Biological Oxidase Enzyme Mimetic Cu‐Pt Nanoalloys: A Multifunctional Nanozyme for Colorimetric Detection of Ascorbic Acid and Identification of Mammalian Cells

Nanozymes and their biomolecular conjugates as next-generation antibacterial agents: A comprehensive review

Antimicrobial resistance (AMR), the ability of bacterial species to develop resistance against exposed antibiotics, has gained immense global attention in the past few years. Bacterial infections are serious health concerns affecting millions of people annually worldwide. Therefore, developing novel antibacterial agents that are highly effective and avoid resistance development is imperative. Among various strategies, recent developments in nanozyme technology have shown promising results as antibacterials in several antibiotic-sensitive and resistant bacterial species. Nanozymes offer several advantages over corresponding natural enzymes, such as inexpensive, stable, multifunctional, tunable catalytic properties, etc. Although the use of nanozymes as antibacterial agents has provided promising results, the specific biomolecule-conjugated nanozymes have shown further improvement in catalytic performance and associated antibacterial efficacy. The exclusive design of functional nanozymes with theranostic potential is found to simultaneously inhibit the growth and image of AMR bacterial species. This review comprehensively summarizes the history of nanozymes, their classification, biomolecules conjugated nanozyme, and their mechanism of enzyme-mimetic activity and associated antibacterial activity in antibiotic-sensitive and resistant species. The futureneeds to effectively engineer the existing or new nanozymes to curb AMR have also been discussed.

Applications of Nanozymes in Chiral-Molecule Recognition through Electrochemical and Ultraviolet-Visible Analysis

Chiral molecules have similar physicochemical properties, which are different in terms of physiological activities and toxicities, rendering their differentiation and recognition highly significant. Nanozymes, which are nanomaterials with inherent enzyme-like activities, have garnered significant interest owing to their high cost-effectiveness, enhanced stability, and straightforward synthesis. However, constructing nanozymes with high activity and enantioselectivity remains a significant challenge. This review briefly introduces the synthesis methods of chiral nanozymes and systematically summarizes the latest research progress in enantioselective recognition of chiral molecules based on electrochemical methods and ultraviolet-visible absorption spectroscopy. Moreover, the challenges and development trends in developing enantioselective nanozymes are discussed. It is expected that this review will provide new ideas for the design of multifunctional chiral nanozymes and broaden the application field of nanozymes.

Ceria-Based Nanozymes in Point-of-Care Diagnosis: An Emerging Futuristic Approach for Biosensing

In recent years, there has been a notable increase in interest surrounding nanozymes due to their ability to imitate the functions and address the limitations of natural enzymes. The scientific community has been greatly intrigued by the study of nanoceria, primarily because of their distinctive physicochemical characteristics, which include a variety of enzyme-like activities, affordability, exceptional stability, and the ability to easily modify their surfaces. Consequently, nanoceria have found extensive use in various biosensing applications. However, the impact of its redox activity on the enzymatic catalytic mechanism remains a subject of debate, as conflicting findings in the literature have presented both pro-oxidant and antioxidant effects. Herein, we creatively propose a seesaw model to clarify the regulatory mechanism on redox balance and survey possible mechanisms of multienzyme mimetic properties of nanoceria. In addition, this review aims to showcase the latest advancements in this field by systematically discussing over 180 research articles elucidating the significance of ceria-based nanozymes in enhancing, downsizing, and enhancing the efficacy of point-of-care (POC) diagnostics. These advancements align with the ASSURED criteria established by the World Health Organization (WHO). Furthermore, this review also examines potential constraints in order to offer readers a concise overview of the emerging role of nanoceria in the advancement of POC diagnostic systems for future biosensing applications.

Recent advances in the colorimetric and fluorescence analysis of bioactive small-molecule compounds based on the enzyme-like activity of nanomaterials

Nanomaterials with enzyme-like activity have been widely used in the construction of colorimetric and fluorescence sensors due to their advantages of cost-effectiveness, high stability, good biocompatibility, and ease of modification. Furthermore, the colorimetric and fluorescence sensors, which are effective approaches for detecting bioactive small-molecule compounds, have been extensively explored due to their simple operation and high sensitivity. Recent significant researches have focused on designing various sensors based on nanozymes with peroxidase- and oxidase-like activity for the colorimetric and fluorescence analysis of different analytes. In this review, recent developments (from 2018 to present) in the colorimetric and fluorescent analysis of bioactive small-molecule compounds based on the enzyme-like activity of nanomaterials were summarized. In addition, the challenges and design strategies in developing colorimetric and fluorescent assays with high performance and specific sensing were discussed.

Lentinan stabilized bimetallic PdPt3 dendritic nanoparticles with enhanced oxidase-like property for L-cysteine detection

The development of nanozymes with enhanced catalytic activity has been drawing great interest. Lentinan with special structure may be used to prepare bimetallic nanomaterials to enhance their catalytic activity. Herein, lentinan stabilized PdPt₃ dendritic nanoparticles (PdPt₃-LNT NDs) were prepared through reduction of Na₂PdCl₄ and K₂PtCl₄ with a molar ratio of 1:3 using lentinan as a biological template. PdPt₃-LNT NDs had dendritic shape with size of 10.76 ± 1.82 nm. PdPt₃-LNT NDs had the hydrodynamic size about 25.7 nm and the zeta potential between -1.4 mV and - 4.9 mV at different pH. Furthermore, PdPt₃-LNT NDs catalyzed 3,3',5,5'-tetramethylbenzidine (TMB) to produce oxidized TMB, suggesting their oxidase-like property. The catalytic activity of PdPt₃-LNT NDs was the highest when pH was 4 and the temperature was 40 °C. The catalytic mechanism was the generation of ·O₂^- and ¹O₂ from O₂ catalyzed by PdPt₃-LNT NDs. More importantly, L-cysteine detection method was set up based on the oxidase-like property of PdPt₃-LNT NDs. This method had wide linear range for 0-200 μM and low detection limit for 3.099 μM. Taken together, PdPt₃-LNT NDs have good potential applications in bio-related detection in the future.

In situ generated Fe3C embedded Fe-N-doped carbon nanozymes with enhanced oxidase mimic activity for total antioxidant capacity assessment

In this work, we reported new Fe₃C embedded Fe-N-doped carbon nanomaterials (Fe₃C@Fe-N-CMs) generated in situ by the facile pyrolysis of Fe-Zn ZIF precursors. The resulting Fe₃C@Fe-N-CMs were equipped with several desirable nanozyme features, including multiple efficient intrinsic active sites (i.e. Fe-N_x, Fe₃C@C, and C-N moieties), large specific surface area and abundant mesoporous structures. As a result, these Fe₃C@Fe-N-CMs displayed exceptional ability to mimic three enzymes: peroxidase, catalase and oxidase, while the Fe₃C@Fe-N-CMs pyrolyzed at 800 °C, named CMs-800, showed the best enzyme-like properties. After systematically investigating the catalytic mechanism, we further explored the application of the oxidase-like properties of CMs-800 in the detection of the total antioxidant capacity (TAC) in beverages and tablets. This study not only provided a new approach to construct multifunctional carbon-based nanozymes, but also expanded the application of carbon nanozymes in the field of food quality and safety.

Selective Inhibition toward Dual Enzyme-like Activities of Iridium Nanozymes for a Specific Colorimetric Assay of Malathion without Enzymes

A colorimetric assay based on an enzyme-inhibition strategy is promising for the on-site detection of pesticide residues. Due to the high cost and low stability of enzymes, nanozymes (nanomaterials with enzyme-like activities) are widely developed as substitutes of enzymes. However, the inhibition of pesticides toward enzymes and nanozymes generally lacks selectivity. It is of great significance and challenge to design a specific pesticide assay based on an activity-inhibition strategy. Here, we discovered that iridium nanoparticles possess both peroxidase-like and oxidase-like activities under the same conditions, and their catalytic mechanisms are different. The synergistic effect of dual enzyme-like activities enhanced the colorimetric signal. Interestingly, the dual enzyme-mimicking activities could be simultaneously inhibited, and the inhibition effect exhibited high selectivity toward malathion. Considering the popularity and the hazards of malathion, a malathion assay method based on activity inhibition was established without enzymes and a redundant process. The synergistic effect of the selective inhibition of dual enzyme-like activities enhanced the selectivity and sensitivity. The proposed assay strategy opens up an avenue for specific assay of various pesticides.

Nitrogen, phosphorus co-doped hollow porous carbon microspheres as an oxidase-like electrochemical sensor for baicalin

The extraordinary properties and unique structure of porous carbon has rapidly turned into a new favorite in the development and application of high-performance electrocatalytic sensor. Nitrogen, phosphorus co-doped hollow porous...

A critical comparison of natural enzymes and nanozymes in biosensing and bioassays

Nanozymes (NZs) are nanomaterials that mimic enzyme-like catalytic activity. They have attracted substantial attention due to their inherent physicochemical properties for use as promising alternatives to natural enzymes (NEs) in a variety of research fields. Particularly, in biosensing and bioassays, NZs have opened a new horizon to eliminate the intrinsic limitations of NEs, including their denaturation at extreme pH values and temperatures, poor reusability and recyclability, and high production costs. Moreover, the catalytic activity of NZs can be modulated in the preparation step by following an appropriate synthesis strategy. This review aims to gain insight into the potential substitution of NEs by NZs in biosensing and bioassays while considering both the pros and cons.

Platinum-Copper Bimetallic Colloid Nanoparticle Cluster Nanozymes with Multiple Enzyme-like Activities for Scavenging Reactive Oxygen Species

Fabrication of high-performance artificial antioxidant enzyme (AAE) systems based on a single nanozyme possessing multi-enzymatic activities is fascinating but challenging. Here, polyvinylpyrrolidone (PVP)-platinum-copper nanoparticle clusters (PVP-PtCuNCs) are prepared by a facile one-pot chemical coreduction method. PVP-PtCuNCs possess efficient superoxide dismutase (SOD)-like, peroxidase (POD)-like, and catalase (CAT)-like activities, and the multi-enzymatic activities depend on the bimetal component and cluster structure. Compared with individual platinum nanoparticle clusters (PVP-PtNCs), PVP-PtCuNCs can effectively eliminate reactive oxygen species (ROS) including superoxide anions, hydrogen peroxide, and hydroxyl radicals. The doping of copper not only reduces the usage of Pt content but also improves the catalytic efficiency and versatility effectively through the synergistic effect of bimetal components and the nanocluster structure. The results not only demonstrate that a single bimetallic nanozyme has the potential as an efficient AAE system in the biomedical application but also demonstrate that traditional concepts of structure-activity relationships can be used to fabricate nanozymes with the desired multi-enzymatic activities.

A NiAg-graphene quantum dot-graphene hybrid with high oxidase-like catalytic activity for sensitive colorimetric detection of malathion

This paper reports the synthesis of a nickel-silver-graphene quantum dot-graphene hybrid.

Rapid colorimetric sensing of ascorbic acid based on the excellent peroxidase-like activity of Pt deposited on ZnCo2O4 spheres

Pt/ZnCo₂O₄ composites were firstly found to act as artificial peroxidases and used to construct colorimetric sensing platforms for detecting H₂O₂ and ascorbic acid.