cai W (2011) Molecular imaging with SERS-active nanoparticles. Small 7(23):3261–3269 Zhou Y, Liu B, Yang R, Liu J (2017) Filling in the gaps between Nanozymes and enzymes: challenges and opportunities. Bioconjug Chem 28(12):2903–2909 Zhou Y, Sun H, Xu H, Matysiak S, Ren J, Qu X (2018) Mesoporous encapsulated chiral Nanogold for use in enantioselective reactions. Angew Chem Int Ed 57(51):16791–16795 Zhu Z, Liu W, Li Z, Han B, Zhou Y, Gao Y, Tang Z (2012) Manipulation of collective optical activity in one-dimensional Plasmonic assembly. ACS Nano 6(3):2326–2332 Zou J, Guo Z, Parkinson JA, Chen Y, Sadler PJ (1999) Gold(III)-induced oxidation of glycine. Chem Commun (Camb) 15:1359–1360

Chapter 2

Thermal Decomposition Routes for Magnetic Nanoparticles: Development of Next-Generation Artificial Enzymes, Their Phase Transfer and Biological Applications Mandeep Singh and Hemant Kumar Daima

Abstract In this chapter, we present a detailed overview of the effect of various synthesis parameters, in obtaining the iron oxide nanoparticles (IONPs) via thermal decomposition of the iron oleate (FeOL) precursor and how they can be utilised for various biological applications like nanozymes via the phase transfer mechanisms. This procedure is well followed by the LaMer diagram, where the separation between nucleation and growth stages is well under control. Detailed overview of the reaction mechanism and the various parameters like temperature; heating rates; reflux time; addition of surfactants and additives etc. are discussed in detail. At the end, the core-shell nature of the final product is being discussed in terms of its structural and magnetic properties. Keywords Iron oxide nanoparticles · Nanozymes · Magnetism · Thermal decomposition · Phase transfer

Abbreviations FeOL IONPs MNPs NaOL NCs OA

Iron oleate Iron oxide nanoparticles Magnetic nanoparticles Sodium oleate Iron oxide nanocrystals Oleic acid

M. Singh (*) School of Science, RMIT University, Melbourne, VIC, Australia e-mail: [email protected] H. K. Daima Amity Center for Nanobiotechnology and Nanomedicine (ACNN), Amity University Rajasthan, Jaipur, Rajasthan, India © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 H. K. Daima et al. (eds.), Nanozymes for Environmental Engineering, Environmental Chemistry for a Sustainable World 63, https://doi.org/10.1007/978-3-030-68230-9_2

35

36

M. Singh and H. K. Daima

ODE NaCl FTIR XPS DSC XRD TEM HRTEM XAS XMCD PXRD STEM HAADF TG-MS DTG CA DMSA CSO PBS HBSS DMEM FBS PEG

2.1

1-octadecene Sodium chloride Fourier-transform infrared spectroscopy X-ray photoelectron spectroscopy Differential scanning calorimetry X-ray powder diffraction Transmission electron microscopy High resolution transmission electron microscopy X-Ray absorption spectroscopy X-ray magnetic circular dichroism Powder X-ray diffraction Scanning transmission electron microscopy High-angle annular dark-field Thermogravimetric-mass spectrometric analysis Differential thermogravimetric Citric acid Meso-2,3-dimercaptosuccinic acid Chitosan oligosaccharide Phosphate-buffered saline Hank’s balanced salt solution Dulbecco’s modified eagle’s medium Fetal bovine serum Poly(ethylene glycol)

Introduction

Magnetic nanoparticles (MNPs) are of great fundamental and technological interest because of their unique magnetic properties (superparamagnetism), high coercivity, low Curie temperature, high magnetic susceptibility, etc. The magnetic nanoparticles can bind to drugs, proteins, enzymes, antibodies, or nucleotides and can be efficiently employed as targeted drug delivery vehicles, and they find prime position in several biomedical applications like cell labelling and imaging (Weis et al. 2014; Kolosnjaj-Tabi et al. 2013); tissue repair (Meng et al. 2013); cell targeting (Nowicka et al. 2013; Hansen et al. 2013; Cheng et al. 2014); hyperthermia (Singh et al. 2013a; Kobayashi 2011; Martinez-Boubeta et al. 2013); magnetic biosensing (Wang et al. 2011; Ali et al. 2013, Kaushik et al. 2008; Haun et al. 2010); biomagnetic separation (Chen et al. 2012; Park et al. 2007); and magnetic resonance imaging (Li et al. 2013; Sun et al. 2008; Babes et al. 1999; Kim et al. 2001). Numerous methods have been used to obtain the magnetic nanoparticles like precipitation (Salavati-Niasari et al. 2012; Pereira et al. 2012); hydrothermal (Sun et al. 2009); sol-gel (Qi et al. 2011); microemulsion (Okoli et al. 2011; Okoli et al. 2012); sonolysis (Xu et al. 2013), thermal decomposition of organometallic compounds (Bao et al. 2012; Bloemen et al. 2012; Bronstein et al. 2007; Johnson et al.

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

37

Fig. 2.1 Crystal structure and crystallographic data of the hematite (a), magnetite (b), and maghemite (c) (the black ball is Fe2+, the green ball is Fe3+ and the red ball is O2
). (Adopted with permission from Wei et al. 2015)

2012; Chen 2012; Demortiere et al. 2011; Ding et al. 2014; Erik et al. 2014; Faure et al. 2013; Hufschmid et al. 2015; Kovalenko et al. 2007; Lynch et al. 2011; Park et al. 2004; Xu et al. 2010; Zhao et al. 2013); polyol (Laurent et al. 2008); microwave (You et al. 2012); laser pyrolysis (Martínez et al. 2012); electrochemical (Cabrera et al. 2008); vapour phase (Singh et al. 2013b); arc discharge (Sun et al. 2000); and biosynthesis (Sundaram et al. 2012; Bharde et al. 2006). Based on the synthesis method, various iron oxide phases have been successfully obtained in different sizes and shapes like wustite (FeO), magnetite (Fe3O4), hematite (α-Fe2O3), maghemite (γFe2O3), β- Fe2O3, ε- Fe2O3, etc. Among them, hematite, magnetite, and maghemite are the most promising materials due to their unique biological, chemical, magnetic, and catalytic properties. Being high corrosion resistant and low-cost material, hematite is widely applied as catalyst, pigments, and gas sensors (Wei et al. 2015). On the other hand, due to biocompatibility and chemical stability, magnetite and maghemite are being employed in the biological applications. The structural difference between magnetite and maghemite is that the magnetite has a cubic inverse spinel structure that consists of a cubic close-packed array along the direction of 32 oxide ions O2
, where all of the divalent iron i.e. Fe2+ occupy half of the octahedral sites and the trivalent iron i.e. Fe3+ are split evenly across the remaining octahedral and tetrahedral sites. In comparison to magnetite, maghemite cubic structure, have 32 oxide ions O2
and the Fe2+ are distributed over tetrahedral sites (eight Fe ions per unit cell) and octahedral sites (the remaining Fe ions and vacancies) as shown in Fig. 2.1. In simpler terms, the maghemite can be considered as fully oxidized magnetite, thus having less bulk saturation magnetisation of 72 emu/g as compared to 92 emu/g of magnetite. To obtain the iron oxide nanoparticles, especially the maghemite and magnetite co-precipitation method is most widely followed due to its facile approach and gramscale production (Pereira et al. 2012, Salavati-Niasari et al. 2012, Laurent et al. 2008). This method allows the chemical reaction to happen under the inert atmospheric conditions while taking the stoichiometric ratio of 2:1 (Fe3+/Fe2+) in the

38

M. Singh and H. K. Daima

presence of the base such as ammonium hydroxide (NH4OH) at pH 8–14 as per equation1 (Laurent et al. 2008; Singh et al. 2013a): Fe2þ þ 2Fe3þ þ 8OH
! Fe3 O4 þ 4H2 O

ð2:1Þ

The obtained magnetite phase is very sensitive to oxidation, and transformed in the presence of oxygen into stable maghemite phase according to the following equation (Laurent et al. 2008): Fe3 O4 þ 2Hþ ! γFe2 O3 þ Fe2þ þ H2 O

ð2:2Þ

In this method, the nanoparticle growth kinetics is not easily controlled, and one can end up with irregular morphologies having large particle size distribution. Thus, puts a big limitation of its usage for the synthesis of iron oxide nanoparticles specifically for biomedical or nanozyme applications. To remove this limitation by providing better control over nanoparticle growth kinetics, a new method known as high temperature thermal decomposition in organic solvents has been developed (Bloemen et al. 2012; Bronstein et al. 2007; Lynch et al. 2011; Park et al. 2004), wherein, ferric salts such as iron pentacarbonyl, ferric acetylacetonate, Fe(Cup)3 (Cup ¼ N-nitrosophenylhydroxylamine), iron oleate, prussian blue, ferrocene etc. are being used in various solvents like 1-octadecene (ODE); di-phenyl ether; di-noctyl ether; di-n-hexyl ether; dibenzyl ether; 1-hexadecene; 1-tetradecene; n-docosane; n-tetracosane; trioctylamine; 1-eicosene; squalene; oleylamine etc. in order to have different decomposition temperatures (Woo et al. 2004; Wang et al. 2012; Liang et al. 2006; Hu et al. 2012; Amara and Margel 2011; Kovalenko et al. 2007; Lynch et al. 2011; Park et al. 2004). However, thermal decomposition of the iron oleate is widely being followed by material researchers because of its non-toxic and inexpensive iron chloride as the starting precursor. Here, oleic acid (OA) acts as both stabilizer and reducing agent, where it’s carboxylic acid headgroups coordinate with Fe atoms of the nanoparticles via a bidentate chelating mechanism, facilitating the nucleation and growth of iron oxide nanoparticles, thus obtaining nanoparticles with narrow particle size distribution. Different shapes and sizes of the nanoparticles can be obtained by altering the various reaction conditions like temperature, heating rate, refluxing, the addition of various surfactants and additives, etc. (Bronstein et al. 2007; Chen 2012; Kovalenko et al. 2007; Lynch et al. 2011; Park et al. 2004). Recently, it has been observed that the structure of the iron oleate also dictates the quality and morphology of the final product. Therefore, it is highly recommended that one should have its full structural and chemical knowledge before they being thermally decomposed (Bronstein et al. 2007; Chen 2012; Demortiere et al. 2011; Ding et al. 2014; Erik et al. 2014; Hufschmid et al. 2015). This book chapter aims to provide a deeper look into the chemical nature of the iron oleate and how one can exploit various synthesis parameters to obtain well designed iron oxide nanoparticles

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

39

with interesting structural morphologies that will dictate its final phase, magnetism, and chemical reactivity.

2.2 2.2.1

Nanoparticle Synthesis Nanoparticle Reaction Kinetics

Monodisperse iron oxide nanoparticle formation from the iron oleate decomposition is known to follow the LaMer diagram, which divides the particle-formation process into three major stages: prenucleation, nucleation, and growth. The particle nucleation takes place when the concentration of the active monomer reaches a threshold (known as the critical supersaturation point) and ends when the monomer concentration falls below this threshold, resulting in the separation of the nucleation stage i.e. the formation of nuclei and growth stage i.e. the growth of the nuclei during the particle formation (Bronstein et al. 2007; Chen 2012; Park et al. 2004). The nucleation and growth stages needed to be separated, where larger the separation higher the probability of obtaining the monodisperse nanoparticles. If these two stages overlap, polydisperse nanoparticles are typically obtained. In the iron oleate complex decomposition, nucleation stage starts, when one oleate group dissociates from the precursors at 200–240  C by carbon dioxide (CO2) elimination, whereas the growth stage occurs at about 300  C (although slow growth seems to occur at 82%) is used for the synthesis of precursor complex, frequently it resulted in cubic nanoparticles without any addition of more sodium oleate in the reaction system. They believed that low-grade sodium oleate contains

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

47

Fig. 2.7 (a) (A) and (B) TEM images of iron oxide nanoplates, inset in (B) shows the HRTEM of the nanoplates standing on their edges; (C) histogram of the nanoplates lateral dimensions presented in (A); (D) HRTEM image of the nanoplates; (E) X-ray diffraction data of iron oxide nanoplates synthesized at 240  C; (F) core-level X-ray photoelectron spectrum of nanoplates; (b) TEM images (A–C) showing solvent effect on iron oxide nanocrystal morphology with iron oxide formed in (A) oleylamine, (B) benzyl ether, and (C) 1-dodecanol, respectively. (D–F) Influence of Fe precursors on thermal decomposition, with TEM images showing the resulting nanocrystals using (D) iron acetate, (E) iron laurate, and (F) iron stearate, respectively. (Adopted with permission from Ding et al. 2014).

Fig. 2.8 Types of metal carboxylate coordination modes; For simplicity, the monovalent metal is shown instead of trivalent [broeinstein]. (Adopted with permission from Bronstein et al. 2007)

48

M. Singh and H. K. Daima

fatty acids of varying chain lengths, which results in iron-precursors with different decomposition temperatures. Similarly, Faure et al. (2013), obtained spheroidal nanoparticles, when using sodium oleate (82%), in the formation of iron oleate for the synthesis of nanoparticles in 1-octadecene at 320  C/min.

2.3.4

Surfactants and Additives

It has been observed that thermal decomposition of the iron oleate, nature and amount of the surfactants, halides can dramatically affect the final nanocrystal product (Chen 2012; Ding et al. 2014; Faure et al. 2013; Pichon et al. 2011). With the increase in the oleic acid concentrations with reference to iron oleate, the size of the nanoparticles increases (Park et al. 2004; Wetterskog et al. 2013). Similarly, it is described that size of the nanoparticles increases with increasing oleic acid concentration. It has been reported that to generate monodisperse nanoparticles, the oleic acid: iron oleate should be in the range of 0.1–10 M and polydisperse for a higher range of greater than 10 M (Chen 2012). It has been observed that with an increase in ligand concentration, the average diameter of the nanoparticle increases, due to the slowdown of the nucleation step by reacting with iron oleate to form more stable complexes which result in a small number of nuclei and size is mainly controlled by the growth step only and in a worse case, the reaction can be inhibited with a large amount of oleic acid (Demortiere et al. 2011; Salas et al. 2012; Hufschmid et al. 2015). Like, Hufschmid et al. (2015) also observed that the addition of excess oleic acid to the iron oleate precursor, nucleation was delayed up to several hours and one can tune the particle size from 10–25 nm as shown in Fig. 2.13. Similarly, Salas et al. (2012) also observed that without oleic acid as a surfactant, the thermal decomposition of Fe-oleate in 1-octadecene (315  C), yields particles with wide size distribution (Fig. 2.9).

Fig. 2.9 Superparamagnetic iron oxide nanoparticles produced by thermal decomposition of iron (III) oleate in the presence of excess oleic acid. Size is shown as a function of (a) precursor concentration, (b) excess oleic acid, and (c) aging time. All sizes are median diameter (DM) and error bars represent the first standard deviation of the log-normal size distribution (σ), determined by fitting VSM measurements. (Adopted with permission from Hufschmid et al. 2015)

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

49

Shavel and Liz-Marzan (2009) shows the importance of special additives that can be added along with oleic acid in the thermal decomposition of the iron oleate. They obtained cubic nanoparticles (in the presence of sodium oleate or sodium carbonate) and octahedrons (in the presence of quaternary ammonium salts like tetraoctylammonium bromide), respectively. Kovalenko et al. (2007) observed that the use of sodium oleate increases the nucleation threshold temperatures which result in a smaller number of nuclei, and larger sizes of nanocubes are obtained in comparison to spheres obtained under the same conditions in the presence of oleic acid or dibutylammonium oleate. On the other hand, with potassium oleate they obtained a mixture of cubes with other faceted along with irregularly shaped particles. Further, by decreasing the sodium oleate concentration with respect to iron oleate complex during the thermal decomposition in 1-octadecene (318  C), the structure of the iron oxide nanocrystals changes from cubes (~23 nm) to the mixture of bipyramids (~35 nm) plus cubes (~15 nm), respectively. Recently, Zhao et al. (2013), obtained octapod shaped nanocrystals from the decomposition of the iron oleate in 1-octadecene (320  C) in the presence of sodium chloride and oleic acid. They believe that such shape is the result of the presence of chloride ions throughout the particle growth process. A similar observation is also being found by Xu et al. (2010), where they obtain cubic crystals in the presence of sodium chloride salt.

2.3.5

Heating Rate and Reflux Time (Including Aging Factor)

The heating rate plays an important role in the synthesis of nanoparticles, as it dictates the boundaries between the nucleation and the growth stages of the crystal formation. It has been observed that the heating rate has a more pronounced effect on the final crystal size formation rather than their morphologies (Chen 2012; Demortiere et al. 2011; Ding et al. 2014; Faure et al. 2013; Hu et al. 2012; Hufschmid et al. 2015; Kovalenko et al. 2007). Chen (2012), obtained polydisperse nanoparticles after thermal decomposition of iron oleate in octadecene at 320  C at 10  C/min heating rate, whereas no nanoparticles are obtained when the heating rate increased to 20  C/min, due to the incompleteness of the nucleation and the subsequent failure of the growth. On the other hand, heating at 1  C/min, favours the formation of larger stable nuclei and thus leads to a slight increase in size. Likewise, Kovalenko et al. (2007), obtain 22 nm cubes during the thermal decomposition of the iron oleate in 1-octadecene (318  C) if the heating rate decreased from 3.3  C/min to 1  C/min. Wetterskog et al. (2013), also found that heating rate at 2.2  C/min resulted in the formation of polydisperse particles, but it had a negligible effect within 2.6–3.3  C/min range. Similarly, Pichon et al. (2011), obtained the nanoparticles with an average size of 16.5 nm (NC-16) and 13.2 nm (NC-13) after the heating rate is increased from 1  C/min to 5  C/min, respectively.

50

M. Singh and H. K. Daima

However, Xu et al. (2010) observed that their obtained cubic nanocrystals are not dependent on heating rate, as they obtained similar size or shape of the nanocrystals after 1.5, 10, 20, and 30 K/min. However, the size is increased from 6.2  1.9 nm to 12  1.4 nm in 1 and 3 h of refluxing time, and refluxing for a longer time i.e. 6 h, did not lead to further growth of nanocrystals, but the cubic shape of the nanocrystals is being damaged (Fig. 2.10). In terms of reflux time, Park et al. (2004) observed a negligible effect of it onto the nanoparticle size, where they obtain a monodisperse 12 nm nanoparticles after 10, 20, 30 min of reflux time. Similarly, Salas et al. (2012) also noticed that the increase in reflux time up to 4 h had a negligible effect on the nanoparticle size distribution. Chen et al.(Chen 2012) observed that refluxing time had little effect on the size of the nanoparticles but had a remarkable effect on their morphology. The thermal decomposition of iron oleate at 320  C in 1-octadecene, one can obtain nanoparticles of sizes 11.2, 11.6, 11.9, and 12.9 nm nanoparticles at reflux time of 30, 60, 90, 120 min, respectively. Kovalenko et al. (2007) confirmed that 30 min of reflux time is enough to obtain well shaped monodisperse nanoparticles and further extended growth rates would be accompanied by Ostwald ripening which broadens the size distribution and rounds the edges and corners of nanocrystals. Park et al. (Park et al. 2004) observed that when the iron oleate complex was aged in 1-octadecene at 260  C for 1 day, they produce polydisperse and poorly crystalline 9 nm nanoparticles, whereas after aging for 3 days generated monodisperse 12 nm nanoparticles. Similarly, aging at 240  C for 1 day, no nanoparticles were formed, whereas after 3 days of aging results in highly polydisperse nanoparticles of size ~14 nm, indicating the growth process is time dependent. However, when the iron oleate complex was aged at 200  C for 3 days, no nanoparticles were formed.

2.4 2.4.1

Structural and Magnetic Properties Nanoparticle Shape

Park et al. (2004) obtained spherical nanoparticles when using iron oleate and oleic acid using thermal decomposition procedure in 1-octadence at 320  C. Bronstein et al. (2007) obtained cubic nanoparticles using iron oleate and oleic acid using thermal decomposition procedure in 1-eicosene at 330  C in comparison to spherical nanoparticles in 1-octadecane at 318  C from the same iron oleate precursor, where the cubical shape of the nanocrystals is a result of a slower growth rate of the fcc facets as compared to all other facets. Xu et al. (2010) from experimental results, concluded that and of the spinel are more favourable for coordinating with halogens because the coordinating activity of Fe3+ is higher than that of noble metal atoms, while the lowered packing density enlarges the free surface space for halogen adsorption. Further notice that the of spinel is about 4.5-fold higher than the in packaging density, which probably results in the preferential adsorption of the and thus

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

51

Fig. 2.10 The refluxing time was varied for 1, 2, 3, and 6 h. It was found that the small cubic shaped iron oxide nano crystals were formed within 1 h (a). Refluxing for 2 and 3 h lead to a further growth of nano crystals and resulted in size-uniformed nanocubes (b and c). Over refluxing for 6 h did not show the size involution of nano crystals, but damages on the cubic shape (d). (e) The side length size distributions of iron oxide nano crystals obtained by refluxing 1, 2, and 3 h. (Adopted with permission from Xu et al. 2010)

cubic shaped nanocrystals are formed by exposing well-stabilised facets. Similarly, Chen (2012), consider that the formation of the cubic nanoparticles is attributed to the kinetically controlled growth of spherical nanoparticles along with the directions at low monomer concentration.

52

M. Singh and H. K. Daima

Fig. 2.11 (a) Resistance of the solution of the oleates of alkali metals in 1-octadecene. The concentration of the oleates is 0.015 M; (b) XPS spectra of the iron oxide nanoparticles prepared with additions of Na (top) and Cs (bottom) ions. Ratios Fe/Na ¼ 22.8 and Fe/Cs ¼ 5.8; (c) Iron oxide nanoparticles prepared with in situ prepared surfactants: tetraoctylammonium bromide (left) and sodium oleate (right). (Adopted with permission from Shavel and Liz-Marzan 2009)

Shavel and Liz-Marzan (2009) obtained cubic nanoparticles, in the presence of sodium oleate or sodium carbonate along with oleic acid using thermal decomposition of the iron oleate in squalene at 310–320  C. The most likely mechanism they propose is that sodium oleate conductivity drastically changes (about 3 orders of magnitude) at about 200  C due to their thermal dissociation, which involves the production of a certain amount of oleic acid anions in solution which plays an important role on shape control as shown in Fig. 2.11. They concluded from X-ray photoelectron spectroscopy, that the alkaline metal atoms get incorporated within the formed nanocubes i.e. sodium ions are present in the inner parts of the nanocubes as shown in Fig. 2.11b. They also obtained octahedrons in the presence of quaternary ammonium salts like tetraoctylammonium bromide along with oleic acid using thermal decomposition of the iron oleate in squalene at 310–320  C, where they believe that quaternary ammonium salts absorbed on outer facets of crystallographic plane of the iron oxide. They also observed that the quality of the nanocrystals obtained by “in-situ” preparation of the additives is worse as shown in Fig. 2.11c than that for nanocrystals prepared using pre-synthesized tetraoctylammonium bromide, probably because of the influence of water traces in the system.

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

53

Zhao et al. (2013) fabricate size-controlled octapod iron oxide nanoparticles by introducing the chloride anions (from sodium chloride or hexdecyl ammonium chloride or potassium chloride) during the thermal decomposition of the iron oleate complex, which exhibits ultrahigh transverse relaxivity value of 679  30 mM
1 s
1, thus making them much more effective T2 contrast agents in comparison with conventional iron oxide nanoparticles. On the other hand, they do not obtain octapods using either hexdecylammonium bromide or potassium bromide, thus revealing the role of chloride anions in their formation. From the energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy studies, they found the presence of a trace of chlorine on the octapod iron oxide nanoparticles and conclude that chloride ions were selectively bound to iron ions exposed on the high-index facets (probably ) of iron oxide during the particle growth, resulting in octapod shape of the nanocrystal. Kovalenko et al. (2007) obtained different nanocrystal shapes by using various oleic acid salts. They concluded from the conductivity measurements, that sodium oleate and potassium oleate dissociate into ions resulting in cubic nanocrystals whereas both oleic acid and dibutylammonium oleate remain in the molecular form giving the spherical shape to the nanocrystals. Wetterskog et al. (Erik et al. 2014; Wetterskog et al. 2013), observed that for the synthesis of spherical nanoparticles, oleic acid is needed, whereas, for the synthesis of cubic nanoparticles, a mixture of oleic acid and sodium oleate is needed. They believe that the presence of sodium oleate suppresses the surface growth rates for the facets or accelerates the growth of the facets, leading the cubic structure of the nanoparticles. On the other hand, Pichon et al. (2011), observe that cube shape is not preserved above a given maximum of the reaction temperature and Ostwald ripening is favoured around the corners of the cubes. To avoid this effect, it is better to reduce reaction time from 60 min to 15 min.

2.4.2

Nanoparticle Phase

The strength of the magnetic nanoparticle depends upon its crystallinity and its phase. From different iron oxide phases, magnetite and maghemite are ferromagnetic and are important in the biomedical applications, especially in the field of target drug delivery. However, these two phases are not easily distinguishable from the commonly used technique like XRD (X-ray powder diffraction), TEM (Transmission electron microscopy), etc. More than one complimentary technique is needed to quantify the exact phase of the nanoparticle formation like FTIR (Fourier-transform infrared spectroscopy), XPS (X-ray photoelectron spectroscopy), Raman spectroscopy, HRTEM (high resolution transmission electron microscopy), Mossbauer spectroscopy, etc. Bronstein et al. (2007) using X-ray powder diffraction and high resolution transmission electron microscopy, observed two phases in their nanoparticles obtained using thermal decomposition of the iron oleate i.e. ferrous oxide wustite

54

M. Singh and H. K. Daima

(Fe1-xO), where x can be between 0.05 and 0.17 along with spinel phase that could correspond to either maghemite (γFe2O3) or magnetite (Fe3O4). Hufschmid et al. (2015), confirmed through transmission electron microscopy and Raman spectroscopy that the obtained phase of their iron oxide from thermal decomposition of iron oleate in 1-octadecene is magnetite. By using Raman spectroscopy, the wustite phase detection is challengeable, where it can easily be laser-induced transformed into magnetite or hematite phase. At very low laser powers, the wustite phase has been reported at approximately 595 cm
1. Similarly, since the electron densities of all possible iron oxide-based compounds (FeO, Fe3O4, γFe2O3, FeOOH, etc.) are very similar, and standard transmission electron microscopy is not suited to distinguish these phases. Even the wustite and spinel phases cannot be differentiated using the fast fourier transform of high resolution transmission electron microscopy micrographs (Bronstein et al. 2007; Hufschmid et al. 2015; Pichon et al. 2011). Park et al. (2004) from the XAS (X-ray absorption spectroscopy) and XMCD (X-ray magnetic circular dichroism) results, conclude that the final phase of the iron oxide nanocrystals is in the form of (γFe2O3)1-x (Fe3O4)x, where the x ¼ 0.20, 0.57, 0.68, 0.86 and 1.00 for the 5, 9, 12, 16 and 22 nm nanocrystals, respectively. Thus, maghemite being the dominant phase for the 5 nm nanocrystals, and the proportion of the magnetite component gradually increases on increasing the nanoparticle size. It is worth mentioning here, that from their XRD results, it seemed that the final product is magnetite with a cubic spinel structure. However, their XAS and XMCD data reveal the core-shell structure of the obtained nanocrystals. Shavel and Liz-Marzan (2009) observed using HRTEM, core-shell structures, and island-like structures for the cubic nanoparticles. They correspond to the oxidation of the nanoparticle surface to be responsible for such structures which could be due to washing to be carried out in the air. Park et al. (2004), also observed the typical shell thickness as ca 3 nm which is enough for the oxidation of the nanoparticles less than 10 nm but allows to maintain the stable metallic core in nanocubes larger than 10 nm. Demortiere et al. (2011), obtained the core-shell structure, Fe3-xO4, with magnetite as the core and maghemite as the shell from the detailed XRD study of the lattice constant values with nanocrystal size, where the oxidation is strongly dependent upon the nanocrystal size i.e. it increases with decrease in nanocrystal size. Further, from the magnetic studies, they conclude that the surface influence in core-shell structure particles is predominant on the values of the magnetocrystalline anisotropy and magnetisation which describes the material net magnetic strength. Erik et al. 2014; Wetterskog et al. 2013, used rietveld refinements of synchrotron powder X-ray diffraction (PXRD) and elaborative TEM study, where they concluded to obtain the core-shell structure of the obtained product. They attributed this core-shell structure, because of reducing reaction environment, where the iron oleate upon thermal decomposition generates several by-product gases like carbon dioxide (CO2) and carbon monoxide (CO). At high temperatures, CO(g) reduces iron(III) resulting in nanoparticle compositions with varying oxidation states: Fe3O4; Fe1-xO, and Fe and in many cases the particles with a core-shell structure. Further, they

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

55

observe that purification and storage of nanoparticles in the presence of atmospheric oxygen causes smaller particles to oxidize relatively quickly into single-phase particles and eventually to transform completely to the maghemite phase. Similarly, Faure et al. (2013), observed that after thermal decomposition of iron oleate in 1-octadecene at 320  C, their product phase is maghemite. Xu et al. (2010), from the XRD and XPS study, also reveal that the obtained cubic nanocrystals via the thermal decomposition phase are a mixture of Fe3O4: γFe2O3, thus obtaining the core-shell structure of the nanocrystals. Bao et al. (2012), from the XRD and XPS analysis, confirmed that the phase of the nanorods formed in benzyl ether at various temperatures is maghemite. Johnson et al. (2012), from the Mossbauer spectroscopy, that the obtained nanoparticles through the thermal decomposition of the iron oleate according to Park et al. (2004) procedure, leads to maghemite phase, besides being partially oxidized to hematite (α-Fe2O3). Similar results are also obtained by Pichon et al. (2011), from the STEM (Scanning transmission electron microscopy)-HAADF (High-angle annular dark-field) and XRD evidence, where they conclude that such core-shell structures are due to the oxidation of the wustite phase into the spinel phase such as magnetite or maghemite and this transformation happens through an oxidation mechanism from the surface of the nanoparticle toward the core-shell interface. Although the exact stoichiometric relations for the formation of iron oxide nanoparticles via thermal decomposition is still not clear, especially when the product obtained is mixed phases of iron oxide (Song et al. 2013; Kwon et al. 2007; Hufschmid et al. 2015; Park et al. 2004; Hedi Mattoussi 2009). If magnetite is being one of the phases in the final product, then one thing is clear that Fe3+ ions are reduced to Fe2+ and which can only be possible if there are CO, H2, and/or Carbon produced during the thermal decomposition of the iron oleate complex. Kwon et al. (2007), from the thermogravimetric-mass spectrometric analysis (TG-MS) measurements, showed that the iron oleate complex was decomposed at around 320  C, reveal that CO2 and H2 are the gaseous products and no signals of water or CO were detected. As shown in Fig. 2.12a, b, the differential thermogravimetric (DTG) peak at 272  C (60.5 min) is assigned to oleic acid that is either free or weakly bound to Fe3+ ions. The second DTG peak at 316  C (71.5 min) matches very well with the CO2 peak (m/z ¼ 44) at 320  C (72.5 min) in Fig. 2.12b. Because CO2 is one of the major products of the thermal decomposition of metal carboxylates, the peak at around 320  C (72.5 min) can be assigned to the thermal decomposition of the iron oleate complex. Another decomposition product H2 (m/z ¼ 2) exhibited a peak at 320  C (76.3 min). Many other hydrocarbon fragments from the thermal decomposition with m/z values in the range of 40–150 also showed broad peaks at around 320  C (73 min). As a representative example of these fragments, the curve for m/z ¼ 97. On the other hand, Hai et al. (2010a, b) used commercial gas detectors to note down the nature and amount he gases to be produced. They observed that CO gas is doubled as a reason for reducing Fe3+ ions to Fe2+ ions, and the direct product of this reduction reaction, CO2 were detected, as shown in Fig. 2.13. They observed

56

M. Singh and H. K. Daima

Fig. 2.12 Thermal analysis data of the iron-oleate solution (a) and mass analysis data of the gas evolved from the solution during the thermal analysis (b) measured by TG-MS experiment. The ion current of each m/z value is proportional to the evolution rate of the corresponding compound. Eicosene was used as the solvent of the iron-oleate solution. (Adopted with permission from Kwon et al. 2007)

200 mmol of the total CO, which is very large compared to the 4 mmol CO required for the reduction of 4 mmol Fe3+ ions to Fe2+ ions, as well as to the maximum amount of CO (~15 mmol) generated when all (-COO-) bonds in 4 mmol iron oleate, 1.3 mmol sodium oleate, and 1.3 mmol oleic acids are assumed to be decomposed. On the other hand, the CO2 quantity is also detected very high, which cannot be a

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

57

Fig. 2.13 Concentrations of CO and CO2 were detected at various points of time and temperatures during the typical synthesis of nanocubes. The inset shows a diagram for detecting CO and CO2 by gas tube sensor. (Adopted with permission from Hai et al. 2010b)

product of only the reduction of Fe3+ ions by CO and/or the decomposition of oleic acid, sodium oleate, and iron oleate. Thus, the generation of CO and CO2 may be due mainly to the incomplete and/or complete combustion reaction of organic species, including solvent in the reactor under the given conditions, rather than only the thermolysis of oleic acid, iron oleate, and sodium oleate. The following equations describing the incomplete and complete combustion reactions of organic substances (Hai et al. 2010b):

58

M. Singh and H. K. Daima

  1 y y x þ
z O2 ! xCO þ H 2 O ðIncomplete combustion reactionÞ ð2:5Þ 2 2 2   y z y C x H y Oz þ x þ
O2 ! xCO2 þ H 2 O ðComplete combustion reactionÞ ð2:6Þ 4 2 2

C x H y Oz þ

This large reservoir of CO suggests that the formation of the ferrous wustite phase (FeO) is inherent in the decomposition of iron oleate complex. 3Fe2 O3 þ CO ! 2Fe3 O4 þ CO2

ð2:7Þ

Fe3 O4 þ CO ! 3FeO þ CO2

ð2:8Þ

Fe2 O3 þ CO ! 2FeO þ CO2

ð2:9Þ

Further, to observe the effect of CO on the phase of the nanoparticles, they perform the same experiment using eicosane (357  C) instead of 1-octadecene (315  C), where they obtain besides spinel phase i.e. Fe3O4 and/or γFe2O3 and FeO phases, α-Fe phase was also formed, which indicates that at high temperature, CO can reduce Fe3+ ions to Fe0 state instead of only Fe2+ state as at 315  C. Bronstein et al. (2007), observed that Wustite is normally formed in the situation of an insufficient amount of oxidizing species or oxygen. And since this phase is a metastable phase, under certain conditions, it can be transformed into the mixture of wustite, α-Fe, and magnetite, yet α-Fe tends to accumulate in the particle shell, where it is easily oxidized when the sample is exposed to air and can go undetected (Redl et al. 2004; Casula et al. 2006). Chen et al. (2009) also observed that solvents with a higher boiling point prompt the formation of larger nanoparticles, containing wustite as the major component, while those with a lower boiling point produce smaller nanoparticles with maghemite as the major component. Further, they obtained pure maghemite phase from the mixed wustite-magnetite composition by extending the reaction time or using an oxidizing agent, where initially wustite content decreases while the magnetite content increases which further oxidise to a stable pure maghemite phase. An overview of the chemical transformations in the FeO system, which results in the formation of core-shell particles (Wetterskog et al. 2013).

2.4.3

Nanoparticle Magnetism

From the previous sections, we observe that different parameters are responsible for obtaining the different morphologies and core-shell structures of the final iron oxide nanocrystals, but very few relate how these core-shell structures affect the net final magnetism of the nanocrystals, especially when there is a presence of non-magnetic core i.e. wustite within the oxidized magnetic shell (Johnson et al. 2012; Chen 2012; Park et al. 2004, 2007; Pichon et al. 2011; Xu et al. 2010). The partition of wustite and spinel phases inside nanoparticles is still debated, where such structures are

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

59

known to entail exchange anisotropy which results from exchange-bias coupling at the interface of both phases (Johnson et al. 2012; Pichon et al. 2011). Pichon et al. (2011), observed that cubic nanoparticles which consist of antiferromagnetic core (AFM) i.e. wustite with a ferrimagnetic (FIM) spinel layer results in hysteresis loop shift below the Neel temperature and an enhanced coercivity field compared to the usual single spinel phase nanoparticles, which is attributed to the exchange-bias coupling at the AFM/FIM interface, but some effects of stress may have to be considered. In comparison to cubic shape, they observed that spherical shape nanoparticles are ferromagnetic at temperatures below the blocking temperatures, which is in good agreement with single blocked domain in spinel structure nanoparticles as shown in Fig. 2.14a, b. The saturation magnetisation (Ms) is 50 emu/g for 12 nm average size spherical nanoparticles in comparison to 36.6 emu/g for the 16 nm average cubes at 300 K (Fig. 2.14c). Peacock et al. (2012) and Bloemen et al. (2012), obtain the Ms. of 53.50 and 20 emu/g of the spherical iron oxide nanoparticles of an average size of 8.0  1.5 nm and 9.3  1.6 nm at 300 K, respectively. Zhao et al. (2013), observed that for Ms. to be 67 emu/g and 55 emu/g for the 16 nm and 10 nm spherical iron oxide nanoparticles at 300 K, respectively. Similarly, they obtain Ms of 71 emu/g and 51 emu/g for the 30 nm and 20 nm octopods at 300 K. For the cubic crystals, Kovalenko et al. (2007), Ms of 29 emu/g for the 7 nm cubic iron oxide nanocrystals at 300 K. Demortiere et al. (2011), obtain the Ms 29 emu/g for the 2.5 nm nanocrystals in comparison to 77 emu/g for the 14 nm nanocrystals at 5 K, respectively. Similarly, Xu et al. (2010), obtained the Ms of approx. 42 emu/g is obtained for the 11.5  2.0 nm cubic iron oxide crystals at 300 K. On the other hand, Chen (2012) obtained the Ms. of 40, 49, and 56 emu/g for the nanoparticles of average sizes 12.5, 17.6, and 22.5 nm, respectively. Hence conclude that the contribution to the magnetism of the atom from the surface of the nanoparticles, at which magnetic moments have different orientations, is smaller than that from the inside. When the size of the nanoparticles increases, the relative portion number of the atoms on the surface will decrease. Thus, Ms. of the nanoparticles increases with increasing size. With blocking temperatures (TB), Park et al. (2004) observed that it increases from 40 K for 5 nm nanocrystal to 260 K for the 22 nm nanocrystals in the applied field of 100 Oe, respectively. On the contrary, the calculated magnetic anisotropy constant was found to increase with decreasing particle size. Similarly, Kovalenko et al. (2007) observed that the TB increases with the particle volume from 90 to 350 K, independently from the particle shape and the magnetic behaviour below TB shows pronounced shape dependence. Wetterskog et al. (2013), also observe that the effective anisotropy of nanocubes decreases as the degree of oxidation increases, where the influence of the strain contribution to the effective anisotropy could also be considered, although theoretical studies suggest that positively strained Fe3O4 exhibits a lower magnetocrystalline anisotropy than the unstrained one. Demortiere et al. (2011), observed that the TB increases continuously with the increase of the average nanocrystal size i.e. 10 K (2.5 nm), 18 K (3.5 nm), 22 K (5 nm), 36 K (9 nm),

60

M. Singh and H. K. Daima

Fig. 2.14 Magnetic measurements of spherically shaped NS12 (a) and cubic-shaped NC16 (b). Magnetization against temperature, ZFC-FC curves and difference between both curves (red) (a, b); (c) Magnetization curves against applied field at 300 K. The inset is the enlargement of the
2 to 2 kOe at 5 K for NS12. (Adopted with permission from Pichon et al. 2011)

61 K (11 nm) and 100 K (14 nm) in the applied field of 75 Oe, respectively as shown in Fig. 2.15. Recently, Johnson et al. (2012), obtain the TB of 300 K with deduced magnetic anisotropy of K as 0.52  104 J/m3 and TB of 120 K with K as 0.92x10
20 J/m3 for the spherical nanoparticles of average size 15 and 7.5 nm, respectively.

2.5

Biological Applications – The Importance of Phase Transfer

Due to biocompatible nature, magnetic nanoparticles are always being considered as one of the hot candidates for several biological applications as shown in Fig. 2.16 (Gao et al. 2009). They are considered as an alternate to the natural and conventional artificial enzyme in terms of low cost, stability, mass production with high enzymatic performance rates. The development of nanomaterials as next-generation artificial enzymes i.e. nanozymes started with the unexpected discovery of magnetite with peroxidase-like activities in 2007 (Gao et al. 2007).

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

61

Fig. 2.15 ZFC/FC curves (inset hysteresis loop recorded at 5 K) of the NCs with diameters 2.5 nm (a), 3.5 nm (b), 5 nm (c), 9 nm (d), 11 nm (e), and 14 nm (f). (Adopted with permission from Demortiere et al. 2011)

However, due to the presence of intrinsic magnetism, if not properly stabilised they tend to aggregate leading to loss of dispersibility and magnetisation (Wei et al. 2015). In terms of stabilisation their surface is being treated in a number of ways as shown in Fig. 2.17 (Gonzales and Krishnan 2007). In terms of the present thermal

62

M. Singh and H. K. Daima

Fig. 2.16 The scheme illustrates two strategies to fabricate multifunctional magnetic nanoparticles and their potential applications. (Adopted with permission from Gao et al. 2009)

Fig. 2.17 Typical morphologies of magnetic composite nanomaterials. Blue spheres represent magnetic iron oxide nanoparticles, and the non-magnetic entities and matrix materials are displayed in other colors. The nonmagnetic entity may provide the composite material with further functionalities and properties, providing multifunctional hybrid systems. (Adopted with permission from Wei et al. 2015)

decomposition methods although it offers good control over the nanoparticle size and shape distribution always comes with the final prints of an organic layer onto the nanoparticle surface, thus making them organic soluble. This possess a great challenge for the researchers to use them for the various biological applications where they need aqueous stabilised nanoparticles (Singh et al. 2018).

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

63

Fig. 2.18 Schematic representation of the phase transfer mechanism. (Adopted with permission from Xu et al. 2011)

Fig. 2.19 Schematic representation of the phase transfer mechanism. (Adopted with permission from Palma et al. 2015)

Several methods are being followed to make the thermal decomposition product water-soluble. These include silanisation, surfactant/polymer coatings, ligand exchange/modification, etc. (Vidal-Vidal et al. 2006). Like Gonzales and Krishnan (2007); Gonzales et al. (2010) achieve the aqueous dispersible iron oxide nanoparticles by the use of biocompatible copolymer pluronic F127 as a surfactant by exploiting their amphiphilic nature and study their cytotoxic nature. Xu et al. (2011) follows the selective ligand exchange mechanism where the oleic acid is being substituted by -COOH (poly(acrylic acid), -NH2 (polyethylenimine), -SH (glutathione) based surfactants as shown in Fig. 2.18. Susana Palma et al. (2015) employ citric acid (CA) or meso-2,3dimercaptosuccinic acid (DMSA) as ligand exchange surfactants and study in detail the effects of such phase transfer ligands as shown in Fig. 2.19. Firstly, they observe that both the ligands cause a bit of nanoparticle surface oxidation with citric acid

64

M. Singh and H. K. Daima

Fig. 2.20 Schematic representation of the phase transfer mechanism. (Adopted with permission from Cai et al. 2017)

more aggressive to the nanoparticle surface in comparison to meso-2,3dimercaptosuccinic acid. This oxidation lowers the saturation magnetisation and the initial susceptibility. Further, the use meso-2,3-dimercaptosuccinic acid modified magnetic nanoparticles for the covalent binding of the biopolymer gum Arabic either using cysteamine as a linker or directly as it is. Similarly, Chen et al. (2008) follow a double ligand exchange method with meso-2,3-dimercaptosuccinic acid as a surfactant. Momtazi et al. (2014) designed a targetable magnetic nanocarrier consisting of iron oxide nanoparticles as a core and biocompatible and biodegradable poly(sebacic anhydride)-block-methyl ether poly(ethylene glycol) (PSA-mPEG) as a polymer shell for cancer cell therapy. The in vitro cytotoxicity and cell viability were investigated, and the successful cellular uptake with no visible abnormalities were visualized by TEM. López-Cruz et al. (2009) covalently linked chitosan oligosaccharide (CSO) to the oleic acid-coated iron oxide nanoparticles via the surface ligand exchanged to a carboxylic acid silane make them highly stable in water, phosphatebuffered saline (PBS), Hank’s balanced salt solution (HBSS), and Dulbecco’s modified eagle’s medium (DMEM) with fetal bovine serum (FBS). Recently, Cai et al. (2017) successfully phase transferred the oleic acid coated iron oxide nanoparticles using reverse-micelle-based oxidative reaction as shown in Fig. 2.20. They are efficiently used as T2 contrast agents for magnetic resonance imaging (MRI) of CNE2 (nasopharyngeal carcinoma cell line) cells. Further, the free

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

65

carboxyl groups can act as conjugators for a variety of other molecules and find their usability in biological targeting or biological recognition applications. Patsula et al. (2016) successfully aqueous phase transferred the iron oxide nanoparticles via the surface modification with α-carboxyl-ω-bis(ethane-2,1-diyl) phosphonic acid-terminated poly(3-O-methacryloyl-α-D-glucopyranose) (PMG–P). The obtained nanoparticles have high relaxivity with low cellular uptake. Their cytotoxicity test was conducted using rat mesenchymal stem cells. They propose such a system being efficiently being used as contrast agents for magnetic resonance imaging. Fang et al. (2009) use a novel surface-engineering approach for the modification of the oleic acid capped iron oxide nanoparticles with triethoxysilylpropylsuccinic anhydride followed by a reaction with aminated poly (ethylene glycol) (PEG) to render the nanoparticles hydrophilic and display amine groups at the free termini of PEG chains. So, to make the iron oxide nanoparticles obtained from the thermal decomposition of the iron oleate, it looks that the surface treatment is one of the pre-requisite conditions. However, the choice selection in providing such surface treatment should depend on its overall effect onto its aqueous stability and net magnetism.

2.6

Conclusion

In a nutshell, the thermal decomposition route has several advantages over the other conventional methods used by the researchers in the synthesis of the iron oxide nanoparticles. Thanks to the chemical synthetic route which follows a strict LaMer diagram to obtain monodispersed nanoparticles. Secondly, one can obtain a variety of different shapes and sizes by altering the various synthetic conditions with ease. However, it does have some drawbacks like obtaining the single-phase purity; the complexity of the reactor design in conjugation with high temperature synthesis, and the phase transferred to aqueous medium for their use in biological applications.

References Ali A, AlSalhi MS, Atif M, Ansari Anees A, Israr MQ, Sadaf JR, Ahmed E, Nur O, Willander M (2013) Potentiometric urea biosensor utilizing nanobiocomposite of chitosan-iron oxide magnetic nanoparticles. J Phys Conf Ser 414(1):012024 Amara D, Margel S (2011) Solventless thermal decomposition of ferrocene as a new approach for the synthesis of porous superparamagnetic and ferromagnetic composite microspheres of narrow size distribution. J Mater Chem 21(39):15764–15772. https://doi.org/10.1039/ C1JM11842K Babes L, Denizot B, Tanguy G, Le Jeune JJ, Jallet P (1999) Synthesis of iron oxide nanoparticles used as MRI contrast agents: a parametric study. J Colloid Interf Sci 212(2):474–482. https:// doi.org/10.1006/jcis.1998.6053 Bao L, Low W-L, Jiang J, Ying JY (2012) Colloidal synthesis of magnetic nanorods with tunable aspect ratios. J Mater Chem 22(15):7117–7120. https://doi.org/10.1039/C2JM16401A

66

M. Singh and H. K. Daima

Bharde A, Rautaray D, Bansal V, Ahmad A, Sarkar I, Yusuf SM, Sanyal M, Sastry M (2006) Extracellular biosynthesis of magnetite using fungi. Small 2(1):135–141. https://doi.org/10. 1002/smll.200500180 Bloemen M, Brullot W, Luong TT, Geukens N, Gils A, Verbiest T (2012) Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications. J Nanopart Res 14(9):1100. https://doi.org/10.1007/s11051-012-1100-5 Bronstein LM, Huang X, Retrum J, Schmucker A, Pink M, Stein BD, Dragnea B (2007) Influence of iron oleate complex structure on iron oxide nanoparticle formation. Chem Mater 19 (15):3624–3632. https://doi.org/10.1021/cm062948j Cabrera L, Gutierrez S, Menendez N, Morales MP, Herrasti P (2008) Magnetite nanoparticles: electrochemical synthesis and characterization. Electrochim Acta 53(8):3436–3441. https://doi. org/10.1016/j.electacta.2007.12.006 Cai J, Miao YQ, Yu BZ, Ma P, Li L, Fan HM (2017) Large-scale, facile transfer of oleic acidstabilized iron oxide nanoparticles to the aqueous phase for biological applications. Langmuir 33(7):1662–1669. https://doi.org/10.1021/acs.langmuir.6b03360 Casula MF, Jun Y-w, Zaziski DJ, Chan EM, Corrias A, Alivisatos AP (2006) The concept of delayed nucleation in nanocrystal growth demonstrated for the case of Iron oxide nanodisks. J Am Chem Soc 128(5):1675–1682. https://doi.org/10.1021/ja056139x Chen Z (2012) Size and shape controllable synthesis of monodisperse iron oxide nanoparticles by thermal decomposition of iron oleate complex. Synth React Inorg Metal-Organic Nano-Metal Chem 42(7):1040–1046. https://doi.org/10.1080/15533174.2012.680126 Chen ZP, Zhang Y, Zhang S, Xia JG, Liu JW, Xu K, Gu N (2008) Preparation and characterization of water-soluble monodisperse magnetic iron oxide nanoparticles via surface double-exchange with DMSA. Colloids Surf A Physicochem Eng Asp 316(1):210–216. https://doi.org/10.1016/j. colsurfa.2007.09.017. Chen C-J, Lai H-Y, Lin C-C, Wang J-S, Chiang R-K (2009) Preparation of monodisperse iron oxide nanoparticles via the synthesis and decomposition of iron fatty acid complexes. Nanoscale Res Lett 4(11):1343–1350. https://doi.org/10.1007/s11671-009-9403-x Chen L, Han XX, Guo Z, Wang X, Ruan W, Song W, Zhao B, Ozaki Y (2012) Biomagnetic glass beads for protein separation and detection based on surface-enhanced Raman scattering. Anal Methods 4(6):1643–1647. https://doi.org/10.1039/C2AY25244A Cheng K, Shen D, Hensley MT, Middleton R, Sun B, Liu W, De Couto G, Marbán E (2014) Magnetic antibody-linked nanomatchmakers for therapeutic cell targeting. Nat Commun 5. https://doi.org/10.1038/ncomms5880 Demortiere A, Panissod P, Pichon BP, Pourroy G, Guillon D, Donnio B, Begin-Colin S (2011) Size-dependent properties of magnetic iron oxide nanocrystals. Nanoscale 3(1):225–232. https://doi.org/10.1039/C0NR00521E Ding X, Bao L, Jiang J, Hongwei G (2014) Colloidal synthesis of ultrathin [gamma]-Fe2O3 nanoplates. RSC Adv 4(18):9314–9320. https://doi.org/10.1039/C3RA46728G Erik W, Michael A, Arnaud M, Jekabs G, Dong W, Subhasis R, Anwar A, German S-A, Lennart B (2014) Precise control over shape and size of iron oxide nanocrystals suitable for assembly into ordered particle arrays. Sci Technol Adv Mater 15(5):055010 Fang C, Bhattarai N, Sun C, Zhang M (2009) Functionalized nanoparticles with long-term stability in biological media. Small 5(14):1637–1641. https://doi.org/10.1002/smll.200801647 Faure B, Wetterskog E, Gunnarsson K, Josten E, Hermann RP, Bruckel T, Andreasen JW, Meneau F, Meyer M, Lyubartsev A, Bergstrom L, Salazar-Alvarez G, Svedlindh P (2013) 2D to 3D crossover of the magnetic properties in ordered arrays of iron oxide nanocrystals. Nanoscale 5(3):953–960. https://doi.org/10.1039/C2NR33013J Gao L, Zhuang J, Nie L, Zhang J, Zhang Y, Gu N, Wang T, Feng J, Yang D, Perrett S, Yan X (2007) Intrinsic peroxidase-like activity of ferromagnetic nanoparticles. Nat Nanotechnol 2 (9):577–583. https://doi.org/10.1038/nnano.2007.260 Gao J, Gu H, Xu B (2009) Multifunctional magnetic nanoparticles: design, synthesis, and biomedical applications. Acc Chem Res 42(8):1097–1107. https://doi.org/10.1021/ar9000026

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

67

Gonzales M, Krishnan KM (2007) Phase transfer of highly monodisperse iron oxide nanocrystals with Pluronic F127 for biomedical applications. J Magn Magn Mater 311(1):59–62. https://doi. org/10.1016/j.jmmm.2006.10.1150 Gonzales M, Mitsumori LM, Kushleika JV, Rosenfeld ME, Krishnan KM (2010) Cytotoxicity of iron oxide nanoparticles made from the thermal decomposition of organometallics and aqueous phase transfer with Pluronic F127. Contrast Media Mol Imaging 5(5):286–293. https://doi.org/ 10.1002/cmmi.391 Hai HT, Kura H, Takahashi M, Ogawa T (2010a) Facile synthesis of Fe3O4 nanoparticles by reduction phase transformation from γ-Fe2O3 nanoparticles in organic solvent. J Colloid Interface Sci 341(1):194–199. https://doi.org/10.1016/j.jcis.2009.09.041. Hai HT, Yang HT, Kura H, Hasegawa D, Ogata Y, Takahashi M, Ogawa T (2010b) Size control and characterization of wustite (core)/spinel (shell) nanocubes obtained by decomposition of iron oleate complex. J Colloid Interface Sci 346(1):37–42. https://doi.org/10.1016/j.jcis.2010. 02.025. Hansen L, Larsen EKU, Nielsen EH, Iversen F, Liu Z, Thomsen K, Pedersen M, Skrydstrup T, Nielsen NC, Ploug M, Kjems J (2013) Targeting of peptide conjugated magnetic nanoparticles to urokinase plasminogen activator receptor (uPAR) expressing cells. Nanoscale 5 (17):8192–8201. https://doi.org/10.1039/C3NR32922D Haun JB, Yoon T-J, Lee H, Weissleder R (2010) Magnetic nanoparticle biosensors. Wiley Interdiscip Rev Nanomed Nanobiotechnol 2(3):291–304. https://doi.org/10.1002/wnan.84 Hedi Mattoussi JC (2009) Inorganic nanoprobes for biological sensing and imaging. Artech House, Norwood, p 2009 Hu M, Jiang J-S, Bu F-X, Cheng X-L, Lin C-C, Zeng Y (2012) Hierarchical magnetic iron (iii) oxides prepared by solid-state thermal decomposition of coordination polymers. RSC Adv 2 (11):4782–4786. https://doi.org/10.1039/C2RA01190E Hufschmid R, Arami H, Ferguson RM, Gonzales M, Teeman E, Brush LN, Browning ND, Krishnan KM (2015) Synthesis of phase-pure and monodisperse iron oxide nanoparticles by thermal decomposition. Nanoscale 7(25):11142–11154. https://doi.org/10.1039/C5NR01651G Johnson CE, Costa L, Gray S, Johnson JA, Krejci AJ, Hasan SA, Gonzalo-Juan I, Dickerson JH (2012) Mössbauer measurements on spinel-structure Iron oxide nanoparticles. In: Proceedings 36th annual condensed matter and materials meeting, Wagga Wagga, pp FO01:1–FO01:6 Kaushik A, Khan R, Solanki PR, Pandey P, Alam J, Ahmad S, Malhotra BD (2008) Iron oxide nanoparticles–chitosan composite based glucose biosensor. Biosens Bioelectron 24 (4):676–683. https://doi.org/10.1016/j.bios.2008.06.032. Kim DK, Zhang Y, Kehr J, Klason T, Bjelke B, Muhammed M (2001) Characterization and MRI study of surfactant-coated superparamagnetic nanoparticles administered into the rat brain. J Magn Magn Mater 225(1–2):256–261. https://doi.org/10.1016/S0304-8853(00)01255-5 Kobayashi T (2011) Cancer hyperthermia using magnetic nanoparticles. Biotechnol J 6 (11):1342–1347. https://doi.org/10.1002/biot.201100045 Kolosnjaj-Tabi J, Wilhelm C, Clément O, Gazeau F (2013) Cell labeling with magnetic nanoparticles: opportunity for magnetic cell imaging and cell manipulation. J Nanobiotechnol 11(Suppl 1):S7–S7. https://doi.org/10.1186/1477-3155-11-S1-S7 Kovalenko MV, Bodnarchuk MI, Lechner RT, Hesser G, Schäffler F, Heiss W (2007) Fatty acid salts as stabilizers in size- and shape-controlled nanocrystal synthesis: the case of inverse spinel iron oxide. J Am Chem Soc 129(20):6352–6353. https://doi.org/10.1021/ja0692478 Kwon SG, Piao Y, Park J, Angappane S, Jo Y, Hwang N-M, Park J-G, Hyeon T (2007) Kinetics of monodisperse iron oxide nanocrystal formation by “heating-up” process. J Am Chem Soc 129 (41):12571–12584. https://doi.org/10.1021/ja074633q Laurent S, Forge D, Port M, Roch A, Robic C, Elst LV, Muller RN (2008) Magnetic iron oxide nanoparticles: synthesis, stabilization, vectorization, physicochemical characterizations, and biological applications. Chem Rev 108(6):2064–2110. https://doi.org/10.1021/cr068445e Li L, Jiang W, Luo K, Song H, Lan F, Wu Y, Gu Z (2013) Superparamagnetic Iron oxide nanoparticles as MRI contrast agents for non-invasive stem cell labeling and tracking. Theranostics 3(8):595–615. https://doi.org/10.7150/thno.5366.

68

M. Singh and H. K. Daima

Liang X, Wang X, Zhuang J, Chen Y, Wang D, Li Y (2006) Synthesis of nearly monodisperse iron oxide and oxyhydroxide nanocrystals. Adv Funct Mater 16(14):1805–1813. https://doi.org/10. 1002/adfm.200500884 López-Cruz A, Barrera C, Calero-DdelC VL, Rinaldi C (2009) Water dispersible iron oxide nanoparticles coated with covalently linked chitosan. J Mater Chem 19(37):6870–6876. https://doi.org/10.1039/B908777J Lynch J, Zhuang J, Wang T, LaMontagne D, Wu H, Cao YC (2011) Gas-bubble effects on the formation of colloidal Iron oxide nanocrystals. J Am Chem Soc 133(32):12664–12674. https:// doi.org/10.1021/ja2032597 Martínez G, Malumbres A, Mallada R, Hueso JL, Irusta S, Bomatí-Miguel O, Santamaría J (2012) Use of a polyol liquid collection medium to obtain ultrasmall magnetic nanoparticles by laser pyrolysis. Nanotechnology 23(42):425605 Martinez-Boubeta C, Simeonidis K, Makridis A, Angelakeris M, Iglesias O, Guardia P, Cabot A, Yedra L, Estrade S, Peiro F, Saghi Z, Midgley PA, Conde-Leboran I, Serantes D, Baldomir D (2013) Learning from nature to improve the heat generation of Iron-oxide nanoparticles for magnetic hyperthermia applications. Sci Rep 3. https://doi.org/10.1038/srep01652. http://www. nature.com/srep/2013/130411/srep01652/abs/srep01652.html#supplementary-information Meng J, Xiao B, Zhang Y, Liu J, Xue H, Lei J, Kong H, Huang Y, Jin Z, Gu N, Xu H (2013) Superparamagnetic responsive nanofibrous scaffolds under static magnetic field enhance osteogenesis for bone repair in vivo. Sci Rep 3. https://doi.org/10.1038/srep02655. http://www.nature.com/ srep/2013/130913/srep02655/abs/srep02655.html#supplementary-information Momtazi L, Bagherifam S, Singh G, Hofgaard A, Hakkarainen M, Glomm WR, Roos N, Mælandsmo GM, Griffiths G, Nyström B (2014) Synthesis, characterization, and cellular uptake of magnetic nanocarriers for cancer drug delivery. J Colloid Interface Sci 433:76–85. https://doi. org/10.1016/j.jcis.2014.07.013. Nowicka AM, Kowalczyk A, Jarzebinska A, Donten M, Krysinski P, Stojek Z, Augustin E, Mazerska Z (2013) Progress in targeting tumor cells by using drug-magnetic nanoparticles conjugate. Biomacromolecules 14(3):828–833. https://doi.org/10.1021/bm301868f Okoli C, Boutonnet M, Mariey L, Järås S, Rajarao G (2011) Application of magnetic iron oxide nanoparticles prepared from microemulsions for protein purification. J Chem Technol Biotechnol 86(11):1386–1393. https://doi.org/10.1002/jctb.2704 Okoli C, Sanchez-Dominguez M, Boutonnet M, Järås S, Civera C, Solans C, Kuttuva GR (2012) Comparison and functionalization study of microemulsion-prepared magnetic Iron oxide nanoparticles. Langmuir 28(22):8479–8485. https://doi.org/10.1021/la300599q Palma SICJ, Marciello M, Carvalho A, Veintemillas-Verdaguer S, Morales M d P, Roque ACA (2015) Effects of phase transfer ligands on monodisperse iron oxide magnetic nanoparticles. J Colloid Interface Sci 437:147–155. https://doi.org/10.1016/j.jcis.2014.09.019 Park J, An K, Hwang Y, Park J-G, Noh H-J, Kim J-Y, Park J-H, Hwang N-M, Hyeon T (2004) Ultra-large-scale syntheses of monodisperse nanocrystals. Nat Mater 3(12):891–895. http:// www.nature.com/nmat/journal/v3/n12/suppinfo/nmat1251_S1.html Park H-Y, Schadt MJ, Wang IISL, Njoki PN, Kim SH, Jang M-Y, Luo J, Zhong C-J (2007) Fabrication of magnetic core@Shell Fe oxide@Au nanoparticles for interfacial bioactivity and bio-separation. Langmuir 23(17):9050–9056. https://doi.org/10.1021/la701305f Patsula V, Kosinová L, Lovrić M, Ferhatovic Hamzić L, Rabyk M, Konefal R, Paruzel A, Šlouf M, Herynek V, Gajović S, Horák D (2016) Superparamagnetic Fe3O4 nanoparticles: synthesis by thermal decomposition of iron(III) glucuronate and application in magnetic resonance imaging. ACS Appl Mater Interfaces 8(11):7238–7247. https://doi.org/10.1021/acsami.5b12720 Peacock AK, Cauet SI, Taylor A, Murray P, Williams SR, Weaver JVM, Adams DJ, Rosseinsky MJ (2012) Poly[2-(methacryloyloxy)ethylphosphorylcholine]-coated iron oxide nanoparticles: synthesis, colloidal stability and evaluation for stem cell labelling. Chem Commun 48 (75):9373–9375. https://doi.org/10.1039/C2CC34420C Pereira C, Pereira AM, Fernandes C, Rocha M, Mendes R, Fernández-García MP, Guedes A, Tavares PB, Grenèche J-M, Araújo JP, Freire C (2012) Superparamagnetic MFe2O4 (M ¼ Fe,

2 Thermal Decomposition Routes for Magnetic Nanoparticles: Development of. . .

69

Co, Mn) nanoparticles: tuning the particle size and magnetic properties through a novel one-step coprecipitation route. Chem Mater 24(8):1496–1504. https://doi.org/10.1021/cm300301c Pichon BP, Gerber O, Lefevre C, Florea I, Fleutot S, Baaziz W, Pauly M, Ohlmann M, Ulhaq C, Ersen O, Pierron-Bohnes V, Panissod P, Drillon M, Begin-Colin S (2011) Microstructural and magnetic investigations of Wüstite-spinel core-shell cubic-shaped nanoparticles. Chem Mater 23(11):2886–2900. https://doi.org/10.1021/cm2003319 Qi HZ, Yan B, Li CK, Lu W (2011) Synthesis and characterization of water-soluble magnetite nanocrystals via one-step sol-gel pathway. Sci China Phys Mech Astron 54(7):1239–1243. https://doi.org/10.1007/s11433-011-4375-0 Redl FX, Black CT, Papaefthymiou GC, Sandstrom RL, Yin M, Zeng H, Murray CB, O’Brien SP (2004) Magnetic, electronic, and structural characterization of nonstoichiometric iron oxides at the nanoscale. J Am Chem Soc 126(44):14583–14599. https://doi.org/10.1021/ja046808r Salas G, Casado C, Teran FJ, Miranda R, Serna CJ, Morales MP (2012) Controlled synthesis of uniform magnetite nanocrystals with high-quality properties for biomedical applications. J Mater Chem 22(39):21065–21075. https://doi.org/10.1039/C2JM34402E Salavati-Niasari M, Mahmoudi T, Amiri O (2012) Easy synthesis of magnetite nanocrystals via coprecipitation method. J Clust Sci 23(2):597–602. https://doi.org/10.1007/s10876-012-0451-5 Shavel A, Liz-Marzan LM (2009) Shape control of iron oxide nanoparticles. Phys Chem Chem Phys 11(19):3762–3766. https://doi.org/10.1039/B822733K Singh M, Ulbrich P, Prokopec V, Svoboda P, Šantavá E, Štěpánek F (2013a) Effect of hydrophobic coating on the magnetic anisotropy and radiofrequency heating of γ-Fe2O3 nanoparticles. J Magn Magn Mater 339(0):106–113. https://doi.org/10.1016/j.jmmm.2013.02.051 Singh M, Ulbrich P, Prokopec V, Svoboda P, Šantavá E, Štěpánek F (2013b) Vapour phase approach for iron oxide nanoparticle synthesis from solid precursors. J Solid State Chem 200 (0):150–156. https://doi.org/10.1016/j.jssc.2013.01.037 Singh M, Ramanathan R, Mayes ELH, Mašková S, Svoboda P, Bansal V (2018) One-pot synthesis of maghemite nanocrystals across aqueous and organic solvents for magnetic hyperthermia. Appl Mater Today 12:250–259. https://doi.org/10.1016/j.apmt.2018.06.003 Song N-N, Yang H-T, Ren X, Li Z-A, Luo Y, Shen J, Dai W, Zhang X-Q, Cheng Z-H (2013) Non-monotonic size change of monodisperse Fe3O4 nanoparticles in the scale-up synthesis. Nanoscale 5(7):2804–2810. https://doi.org/10.1039/C3NR33950E Sun X, Gutierrez A, Jose Yacaman M, Dong X, Jin S (2000) Investigations on magnetic properties and structure for carbon encapsulated nanoparticles of Fe, Co, Ni. Mat Sci Eng A 286 (1):157–160. https://doi.org/10.1016/S0921-5093(00)00628-6 Sun C, Lee JSH, Zhang M (2008) Magnetic nanoparticles in MR imaging and drug delivery. Adv Drug Deliv Rev 60(11):1252–1265. https://doi.org/10.1016/j.addr.2008.03.018. Sun X, Zheng C, Zhang F, Yang Y, Wu G, Yu A, Guan N (2009) Size-controlled synthesis of magnetite (Fe3O4) nanoparticles coated with glucose and gluconic acid from a single Fe(III) precursor by a sucrose bifunctional hydrothermal method. J Phys Chem C 113 (36):16002–16008. https://doi.org/10.1021/jp9038682 Sundaram PA, Augustine R, Kannan M (2012) Extracellular biosynthesis of iron oxide nanoparticles by Bacillus subtilis strains isolated from rhizosphere soil. Biotechnol Bioprocess Eng 17(4):835–840. https://doi.org/10.1007/s12257-011-0582-9 Vidal-Vidal J, Rivas J, López-Quintela MA (2006) Synthesis of monodisperse maghemite nanoparticles by the microemulsion method. Colloids Surf A Physicochem Eng Asp 288 (1):44–51. https://doi.org/10.1016/j.colsurfa.2006.04.027. Wang Y, Dostalek J, Knoll W (2011) Magnetic nanoparticle-enhanced biosensor based on gratingcoupled surface plasmon resonance. Anal Chem 83(16):6202–6207. https://doi.org/10.1021/ ac200751s Wang Y, Zhu Z, Xu F, Wei X (2012) One-pot reaction to synthesize superparamagnetic iron oxide nanoparticles by adding phenol as reducing agent and stabilizer. J Nanopart Res 14(4):1–7. https://doi.org/10.1007/s11051-012-0755-2

70

M. Singh and H. K. Daima

Wei W, Wu Z, Yu T, Jiang C, Kim W-S (2015) Recent progress on magnetic iron oxide nanoparticles: synthesis, surface functional strategies and biomedical applications. Sci Technol Adv Mater 16(2):023501 Weis C, Blank F, West A, Black G, Woodward RC, Carroll MRJ, Mainka A, Kartmann R, Brandl A, Bruns H, Hallam E, Shaw J, Murphy J, Teoh WY, Aifantis KE, Amal R, House M, Pierre TS, Fabry B (2014) Labeling of cancer cells with magnetic nanoparticles for magnetic resonance imaging. Magn Reson Med 71(5):1896–1905. https://doi.org/10.1002/mrm.24832 Wetterskog E, Tai C-W, Grins J, Bergström L, Salazar-Alvarez G (2013) Anomalous magnetic properties of nanoparticles arising from defect structures: topotaxial oxidation of Fe1–xO| Fe3
δO4 Core|shell nanocubes to single-phase particles. ACS Nano 7(8):7132–7144. https:// doi.org/10.1021/nn402487q Woo K, Hong J, Choi S, Lee H-W, Ahn J-P, Kim CS, Lee SW (2004) Easy synthesis and magnetic properties of iron oxide nanoparticles. Chem Mater 16(14):2814–2818. https://doi.org/10.1021/ cm049552x Xu Z, Shen C, Tian Y, Shi X, Gao HJ (2010) Organic phase synthesis of monodisperse iron oxide nanocrystals using iron chloride as precursor. Nanoscale 2(6):1027–1032. https://doi.org/10. 1039/B9NR00400A Xu Y, Qin Y, Palchoudhury S, Bao Y (2011) Water-soluble Iron oxide nanoparticles with high stability and selective surface functionality. Langmuir 27(14):8990–8997. https://doi.org/10. 1021/la201652h Xu H, Zeiger BW, Suslick KS (2013) Sonochemical synthesis of nanomaterials. Chem Soc Rev 42 (7):2555–2567. https://doi.org/10.1039/C2CS35282F You L-J, Xu S, Ma W-F, Li D, Zhang Y-T, Guo J, Hu JJ, Wang C-C (2012) Ultrafast hydrothermal synthesis of high quality magnetic core phenol–formaldehyde Shell composite microspheres using the microwave method. Langmuir 28(28):10565–10572. https://doi.org/10.1021/ la3023562 Zhao Z, Zhou Z, Bao J, Wang Z, Hu J, Chi X, Ni K, Wang R, Chen X, Chen Z, Gao J (2013) Octapod iron oxide nanoparticles as high-performance T2 contrast agents for magnetic resonance imaging. Nat Commun 4. https://doi.org/10.1038/ncomms3266

Chapter 3

Nanozymes: Emerging Nanomaterials to Detect Toxic Ions Xiangheng Niu, Xin Li, and Xuechao Xu

Abstract Since magnetic Fe3O4 nanoparticles were discovered to show intrinsic peroxidase-like catalytic activity in 2007, nanoscale materials with enzymemimicking characteristics (nanozymes) have attracted considerable interest from the academic and industrial communities. Unlike vulnerable natural enzymes that need complicated separation and purification processes at high cost, nanozymes with better robustness against harsh environments can be massively produced with lower cost. These merits have endowed them with promising applications in catalysis, sensing, biomedicine, and environmental engineering. Particularly, their catalytic properties can be easily tuned by foreign species like some ions, making it possible to employ them to design new methods for the determination of these species. In this book chapter, we aim at summarizing nanozymes used as emerging nanomaterials to detect toxic ions. Typically, detection of inorganic Hg2+, Ag+, arsenate/arsenite, Pb2+, [Cr2O7]2
, halide ions, phosphates and S-containing species based on the modulation of nanozyme activity is reviewed, and the underlying sensing mechanisms and strategies explored are comprehensively classified. Their opportunities and challenges in future toxic ion analysis for environmental monitoring are also discussed. Keywords Enzyme · Artificial enzyme · Nanozyme · Ion · Pollutant · Environmental analysis · Colorimetric assay · Fluorescent sensor · Catalytic activity · Catalytic system

X. Niu (*) · X. Li · X. Xu Institute of Green Chemistry and Chemical Technology, School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang, People’s Republic of China © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 H. K. Daima et al. (eds.), Nanozymes for Environmental Engineering, Environmental Chemistry for a Sustainable World 63, https://doi.org/10.1007/978-3-030-68230-9_3

71

72

3.1

X. Niu et al.

Introduction

As biological catalysts, natural enzymes show the ability to regulate the rates of various reactions with high efficiency and excellent substrate selectivity under mild conditions. Nonetheless, the promising use of these natural enzymes is seriously restricted by the shortcomings such as low stability and high cost. To overcome these deficiencies for wider applications, one has been trying to design and prepare artificial enzymes as cheap and stable substitutes to natural enzymes. As a consequence, lots of artificial chemicals with similar functions and/or structures to natural enzymes have been explored, including porphyrins, cyclodextrins, and supramolecules (Bjerre et al. 2008; Motherwell et al. 2001; Murakami et al. 1996). In recent decades, the emergence and boom of nanotechnology provide a great opportunity to fabricate functional materials with enzyme-mimicking features. Shortly after the amazing discovery of magnetic Fe3O4 nanoparticles exhibiting inherent peroxidase-like activity (Gao et al. 2007), numerous nanoscale materials, including noble metals (Zhang et al. 2018a; Lin et al. 2014), transition metal derivatives (Niu et al. 2016; He et al. 2018a; Xie et al. 2014; Li et al. 2018a) and carbon-based materials (Song et al. 2010; Sun et al. 2018), have been reported to have peroxidase-, oxidase-, catalase- or/and superoxide dismutase-like catalytic characteristics. These materials with enzyme-like properties are defined as ‘nanozymes’ (Wei and Wang 2013). Compared to biological enzymes, nanozymes show the attractive merits of easy large-scale production, low cost, favorable robustness against harsh environments, and good storage stability. These advantages have endowed them with extensive use in catalysis, biomedicine, sensing, and environmental engineering (Wang et al. 2016, 2018a; Huang et al. 2019a; Li et al. 2018b, 2019a; Liang and Yan 2019; Gao and Yan 2016; Gao et al. 2017; Wu et al. 2020). As a promising use, nanozymes are finding growing applications in environmental monitoring (Li et al. 2019a). Apart from the inherent physicochemical parameters (size, morphology, component, porosity, et al.) affecting the catalytic activities of nanozymes, some foreign ions are also able to directly tune the catalytic properties of some nanozymes or indirectly affect nanozyme-catalyzed systems, thus providing reliable strategies to detect these species. On the other hand, the combination of foreign recognition motifs (specific molecules, aptamers, antibodies, et al.) with nanozymes also enables the highly selective determination of targets. By using these principles, in the past few years one has established a few simple approaches to sense toxic ions (Fig. 3.1). Compared to other techniques available for the monitoring of toxic ions, nanozyme-based sensing systems have a main merit: nanozymes acting as labels can catalyze some reactions to offer amplified signals for high-sensitivity detection. In this book chapter, we intend to make a summary on the potential utilization of nanozymes in detecting toxic ions in environmental matrices. Table 3.1 summarizes typical sensing systems based on the modulation of nanozyme activity for the detection of toxic inorganic ions. The strategies developed using nanozymes as sensing elements for the determination of Hg2+, Ag+, arsenate/arsenite, Pb2+, [Cr2O7]2
, halide ions, phosphates, S-containing species and others are reviewed in detail. The underlying sensing mechanisms and strategies developed are

3 Nanozymes: Emerging Nanomaterials to Detect Toxic Ions

73

Fig. 3.1 Nanozyme-based sensing strategies for toxic ions

comprehensively summarized. The prospects, trends and challenges of nanozymes in future toxic ion detection for environmental analysis are discussed as well.

3.2

Detection of Hg2+ Using Nanozymes

Determination of Hg2+ is always a hot topic in the analytical chemistry community because of its hypertoxicity toward the environment and human health. Exposure to environments polluted by Hg2+ can make serious impacts on the nervous system and cause some diseases including kidney failure and acrodynia. Thus, it is of great importance to develop feasible methods and tools for the monitoring of toxic Hg2+. Up to today, one has explored several principles and strategies based on nanozymes to detect Hg2+ in environmental matrices.

3.2.1

Based on Target Promoted Activity

The potential enzyme-like catalytic activities of certain nanomaterials can be stimulated by Hg2+. Typically, Hg2+ is found to sharply enhance the peroxidasemimicking activity of nanoscale Au (Long et al. 2011; Sui et al. 2017; Ma et al. 2019; Wang et al. 2019; Zhang et al. 2015a; Jiang et al. 2018; Zhi et al. 2016). By using this principle, high-performance analysis of toxic Hg2+ can be done. For instance, Long and co-workers pioneeringly established a visual method for Hg2+

74

X. Niu et al.

Table 3.1 Typical sensing systems based on the modulation of nanozyme activity for the detection of toxic inorganic ions Nanozyme Au NPs

Target Hg2+

Pt NPs@UiO66-NH2

Hg2+

MnO2 nanorods

Hg2+

Cysteine-decorated Fe3O4

Hg2+

MVC-MOF

Hg2+

Pt NPs

Ag+

Histidinemodified Pd

Ag+

ZIF-8/GO nanosheets

Ag+

Dithiothreitolcapped Pd

Arsenite

Sensing principle Hg2+ stimulates the peroxidase-like activity of Au NPs Hg2+ inhibits the peroxidase-like activity of Pt NPs@UiO-66-NH2 Glutathione suppresses the oxidaselike MnO2 catalyzed chromogenic reaction, while Hg2 + recovers the reaction Hg2+ increases the peroxidase-like activity of cysteinedecorated Fe3O4 ssDNA suppresses the oxidase-like MVC-MOF catalyzed chromogenic reaction, while Hg2 + recovers the reaction Ag+ inhibits the oxidase-like activity of Pt NPs Ag+ inhibits the peroxidase-like activity of histidinemodified Pd Ag+ triggers the peroxidase-like activity of ZIF-8/ GO nanosheets Arsenite inhibits the oxidase-like activity of dithiothreitolcapped Pd via inducing reassembly

Linear range 1 ~ 600 nM

LOD 0.3 nM

References Long et al. (2011)

0 ~ 10 nM

0.35 nM

Li et al. (2017)

0.1 ~ 8 μM

0.08 μM

Yang et al. (2015)

0.02 ~ 90 nM

5.9 pM

Niu et al. (2019)

0.05 ~ 6 μM

10.5 nM

Wang et al. (2018b)

5 ~ 1000 nM

4 nM

Deng et al. (2019a)

30 ~ 300 nM

4.7 nM

Zhang et al. (2018b)

2 ~ 5 nM

1.43 nM

Li et al. (2019b)

0.033 ~ 333.3 μg/ L

35 ng/L

Xu et al. (2019a)

(continued)

3 Nanozymes: Emerging Nanomaterials to Detect Toxic Ions

75

Table 3.1 (continued) Nanozyme Glutathionecapped Au nanoclusters

Target Pb2+

Au@Hg

[Cr2O7]2


CeO2

F


VOx

I


Fe3O4 NPs

PO43


PdCu nanocorals

SCN


Cu nanoclusters

S2


Au NPs

Ce3+

CoOxH-GO

CN


Sensing principle Pb2+ binds to glutathione and induces the aggregation of glutathione-capped Au nanoclusters to provide enhanced peroxidase-like activity Au@Hg acts as an oxidoreductase mimic to catalyze the reaction between [Cr2O7]2
and TMB F
boosts the oxidase-like activity of CeO2 I
accelerates the peroxidase-like activity of VOx PO43
inhibits the peroxidase-like activity of Fe3O4 NPs SCN
inhibits the peroxidase-like activity of PdCu nanocorals S2
inhibits the peroxidase-like activity of Cu nanoclusters Ce3+ triggers the peroxidase-like activity of Au NPs CN
inhibits the peroxidase-like activity of CoOxH-GO

Linear range 2 ~ 250 μM

LOD 2 μM

References Liao et al. (2017)

1 ~ 2000 nM

0.71 nM

Zhang et al. (2018c)

Up to 100 μM

0.64 μM

Liu et al. (2016a)

3.3 nM ~ 33.3 μM

74 pM

Niu et al. (2017)

0.2 ~ 200 μM

0.11 μM

Chen et al. (2015)

1 nM ~ 100 μM

1 nM

He et al. (2018b)

0.5 ~ 20 μM

0.5 μM

Liao et al. (2018)

10 ~ 160 nM

2.2 nM

Deng et al. (2019b)

0.1 ~ 10 μM

0.1 μM

Lien et al. (2018)

determination based on the Hg2+-triggered peroxidase-mimicking activity of gold nanoparticles (AuNPs) (Long et al. 2011). They prepared AuNPs by employing sodium citrate as a reducing agent and stabilizer. As illustrated in Fig. 3.2a, the citrate-stabilized AuNPs have negligible ability to catalyze the oxidation reaction of 3,30 ,5,50 -tetramethylbenzidine (TMB) by H2O2; when a small amount of Hg2+ is added to the system, it will adsorb onto AuNPs and be reduced into Hg0 by the citrate modifier on them; the generated Hg0 is prone to form a gold amalgam with AuNPs and causes the change of the latter’s surface properties; as a result, the potential

76

X. Niu et al.

Fig. 3.2 (a) shows the target promoted peroxidase-like activity of AuNPs for Hg2+ analysis. (Reprinted with permission of the Royal Society of Chemistry from Ref. (Long et al. 2011)). (b) presents the inhibiting effect of Hg2+ on the peroxidase-mimicking activity of Pt NPs@UiO-66NH2 for Hg2+ detection. (Reprinted with permission of the American Chemical Society from Ref. (Li et al. 2017))

peroxidase-like activity of AuNPs is stimulated by the addition of Hg2+, leading to the significantly enhanced oxidation of colorless TMB to its corresponding product TMBox with a deep blue color. With the interesting finding, they determined Hg2+ in a linear scope of 1 ~ 600 nM, achieving a limit of detection (LOD) down to 0.3 nM. In addition to the positive effect of Hg2+ on Au-based nanozymes, Hg2+ is also able to accelerate the catalytic efficiencies of MoS2 (Lu et al. 2016), MoSe2 (Huang et al. 2019b), Ag (Wang et al. 2015) and Cu (Li et al. 2019c) via similar mechanisms. As a consequence, these findings have been utilized to fabricate platforms for the detection of Hg2+ as well. What should be mentioned here is that, although in these studies the Hg2+-triggered catalytic activities of nanozymes have been well verified and several techniques have been used to test the change of their surface chemistry, the underlying reason why the change can trigger their enzyme-like activities is still unclear. In other words, the factors affecting the enzyme-like properties of nanomaterials are still not fully supported by theoretical studies, which need more efforts to explain these findings for better design and use.

3 Nanozymes: Emerging Nanomaterials to Detect Toxic Ions

3.2.2

77

Based on Target Inhibited Activity

In contrast to the accelerating impact of Hg2+ on Au, it is observed that the enzymemimicking characteristics of Pt-based nanomaterials can be suppressed by the species (Li et al. 2015, 2017; Wu et al. 2014; Zhou and Ma 2017; Chen et al. 2016; Kora and Rastogi 2018). Xian’s group found that the addition of Hg2+ could sharply hinder the TMB + H2O2 reaction catalyzed by Pt nanoparticles encapsulated in a metal-organic framework (Pt NPs@UiO-66-NH2) (Li et al. 2017). As illustrated in Fig. 3.2b, the Pt NPs exposed on the surface of UiO-66-NH2 exhibit remarkable activity to trigger the TMB chromogenic reaction; with the presence of Hg2+, it can be chemically reduced into Hg0 by Pt atoms in the Pt NPs@UiO-66-NH2 hybrid (Wu et al. 2014), causing the decrease of the proportion of Pt0; since metallic Pt is the real active component, the decreased Pt0 caused by the addition of Hg2+ finally results in its reduced peroxidase-mimicking activity. With this principle, the LOD for Hg2+ analysis was determined to be 0.35 nM, much lower than its maximum concentration allowed in drinking water. Besides, Xiong et al. reported a nanozyme-based colorimetric sensor of Hg2+ based on the interaction of CuS particles and the target (Xiong et al. 2015). Given the extremely low Ksp (2  10
52) of HgS, the material rapidly precipitates Hg2+ once it is added, forming a layer of HgS on the nanozyme’s surface and covering its active sites for catalyzing the TMB oxidation process. This mechanism can be utilized for both the detection and removal of toxic Hg2+. Particularly, Zheng’s group found that Hg2+ was able to suppress the peroxidaselike activity of bovine serum albumin (BSA)-Au nanoclusters (Zhu et al. 2013), which was different from the phenomenon observed by Huang’s group (Long et al. 2011). They argued that the active sites of the material were Au+ on its surface and Hg2+ hindered its peroxidase-mimicking activity through the specific interaction between Au+ and Hg2+. As a matter of fact, more efforts are required to confirm the reported negative influence of Hg2+ on Au-based nanozymes. More importantly, the underlying reasons for Hg2+ inhibiting their catalytic activities should be further uncovered.

3.2.3

Based on Other Mechanisms

Apart from the direct interactions of Hg2+ with nanozymes, it can also make influences on some nanozyme-catalyzed systems. A typical example is that Hg2+ affects the nanozyme-catalyzed substrate oxidation with the presence of glutathione (GSH) (Yang et al. 2015; Christus et al. 2018a) or cysteine (Mohammadpour et al. 2014). Yang et al. used MnO2 nanorods as an oxidase mimic to catalyze the chromogenic oxidation reaction of TMB, and they found that GSH with certain reducing capacity could restore the blue TMBox product to colorless TMB again (Yang et al. 2015). Given the strong affinity of Hg2+ toward thiols, the

78

X. Niu et al.

pre-incubation of Hg2+ and GSH induced the recovery of the system to a blue color. Based on the ‘on-off-on’ process, monitoring of Hg2+ with favorable specificity was realized. Recently, our group proposed an ultrasensitive strategy for Hg2+ analysis on the basis of the target-triggered catalytic activity of cysteine-modified Fe3O4 particles (Cys-Fe3O4) (Niu et al. 2019). The as-synthesized material has barely peroxidaselike activity because of the excessive Cys modifier blocking the active sites of Fe3O4 particles. Once adding a trace amount of Hg2+, the Cys modifier can be despoiled off Fe3O4 particles due to the stronger Cys-Hg2+-Cys coordination, leading to the exposure of active Fe3O4 catalyzing the TMB chromogenic reaction. With this principle, the fabricated assay enabled the determination of Hg2+ with a LOD of 34 pM. It is well known that Hg2+ can specifically interact with thymine-rich DNA chains (Torigoe et al. 2010). Also, previous studies have revealed that DNA chains can make some impacts on the catalytic behaviors of nanozymes (Liu and Liu 2015; Wang et al. 2018c). Therefore, combining thymine-rich DNA chains with some nanozymes also provides a new route to sense Hg2+ with amplified signals (Wang et al. 2018b; Kim and Jurng 2013; Lien et al. 2019).

3.3

Detection of Ag+ Using Nanozymes

Silver plays important roles in the photography, electrical, and pharmaceutical industries. Also, it is intensively used for disinfection and sterilization. These applications have resulted in the environment seriously polluted by Ag+. In addition, the accumulation of silver in body can induce a disease called argyria. Thus, exploring methods to effectively monitor the species in various matrices turns to be very significant. At present, a few strategies based on the catalysis of nanozymes have been proposed for the determination of Ag+ (Deng et al. 2019a; Zhang et al. 2018b; Li et al. 2019b; Tang et al. 2018; Chang et al. 2016; Liu et al. 2016b).

3.3.1

Based on Target Inhibited Activity

Several investigations have confirmed that Ag+ can restrain the enzyme-like activities of Pt (Deng et al. 2019a; Tang et al. 2018) and Au (Chang et al. 2016; Liu et al. 2016b). In the Pt case, it is speculated that Pt2+ (4f145d8) on the Pt nanoparticles surface can combine Ag+ (4d10) via the d10-d8 interaction. As a result, the adsorption of Ag+ onto Pt can decrease the affinity toward substrates, eventually leading to the decrease in enzyme-like activity (Deng et al. 2019a). Also, the Ag+ species added can be chemically reduced into metallic Ag by common modifiers like citrate under the catalysis of Pt surface atoms, which further weakens the affinity of substrates toward Pt-based nanozymes (Tang et al. 2018). With respect to Au, metallic Ag

3 Nanozymes: Emerging Nanomaterials to Detect Toxic Ions

79

coming from the reduction of the Ag+ species is able to produce an Au-Ag hybrid with Au-based nanomaterials. The hybrid shows less affinity toward substrates and less catalytic activity compared to original Au. Similar to the Hg2+ case, the reason why the Ag-Au hybrid has less affinity toward substrates and less enzyme-like activity than monometallic Au still needs more studies to make it clear for better understanding and applications. Anyway, with the inhibiting impact of Ag+ on noble metals acting as nanozymes, simple and efficient sensing of Ag+ has been realized (Deng et al. 2019a; Tang et al. 2018; Chang et al. 2016; Liu et al. 2016b).

3.3.2

Based on Target Promoted Activity

Interestingly, Li et al. found that Ag+ could trigger the peroxidase-like catalytic activity of zeolitic imidazolate framework-8/graphene oxide (ZIF-8/GO) (Li et al. 2019b). They argued that when Ag+ was reduced into Ag0 by the citric acid-sodium citrate system, the formed Ag0 nanoparticles would disperse on the surface of ZIF-8/ GO, causing its surface chemistry to change. As a result, the promoted electron transfer facilitated the oxidation of TMB by H2O2. With the mechanism, the proposed sensing system enabled the detection of Ag+ with a LOD down to 1.43 nM, but it would be seriously interfered by Fe2+. Instead of the above direct interaction, our group proposed a facile assay for Ag+ analysis based on the histidine (His)-regulated enzyme-mimicking activity of Pd nanoparticles (Pd NPs) (Zhang et al. 2018b). As demonstrated by Fig. 3.3a, the TMB + H2O2 + His-Pd NPs system shows an obvious difference in absorbance with the absence or presence of Ag+. In detail, as illustrated in Fig. 3.3b, the modification of an appropriate amount of His on Pd NPs shows excellent mimetic activity to induce the oxidation of TMB to TMBox by H2O2. When Ag+ is in presence, it can despoil the His modifier from His-Pd NPs via the specific interaction between Ag+ and His, leading to bald Pd NPs. In comparison with bare Pd NPs, the His-Pd NPs material shows significantly improved catalytic activity due to the latter’s favorable

Fig. 3.3 (a) compares the UV-vis profiles of the His-Pd NPs catalyzed H2O2-TMB system with the absence or presence of Ag+, and (b) illustrates the underlying mechanism for Ag+ detection based on the nanozyme-catalyzed system. (Reprinted with permission of Elsevier from Ref. (Zhang et al. 2018b))

80

X. Niu et al.

physicochemical characteristics. What should be noted is that the amount of His decorated on Pd NPs affects the latter’s enzyme-like activity a lot. When an appropriate amount of His is used, it indeed promotes the activity (Fan et al. 2017). However, a negative impact is observed when excessive His is coated onto the nanozyme. This is because the overmuch modifier blocks the active sites of Pd NPs accessible to substrates. On the basis of the His-mediated process, linear detection of Ag+ in the range of 30 ~ 300 nM was gained with a LOD of 4.7 nM.

3.4

Detection of Arsenate/Arsenite Using Nanozymes

It is recognized that inorganic arsenic attracts much attention due to its hypertoxicity and carcinogenicity. Its maximum content is 10 μg/L (~0.13 μM) in drinking water guided by the World Health Organization (WHO). Inorganic arsenic mainly exists as highly toxic arsenite (As3+) and less toxic arsenate (As5+). For the determination of toxic inorganic arsenic, one has tried to explore several efficient and low-cost strategies using nanozymes. Both arsenite and arsenate can inhibit the catalytic features of some nanozymes (Christus et al. 2018b; Wen et al. 2019). For instance, Wen and co-workers found that CoOOH nanoflakes acting as a peroxidase-like nanozyme would bind arsenate via the As–O bond and electrostatic attraction, which would result in an activity suppression of the CoOOH (Wen et al. 2019). By employing 2,20 -azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as a peroxidase substrate and chromogenic agent, they built a colorimetric sensor of arsenate with a LOD as low as 3.72 ppb. Moreover, they removed the oxidized ABTS onto an electrode for electrochemical measurement, which provided a better sensitivity. A potential defect of this method is the use of H2O2. Although arsenite cannot lead to the change of the nanozyme’s activity directly, it can be oxidized into arsenate by H2O2. Therefore, their method cannot be utilized to accurately determine and differentiate arsenite and arsenate in practical samples. Besides, the method is seriously interfered by PO43
, because PO43
can also bind to the nanozyme through the P–O bond. As a result, an appropriate reagent like CaCl2 is required to entirely mask the impact of PO43
prior to the measurement of arsenate. Recently, we reported a colorimetric approach for arsenite determination based on the 3-mercaptopropionic acid (3-MPA)-assisted active site and interlayer channel dual-masking of oxidase-like FeCo-layered double hydroxide (FeCo-LDH) (Xu et al. 2019b). The FeCo-LDH shows high oxidase-mimicking activity to catalyze the oxidation of colorless TMB to TMBox with a blue color. With the presence of 3-MPA, arsenite can anchor onto the Fe* sites by forming a robust Fe– AsIII–3-MPA–AsIII–Fe structure, masking both the active sites and interlayer channels of FeCo-LDH for catalysis. According to this rule, a limit of detection as low as 35 nM was gained for the determination of arsenite. In addition, the 3-MPA-assisted method could effectively exclude the possible interferences from arsenate, Hg2+ and Pb2+.

3 Nanozymes: Emerging Nanomaterials to Detect Toxic Ions

81

Fig. 3.4 Scheme of the re-assembly-triggered oxidase-like activity suppression of Pd-DTT for the determination of arsenite. (Reprinted with permission of Elsevier from Ref. (Xu et al. 2019a))

In our another work, a colorimetric sensor of toxic arsenite was established according to the reassembly-triggered oxidase-like activity suppression of dithiothreitol (DTT)-decorated Pd nanoparticles (Pd-DTT) (Xu et al. 2019a). As presented in Fig. 3.4, the Pd-DTT nanozyme provides good oxidase-like activity to trigger the TMB chromogenic reaction. When arsenite is added, it chelates the sulfydryl groups in DTT and induces a re-assembly process of the material. Compared to original nanozyme, the re-assembled one shows less activity to catalyze the chromogenic reaction. On the basis of the finding, arsenite in a wide linear range and with a low LOD (35 ng/L) was monitored. With the aid of ethylene diamine tetraacetic acid (EDTA) as a chelating agent, the assay also exhibited good selectivity for the analysis of arsenite against other ions. As a matter of fact, the use of masking agents not only complicates the operation but also may bring some unrevealed effects. Thus, exploring reliable nanozyme-based strategies where no foreign agents are needed for the specific determination of arsenite and arsenate is still welcome.

3.5

Detection of Pb2+ Using Nanozymes

Pb is another heavy metal that poses high toxicity and great threat to the environment and human health. As for the determination of Pb2+, Liao et al. provided a simple colorimetric sensing mean according to the target-triggered aggregation of gold nanoclusters (AuNCs) with better peroxidase-like activity (Liao et al. 2017). In their report, GSH was employed as a reducing agent and stabilizer to synthesize AuNCs. As shown in Fig. 3.5, GSH decorated on the AuNCs surface can lead to the aggregation of the nanozyme via the interaction of Pb2+ and GSH. The aggregated material shows significantly improved activity than original AuNCs to induce the TMB color reaction. Thus, Pb2+ in the scope of 2 ~ 250 μM was determined linearly, giving a LOD of 2 μM. Surprisingly, in their sensing system no obvious interferences from Hg2+ and Ag+ were found.

82

X. Niu et al.

Fig. 3.5 Schematic illustration of the Pb2+-promoted oxidation of TMB by H2O2 under the peroxidase-like catalysis of AuNCs. (Reprinted with permission of the Royal Society of Chemistry from Ref. (Liao et al. 2017))

Fig. 3.6 Schematic illustration for the oxidoreductase-mimicking activity of Au@Hg for the sensing of [Cr2O7]2
. (Reprinted with permission of the American Chemical Society from Ref. (Zhang et al. 2018c))

3.6

Detection of [Cr2O7]22 Using Nanozymes

Cr exists in the environment as Cr(III) and Cr(VI). Cr(VI) is widely considered as a toxic species, while Cr(III) is believed to be less toxic. As for the analysis of [Cr2O7]2
using nanozymes, Lu’s group proposed a catalysis-based route based on the oxidoreductase-like activity of Au@Hg (Zhang et al. 2018c). They argued that the Au@Hg material exhibited oxidoreductase-mimicking activity to catalyze [Cr2O7]2
oxidizing the TMB substrate (Fig. 3.6), giving a blue color as the indicator of [Cr2O7]2
. Although they carried out a series of control experiments

3 Nanozymes: Emerging Nanomaterials to Detect Toxic Ions

83

to verify the oxidoreductase-like features of Au@Hg, more proofs to uncover the catalytic process are still needed. Besides, toxic Hg is used in their method, which shades the highlights of the strategy to some extent. Similarly, Borthakur et al. found that CuS-decorated reduced graphene oxide (CuS-rGO) could efficiently catalyze the decomposition of H2O2 to hydroxyl radicals in the presence of [Cr2O7]2
(Borthakur et al. 2019). By using the generated radicals to trigger the fluorogenic reaction of terephthalic acid, they fabricated a fluorescent platform for the determination of [Cr2O7]2
in aqueous media. Their proposed method could be used to detect toxic [Cr2O7]2
at a concentration down to 26.6 nM. In addition, the CuS-rGO hybrid offered 99% photocatalytic efficiency for the rapid reduction of highly toxic Cr(VI) to less toxic Cr(III) under a natural sunlight irradiation.

3.7

Detection of Halide Ions Using Nanozymes

Halide ions are common species found in various matrices, and some of them are considered as potential pollutants. For instance, fluoride (F
) in drinking water within an appropriate concentration range is favorable for human health, but when its level is beyond the scope, long-term drinking of water contaminated by high-level F
can lead to a disease called fluorosis. In 2016, Liu and co-workers found that F
could stimulate the oxidasemimicking activity of CeO2 (Liu et al. 2016a). As compared in Fig. 3.7a, when using ABTS as a substrate, the as-synthesized CeO2 nanoparticles show negligible oxidase-like catalytic activity, while in the presence of F
the material is triggered to catalyze the ABTS chromogenic process remarkably. In their study, the roles of F
in accelerating the color reaction were speculated. As illustrated in Fig. 3.7b, on the one hand, the negatively charged F
species can change the surface charge of CeO2 to adjust the substrate adsorption affinity. On the other hand, it promotes the electron

Fig. 3.7 (a) shows that F
can promote the oxidase-like activity of CeO2 catalyzing the oxidation of ABTS, and (b) illustrates the multiple effects of F
on the CeO2 nanozyme. (Reprinted with permission of the Royal Society of Chemistry from Ref. (Liu et al. 2016a))

84

X. Niu et al.

transfer between O2 and ABTS through the CeO2 mediator. Besides, the presence of F
on the nanozyme’s surface prevents the inhibiting effect from the oxidized ABTS product. With the interesting finding, high-performance colorimetric analysis of F
was achieved by them. Subsequently, they expanded the principle to detect F
fluorescently (Li et al. 2019d). We observed that I
could dramatically promote the peroxidase-like activity of VOx (Niu et al. 2017). The nanozyme showed quite low catalytic efficiency toward the TMB color reaction when trace VOx was utilized. It was found that a small content of I
(3.3 μM) was able to significantly improve the nanozyme’s activity and catalytic efficiency. X-ray photoelectron spectroscopy (XPS) and Zeta potential measurements verified that I
could adjust the surface charge of the VOx material and modulate its electronic structure. Considering the positive impact of I
, we achieved the highly sensitive determination of the target with a LOD as low as 74 pM. Interestingly, Guo’s group studied the different impacts of halide ions (F
, Cl
,
Br and I
) on the peroxidase-like activity of β-casein-modified gold nanoparticles (CM-AuNPs) in detail (Liu et al. 2017). Given the different Au–X (X represents halide ions) interactions to block active sites, they show various influences on the catalytic activity of CM-AuNPs. In detail, I
can rapidly inhibit the activity of the nanozyme irreversibly. Similar to I
, Br
is also able to hinder the nanozyme’s activity, but the behavior is reversible. Given the weak Au–Cl interaction, Cl
at a high level shows very weak influence on the catalytic activity of CM-AuNPs, while F
has no impact because of the absence of the Au–F interaction. Theoretically, these findings can be employed to quantify and differentiate halide ions.

3.8

Detection of Phosphates Using Nanozymes

Phosphates are inorganic anions widely distributed in stream and underground water. Due to unrestricted industrial waste, agricultural discharge and household sewage runoff, they have been common pollutants in environmental matrices. As a significant part in the nutritional chain of aquatic microorganisms, phosphates are usually considered as an index of eutrophication pollution. In this regard, developing efficient methods and devices to monitor phosphates is of great importance. With the catalysis of nanozymes and the potential effects of phosphates on some nanozymes, sensing of phosphate ion (Pi) (Chen et al. 2015; Li et al. 2019e) and pyrophosphate ion (PPi) (Xia et al. 2019; Xu et al. 2019c) has been realized. Yang’s group found that Pi would adsorb onto the surface of Fe3O4 nanoparticles via the coordination with Fe3+ and further suppress the latter’s peroxidase-mimicking activity (Chen et al. 2015). With the mechanism, a facile protocol was proposed for the colorimetric analysis of Pi. To enhance the method’s analytical performance, our group proposed an enhanced Pi assay by utilizing Zr(IV) to synergistically inhibit the peroxidase-like catalytic activity of cubic Fe3O4 (Li et al. 2019e). As illustrated in Fig. 3.8, after the modification of 3,4-dihydroxyhydrocinnamic acid

3 Nanozymes: Emerging Nanomaterials to Detect Toxic Ions

85

Fig. 3.8 Scheme of the Zr4+-mediated peroxidase-like activity suppression of Fe3O4-DHCA for the determination of PO43
. (Reprinted with permission of Elsevier from Ref. (Li et al. 2019e))

(DHCA), cubic Fe3O4 particles turn to be more hydrophilic, resulting in the hybrid (Fe3O4-DHCA) with improved capacity to induce the catalytic oxidation of colorless TMB to blue TMBox; due to the intrinsic electrostatic interaction, it is very easy for Zr4+ to adsorb onto the surface of the negatively charged nanozyme; if Pi is further added, it will interact with Zr4+ strongly and generate a coating layer on the nanozyme surface, greatly inhibiting its catalytic activity; as a consequence, the TMB chromogenic process is sharply reduced when Pi exists in the system. Compared to the direct interaction of Pi and Fe3O4, the participation of Zr4+ intensifies the negative impact of Pi on the Fe3O4-DHCA nanozyme, providing a wider linear scope and a lower LOD. What should be stated is that the proposed method needs multiple additions of Zr4+ and the analyte. To simplify the operation, development of novel nanozymes integrating the catalytic function with strong Zr4+ recognition sites is still highly desired. For the determination of PPi, Xia et al. fabricated a nanozyme-based colorimetric system based on the aggregation/dispersion-mediated peroxidase-mimicking activity of MoS2 quantum dots (QDs) (Xia et al. 2019). They found that the as-prepared MoS2 QDs had no intrinsic catalytic activity. When a certain amount of Fe3+ was added, MoS2 QDs would aggregate together as verified by atomic force microscopy (AFM). Interestingly, the aggregated QDs could exhibit impressed peroxidase-like capacity to trigger the TMB chromogenic reaction. Given PPi could strongly coordinate with the Fe3+ species, the presence of PPi would reduce the aggregation of QDs. With the aggregation/dispersion-mediated adjustment of MoS2 QDs, highly sensitive and selective analysis of PPi has been gained. However, the reason for the stimulated peroxidase-like activity of aggregated MoS2 QDs compared to dispersed ones is still unclear. It is believed that, once the underlying mechanism is fully uncovered, the controllable aggregation and dispersion of QDs acting as potential nanozymes will be a general strategy for more sensing applications. Instead, our group developed an efficient sensor for PPi detection according to the formation of fluorescent polydopamine (PDA) catalyzed by peroxidase-like FeCo-LDH, the quenching effect of Fe3+ on PDA, and the strong interaction of PPi and Fe3+ (Xu et al. 2019c).

86

3.9

X. Niu et al.

Detection of S-containing Species Using Nanozymes

S-containing ions are common substances derived from various industrial processes including photofinishing, textile dyeing, and electroplating. Besides, vehicle exhaust also makes a great contribution to the pollution of S-containing species. Given their high toxicity and the corresponding risks associated with exposure, determination of S-containing ions has gained a lot of attention in the environmental analytical community. With the aid of the suppressing effect on certain nanozymes, S-containing ions can be analyzed conveniently and efficiently (He et al. 2018b; Liao et al. 2018; Peng et al. 2017). For instance, Liao and co-workers developed a sulfide (S2
) assay based on the target-inhibited peroxidase-mimicking activity of copper nanoclusters (CuNCs) (Liao et al. 2018). The as-synthesized CuNCs exhibited high activity catalyzing the oxidation of colorless TMB by H2O2 to blue TMBox, triggering a remarkable chromogenic reaction that gave a large absorbance at 652 nm. The absorbance was significantly reduced when a ppm-level amount of S2
was added to the system. They speculated that S2
was attached onto the CuNCs surface through the interaction between the target and Cu(I) in the CuNCs structure, resulting in the reduced catalytic activity of the latter toward TMB (Fig. 3.9). With the principle, the LOD for S2
was determined to be 0.5 μM, lower than the level in drinking water guided by the WHO. Due to the very strong interaction of Cu(I) and S2
(the pKsp of Cu2S is as high as 47.6), their method can be used to selectively sense the S2
species without obvious effects from other common anions. However, some reducing anions like ascorbate potentially disturb the sensing system, which will be a major limitation of the proposed method. Similar to S2
, thiocyanate (SCN
) can also tune the catalytic properties of some nanozymes, making it possible to utilize nanozymes to sense the species. Our group achieved the high-performance determination of SCN
by employing PdCu nanocorals as a sensing element (He et al. 2018b). In comparison with

Fig. 3.9 Scheme of the target-inhibited peroxidase-like activity of CuNCs for S2
detection. (Reprinted with permission of Springer Nature from Ref. (Liao et al. 2018))

3 Nanozymes: Emerging Nanomaterials to Detect Toxic Ions

87

nanostructured Pd, the bimetallic PdCu material prepared by a microwave-assisted reduction procedure was found to show improved catalytic activity toward the TMB color reaction with the presence of H2O2. Due to the strong binding interaction of SCN
and Pd atoms, the former could adsorb onto the PdCu surface, leading to the inhibition of the chromogenic reaction. With this strategy, a very wide linear range (1 nM ~ 100 μM) of the analyte was determined, providing a LOD down to 1 nM. As for selectivity, little effects from common ions (except Cl
) with a 50-fold concentration of SCN
were observed. The Cl
species with a high level would poison the Pd-based catalyst, thus making certain impact on the detection of SCN
. Also, a similar strategy for SCN
sensing was proposed by using Au@Pt as a peroxidase mimic (Peng et al. 2017).

3.10

Detection of Other Ions Using Nanozymes

Apart from the above applications, several nanozyme-based platforms have been fabricated to detect other ions. For instance, Lien and co-workers found that the peroxidase-mimicking activity of cobalt hydroxide/oxide-modified graphene oxide (CoOxH-GO) would be suppressed by cyanide ions (CN
) (Lien et al. 2018). They argued that the strong affinity of CN
toward Co2+ in the nanozyme led to the formation of a Co(II)-cyanide complex, and the complex might hinder the electron transfer from the nanozyme to substrates, resulting in the decrease in activity. With this finding, they proposed a membrane-based nanozyme assay for the fluorescent detection of CN
. Khashab’s group reported a peroxidase mimetic method for uranyl (UO22+) determination based on the target-inhibited activity of BSA-protected AuNCs (Zhang et al. 2015b). In their study, the analyte could interact with the BSA modifier on AuNCs and induce the aggregation of active AuNCs, eventually changing the material’s peroxidase-like catalytic activity. However, this interaction would be seriously influenced by Hg2+ and Ag+, because the two species could also interact with the BSA modifier through some hydroxyl groups. Thus, an appropriate masking reagent was required to mask them for the selective analysis of UO22+. Recently, Chen’s group studied the influences of rare-earth elements on the peroxidase-like activity of bare gold nanoparticles (GNPs), and they further fabricated a colorimetric assay of Ce3+ based on the target-activated peroxidase mimetic activity (Deng et al. 2019b). They argued that the Ce3+ species could bind to the bare GNPs surface through the electrostatic attraction, after which it donated its electrons to the nanozyme. With the catalyzed TMB chromogenic reaction, their assay could provide a LOD down to 2.2 nM for the sensing of Ce3+. Since other rare-earth elements, common metal ions and inorganic anions show no obvious effects, the method exhibited excellent selectivity for Ce3+ detection.

88

3.11

X. Niu et al.

Trends and Challenges

Based on the above summary, the past few years have witnessed the active development of sensors and biosensors utilizing nanomaterials with enzyme-like catalytic activities for the analysis of toxic inorganic ions. Although the above applications achieved by nanozymes, there is still plenty of space to advance the community: (1) at present, the type of targets detected by nanozymes is still very limited. It is believed that establishing novel nanozyme-based sensing principles and strategies for more pollutants will be a hot topic in the near future; (2) although the activities of a few nanozymes are reported to be tuned selectively by a certain metal ion, most of currently developed nanozymes may be directly affected by multiple ions simultaneously. When these ions are present together, it is hard to use the nanozyme-based sensing system to selectively detect a targeted ion. How to establish sensing systems with better selectivity is still a great challenge in this community; (3) for some nanozyme-based sensing systems mentioned above, the fundamental mechanism and principle are still not very clear. Besides, a lot of factors, such as dispersion state of nanozymes, organic molecules modified on nanozyme surface, and charged state of nanozymes, will affect the interaction between the nanozyme and the targeted ion. Revealing the nature of the interaction between the surface molecules on nanozymes and the targeted ion and further uncovering the recognition process will be very helpful for designing better nanozyme-based sensing systems; (4) currently, most of nanozyme-based analyses of pollutants relies on colorimetric detection. Although the colorimetric paradigm shows simple signal reading, its relatively poor sensitivity restricts its wide use. Expanding other sensing paradigms to satisfy various demands will bring nanozymes a better future in environmental monitoring; (5) the toxicity of nanozymes themselves should not be neglected when they are applied in environmental monitoring. Developing environmentally friendly and recyclable nanozymes for pollutant analysis is highly desired.

3.12

Conclusions

In this book chapter, we have attempted to present an overview of nanozymes used as emerging nanomaterials to sense toxic inorganic ions. The principles and platforms developed for the determination of typical ionic pollutants, including Hg2+, Ag+, arsenate/arsenite, Pb2+, [Cr2O7]2
, halide ions, and phosphates, have been discussed. Thanks to the nature of catalysis, nanozymes acting as sensing elements are able to provide amplified signals for high-sensitivity detection. With the specific interactions between targets and certain nanozymes or by combining foreign recognition elements (specific molecules, aptamers, antibodies, et al.) with nanozymes, highly specific determination of analytes can be achieved. Besides, nanozymes are easy to be obtained and show favorable stability, both of which give them a promising prospect in environmental analysis. We believe that nanoscale materials

3 Nanozymes: Emerging Nanomaterials to Detect Toxic Ions

89

with enzyme-like catalytic characteristics will find intensive applications in the environmental monitoring field. Acknowledgements The authors appreciate the supports from the National Natural Science Foundation of China (No. 21605061), the Natural Science Foundation of Jiangsu Province (No. BK20160489), the Open Fund from the Key Laboratory of Luminescence and Real-Time Analytical Chemistry of Ministry of Education (No. 201814), the Open Fund from the Shanghai Key Laboratory of Functional Materials Chemistry (No. SKLFMC201601), the Open Fund from the State Key Laboratory of Bioreactor Engineering, and the Cultivation Project for Excellent Young Teachers of Jiangsu University (No. 4111310004).

References Bjerre J, Rousseau C, Marinescu L, Bols M (2008) Artificial enzymes, “Chemzymes”: current state and perspectives. Appl Microbiol Biotechnol 81:1–11 Borthakur P, Das MR, Szunerits S, Boukherroub R (2019) CuS decorated functionalized reduced graphene oxide: a dual responsive nanozyme for selective detection and photoreduction of Cr (VI) in aqueous medium. ACS Sustain Chem Eng 7:16131–16143 Chang YQ, Zhang Z, Hao JH, Yang WS, Tang JL (2016) BSA-stabilized Au clusters as peroxidase mimetic for colorimetricdetection of Ag+. Sens. Actuators B Chem. 232:692–697 Chen CX, Lu LX, Zheng Y, Zhao D, Yang F, Yang XR (2015) A new colorimetric protocol for selective detection of phosphate based on the inhibition of peroxidase-like activity of magnetite nanoparticles. Anal Methods 7:161–167 Chen WW, Fang XE, Li H, Cao HM, Kong JL (2016) A simple paper-based colorimetric device for rapid mercury(II) assay. Sci Rep 6:31948 Christus AAB, Panneerselvam P, Ravikumar A, Morad N, Sivanesan S (2018a) Colorimetric determination of Hg(II) sensor based on magnetic nanocomposite (Fe3O4@ZIF-67) acting as peroxidase mimics. J Photochem Photobiol A Chem 364:715–724 Christus AAB, Panneerselvam P, Ravikumar A (2018b) Novel, sensitive and selective colorimetric detection of arsenate in aqueous solution by a Fenton-like reaction of Fe3O4 nanoparticles. Anal Methods 10:4378–4386 Deng HH, He SB, Lin XL, Yang L, Lin Z, Chen RT, Peng HP, Chen W (2019a) Target-triggered inhibiting oxidase-mimicking activity of platinum nanoparticles for ultrasensitive colorimetric detection of silver ion. Chin Chem Lett 30:1659–1662 Deng HH, Luo BY, He SB, Chen RT, Lin Z, Peng HP, Xia XH, Chen W (2019b) Redox recyclingtriggered peroxidase-like activity enhancement of bare gold nanoparticles for ultrasensitive colorimetric detection of rare-earth Ce3+ ion. Anal Chem 91:4039–4046 Fan KL, Wang H, Xi JQ, Liu Q, Meng XQ, Duan DM, Gao LZ, Yan XY (2017) Optimization of Fe3O4 nanozyme activity via single amino acid modification mimicking an enzyme active site. Chem Commun 53:424–427 Gao LZ, Yan XY (2016) Nanozymes: an emerging field bridging nanotechnology and biology. Sci China Life Sci 59:400–402 Gao LZ, Zhuang J, Nie L, Zhang JB, Zhang Y, Gu N, Wang TH, Feng J, Yang DL, Perrett S, Yan XY (2007) Intrinsic peroxidase-like activity of ferromagnetic nanoparticles. Nat Nanotechnol 2:577–583 Gao LZ, Fan KL, Yan XY (2017) Iron oxide nanozyme: a multifunctional enzyme mimetic for biomedical applications. Theranostics 7:3207–3227 He YF, Qi F, Niu XH, Zhang WC, Zhang XF, Pan JM (2018a) Uricase-free on-demand colorimetric biosensing of uric acid enabled by integrated CoP nanosheet arrays as a monolithic peroxidase mimic. Anal Chim Acta 1021:113–120

90

X. Niu et al.

He YF, Niu XH, Li LH, Li X, Zhang WC, Zhao HL, Lan MB, Pan JM, Zhang XF (2018b) Microwave-assisted fabrication of bimetallic PdCu nanocorals with enhanced peroxidase-like activity and efficiency for thiocyanate sensing. ACS Appl Nano Mater 1:2397–2405 Huang YY, Ren JS, Qu XG (2019a) Nanozymes: classification, catalytic mechanisms, activity regulation, and applications. Chem Rev 119:4357–4412 Huang LJ, Zhu QR, Zhu J, Luo LP, Pu SH, Zhang WT, Zhu WX, Sun J, Wang JL (2019b) Portable colorimetric detection of mercury(II) based on a non-noble metal nanozyme with tunable activity. Inorg Chem 58:1638–1646 Jiang CF, Li ZJ, Wu YX, Guo W, Wang JS, Jiang Q (2018) Colorimetric detection of Hg2+ based on enhancement of peroxidase-like activity of chitosan-gold nanoparticles. Bull Kor Chem Soc 39:625–630 Kim YS, Jurng J (2013) A simple colorimetric assay for the detection of metal ions based on the peroxidase-like activity of magnetic nanoparticles. Sens. Actuators B Chem. 176:253–257 Kora AJ, Rastogi L (2018) Peroxidase activity of biogenic platinum nanoparticles: a colorimetric probe towards selective detection of mercuric ions in water samples. Sens. Actuators B Chem. 254:690–700 Li W, Chen B, Zhang HX, Sun YH, Wang J, Zhang JL, Fu Y (2015) BSA-stabilized Pt nanozyme for peroxidase mimetics and its application on colorimetric detection of mercury(II) ions. Biosens Bioelectron 66:251–258 Li HP, Liu HF, Zhang JD, Cheng YX, Zhang CL, Fei XY, Xian YZ (2017) Platinum nanoparticle encapsulated metal-organic frameworks for colorimetric measurement and facile removal of mercury(II). ACS Appl Mater Interfaces 9:40716–40725 Li D, Liu BW, Huang PJJ, Zhang ZJ, Liu JW (2018a) Highly active fluorogenic oxidase-mimicking NiO nanozymes. Chem Commun 54:12519–12522 Li SQ, Liu XD, Chai HX, Huang YM (2018b) Recent advances in the construction and analytical applications of metal-organic frameworks-based nanozymes. TrAC Trends Anal Chem 105:391–403 Li X, Wang LJ, Du D, Ni L, Pan JM, Niu XH (2019a) Emerging applications of nanozymes in environmental analysis: opportunities and trends. TrAC Trends Anal Chem 120:115653 Li CR, Hai J, Fan L, Li SL, Wang BD, Yang ZY (2019b) Amplified colorimetric detection of Ag+ based on Ag+-triggered peroxidase-like catalytic activity of ZIF-8/GO nanosheets. Sens. Actuators B Chem. 284:213–219 Li Q, Wu F, Mao M, Ji X, Wei LY, Li JY, Ma L (2019c) A dual-mode colorimetric sensor based on copper nanoparticles for the detection of mercury-(II) ions. Anal Methods 11:4014–4021 Li D, Garisto SL, Huang PJJ, Yang J, Liu BW, Liu JW (2019d) Fluorescent detection of fluoride by CeO2 nanozyme oxidation of Amplex red. Inorg Chem Commun 106:38–42 Li X, Liu BX, Ye K, Ni L, Xu XC, Qiu FX, Pan JM, Niu XH (2019e) Highly sensitive and specific colorimetric detection of phosphate by using Zr(IV) to synergistically suppress the peroxidasemimicking activity of hydrophilic Fe3O4 nanocubes. Sens Actuators B Chem 297:126822 Liang MM, Yan XY (2019) Nanozymes: from new concepts, mechanisms, and standards to applications. Acc Chem Res 52:2190–2200 Liao H, Liu GJ, Liu Y, Li R, Fu WS, Hu LZ (2017) Aggregation-induced accelerating peroxidaselike activity of gold nanoclusters and their applications for colorimetric Pb2+ detection. Chem Commun 53:10160–10163 Liao H, Hu LZ, Zhang YZ, Yu XR, Liu YL, Li R (2018) A highly selective colorimetric sulfide assay based on the inhibition of the peroxidase-like activity of copper nanoclusters. Microchim Acta 185:143 Lien CW, Unnikrishnan B, Harroun SG, Wang CM, Chang JY, Chang HT, Huang CC (2018) Visual detection of cyanide ions by membrane-based nanozyme assay. Biosens Bioelectron 102:510–517 Lien CW, Yu PH, Chang HT, Hsu PH, Wu T, Lin YW, Huang CC, Lai JY (2019) DNA engineered copper oxide-based nanocomposites with multiple enzyme-like activities for specific detection of mercury species in environmental and biological samples. Anal Chim Acta 1084:106–115

3 Nanozymes: Emerging Nanomaterials to Detect Toxic Ions

91

Lin YH, Ren JS, Qu XG (2014) Nano-gold as artificial enzymes: hidden talents. Adv Mater 26:4200–4217 Liu BW, Liu JW (2015) Accelerating peroxidase mimicking nanozymes using DNA. Nanoscale 7:13831–13835 Liu BW, Huang ZC, Liu JW (2016a) Boosting the oxidase mimicking activity of nanoceria by fluoride capping: rivaling protein enzymes and ultrasensitive F
detection. Nanoscale 8:13562–13567 Liu Y, Xiang YP, Ding D, Guo R (2016b) Structural effects of amphiphilic protein/gold nanoparticle hybrid based nanozyme on peroxidase-like activity and silver-mediated inhibition. RSC Adv 6:112435–112444 Liu Y, Xiang YP, Zhen YL, Guo R (2017) Halide ion-induced switching of gold nanozyme activity based on Au-X interactions. Langmuir 33:6372–6381 Long YJ, Li YF, Liu Y, Zheng JJ, Tang J, Huang CZ (2011) Visual observation of the mercurystimulated peroxidase mimetic activity of gold nanoparticles. Chem Commun 47:11939–11941 Lu Y, Yu J, Ye WC, Yao X, Zhou PP, Zhang HX, Zhao SQ, Jia LP (2016) Spectrophotometric determination of mercury(II) ions based on their stimulation effect on the peroxidase-like activity of molybdenum disulfide nanosheets. Microchim Acta 183:2481–2489 Ma CM, Ma Y, Sun YF, Lu Y, Tian EL, Lan JF, Li JL, Ye WC, Zhang HX (2019) Colorimetric determination of Hg2+ in environmental water based on the Hg2+-stimulated peroxidase mimetic activity of MoS2-Au composites. J Colloid Interface Sci 537:554–561 Mohammadpour Z, Safavi A, Shamsipur M (2014) A new label free colorimetric chemosensor for detection of mercury ion with tunable dynamic range using carbon nanodots as enzyme mimics. Chem Eng J 255:1–7 Motherwell WB, Bingham MJ, Six Y (2001) Recent progress in the design and synthesis of artificial enzymes. Tetrahedron 57:4663–4686 Murakami Y, Kikuchi J, Hisaeda Y, Hayashida O (1996) Artificial enzymes. Chem Rev 96:721–758 Niu XH, He YF, Pan JM, Li X, Qiu FX, Yan YS, Shi LB, Zhao HL, Lan MB (2016) Uncapped nanobranch-based CuS clews used as an efficient peroxidase mimic enable the visual detection of hydrogen peroxide and glucose with fast response. Anal Chim Acta 947:42–49 Niu XH, He YF, Li X, Song HW, Zhang WC, Peng YX, Pan JM, Qiu FX (2017) Trace iodide dramatically accelerates the peroxidase activity of VOx at ppb-concentration levels. Chem Select 2:10854–10859 Niu XH, He YF, Li X, Zhao HL, Pan JM, Qiu FX, Lan MB (2019) A peroxidase-mimicking nanosensor with Hg2+-triggered enzymatic activity of cysteine-decorated ferromagnetic particles for ultrasensitive Hg2+ detection in environmental and biological fluids. Sens. Actuators B Chem. 281:445–452 Peng CF, Pan N, Juan QZ, Wei XL, Shao G (2017) Colorimetric detection of thiocyanate based on inhibiting the catalytic activity of cystine-capped core-shell Au@Pt nanocatalysts. Talanta 175:114–120 Song YJ, Qu KG, Zhao C, Ren JS, Qu XG (2010) Graphene oxide: intrinsic peroxidase catalytic activity and its application to glucose detection. Adv Mater 22:2206–2210 Sui N, Liu FY, Wang K, Xie FX, Wang LN, Tang JJ, Liu MH, Yu WW (2017) Nano Au-Hg amalgam for Hg2+ and H2O2 detection. Sens. Actuators B Chem. 252:1010–1015 Sun HJ, Zhou Y, Ren JS, Qu XG (2018) Carbon nanozymes: enzymatic properties, catalytic mechanism, and applications. Angew Chem Int Ed 57:9224–9237 Tang SR, Wang ML, Li GW, Li X, Chen W, Zhang L (2018) Ultrasensitive colorimetric determination of silver(I) based on the peroxidase mimicking activity of a hybrid material composed of graphitic carbon nitride and platinum nanoparticles. Microchim Acta 185:273 Torigoe H, Ono A, Kozasa T (2010) HgII ion specifically binds with T:T mismatched base pair in duplex DNA. Chem Eur J 16:13218–13225

92

X. Niu et al.

Wang GL, Jin LY, Wu XM, Dong YM, Li ZJ (2015) Label-free colorimetric sensor for mercury (II) and DNA on the basis of mercury(II) switched-on the oxidase-mimicking activity of silver nanoclusters. Anal Chim Acta 871:1–8 Wang XY, Hu YH, Wei H (2016) Nanozymes in bionanotechnology: from sensing to therapeutics and beyond. Inorg Chem Front 3:41–60 Wang QQ, Wei H, Zhang ZQ, Wang EK, Dong SJ (2018a) Nanozyme: an emerging alternative to natural enzyme for biosensing and immunoassay. TrAC Trends Anal Chem 105:218–224 Wang CH, Tang GE, Tan HL (2018b) Colorimetric determination of mercury(II) via the inhibition by ssDNA of the oxidase-like activity of a mixed valence state cerium-based metal-organic framework. Microchim Acta 185:475 Wang L, Huang ZC, Liu YB, Wu J, Liu JW (2018c) Fluorescent DNA probing nanoscale MnO2: adsorption, dissolution by thiol, and nanozyme activity. Langmuir 34:3094–3101 Wang YW, Liu Q, Wang LX, Tang SR, Yang HH, Song HB (2019) A colorimetric mercury (II) assay based on the Hg(II)-stimulated peroxidase mimicking activity of a nanocomposite prepared from graphitic carbon nitride and gold nanoparticles. Microchim Acta 186:7 Wei H, Wang EK (2013) Nanomaterials with enzyme-like characteristics (nanozymes): nextgeneration artificial enzymes. Chem Soc Rev 42:6060–6093 Wen SH, Zhong XL, Wu YD, Liang RP, Zhang L, Qiu JD (2019) Colorimetric assay conversion to highly sensitive electrochemical assay for bimodal detection of arsenate based on cobalt oxyhydroxide nanozyme via arsenate absorption. Anal Chem 91:6487–6497 Wu GW, He SB, Peng HP, Deng HH, Liu AL, Lin XH, Xia XH, Chen W (2014) Citrate-capped platinum nanoparticle as a smart probe for ultrasensitive mercury sensing. Anal Chem 86:10955–10960 Wu SW, Guo DZ, Xu XC, Pan JM, Niu XH (2020) Colorimetric quantification and discrimination of phenolic pollutants based on peroxidase-like Fe3O4 nanoparticles. Sens. Actuators B Chem. 303:127225 Xia WQ, Zhang P, Fu WS, Hu LZ, Wang Y (2019) Aggregation/dispersion-mediated peroxidaselike activity of MoS2 quantum dots for colorimetric pyrophosphate detection. Chem Commun 55:2039–2042 Xie JX, Zhang XD, Jiang H, Wang S, Liu H, Huang YM (2014) V2O5 nanowires as a robust and efficient peroxidase mimic at high temperature in aqueous media. RSC Adv 4:26046–26049 Xiong YH, Su LJ, Yang HG, Zhang P, Ye FG (2015) Fabrication of copper sulfide using a Cu-based metal organic framework for the colorimetric determination and the efficient removal of Hg2+ in aqueous solutions. New J Chem 39:9221–9227 Xu XC, Wang LJ, Zou XB, Wu SW, Pan JM, Li X, Niu XH (2019a) Highly sensitive colorimetric detection of arsenite based on reassembly-induced oxidase-mimicking activity inhibition of dithiothreitol-capped Pd nanozyme. Sens. Actuators B Chem. 298:126876 Xu XC, Zou XB, Wu SW, Wang LJ, Pan JM, Xu MJ, Shan W, Li X, Niu XH (2019b) Colorimetric determination of As(III) based on 3-mercaptopropionic acid assisted active site and interlayer channel dual-masking of Fe-Co-layered double hydroxides with oxidase-like activity. Microchim Acta 186:815 Xu XC, Zou XB, Wu SW, Wang LJ, Niu XH, Li X, Pan JM, Zhao HL, Lan MB (2019c) In situ formation of fluorescent polydopamine catalyzed by peroxidase-mimicking FeCo-LDH for pyrophosphate ion and pyrophosphatase activity detection. Anal Chim Acta 1053:89–97 Yang HG, Xiong YH, Zhang P, Su LJ, Ye FG (2015) Colorimetric detection of mercury ions using MnO2 nanorods as enzyme mimics. Anal Methods 7:4596–4601 Zhang ST, Li H, Wang ZY, Liu J, Zhang HL, Wang BD, Yang ZY (2015a) A strongly coupled Au/Fe3O4/GO hybrid material with enhanced nanozyme activity for highly sensitive colorimetric detection, and rapid and efficient removal of Hg2+ in aqueous solutions. Nanoscale 7:8495–8502 Zhang DY, Chen Z, Omar H, Deng L, Khashab NM (2015b) Colorimetric peroxidase mimetic assay for uranyl detection in sea water. ACS Appl Mater Interfaces 7:4589–4594

3 Nanozymes: Emerging Nanomaterials to Detect Toxic Ions

93

Zhang WC, Niu XH, Li X, He YF, Song HW, Peng YX, Pan JM, Qiu FX, Zhao HL, Lan MB (2018a) A smartphone-integrated ready-to-use paper-based sensor with mesoporous carbondispersed Pd nanoparticles as a highly active peroxidase mimic for H2O2 detection. Sens. Actuators B Chem. 265:412–420 Zhang WC, Niu XH, Meng SC, Li X, He YF, Pan JM, Qiu FX, Zhao HL, Lan MB (2018b) Histidine-mediated tunable peroxidase-like activity of nanosized Pd for photometric sensing of Ag+. Sens. Actuators B Chem. 273:400–407 Zhang XH, Liu W, Li XM, Zhang Z, Shan DL, Xia H, Zhang ST, Lu XQ (2018c) Ultrahigh selective colorimetric quantification of chromium(VI) ions based on gold amalgam catalyst oxidoreductase-like activity in water. Anal Chem 90:14309–14315 Zhi LH, Zuo W, Chen FJ, Wang BD (2016) 3D MoS2 composition aerogels as chemosensors and adsorbents for colorimetric detection and high-capacity adsorption of Hg2+. ACS Sustain Chem Eng 4:3398–3408 Zhou Y, Ma ZF (2017) Fluorescent and colorimetric dual detection of mercury(II) by H2O2 oxidation of o-phenylenediamine using Pt nanoparticles as the catalyst. Sens. Actuators B Chem. 249:53–58 Zhu R, Zhou Y, Wang XL, Liang LP, Long YJ, Wang QL, Zhang HJ, Huang XX, Zheng HZ (2013) Detection of Hg2+ based on the selective inhibition of peroxidase mimetic activity of BSA-Au clusters. Talanta 117:127–132

Chapter 4

Applications of Nanozymes in Wastewater Treatment Vinod Kumar Yata

Abstract Hazardous waste containing wastewaters should be treated with efficient and economically feasible methods for sustainable water management. Adaptations of novel wastewater treatment methods are required to protect the environment and to provide a high level of health protection. Conventional methods need to be combined with advanced methods to remove the toxic contaminants from wastewater. Treatment of wastewater with enzymes has been shown to improve the treatment efficiency with reduced sludge volume and reduced odour. High cost and stability of the enzymes are major limitations for the implications of enzymes in wastewater treatment. Nanomaterials with an enzyme-like activity, which are called nanozymes, are emerging as potential alternatives for natural enzymes in wastewater treatment. Nanozymes have been shown oxidase, peroxidase, superoxide dismutase and catalase enzymes like activity. Nanozymes are highly stable than natural enzymes and can exhibit the activity at a wide range of pH and temperatures. Production cost is less than that of natural enzymes, and nanozymes can be stored for longer periods. Multi functionalization and reusability are some of the important properties for wider applications of nanozymes in different types of wastewaters. Keywords Nanozymes · Wastewater · Oxidase · Peroxidase · Superoxide dismutase · Catalase

Abbreviations ABTS BSA-Pt ELISA HRP Km

2, 20 -Azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) bovine serum albumin – platinum Enzyme-linked immunosorbent assay Horseradish peroxidase Michaelis–Menten constant

V. K. Yata (*) Animal Biotechnology Centre, National Dairy Research Institute (NDRI), Karnal, Haryana, India © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 H. K. Daima et al. (eds.), Nanozymes for Environmental Engineering, Environmental Chemistry for a Sustainable World 63, https://doi.org/10.1007/978-3-030-68230-9_4

95

96

OPD PANI SOD TMB

4.1

V. K. Yata

o-phenylenediamine Polyaniline Superoxide dismutase 3,30 ,5,50 -tetramethylbenzidine

Introduction

Wastewater contains a wide variety of toxic contaminants such as organic, inorganic chemicals and biological materials (Bolong et al. 2009). Emerging contaminants such as endocrine-disrupting chemicals, surfactant metabolites, acidic pharmaceuticals, antibacterial agents, acidic in wastewater pose significant threats to the environment and human health (Lapworth et al. 2012). In addition to the conventional activated sludge treatment and advanced wastewater treatment processes, there is a need to develop cost-effective, efficient methods for wastewater treatment. Conventional methods of wastewater treatment include coagulation, flocculation and sedimentation (Zinicovscaia 2016). Co-agaultaion is a method of neutralization of suspended particles in the wastewater upon rapid mixing with co-agaultaion chemicals. This process forms micro flocs that are not visible with the naked eye (Prakash et al. 2014). Flocculation is a slow mixing process of the wastewater treatment, and it results in the formation of pin flocs that are visible with a naked eye. Typical wastewater treatment plants involve sedimentation stage after coagulation and flocculation in some cases alternate solid removal process is involved (Ma et al. 2008). Sedimentation or solid removal process is followed by filtration. Ion exchange, adsorption, membrane filtration and electrochemical methods are being applied in the wastewater treatments depending upon the pollutants and chrematistics of wastewater (Ghernaout and Ghernaout 2012). Coagulation and flocculation are associated with drawbacks such as the high amount of sludge that needs spate treatments process before discarding. Ion exchange and membrane filtration are not suitable for the effluents with a high concentration of contaminants (Prakash et al. 2014). Advanced oxidation processes (AOP’s) is an efficient water treatment method that generates highly reactive groups for the degradation of pollutants in the wastewater. Ozonation, wet peroxide ozonation, catalytic ozonation, Fenton based wet peroxidation are non-photochemical AOPs and theses can generate the reactive groups without using a light source. Ozone–hydrogen peroxide–UV radiation, Photo-Fenton system, Photocatalytic system are some of the photo chemical-based AOPs. The utility of these methods has been limited due to high cost and low efficiency of pollutant removal. (Stasinakis 2008; Oturan and Aaron 2014). Biological materials have been employed for many years in the treatment of wastewater, and enzymes have used for the degradation of pollutants (Dhir 2014). Aerobic or anaerobic wastewater treatment processes involves micro-organisms and their associated enzymes (Karam and Nicell 1997). Enzymes can act on specific contaminants to remove them by precipitation or to convert them to other products.

4 Applications of Nanozymes in Wastewater Treatment

97

Enzymes also can covert the waste products to useful products in the wastewater treatment (Burgess and Pletschke 2008). Even though there are several advantages of enzymes used in wastewater treatment, the commercial use is limit due to high economic cost, storage and stability of enzymes at different wastewater conditions like pH and temperature. Enzymes also digested by proteases that may present in the wastewater (Aitken 1993). There is a need to develop materials which can withstand harsh conditions and exhibit enzyme-like activity. Nanozymes have attracted the researchers to use it as an alternative to enzymes (Wei and Wang 2013). Nanozymes are the nanomaterials which can convert the substrate to the products which are similar to the enzyme activity. Nanozymes follow the similar enzyme kinetics and more stable than enzymes. These are easy to produce with very less cost than producing enzymes (Shin et al. 2015). Advantages and challenges of nanozymes were summarized and compared with Natural Enzymes and Nanomaterial-Based Catalysts in Table 4.1. In this chapter, we briefed the importance of various natural enzymes in wastewater treatment and focused the discussion on nanozymes activity for the conversion of substrates to products. Enzyme like activity of nanozymes compared with natural enzymes, and this chapter provided the potential applications of different nanozymes in wastewater treatment with critical opinion.

4.2

Importance of Enzymes in Wastewater Treatment

Enzymes from microbial and plant origin are being explored in the water treatment for the degradation of harmful contaminants (Karam and Nicell 1997). Natural enzymes catalyze the pollutants with high specificity and selectivity. Enzymes can be purified from microbial and plant sources and utilized in wastewater treatment applications (Duran and Esposito 2000). Peroxidases obtained from horseradish, Artromyces ramosus and plant materials exhibit phenol, aniline, polyaromatic, herbicide and chlorophenol degradation (Siddique et al. 1993; Kim et al. 1997; Gramss et al. 1999). These enzymes were also effective in Kraft effluents and black liquor decontamination, dewatering of slimes, dewatering of Slimes and water decontamination (Ferrer et al. 1991). Chloroperoxidase obtained from Caldariomyces funago exhibits the oxidation of phenolic compounds (Pickard et al. 1991; Saby and Luong 1998). Lignin peroxidase obtained from Phanerochaete chrysosporium and Chrysonilia sitophila shown the applications in the degradation of Aromatic compounds and phenolic materials, and Kraft effluent remediation (Johjima et al. 1999; Mansilla et al. 1997). Manganese peroxidase obtained from Phanerochaete chrysopsorium, Nematolona frowardie, Phebia radiate, Lentinula edodes have shown the applications in the wastewater treatment by the degradation of phenols, lignins, pentachlorophenol and dyes (Aitken et al. 1994; Grabski et al. 1996; Hofrichter et al. 1999). Tyrosinases obtained from Agaricus bisporus have the applications in wastewater treatment by phenols and amines degradation, xenobiotic compound removal, catechol oxidation and polymerization of phenolic compounds

98

V. K. Yata

Table 4.1 Comparison of Nanozymes with Natural Enzymes and Nanomaterial-Based Catalysts Catalysts Nanozymes

Natural enzymes

Nanomaterialbased catalysts

Advantages (1) high catalytic activity (2) tunable catalytic activity and types (3) multienzyme mimetic activity (4) high stability (5) recyclable utilization (6) easy to mass produce (7) low cost (8) long-term storage (9) robustness to harsh environments (10) Easy to multifunctionalize (large surface area for bioconjugation) (11) controllable catalytic activity and types via external stimuli (such as light, ultrasound, heat, magnetic field, etc.) (12) unique physicochemical properties (such as fluorescence, electricity, paramagnetic properties, etc. (1) high catalytic activity (2) high substrate selectivity (3) good biocompatibility (4) wide range of biocatalysis (5) wide range of applications (6) rational design via gene and protein engineering

(1) tunable catalytic activity (2) low cost (3) easy to mass produce (4) high stability (5) robustness to harsh environments (6) long-term storage (7) exact catalytic mechanism (8) atomically precise structural information

Challenges (1) limited types of nanozymes (2) limited substrate selectivity (3) the ambiguous mechanism (4) size-, shape-, structure-, and composition-dependent catalytic properties (5) lack of standards and reference materials (6) potential nanotoxicity

(1) high cost (2) limited stability (3) hard to store long term (4) hard to mass produce (5) time-consuming separation and purification (6) hard to use in a harsh environment (such as heat, extreme pH, salinity, UV irradiation, etc.) (1) low specificity (2) low selectivity (3) poor biocompatibility (4) size-, shape-, structure-, and composition-dependent catalytic properties

Reproduced with permission from Liang and Yan (2019)

(Burton et al. 1998; Edwards et al. 1999). Laccase obtained from Trametes hispida, Pyricularia oryzae, Trametes versicolor, Pycnoporus cinnabarinus and plant materials have shown a wide variety of applications in Dyes decolouration, degradation of azo-dyes textile effluent, chlorophenols, urea derivatives, 2,4-dichlorpenol and benzopyrenes (Dec and Bollag 1994; Chivukula and Renganathan 1995; Grey et al. 1998; Gianfreda et al. 1998; Rama et al. 1998; Rodriguez et al. 1999). Catechol dioxygenases obtained from Comamonas testosterone and Pseudomonas pseudoalacaligenes shown the oxidation of chlorophenol and diuron degradation (Hollender et al. 1997; Bohdziewicz 1998). Phenoloxidase-like enzymes obtained from Gloeophyllum trabeum, Trametes versicolor, Phanerochaete chrysosporium Thermoascus aurantiacus exhibits the Kraft effluent decontamination and

4 Applications of Nanozymes in Wastewater Treatment

99

Chlorinated compounds degradation (Machuca et al. 1999; Duran and Esposito 2000). Purification of the enzymes is a laborious process, and it involves high cost for the production of enzymes in large scale. Enzyme stability may be decreased upon long term storage, and it may not be stable under harsh conditions of wastewater.

4.3

Nanoparticles as Enzyme Mimics

Organic or inorganic nanomaterials characterize Nanozymes with nanostructures which can exhibit the biochemical reactions of the substrates of natural enzymes (Huang et al. 2019). Recent studies on nanozymes have been shown the oxidase, peroxidase, superoxide dismutase (SOD), catalases, DNAase, phosphatase activity (Wang et al. 2018). Nanozyme enzyme-catalyzed reactions are summarized in Table 4.2. Nanoenzymes have been exploited in the wide variety of fields such as biosensing, antibacterial, cancer treatment (Wei and Wang 2013). Research on nanozymes has gained momentum to extend the applications in environmental applications. Nanozymology is an emerging field which deals with artificial enzymes. As enzyme research at an initial stage, the fundamental mechanism of nanozymes needs to be established with structure-activity relationship studies. A rational design strategy needs to be addressed to improve the catalytic activity and specificity of nanozymes. Translation of the nanozyme research to application into the wastewater treatment is one of the major challenges of nanozymes, and it will be addressed with extensive research in the near future.

4.3.1

Iron Nanoparticles as Nanozymes

The use of Iron nanoparticles in wastewater treatment has received much attention due to its properties such as adsorption and photocatalytic activity and immobilization on various surfaces (Xu et al. 2012). Despite the limitations such as aggregation, competitive adsorption expensive separations, iron nanoparticles have shown greater potential in wastewater treatment (Mohapatra and Anand 2010). Recent Table 4.2 Types of Enzyme like activity of nanozymes and chemical reactions S.No 1

Type of enzyme – like activity of nanozymes Peroxidases –like activity

2

Oxidase-like enzyme activity

3 4

Superoxide Dismutases--like enzyme activity Catalase--like enzyme activity

Chemical reactions 2AH + H2O2 ! 2A + 2H2O 2AH + ROOH ! 2A + ROH + H2O O2 + AH ! H2O + A O2 + AH + H2O ! H2O2 + A O2∙  þ 2Hþ ! H2 O2 þ O2 H2O2 ! 2H2O + O2

100

V. K. Yata

investigations revealed that iron nanoparticles could exhibit enzyme-like activity for the conversion of substrates to products. Fe3O4 nanoparticles and FePO4 micro flowers synthesized by hydrothermal method exhibited SOD-like activity and Peroxidase/catalase activity, respectively. CoFe2O4 nanoparticles synthesized by the solvothermal method, shown oxidase activity (Wang et al. 2012a; Shen et al. 2013). MnFe2O4 nanocomposite synthesized by co-precipitation method shown oxidase activity (Vernekar et al. 2016). CoFe layered double hydroxides synthesized by co-precipitation method exhibited peroxidase activity (Zhang et al. 2012). Gao et al. (2007), synthesized Fe3O4 magnetic nanoparticles of 150 nm and 300 nm size by the solvothermal method and Fe3O4 magnetic nanoparticles of 30 nm size were synthesized by the co-precipitation method. Fe3O4 nanoparticles exhibit the peroxidase-like activity and catalyzed peroxidase substrates such as 3,30 ,5,50 -tetramethylbenzidine (TMB), di-azo-aminobenzene and o-phenylenediamine (OPD). Fe3O4 nanoparticles Km value for TMB was found to be 0.098, whereas horseradish peroxidase (HRP) has Km value of 0.098 Mm for against the same substrate (Gao et al. 2007). In a recent study, Qin et al. (2019) demonstrated that iron oxide nanozymes were capable of inactivating virus envelope by catalyzing the lipid peroxidation. In this study, iron oxide nanozymes exhibited inactivation of influenza A viruses by destroying hemagglutinin, neuraminidase, and matrix protein 1 (Fig. 4.1). Fe3O4 magnetic nanoparticles of 150 nm and 300 nm size were synthesized by the solvothermal method, and Fe3O4 magnetic nanoparticles of size were Synthesized by the co-precipitation method. Effect of peroxidase activity of Fe3O4 nanocrystals was studied and found that spheres have higher peroxidase activity that triangular plates and octahedral structures (Liu et al. 2011). In a study, Wang et al. 2018 demonstrated that the ultrasound irradiation in combination with magnetic nanoparticles enhanced the degradation of pollutant. This study observed the peroxidize like activity of Fe3O4 magnetic nanoparticles were significantly improved for the degradation of dye pollutant Rhodamine B when sonication was applied in pulsed mode. Iron nanoparticles based nanozymes are more stable than natural enzymes and easy to synthesize. Iron nanozymes have been shown high efficiency in the degradation of pollutants.

4.3.2

Manganese Nanoparticles as Nanozymes

Manganese oxide nanoparticles have been exploited as adsorbents for the removal of contaminants from wastewater (Islam et al. 2018). In a study by Wan et al. (2012), Manganese oxide nanoparticles showed HRP and laccase enzyme-like activities, and it indicates the potential applications of these nanoparticles in wastewater treatment. In a study, MnO2-mediated immunoassay was developed for the detection of bacteria where MnO2 is replaced with HRP in Enzyme-linked immunosorbent assay (ELISA) (Fig. 4.2). MnO2 shown peroxidase-like activity and it converted TMB to coloured compound with H2O2 in the reaction. Laccase is an enzyme present in basidiomycetes that catalyzes the oxidation of a wide number of phenolic

4 Applications of Nanozymes in Wastewater Treatment

101

Fig. 4.1 Diagram of viral lipoperoxidation by iron oxide nanozymes for virus inactivation. Iron oxide nanozymes directly contact with influenza A viruses particles and disintegrates viral lipid envelope via enhancing the level of lipid peroxidation. (Reproduced with permission from Qin et al. (2019))

compounds and aromatic amines. In a study, laccase was isolated from trametes trogii able to oxidize 2,20 -azino-bis-3-ethylbenzothiazoline-6-sulfonate (ABTS) to decolourize the commercial dye poly R478. The laccase-like activity of nanostructured manganese oxide observed for the conversion of ABTS and 17β-estradiol. Nano-structured manganese oxide particles were synthesized by the hydrothermal

102

V. K. Yata

Fig. 4.2 Schematic representation of MnO2-mediated immunoassay and comparison with HRP-mediated ELISA. (Reproduced with permission from Wan et al. (2012))

method by using MnO4 as precursors (Wang et al. 2017). MnO2 nanozymes have huge potential for further research and development for the wastewater treatment.

4.3.3

Copper Nanoparticles as Nanozymes

Copper nanoparticles have the ability to kill a wide variety of nanoparticles, and it has been used as a disinfectant in wastewater treatment (Al-Saydeh et al. 2017). These nanoparticles have many useful physical, and chemical properties can mimic like peroxidase, laccase enzymes which could be the potential candidate for substrate conversion in wastewater. Cupric oxide nanoparticles mimic the peroxidase-like activity and of catalyzes the substrates like TMB, including ABTS and 3,30 -diaminobenzidine. CuO nanoparticles exhibit a higher binding affinity for the substrate TMB than HRP The cupric oxide nanoparticles which were prepared by the quick-precipitation method, shown a higher affinity to hydrogen peroxide resulted in a higher catalytic activity than commercial CuO nanoparticles (Chen et al. 2011). Copper sulfide concave polyhedral superstructures synthesized by a solvothermal reaction catalyzed the oxidation of TMB and OPD in the presence of hydrogen peroxide (He et al. 2012). A synergistic effect was observed when Cu9S5 nanocrystals on polyaniline (PANI) nanowires using mercaptoacetic acid in a hydrothermal reaction PANI/Cu9S5 nanocomposite showed the oxidation of the peroxidase substrate TMB in the presence of H2O2 (Lu et al. 2013). Guanosine monophosphate -Cu nanozymes exhibit the Oxidase-like activity and remove the

4 Applications of Nanozymes in Wastewater Treatment

103

Fig. 4.3 Artificial metal and metal oxide nanozyme-mediated the transformation mechanism. (Reproduced with permission from Chen et al. (2019))

pollutant such as hydroquinone, naphthol, and catechol. CH-Cu nanozymes have excellent laccase-like activity, and these nanozymes can degrade the Chlorophenols and bisphenols (Chen et al. 2019). Both the nanozymes transform a diverse range of R–OH to generate a new product to eliminate the toxicity (Fig. 4.3a). Artificial metal and metal oxide nanozymes adsorb R–OH and undergo one-electron transfer to produce intermediates (Fig. 4.3b). The laccase-like activity of copper nanoparticles was observed upon coronation with a cysteine (Cys)-histidine (His) dipeptide and the composite was named CH-Cu Nanozymes. 2,4-dichlorophenol and hydroquinone were degraded by using CH-Cu nanozymes (Wang et al. 2019).

104

4.3.4

V. K. Yata

Gold Nanoparticles as Nanozymes

Gold nanoparticles remove the contaminants from water by physical adsorption or chemical reaction and degrade the contaminants by catalytic reaction. Gold nanoparticles exhibit peroxidase, superoxide dismutase and catalase like an activity for the conversion of the substrate (Abu-Elsaoud and Abdel-Azeem 2020). Wang et al. (2012b), synthesized cysteamine- or citrate-modified gold nanoparticles and compared the unmodified gold nanoparticles for catalytic activity toward peroxidase substrates such as TMB and ABTS. The study revealed that charge characteristics of the nanoparticles play a key role and unmodified gold nanoparticles show higher catalytic activity than surface-modified gold nanoparticles. He et al. (2013), reported that gold nanoparticles could act as Superoxide dismutase and catalase mimetics (Fig. 4.4). This study demonstrated the generation of hydroxyl radicals by gold nanoparticles in the presence of hydrogen peroxide. In a study, peroxidase mimetic activity of gold nanoparticles was stimulated by mercury.

4.3.5

Platinum Nanoparticles as Nanozymes

Platinum nanoparticles can exhibit peroxidase enzyme-like activity, and these nanozymes need further research for future applications in the wastewater treatment. Li et al. (2015), synthesized bovine serum albumin – platinum (BSA-Pt) nanoparticles and performed the nanozyme kinetics with TMB and hydrogen peroxide. BSA-Pt exhibited high peroxidase activity with km values of 0.119 mM and 41.8 mM form TMB and H2O2, respectively (Fig. 4.5). Fan et al. (2011), synthesized platinum nanoparticles using apoferritin as a nucleation substrate. These Fig. 4.4 Schematic representation of the catalytic properties of gold nanoparticles (Au NP). (Reproduced with permission from He et al. (2013))

4 Applications of Nanozymes in Wastewater Treatment

105

Fig. 4.5 Nanozyme kinetics of BSA–Pt (a) the concentration of H2O2 is fixed, and the TMB concentration is varied, (b) double-reciprocal plots of at fixed H2O2 at varied TMB concentration (c) the concentration of TMB is fixed and the H2O2 concentration is varied, and (d) doublereciprocal plots at fixed TMB concentration and varied H2O2 concentrations, respectively. (Reproduced with permission from Li et al. (2015))

nanoparticles exhibited catalase and peroxidase-like activity with hydrogen peroxide as a substrate. TMB and di-azo-aminobenzene were catalyzed platinum nanoparticles similar to that of native HRP. Cubic platinum nanocrystals synthesized by reduction method with cetyltrimethylammonium bromide can mimic like peroxidases and converts TMB in the presence of H2O2 (Ma et al. 2011). Porous Platinum nanotubes synthesized by a green method using tellurium nanowires as template was shown peroxidase-like activity in fact of H2O2 (Cai et al. 2013).

4.3.6

Hybrid Nanozymes

Combinations of two or more types of nanoparticles have been exhibited enzymelike activities with synergistic and additive effects. He et al. (2010), were synthesized three bimetallic alloy nanoparticles, namely, AgAu Nanoboxes AgPd and AgPt Nanoparticles. These nanoparticles exhibit peroxidase-like activity by the catalytic oxidation of OPD in the presence of H2O2. PdPt nanoparticles successfully reduced

106

V. K. Yata

4-nitrophenol even though The Pt nanoparticles alone showed no ability to reduce the same substrate (Capeness et al. 2019). Au-Cu2O core-shell nanocrystals showed intrinsic peroxidase-like property against the 3,30 ,5,50 -tetramethylbenzidine by catalytic oxidation in the presence of H2O2. These nanocrystals Au@Cu2O nanocrystals also exhibit photocatalytic inactivation of E. coli under visible light (Kuo et al. 2019). Superoxide dismutase, catalase, oxidase and peroxidase enzymelike activities of pt. nanoparticles were decreased with an in an increased concentration of Ag in Au@PtAg (Hu et al. 2013). In a study, Hydrogen peroxide and superoxide anion radicals were quenched by gold platinum nanoparticle stabilized with pectin which was synthesized by a citrate reduction method. Au/Fe3O4/GO Hybrid Material was synthesized by using polyethene glycol derivatives as the coupling linker. This reusable hybrid was rapid and efficient removal of Hg2+ in water (Zhang et al. 2015). V2O5 nanowires, WC nanorods, VO2 nanoplates, CePO4: Tb, Gd nanoparticles, ZnFe2O4/ZnO nanocomposite, CuInS2 nanocomposite, His-Au nanocomposites, Peroxidase, Gold/silver/Pt nanoparticles have been exhibited peroxidase-like enzyme activity (Qin et al. 2020). CoFe2O4 nanoparticles have shown oxidase enzyme-like activity, and it has been applied to the determination of trace sulfite in white wine samples (Zhang et al. 2013). In a recent study, porous CoFe2O4 nanozymes were synthesized via a facile method and evaluated for peroxidase-like catalytic activity. In this study, a pollutant dye, Tetramethylbenzidine, was degraded by using CoFe2O4 nanozymes in the presence of H2O2 (Wu et al. 2018). CeO2 nanoparticles and Co3O4 nanoparticles have shown peroxidase/oxidase/catalase/SOD enzyme-like activities (Jiao et al. 2012; Mu et al. 2012).

4.4

Conclusions and Future Scope

Nanozymes have shown great potential to remove the contaminants from wastewater and promising for environmental monitoring. Nanozyme kinetic studies indicated that some of the nanozymes have a greater affinity towards the substrates than natural enzymes. Further research is required on nanozymes to monitor the efficiency in larger quantities of wastewater. Detection stability of nanozymes is needed to be studied in a wide variety of wastewaters. Peroxidase like activity of the nanozymes has the potential to implement in wastewater treatment in large scale. Wastewater treatment through nanozymes is an ecofriendly and economical alternative conventional and biological methods. The utility of nanozymes could greatly reduce the sludge volume in wastewater treatment. Nanozymes will be a potential alternative to natural enzymes and nanomaterials based catalysts. This chapter is an attempt to understand the mechanism and apply these nanozymes for the removal of contaminants from the wastewater. Although there are some unanswered questions regarding the large scale implication of nanozymes, surface modification, and other tunable properties of nanozymes would lead to potential alternatives to natural enzymes.

4 Applications of Nanozymes in Wastewater Treatment

107

Acknowledgements The author would like to thank Department of Biotechnology, Government of in India for financial support and ICAR-National Dairy Research Institute, Karnal, India, for providing lab space. The author would like to express his sincere thanks to Dr. A K Mohanty for his valuable suggestions.

References Abu-Elsaoud AM, Abdel-Azeem AM (2020) Light, electromagnetic spectrum, and photostimulation of microorganisms with special reference to Chaetomium. In: Recent developments on Genus Chaetomium. Springer, Cham, pp 377–393 Aitken MD (1993) Waste treatment applications of enzymes: opportunities and obstacles. Chem Eng J 52(2):B49–B58 Aitken MD, Massey IJ, Chen T, Heck PE (1994) Characterization of reaction products from the enzyme catalyzed oxidation of phenolic pollutants. Water Res 28(9):1879–1889 Al-Saydeh SA, El-Naas MH, Zaidi SJ (2017) Copper removal from industrial wastewater: A comprehensive review. J Ind Eng Chem 56:35–44 Bohdziewicz J (1998) Biodegradation of phenol by enzymes from Pseudomonas sp. immobilized onto ultrafiltration membranes. Process Biochem 33(8):811–818 Bolong N, Ismail AF, Salim MR, Matsuura T (2009) A review of the effects of emerging contaminants in wastewater and options for their removal. Desalination 239(1–3):229–246 Burgess JE, Pletschke BI (2008) Hydrolytic enzymes in sewage sludge treatment: a mini-review. Water SA 34(3):343–350 Burton SG, Boshoff A, Edwards W, Rose PD (1998) Biotransformation of phenols using immobilized polyphenol oxidase. J Mol Catal B Enzym 5(1–4):411–416 Cai K, Lv Z, Chen K, Huang L, Wang J, Shao F et al (2013) Aqueous synthesis of porous platinum nanotubes at room temperature and their intrinsic peroxidase-like activity. Chem Commun 49 (54):6024–6026 Capeness MJ, Echavarri-Bravo V, Horsfall LE (2019) Production of biogenic nanoparticles for the reduction of 4-nitrophenol and oxidative laccase-like reactions. Front Microbiol 10:997 Chen W, Chen J, Liu AL, Wang LM, Li GW, Lin XH (2011) Peroxidase-like activity of cupric oxide nanoparticle. ChemCatChem 3(7):1151–1154 Chen W, Li S, Wang J, Sun K, Si Y (2019) Metal and metal-oxide nanozymes: bioenzymatic characteristics, catalytic mechanism, and eco-environmental applications. Nanoscale 11 (34):15783–15793 Chivukula M, Renganathan V (1995) Phenolic azo dye oxidation by laccase from Pyricularia oryzae. Appl Environ Microbiol 61(12):4374–4377 Dec J, Bollag JM (1994) Use of plant material for the decontamination of water polluted with phenols. Biotechnol Bioeng 44(9):1132–1139 Dhir B (2014) Potential of biological materials for removing heavy metals from wastewater. Environ Sci Pollut Res 21(3):1614–1627 Duran N, Esposito E (2000) Potential applications of oxidative enzymes and phenoloxidase-like compounds in wastewater and soil treatment: a review. Appl Catal B Environ 28(2):83–99 Edwards W, Bownes R, Leukes WD, Jacobs EP, Sanderson R, Rose PD, Burton SG (1999) A capillary membrane bioreactor using immobilized polyphenol oxidase for the removal of phenols from industrial effluents. Enzym Microb Technol 24(3–4):209–217 Fan J, Yin JJ, Ning B, Wu X, Hu Y, Ferrari M et al (2011) Direct evidence for catalase and peroxidase activities of ferritin–platinum nanoparticles. Biomaterials 32(6):1611–1618 Ferrer I, Dezotti M, Durán N (1991) Decolorization of Kraft effluent by free and immobilized lignin peroxidases and horseradish peroxidase. Biotechnol Lett 13(8):577–582

108

V. K. Yata

Gao L, Zhuang J, Nie L, Zhang J, Zhang Y, Gu N et al (2007) Intrinsic peroxidase-like activity of ferromagnetic nanoparticles. Nat Nanotechnol 2(9):577–583 Ghernaout D, Ghernaout B (2012) Sweep flocculation as a second form of charge neutralization—a review. Desalin Water Treat 44(1–3):15–28 Gianfreda L, Sannino F, Filazzola MT, Leonowicz A (1998) Catalytic behavior and detoxifying ability of a laccase from the fungal strain Cerrena unicolor. J Mol Catal B Enzym 4(1–2):13–23 Grabski AC, Burgess RR, Rasmussen JK, Coleman PL (1996) Immobilization of manganese peroxidase from Lentinula edodes on alkylaminated Emphaze (TM) AB 1 polymer for generation of Mn3+ as an oxidizing agent. Appl Biochem Biotechnol 60(1):1–17 Gramss G, Voigt KD, Kirsche B (1999) Oxidoreductase enzymes liberated by plant roots and their effects on soil humic material. Chemosphere 38(7):1481–1494 Grey R, Höfer C, Schlosser D (1998) Degradation of 2-chlorophenol and formation of 2-chloro-1, 4-benzoquinone by mycelia and cell-free crude culture liquids of Trametes versicolor in relation to extracellular laccase activity. J Basic Microbiol 38(5–6):371–382 He W, Wu X, Liu J, Hu X, Zhang K, Hou S et al (2010) Design of AgM bimetallic alloy nanostructures (M¼ Au, Pd, Pt) with tunable morphology and peroxidase-like activity. Chem Mater 22(9):2988–2994 He W, Jia H, Li X, Lei Y, Li J, Zhao H et al (2012) Understanding the formation of CuS concave superstructures with peroxidase-like activity. Nanoscale 4(11):3501–3506 He W, Zhou YT, Wamer WG, Hu X, Wu X, Zheng Z et al (2013) Intrinsic catalytic activity of Au nanoparticles with respect to hydrogen peroxide decomposition and superoxide scavenging. Biomaterials 34(3):765–773 Hofrichter M, Vares K, Scheibner K, Galkin S, Sipilä J, Hatakka A (1999) Mineralization and solubilization of synthetic lignin by manganese peroxidases from Nematoloma frowardii and Phlebia radiata. J Biotechnol 67(2–3):217–228 Hollender J, Hopp J, Dott W (1997) Degradation of 4-Chlorophenol via the meta cleavage pathway by Comamonas testosteroni JH5. Appl Environ Microbiol 63(11):4567–4572 Hu X, Saran A, Hou S, Wen T, Ji Y, Liu W et al (2013) Au@ PtAg core/shell nanorods: tailoring enzyme-like activities via alloying. RSC Adv 3(17):6095–6105 Huang Y, Ren J, Qu X (2019) Nanozymes: classification, catalytic mechanisms, activity regulation, and applications. Chem Rev 119(6):4357–4412 Islam MA, Morton DW, Johnson BB, Mainali B, Angove MJ (2018) Manganese oxides and their application to metal ion and contaminant removal from wastewater. J Water Process Eng 26:264–280 Jiao X, Song H, Zhao H, Bai W, Zhang L, Lv Y (2012) Well-redispersed ceria nanoparticles: promising peroxidase mimetics for H2O2 and glucose detection. Anal Methods 4 (10):3261–3267 Johjima T, Itoh N, Kabuto M, Tokimura F, Nakagawa T, Wariishi H, Tanaka H (1999) Direct interaction of lignin and lignin peroxidase from Phanerochaete chrysosporium. Proc Natl Acad Sci 96(5):1989–1994 Karam J, Nicell JA (1997) Potential applications of enzymes in waste treatment. J Chem Technol Biotechnol 69(2):141–153 Kim JE, Wang CJJ, Bollag JM (1997) Interaction of reactive and inert chemicals in the presence of oxidoreductases: Reaction of the herbicide bentazon and its metabolites with humic monomers. Biodegradation 8(6):387–392 Kuo MY, Hsiao CF, Chiu YH, Lai TH, Fang MJ, Wu JY et al (2019) Au@ Cu2O core@ shell nanocrystals as dual-functional catalysts for sustainable environmental applications. Appl Catal B Environ 242:499–506 Lapworth DJ, Baran N, Stuart ME, Ward RS (2012) Emerging organic contaminants in groundwater: a review of sources, fate and occurrence. Environ Pollut 163:287–303 Li W, Chen B, Zhang H, Sun Y, Wang J, Zhang J, Fu Y (2015) BSA-stabilized Pt nanozyme for peroxidase mimetics and its application on colorimetric detection of mercury (II) ions. Biosens Bioelectron 66:251–258

4 Applications of Nanozymes in Wastewater Treatment

109

Liang M, Yan X (2019) Nanozymes: from new concepts, mechanisms, and standards to applications. Acc Chem Res 52(8):2190–2200 Liu S, Lu F, Xing R, Zhu JJ (2011) Structural effects of Fe3O4 nanocrystals on peroxidase-like activity. Chem Eur J 17(2):620–625 Lu XF, Bian XJ, Li ZC, Chao DM, Wang C (2013) A facile strategy to decorate Cu 9 S 5 nanocrystals on polyaniline nanowires and their synergetic catalytic properties. Sci Rep 3:2955 Ma F, Zheng L, Chi Y (2008) Applications of biological flocculants (BFs) for coagulation treatment in water purification: turbidity elimination. Chem Biochem Eng Q 22(3):321–326 Ma M, Zhang Y, Gu N (2011) Peroxidase-like catalytic activity of cubic Pt nanocrystals. Colloids Surf A Physicochem Eng Asp 373(1–3):6–10 Machuca A, Aoyama H, Durán N (1999) Isolation and partial characterization of an extracellular low-molecular mass component with high Phenoloxidase activity from Thermoascus aurantiacus. Biochem Biophys Res Commun 256(1):20–26 Mansilla HD, Rodriguez J, Ferraz A, Duran N (1997) Biodegradation of acidolysis lignins from Chilean hardwoods by the ascomycete Chrysonilia sitophila. World J Microbiol Biotechnol 13 (5):545–548 Mohapatra M, Anand S (2010) Synthesis and applications of nano-structured iron oxides/ hydroxides–a review. Int J Eng Sci Technol 2(8):127–146 Mu J, Wang Y, Zhao M, Zhang L (2012) Intrinsic peroxidase-like activity and catalase-like activity of Co 3 O 4 nanoparticles. Chem Commun 48(19):2540–2542 Oturan MA, Aaron JJ (2014) Advanced oxidation processes in water/wastewater treatment: principles and applications. A review. Crit Rev Environ Sci Technol 44(23):2577–2641 Pickard MA, Kadima TA, Carmichael RD (1991) Chloroperoxidase, a peroxidase with potential. J Ind Microbiol 7(4):235–241 Prakash NB, Sockan V, Jayakaran P (2014) Waste water treatment by coagulation and flocculation. Int J Eng Sci Innov Technol 3(2):479–484 Qin T, Ma R, Yin Y, Miao X, Chen S, Fan K et al (2019) Catalytic inactivation of influenza virus by iron oxide nanozyme. Theranostics 9(23):6920 Qin L, Hu Y, Wei H (2020) Nanozymes: preparation and characterization. In: Yan (ed) Nanozymology. Springer, Singapore, pp 79–101 Rama R, Mougin C, Boyer FD, Kollmann A, Malosse C, Sigoillot JC (1998) Biotransformation of bezo [a] pyrene in bench scale reactor using laccase of Pycnoporus cinnabarinus. Biotechnol Lett 20(12):1101–1104 Rodriguez E, Pickard MA, Vazquez-Duhalt R (1999) Industrial dye decolorization by laccases from ligninolytic fungi. Curr Microbiol 38(1):27–32 Saby C, Luong JH (1998) A biosensor system for chlorophenols using chloroperoxidase and a glucose oxidase based amperometric electrode. Electroanalysis 10(1):7–11 Shen LH, Bao JF, Wang D, Wang YX, Chen ZW, Ren L et al (2013) One-step synthesis of monodisperse, water-soluble ultra-small Fe3 O4 nanoparticles for potential bio-application. Nanoscale 5(5):2133–2141 Shin HY, Park TJ, Kim MI (2015) Recent research trends and future prospects in nanozymes. J Nanomater 2015: 1–11 Siddique MH, St Pierre CC, Biswas N, Bewtra JK, Taylor KE (1993) Immobilized enzyme catalyzed removal of 4-chlorophenol from aqueous solution. Water Res 27(5):883–890 Stasinakis AS (2008) Use of selected advanced oxidation processes (AOPs) for wastewater treatment–a mini review. Global NEST J 10(3):376–385 Vernekar AA, Das T, Ghosh S, Mugesh G (2016) A remarkably efficient MnFe2O4-based oxidase nanozyme. Chem Asian J 11(1):72–76 Wan Y, Qi P, Zhang D, Wu J, Wang Y (2012) Manganese oxide nanowire-mediated enzyme-linked immunosorbent assay. Biosens Bioelectron 33(1):69–74

110

V. K. Yata

Wang W, Jiang X, Chen K (2012a) Iron phosphate microflowers as peroxidase mimic and superoxide dismutase mimic for biocatalysis and biosensing. Chem Commun 48 (58):7289–7291 Wang S, Chen W, Liu AL, Hong L, Deng HH, Lin XH (2012b) Comparison of the peroxidase-like activity of unmodified, amino-modified, and citrate-capped gold nanoparticles. ChemPhysChem 13(5):1199–1204 Wang X, Liu J, Qu R, Wang Z, Huang Q (2017) The laccase-like reactivity of manganese oxide nanomaterials for pollutant conversion: rate analysis and cyclic voltammetry. Sci Rep 7(1):1–10 Wang Q, Wei H, Zhang Z, Wang E, Dong S (2018) Nanozyme: an emerging alternative to natural enzyme for biosensing and immunoassay. TrAC Trends Anal Chem 105:218–224 Wang J, Huang R, Qi W, Su R, Binks BP, He Z (2019) Construction of a bioinspired laccasemimicking nanozyme for the degradation and detection of phenolic pollutants. Appl Catal B Environ 254:452–462 Wei H, Wang E (2013) Nanomaterials with enzyme-like characteristics (nanozymes): nextgeneration artificial enzymes. Chem Soc Rev 42(14):6060–6093 Wu L, Wan G, Hu N, He Z, Shi S, Suo Y et al (2018) Synthesis of porous CoFe2O4 and its application as a peroxidase mimetic for colorimetric detection of H2O2 and organic pollutant degradation. Nano 8(7):451 Xu P, Zeng GM, Huang DL, Feng CL, Hu S, Zhao MH et al (2012) Use of iron oxide nanomaterials in wastewater treatment: a review. Sci Total Environ 424:1–10 Zhang Y, Tian J, Liu S, Wang L, Qin X, Lu W et al (2012) Novel application of CoFe layered double hydroxide nanoplates for colorimetric detection of H2O2 and glucose. Analyst 137 (6):1325–1328 Zhang X, He S, Chen Z, Huang Y (2013) CoFe2O4 nanoparticles as oxidase mimic-mediated chemiluminescence of aqueous luminol for sulfite in white wines. J Agric Food Chem 61 (4):840–847 Zhang S, Li H, Wang Z, Liu J, Zhang H, Wang B, Yang Z (2015) A strongly coupled Au/Fe3O4/GO hybrid material with enhanced nanozyme activity for highly sensitive colorimetric detection, and rapid and efficient removal of Hg2+ in aqueous solutions. Nanoscale 7(18):8495–8502 Zinicovscaia I (2016) Conventional methods of wastewater treatment. In: Cyanobacteria for bioremediation of wastewaters. Springer, Cham, pp 17–25

Chapter 5

Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic Activity of NanoZymes Neeti Kalyani, Bandhan Chatterjee, and Tarun Kumar Sharma

Abstract Environmental pollution is a global health concern, affecting millions of lives. With the current pace of industrialization and unabated anthropogenic activities, the global burden of environmental pollutants is bound to rise. These pollutants take a heavy toll on human health, are also a major cause of global death and reduced life expectancy. They rapidly invade biospheres, including air, soil, and aquatic environment. From here, they find their way into the various food chain/webs and results in bioaccumulation and biomagnification, in a way affecting every member of the chain. Thus, there is an urgent need to combat this menace, and for any effective management first, there has to be an estimation of the extent and amount of contamination. Here comes the role of various pollutant sensors, a part traditionally confined to sophisticated and expensive instrumentation and methods. However, the combination of NanoZymes (nanoparticles exhibiting enzymatic properties) and aptamers (chemical substitutes of antibody) have revolutionized the field of sensing altogether. The NanoZymes, on the one hand, are inexpensive, and robust signal generating moiety works fluidly with aptamers. The aptamers, which can be economically produced with batch consistency, have excellent recognition ability. The combination of the duo has been reported to work efficiently in the existing biosensing platforms like lateral flows and electrochemical sensors. This chapter first concisely introduces the reader to the basic principle of the aptamer-nanozyme sensing mechanism and provides insights into the recent advancements in the field of aptamer nanozyme-based pollutant sensing. Major advances include the development of new combinations of nanomaterials, new shapes of nanomaterials to enhance the sensitivity of the biosensor. The last decade has also witnessed the development of high affine and specific aptamers for a host of environmental pollutants, which aptly supplements the development of sensors by providing novel and high-performance recognition elements for them. Additionally, due emphasis has been laid to develop mobile Point-of-Care (POC)/on-site sensors N. Kalyani · B. Chatterjee · T. K. Sharma (*) Aptamer Technology and Diagnostics Laboratory, Multidisciplinary Clinical and Translational Research Group, Translational Health Science and Technology Institute (THSTI), Faridabad, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 H. K. Daima et al. (eds.), Nanozymes for Environmental Engineering, Environmental Chemistry for a Sustainable World 63, https://doi.org/10.1007/978-3-030-68230-9_5

111

112

N. Kalyani et al.

that do not need sophisticated instrumentation, trained manpower, and also comes at an affordable cost. These sensors will enable rapid, affordable on-site detection of environmental pollutants. Keywords Environment pollutants · NanoZymes · Aptamer · Metallic nanoparticles · Biosensing · Colorimetric detection · Pesticides · Heavy metal · Toxin · Antibiotics

Abbreviations ABTS BR-CN 4-CD 4-CN CFU CTAB FTO DNA ELISA GNPs MOF SELEX ssDNA TMB WHO

5.1

2,20 -azino-bis (3-ethyl benzothiazoline-6-sulfonic acid) Benzene-ring doped graphitic-C3N4 Benzo-4-chlorohexadienone (4-CD) 4-chloro-1-naphthol Colony forming units Cetyltrimethylammonium bromide Fluorine-doped tin oxide Deoxyribonucleic acid Enzyme-linked immunosorbent assay Gold nanoparticles Metal-organic frameworks Systematic evolution of ligands by exponential enrichment Single stranded DNA 3,30 ,5,50 -tetramethylbenzidine World Health Organization

Introduction

Environmental pollution is one of the gravest threats in the anthropocene epoch (an era marked by humans activities being the main contributor to environmental change) (Crutzen 2002; Steffen et al. 2007) to life on earth (Rockström et al. 2009). It is one of the largest contributors to global morbidity. For reference, pollution caused nine million premature deaths in 2015, a whopping 16% of global deaths. To have a better understanding, consider this “the pollution caused more deaths than malaria, tuberculosis, and AIDS combined” (Landrigan et al. 2018). The largest quanta of these deaths are reported from low and medium-income countries, which are already suffering from constrained healthcare systems (Chatterjee et al. 2019). The genesis of the current environmental crisis can be attributed to the onset of the industrial revolution, which then grew rapidly with the industrialization (Landrigan et al. 2018). These unregulated and unabated processes have lead to the generation of a colossal amount of pollutants. According to an estimate, we have generated more than 140,000 new chemical entities since 1950. Among these, nearly

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

113

5000 (including but not limited to pesticides, heavy metals, antibiotics and, dyes) are extensively used by humans and have found their way into almost every biosphere (Langley and Mort 2012; Tchounwou et al. 2012; Kraemer et al. 2019). And from these spheres, the pollutants get entry into the various food chains and manifests its disastrous effects with bioaccumulation and then biomagnification (Gobas et al. 1993; Kelly et al. 2004; Ali and Khan 2019). These pollutants are highly toxic and known to cause endocrine disruption, teratological effects, and various diseases including but not limited to cancer, cardiovascular, cerebrovascular diseases, chronic kidney diseases, and medical complications ranging from mild to severe, even death (Landrigan et al. 2018). With the current pace of global industrialization, the possibility of lesser pollutants discharge seems bleak. Considering the current situation, there is an urgent need to address this issue; at least their invasion into the food chains has to be curtailed. However, for effective environmental pollutant management or limiting the pollutant discharge, an accurate and frequent environmental monitoring system is a prerequisite. In such a scenario, facile, rapid, and economical detection of various pollutants holds the key for effective containment. The traditional methods of detection of these pollutants largely rely on heavy instrumentation like various spectroscopic and chromatographic approaches, which are both expensive and have high operating costs owing to the prerequisite of sophisticated infrastructure and trained workforce (Shimizu et al. 2019; Chatterjee et al. 2020). These instruments are large and non-portable, so the samples to be tested are to be collected from various sources and send to various centers, which are primarily located away from the pollutant sites (Zhang et al. 2018). This creates a logistical problem, requiring specialized personnel, at the same time negates the possibility of frequent testing. So there is an urgent need to devise detection methods which are economical, simple, and less demanding of trained manpower and sophisticated instrumentation. Aptamer-based sensing is one of the promising candidates for the current exigency (Sharma et al. 2014; Weerathunge et al. 2014; Chatterjee et al. 2019, 2020; Kaur et al. 2019; Das et al. 2020; Reid et al. 2020). Aptamers are chemical surrogates of antibodies whose generation is not limited to immunogenic entities (Jayasena 1999; Crivianu-Gaita and Thompson 2016; Seok Kim et al. 2016; Dunn et al. 2017). So aptamers can be generated against a broader range of targets, including environmental pollutants. These aptamers, once developed against a target, are chemically synthesized so they are devoid of any batch to batch variation and can be rapidly produced in a discounted budget. They can be readily adapted on various point of care sensors with platforms ranging from lateral flow to electrochemical sensing (Sharma et al. 2016, 2017; Dhiman et al. 2017). Of the many available aptamer-based biosensing, a combination of aptamers and NanoZymes (Huang et al. 2019) (nanoparticles behaving like enzymes), is particularly popular (Wang et al. 2016a; Das et al. 2019; Ou et al. 2019; Tian et al. 2019; Weerathunge et al. 2019b). The popularity of this combination draws from the simplicity of the developed test, which is devoid of any expensive chemical or instrument requirement, no or minimal technical expertise needed, and is very robust

114

N. Kalyani et al.

(Chatterjee et al. 2020). Further, the combination has been frequently employed on lateral flow assays, which provides instant on-site visual results (Pfeiffer and Mayer 2016; Dembowski and Bowser 2018; Schüling et al. 2018; Reid et al. 2020). In this chapter, we discuss the application of the aptamer in the sensing of various environmental pollutants, emphasizing on heavy metal and chemical pollutants. The chapter entails the principle of aptamer-nanozyme based sensing and underlines on the recent developments in the field. The chapter also provides a brief description of the basics of aptamer and NanoZymes while providing a detailed description of various pollutant sensing with the aptamer-nanozyme duo at the center of the sensing platform.

5.2

NanoZymes

Since the first report of iron oxide nanoparticles showing enzyme mimicking activity (Gao et al. 2007) many different types of metal and metal oxide nanoparticles have been shown to have intrinsic catalytic activities (Jiang et al. 2019; Wang et al. 2020). Nanoparticles exhibit various enzymatic activities such as oxidase, peroxidase, phosphatase, esterase, catalase, protease, nuclease, hydrolase, ferroxidase, and superoxide dismutase (Li et al. 2015; Wang et al. 2016c; Gao et al. 2016; Xu et al. 2019; Zhang et al. 2020a). In recent years, nanomaterials having enzymatic activities are used as sensing components due to their stability, low cost, ease in synthesis, robustness, excellent reactivity, multi-functions, long–term storage, and tunable enzymatic activity (Sun et al. 2018; Wang et al. 2019). Generally, the enzyme-like behavior of nanomaterials depends on the surface properties and can be modified by changing shape, size, composition, and surface groups (Chen et al. 2019; Huang et al. 2019; Wang et al. 2020). Moreover, the enzyme mimetic activity of NanoZymes can be modulated by the adsorption and desorption of DNA/proteins, which may result in distinct color changes (Yuan et al. 2017). These color changes can be utilized for environmental monitoring, clinical detection, and biosensing (Karim et al. 2018; Chen et al. 2018; Huang et al. 2019; Peng et al. 2019). In the case of oligonucleotides, the negatively charged backbone and positively charged bases interact with cationic and anionic NanoZymes, respectively, whereas proteins interact with the charged side groups of amino acids (Zhan et al. 2016; Wang et al. 2018b). There are some limitations of NanoZymes, such as low specificity and poor catalytic activity, but this can overcome by controlled synthesis and surface modifications (Chen et al. 2019; Huang et al. 2019). Gold nanoparticles (GNPs) are the most favorable nanomaterial used for biomolecular sensing due to their peculiar properties such as facile synthesis, large extinction coefficient, and excellent biocompatibility (Vilela et al. 2012; Pang et al. 2016; Syedmoradi et al. 2017). Several GNPs-based aptasensors have been reported for the colorimetric detection of different targets like antibiotics, proteins, nucleic acids, toxins, pesticides, and bacteria (Weerathunge et al. 2014; Taghdisi et al. 2015; Zhang and Li 2016; Yan et al. 2017; Das et al. 2020). Besides GNPs,

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

115

silver, iron, nickel, platinum, and cerium nanoparticles are also being utilized for sensing applications by exploiting their nanozymatic activity (Bülbül et al. 2016; Zeng et al. 2018; Weerathunge et al. 2019a). Recently, nanoparticle hybrids (Au@Fe3O4, Au@Pt, graphene/Ni@Pt) and metal-organic frameworks (Cu-MOF, Ce-MOF) with catalytic activities have been constructed for the sensing of different molecules (Wang et al. 2016b, 2017b, 2018a; Dehghani et al. 2018).

5.3

Aptamers

Aptamers are small RNA and single-stranded DNA, which are isolated by an in vitro technique known as Systematic Evolution of Ligands by EXponential enrichment (SELEX) (Famulok 1999; Crawford 2003; Lee et al. 2013; Dunn et al. 2017). Aptamers can strongly and specifically interact with their targets via unique threedimensional structures. Their targets vary from small molecules (antibiotics, amino acids, and pesticides) (Wang et al. 2012) to proteins (thrombin, lysozyme, and albumin) (Bock et al. 1992; Tran et al. 2010; Takenaka et al. 2017) to whole cells (bacteria and cancer cells) (Civit et al. 2018; Zou et al. 2018). They offer several advantages over antibodies such as low cost, excellent stability and reproducibility, purity, non-toxicity, smaller size, longer shelf life, and can be synthesized and modified easily (Lian et al. 2015; Zhao et al. 2015; Taghdisi et al. 2018). These unique features make them a favorable candidate as the recognition element in biosensors. In recent years, aptamers have been employed in conjugation with nanoparticles having catalytic activity for the development of numerous assays for the sensing of numerous biomolecules such as proteins, bacteria, cancer, and small molecules (Wang et al. 2016c; Ou et al. 2019). These assays can be interpreted using various techniques such as Ultraviolet-visible spectrophotometry, Surface-Enhanced Raman Scattering, and electrochemical techniques (Huang et al. 2018; Ouyang et al. 2018; Tian et al. 2018).

5.4 5.4.1

NanoZymes for Pollutants Detection Heavy Metal

Heavy metals can get accumulated in the biological food chains and poses grievous risks to the environment and human health even if they are present in a very low amount (Babamiri et al. 2018; Wang et al. 2020). The release of heavy metals results in the increase of their concentration in the atmosphere, which enters the atmospheric soil-water cycle and can persist in the circulation for years (Rice et al. 2014). Lead, for example, is one of the most toxic heavy metal which have harmful effects on the liver, kidneys, nervous system, and reproductive system (Sun et al. 2015; Qian et al. 2015). Mercury causes cellular, renal, embryonic, cardiovascular,

116

N. Kalyani et al.

reproductive, hematological, endocrine, pulmonary defects, and impairment of neurological developments (Taber and Hurley 2008; Fernandes Azevedo et al. 2012). Hence, the trace level detection of heavy metals is crucial for food safety, monitoring of the environment, and clinical examinations (Sitko et al. 2013). For the detection of heavy metals at such low concentrations, various techniques are used, such as atomic fluorescence spectrometry (Imhof et al. 2016), inductively coupled plasma mass spectrometry (Ammann 2002) electrochemical analysis (Aragay and Merkoçi 2012), and atomic absorption spectrometry (Nawab et al. 2018). These methods have good sensitivity and accuracy, but they are complex, time-consuming, require sophisticated instruments and highly trained manpower (Kuang et al. 2013; Nawab et al. 2018). Thus, simple, rapid, specific, accurate, and economical methods are sought after for the detection of heavy metals. Table 5.1 listed the NanoZymes based methods for the detection of heavy metals using aptamer as a sensor probe. Kim and Jurng have reported a facile colorimetric method to detect metal ions based-on the catalytic activity of Fe3O4 magnetic nanoparticles, which varies depending on the interactions between Fe3O4 magnetic nanoparticles, analyte, and their aptamers (Kim and Jurng 2013). In acidic conditions (pH-4), Fe3O4 magnetic nanoparticles oxidize the transparent O-phenylenediamine to red color diimine derivatives in the presence of H2O2. Thymine rich single-stranded DNA (T-rich ssDNA) was used as a sensory element for the detection of mercury ions, which binds to the positively charged Fe3O4 magnetic nanoparticles and inhibits the peroxidase activity of magnetic nanoparticles reflected in the decrease in the red color of the reaction product. The interaction between T-rich ssDNA and target ensue the recovery of peroxidase activity due to the wrapping of ssDNA around the target and repulsion between the positively charged mercury ions and Fe3O4 magnetic nanoparticles (Fig. 5.1). The change in peroxidase activity can be simply visualized by the naked eye within 30 min. The assay is sensitive for mercuric ions in the range of 5–75 μM and does not show any activity in the presence of other metal ions like Mn2+, Zn2+, Fe3+, Pb2+, Cd2+, Cr3+, and Ni2+. Qi and coworkers demonstrate a label-free chemiluminescent sensor for ultrasensitive detection of Hg2+ using positively charged GNPs (Qi et al. 2017). Since the H2O2-luminol chemiluminescence reaction takes place in alkaline conditions, the H2O2 and luminol predominantly exist as hydroperoxide ion and the luminol anion. The strong electrostatic interactions between anionic luminol and positively charged GNPs leads to the strong catalytic activity of GNPs for the chemiluminescent reaction. An amplification in signal was achieved by employing the single-stranded DNA (ssDNA) for charge screening effect on GNPs (Fig. 5.2). The negatively charged backbone of ssDNA directly screens the positive charge on GNPs, resulting in aggregation and, in turn, reduction of chemiluminescent catalytic activity. But, in the presence of Hg2+, the strong interaction between ssDNA and Hg2 + minimizes the screening of charge on GNPs and results in the dispersion of GNPs, which enhances the chemiluminescent signal. This study was successful in detecting Hg2+ in a wide range from 0.1 to 1000 nM with the detection limit of 10 pM due to signal amplification. Tap and lake water samples were spiked with Hg2+ to test the sensor performance in real samples and resulted in 104.2% and 95.3% recovery.

Nanozyme GNPs

GNPs

GNPs/Graphene nanohybrids

GNPs

Ironporphyrinic metalorganic framework (GR  5/(Fe  P)nMOF)

Fe3O4 magnetic nanoparticles

Target Mercury

Lead

Mercury

Lead

Lead

Mercury

Peroxidase

Peroxidase

Peroxidase

Peroxidase

Peroxidase

Activity Peroxidase

DNA

DNA

DNA

DNA

DNA

Type of aptamer DNA

50 -TTGTTTGTTGG CCCCCCTTCTTTC TT-30 50 -CTCTCT GGGT GGGTGGGTGGGT TCTCTC-30 50 -ACAGACATCATC TCTGAAGTAG-CGC CGC CGTATAGTGA GAAA CTCA-CTATrA GGAAGAGATGATGT CTGTTTTTT-(CH2)6SH-30 50 -TTCTTTCTTCCCC TTGTTTGTT-30

50 -GGTGGTGTGGT GGTTGGTGTTGG-30

Aptamer sequence 50 -TTT TTT TTT T-30

5 μM

5–75 μM Ultraviolet-visible

0.034 nM

0.05– 200 nM

Electrochemical

602 pM

0.2– 30 nM

Ultraviolet-visible

3.63 nM

0.07 nM

Limit of detection 16 pM

0.01– 0.5 μM

Detection range 62 nM 1.2 μM 0.13– 53.33 nM

Ultraviolet-visible

SERS

Technique Chemiluminescence

Table 5.1 List of NanoZymes based methods developed using aptamers for the detection of heavy metals

60 min

120 min

30 min

80 min

30 min

Detection time 30 min

Kim and Jurng (2013)

Taghdisi et al. (2015) Cui et al. (2015)

References Qi et al. (2017) Ouyang et al. (2018) Tian (2019)

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . . 117

118

N. Kalyani et al.

Fig. 5.1 Schematic representation of the detection of mercury ions by Fe3O4 magnetic nanoparticles using thymine rich DNA. Binding of ssDNA with Fe3O4 magnetic nanoparticles inhibits their peroxidase activity, whereas the peroxidase activity recovers in the presence of mercury ions due to their interaction with thymine-rich ssDNA manifesting in the red-colored product. (Reprinted with permission of Elsevier from reference (Kim and Jurng 2013); Copyright 2017)

However, this method can only detect mercury in ionic form. Therefore, pretreatment of the samples is required, which are comprising of other forms of Hg, such as anionic or neutral species or complexes.

5.4.2

Pathogens

Pathogens pose a grave threat to humans and other organisms. Contamination of different water bodies with water-borne pathogens and associated illnesses is an important water quality concern all over the world. Water-borne pathogens like bacteria, viruses, and protozoans are the cause of life-threatening diseases (Pandey et al. 2014; Das et al. 2019, 2020). Diarrhea alone, which is caused by rotavirus and Escherichia coli is one of the major reasons for the death of children below 5 years of age. Millions of people get infected in developing countries by water-borne pathogens (World Health Organization 2019). Various techniques are employed for the detection of pathogens in the environment, such as culturing, Surface-Enhanced Raman scattering, chromatography, and polymerase chain reaction (Mounier et al.

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

119

Fig. 5.2 Chemiluminescence detection mechanism of Hg2+ utilizing charge screening effect of positively charged GNPs. The positive charge of GNPs is screened by the negative backbone of ssDNA, whereas, in the presence of Hg2+ the interaction between aptamer and Hg2+ weakens the screening and in turn, the chemiluminescence catalytic activity of GNPs increases. (Reprinted with permission of Elsevier from reference (Qi et al. 2017); Copyright 2017)

2014; Kumar et al. 2015; Chengalroyen et al. 2016; Cui et al. 2017; Gahlaut et al. 2019). Although these techniques are sensitive, they demand high cost, well-trained manpower, good laboratory conditions, bulky instruments, and long assay time (Loesche et al. 1992; Wellinghausen et al. 2009). All these aspects limit the employment of these conventional techniques for the timely detection of pathogens on-site in minimal resource settings like developing nations (Wei et al. 2019). Therefore, researchers are exploring simpler, rapid, and economic assays for the fast and sensitive detection of pathogens in environmental samples to prevent harmful effects on human health. In recent years, NanoZymes based aptasensors for chromogenic detection and quantification of pathogens have attracted attention due to low cost, fast response time, and easier protocols (Liu et al. 2016; Alhogail et al. 2016) (Table 5.2). Dual nanoparticles based simple and sensitive method has been demonstrated for the detection of Staphylococcus aureus using aptamer recognition and magnetic separation (Wang et al. 2017b). Cu-Metal organic frameworks (MOFs) have displayed peroxidase activity and can catalyze the oxidation of 3,30 ,5,50 -tetramethylbenzidine (TMB) in the presence of H2O2 in acidic conditions at 45  C emanating yellow-colored product. Although copper ions have intrinsic peroxidase activity (Zheng et al. 2016) these MOFs with copper as an active center have much higher peroxidase activity due to modification in electronic structure mediated by the coordination interaction between metal ion and ligand. The

Nanozyme

GNPs

Au@Pd nanoparticles

Fe3O4 nanoparticles

GNPs

GNPs

Target

Norovirus

Campylobacter jejuni

Streptococcus mutans

Escherichia coli

Pseudomonas aeruginosa

Peroxidase

Peroxidase

Peroxidase

Peroxidase

Peroxidase

Activity

DNA

DNA

DNA

DNA

DNA

Type of aptamer 5´-GCTAGCGAAT TCCGTACGAAGG GCGAATTCCACA TTGGGCTGCAGC CCGGGGGATCC-30 50 -GCAAGATCTC CGAGATATCGT GCTGGGGGGTG GTTTGTTTGGG TCGGTTGTTTT GGTTGGGCTG CAGGTAATA CG TATACT-30 50 -ATACTATCGC ATTCCTTCCGA GGGGGGAGGG GGGGGTGGGG GTCGGT-30 and 50 -biotin-TTTATA CTATCGCATTCC TTCCGAGGGGGG AGGGGGGGGTG GGGGTCGGT-30 50 -CCCTCCGGGG GGGTCATCGGGA TACCTGGTAAG GATA-30 50 -CCCCCGTTGC TTTCGCTTTTCC TTTCGCTTTTGT TCGTTTCGTCCC TGCTTCCTTTCT TG-30

Aptamer sequence

10 CFU/mL

12 CFU/mL

100 CFU/mL

60 CFU/mL

10–106 CFU/mL

0–109 CFU/mL

10 to 109 CFU/mL

60 to 6  107 CFU/mL

Electrochemical

Electrochemical

Ultraviolet visible

Ultraviolet visible

30 virus/mL

200–10,000 viruses/mL

Ultraviolet visible

Limit of detection

Detection range

Technique

Table 5.2 List of NanoZymes-based methods for the detection of pathogens using aptamers

10 min

5 min

15 min

24 h

10 min

Detection time

Das et al. (2019)

Das et al. (2020)

Zhang et al. (2019)

Dehghani et al. (2018)

Weerathunge et al. (2019b)

References

120 N. Kalyani et al.

Peroxidase

Peroxidase

Peroxidase

Peroxidase

Copper-based metalorganic framework

ZnFe2O4/rGO

Fe3O4 nanoparticles cluster

Platinum nanoparticles

Staphylococcus aureus

Salmonella enterica serovar typhimurium

Listeria monocytogenes

Salmonella enterica, Escherichia coli, and Listeria monocytogenes

DNA

DNA

DNA

DNA

50 -NH2-GCAATG GTACGGTACTTC TCGGCACGTTCT CAGTAGCGCTC GCTGGTCATCCC ACAGCTACGTCA AAAGTGCACGC TACTTTGCTAA-30 50 -bio-AGTAATG CCCGGTAGTTA TTCAAAGATGA GTAGGAAAAGA-30 and 50 -AAAAAAAA AAAAAGTAATG CCCGGTAGTTAT TCAAAGATGAGT AGGAAAAGA-30 50 NH2-TTTTTTTTTT ATCCATGGGGCGG AGATGAGGGGGA GGAGGGCGGGTA CCCGGTTGAT-30 S. enterica – SH-TA TGGCGGCGTCAC CCGACGGGGACT TGACATTATGAC AG; E. coli – SH-CC GGACGCTTATGC CTTGCCATCTAC AGAGCAGGT GTGACGG; L. monocytogenes – SH-TACTATCGCGG AGACAGCGCGGG AGGCACCGGGGA 11 CFU/mL

5.4  103 CFU/ mL

10 CFU/mL

11–1.10  105 CFU/mL

5.4  103–108 CFU/mL

S. enterica  10800 CFU/mL; E. coli  102-108 CFU/ mL; and L. monocytogenes  102107 CFU/mL

Ultravioletvisible

Colorimetric

Ultravioletvisible

20 CFU/mL

50–10,000 CFU/mL

Ultravioletvisible

145 min

20 h

90 min

Wei et al. (2019)

Zhang et al. (2016)

Wu et al. (2017)

Wang et al. (2017b)

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . . 121

122

N. Kalyani et al.

Fig. 5.3 Cu-metal organic framework nanoparticles having peroxidase activity for detection of Staphylococcus aureus using aptamer. Aptamer-labeled Fe3O4 nanoparticles were employed for magnetic separation. In the presence of the target, bacteria clamped Cu-MOF settle down, and thereby, the concentration of Cu-MOF decreases in the supernatant leading to a reduction in peroxidase activity. (Reprinted with permission of American Chemical Society from reference (Wang et al. 2017b); Copyright 2017)

abundance of amine groups on the surface of Cu-MOF can facilitate their modification with amino terminated aptamers using glutaraldehyde as cross-linker. Both nanostructures (Cu-MOFs and Fe3O4 nanoparticles) were functionalized with aptamers selective towards S. aureus having different targets presents on the surface of S. aureus, where Fe3O4 nanoparticles were used for the magnetic separation and Cu-MOFs were used for the signal generation. Under the influence of the magnetic field, S. aureus bound to Cu-MOFs and Fe3O4 settles down in the tube, declining the amount of Cu-MOFs in the supernatant and thus, weakening the peroxidase activity. In the absence of a target, whole Cu-MOFs remain in the supernatant, and high peroxidase activity is observed (Fig. 5.3). Using this method, S. aureus can be detected by determining the residual catalytic activity of Cu-MOFs in the supernatant by the chromogenic reaction. This method has achieved linearity in the range of 50–10,000 CFU/mL with the limit of detection of 20 CFU/mL. The selectivity of the method S. aureus was also tested against S. dysenteriae, S. typhimurium, and E. coli O157:H7. A GNPs based sensor has been proposed by Das et al. for the rapid and facile detection of E. coli (Das et al. 2020). The developed sensor can detect the pathogenic bacteria within 5 min and at a very low cost ($2). The inherent peroxidase activity of GNPs was utilized for the electrochemical detection of E. coli. GNPs oxidizes the colorless TMB to a dark blue colored product in the presence of H2O2. Aptamer

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

123

reduces the peroxidase activity of GNPs by covering their surface. In the presence of E. coli, owing to a higher affinity towards E. coli, aptamer dissociates from the surface of GNPs, and their peroxidase activity recovers. The presence of the bacteria can be easily confirmed by the naked eye or can be quantified by the electrochemical method developed where the oxidation of TMB was quenched by H2SO4, which provides TMB in electrochemically active form. The quenched TMB solution was electrochemically measured using a screen-printed electrode, and the amperometric response was recorded (Fig. 5.4). The assay showed a turn-on electrochemical response in the presence of E. coli with a dynamic range from 10 to 109 CFU/mL and a detection limit of 100 CFU/mL. The performance of the sample was also tested for the determination of E. coli in spiked apple juice samples.

5.4.3

Organic Pollutants

Organic pollutants can enter the environment via agricultural route or as an industrial waste, which creates an imbalance in the environment and endanger organisms due to their toxicity (Song et al. 2015). They can have chronic to severe acute effects on human health and culminates in the number of illnesses such as endocrine disruption, cardiovascular diseases, birth defects, hypertension, cancer, and anemia (Abhilash and Singh 2009; Jarošová et al. 2015; Asif et al. 2016). The overwhelming use of antibiotics, especially in developing countries, causing antibiotic resistance, which is hampering the curing of fatal diseases like pneumonia and tuberculosis (World Health Organization 2017). Traditionally, organic pollutants have been detected by capillary electrophoresis, fluorimetry, enzyme-linked immunosorbent assay (ELISA), high-performance liquid chromatography, gas chromatography, and mass spectrometry (Mauldin et al. 2006; Guan and Eichler 2011; Appenzeller and Tsatsakis 2012; Zuloaga et al. 2012; Cheah et al. 2014; Zhai et al. 2015). Although these techniques are sensitive, their shortcomings like requirements of sophisticated instruments, trained personnel, long processing times, complicated sample preparations, and high cost have limited their use in wide applications (Yang et al. 2015a; Jiao et al. 2016; Bazin et al. 2017). Thus, alternative techniques are urgently required for the simplistic, economical, and rapid sensing of organic pollutants. Particularly, NanoZymes-based assay fulfills all these criteria, and sensing of the analyte can be realized visually by simply recording the change in color (Saha et al. 2012; Zohora et al. 2017; Aldewachi et al. 2018). Table 5.3 enlisted the NanoZymes-based aptasensors developed for the detection of various organic pollutants such as antibiotics, pesticides, toxins, and dye.

5.4.3.1

Toxins

In the environment, toxins can enter by agricultural, industrial, or military activity (Ligler et al. 2003). The presence of toxins in agriculture produce causes huge post-

124

N. Kalyani et al.

Fig. 5.4 Schematic representation of the working principle; (a) in the absence of the target, the aptamer keeps covering the GNPs surface, thus hindering the TMB oxidation, however, in the presence of the target, aptamers deserts the surface of the GNP surface, allowing the TMB oxidation at the surface of GNPs, hence the blue color. (b) Electrochemical sensing where the extent of TMB oxidation in the response of E.coli concentration is measured with voltammetry. (Reprinted with permission of Elsevier from reference (Das et al. 2020); Copyright 2017)

3D graphene/Fe3O4AuNPs hybrids

Ochratoxin A

GNPs

Cu(HBTC)-1/Fe3O4AuNPs nanosheets Gold nanoclusters

Kanamycin

Sulfadimethoxine

Tetracycline

Kanamycin

Platinum nanoparticles functionalized nano Fe-MIL-88NH2 (NMOF-Pt) GNPs

Kanamycin

Sulfadimethoxine

Graphene/ nickel@palladium GNPs

GNPs

Abrin

Sulfadimethoxine

GNPs

Zearalenone

Antibiotics

Au@Fe3O4 nanoparticles

Ochratoxin A

Toxins

Nanozyme

Target

Category

Peroxidase

Peroxidase

Peroxidase

DNA

DNA

DNA

DNA

DNA

Peroxidase

Peroxidase

DNA

DNA

DNA

DNA

Peroxidase

Peroxidase

Peroxidase

Peroxidase

DNA

DNA

Peroxidase

Peroxidase

Type of aptamer

Activity

50 -NH2-(CH2)6-CAAG ATGGGGGTTGAGG CTAAGCCGAACCC TTTTGTTTTTT-30 50 -TGGGGGTTGAGG CTAAGCCGA-30 50 -TGGGGGTTGAGG CTAAGCCGA-30 50 -GAGGGCAACGA GTGTTTATAGA-30 50 -NH2-CGTA CGGA

50 -GATCGGGTGTGG GTGGCGTAAAGGA GCATCGGACANH2–30 50 -GATGGGGAAAG GGTCCCCCTGGGTT GGAGCATCGGA CA-30 50 -ATCCTGTGAGGA ATGCTCATGCATA GCAAGGGCT-30 50 -CGTACGGAATTC GCTAGCCGAGTTG AGCCGGGCGCGGT ACGGGTACTGGTA TGTGTGGGGATCC GAGCTCCACGTG-30 50 -GAGGGCAACGA GTGTTTATAGA-30 50 -GAGGGCAACGA GTGTTTATAGA-30

Aptamer sequences

0.2– 17.5 nM

Ultravioletvisible

40 min

0.06 nM 1.7 μM

0.1–60 nM Ultravioletvisible Ultravioletvisible

12.86– 257.14 μM 1–16 μM

60 min

1.49 nM

1–100 nM

46 nM

0.2 pg/ mL

Ultravioletvisible Electrochemical

Ultravioletvisible

100 min

8 min

30 min

15 min

1–500 ng/ mL 0.01– 1000 μg/ mL 0.5– 30,000 pg/ mL

45 min

30 min

0.008 μM

0.7 ng/ mL 10 ng/mL

60 min

30 min

90 min

Detection time

0.05 nM

10 ng/mL

30 pg/mL

Limit of detection

Ultravioletvisible Ultravioletvisible

0.01– 0.25 μM

10– 250 ng/mL

Ultravioletvisible

Ultravioletvisible

0.5– 100 ng/mL

Detection range

Ultravioletvisible

Technique

Table 5.3 List of NanoZymes based methods for the detection of organic pollutants using aptamers

(continued)

Sharma et al. (2014) Wang et al. (2016a) Tan et al. (2017) Zhang et al. (2020b)

Luan et al. (2017)

Wang et al. (2017a) Yan et al. (2017)

Yuan et al. (2016)

Hu et al. (2015)

Sun et al. (2018)

Wang et al. (2016b)

References

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . . 125

Pesticides

Category

Fe/Mn metal-organicframeworks and Au nanoparticles Platinum nanoparticles

Graphene/GNPs hybrids

Fe-based MOF (Fe-MIL-53)

Sulfadimethoxine

Oxytetracycline

Chloramphenicol

Tyrosine capped silver nanoparticles

GNPs

Chlorpyrifos

Acetamiprid

Kanamycin

Nanozyme

Target

Table 5.3 (continued)

Peroxidase

Peroxidase

Peroxidase

Peroxidase

Peroxidase

Peroxidase

Activity

DNA

DNA

DNA

DNA

DNA

DNA

Type of aptamer

0.1– 10 ppm

35– 210 ppm

Ultravioletvisible

Ultravioletvisible

50– 200 nM

0.17 to 0.50 μM

Ultravioletvisible

Ultravioletvisible

0.2–50 pM

0.54– 41.58 μg/L

Detection range

Electrochemical

Ultravioletvisible

ATTCGCTAGCCCCC CGGCAGGCCACGG CTTGGGTTGGTCCC ACTGCGCGTGGAT CCGAGCTCCACGT G-30 50 -GAGGGCAACGA GTGTTTATAGA-30 50 -TGGGGGTTGAGG CTAAGCCG A-30 50 -CGTACGGAATTC GCTAGCCGAGTT-G AGCCGGGCGCGGT ACGGGTACTGGTA TGTGTGGGGATCC GAGCTCCACGTG-30 50 -ACTTCAGTGAGT TGTCCCACGGTCG GCGAGTCGGTGGT AG-30 50 -CCTGCCACGCTC CGCAAGCTTAGGG TTACGCCTGCAGC GATTCTGATCGCG CTGCTGGTAATCCT TCTTTAAGCTTGGC ACCCGCATCGT-30 50 -TGTAATTTGTCT

Technique

Aptamer sequences

0.1 ppm

11.3 ppm

25 nM

91 nM

0.063 pM

0.35 μg/L

Limit of detection

10 min

10 min

90 min

60 min

6h

50 min

Detection time

Weerathunge et al. (2014)

Weerathunge et al. (2019a)

Li et al. (2019)

Zeng et al. (2018) Yuan et al. (2017)

Dang and Zhao (2020)

References

126 N. Kalyani et al.

Dyes

GNPs

GNPs

Acetamiprid

Malachite green

Hemin-functionalized reduced graphene oxide

Acetamiprid

Peroxidase

Peroxidase

Peroxidase

RNA

DNA

DNA

50 -TGTAATTTGTCT GCAGCGGTTCTTG ATCGCTGACACCA TATTATGAAGA-30 50 -TGTAATTTGTCT GCAGCGGTTCTTG ATCGCTGACACCA TATTATGAAGA-30 50 -UCCCGACUGGA ACAGGUAACGAAU GGA 30

GCAGCGGTTCTTG ATCGCTGACACCA TATTATGAAGA-30

Ultravioletvisible

Ultravioletvisible

Ultravioletvisible

10– 500 nM

10– 160 μg/L

100 nM10 μM

75 min

90 min

1.02 μg/L

1.8 nM

60 min

40 nM

(Zhao et al. 2019)

Yang et al. (2017)

Yang et al. (2015b)

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . . 127

128

N. Kalyani et al.

Fig. 5.5 Colorimetric detection of ochratoxin A by Au@Fe3O4 with enhanced peroxidase activity. The blocked activity of Au@Fe3O4 can be recovered in the presence of ochratoxin A due to a high affinity of aptamer towards ochratoxin A as compared to complementary DNA. (Reprinted with permission of Elsevier from reference (Wang et al. 2016b); Copyright 2016)

harvest loss. At the same time, their exposure to humankind may lead to harmful effects on the nervous system, reproductive system, and immune system and also causes cancer (Wang et al. 2009; Jarošová et al. 2015; Riberi et al. 2018). In some cases, toxin detection can be utilized to test the presence of secreting pathogens indirectly. Thus, innovative detection of toxins with a simple, rapid, and easy method is needed. Different NanoZymes based aptasensor have been proposed for the colorimetric detection of toxins, which are listed in Table 5.3 (Hu et al. 2015; Taghdisi et al. 2018; Tian et al. 2019). A magnetic nanoparticles based sensor have been constructed by Wang et al. to detect ochratoxin A (Wang et al. 2016b). GNPs doped Fe3O4 nanoparticles (Au@Fe3O4) not only displayed synergistically increased peroxidase activity but also used for the magnetic separation to decrease background signal. Synthesized Au@Fe3O4 has abundant polyethylene glycol molecules on the surface, making it easier to functionalize with (3-aminopropyl) triethoxysilane to provide an amino terminated layer for adding glutaraldehyde. The free aldehyde group of this glutaraldehyde was used for the immobilization of amino-modified complementary DNA via covalent bonding. Afterward, glass beads labeled aptamer was hybridized with complementary DNA, which results in a reduction in the catalytic activity of Au@Fe3O4. The activity was recovered when exposed to ochratoxin A due to the removal of glass beads labeled aptamer (Fig. 5.5). Au@Fe3O4 can be easily

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

129

separated under the influence of the magnetic field, and their activity can be visualized by the oxidation of 3,30 ,5,50 -tetramethylbenzidine in the presence of H2O2 in acetate buffer. The highest catalytic activity was observed at 40  C in acidic conditions (pH 4.0). The sensitivity of the sensor for ochratoxin A is within the range of 0.5–100 ng/mL, and the limit of detection is 30 pg/mL. The selectivity of the sensor was also tested against ochratoxin B, fumonisin B1, and aflatoxin, and the response was not significant in comparison to ochratoxin A. A colorimetric assay has been developed by Sun et al. for the detection of zearalenone (Sun et al. 2018). The assay is based on the inhibition of peroxidase activity of aptamer bound GNPs, and they regain the peroxidase activity in the presence of zearalenone. This is due to the strong affinity between aptamer and zearalenone, which renders aptamer to leave GNPs. The peroxidase activity was monitored by oxidation of a colorless compound TMB into a dark blue colored product in the presence of H2O2. The reaction system was quantified by recording the absorbance at 630 nm. Good linearity was reported in the range 10–250 ng/mL with the detection limit of 10 ng/mL. It was also tested if the presence of other species (aflatoxin B1, ochratoxin A, Ca2+, Na+, Mg2+ and, Zn2+) affect the sensitivity of the assay and the change in signal was negligible compared to zearalenone one. The assay was also checked for real sample analysis for which spiked corn and corn oil was used, and recovery of 92–115% was reported.

5.4.3.2

Antibiotics

Antibiotics use in excess and in perverse way results in their easy penetration in the environment (Berendonk et al. 2015). Their residues present in the atmosphere poses grave danger to the ecosystem by causing an allergic reaction in people and drug resistance in bacteria (Barton 2000; Zhang et al. 2012; Solensky 2012; Yuan et al. 2017). It is getting challenging to treat life-threatening diseases like pneumonia, tuberculosis, gonorrhea, and salmonellosis due to antimicrobial resistance. World Health Organization has projected an additional health expense of 1.2 trillion USD per year by 2050 because of antimicrobial resistance (World Health Organization 2017). Besides this, toxic effects due to antibiotics include bone marrow depression, cancer, cardiovascular diseases, dermatological diseases, and aplastic anemia (Zhai et al. 2015; Zamora-Gálvez et al. 2016). Therefore, researchers are working on the realization of fast, reliable, and sensitive methods for the detection of antibiotics, and several NanoZymes-based sensors have been developed for the same (Yan et al. 2017; Yuan et al. 2017; Zhang et al. 2020b). Zhu and colleagues have constructed a self-powered photoelectrochemical sensor for the detection of chloramphenicol (Zhu et al. 2019). The sensor is based on extremely thin platinum-nickel nanowires having peroxidase mimetic activity and benzene-ring doped graphitic carbon nitride (BR-CN) as NanoZymes and photoactive material, respectively. Aptasensor consists of fluorine-doped tin oxide (FTO) coated with BR-CN, further coated with chitosan and amine-functionalized complementary DNA (complementary sequence to chloramphenicol aptamer) using

130

N. Kalyani et al.

Fig. 5.6 Platinum-Nickel nanozyme based photoelectrochemical aptasensor for the detection of chloramphenicol. Biotin coated aptamer in the presence of chloramphenicol deserts the complementary DNA and prevents the immobilization of streptavidin-conjugated PtNi nanowire, which in turn inhibits the formation of benzo-4-chlorohexadienone (4-CD), resulting in less catalytic precipitation and high photocurrent. (Reprinted with permission of Elsevier from reference (Zhu et al. 2019); Copyright 2019)

glutaraldehyde as a cross-linking agent. After the hybridization of biotinylated chloramphenicol aptamer (Bio-Aptamer), streptavidin functionalized Pt-Ni nanowires (SA-PtNi) were immobilized on the electrode by streptavidin-biotin conjugation. If chloramphenicol is present, chloramphenicol aptamer detaches from the electrode and prevents the Pt-Ni nanowires’ immobilization due to the absence of biotin (Fig. 5.6). These Pt-Ni nanowires oxidize the 4-chloro-1-naphthol (4-CN) to benzo-4-chlorohexadienone (4-CD) in the presence of hydrogen peroxide, which forms an insoluble precipitate on the surface of the electrode and consequently, leading to a reduction in photocurrent. The higher the amount of chloramphenicol in the sample, the lower the immobilization of Pt-Ni nanowires on the electrodes, which lower the catalytic precipitation on the electrode resulting in high photocurrent. The sensor displayed a wide detection range for chloramphenicol from 0.1 pM to 100 nM, along with a very low detection limit of 26 fM. On testing of this sensor for real spiked samples such as milk, water and, pig urine, recovery of 99–102% was obtained.

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

131

Fig. 5.7 Electrochemical sensor for the detection of kanamycin using GNPs as peroxidase mimetics. The inhibited peroxidase activity of GNPs recovers in the presence of kanamycin due to the higher affinity of aptamer towards kanamycin, resulting in a high amount of reduced tyrosine and higher current. (Reprinted with permission of Elsevier from reference (Wang et al. 2016a); Copyright 2016)

Wang et al. have introduced an electrochemical aptasensor based on GNPs for the detection of kanamycin (Wang et al. 2016a). Tyrosine capped GNPs were used as peroxidase mimics, which oxidizes thionine in the presence of H2O2, and the oxidized thionine gets electrochemically reduced on the electrode. The equations can describe the electrocatalytic reactions: H2 O2 þ thioinie ðredÞ ! H2 O þ thioinie ðoxÞ 

GNPs þ

thioinie ðoxÞ þ 2e þ 2H

! thioinie ðredÞ

electrode

A distinct reduction peak of thionine can be recorded by differential pulse voltammetry. Aptamer blocks this reaction by covering the surface of GNPs and inhibiting their peroxidase activity, resulting in a low signal, which is measured in terms of current. Since aptamer has a higher affinity towards kanamycin, in its presence, aptamer gets attached to it, and peroxidase activity of GNPs recovers, resulting in a high amount of signal (Fig. 5.7). The intensity of the signal is directly proportional to the concentration of kanamycin. The sensor showed an extremely high sensitivity for kanamycin within the range of 0.1–60 nM with the detection limit of 60 pM.

132

5.4.3.3

N. Kalyani et al.

Pesticides

Pesticides can persist in the environment for a very long time (in years) in soil and water. For example, atrazine was found in groundwater samples in Germany 18 years after a ban on its use (Jablonowski et al. 2011). Environmental and health concerns are increasing over the world for the use of pesticides leading to strict regulations and monitoring. Despite the classification of some pesticides as highly hazardous by the world health organization, they are still in use in many developing countries (Jirasirichote et al. 2017; Okoroiwu and Iwara 2018). Exposure to harmful pesticides majorly causes serious damage to the nervous system due to the inhibition of acetylcholine esterase (Verma and Bhardwaj 2015; Kalyani et al. 2020). Pesticides also cause toxicity of the immune system, reproductive system, and birth defects (Garry et al. 2002; Abhilash and Singh 2009). Hence, there is a vital requirement of easy, rapid, and cost-effective detection of pesticides. A colorimetric aptasensor was reported by Yang at el. for the detection of acetamiprid by utilizing the catalytic activity of gold nanoparticles (Yang et al. 2017). Aptamer inhibits the peroxidase activity of GNPs by increasing the negative charge density on them because of the DNA backbone, which is negatively charged. If the acetamiprid is present, aptamer binds to acetamiprid, and their complex interacts with GNPs via adsorption energy of nucleobases. This results in enhancement of catalytic activity and can be visualized by chromogenic oxidation of 2,20 -azino-bis (3-ethyl benzothiazoline-6-sulfonic acid) (ABTS) in the presence of H2O2, resulting in a green-colored product having absorption maxima at 735 nm (Fig. 5.8). The sensor showed sensitive detection within the range of 10–160 μg/L and the detection limit of 1.02 μg/L. There was no response observed in the presence of other pesticides like chlorpyrifos, profenophos, phoxim, phorate, dipterex, dimethoate, dichlorvos, methyl parathion, and isocarbophos. Detection of an organophosphorus pesticide, chlorpyrifos have been demonstrated by Weerathunge and coworkers by employing the tyrosine-capped silver nanoparticles as peroxidase mimetics (Weerathunge et al. 2019a). The non-covalent binding of aptamer with silver nanoparticles blocks their nanozyme activity. When the aptamer-nanozyme complex is exposed to chlorpyrifos, aptamer dissociates from the surface of silver nanoparticles resulting in regenerating their nanozymatic activity (Fig. 5.9). This activity can be monitored by the oxidation of TMB in the presence of H2O2 and recording the absorbance at 650 nM. The proposed sensor can successfully detect the chlorpyrifos within the range of 35–210 ppm, and the limit of detection is 11.3 ppm with very fast response time (2 min). The sensor has shown high selectivity towards chlorpyrifos as compared to various organophosphorus pesticides such as chlorpyrifos, monocrotophos, azamethiphos, diazinon, methamidophos, phorate and dichlorvos and other pesticides like aldicarb, captan, mancozeb, clothianidin, and thiamethoxam. The detection of chlorpyrifos in spiked water samples yield 98–102% recovery.

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

133

Fig. 5.8 Mechanism of colorimetric aptasensor based on the enhanced catalytic activity of GNPs to detect acetamiprid. Aptamer alone inhibits the peroxidase activity of GNPs. In contrast, aptameracetamiprid complex interacts with GNPs and enhances their peroxidase activity towards the oxidation of ABTS in the presence of H2O2. (Reprinted with permission of Royal Society of Chemistry from reference (Yang et al. 2017); Copyright 2017)

5.4.3.4

Dyes

Due to the extensive use of organic dyes in different industries such as textiles, paper, printing, cosmetics, paint, and tannery, they are one of the most common pollutants being discharged into water and that too without any treatment (He et al. 2018). It is really difficult to degrade them due to their complex aromatic structure and are majorly removed by adsorption from the wastewater (Sajid et al. 2018). Their exposure poses serious health risks due to their stability and toxicity and can cause allergy, irritation, cancer, and dermatitis (Capanema et al. 2018). Malachite green is used in aquaculture and lethal for aquatic organisms because of abnormalities in the growth and reproduction and damage to tissues and organs (Bergwerff and Scherpenisse 2003; Srivastava et al. 2004). Zhao et al. have reported GNPs based colorimetric sensor for the detection of malachite green (Zhao et al. 2019). A cationic surfactant, cetyltrimethylammonium bromide (CTAB) inhibits the peroxidase activity of GNPs by inducing aggregation of negatively charged GNPs. An RNA aptamer against malachite green was used as the sensing element which binds to GNPs. This interaction between RNA and GNPs prevents the aggregation of GNPs in the presence of CTAB and restores the peroxidase activity of GNPs. In the presence of malachite green, the RNA aptamer leaves the surface of GNPs, and renders the GNPs for aggregation with CTAB, again leading to a decrease in peroxidase activity. The peroxidase activity was measured by oxidation of

134

N. Kalyani et al.

Fig. 5.9 Silver nanoparticles based aptasensor for the detection of chlorpyrifos pesticide. The peroxidase activity of silver nanoparticles blocked by aptamer is recovered in the presence of chlorpyrifos pesticide and realized by oxidation of TMB in the presence of H2O2. (Reprinted with permission of Elsevier from reference (Weerathunge et al. 2019a); Copyright 2019)

3,30 ,5,50 -tetramethylbenzidine (TMB), which, when oxidized in the presence of H2O2, changes from colorless to dark blue color. This change in color was monitored spectrophotometrically and showed linearity in the range from 10 to 500 nM with a limit of detection of 1.8 nM. The assay was also tested for the recovery of malachite green in spiked aquaculture water samples and recoveries were obtained within 80% and 120%.

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

5.5

135

Summary and Future Prospects

The combination of the aptamer nanozyme duo holds great potential for the development of various environmental pollutant sensors. The duo offers a very lucid, facile, affordable mechanism that can be readily adapted on a range of existing sensing platforms like optical and electrochemical sensing, etc. The potential of the duo has been extensively gauged and validated in the last decade, with numerous studies bolstering their utility in the pollutant sensing field. The field is also poised to grow due to the extensive thrust given in the development of new aptamers against various environmental pollutants supplemented with the development of novel NanoZymes. As the awareness about the detrimental effects of various pollutants on human health is ever increasing, the demand for affordable on-site detection of these pollutants is bound to increase. In such a scenario, the advancement in the field of nanozyme and aptamer will be extensively used in the development of novel sensors for environmental pollutants. Acknowledgments TKS acknowledges the Department of Biotechnology (DBT), Government of India for supporting past and ongoing research in Aptamer Technology and Diagnostics Laboratory. Neeti Kalyani acknowledges the Science and Engineering Research Board, Department of Science & Technology, Government of India for financial support vide reference no PDF/2018/ 002186 under National Postdoctoral Fellowship Scheme.

References Abhilash PC, Singh N (2009) Pesticide use and application: an Indian scenario. J Hazard Mater 165:1–12. https://doi.org/10.1016/j.jhazmat.2008.10.061 Aldewachi H, Chalati T, Woodroofe MN et al (2018) Gold nanoparticle-based colorimetric biosensors. Nanoscale 10:18–33. https://doi.org/10.1039/C7NR06367A Alhogail S, Suaifan GARY, Zourob M (2016) Rapid colorimetric sensing platform for the detection of Listeria monocytogenes foodborne pathogen. Biosens Bioelectron 86:1061–1066. https://doi. org/10.1016/j.bios.2016.07.043 Ali H, Khan E (2019) Trophic transfer, bioaccumulation, and biomagnification of non-essential hazardous heavy metals and metalloids in food chains/webs – concepts and implications for wildlife and human health. Hum Ecol Risk Assess 25:1353–1376. https://doi.org/10.1080/ 10807039.2018.1469398 Ammann AA (2002) Speciation of heavy metals in environmental water by ion chromatography coupled to ICP–MS. Anal Bioanal Chem 372:448–452. https://doi.org/10.1007/s00216-0011115-8 Appenzeller BMR, Tsatsakis AM (2012) Hair analysis for biomonitoring of environmental and occupational exposure to organic pollutants: state of the art, critical review and future needs. Toxicol Lett 210:119–140. https://doi.org/10.1016/j.toxlet.2011.10.021 Aragay G, Merkoçi A (2012) Nanomaterials application in electrochemical detection of heavy metals. Electrochim Acta 84:49–61. https://doi.org/10.1016/j.electacta.2012.04.044 Asif S, Chaudhari A, Gireesh-Babu P et al (2016) Immobilization of fluorescent whole cell biosensors for the improved detection of heavy metal pollutants present in aquatic environment. Mater Today Proc 3:3492–3497. https://doi.org/10.1016/j.matpr.2016.10.032

136

N. Kalyani et al.

Babamiri B, Salimi A, Hallaj R (2018) Switchable electrochemiluminescence aptasensor coupled with resonance energy transfer for selective attomolar detection of Hg2+ via CdTe@CdS/ dendrimer probe and Au nanoparticle quencher. Biosens Bioelectron 102:328–335. https:// doi.org/10.1016/j.bios.2017.11.034 Barton MD (2000) Antibiotic use in animal feed and its impact on human healt. Nutr Res Rev 13:279–299. https://doi.org/10.1079/095442200108729106 Bazin I, Tria SA, Hayat A, Marty JL (2017) New biorecognition molecules in biosensors for the detection of toxins. Biosens Bioelectron 87:285–298 Berendonk TU, Manaia CM, Merlin C et al (2015) Tackling antibiotic resistance: the environmental framework. Nat Rev Microbiol 13:310–317. https://doi.org/10.1038/nrmicro3439 Bergwerff AA, Scherpenisse P (2003) Determination of residues of malachite green in aquatic animals. J Chromatogr B 788:351–359. https://doi.org/10.1016/S1570-0232(03)00042-4 Bock LC, Griffin LC, Latham JA et al (1992) Selection of single-stranded DNA molecules that bind and inhibit human thrombin. Nature 355:564–566. https://doi.org/10.1038/355564a0 Bülbül G, Hayat A, Andreescu S (2016) ssDNA-functionalized nanoceria: a redox-active aptaswitch for biomolecular recognition. Adv Healthc Mater 5:822–828. https://doi.org/10. 1002/adhm.201500705 Capanema NSV, Mansur AAP, Mansur HS et al (2018) Eco-friendly and biocompatible crosslinked carboxymethylcellulose hydrogels as adsorbents for the removal of organic dye pollutants for environmental applications. Environ Technol 39:2856–2872. https://doi.org/10.1080/ 09593330.2017.1367845 Chatterjee B, Kalyani N, Das S et al (2019) Nano-realm for point-of-care (POC) bacterial diagnostics. In: Methods in microbiology, 1st edn. Elsevier, New York, pp 19–42 Chatterjee B, Jyoti Das S, Anand A, Kumar Sharma T (2020) Nanozymes and aptamer-based biosensing. Mater Sci Energy Technol 3:127–135. https://doi.org/10.1016/j.mset.2019.08.007 Cheah S-E, Bulitta JB, Li J, Nation RL (2014) Development and validation of a liquid chromatography–mass spectrometry assay for polymyxin B in bacterial growth media. J Pharm Biomed Anal 92:177–182. https://doi.org/10.1016/j.jpba.2014.01.015 Chen J, Shu Y, Li H et al (2018) Nickel metal-organic framework 2D nanosheets with enhanced peroxidase nanozyme activity for colorimetric detection of H2O2. Talanta 189:254–261. https:// doi.org/10.1016/j.talanta.2018.06.075 Chen J, Meng H, Tian Y et al (2019) Recent advances in functionalized MnO2 nanosheets for biosensing and biomedicine applications. Nanoscale Horizons 4:321–338. https://doi.org/10. 1039/C8NH00274F Chengalroyen MD, Beukes GM, Gordhan BG et al (2016) Detection and quantification of differentially culturable tubercle bacteria in sputum from patients with tuberculosis. Am J Respir Crit Care Med 194:1532–1540. https://doi.org/10.1164/rccm.201604-0769OC Civit L, Taghdisi SM, Jonczyk A et al (2018) Systematic evaluation of cell-SELEX enriched aptamers binding to breast cancer cells. Biochimie 145:53–62. https://doi.org/10.1016/j. biochi.2017.10.007 Crawford M (2003) Peptide aptamers: tools for biology and drug discovery. Briefings Funct Genomics Proteomics 2:72–79. https://doi.org/10.1093/bfgp/2.1.72 Crivianu-Gaita V, Thompson M (2016) Aptamers, antibody scFv, and antibody Fab’ fragments: an overview and comparison of three of the most versatile biosensor biorecognition elements. Biosens Bioelectron 85:32–45. https://doi.org/10.1016/j.bios.2016.04.091 Crutzen PJ (2002) Geology of mankind. Nature 415:23. https://doi.org/10.1038/415023a Cui L, Wu J, Li J, Ju H (2015) Electrochemical sensor for lead cation sensitized with a DNA functionalized porphyrinic metal-organic framework. Anal Chem 87:10635–10641. https://doi. org/10.1021/acs.analchem.5b03287 Cui Q, Fang T, Huang Y et al (2017) Evaluation of bacterial pathogen diversity, abundance and health risks in urban recreational water by amplicon next-generation sequencing and quantitative PCR. J Environ Sci 57:137–149. https://doi.org/10.1016/j.jes.2016.11.008

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

137

Dang X, Zhao H (2020) Bimetallic Fe/Mn metal-organic-frameworks and Au nanoparticles anchored carbon nanotubes as a peroxidase-like detection platform with increased active sites and enhanced electron transfer. Talanta 210:120678. https://doi.org/10.1016/j.talanta.2019. 120678 Das R, Dhiman A, Kapil A et al (2019) Aptamer-mediated colorimetric and electrochemical detection of Pseudomonas aeruginosa utilizing peroxidase-mimic activity of gold NanoZyme. Anal Bioanal Chem 411:1229–1238 Das R, Chaterjee B, Kapil A, Sharma TK (2020) Aptamer-NanoZyme mediated sensing platform for the rapid detection of Escherichia coli in fruit juice. Sens Bio-Sensing Res 27:100313. https://doi.org/10.1016/j.sbsr.2019.100313 Dehghani Z, Hosseini M, Mohammadnejad J et al (2018) Colorimetric aptasensor for Campylobacter jejuni cells by exploiting the peroxidase like activity of Au@Pd nanoparticles. Microchim Acta 185:448. https://doi.org/10.1007/s00604-018-2976-2 Dembowski SK, Bowser MT (2018) Microfluidic methods for aptamer selection and characterization. Analyst 143:21–32. https://doi.org/10.1039/c7an01046j Dhiman A, Kalra P, Bansal V et al (2017) Aptamer-based point-of-care diagnostic platforms. Sensors Actuators B Chem 246:535–553 Dunn MR, Jimenez RM, Chaput JC (2017) Analysis of aptamer discovery and technology. Nat Chem 1:1–16. https://doi.org/10.1038/s41570017-0076 Famulok M (1999) Oligonucleotide aptamers that recognize small molecules. Curr Opin Struct Biol 9:324–329. https://doi.org/10.1016/S0959-440X(99)80043-8 Fernandes Azevedo B, Barros Furieri L, Peçanha FM et al (2012) Toxic effects of mercury on the cardiovascular and central nervous systems. J Biomed Biotechnol 2012:1–11. https://doi.org/10. 1155/2012/949048 Gahlaut SK, Kalyani N, Sharan C et al (2019) Smartphone based dual mode in situ detection of viability of bacteria using Ag nanorods array. Biosens Bioelectron 126:478–484 Gao L, Zhuang J, Nie L et al (2007) Intrinsic peroxidase-like activity of ferromagnetic nanoparticles. Nat Nanotechnol 2:577–583. https://doi.org/10.1038/nnano.2007.260 Gao N, Dong K, Zhao A et al (2016) Polyoxometalate-based nanozyme: design of a multifunctional enzyme for multi-faceted treatment of Alzheimer’s disease. Nano Res 9:1079–1090. https://doi. org/10.1007/s12274-016-1000-6 Garry VF, Harkins ME, Erickson LL et al (2002) Birth defects, season of conception, and sex of children born to pesticide applicators living in the Red River Valley of Minnesota, USA. Environ Health Perspect 110:441–449. https://doi.org/10.1289/ehp.02110s3441 Gobas FAPC, Zhang X, Wells R (1993) Gastrointestinal magnification: the mechanism of biomagnification and food chain accumulation of organic chemicals. Environ Sci Technol 27:2855–2863. https://doi.org/10.1021/es00049a028 Guan Z, Eichler J (2011) Liquid chromatography/tandem mass spectrometry of dolichols and polyprenols, lipid sugar carriers across evolution. Biochim Biophys Acta Mol Cell Biol Lipids 1811:800–806. https://doi.org/10.1016/j.bbalip.2011.04.009 He K, Chen G, Zeng G et al (2018) Three-dimensional graphene supported catalysts for organic dyes degradation. Appl Catal B Environ 228:19–28. https://doi.org/10.1016/j.apcatb.2018.01. 061 Hu J, Ni P, Dai H et al (2015) Aptamer-based colorimetric biosensing of abrin using catalytic gold nanoparticles. Analyst 140:3581–3586. https://doi.org/10.1039/c5an00107b Huang L, Chen K, Zhang W et al (2018) ssDNA-tailorable oxidase-mimicking activity of spinel MnCo2O4 for sensitive biomolecular detection in food sample. Sensors Actuators B Chem 269:79–87. https://doi.org/10.1016/j.snb.2018.04.150 Huang Y, Ren J, Qu X (2019) Nanozymes: classification, catalytic mechanisms, activity regulation, and applications. Chem Rev 119:4357–4412. https://doi.org/10.1021/acs.chemrev.8b00672 Imhof HK, Laforsch C, Wiesheu AC et al (2016) Pigments and plastic in limnetic ecosystems: a qualitative and quantitative study on microparticles of different size classes. Water Res 98:64–74. https://doi.org/10.1016/j.watres.2016.03.015

138

N. Kalyani et al.

Jablonowski ND, Schäffer A, Burauel P (2011) Still present after all these years: persistence plus potential toxicity raise questions about the use of atrazine. Environ Sci Pollut Res 18:328–331. https://doi.org/10.1007/s11356-010-0431-y Jarošová B, Javůrek J, Adamovský O, Hilscherová K (2015) Phytoestrogens and mycoestrogens in surface waters – their sources, occurrence, and potential contribution to estrogenic activity. Environ Int 81:26–44. https://doi.org/10.1016/j.envint.2015.03.019 Jayasena SD (1999) Aptamers: an emerging class of molecules that rival antibodies in diagnostics. Clim Chem 45:1628–1650 Jiang D, Ni D, Rosenkrans ZT et al (2019) Nanozyme: new horizons for responsive biomedical applications. Chem Soc Rev 48:3683–3704. https://doi.org/10.1039/c8cs00718g Jiao Y, Jia H, Guo Y et al (2016) An ultrasensitive aptasensor for chlorpyrifos based on ordered mesoporous carbon/ferrocene hybrid multiwalled carbon nanotubes. RSC Adv 6:58541–58548. https://doi.org/10.1039/c6ra07735h Jirasirichote A, Punrat E, Suea-Ngam A et al (2017) Voltammetric detection of carbofuran determination using screen-printed carbon electrodes modified with gold nanoparticles and graphene oxide. Talanta 175:331–337. https://doi.org/10.1016/j.talanta.2017.07.050 Kalyani N, Goel S, Jaiswal S (2020) Point-of-care sensors for on-site detection of pesticides. In: Kumar Tuteja S, Arora D, Dilbaghi N, Lichtfouse E (eds) Nanosensors for environmental applications. Springer, Cham, pp 197–224 Karim MN, Anderson SR, Singh S et al (2018) Nanostructured silver fabric as a free-standing NanoZyme for colorimetric detection of glucose in urine. Biosens Bioelectron 110:8–15. https:// doi.org/10.1016/j.bios.2018.03.025 Kaur H, Chaterjee B, Bruno JG, Sharma TK (2019) Defining target product profiles (TPPs) for aptamer-based diagnostics. In: Advances in biochemical engineering/biotechnology. Springer, Berlin/Heidelberg, pp 1–12 Kelly BC, Gobas FAPC, McLachlan MS (2004) Intestinal absorption and biomagnification of organic contaminants in fish, wildlife, and humans. Environ Toxicol Chem 23:2324–2336. https://doi.org/10.1897/03-545 Kim YS, Jurng J (2013) A simple colorimetric assay for the detection of metal ions based on the peroxidase-like activity of magnetic nanoparticles. Sensors Actuators B Chem 176:253–257. https://doi.org/10.1016/j.snb.2012.10.052 Kraemer SA, Ramachandran A, Perron GG (2019) Antibiotic pollution in the environment: from microbial ecology to public policy. Microorganisms 7:1–24. https://doi.org/10.3390/ microorganisms7060180 Kuang H, Xing C, Hao C et al (2013) Rapid and highly sensitive detection of lead ions in drinking water based on a strip immunosensor. Sensors 13:4214–4224. https://doi.org/10.3390/ s130404214 Kumar S, Lodhi DK, Goel P et al (2015) A facile method for fabrication of buckled PDMS silver nanorod arrays as active 3D SERS cages for bacterial sensing. Chem Commun 51:12411–12414 Landrigan PJ, Fuller R, Acosta NJR et al (2018) The Lancet Commission on pollution and health. Lancet 391:462–512. https://doi.org/10.1016/S0140-6736(17)32345-0 Langley RL, Mort SA (2012) Human exposures to pesticides in the united states. J Agromed 17:300–315. https://doi.org/10.1080/1059924X.2012.688467 Lee EJ, Lim HK, Cho YS, Hah SS (2013) Peptide nucleic acids are an additional class of aptamers. RSC Adv 3:5828. https://doi.org/10.1039/c3ra40553b Li B, Chen D, Wang J et al (2015) MOFzyme: intrinsic protease-like activity of Cu-MOF. Sci Rep 4:6759. https://doi.org/10.1038/srep06759 Li J, Yu C, Y nan W et al (2019) Novel sensing platform based on gold nanoparticle-aptamer and Fe-metal-organic framework for multiple antibiotic detection and signal amplification. Environ Int 125:135–141. https://doi.org/10.1016/j.envint.2019.01.033 Lian Y, He F, Wang H, Tong F (2015) A new aptamer/graphene interdigitated gold electrode piezoelectric sensor for rapid and specific detection of Staphylococcus aureus. Biosens Bioelectron 65:314–319. https://doi.org/10.1016/j.bios.2014.10.017

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

139

Ligler FS, Taitt CR, Shriver-Lake LC et al (2003) Array biosensor for detection of toxins. Anal Bioanal Chem 377:469–477. https://doi.org/10.1007/s00216-003-1992-0 Liu P, Han L, Wang F et al (2016) Gold nanoprobe functionalized with specific fusion protein selection from phage display and its application in rapid, selective and sensitive colorimetric biosensing of Staphylococcus aureus. Biosens Bioelectron 82:195–203. https://doi.org/10.1016/ j.bios.2016.03.075 Loesche WJ, Lopatin DE, Stoll J et al (1992) Comparison of various detection methods for periodontopathic bacteria: can culture be considered the primary reference standard? J Clin Microbiol 30:418–426. https://doi.org/10.1128/JCM.30.2.418-426.1992 Luan Q, Gan N, Cao Y, Li T (2017) Mimicking an enzyme-based colorimetric aptasensor for antibiotic residue detection in milk combining magnetic loop-dna probes and cha-assisted target recycling amplification. J Agric Food Chem 65:5731–5740. https://doi.org/10.1021/acs.jafc. 7b02139 Mauldin RE, Primus TM, Buettgenbach TA et al (2006) A Simple HPLC method for the determination of chlorpyrifos in black oil sunflower seeds. J Liq Chromatogr Relat Technol 29:339–348. https://doi.org/10.1080/10826070500451863 Mounier J, Gouëllo A, Keravec M et al (2014) Use of denaturing high-performance liquid chromatography (DHPLC) to characterize the bacterial and fungal airway microbiota of cystic fibrosis patients. J Microbiol 52:307–314. https://doi.org/10.1007/s12275-014-3425-5 Nawab J, Khan S, Xiaoping W (2018) Ecological and health risk assessment of potentially toxic elements in the major rivers of Pakistan: general population vs. fishermen. Chemosphere 202:154–164. https://doi.org/10.1016/j.chemosphere.2018.03.082 Okoroiwu HU, Iwara IA (2018) Dichlorvos toxicity: a public health perspective. Interdiscip Toxicol 11:129–137. https://doi.org/10.2478/intox-2018-0009 Ou D, Sun D, Lin X et al (2019) A dual-aptamer-based biosensor for specific detection of breast cancer biomarker HER2 via flower-like nanozymes and DNA nanostructures. J Mater Chem B 7:3661–3669. https://doi.org/10.1039/c9tb00472f Ouyang H, Ling S, Liang A, Jiang Z (2018) A facile aptamer-regulating gold nanoplasmonic SERS detection strategy for trace lead ions. Sensors Actuators B Chem 258:739–744. https://doi.org/ 10.1016/j.snb.2017.12.009 Pandey PK, Kass PH, Soupir ML et al (2014) Contamination of water resources by pathogenic bacteria. AMB Express 4:51. https://doi.org/10.1186/s13568-014-0051-x Pang S, Yang T, He L (2016) Review of surface enhanced Raman spectroscopic (SERS) detection of synthetic chemical pesticides. TrAC Trends Anal Chem 85:73–82. https://doi.org/10.1021/ acsami.5b05838 Peng C, Hua M-Y, Li N-S et al (2019) A colorimetric immunosensor based on self-linkable dualnanozyme for ultrasensitive bladder cancer diagnosis and prognosis monitoring. Biosens Bioelectron 126:581–589. https://doi.org/10.1016/j.bios.2018.11.022 Pfeiffer F, Mayer G (2016) Selection and biosensor application of aptamers for small molecules. Front Chem 4:1–21. https://doi.org/10.3389/fchem.2016.00025 Qi Y, Xiu F-R, Yu G et al (2017) Simple and rapid chemiluminescence aptasensor for Hg2+ in contaminated samples: a new signal amplification mechanism. Biosens Bioelectron 87:439–446. https://doi.org/10.1016/j.bios.2016.08.022 Qian ZS, Shan XY, Chai LJ et al (2015) A fluorescent nanosensor based on graphene quantum dots–aptamer probe and graphene oxide platform for detection of lead (II) ion. Biosens Bioelectron 68:225–231. https://doi.org/10.1016/j.bios.2014.12.057 Reid R, Chatterjee B, Das SJ et al (2020) Application of aptamers as molecular recognition elements in lateral flow assays. Anal Biochem 593:113574. https://doi.org/10.1016/j.ab.2020.113574 Riberi WI, Tarditto LV, Zon MA et al (2018) Development of an electrochemical immunosensor to determine zearalenone in maize using carbon screen printed electrodes modified with multiwalled carbon nanotubes/polyethyleneimine dispersions. Sensors Actuators B Chem 254:1271–1277. https://doi.org/10.1016/j.snb.2017.07.113

140

N. Kalyani et al.

Rice KM, Walker EM, Wu M et al (2014) Environmental mercury and its toxic effects. J Prev Med Public Health 47:74–83. https://doi.org/10.3961/jpmph.2014.47.2.74 Rockström J, Steffen W, Noone K et al (2009) A safe operation space for humanity. Nature 461:472–475 Saha K, Agasti SS, Kim C et al (2012) Gold nanoparticles in chemical and biological sensing. Chem Rev 112:2739–2779. https://doi.org/10.1021/cr2001178 Sajid M, Nazal MK, Ihsanullah et al (2018) Removal of heavy metals and organic pollutants from water using dendritic polymers based adsorbents: a critical review. Sep Purif Technol 191:400–423. https://doi.org/10.1016/j.seppur.2017.09.011 Schüling T, Eilers A, Scheper T, Walter J (2018) Aptamer-based lateral flow assays. AIMS Bioeng 5:78–102. https://doi.org/10.3934/bioeng.2018.2.78 Seok Kim Y, Ahmad Raston NH, Bock Gu M (2016) Aptamer-based nanobiosensors. Biosens Bioelectron 76:2–19. https://doi.org/10.1016/j.bios.2015.06.040 Sharma TK, Ramanathan R, Weerathunge P et al (2014) Aptamer-mediated “turn-off/turn-on” nanozyme activity of gold nanoparticles for kanamycin detection. Chem Commun 50:15856–15859. https://doi.org/10.1039/c4cc07275h Sharma TK, Bruno JG, Cho WC (2016) The point behind translation of aptamers for point of care diagnostics. Aptamers Synth Antibodies 2:36–42 Sharma TK, Bruno JG, Dhiman A (2017) ABCs of DNA aptamer and related assay development. Biotechnol Adv 35:275–301 Shimizu FM, Braunger ML, Riul A (2019) Heavy metal/toxins detection using electronic tongues. Chemosensors 7:1–19. https://doi.org/10.3390/CHEMOSENSORS7030036 Sitko R, Turek E, Zawisza B et al (2013) Adsorption of divalent metal ions from aqueous solutions using graphene oxide. Dalton Trans 42:5682. https://doi.org/10.1039/c3dt33097d Solensky R (2012) Allergy to β-lactam antibiotics. J Allergy Clin Immunol 130:1442–1442.e5. https://doi.org/10.1016/j.jaci.2012.08.021 Song HJ, You S, Jia XH, Yang J (2015) MoS2 nanosheets decorated with magnetic Fe3O4 nanoparticles and their ultrafast adsorption for wastewater treatment. Ceram Int 41:13896–13902. https://doi.org/10.1016/j.ceramint.2015.08.023 Srivastava S, Sinha R, Roy D (2004) Toxicological effects of malachite green. Aquat Toxicol 66:319–329. https://doi.org/10.1016/j.aquatox.2003.09.008 Steffen W, Crutzen PJ, McNeill JR (2007) The anthropocene: are humans now overwhelming the great forces of nature. Am J Human Environ 36:614–621. https://doi.org/10.1579/0044-7447 (2007)36[614:TAAHNO]2.0.CO;2 Sun H, Yu L, Chen H et al (2015) A colorimetric lead (II) ions sensor based on selective recognition of G-quadruplexes by a clip-like cyanine dye. Talanta 136:210–214. https://doi.org/10.1016/j. talanta.2015.01.027 Sun S, Zhao R, Feng S, Xie Y (2018) Colorimetric zearalenone assay based on the use of an aptamer and of gold nanoparticles with peroxidase-like activity. Microchim Acta 185:1–7. https://doi. org/10.1007/s00604-018-3078-x Syedmoradi L, Daneshpour M, Alvandipour M et al (2017) Point of care testing: the impact of nanotechnology. Biosens Bioelectron 87:373–387. https://doi.org/10.1016/j.bios.2016.08.084 Taber KH, Hurley RA (2008) Mercury exposure: effects across the lifespan. J Neuropsychiatr Clin Neurosci 20:382–389. https://doi.org/10.1176/jnp.2008.20.4.iv Taghdisi SM, Danesh NM, Lavaee P et al (2015) A novel colorimetric triple-helix molecular switch aptasensor based on peroxidase-like activity of gold nanoparticles for ultrasensitive detection of lead (II). RSC Adv 5:43508–43514. https://doi.org/10.1039/C5RA06326D Taghdisi SM, Danesh NM, Ramezani M et al (2018) Novel colorimetric aptasensor for zearalenone detection based on nontarget-induced aptamer walker, gold nanoparticles, and exonucleaseassisted recycling amplification. ACS Appl Mater Interfaces 10:12504–12509. https://doi.org/ 10.1021/acsami.8b02349

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

141

Takenaka M, Okumura Y, Amino T et al (2017) DNA-duplex linker for AFM-SELEX of DNA aptamer against human serum albumin. Bioorg Med Chem Lett 27:954–957. https://doi.org/10. 1016/J.BMCL.2016.12.080 Tan B, Zhao H, Wu W et al (2017) Fe3O4-AuNPs anchored 2D metal-organic framework nanosheets with DNA regulated switchable peroxidase-like activity. Nanoscale 9:18699–18710. https://doi.org/10.1039/c7nr05541b Tchounwou PB, Yedjou CG, Patlolla AK, Sutton DJ (2012) Heavy metals toxicity and the environment. Springer, Basel Tian J (2019) Aptamer-based colorimetric detection of various targets based on catalytic Au NPs/Graphene nanohybrids. Sens Bio-Sensing Res 22:100258. https://doi.org/10.1016/j.sbsr. 2019.100258 Tian L, Qi J, Qian K et al (2018) Copper (II) oxide nanozyme based electrochemical cytosensor for high sensitive detection of circulating tumor cells in breast cancer. J Electroanal Chem 812:1–9. https://doi.org/10.1016/j.jelechem.2017.12.012 Tian F, Zhou J, Jiao B, He Y (2019) A nanozyme-based cascade colorimetric aptasensor for amplified detection of ochratoxin A. Nanoscale 11:9547–9555. https://doi.org/10.1039/ c9nr02872b Tran DT, Janssen KPF, Pollet J et al (2010) Selection and characterization of DNA aptamers for egg white lysozyme. Molecules 15:1127–1140. https://doi.org/10.3390/molecules15031127 UN: 200,000 die each year from pesticide poisoning | News | Al Jazeera Verma N, Bhardwaj A (2015) Biosensor technology for pesticides – a review. Appl Biochem Biotechnol 175:3093–3119. https://doi.org/10.1007/s12010-015-1489-2 Vilela D, González MC, Escarpa A (2012) Sensing colorimetric approaches based on gold and silver nanoparticles aggregation: chemical creativity behind the assay. A review. Anal Chim Acta 751:24–43. https://doi.org/10.1016/j.aca.2012.08.043 Wang L, Chen W, Xu D et al (2009) Simple, rapid, sensitive, and versatile SWNT – paper sensor for environmental toxin detection competitive with ELISA. Nano Lett 9:4147–4152. https://doi. org/10.1021/nl902368r Wang L, Liu X, Zhang Q et al (2012) Selection of DNA aptamers that bind to four organophosphorus pesticides. Biotechnol Lett 34:869–874. https://doi.org/10.1007/s10529-012-0850-6 Wang C, Liu C, Luo J et al (2016a) Direct electrochemical detection of kanamycin based on peroxidase-like activity of gold nanoparticles. Anal Chim Acta 936:75–82. https://doi.org/10. 1016/j.aca.2016.07.013 Wang C, Qian J, Wang K et al (2016b) Colorimetric aptasensing of ochratoxin A using Au@Fe3O4 nanoparticles as signal indicator and magnetic separator. Biosens Bioelectron 77:1183–1191. https://doi.org/10.1016/j.bios.2015.11.004 Wang X, Hu Y, Wei H (2016c) Nanozymes in bionanotechnology: from sensing to therapeutics and beyond. Inorg Chem Front 3:41–60. https://doi.org/10.1039/c5qi00240k Wang A, Zhao H, Chen X et al (2017a) A colorimetric aptasensor for sulfadimethoxine detection based on peroxidase-like activity of graphene/nickel@palladium hybrids. Anal Biochem 525:92–99. https://doi.org/10.1016/j.ab.2017.03.006 Wang S, Deng W, Yang L et al (2017b) Copper-based metal–organic framework nanoparticles with peroxidase-like activity for sensitive colorimetric detection of Staphylococcus aureus. ACS Appl Mater Interfaces 9:24440–24445. https://doi.org/10.1021/acsami.7b07307 Wang C, Tang G, Tan H (2018a) Colorimetric determination of mercury(II) via the inhibition by ssDNA of the oxidase-like activity of a mixed valence state cerium-based metal-organic framework. Microchim Acta 185:1–8. https://doi.org/10.1007/s00604-018-3011-3 Wang Q, Wei H, Zhang Z et al (2018b) Nanozyme: an emerging alternative to natural enzyme for biosensing and immunoassay. TrAC Trends Anal Chem 105:218–224. https://doi.org/10.1016/ j.trac.2018.05.012 Wang H, Wan K, Shi X (2019) Recent advances in nanozyme research. Adv Mater 31:1–10. https:// doi.org/10.1002/adma.201805368

142

N. Kalyani et al.

Wang J, Wang J, Zhou P et al (2020) Oligonucleotide-induced regulation of the oxidase-mimicking activity of octahedral Mn3O4 nanoparticles for colorimetric detection of heavy metals. Microchim Acta 187:1–11. https://doi.org/10.1007/s00604-019-4069-2 Weerathunge P, Ramanathan R, Shukla R et al (2014) Aptamer-controlled reversible inhibition of gold nanozyme activity for pesticide sensing. Anal Chem 86:11937–11941. https://doi.org/10. 1021/ac5028726 Weerathunge P, Behera BK, Zihara S et al (2019a) Dynamic interactions between peroxidasemimic silver NanoZymes and chlorpyrifos-specific aptamers enable highly-specific pesticide sensing in river water. Anal Chim Acta 1083:157–165. https://doi.org/10.1016/j.aca.2019.07. 066 Weerathunge P, Ramanathan R, Torok VA et al (2019b) Ultrasensitive colorimetric detection of murine norovirus using nanozyme aptasensor. Anal Chem 91:3270–3276. https://doi.org/10. 1021/acs.analchem.8b03300 Wei X, Zhou W, Sanjay ST et al (2019) Multiplexed instrument-free bar-chart spinchip integrated with nanoparticle-mediated magnetic aptasensors for visual quantitative detection of multiple pathogens. Anal Chem 90:9888–9896. https://doi.org/10.1021/acs.anal-chem.8b02055. Detailed Wellinghausen N, Siegel D, Gebert S, Winter J (2009) Rapid detection of Staphylococcus aureus bacteremia and methicillin resistance by real-time PCR in whole blood samples. Eur J Clin Microbiol Infect Dis 28:1001–1005. https://doi.org/10.1007/s10096-009-0723-7 World Health Organization (2017) Prioritization of pathogens to guide discovery, research and development of new antibiotics for drug resistant bacterial infections, including tuberculosis. WHO, Geneva World Health Organization (2019) Water, sanitation, hygiene and health. A primer for health professionals. WHO, Geneva, p 40 Wu S, Duan N, Qiu Y et al (2017) Colorimetric aptasensor for the detection of Salmonella enterica serovar typhimurium using ZnFe2O4-reduced graphene oxide nanostructures as an effective peroxidase mimetics. Int J Food Microbiol 261:42–48. https://doi.org/10.1016/j.ijfoodmicro. 2017.09.002 Xu F, Lu Q, Huang PJJ, Liu J (2019) Nanoceria as a DNase I mimicking nanozyme. Chem Commun 55:13215–13218. https://doi.org/10.1039/C9CC06782E Yan J, Huang Y, Zhang C et al (2017) Aptamer based photometric assay for the antibiotic sulfadimethoxine based on the inhibition and reactivation of the peroxidase-like activity of gold nanoparticles. Microchim Acta 184:59–63. https://doi.org/10.1007/s00604-016-1994-1 Yang L, Zhang Y, Li R et al (2015a) Electrochemiluminescence biosensor for ultrasensitive determination of ochratoxin A in corn samples based on aptamer and hyperbranched rolling circle amplification. Biosens Bioelectron 70:268–274. https://doi.org/10.1016/j.bios.2015.03. 067 Yang Z, Qian J, Yang X et al (2015b) A facile label-free colorimetric aptasensor for acetamiprid based on the peroxidase-like activity of hemin-functionalized reduced graphene oxide. Biosens Bioelectron 65:39–46. https://doi.org/10.1016/J.BIOS.2014.10.004 Yang W, Wu Y, Tao H et al (2017) Ultrasensitive and selective colorimetric detection of acetamiprid pesticide based on the enhanced peroxidase-like activity of gold nanoparticles. Anal Methods 9:5484–5493. https://doi.org/10.1039/c7ay01451a Yuan F, Zhao H, Zang H et al (2016) Three-dimensional graphene supported bimetallic nanocomposites with DNA regulated-flexibly switchable peroxidase-like activity. ACS Appl Mater Interfaces 8:9855–9864. https://doi.org/10.1021/acsami.6b00306 Yuan F, Zhao H, Wang X, Quan X (2017) Determination of oxytetracycline by a graphene – gold nanoparticle-based colorimetric aptamer sensor. Anal Lett 50:544–553. https://doi.org/10.1080/ 00032719.2016.1187160 Zamora-Gálvez A, Ait-Lahcen A, Mercante LA et al (2016) Molecularly Imprinted polymerdecorated magnetite nanoparticles for selective sulfonamide detection. Anal Chem 88:3578–3584. https://doi.org/10.1021/acs.analchem.5b04092

5 Aptamer Mediated Sensing of Environmental Pollutants Utilizing Peroxidase Mimic. . .

143

Zeng R, Luo Z, Zhang L, Tang D (2018) Platinum nanozyme-catalyzed gas generation for pressurebased bioassay using polyaniline nanowires-functionalized graphene oxide framework. Anal Chem 90:12299–12306. https://doi.org/10.1021/acs.analchem.8b03889 Zhai H, Liang Z, Chen Z et al (2015) Simultaneous detection of metronidazole and chloramphenicol by differential pulse stripping voltammetry using a silver nanoparticles/sulfonate functionalized graphene modified glassy carbon electrode. Electrochim Acta 171:105–113. https://doi.org/10. 1016/j.electacta.2015.03.140 Zhan S, Wu Y, Wang L et al (2016) A mini-review on functional nucleic acids-based heavy metal ion detection. Biosens Bioelectron 86:353–368. https://doi.org/10.1016/j.bios.2016.06.075 Zhang L, Li L (2016) Colorimetric thrombin assay using aptamer-functionalized gold nanoparticles acting as a peroxidase mimetic. Microchim Acta 183:485–490. https://doi.org/10.1007/s00604015-1674-6 Zhang Y, Cai X, Lang X et al (2012) Insights into aquatic toxicities of the antibiotics oxytetracycline and ciprofloxacin in the presence of metal: complexation versus mixture. Environ Pollut 166:48–56. https://doi.org/10.1016/j.envpol.2012.03.009 Zhang L, Huang R, Liu W et al (2016) Rapid and visual detection of Listeria monocytogenes based on nanoparticle cluster catalyzed signal amplification. Biosens Bioelectron 86:1–7. https://doi. org/10.1016/j.bios.2016.05.100 Zhang W, Liu QX, Guo ZH, Lin JS (2018) Practical application of aptamer-based biosensors in detection of low molecular weight pollutants in water sources. Molecules 23:12–16. https://doi. org/10.3390/molecules23020344 Zhang L, Qi Z, Zou Y et al (2019) Engineering DNA–nanozyme interfaces for rapid detection of dental bacteria. ACS Appl Mater Interfaces 11:30640–30647. https://doi.org/10.1021/acsami. 9b10718 Zhang J, Wu S, Ma L et al (2020a) Graphene oxide as a photocatalytic nuclease mimicking nanozyme for DNA cleavage. Nano Res 13:455–460. https://doi.org/10.1007/s12274-0202629-8 Zhang Z, Tian Y, Huang P, Wu FY (2020b) Using target-specific aptamers to enhance the peroxidase-like activity of gold nanoclusters for colorimetric detection of tetracycline antibiotics. Talanta 208:120342. https://doi.org/10.1016/j.talanta.2019.120342 Zhao B, Wu P, Zhang H, Cai C (2015) Designing activatable aptamer probes for simultaneous detection of multiple tumor-related proteins in living cancer cells. Biosens Bioelectron 68:763–770. https://doi.org/10.1016/j.bios.2015.02.004 Zhao C, Hong C, Lin Z et al (2019) Detection of Malachite Green using a colorimetric aptasensor based on the inhibition of the peroxidase-like activity of gold nanoparticles by cetyltrimethylammonium ions. Microchim Acta 322(1–8):186. https://doi.org/10.1007/ s00604-019-3436-3 Zheng A, Zhang X, Gao J et al (2016) Peroxidase-like catalytic activity of copper ions and its application for highly sensitive detection of glypican-3. Anal Chim Acta 941:87–93. https://doi. org/10.1016/j.aca.2016.08.036 Zhu X, Gao L, Tang L et al (2019) Ultrathin PtNi nanozyme based self-powered photoelectrochemical aptasensor for ultrasensitive chloramphenicol detection. Biosens Bioelectron 146:111756. https://doi.org/10.1016/j.bios.2019.111756 Zohora N, Kumar D, Yazdani M et al (2017) Rapid colorimetric detection of mercury using biosynthesized gold nanoparticles. Colloids Surfaces A Physicochem Eng Asp 532:451–457. https://doi.org/10.1016/j.colsurfa.2017.04.036 Zou Y, Duan N, Wu S et al (2018) Selection, identification, and binding mechanism studies of an ssDNA aptamer targeted to different stages of E. coli O157:H7. J Agric Food Chem 66:5677–5682. https://doi.org/10.1021/acs.jafc.8b01006 Zuloaga O, Navarro P, Bizkarguenaga E et al (2012) Overview of extraction, clean-up and detection techniques for the determination of organic pollutants in sewage sludge: a review. Anal Chim Acta 736:7–29. https://doi.org/10.1016/j.aca.2012.05.016

Chapter 6

Nanozyme-Based Sensors for Pesticide Detection Sanjana Naveen Prasad, Vipul Bansal, and Rajesh Ramanathan

Abstract Detection of pesticides in food and environmental samples is critical as pesticide residues compromise with human and animal health. The residual pesticides are also of significant environmental concern as they continue to accumulate in soil and water leading to change in the natural flora and fauna. Owing to these effects, several strategies have been proposed to detect and monitor their presence. Traditional strategies involve the use of expensive analytical tools that cannot be directly used on-site, require technical expertise, face high operating cost, and are time intensive. This has led to the recent interest in alternative strategies for more efficient pesticide detection. To this end, enzyme-mimicking catalytic activity of nanomaterials, more commonly referred to as the nanozyme activity, has been a topic of intensive research over the past decade. The potential applicability of nanozymes in environmental monitoring, diagnostics, sensing, microbial management, photodynamic therapy, and prodrug-activation therapy is being increasingly realised. Particularly, the importance of nanozymes in sensor development has seen tremendous interest, as previous sensors relying upon natural enzymes pose ongoing challenges in terms of stability and cost. Many such challenges can be mitigated by the use of nanozymes. The chapter outlines the strengths of nanozyme-based sensors for the detection of pesticides in food and environmental samples. An interesting aspect that has been discussed is the use of molecularly imprinted polymers and aptamers instead of antibodies for recognition of pesticides. Both of these recognition elements hold great promise in replacing our reliance on antibodies that rapidly denature and are cost prohibitive. The strength of nanozyme-based sensing platforms to be used on-site is also discussed, which is a significant advantage over conventional sensors that rely on bulky equipment. Lastly, the chapter discusses the next steps that needs

S. Naveen Prasad · V. Bansal (*) · R. Ramanathan (*) Ian Potter NanoBioSensing Facility, NanoBiotechnology Research Laboratory (NBRL), School of Science, Applied Chemistry and Environmental Science Discipline, RMIT University, Melbourne, VIC, Australia e-mail: [email protected]; [email protected]; [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 H. K. Daima et al. (eds.), Nanozymes for Environmental Engineering, Environmental Chemistry for a Sustainable World 63, https://doi.org/10.1007/978-3-030-68230-9_6

145

146

S. Naveen Prasad et al.

to be addressed in further expanding this important area of research and bringing laboratory-based nanozyme sensor technologies to the market. Keywords Nanozyme · Pesticide · Organophosphates · Sensors · Enzyme-mimic · Biosensors · Aptamers · Acetamiprid · Atrazine

6.1

Introduction

The World Health Organization defines pesticides as chemical compounds used to exterminate unwanted plants (weeds), fungi, insects, and rodents that may damage agricultural crops or spread diseases (WHO 2018). Since the 1960s, we have seen a substantial increase in the use of pesticides to not only control infections to agricultural plants but also to increase crop production to meet the ever-increasing food demand. However, only 1% of the applied pesticide gets delivered to the target. The potential adverse effects of the excess pesticide on the environment and human health has been a cause of ongoing concern (Nowell 2019). In fact, the high biological activity and toxicity of pesticides set them apart from other environmental contaminants (Yadav and Devi 2017). The safe use and appropriate disposal of pesticides is essential as they are toxic to most organisms, humans included (WHO 2018). The inevitable accumulation and subsequent entry of pesticide residues into our natural ecosystem pose a massive threat to human health (Mac Loughlin et al. 2018). Federal agencies such as the World Health Organization, the Food and Drug Administration, the Environmental Protection Agency, etc., have strict processes in place to monitor pesticide residues in soil, water, air, wildlife and humans. These guidelines are used to test raw agricultural crops, agricultural and urban soils, surface water, bed sediment and ambient air in suburban locales, processed and raw foods, animal feeds, meat, poultry and fish, blood serum, urine and adipose tissue in humans (Nowell 2019). The reason to monitor pesticide levels in such a wide testbed stems from the fact that exposure to pesticides can be through inhalation (pesticide vapor, dust or liquid spray), oral consumption (contaminated food and water) or dermal contact (skin contact or absorption into the body) (CDPR 2013). Inadvertent poisoning, exposure during application and pesticide drift from agricultural fields leads to acute toxicity while long term exposure to sub-lethal quantities of pesticide causes life-threatening conditions and chronic illness in humans which are much more difficult to determine through laboratory analysis (Yadav and Devi 2017). Farmers, formulators, mixers, loaders, and production workers are susceptible to chronic diseases due to prolonged exposure to pesticides leading to pesticide poisoning (Jayaraj et al. 2016). The consumption of contaminated food and water can also make the general population susceptible to its chronic effects including tumors; blood, nerve and endocrine disorders; and reproductive effects such as birth defects and toxicity to the foetus (Yadav and Devi 2017). In the case of severe organophosphate poisoning, it can lead to respiratory and neurological complications which can eventually lead

6 Nanozyme-Based Sensors for Pesticide Detection

147

to multiple organ distress syndrome and renal impairment (Agostini and Bianchin 2003). In addition to human health issues, overuse of pesticides can also have large implications on the environment. For instance, agricultural pesticide runoff into water bodies threatens resident organisms. The effects could range from a minor deviation in the normal functioning of the ecosystem to drastic effects including completely wiping out of native flora and fauna (Yadav and Devi 2017). Additionally, the mechanism of pesticide toxicity on non-target organisms (earthworms, pollinators, and predators) is often unknown. This makes monitoring of pesticides in a wide testbed and studying its toxicity on humans, animals and the environment all the more important (DeLorenzo et al. 2001). To develop effective remediation and mitigation strategies, it is important to first reliably detect and monitor pesticides in food, water (drinking and underground) and soil. A wide range of tools including mass spectroscopy, gas chromatography, highperformance liquid chromatography, capillary electrophoresis, surface plasmon resonance, surface-enhanced Raman spectroscopy, ultraviolet spectroscopy, fluorimetry, and immunoassays (Sulaiman et al. 2019; Songa and Okonkwo 2016; Kandjani et al. 2014, 2015; Zou et al. 2018, 2020; Ramanathan et al. 2013, 2015; Behera et al. 2018; Zohora et al. 2017; Sharma et al. 2015; Le et al. 2017; Chen et al. 2018; Muhamadali et al. 2016; Plowman et al. 2009; Arash et al. 2019) are used for detection. Some of the techniques are highly successful with the ability to detect trace residues of pesticides. However, they involve the need for expensive instrumentation, skilled personnel, sample pre-treatment and are time-consuming (Songa and Okonkwo 2016). Potential life-saving treatments are often delayed due to the waiting time on laboratory testing results (Silberman and Taylor 2019). The ability to perform on-site detection and/or access to rapid detection tools are required that can be directly applied to a wide range of sample testbeds to effectively monitor pesticide residues. To this end, a simple yet effective analytical platform that is the workhorse of analytical research is ELISA (enzyme-linked immunosorbent assay). In this assay, a recognition element such as an antibody is brought in close contact with the target analyte and this interaction is then converted to a measurable colorimetric output (Campàs et al. 2009) using the catalytic activity of a natural enzyme (in most cases horseradish peroxidase enzyme) (Mulchandani 1998). A particular challenge in employing natural enzymes is that due to their organic nature, their activity is influenced by environmental conditions, i.e. temperature can lead to denaturing of the enzymes thereby losing its catalytic power or the catalytic activity is high enough for the assay only under specific conditions. In addition, the cost associated with the synthesis, purification and storage of natural enzymes further adds to the challenge (Nicell and Wright 1997; Valderrama et al. 2002). Considering these challenges, there has been a significant push to look at alternate materials that mimic the catalytic activity of natural enzymes. The discovery that certain nanoparticles can mimic the catalytic activity of natural enzymes has spurred significant interest in their exploration as ‘artificial enzymes’ (Wei and Wang 2013). Several nanomaterials have now been reported to mimic the catalytic activity of natural enzymes, commonly called nanozymes. These activities typically include the peroxidase, oxidase, catalase, and

148

S. Naveen Prasad et al.

superoxide dismutase activity of natural enzymes. More recently esterase, phosphatase, and protease-mimic activities have also been reported (Wu et al. 2019; Weerathunge et al. 2017, 2019b, c; Singh et al. 2017a; Karim et al. 2018a, b; Kumar Sharma et al. 2014; Walther et al. 2019). Given the high stability of inorganic nanoparticles and the ability of the nanoparticles to show catalytic activity across a broad range of reaction parameters, they have been widely used to develop nanozyme-based sensors where the transducer (detection) platform could be electrochemical, colorimetric, chemiluminescent, fluorescent or surface-enhanced Raman spectroscopy (Zhang et al. 2019). With this knowledge, the current chapter provides a comprehensive overview of the different classes of pesticide, their mode of action, toxicity, etc. This is followed by a description of the various nanozyme-based sensors that have been developed to detect the different classes of pesticides, including the underlying working principle of the sensor, the limit of detection, and the robustness of the sensor, when tested in real samples.

6.2

Chemical Classification of Pesticides

The chemical nature of the active ingredient not only gives information on the efficacy, physical and chemical properties of the pesticide but also provides insight into how best we can use the information to develop effective remediation/mitigation strategies. Broadly, pesticides can be classified into four groups – organochlorines, organophosphates, carbamates, and pyrethroids (Büchel 1983) with some pesticides not falling into any one of these categories.

6.2.1

Organochlorines

Organochlorine pesticides are chlorinated hydrocarbons with at least five chlorine atoms. They have low aqueous solubility and therefore tend to adsorb on to particles present in the soil. In humans, organochlorine pesticides tend to interact with lipids, making it difficult to be excreted, leading to them readily accumulating in the human body tissues. Due to their hydrophobic nature, they are also known to accumulate in aquatic sediments and biota. In fact, many of the organochlorine pesticides are persistent in the environment. The persistence of organochlorine pesticides can range from 2 months to 15 years due to their resistance to degradation (by abiotic or microbial means) or metabolism (by aquatic or terrestrial organisms) (Nowell 2019; Jayaraj et al. 2016). Given their long-term residual effect on the environment through accumulation in soil, sediment, and biota, their use is severely restricted. The most commonly used organochlorine-based agricultural pesticides – dichlorodiphenyltrichloroethane and endosulfan have been banned in many

6 Nanozyme-Based Sensors for Pesticide Detection

Fig. 6.1 Chemical structure of commonly used dichlorodiphenyltrichloroethane – DDT and (b) endosulfan

149

organochlorine

pesticides

(a)

countries but these are still used in several developing countries in agriculture or for disease control (malaria, typhus) (Yadav and Devi 2017; Nowell 2019; Subramaniam and Solomon 2006). Organochlorine compounds are generally used as insecticides as they disrupt the central nervous system of the target insect by acting as GABA (γ-aminobutyric acid) antagonist. Organochlorine pesticides target the GABA-gated calcium and chloride channels inhibiting ion influx and cause the release of neurotransmitters by inhibiting Ca- and Mg-ATPase (D Buckingham et al. 2017). In humans, organochlorine pesticides act as endocrine-disrupting chemicals by interfering with the molecular circuitry and the function of the endocrine system (Jayaraj et al. 2016). A measurable quantity of pesticides can be easily exposed to human either directly during application of organochlorine pesticides or indirectly when passing through an area where organochlorine pesticides were recently applied. Exposure to organochlorine pesticides can cause neuromuscular impairment, elevated serum cholesterol, hypertension, and stimulation of drug and steroid metabolism (Subramaniam and Solomon 2006). Many organochlorine molecules have been found to be neurotoxic and carcinogenic with an increased risk of hormone-related cancers (Jayaraj et al. 2016). Well known examples of organochlorine pesticides include dichlorodiphenyltrichloroethane, lindane, endosulfan, aldrin, dieldrin, chlordane, methoxychlor, toxaphene, mirex, kepone, benzene hexachloride (Fig. 6.1).

6.2.2

Organophosphates

Organophosphorus pesticides are a group of chemicals consisting of synthetic amides, esters and thiol derivatives of phosphonic, phosphonothioic, phosphoric or phosphorothioic acids that have high potency with low persistence (Eto 2018). They are used extensively in agriculture and household pest control as they

150

S. Naveen Prasad et al.

hydrolyze upon exposure to light and air without releasing any toxic products, thus minimizing the risk of bioaccumulation and biomagnification (Stoytcheva and Zlatev 2011). Given this nature of organophosphorus pesticides, it became a favorable choice over organochlorine pesticides. In saying this, however, one cannot be sure that organophosphorus pesticides degrade completely as residues have been detected in soil and water long after its application (Krieger 2001). Organophosphorus compounds inhibit acetylcholinesterase, an enzyme that is critical for normal functioning of the nervous system (Chambers and Levi 2013). The inhibition is by an irreversible transphosphorylation reaction of organophosphorus pesticides with acetylcholinesterase in the plasma, red blood cells and the synapses in the peripheral and central nervous system. Inhibition of acetylcholinesterase prevents the hydrolytic breakdown of acetyl choline, thereby overstimulating the nicotinic and muscarinic receptors (Adeyinka and Pierre 2019). The inhibition of acetylcholinesterase is an irreversible reaction where the organophosphate compound mimics acetyl choline such that the catalytic activity of the enzyme is lost (Chambers and Levi 2013). Given that organophosphorus compounds directly affect the central nervous system, they are considered to be acutely toxic that can cause long-term damage even at trace levels. In fact, a well-known chemical warfare agent that was used recently during the Syrian civil war used organophosphorus compounds as a base to create the nerve gas that targets the nervous system by inhibiting acetylcholinesterase. The clinical manifestation of organophosphorus pesticide poisoning in humans is on the central nervous system along with cardiovascular, respiratory and gastrointestinal systems. The central nervous system complications include psychosis, seizure, and hallucinations; on the other hand, cardiovascular complications include prolonged QTc (a condition related to heart rhythm), arrhythmia, bradycardia, hypo, and hypertension. Noncardiac pulmonary edema, severe bronchospasm, aspiration pneumonia, diaphragmatic muscle weakness is also caused by organophosphorus pesticides, all of which progresses to respiratory failure. Gastrointestinal metabolic system complications include hyperglycaemia, pancreatitis, electrolyte imbalance and acute kidney problems (Peter et al. 2014). The toxic nature of organophosphorus pesticides has prompted the International Agency for Research on Cancer to classify commonly used organophosphorus pesticides such as parathion, malathion, diazinon, and tetrachlorvinphos as carcinogens (Adeyinka and Pierre 2019). The United States Environmental Protection Agency has categorized organophosphorus pesticides as Class I – Highly toxic substances (Songa and Okonkwo 2016). The introduction of toxicologically safer synthetic pyrethroids significantly reduced the usage of organophosphorus pesticides, however, they are still the preferred choice of insecticides (Chambers and Levi 2013). Common examples of organophosphorus pesticides include parathion, methyl parathion, malathion, fenthion, fenitrothion, pirimiphos-methyl, azinphos-methyl, temephos, azamethiphos, tetrachlorvinphos, dichlorvos, chlorpyrifos, diazinon, ethoprophos, phosmet, dimethoate, omethoate, dipterex (active ingredient: trichlorfon), acephate, methylparaoxon, ethyl-paraoxon, glyphosate (Fig. 6.2).

6 Nanozyme-Based Sensors for Pesticide Detection

151

Fig. 6.2 General chemical structure of organophosphorus pesticides

Fig. 6.3 General chemical structure of carbamates

6.2.3

Carbamates

Carbamates are insecticidal pesticides that are N-methyl carbamates derived from carbamic acid. They are mechanistically similar to organophosphorus pesticides as they target the nervous system of the insect where a reversible carbamylation reaction of acetylcholinesterase occurs at the neuronal synapse level and neuromuscular junctions lasting for about 24 h. They degrade naturally in the environment within months thus minimizing environmental pollution (Yadav and Devi 2017). Carbamate poisoning can cause severe parasympathetic symptoms similar to organophosphate poisoning mixed with autonomic presentations. Humans exposed to carbamates exhibit difficulty breathing, excessive sweating, and pinpoint pupils. Considering that the underlying mechanism of action is reversible, i.e. lasting only for 24 h, these symptoms only last for a short time (Silberman and Taylor 2019). This can also be a significant issue as detecting carbamate poisoning needs to occur within the 24 h period, else the testing may lead to false positives or false negatives (Sulaiman et al. 2019; Silberman and Taylor 2019). Typical examples of carbamate are carbaryl, carbofuran, aldicarb, bendiocarb, fenobucarb, methiocarb, pirimicarb, trimethacarb, propoxur, oxamyl, and methomyl (Fig. 6.3).

6.2.4

Pyrethroids

Pyrethrins are naturally occurring organic compounds obtained from Chrysanthemum flowers (Chrysanthemum coccineum and C. cinerariaefolium) (Yadav and Devi 2017). Pyrethroid pesticides are synthetic organic compounds similar to natural pyrethrins and create their toxicity by preventing the closure of sodium channels in the axons of the nervous system. The pyrethrin pesticides keep the sodium channels in an open state resulting in the inability of the nerves to repolarize thereby

152

S. Naveen Prasad et al.

Fig. 6.4 Chemical structure of commonly used pyrethroids including allethrin, permethrin and cypermethrin

paralyzing the organism (Jayaraj et al. 2016). These are typically fast-acting and are required in very low doses to show toxicity. Most pyrethrin pesticides have relatively low mammalian toxicity, are non-persistent and easily degradable upon light exposure. It has been suggested that these pesticides are relatively safe for application on food crops. However, exposure to very high levels can cause headache, nausea, vomiting, muscle twitching, and convulsions (Yadav and Devi 2017). Examples of

6 Nanozyme-Based Sensors for Pesticide Detection

153

pyrethroid pesticides include allethrin, cypermethrin, permethrin, deltamethrin, cyfluthrin, bifenthrin, and cyhalothrin (Fig. 6.4).

6.2.5

Others

6.2.5.1

Acetamiprid

Acetamiprid is a neonicotinoid used for the control of sucking-type insects (Fig. 6.5). It is a neurotoxin that causes agonistic effects on the nicotinic acetylcholine receptors of the postsynaptic membrane of nerve cells. Although the relative acute and chronic mammalian toxicity is low, concerns of the potential health risk due to frequent exposure and extensive usage still exist.

6.2.5.2

Atrazine

Atrazine (2-chloro-4-ethylamino-6-isopropyl amino-s-triazine) is a widely used herbicide of the triazine class. It is used for the control of broadleaf and grass weeds (Fig. 6.6). It acts by binding to plastoquinone-binding protein in the photosystem II and inhibits photosynthesis (Shimabukuro and Swanson 1969). Short term exposure was found to cause lung, heart and kidney congestion, damage to adrenal glands, muscle spasms, low blood pressure, and weight loss, while long term exposure caused cardiovascular damage, muscle and retinal damage and cancer (Graziano et al. 2006; Solomon et al. 1996). Therefore, United States Environmental Protection Agency has placed restrictions on the usage of atrazine to limit surface water and groundwater contamination. Fig. 6.5 The chemical structure of acetamiprid pesticide

Fig. 6.6 The chemical structure of atrazine

154

6.3

S. Naveen Prasad et al.

Nanozyme Based Sensors

6.3.1

Organophosphorus Pesticide Sensors

6.3.1.1

Acetylcholinesterase-Based Sensor with Oxidase-Mimic Nanozyme

Organophosphorus pesticide are compounds known to inhibit the activity of the enzyme acetylcholinesterase. This property of organophosphorus pesticides has been used to develop colorimetric nanozyme sensors. These sensors either uses the product of the enzyme acetylcholinesterase to degrade the nanozyme thereby decreasing the activity or use the acetylcholinesterase enzyme catalysed product to enhance the color generation by the nanozyme. For instance, acetylthiocholine, the substrate for the enzyme acetylcholinesterase, is hydrolyzed to form an inactive metabolite thiocholine. Although thiocholine may seem like an inactive metabolite, interestingly, the molecule triggers the decomposition of nanoparticles. This strategy was used to create an organophosphorus pesticide sensor (Yan et al. 2018). The sensor used oxidase-mimicking γ-MnOOH nanowires as a nanozyme that disintegrates into Mn2+ ions by selective reaction with thiocholine. This causes a notable loss in the catalytic activity of the MnOOH nanozyme resulting in a lower intensity of color generated due to the oxidation of the chromogenic oxidase substrate 3,30 ,5,50 -Tetramethylbenzidine. The lower intensity of color is directly proportional to the catalytic activity of the acetylcholinesterase enzyme with a limit of detection of 0.007 mU mL1 acetylcholinesterase in solution. The sensing capability was further enhanced by creating a portable assembly on paper that showed a detection limit of 0.1 mU mL1 for acetylcholinesterase (Huang et al. 2019). In addition to acetylcholinesterase, the sensor also showed the capability to detect omethoate and dichlorvos. However, the sensor showed cross-reactivity to oxamyl (a carbamyl pesticide). A similar concept was used where oxidasemimicking MnO2 nanosheets were used for the detection of paraoxon with a detection limit of 1 ng/mL (Yan et al. 2017). In another strategy, polyacrylic acidcoated cerium oxide nanoparticles (PAA-CeO2) were used as oxidase-mimic while organophosphorus pesticides was used as an inhibitor to suppress the activity of acetylcholinesterase. In contrast to the earlier cases where the catalytic metabolite resulted in the decomposition of the nanozyme, here the metabolite resulted in a reduced degree of the nanozyme-mediated oxidation of the chromogenic substrate. It was suggested that the thiol-containing thiocholine with an ability to act as a reducing agent may play an important role in the reduced oxidation of the substrate. The presence of organophosphorus pesticides results in reduced catalytic activity of acetylcholinesterase thereby producing less thiocholine, which allowed the nanozyme to convert more of the chromogenic substrate to a colored product (Zhang et al. 2016b). This sensor showed a detection limit of 8.62 ppb and 26.73 ppb for dichlorvos and methyl paraoxon, respectively. Although both strategies using oxidase-mimic nanozyme have merits, the role of thiocholine is unclear, i.

6 Nanozyme-Based Sensors for Pesticide Detection

155

e. does it result in the disintegration of the nanozyme or if the reducing ability of thiocholine results in less chromogenic substrate to be oxidized.

6.3.1.2

Acetylcholinesterase Based Sensor with Peroxidase-Mimic Nanozyme

Peroxidase-mimic nanozymes need H2O2 as a substrate in addition to the chromogenic substrate for the generation of a colorimetric response. The underlying principle of the peroxidase-mimic acetylcholinesterase sensors is to in situ generate H2O2 which is then used as a substrate by the nanozyme. In such sensors, the first step of the catalytic activity of the enzyme acetylcholinesterase to produce choline (Eq. 6.1) is the same as seen in the case of oxidase-mimic nanozyme organophosphorus pesticide sensors. The choline then reacts with dissolved oxygen in the presence of the natural choline oxidase enzyme to produce H2O2 (Eq. 6.2). Given that organophosphorus pesticides inhibit the catalytic activity of acetylcholinesterase, the amount of H2O2 produced would decrease in the presence of pesticide, leading to decrease in nanozyme activity (Eq. 6.3). This is observed by using a nanozyme that can convert a colorless substrate to a colored product. Commonly, chromogenic substrates are used for testing the nanozyme activity including 3,30 ,5,50 -Tetramethylbenzidine (TMB), 2,20 -azino-bis(3-ethylbenzothiazoline-6sulphonic acid (ABTS) and o-Phenylenediamine dihydrochloride (OPD). Acetylcholine þ H2 O Choline þ O2

Acetylcholinesterase

!

Choline oxidase

!

Choline

H2 O2

ð6:1Þ ð6:2Þ

H2 O2 þ substrate ðe:g:TMB, OPD, ABTSÞ Peroxidasemimic nanozyme

!

oxidized substrate ðe:g:TMBox , OPDox , ABTSox Þ þ H2 O

ð6:3Þ

This strategy was first established using magnetic Fe3O4 nanoparticles as the color generating nanozyme (Liang et al. 2013) where detection limits of 10 nM and 5 μM for methyl-paraoxon and acephate, respectively, were obtained. Given that the sensitivity of colorimetric sensors is limited by the extinction coefficient of the chromogenic substrate, a chemiluminescent assay was developed using gold nanoparticles anchored to iron-based metal-organic gels (AuNPs/MOGs-Fe) where enhanced peroxidase-mimicking catalytic activity was observed due to the generation of multiple reactive oxygen species radicals (OH, O2, and 1O2) and enhanced electron transfer (He et al. 2018). This enhanced activity was attributed to the modification of the MOGs-Fe with AuNPs, which synergistically accelerated the chemiluminescent reaction of luminol, a chemiluminescent peroxidase substrate. The sensor could detect the ethoprophos pesticide and operated within a linear dynamic range of 5–800 nM with a detection limit of 1 nM. The potential feasibility

156

S. Naveen Prasad et al.

of using the sensor in complex environments was also validated by detecting organophosphorus pesticide ethoprophos in water samples. The use of metal-organic framework was further extended to using ZIF-8 framework encapsulating Fe3O4 nanoparticles as a peroxidase-mimic nanozyme (Bagheri et al. 2019) that could oxidize either colorimetric or fluorometric substrate. The ZIF-8 encapsulating Fe3O4 nanozyme was used for the rapid detection of diazinon as a model organophosphorus pesticide. Using a fluorometric substrate, the sensor detected diazinon in the concentration range of 0.5–500 nM with a detection limit of 0.2 nM. The robustness of the sensor was established by detecting diazinon in water and fruit juices. In addition to the use of plate-based colorimetric assays, a paper-based portable mini-diagnostic platform using the peroxidase-mimicking catalytic activity of cobalt oxyhydroxide nanoflakes has also been recently developed for the detection of acetylcholinesterase (Jin et al. 2019). The assay was first developed in a platebased model and the learning was then applied for developing a paper-based assay. To develop the paper-based platform, an adsorbent paper was first imprinted with cobalt oxyhydroxide nanoflake nanozyme using an immersion method. An ink containing a mixture of 3,30 ,5,50 -Tetramethylbenzidine and H2O2 was used to handwrite the words ‘JLU’ on the nanozyme imprinted paper. The paper showed the ability to quantitatively detect acetylcholinesterase in the range of 0.1–5 mU mL1 by performing color analysis (ImageJ) on the images acquired using a smartphone.

6.3.1.3

Colorimetric or Fluorometric Inhibition in the Absence of Another Natural Enzyme

In addition to the aforementioned sensor platforms, a simple colorimetric sensor was developed using peroxidase-mimic gold nanorods where organophosphorus pesticide malathion was shown to inhibit the catalytic activity of the nanozyme (Biswas et al. 2016). A comparison of the catalytic activity of positively charged gold nanorods, positively charged quasi-spherical gold nanoparticles, negative charged quasi-spherical gold nanoparticles, as well as horseradish peroxidase, suggested that the gold nanorods with an aspect ratio of 2.8 demonstrated 2.5 times higher peroxidase activity than natural horseradish peroxidase enzyme and positively charged spherical gold nanoparticles. The superior activity was attributed to the positively charged surface of the gold nanorods that results in the formation of peroxide radicals, their stabilization and partial electron transfer process. The sensor system showed an inverse relationship between the catalytic activity of the gold nanorods and malathion concentration with a sensitivity of 1.78 μg/mL and the ability to detect malathion in water samples. The authors further improved the sensitivity of the sensor system by creating bimetallic nanomaterials (Singh et al. 2017b; Anderson et al. 2016, 2019). The bimetallic palladium-gold nanorods sensor system used in this case showed an improvement in sensitivity that was two orders of magnitude higher than the monometallic system (1.78 μg/mL with the Au nanorods

6 Nanozyme-Based Sensors for Pesticide Detection

157

to 60 ng/mL in the bimetallic Pd-Au nanorods). The selective quenching of enzymelike catalytic activity was attributed to the sulfanyl group (R-S-R’) of malathion that was suggested to interact with the nanorods resulting in a change of the surface charge. The inhibition-based concept was further reported where the peroxidasemimicking catalytic activity of CuO/multiwall carbon nanotubes was shown to be inhibited in the presence of glyphosate pesticide (Chang et al. 2016). However, instead of a chromogenic substrate as employed in the case of the gold nanorod system, a fluorogenic substrate was used. The change in the substrate resulted in a highly sensitive sensor system with the ability to detect glyphosate as low as 0.67 ppb while the operational linear range was 0.002–0.01 ppm. The high sensitivity and robustness to detect the pesticide in water samples suggested the importance of this sensor system to detect the pesticide at a concentration lower than the United States Environmental Protection Agency regulation of 0.7 ppm. Although both the chromogenic and fluorogenic sensor systems have significant merit, their cross-reactivity with other organophosphorus pesticides and other contaminants typically present in the sample matrix is yet to be seen.

6.3.1.4

Chemiluminescent Sensor Array for Multiple Pesticide Detection

In contrast to fluorogenic or colorimetric substrates where the catalytic activity of the nanozyme results in the oxidation of these substrates to form a fluorogenic or colorimetric product, chemiluminescent sensors result in the production of light from a chemical reaction (Wang et al. 2013). It has been suggested that chemiluminescence assays have advantages such as a low detection limit, wide linearity range, and simple operation. In contrast to detecting a single pesticide using conventional “lockkey” sensing mode where a receptor binds to a single pesticide, array-based sensing methods employ the differential interactions of analytes to generate distinct responses for each analyte without the need for specific receptors. Such systems generate rich multidimensional data that can then be used for classification and identification through the use of statistical tools (He et al. 2014). Combining the strengths of chemiluminescence and array-based sensors, a simple, and highly sensitive sensor array using silver nanoparticles was developed to discriminate five pesticides including three organophosphorus pesticides – dimethoate, dipterex, chlorpyrifos and two carbamates – carbaryl and carbofuran (He et al. 2015). The underlying principle of the assay was that luminol, a chemiluminescent substrate, reduces silver nitrate to form luminol-functionalized silver nanoparticles. These nanoparticles react with H2O2 producing a chemiluminescence emission. It was suggested that the reaction between H2O2 and nanoparticles can be dynamically tuned depending on the reaction condition. This allowed the sensor system to generate triple-channel information containing the chemiluminescence intensity, time of appearance of chemiluminescence emissions and the time taken by the chemiluminescence emission to reach peak value. It was further suggested that pesticides also had the capability to influence the chemiluminescence depending

158

S. Naveen Prasad et al.

on the affinity of the pesticide to the nanoparticle (Zhang et al. 2005; Xie et al. 2011). This meant that each pesticide leads to distinct chemiluminescence responses. The difference in the affinity was attributed to the presence of different functional groups. Exposing the sensor to five independent pesticides created a ‘fingerprint’ chemiluminescence profile for each pesticide which were further subjected to tools such as principal component analysis to convert the patterns to canonical scores that allowed easy identification of the pesticide. Based on the results, it was suggested that the sensor could identify pesticides as low as 24 μg/mL in concentration.

6.3.1.5

Chemiluminescence Switching Assay

In another strategy, the ability of sub-10 nm Fe3O4 nanoparticles to enhance the chemiluminescence emission was exploited to develop a sensor (Guan et al. 2012) for the detection of a range of pesticides including ethoprophos, parathion-methyl, nicosulfuron, and endosulfan. The principle of the sensor system involved exploiting the peroxidase-like catalytic activity of Fe3O4 nanoparticles through the generation of superoxide anions as a result of the decomposition of dissolved oxygen (Fig. 6.7). The high surface-to-volume ratio of the nanoparticles allowed efficient adsorption of these superoxide anions to the nanoparticle surface. Ethanol was then used as a radical scavenger (Rose and Waite 2001), which did not allow the Fe3O4 nanoparticles to produce light through the conversion of luminol. In the case where a pesticide such as ethoprophos was added before the addition of ethanol,

Fig. 6.7 Mechanism of chemiluminescence-based sensing platform using Fe3O4 nanoparticles. In the absence of the pesticide: (1) Fe3O4 nanoparticles catalyze the decomposition of dissolved oxygen to superoxide anions which adsorb on the nanoparticle surface, (2) ethanol scavenges the produced superoxide anions, (3) as there is no ROS, addition of luminol does not lead to light production. However, in the presence of the pesticide ethoprophos (EP): (1) Fe3O4 nanoparticles catalyze the decomposition of dissolved oxygen to superoxide anions which adsorb on the nanoparticle surface, (4) the introduction of pesticide EP results in binding of the EP molecules to the nanoparticle surface, (5) ethanol addition cannot scavenge superoxide anions due to the surfacebound EP, (6) the addition of luminol produces strong chemiluminescence emission. (7) The alternate paths are combined to form a chemiluminescence “switching on” chemosensor. (Reprinted from Guan et al. (2012) with permission from ACS Publications)

6 Nanozyme-Based Sensors for Pesticide Detection

159

the pesticide could bind strongly to the surface of the nanoparticles through coordinative reaction with surface Fe2+ ions. The pesticide on the surface could then protect the superoxide anions from ethanol scavenging. This allowed the pesticide bound nanoparticle to produce light emission in the presence of luminol creating a chemiluminescence “switching-on” chemosensor. An observation in the work was that the light emission was dependent on the strength of interaction between the pesticide and nanoparticle. Using this, a range of pesticides could be detected. An additional capability of this sensor system was that superparamagnetic nature of sub-10 nm Fe3O4 nanoparticles allowed a simple magnetic separation approach to attain interference-free measurement for detection of the pesticide in green tea. This presents a unique opportunity to perform sensing measurements without matrix interference which otherwise remains a major problem in the field of sensors (Liu et al. 2011).

6.3.1.6

Nanozyme-Based Immunoassays

In all the aforementioned examples, the nanoparticle itself played the role of recognition. Although these approaches have significant merit, it is important to consider that without a specific recognition moiety, the sensor may have non-specific interaction with interfering molecules present in the sample matrix. This may lead to either false positives or negatives. Therefore, it was unsurprising to see the incorporation of different recognition moieties to detect organophosphorus pesticides. The most common and widely used sensor incorporating recognition moieties is Enzyme-linked immunosorbent assay (ELISA). In an ELISA, the target is immobilized in a well of a microplate and then complexed with an antibody that is linked to a reporter enzyme which converts the substrate to produce a measurable product (Engvall and Perlmann 1971). This version of ELISA is called the direct assay. There have been several variants of ELISA including indirect assay and capture sandwich assay (Lequin 2005). Another variant is the development of the bio-barcode assay where short oligonucleotides of DNA are used as target identification strands (Nam et al. 2003). Several such immunoassays coupled with nanozymes have been employed for the detection of organophosphorus pesticides. Bio-barcode Immunoassay A competitive bio-barcode immunoassay for the trace detection of parathion in a range of sample matrices including water, pear, cabbage, and rice was recently shown (Chen et al. 2019). In contrast to the other strategies that have been described, this approach used multiple nanoparticles as shown in (Fig. 6.8). These included (i) gold nanoparticles (AuNPs) labelled with thiolated ssDNA and monoclonal antibodies against parathion; (ii) magnetic nanoparticles (MNPs) functionalized with ovalbumin attached with parathion hapten and; (iii) platinum nanoparticles (PtNP) labelled with complementary thiolated ssDNA that acted as the nanozyme. The mechanism of detection involved a multi-step process where the first step saw the mixing of the functionalized AuNPs and PtNPs. Due to complementary base pairing of the thiolated DNA, the reaction yielded an

160

S. Naveen Prasad et al.

Fig. 6.8 The operating process of the colorimetric bio-barcode immunoassay for parathion detection is shown. (a) mechanism using nanozyme as the color generating catalyst and (b) mechanism using natural horseradish peroxidase enzyme to generate a colorimetric response. (Reprinted from Chen et al. (2020) with permission from ACS Publications)

AuNP-PtNP probe. The MNPs along with the sample containing the pesticide of interest – parathion was then introduced. A competitive reaction occurred between the parathion and the hapten on the surface of the MNPs to bind to the monoclonal antibodies present on the surface of the AuNPs. This led to the formation of two complexes viz. an AuNP-PtNP-Parathion complex and AuNP-PtNP-MNP complex. The AuNP-PtNP-MNP complex was magnetically separated, and the PtNP nanozyme was separated from the complex through the addition of dithiothreitol (DTT) that resulted in the dehybridization of the DNA. The free PtNPs could then catalyze the oxidation of the chromogenic substrate 3,30 ,5,50 -Tetramethylbenzidine to form a blue-colored product. Although the process of sensing was elaborate and complex, the strength of this sensor system resulted in a highly sensitive and low detection limit of 2 ng/L. This was a significant improvement over a bio-barcode ELISA (without nanozyme) employed for the detection of triazophos by the same authors (Du et al. 2016). The improvement in the assay was attributed to the high catalytic activity of the PtNP nanozyme. The assay was also developed by replacing the PtNP nanozyme with gold-platinum (Au@Pt) bimetallic nanozyme (Chen et al. 2020) that resulted in a detection limit of 2.13 ng/kg (Fig. 6.8a). Simultaneously, the stability and sensitivity of the sensor in comparison to natural enzyme horseradish peroxidase was assessed (Fig. 6.8b). The reason for the replacement of the monometallic nanozyme with a bimetallic nanozyme was attributed to the susceptibility of PtNPs to aggregation which was one of the reasons which lead to the sensing performance to be compromised in the former case. The capability of the

6 Nanozyme-Based Sensors for Pesticide Detection

161

Fig. 6.9 The underlying principle of the sandwich immunochromatographic assay – (a) schematic showing the different areas of the sensing device. (b) simultaneous immunodetection of butyrylcholinesterase activity and total amount of butyrylcholinesterase. (c) Smartphone-based ambient light sensor. (Reprinted from Zhao et al. (2018) with permission from ACS Publications)

bio-barcode assay to accurately detect pesticides not only in buffer conditions but also in a wide range of sample matrices outlines the robustness of this system. Sandwich Immunochromatic Test Strips Having realised the strength of immunoassays in terms of specificity and selectivity as well as its potential to overcome limitations of conventional analytical methods, further improvements were made to overcome an important challenge associated with immunoassays – the need to use multiple antibodies, specifically in sandwich-type assays. A simple immunochromatographic test (lateral-flow device) was developed that could expand the capabilities of sensing from laboratory-based methods to point-ofcare testing (Zhao et al. 2018). This sensing system combined the strength of immunochromatographic test strips and ambient light sensors instead of directly using smartphone camera due to several drawbacks – the major being image resolution (Feng et al. 2014). Ambient light sensors are superior in terms of providing higher sensitivity and precision than mobile cameras as the optical signal is the primary source of data. A new sensor system was developed to detect both the activity and total amount of butyrylcholinesterase (Fig. 6.9). This enzyme is produced as a result of exposure to organophosphorus pesticide ethyl paraoxon. As shown in Fig. 6.9a, the immunochromatographic test strip to test the total butyrylcholinesterase consisted of a sample pad – for sample introduction, a conjugate pad – functionalized with nanozyme-butyrylcholinesterase monoclonal antibodies conjugate, a test line – butyrylcholinesterase monoclonal

162

S. Naveen Prasad et al.

antibodies functionalized on nitrocellulose membrane, and an absorbent pad – required to measure the activity. The immunochromatographic test strip to test the activity of butyrylcholinesterase consisted of the same elements as mentioned previously with a modification only in the conjugate pad where there was no functionalization. When a sample containing butyrylcholinesterase and ethyl paraoxon-butyrylcholinesterase migrates from sample pad to test line, it carries the nanozyme-butyrylcholinesterase monoclonal antibodies to the test line where butyrylcholinesterase monoclonal antibodies has been pre-immobilized. In this case, the monoclonal antibodies was used as a capturing and labelling antibody as butyrylcholinesterase has four identical antigenic determinants and can bind to four monoclonal antibodies simultaneously. This meant that both the butyrylcholinesterase and ethyl paraoxon-butyrylcholinesterase were captured by the monoclonal antibodies creating a sandwich structure at the test line. The chromogenic substrate was then added which resulted in the formation of the colored product due to the catalytic activity of the nanozyme. The total amount of butyrylcholinesterase was determined by measuring the light intensity using an ambient light sensor (Fig. 6.9b, c). It is important to note that both the butyrylcholinesterase and ethyl paraoxon-butyrylcholinesterase result in the generation of color giving the user information on the total amount of butyrylcholinesterase in the sample. To further detect the activity of the butyrylcholinesterase, the sample was first drop casted on another test strip which did not have the nanozyme-monoclonal antibodies in the conjugation pad. Similar to the previous case, the monoclonal antibodies in the test line once again captured both the butyrylcholinesterase and ethyl paraoxonbutyrylcholinesterase. While the conjugation of ethyl paraxone to butyrylcholinesterase inhibited the catalytic activity of the butyrylcholinesterase enzyme, only the free/active butyrylcholinesterase could convert its substrate to the product which could then be detected using the ambient light sensor (Fig. 6.9b, c). The smartphone-based sensing system could detect a range of 0.05–6.4 nM of total butyrylcholinesterase while 0.1–6.4 nM of the active butyrylcholinesterase. The working of this system was also validated using human plasma samples with a rationale that this sensor system could be suitable to understand the exposure of humans to organophosphorus pesticides. Biomimetic Immunosorbent Assay Another strategy is to modify two steps in ELISA viz. (i) replace natural enzyme with a nanozyme as an alternative for immunoassay label (Farka et al. 2018; He et al. 2011) and (ii) replace conventional antibodies with molecularly imprinted polymers (MIP) or “plastic antibodies” as recognition moieties (Chianella et al. 2013; Piletsky et al. 2000). Given that this new assay uses the underlying working principle of ELISA with modifications, this assay was renamed as biomimetic nanozyme-linked immunosorbent assay (Yan et al. 2019). The colorimetric assay thus developed was used for the detection of triazophos with a detection limit of 1 ng/mL. The portability potential for biomimetic nanozyme-linked immunosorbent assay was also shown through the use of surface-enhanced Raman scattering for detection instead of a colorimetric response.

6 Nanozyme-Based Sensors for Pesticide Detection

6.3.1.7

163

Nanozyme Aptasensors

In addition to the use of monoclonal antibodies, the past decade has seen a rise in the development and use of aptamers as recognition elements in sensor development (Hermann and Patel 2000; Dhiman et al. 2017). Aptamers are single-stranded DNA or RNA sequences generated from an in-vitro selection technique known as the systemic evolution of ligands by exponential enrichment (SELEX) (Dhiman et al. 2017). They are called ‘artificial antibodies’ as they have a high binding affinity, selectivity, and specificity to their target (Hayat and Marty 2014). The use of aptamers to detect organophosphorus pesticides was demonstrated recently by combining the strength of peroxidase-mimicking catalytic activity of silver nanoparticles and chlorpyrifos specific aptamers (Weerathunge et al. 2019a). The sensor platform exploited the dynamic nature of the non-covalent interactions of the aptamer to the nanozyme vs the target (Fig. 6.10). A non-catalytic nanozyme (nanozyme surface covered with pesticide-specific aptamer with blocked nanozyme activity) was used as a sensor probe. In the presence of chlorpyriphos, the aptamer molecules left the nanozyme surface to bind to the pesticide, which rejuvenated the nanozyme activity. By controlling the association and dissociation kinetics of the aptamer to the nanozyme, the sensor generated a colorimetric response specifically in the presence of the target pesticide chlorpyrifos with a detection limit of ~11 ppm.

6.3.1.8

Phosphatase-Mimic Nanozymes – A Dual Role

Phosphotriesterases are enzymes produced by certain bacterial species that have the capability to degrade organophosphorus esters. This important enzyme is considered as a supporting factor to enable bacteria to survive in soil under environmentally toxic conditions (Singh 2009). Recent reports have suggested that ceria (CeO2) nanoparticles containing cerium ions in dual oxidation states (Ce3+ and Ce4+) can effectively catalyze the hydrolysis of organophosphorus esters (Vernekar et al. 2016). For instance, nanoceria catalyzes the conversion of paraoxon (triester) to diethyl phosphate (diesters). Other reports have further emerged where Nanozymes have been shown to catalyze the hydrolysis of phosphotriester compounds such as methyl paraoxon, methyl parathion and methyl chlorpyrifos to produce its diester and monoester forms (Khulbe et al. 2018; Janoš et al. 2019). The phosphodiesterase mimic activity of ceria was exploited to develop a dual-mode sensor for the detection of methyl-paraoxon (Wei et al. 2019a). The enzyme-mimic catalytic activity of the nanozyme resulted in the hydrolysis of the methyl-paraoxon to para-nitrophenol. The hydrolyzed product was monitored spectroscopically as the product generated a bright yellow color. The color could also be analyzed using a smartphone-based color detection method which may be suitable for on-site analysis of pesticides. The proposed method showed a detection limit of 0.42 μM. The authors further improved the sensor performance achieving a detection limit of 0.375 μM by coupling the phosphatase-mimic nanoceria with the inner filter effect on the fluorescence of the carbon dots (Wei et al. 2019b). Inner filter effect is an approach for target recognition

164

S. Naveen Prasad et al.

Fig. 6.10 Working principle of the colorimetric aptasensor platform for chlorpyrifos sensing. The intrinsic peroxidase-mimic nanozyme activity of the tyrosine-capped AgNPs shows its ability to convert colorless substrate to a colored product (Nanozyme ON). The introduction of Chl aptamers leads to non-covalent interaction of the aptamer with the nanozyme surface resulting in loss of nanozyme activity (Nanozyme OFF). This non-catalytic aptamer-nanozyme conjugate serves as the sensor probe. Exposing the probe to non-specific pesticides does not allow the aptamers to dissociate from the surface and the nanozyme activity remains ‘OFF’. Exposure to chlorpyrifos pesticide results in the dissociation of the aptamer from the surface of the nanozyme. This exposes the surface atoms of the nanozyme to the analyte, leading to the recovery of catalytic activity as ‘Nanozyme ON’. (Reprinted with permission from Weerathunge et al. (2019a) with permission from Elsevier)

based on fluorescence quenching effect. The overlapping of the fluorophore excitation spectra (carbon dots) with the absorption spectra of the absorber (para-nitrophenol) resulted in a reduced intensity of the fluorescence emission due to the competition between the fluorophore and the absorber for incident radiation.

6 Nanozyme-Based Sensors for Pesticide Detection

6.3.1.9

165

Electrochemical Sensors

Nanozyme technology has also been incorporated into electrochemical sensors where the catalytic ability of nickel oxide (NiO) nanoplatelets to reduce the nitro group of parathion to hydroxylamine group via the transfer of four electrons and four protons was exploited to detect 0.024 μM parathion (Khairy et al. 2018). Another sensor took advantage of the high affinity of para-sulfonated calix[n]arene ( pSCn) to bind to methyl parathion by first binding pSCn to the nanozyme, which could then reduce the nitro group of the pesticide that could be electrochemically detected (Bian et al. 2010). The use of a recognition moiety in the sensor, in fact, showed high specificity and sensitivity with a detection limit of 4 nM. However, it is worth mentioning that this sensing platform was not discussed in the context of nanozyme sensors. More recently, the ability of amino acids to catalyze the hydrolysis of organophosphorus pesticides was also used to develop organophosphorus pesticide sensors (Qiu et al. 2019). TiO2 nanoparticles served as carriers for serine (S), histidine (H) and glutamic acid (E) that behaved like biomimetic enzymes with hydrolysis activity converting organophosphorus pesticides (methyl paraoxon, methyl parathion and ethyl paraoxon) to redox active p-nitrophenol. The generation of this redox-active species was detected electrochemically where a detection limit of 0.2 μM was observed. It is also noted that this concept was first developed by the same authors using carbon nanotubes conjugated with a catalytic triad (S, H, E) peptide (Zhang et al. 2016a). It was suggested that the proximity of the three key amino acids could promote the hydrolysis reaction.

6.3.2

Acetamiprid Sensors

As outlined in the Sect. 6.3.1.7, combining the strength of nanozymes with the outstanding target recognition ability of aptamers was first shown by Weerathunge et al. for the detection of acetamiprid (Weerathunge et al. 2014) before the concept was further refined for the detection of chlorpyrifos (Weerathunge et al. 2019a). The use of an acetamiprid specific S-18 aptamer allowed the sensor to generate a colorimetric response due to the catalytic activity of gold nanoparticle nanozyme specifically in the presence of acetamiprid (Fig. 6.11). This highly specific sensor showed a detection limit of 1.8 ppm which was within the limit specified by the Environmental Protection Agency (Wijaya et al. 2014). An aggregation based sensor platform was also developed for acetamiprid sensing using peroxidase-mimic hemin-functionalized reduced graphene oxide (heminrGO) composite and an acetamiprid aptamer (Yang et al. 2015). The underlying concept of the sensor was that the hemin-rGO possessed sites for binding of aptamers as well as peroxidase-mimic activity. The presence of aptamers on the surface prevented salt-induced aggregation of the nanozyme. When acetamiprid was introduced, the aptamer molecules detached from the surface of the composite to

166

S. Naveen Prasad et al.

Fig. 6.11 The reversible inhibition of the nanozyme activity of gold nanoparticles (GNP) using acetamiprid specific aptamer. (a) Bare GNP shows intrinsic peroxidase-mimic catalytic activity, (b) this catalytic activity is inhibited by the binding of S-18 aptamer resulting in loss of catalytic activity, (c) in the presence of acetamiprid, the aptamer undergoes target-responsive structural changes and binds to the target molecule, while the exposed surface of the GNP resumes its peroxidase-like activity. (Reprinted from Weerathunge et al. (2014) with permission from ACS Publications)

bind to acetamiprid, which resulted in aggregation of the composite resulting in a reduction of the composite content after centrifugation. By measuring the oxidized colorimetric product, the concentration of acetamiprid in the sample could be realised.

6.3.3

Atrazine Sensors

The use of Fe3O4-TiO2/rGO nanocomposite for the detection of atrazine was shown recently (Boruah and Das 2020). The detection mechanism involves the inhibition of the oxidation of peroxidase substrate (3,30 ,5,50 -Tetramethylbenzidine) which is attributed to the hydrogen bond forming between atrazine and 3,30 ,5,50 -Tetramethylbenzidine. The nanocomposite could also be used to photocatalytically degrade atrazine under sunlight irradiation where light absorption led to the production of electrons and holes resulting in the formation of reactive oxygen species. The reactive oxygen species such as hydroxyl radical (OH•) and superoxide radical (O•2) were responsible for the degradation of atrazine.

6.4

Conclusion

This chapter provides a comprehensive overview of the different nanozyme-based approaches employed so far for the detection of pesticides (summary provided in Table 6.1). As illustrated from the examples, several sensing platforms show outstanding ability to detect pesticides not only in standard buffers but also to detect them in food and environmental samples. However, an important point for consideration is that in the absence of a target recognition moiety, the specificity and sensitivity of the sensor system may be compromised. While earlier reports focused

6 Nanozyme-Based Sensors for Pesticide Detection

167

Table 6.1 Summary of the nanozyme sensors for the detection of pesticides Pesticide Omethoate

Paraoxon

Limit of detection 0.35 ng/mL (aq.) 10 ng/mL (paper) 0.14 ng/mL (aq.) 3 ng/mL (paper) 1.0 ng/mL

Dichlorvos Methyl-paraoxon Acephate Methyl-paraoxon Ethoprophos

8.62 ppb 26.73 ppb 5 μM 10 nM 1 nM

–

Diazinon

0.2 nM

Water and fruit juice

Methyl parathion

10 ng/mL

–

Malathion

1.78 μg/mL

Tap water

Malathion

60 ng/mL

Tap water

Glyphosate

0.67 ppb

Tap and lake water

Dimethoate, dipterex, carbaryl, chlorpyrifos, carbofuran Ethoprophos

24 μg/ml

–

0.1 nM

Green tea

Parathion

2.0 ng/L

Parathion

2.13 ng/kg

Ethyl paraoxon

Triazophos

0.025 nM (total butyrylcholinesterase) 0.028 nM (active butyrylcholinesterase) 1 ng/mL

Water, pear, cabbage, and rice Pear, rice, apple, and cabbage Human plasma

Chlorpyrifos

11.3 ppm

River water

Paraoxon

–

–

Parathion, methyl paraoxon

–

–

Dichlorvos

Sample type Rat serum, Chinese cabbage

Nanozyme γ-MnOOH nanowires (Huang et al. 2019)

River and tap water

MnO2 nanosheets (Yan et al. 2017) PAA-CeO2 NPs (Zhang et al. 2016b)

–

Fe3O4 nanoparticles (Liang et al. 2013)

River and tap water

AuNPs/MOGs-Fe NPs (He et al. 2018) Fe3O4 NPs@ZIF-8(Bagheri et al. 2019) CoOOH nanoflakes (Jin et al. 2019) Gold nanorods (Biswas et al. 2016) Pd-Au nanorods (Singh et al. 2017b) CuO/Carbon nanotubes (Chang et al. 2016) Silver NPs (He et al. 2015)

Water and pear

Fe3O4 NPs (Guan et al. 2012) AuNP/PtNP (Chen et al. 2019) AuNP/Au@PtNP (Chen et al. 2020) PtPd NPs (Zhao et al. 2018)

Platinum NPs (Yan et al. 2019) Silver NPs (Weerathunge et al. 2019a) CeO2 NPs (Vernekar et al. 2016) Nanoceria (Janoš et al. 2019) (continued)

168

S. Naveen Prasad et al.

Table 6.1 (continued) Pesticide Methyl paraoxon

Limit of detection –

Sample type –

Methyl paraoxon

0.42 μM

Methyl paraoxon

0.375 μM

Parathion

0.024 μM

Methyl parathion

4.0 nM

Chinese yam, lotus seed, and bitter apricot seed American ginseng and tap water Tap water, human urine, and tomato juice Pear

Methyl paraoxon, methyl parathion, ethyl paraoxon Acetamiprid

0.2 μM

Lettuce

1.8 ppm

–

Acetamiprid

40 nM

Waste water

Atrazine

2.98 μg/L

River, pond and well water

Nanozyme Zr-CeO2 (Khulbe et al. 2018) Nanoceria (Wei et al. 2019a) Nanoceria (Wei et al. 2019b) NiO nanoplatelets (Khairy et al. 2018) Silver NPs (Bian et al. 2010) TiO2 NPs (Qiu et al. 2019) Gold NPs (Weerathunge et al. 2014) Hemin-rGO (Yang et al. 2015) Fe3O4-TiO2 nanocomposite (Boruah and Das 2020)

on developing pesticide sensors without recognition moieties, more recent papers have incorporated recognition moieties such as antibodies, molecularly imprinted polymers and aptamers to bring in the element of specificity to the sensor. This incorporation of highly specific recognition elements has resulted in more specific sensors for the detection of targeted organophosphorus pesticides, acetamiprid and atrazine. The next phase of research would need to focus on translational capabilities of nanozyme-based sensors. Such efforts will bring nanozyme-based sensor technologies closer to other high-end analytical techniques for reliable on-site detection of pesticides. Acknowledgements Authors acknowledge the support of Ian Potter Foundation in establishing Sir Ian Potter NanoBioSensing Facility at RMIT University, Australia that has enabled some of the work captured in this book chapter. V. Bansal and R. Ramanathan acknowledge the Australian Research Council (ARC) for funding support through ARC Discovery grant scheme (DP170103477). V. Bansal acknowledges the ARC for a Future Fellowship (FT140101285).

6 Nanozyme-Based Sensors for Pesticide Detection

169

References Adeyinka A, Pierre L (2019) Organophosphates. In: StatPearls. StatPearls Publishing, Treasure Island Agostini M, Bianchin A (2003) Acute renal failure from organophospate poisoning: a case of success with haemofiltration. Hum Exp Toxicol 22(3):165–167. https://doi.org/10.1191/ 0960327103ht343cr Anderson SR, Mohammadtaheri M, Kumar D, O’Mullane AP, Field MR, Ramanathan R, Bansal V (2016) Robust nanostructured silver and copper fabrics with localized surface plasmon resonance property for effective visible light induced reductive catalysis. Adv Mater Interfaces 3 (6):1500632. https://doi.org/10.1002/admi.201500632 Anderson SR, O’Mullane AP, Della Gaspera E, Ramanathan R, Bansal V (2019) LSPR-induced catalytic enhancement using bimetallic copper fabrics prepared by galvanic replacement reactions. Adv Mater Interfaces 6(16):1900516. https://doi.org/10.1002/admi.201900516 Arash A, Ahmed T, Govind Rajan A, Walia S, Rahman F, Mazumder A, Ramanathan R, Sriram S, Bhaskaran M, Mayes E, Strano MS, Balendhran S (2019) Large-area synthesis of 2D MoO 3 x for enhanced optoelectronic applications. 2D Mater 6(3):035031. https://doi.org/10.1088/20531583/ab1114 Bagheri N, Khataee A, Hassanzadeh J, Habibi B (2019) Sensitive biosensing of organophosphate pesticides using enzyme mimics of magnetic ZIF-8. Spectrochim Acta A 209:118–125. https:// doi.org/10.1016/j.saa.2018.10.039 Behera BK, Das A, Sarkar DJ, Weerathunge P, Parida PK, Das BK, Thavamani P, Ramanathan R, Bansal V (2018) Polycyclic Aromatic Hydrocarbons (PAHs) in inland aquatic ecosystems: perils and remedies through biosensors and bioremediation. Environ Pollut 241:212–233. https://doi.org/10.1016/j.envpol.2018.05.016 Bian Y, Li C, Li H (2010) Para-Sulfonatocalix [6] arene-modified silver nanoparticles electrodeposited on glassy carbon electrode: preparation and electrochemical sensing of methyl parathion. Talanta 81(3):1028–1033. https://doi.org/10.1016/j.talanta.2010.01.054 Biswas S, Tripathi P, Kumar N, Nara S (2016) Gold nanorods as peroxidase mimetics and its application for colorimetric biosensing of malathion. Sensors Actuators B Chem 231:584–592. https://doi.org/10.1016/j.snb.2016.03.066 Boruah PK, Das MR (2020) Dual responsive magnetic Fe3O4-TiO2/graphene nanocomposite as an artificial nanozyme for the colorimetric detection and photodegradation of pesticide in an aqueous medium. J Hazard Mater 385:121516. https://doi.org/10.1016/j.jhazmat.2019.121516 Büchel KH (1983) Chemistry of pesticides. Wiley, New York Buckingham SD, Ihara M, B Sattelle D, Matsuda K (2017) Mechanisms of action, resistance and toxicity of insecticides targeting GABA receptors. Curr Med Chem 24(27):2935–2945. https:// doi.org/10.2174/0929867324666170613075736 Campàs M, Prieto-Simón B, Marty J-L (2009) A review of the use of genetically engineered enzymes in electrochemical biosensors. In: Seminars in cell & developmental biology, vol 1. Elsevier, New York, pp 3–9 CDPR (2013) Community guide to recognizing and reporting pesticide problems. https://www. cdpr.ca.gov/docs/dept/comguide/ Chambers JE, Levi PE (2013) Organophosphates chemistry, fate, and effects: chemistry, fate, and effects. Elsevier, Saint Louis Chang Y-C, Lin Y-S, Xiao G-T, Chiu T-C, Hu C-C (2016) A highly selective and sensitive nanosensor for the detection of glyphosate. Talanta 161:94–98. https://doi.org/10.1016/j. talanta.2016.08.029 Chen F, Tang F, Yang C-T, Zhao X, Wang J, Thierry B, Bansal V, Dai J, Zhou X (2018) Fast and highly sensitive detection of pathogens wreathed with magnetic nanoparticles using dark-field microscopy. ACS Sens 3(10):2175–2181. https://doi.org/10.1021/acssensors.8b00785

170

S. Naveen Prasad et al.

Chen G, Jin M, Yan M, Cui X, Wang Y, Zheng W, Qin G, Zhang Y, Li M, Liao Y (2019) Colorimetric bio-barcode immunoassay for parathion based on amplification by using platinum nanoparticles acting as a nanozyme. Microchim Acta 186(6):339. https://doi.org/10.1007/ s00604-019-3433-6 Chen G, Jin M, Ma J, Yan M, Cui X, Wang Y, Zhang X, Li H, Zheng W, Zhang Y, Abd El-Aty AM, Hacımüftüoğlu A, Wang J (2020) Competitive bio-barcode immunoassay for highly sensitive detection of parathion based on bimetallic nanozyme catalysis. J Agric Food Chem 68 (2):660–668. https://doi.org/10.1021/acs.jafc.9b06125 Chianella I, Guerreiro A, Moczko E, Caygill JS, Piletska EV, De Vargas Sansalvador IMP, Whitcombe MJ, Piletsky SA (2013) Direct replacement of antibodies with molecularly imprinted polymer nanoparticles in ELISA – development of a novel assay for vancomycin. Anal Chem 85(17):8462–8468. https://doi.org/10.1021/ac402102j DeLorenzo ME, Scott GI, Ross PE (2001) Toxicity of pesticides to aquatic microorganisms: a review. Environ Toxicol Chem 20(1):84–98. https://doi.org/10.1002/etc.5620200108 Dhiman A, Kalra P, Bansal V, Bruno JG, Sharma TK (2017) Aptamer-based point-of-care diagnostic platforms. Sensors Actuators B Chem 246:535–553. https://doi.org/10.1016/j.snb. 2017.02.060 Du P, Jin M, Chen G, Zhang C, Jiang Z, Zhang Y, Zou P, She Y, Jin F, Shao H, Wang S, Zheng L, Wang J (2016) A competitive bio-barcode amplification immunoassay for small molecules based on nanoparticles. Sci Rep 6(1):38114. https://doi.org/10.1038/srep38114 Engvall E, Perlmann P (1971) Enzyme-linked immunosorbent assay (ELISA) quantitative assay of immunoglobulin G. Immunochemistry 8(9):871–874. https://doi.org/10.1016/0019-2791(71) 90454-X Eto M (2018) Organophosphorus pesticides. CRC Press, Cleveland Farka Z, Čunderlová V, Horáčková V, Pastucha M, Mikušová Z, Hlaváček A, Skládal P (2018) Prussian blue nanoparticles as a catalytic label in a sandwich nanozyme-linked immunosorbent assay. Anal Chem 90(3):2348–2354. https://doi.org/10.1021/acs.analchem.7b04883 Feng S, Caire R, Cortazar B, Turan M, Wong A, Ozcan A (2014) Immunochromatographic diagnostic test analysis using Google Glass. ACS Nano 8(3):3069–3079. https://doi.org/10. 1021/nn500614k Graziano N, McGuire MJ, Roberson A, Adams C, Jiang H, Blute N (2006) 2004 national atrazine occurrence monitoring program using the abraxis ELISA method. Environ Sci Technol 40 (4):1163–1171. https://doi.org/10.1021/es051586y Guan G, Yang L, Mei Q, Zhang K, Zhang Z, Han M-Y (2012) Chemiluminescence switching on peroxidase-like Fe3O4 nanoparticles for selective detection and simultaneous determination of various pesticides. Anal Chem 84(21):9492–9497. https://doi.org/10.1021/ac302341b Hayat A, Marty JL (2014) Aptamer based electrochemical sensors for emerging environmental pollutants. Front Chem 2:41. https://doi.org/10.3389/fchem.2014.00041 He W, Liu Y, Yuan J, Yin J-J, Wu X, Hu X, Zhang K, Liu J, Chen C, Ji Y, Guo Y (2011) Au@Pt nanostructures as oxidase and peroxidase mimetics for use in immunoassays. Biomaterials 32 (4):1139–1147. https://doi.org/10.1016/j.biomaterials.2010.09.040 He Y, He X, Liu X, Gao L, Cui H (2014) Dynamically tunable chemiluminescence of luminolfunctionalized silver nanoparticles and its application to protein sensing arrays. Anal Chem 86 (24):12166–12171. https://doi.org/10.1021/ac503123q He Y, Xu B, Li W, Yu H (2015) Silver nanoparticle-based chemiluminescent sensor array for pesticide discrimination. J Agric Food Chem 63(11):2930–2934. https://doi.org/10.1021/acs. jafc.5b00671 He L, Jiang ZW, Li W, Li CM, Huang CZ, Li YF (2018) In situ synthesis of gold nanoparticles/ metal–organic gels hybrids with excellent peroxidase-like activity for sensitive chemiluminescence detection of organophosphorus pesticides. ACS Appl Mater Interfaces 10 (34):28868–28876. https://doi.org/10.1021/acsami.8b08768 Hermann T, Patel DJ (2000) Adaptive recognition by nucleic acid aptamers. Science 287 (5454):820–825

6 Nanozyme-Based Sensors for Pesticide Detection

171

Huang L, Sun D-W, Pu H, Wei Q, Luo L, Wang J (2019) A colorimetric paper sensor based on the domino reaction of acetylcholinesterase and degradable γ-MnOOH nanozyme for sensitive detection of organophosphorus pesticides. Sensors Actuators B Chem 290:573–580. https:// doi.org/10.1016/j.snb.2019.04.020 Janoš P, Ederer J, Došek M, Štojdl J, Henych J, Tolasz J, Kormunda M, Mazanec K (2019) Can cerium oxide serve as a phosphodiesterase-mimetic nanozyme? Environ Sci Nano 6 (12):3684–3698. https://doi.org/10.1039/C9EN00815B Jayaraj R, Megha P, Sreedev P (2016) Organochlorine pesticides, their toxic effects on living organisms and their fate in the environment. Interdiscip Toxicol 9(3–4):90–100. https://doi.org/ 10.1515/intox-2016-0012 Jin R, Xing Z, Kong D, Yan X, Liu F, Gao Y, Sun P, Liang X, Lu G (2019) Sensitive colorimetric sensor for point-of-care detection of acetylcholinesterase using cobalt oxyhydroxide nanoflakes. J Mater Chem B 7(8):1230–1237. https://doi.org/10.1039/C8TB02987C Kandjani AE, Mohammadtaheri M, Thakkar A, Bhargava SK, Bansal V (2014) Zinc oxide/silver nanoarrays as reusable SERS substrates with controllable ‘hot-spots’ for highly reproducible molecular sensing. J Colloid Interface Sci 436:251–257. https://doi.org/10.1016/j.jcis.2014.09. 017 Kandjani AE, Sabri YM, Mohammad-Taheri M, Bansal V, Bhargava SK (2015) Detect, remove and reuse: a new paradigm in sensing and removal of Hg (II) from wastewater via SERS-active ZnO/Ag nanoarrays. Environ Sci Technol 49(3):1578–1584. https://doi.org/10.1021/es503527e Karim MN, Anderson SR, Singh S, Ramanathan R, Bansal V (2018a) Nanostructured silver fabric as a free-standing NanoZyme for colorimetric detection of glucose in urine. Biosens Bioelectron 110:8–15. https://doi.org/10.1016/j.bios.2018.03.025 Karim MN, Singh M, Weerathunge P, Bian P, Zheng R, Dekiwadia C, Ahmed T, Walia S, Della Gaspera E, Singh S, Ramanathan R, Bansal V (2018b) Visible-light-triggered reactive-oxygenspecies-mediated antibacterial activity of peroxidase-mimic CuO nanorods. ACS Appl Nano Mat 1(4):1694–1704. https://doi.org/10.1021/acsanm.8b00153 Khairy M, Ayoub HA, Banks CE (2018) Non-enzymatic electrochemical platform for parathion pesticide sensing based on nanometer-sized nickel oxide modified screen-printed electrodes. Food Chem 255:104–111. https://doi.org/10.1016/j.foodchem.2018.02.004 Khulbe K, Roy P, Radhakrishnan A, Mugesh G (2018) An unusual two-step hydrolysis of nerve agents by a nanozyme. ChemCatChem 10(21):4826–4831. https://doi.org/10.1002/cctc. 201801220 Krieger R (2001) Handbook of pesticide toxicology: principles and agents, vol 1. Academic, San Diego Kumar Sharma T, Ramanathan R, Weerathunge P, Mohammadtaheri M, Kumar Daima H, Shukla R, Bansal V (2014) Aptamer-mediated “turn-off/turn-on” nanozyme activity of gold nanoparticles for kanamycin detection. Chem Commun 50(100):15856–15859. https://doi.org/ 10.1039/c4cc07275h Le NDB, Yesilbag Tonga G, Mout R, Kim S-T, Wille ME, Rana S, Dunphy KA, Jerry DJ, Yazdani M, Ramanathan R, Rotello CM, Rotello VM (2017) Cancer cell discrimination using host–guest “doubled” arrays. J Am Chem Soc 139(23):8008–8012. https://doi.org/10.1021/jacs. 7b03657 Lequin RM (2005) Enzyme immunoassay (EIA)/enzyme-linked immunosorbent assay (ELISA). Clin Chem 51(12):2415–2418. https://doi.org/10.1373/clinchem.2005.051532 Liang M, Fan K, Pan Y, Jiang H, Wang F, Yang D, Lu D, Feng J, Zhao J, Yang L (2013) Fe3O4 magnetic nanoparticle peroxidase mimetic-based colorimetric assay for the rapid detection of organophosphorus pesticide and nerve agent. Anal Chem 85(1):308–312. https://doi.org/10. 1021/ac302781r Liu B, Han M, Guan G, Wang S, Liu R, Zhang Z (2011) Highly-controllable molecular imprinting at superparamagnetic iron oxide nanoparticles for ultrafast enrichment and separation. J Phys Chem C 115(35):17320–17327. https://doi.org/10.1021/jp205327q

172

S. Naveen Prasad et al.

Mac Loughlin TM, Peluso ML, Etchegoyen MA, Alonso LL, de Castro MC, Percudani MC, Marino DJ (2018) Pesticide residues in fruits and vegetables of the argentine domestic market: occurrence and quality. Food Control 93:129–138. https://doi.org/10.1016/j.foodcont.2018.05. 041 Muhamadali H, Subaihi A, Mohammadtaheri M, Xu Y, Ellis DI, Ramanathan R, Bansal V, Goodacre R (2016) Rapid, accurate, and comparative differentiation of clinically and industrially relevant microorganisms via multiple vibrational spectroscopic fingerprinting. Analyst 141 (17):5127–5136. https://doi.org/10.1039/C6AN00883F Mulchandani A (1998) Principles of enzyme biosensors. In: Enzyme and microbial biosensors. Springer, Totowa, pp 3–14 Nam J-M, Thaxton CS, Mirkin CA (2003) Nanoparticle-based bio-bar codes for the ultrasensitive detection of proteins. Science 301(5641):1884–1886 Nicell JA, Wright H (1997) A model of peroxidase activity with inhibition by hydrogen peroxide. Enzym Microb Technol 21(4):302–310. https://doi.org/10.1016/S0141-0229(97)00001-X Nowell LH (2019) Pesticides in stream sediment and aquatic biota: distribution, trends, and governing factors. CRC Press, Boca Raton Peter JV, Sudarsan TI, Moran JL (2014) Clinical features of organophosphate poisoning: a review of different classification systems and approaches. Indian J Crit Care Med 18(11):735. https:// doi.org/10.4103/0972-5229.144017 Piletsky SA, Piletska EV, Chen B, Karim K, Weston D, Barrett G, Lowe P, Turner AP (2000) Chemical grafting of molecularly imprinted homopolymers to the surface of microplates. Application of artificial adrenergic receptor in enzyme-linked assay for β-agonists determination. Anal Chem 72(18):4381–4385. https://doi.org/10.1021/ac0002184 Plowman B, Ippolito SJ, Bansal V, Sabri YM, O’Mullane AP, Bhargava SK (2009) Gold nanospikes formed through a simple electrochemical route with high electrocatalytic and surface enhanced Raman scattering activity. Chem Commun 33:5039–5041. https://doi.org/10.1039/ b910830k Qiu L, Lv P, Zhao C, Feng X, Fang G, Liu J, Wang S (2019) Electrochemical detection of organophosphorus pesticides based on amino acids conjugated nanoenzyme modified electrodes. Sensors Actuators B Chem 286:386–393. https://doi.org/10.1016/j.snb.2019.02.007 Ramanathan R, Kandjani AE, Walia S, Balendhran S, Bhargava SK, Kalantar-zadeh K, Bansal V (2013) 3-D nanorod arrays of metal–organic KTCNQ semiconductor on textiles for flexible organic electronics. RSC Adv 3(39):17654–17658. https://doi.org/10.1039/C3RA43291B Ramanathan R, Walia S, Kandjani AE, Balendran S, Mohammadtaheri M, Bhargava SK, KalantarZadeh K, Bansal V (2015) Low-temperature fabrication of alkali metal-organic charge transfer complexes on cotton textile for optoelectronics and gas sensing. Langmuir 31(4):1581–1587. https://doi.org/10.1021/la501446b Rose AL, Waite TD (2001) Chemiluminescence of luminol in the presence of iron (II) and oxygen: oxidation mechanism and implications for its analytical use. Anal Chem 73(24):5909–5920. https://doi.org/10.1021/ac015547q Sharma TK, Ramanathan R, Rakwal R, Agrawal GK, Bansal V (2015) Moving forward in plant food safety and security through NanoBioSensors: adopt or adapt biomedical technologies? Proteomics 15(10):1680–1692. https://doi.org/10.1002/pmic.201400503 Shimabukuro RH, Swanson HR (1969) Atrazine metabolism, selectivity, and mode of action. J Agric Food Chem 17(2):199–205. https://doi.org/10.1021/jf60162a044 Silberman J, Taylor A (2019) Carbamate toxicity. In: StatPearls. StatPearls Publishing, Treasure Island Singh BK (2009) Organophosphorus-degrading bacteria: ecology and industrial applications. Nat Rev Microbiol 7(2):156–164. https://doi.org/10.1038/nrmicro2050 Singh M, Weerathunge P, Liyanage PD, Mayes E, Ramanathan R, Bansal V (2017a) Competitive inhibition of the enzyme-mimic activity of Gd-based nanorods toward highly specific colorimetric sensing of l-cysteine. Langmuir 33(38):10006–10015. https://doi.org/10.1021/acs. langmuir.7b01926

6 Nanozyme-Based Sensors for Pesticide Detection

173

Singh S, Tripathi P, Kumar N, Nara S (2017b) Colorimetric sensing of malathion using palladiumgold bimetallic nanozyme. Biosens Bioelectron 92:280–286. https://doi.org/10.1016/j.bios. 2016.11.011 Solomon KR, Baker DB, Richards RP, Dixon KR, Klaine SJ, La Point TW, Kendall RJ, Weisskopf CP, Giddings JM, Giesy JP (1996) Ecological risk assessment of atrazine in North American surface waters. Environ Toxicol Chem 15(1):31–76. https://doi.org/10.1002/etc.5620150105 Songa EA, Okonkwo JO (2016) Recent approaches to improving selectivity and sensitivity of enzyme-based biosensors for organophosphorus pesticides: a review. Talanta 155:289–304. https://doi.org/10.1016/j.talanta.2016.04.046 Stoytcheva M, Zlatev R (2011) Organophosphorus pesticides analysis. In: Pesticides in the modern world-trends in pesticides analysis. Intech, Rijeka/Croatia, pp 143–164 Subramaniam K, Solomon J (2006) Organochlorine pesticides BHC and DDE in human blood in and around Madurai, India. Indian J Clin Biochem 21(2):169. https://doi.org/10.1007/ bf02912936 Sulaiman NS, Rovina K, Joseph VM (2019) Classification, extraction and current analytical approaches for detection of pesticides in various food products. J Consum Prot Food Saf:1–13. https://doi.org/10.1007/s00003-019-01242-4 Valderrama B, Ayala M, Vazquez-Duhalt R (2002) Suicide inactivation of peroxidases and the challenge of engineering more robust enzymes. Chem Biol 9(5):555–565. https://doi.org/10. 1016/S1074-5521(02)00149-7 Vernekar AA, Das T, Mugesh G (2016) Vacancy-engineered nanoceria: enzyme mimetic hotspots for the degradation of nerve agents. Angew Chem Int Ed 55(4):1412–1416. https://doi.org/10. 1002/anie.201510355 Walther R, Winther AK, Fruergaard AS, van den Akker W, Sørensen L, Nielsen SM, Jarlstad Olesen MT, Dai Y, Jeppesen HS, Lamagni P, Savateev A, Pedersen SL, Frich CK, VigierCarrière C, Lock N, Singh M, Bansal V, Meyer RL, Zelikin AN (2019) Identification and directed development of non-organic catalysts with apparent pan-enzymatic mimicry into nanozymes for efficient prodrug conversion. Angew Chem Int Ed 58(1):278–282. https://doi. org/10.1002/anie.201812668 Wang S, Ge L, Li L, Yan M, Ge S, Yu J (2013) Molecularly imprinted polymer grafted paper-based multi-disk micro-disk plate for chemiluminescence detection of pesticide. Biosens Bioelectron 50:262–268. https://doi.org/10.1016/j.bios.2013.07.003 Weerathunge P, Ramanathan R, Shukla R, Sharma TK, Bansal V (2014) Aptamer-controlled reversible inhibition of gold nanozyme activity for pesticide sensing. Anal Chem 86 (24):11937–11941. https://doi.org/10.1021/ac5028726 Weerathunge P, Sharma TK, Ramanathan R, Bansal V (2017) Chapter 23: nanozyme-based environmental monitoring. In: Advanced environmental analysis: applications of nanomaterials, volume 2, vol 2. The Royal Society of Chemistry, Cambridge, pp 108–132. https://doi.org/10. 1039/9781782629139-00108 Weerathunge P, Behera BK, Zihara S, Singh M, Prasad SN, Hashmi S, Mariathomas PRD, Bansal V, Ramanathan R (2019a) Dynamic interactions between peroxidase-mimic silver NanoZymes and chlorpyrifos-specific aptamers enable highly-specific pesticide sensing in river water. Anal Chim Acta 1083:157–165. https://doi.org/10.1016/j.aca.2019.07.066 Weerathunge P, Pooja D, Singh M, Kulhari H, Mayes EL, Bansal V, Ramanathan R (2019b) Transferrin-conjugated quasi-cubic SPIONs for cellular receptor profiling and detection of brain cancer. Sensors Actuators B Chem:126737. https://doi.org/10.1016/j.snb.2019.126737 Weerathunge P, Ramanathan R, Torok VA, Hodgson K, Xu Y, Goodacre R, Behera BK, Bansal V (2019c) Ultrasensitive colorimetric detection of murine norovirus using NanoZyme aptasensor. Anal Chem 91(5):3270–3276. https://doi.org/10.1021/acs.analchem.8b03300 Wei H, Wang E (2013) Nanomaterials with enzyme-like characteristics (nanozymes): nextgeneration artificial enzymes. Chem Soc Rev 42(14):6060–6093. https://doi.org/10.1039/ C3CS35486E

174

S. Naveen Prasad et al.

Wei J, Yang L, Luo M, Wang Y, Li P (2019a) Nanozyme-assisted technique for dual mode detection of organophosphorus pesticide. Ecotoxicol Environ Saf 179:17–23. https://doi.org/ 10.1016/j.ecoenv.2019.04.041 Wei J, Yang Y, Dong J, Wang S, Li P (2019b) Fluorometric determination of pesticides and organophosphates using nanoceria as a phosphatase mimic and an inner filter effect on carbon nanodots. Microchim Acta 186(2):66. https://doi.org/10.1007/s00604-018-3175-x WHO (2018) Pesticides. https://www.who.int/topics/pesticides/en/ Wijaya W, Pang S, Labuza TP, He L (2014) Rapid detection of acetamiprid in foods using SurfaceEnhanced Raman Spectroscopy (SERS). J Food Sci 79(4):T743–T747. https://doi.org/10.1111/ 1750-3841.12391 Wu J, Wang X, Wang Q, Lou Z, Li S, Zhu Y, Qin L, Wei H (2019) Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes (II). Chem Soc Rev 48 (4):1004–1076. https://doi.org/10.1039/C8CS00457A Xie C, Li H, Li S, Gao S (2011) Surface molecular imprinting for chemiluminescence detection of the organophosphate pesticide chlorpyrifos. Microchim Acta 174(3–4):311. https://doi.org/10. 1007/s00604-011-0626-z Yadav IC, Devi NL (2017) Pesticides classification and its impact on human and environment. In: Environmental science and engineering, vol 6. Springer, Berlin Yan X, Song Y, Wu X, Zhu C, Su X, Du D, Lin Y (2017) Oxidase-mimicking activity of ultrathin MnO 2 nanosheets in colorimetric assay of acetylcholinesterase activity. Nanoscale 9 (6):2317–2323. https://doi.org/10.1039/C6NR08473G Yan X, Song Y, Zhu C, Li H, Du D, Su X, Lin Y (2018) MnO2 nanosheet-carbon dots sensing platform for sensitive detection of organophosphorus pesticides. Anal Chem 90(4):2618–2624. https://doi.org/10.1021/acs.analchem.7b04193 Yan M, Chen G, She Y, Ma J, Hong S, Shao Y, Abd El-Aty A, Wang M, Wang S, Wang J (2019) Sensitive and simple competitive biomimetic nanozyme-linked immunosorbent assay for colorimetric and surface-enhanced Raman scattering sensing of triazophos. J Agric Food Chem 67 (34):9658–9666. https://doi.org/10.1021/acs.jafc.9b03401 Yang Z, Qian J, Yang X, Jiang D, Du X, Wang K, Mao H, Wang K (2015) A facile label-free colorimetric aptasensor for acetamiprid based on the peroxidase-like activity of heminfunctionalized reduced graphene oxide. Biosens Bioelectron 65:39–46. https://doi.org/10. 1016/j.bios.2014.10.004 Zhang Z-F, Cui H, Lai C-Z, Liu L-J (2005) Gold nanoparticle-catalyzed luminol chemiluminescence and its analytical applications. Anal Chem 77(10):3324–3329. https://doi.org/10.1021/ ac050036f Zhang Q, He X, Han A, Tu Q, Fang G, Liu J, Wang S, Li H (2016a) Artificial hydrolase based on carbon nanotubes conjugated with peptides. Nanoscale 8(38):16851–16856. https://doi.org/10. 1039/C6NR05015H Zhang S-X, Xue S-F, Deng J, Zhang M, Shi G, Zhou T (2016b) Polyacrylic acid-coated cerium oxide nanoparticles: an oxidase mimic applied for colorimetric assay to organophosphorus pesticides. Biosens Bioelectron 85:457–463. https://doi.org/10.1016/j.bios.2016.05.040 Zhang X, Wu D, Zhou X, Yu Y, Liu J, Hu N, Wang H, Li G, Wu Y (2019) Recent progress on the construction of nanozymes-based biosensors and their applications to food safety assay. Trends Anal Chem:115668. https://doi.org/10.1016/j.trac.2019.115668 Zhao Y, Yang M, Fu Q, Ouyang H, Wen W, Song Y, Zhu C, Lin Y, Du D (2018) A nanozyme-and ambient light-based smartphone platform for simultaneous detection of dual biomarkers from exposure to organophosphorus pesticides. Anal Chem 90(12):7391–7398. https://doi.org/10. 1021/acs.analchem.8b00837 Zohora N, Kumar D, Yazdani M, Rotello VM, Ramanathan R, Bansal V (2017) Rapid colorimetric detection of mercury using biosynthesized gold nanoparticles. Colloids Surf A Physicochem Eng Asp 532:451–457. https://doi.org/10.1016/j.colsurfa.2017.04.036

6 Nanozyme-Based Sensors for Pesticide Detection

175

Zou W, González A, Jampaiah D, Ramanathan R, Taha M, Walia S, Sriram S, Bhaskaran M, Dominguez-Vera JM, Bansal V (2018) Skin color-specific and spectrally-selective naked-eye dosimetry of UVA, B and C radiations. Nat Commun 9(1):3743. https://doi.org/10.1038/ s41467-018-06273-3 Zou W, Sastry M, Gooding JJ, Ramanathan R, Bansal V (2020) Recent advances and a roadmap to wearable UV sensor technologies. Adv Mater Technol 5(4):1901036. https://doi.org/10.1002/ admt.201901036

Chapter 7

Metal-Based Nanozyme: Strategies to Modulate the Catalytic Activity to Realize Environment Application Stuti Bhagat, Juhi Shah, and Sanjay Singh

Abstract Nanomaterials displaying catalytic properties of natural enzymes are regarded as “nanozymes”. Nanozymes offer contrasting advantages over conventional enzymes such as low cost production, high stability under stringent environment, controlled synthesis of shape, size, composition and surface functionalization. Last decade has witnessed a myriad of nanomaterials including metallic, metal oxides, and carbon-based nanoparticles with biological enzyme-like activities. These nanozymes predominantly resemble the activities of natural peroxidase, oxidase, superoxide dismutase, and catalase enzymes. Among various nanomaterials, metallic nanozymes such as gold, silver, platinum, palladium, and copper nanoparticles have gained tremendous attention. Nanozymatic activity along with other unique properties of optoelectronic and surface plasmon resonance makes them an ideal candidate for the material of multiple applications. Utilizing these properties, metallic nanozymes have been also used for disease diagnosis and biosensing of biomolecules. Although there are several advantages of using nanozymes, however, this unique class of artificial enzyme suffers from several limitations that need to be addressed. Low catalytic efficiency, less substrate selectivity, biocompatibility and lack of engineering of the active sites are some of the key concerns. In this chapter, we discussed different metal-based nanozymes and their related biological and environmental applications such as removal and detection of organic pollutants/dyes, and theranostics. A section is devoted to the various strategies used for improving the catalytic efficiency of metallic nanozymes. Application of nanozymes in the detection of environmental pollutant is also discussed. At the end, we also provided a comprehensive summary of the current developments and future prospects of this arena. Keywords Peroxidase activity · Catalytic nanoparticles · Enzyme mimetics · Oxidase activity · Artificial enzymes

S. Bhagat · J. Shah · S. Singh (*) Nanomaterials and Toxicology Laboratory, Division of Biological and Life Sciences, School of Arts and Sciences, Ahmedabad University, Ahmedabad, Gujarat, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 H. K. Daima et al. (eds.), Nanozymes for Environmental Engineering, Environmental Chemistry for a Sustainable World 63, https://doi.org/10.1007/978-3-030-68230-9_7

177

178

S. Bhagat et al.

Abbreviations ADP ATP AuNPs AuNRs BSA ELISA ESR H2O2 MB NCs NPs NRs
OH PdNPs PtNPs RNS ROS SOD TMB

7.1

Adenosine diphosphate Adenosine triphosphate Gold nanoparticles Gold nanorods Bovine serum albumin Enzyme-linked immunosorbent assay Electron spin resonance Hydrogen peroxide Methylene blue Nanoclusters Nanoparticles Nanorods Hydroxyl radicals Palladium nanoparticles Platinum nanoparticles Reactive nitrogen species Reactive oxygen species Superoxide dismutase 3,30 ,5,50 -Tetramethylbenzidine

Introduction

Catalytic nanoparticles (NPs) capable of performing the biochemical activities like a biological enzyme are regarded as nanozyme. Due to the inherent properties, nanomaterials display exceptional catalytic performance, which are often comparable to the natural enzymes. Compositionally, biological enzymes are globular proteins, therefore, their manufacturing requires high cost. Additionally, they demand strict storage conditions due to sensitivity, a slight change in the physico-chemical conditions leads to inactivation or denaturation of the enzyme. Conventional methods which include biological enzymes exposed to the conditions of pH and temperature beyond the recommended range, are prone to undergo an irreversible change in the structure required for catalytic function. Whereas, nanozymes effectively work as a surrogate of conventional enzymes for catalysis as they are much more cost effective, recyclable, stable at harsh environmental conditions, mass produced, easily tunable which offers their robust applications (Wu et al. 2019a). Furthermore, nanozymes can be remotely controlled through different stimuli such as light, heat, magnetic field and temperature which is reasonably impossible for conventional enzymes (Jiang et al. 2019). Natural enzymes are widely used in industrial and biomedical applications, however, due to the above-mentioned limitations, their full potential use has not been realized. Further, biological enzymes

7 Metal-Based Nanozyme: Strategies to Modulate the Catalytic Activity to. . .

179

also face limited applications in food processing, biosensing, environmental protection and pollutant detection, etc. Therefore, in the recent past, a lot of efforts have been devoted to developing artificial enzymes with comparable catalytic efficiency. Chemical molecule-based artificial enzymes were shown to have similar structure and catalytic property of the natural enzyme. These artificial enzymes included dendrimers, fullerenes, cyclodextrins, and porphyrins, etc (Wu et al. 2019a; Singh 2019). Although these chemical structures were able to perform catalytic reactions similar to biological enzymes, however, they were found to be extremely toxic to mammalian cells. In the further quest of artificial enzymes, iron oxide NPs (Fe3O4 NPs) were reported as peroxidase mimic by Gao et al. in 2007 (Gao et al. 2007). This study reported that Fe3O4 NPs-based nanozyme could successfully replace the natural horseradish peroxidase (HRP) enzyme from immunoassays. Subsequent to this report, numerous NPs are reported exhibiting different enzyme mimetic activity. For example, gold (Au), silver (Ag), cerium oxide (CeO2), carbon-based, platinum (Pt), palladium (Pd), Fe3O4, etc are some of the common enzyme mimetics. Broadly, these enzyme mimetic activities could be divided into four major types, peroxidase, catalase, phosphatase, superoxide dismutase (SOD), and oxidase enzyme activity. However, there are some gaps between natural enzymes and nanozymes where latter face several limitations including low activity, less turnover number and weak substrate specificity (Zhou et al. 2017). Therefore, in order to surpass the aforementioned limitations with nanozymes in future, several strategies have been implemented including incorporation of adenosine supplements (You et al. 2018), use of metal ions (Long et al. 2011), oligonucleotides (Hizir et al. 2016), chemical compounds (Singh et al. 2017), and bio-conjugation of nanozymes (Zhang et al. 2020). For an example, Vallabani et al. reported the peroxidase mimetic activity of citrate capped Fe3O4 NPs enhanced by incorporation of adenosine triphosphate (ATP) at neutral pH (Vallabani et al. 2017). The ATP helped in single electron transfer reaction in presence of Fe3O4 NPs and H2O2 which further generated
OH radicals. The Fe3O4 NPs retained their catalytic activity throughout a wide range of pH in presence of ATP. The synergistic combination of ATP and Fe3O4 NPs showed excellent antibacterial activity for gram positive (B. subtilis) and gram negative (E. coli) bacteria (Vallabani et al. 2020). Additionally, there are several reports on the NP shape, size, and composition controlled enzyme-like activities (Dong et al. 2018; Raza et al. 2016; Mistry et al. 2017; Fu et al. 2016a). Although various nanomaterials are reported to exhibit biological enzyme-like activities, this chapter is focused on the advances in the area of metal-based nanozymes. Among metallic NPs, Au, Ag, copper (Cu), Pt, and Pd, etc. are some of the common NP types reported to show biological enzyme-like activity. Metallic NPs are easy to synthesize as they require a minimum number of reagents, metal NPs shape and size can be easily controlled by slightly varying the reaction conditions such as pH, capping molecules and temperature. Metal NPs display unique characteristics such as colored suspension, large surface energies, high surface to volume ratio, and, plasmon resonance, which collectively makes them an attractive nanozyme. As an emerging application, researchers are using nanozymes for the detection of biological and environment samples. The peroxidase mimetic activity of NPs widely uses for the

180

S. Bhagat et al.

detection of the glucose, cholesterol, metal ions, pathogens and pollutants etc. For an instance, Yan et al. utilized peroxidase mimic Fe3O4 NPs for the detection of H2O2 in acid rain water (Zhuang et al. 2008). Fe3O4 NPs showed better affinity towards peroxidase substrate (TMB) compare to HRP. Nanozymes provide better catalytic affinity and analytic performance, holding great promise for the detection of environmental pollutants. The following section will comprise of the methods of controlling the enzymatic activities and environmental application of metal-based nanozymes.

7.2

Strategies to Modulate the Activities of Nanozymes

There have been several strategies to modulate the enzyme-like activities of nanozymes. The following section discusses about some of the important studies.

7.2.1

pH

AuNPs exhibits intrinsic peroxidase-like activity at acidic pH, whereas neutral pH facilitates SOD and catalase-like activity (He et al. 2013). Biological enzymes show maximum catalytic activity at optimum pH, for example peroxidase (pH – 4.0), catalase (pH – 7.0), SOD (pH – 7.0), and pepsin (pH – 1.5), etc. This limitation of natural enzyme restricts their broad-spectrum usage. Li et al. reported that nanocomposite of Au and melamine cyanurate exhibits high peroxidase-like activity at neutral pH which can be used for quantitative detection of blood glucose via one-pot colorimetric assay (Li et al. 2017). Such applications are not possible with biological peroxidase enzymes because they do not show the catalytic activity at neutral pH. However, nanozymes are shown to retain their catalytic activity even in alkaline conditions. In one of our recent studies, we have shown that Cu-Pt nanoalloy-based oxidase mimetic nanozyme could exhibit the catalytic activity in a broad range of pH (2–10) (Shah et al. 2019) which was further utilized for the identification of mammalian cells.

7.2.2

Temperature

Unlike natural enzymes, nanozymes retain their catalytic activity even beyond their optimum temperature. Generally, natural enzymes undergo irreversible aggregation and thus, lose catalytic activity, whereas nanozymes exhibit enzyme-like activity even at higher temperatures. For example, Cu-Pt and Fe-Pt nanoalloys (Shah et al. 2018, 2019), iridium nanocrystal (Feng et al. 2018), magnetic NPs, (Srinivasan et al. 2019) etc. The ideal storage temperature for natural enzymes is 20 or 80  C,

7 Metal-Based Nanozyme: Strategies to Modulate the Catalytic Activity to. . .

181

whereas when stored at higher temperatures undergo aggregation and lose catalytic activity. Several cycles of freezing and thawing also result in the loss of catalytic activity. In contrast to the natural enzyme, NPs are stable at room temperature. For example, biologically synthesized AgNPs remain spherical with narrow size (