Nanozymes: Definition, Activity, and Mechanisms

Multifunctional MOF: Cold/hot adapted sustainable oxidase-like MOF nanozyme with ratiometric and color tonality for nitrite ions detection

Integrating multiple functionalities into a single entity is highly important, especially when a broad spectrum of application is required. In the present work, we synthesized a novel manganese-based MOF (denoted as UoZ-6) that functions as a cold/hot-adapted and recyclable oxidase nanozyme (Km 0.085 mM) further developed for ratiometric-based colorimetric and color tonality visual-mode detection of nitrite in water and food. Nitrite ions promote the diazotization process of the oxTMB product, resulting in a decay in the absorbance signal at 652 nm and the emergence of a new signal at 461 nm. The dual-absorbance ratiometric platform for nitrite ion detection functions effectively across a wide temperature range (0 °C to 100 °C), offering a linear detection range of 5-45 μM with a detection limit of 0.15 μM using visual-mode. This approach is sensitive, reliable, and selective, making it effective for detecting nitrite ions in processed meat and water.

In-situ nanozyme catalytic amplification coupled with a universal antibody orientation strategy based electrochemical immunosensor for AD-related biomarker

An in-situ nanozyme signal tag combined with a DNA-mediated universal antibody-oriented strategy was proposed to establish a high-performance immunosensing platform for Alzheimer's disease (AD)-related biomarker detection. Briefly, a Zr-based metal-organic framework (MOF) with peroxidase (POD)-like activity was synthesized to encapsulating the electroactive molecule methylene blue (MB), and subsequently modified with a layer of gold nanoparticles on its surface. This led to the creation of double POD-like activity nanozymes surrounding the MB molecule to form a nanozyme signal tag. A large number of hydroxyl radicals were generated by the nanozyme signal tag with the help of H2O2, which catalyzed MB molecules in situ to achieve efficient signal amplification. Subsequently, a DNA-aptamer-mediated universal antibody-oriented strategy was proposed to enhance the binding efficiency for the antigen (target). Meanwhile, a poly adenine was incorporated at the end of the aptamer, facilitating binding to the gold electrode and providing anti-fouling properties due to the hydrophilicity of the phosphate group. Under optimal conditions, this platform was successfully employed for highly sensitive detection of AD-associated tau protein and BACE1, achieving limits of detection with concentrations of 3.34 fg/mL and 1.67 fg/mL, respectively. It is worth mentioning that in the tau immunosensing mode, 20 clinical samples from volunteers of varying ages were analyzed, revealing significantly higher tau expression levels in the blood samples of elderly volunteers compared to young volunteers. This suggests that the developed strategy holds great promise for early AD diagnosis.

Machine learning-assisted melamine-Cu nanozyme and cholinesterase integrated array for multi-category pesticide intelligent recognition

Expanding target pesticide species and intelligent pesticide recognition were formidable challenges for existing cholinesterase inhibition methods. To improve this status, multi-active Mel-Cu nanozyme with mimetic Cu-N sites was prepared for the first time. It exhibited excellent laccase-like and peroxidase-like activities, and can respond to some pesticides beyond the detected range of enzyme inhibition methods, such as glyphosate, carbendazim, fumonisulfuron, etc., through coordination and hydrogen bonding. Inspired by the signal complementarity of Mel-Cu and cholinesterase, an integrated sensor array based on the Mel-Cu laccase-like activity, Mel-Cu peroxidase-like activity, acetylcholinesterase, and butyrylcholinesterase was creatively constructed. And it could successfully discriminate 12 pesticides at 0.5-50 μg/mL, which was significantly superior to traditional enzyme inhibition methods. Moreover, on the basis of above array, a unified stepwise prediction model was built using classification and regression algorithms in machine learning, which enabled concentration-independent qualitative identification as well as precise quantitative determination of multiple pesticide targets, simultaneously. The sensing accuracy was verified by blind sample analysis, in which the species was correctly identified and the concentration was predicted within 10% error, suggesting great intelligent recognition ability. Further, the proposed method also demonstrated significant immunity to interference and practical application feasibility, providing powerful means for pesticide residue analysis.

Peptide nanozymes: An emerging direction for functional enzyme mimics

The abundance of molecules on early Earth likely enabled a wide range of prebiotic chemistry, with peptides playing a key role in the development of early life forms and the evolution of metabolic pathways. Among peptides, those with enzyme-like activities occupy a unique position between peptides and enzymes, combining both structural flexibility and catalytic functionality. However, their full potential remains largely untapped. Further exploration of these enzyme-like peptides at the nanoscale could provide valuable insights into modern nanotechnology, biomedicine, and even the origins of life. Hence, this review introduces the groundbreaking concept of "peptide nanozymes (PepNzymes)", which includes single peptides exhibiting enzyme-like activities, peptide-based nanostructures with enzyme-like activities, and peptide-based nanozymes, thus enabling the investigation of biological phenomena at nanoscale dimensions. Through the rational design of enzyme-like peptides or their assembly with nanostructures and nanozymes, researchers have found or created PepNzymes capable of catalyzing a wide range of reactions. By scrutinizing the interactions between the structures and enzyme-like activities of PepNzymes, we have gained valuable insights into the underlying mechanisms governing enzyme-like activities. Generally, PepNzymes play a crucial role in biological processes by facilitating small-scale enzyme-like reactions, speeding up molecular oxidation-reduction, cleavage, and synthesis reactions, leveraging the functional properties of peptides, and creating a stable microenvironment, among other functions. These discoveries make PepNzymes useful for diagnostics, cellular imaging, antimicrobial therapy, tissue engineering, anti-tumor treatments, and more while pointing out opportunities. Overall, this research provides a significant journey of PepNzymes' potential in various biomedical applications, pushing them towards new advancements.

Dual-enhanced enzyme cascade hybrid hydrogel for the construction of optical biosensor

The biomimetic enzyme cascade system plays a key role in biosensing as a sophisticated signal transduction and amplification strategy. However, constructing a regulated enzyme cascade sensing system remains challenging due to the mismatch of multiple enzyme activities and poor stability. Herein, we design an efficient dual-enhanced enzyme cascade hybrid system (UFD-DEC) containing DNA-controlled nanozymes (Fe-cdDNA) and enzyme (urease) via combining the electrostatic contact effect with the hydrogel-directed confinement effect. Precise modulation of Fe-cdDNA nanozyme by DNA offers a means to control its catalytic efficiency. This regulated UFD-DEC system accelerates the reaction rate and provides remarkable stability compared with the free enzyme system. Benefiting from the plasticity properties of hydrogels, a "lab-in-a-tube" platform was constructed by encapsulating UFD-DEC in a microcentrifuge tube. Such a UFD-DEC-based hydrogel tube exhibits sufficient adaptability to profile urea when used in conjunction with a smartphone-assisted image processing algorithm, which on-site delivers urea information with a detection limit of 0.12 mmol L-1. This customizable and inexpensive miniaturized biosensor platform for monitoring urea may facilitate point-of-care testing applications.

Serum albumin-embedding copper nanoclusters inhibit Alzheimer's β-amyloid fibrillogenesis and neuroinflammation

Increasing evidence suggests that the accumulations of reactive oxygen species (ROS), β-amyloid (Aβ), and neuroinflammation are crucial pathological hallmarks for the onset of Alzheimer's disease (AD), yet there are few effective treatment strategies. Therefore, design of nanomaterials capable of simultaneously elimination of ROS and inhibition of Aβ aggregation and neuroinflammation is urgently needed for AD treatment. Herein, we designed human serum albumin (HSA)-embedded ultrasmall copper nanoclusters (CuNCs@HSA) via an HSA-mediated fabrication strategy. The as-prepared CuNCs@HSA exhibited outstanding multiple enzyme-like properties, including superoxide dismutase (>5000 U/mg), catalase, and glutathione peroxidase activities as well as hydroxyl radicals scavenging ability. Besides, CuNCs@HSA prominently inhibited Aβ fibrillization, and its inhibitory potency was 2.5-fold higher than native HSA. Moreover, CuNCs@HSA could significantly increase the viability of Aβ-treated cells from 60 % to over 96 % at 40 μg/mL and mitigate Aβ-induced oxidative stresses. The secretion of neuroinflammatory cytokines by lipopolysaccharide-induced BV-2 cells, including tumor necrosis factor-α and interleukin-6, was alleviated by CuNCs@HSA. In vivo studies manifested that CuNCs@HSA effectively suppressed the formation of plaques in transgenic C. elegans, reduced ROS levels, and extended C. elegans lifespan by 5 d. This work, using HSA as a template to mediate the fabrication of copper nanoclusters with robust ROS scavenging capability, exhibited promising potentials in inhibiting Aβ aggregation and neuroinflammation for AD treatment.

Emerging Roles of Nanozymes in Plant and Environmental Sectors

The demand for food has increased dramatically as the global population increases, putting more strain on the sustainability of agriculture. To fulfill this requirement, it is imperative to develop brand-new technologies. The application potential of nanozymes in the plant and environmental sectors is progressively becoming apparent as a result of their effective enzymatic catalytic activity and the distinctive characteristics of nanomaterials, including size, specific surface area, optical properties, and thermal properties. Herein, we systematically analyze the catalytic mechanisms of nanozymes with different enzyme-mimetic activities and summarize their applications in improving crop yields by regulating ROS levels and enhancing stress resistance and detecting and removing hazardous pollutants. Finally, we thoroughly analyze the challenges faced by nanozymes regarding size, design, application, economy, and biosafety and look forward to their future development directions to better serve sustainable agriculture.

Nanozyme linked multi-array gas driven sensor for real-time quantitative detection of Group A streptococcus

Group A streptococcus (GAS) is a pathogen typically transmitted through respiratory droplets and skin contact, causing an estimated 700 million mild non-invasive infections worldwide each year. There are approximately 650 000 infections that progress to severe invasive infections, even resulting in death. Therefore, the ability to detect GAS rapidly, accurately and in real time is important. Herein, we developed a nanozyme linked multi-array gas driven sensor (NLMAGS) to point-of-care testing of GAS within 2 h. The NLMAGS demonstrated excellent performance as it combined the advantages of nanozyme techniques, immunoassay techniques, and 3D printing techniques. Platinum- and palladium-rich nanozyme particles (Au@Pt@PdNPs) were synthesized and used to label monocloning antibodies as detection probes. Magnetic beads were labeled with monocloning antibodies as capture probes to establish a double-antibody sandwich immunoassay for the detection of GAS. The sandwich immune complex can catalyze the H2O2 substrate and produce O2. GAS quantification can be achieved by measuring the distance that the O2 pushes the ink drops forward in the sensor. Under optimized conditions, the NLMAGS quantitatively detected 24 spiked samples with a limit of detection (LOD) of 62 CFU mL-1, which was 5 times lower than that of ELISA (334 CFU mL-1). A strong correlation with the conventional ELISA was found (r = 0.99, P < 0.001). In comparison, the traditional lateral flow immunoassay based on Au@Pt@PdNPs-mAb2 (Au@Pt@PdNPs-LFIA) had a LOD of 104 CFU mL-1, which was significantly higher than that of NLMAGS. The NLMAGS demonstrated excellent sensitivity to GAS. The intra- and inter-assay precisions of the sensor were below 15%. Overall, the established NLMAGS has promising potential as a rapid and quantitative method for detecting GAS and can also be used to detect various pathogens.

Coamplified Nanozyme Cocktails for Cascade Reaction-Driven Antioxidant Treatments

Antioxidant nanozymes are powerful tools to combat oxidative stress, which can be further improved by applying nanozyme mixtures of multiple enzymatic function. Here, cocktails of Prussian blue (PB) nanocubes and copper(II) exchanged ZSM-5 zeolites (CuZ) with enhanced reactive oxygen species (ROS) scavenging activity were developed. Surface functionalization of the particles was performed using polymers to obtain stable colloids, i.e., resistant to aggregation, under a wide range of experimental conditions. The nanozyme cocktails possessed advanced antioxidant properties with multiple enzyme-like functions, catalyzing the decomposition of ROS in cascade reactions. The activity of the mixture far exceeded that of the individual particles, particularly in the peroxidase assay, where an improvement of more than an order of magnitude was observed, pointing to coamplification of the enzymatic activity. In addition, it was revealed that the copper(II) site in the CuZ plays an important role in the decomposition of both superoxide radicals and hydrogen peroxide, as it directly catalyzes the former reaction and acts as cocatalyst in the latter process by boosting the peroxidase activity of the PB nanozyme. The results give important insights into the design of synergistic particle mixtures for the broad-spectrum scavenging of ROS to develop efficient tools for antioxidant treatments in both medical therapies and industrial manufacturing processes.

Liver cirrhosis: molecular mechanisms and therapeutic interventions

Liver cirrhosis is the end-stage of chronic liver disease, characterized by inflammation, necrosis, advanced fibrosis, and regenerative nodule formation. Long-term inflammation can cause continuous damage to liver tissues and hepatocytes, along with increased vascular tone and portal hypertension. Among them, fibrosis is the necessary stage and essential feature of liver cirrhosis, and effective antifibrosis strategies are commonly considered the key to treating liver cirrhosis. Although different therapeutic strategies aimed at reversing or preventing fibrosis have been developed, the effects have not be more satisfactory. In this review, we discussed abnormal changes in the liver microenvironment that contribute to the progression of liver cirrhosis and highlighted the importance of recent therapeutic strategies, including lifestyle improvement, small molecular agents, traditional Chinese medicine, stem cells, extracellular vesicles, and gut remediation, that regulate liver fibrosis and liver cirrhosis. Meanwhile, therapeutic strategies for nanoparticles are discussed, as are their possible underlying broad application and prospects for ameliorating liver cirrhosis. Finally, we also reviewed the major challenges and opportunities of nanomedicine‒biological environment interactions. We hope this review will provide insights into the pathogenesis and molecular mechanisms of liver cirrhosis, thus facilitating new methods, drug discovery, and better treatment of liver cirrhosis.

Mitochondria-targeting Cu2-xSe-TPP with dual enzyme activity alleviates Alzheimer's disease by modulating oxidative stress

Mitochondrial dysfunction in microglia has been implicated as a key pathogenesis of most neurodegenerative diseases including Alzheimer's disease (AD). Abnormal production of reactive oxygen species (ROS) and neuroinflammation caused by mitochondrial oxidative stress are important factors leading to neuronal death in AD. Herein, a "dual brake" strategy to synergistically halt mitochondrial dysfunction and neuroinflammation targeting mitochondria in microglia is proposed. To achieve this goal, (3-carboxypropyl) triphenyl-phosphonium bromide (TPP)-modified Cu2-xSe nanozymes (Cu2-xSe-TPP NPs) with dual enzyme-like activities was designed. Cu2-xSe-TPP NPs with superoxide dismutase-mimetic (SOD) and catalase-mimetic (CAT) activities can effectively scavenge ROS in the mitochondria of microglia and relieve mitochondrial oxidative stress. In vivo studies demonstrated that Cu2-xSe-TPP NPs can alleviate oxidative stress and promote neuroprotection in the hippocampus of AD model mice. In addition, Cu2-xSe-TPP NPs can regulate the polarization of microglia from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype, promote Aβ phagocytosis and reshape the AD inflammatory microenvironment, thus effectively attenuating AD neuropathology and rescuing cognitive deficits in AD model mice. Taken together, this strategy preventing mitochondrial damage and remodeling the inflammatory microenvironment will provide a new perspective for AD therapy.

Ultra-small platinum nano-enzymatic spray with ROS scavenging and anti-inflammatory properties for photoaging treatment

Photoaging induced by ultraviolet (UV) results in oxidative stress and inflammation. Noble metal nanozymes have strong antioxidant and anti-inflammatory capacity, which are expected to eliminate the excessive reactive oxygen species (ROS) and inflammatory factors in the photoaged skin. Hence, we have synthesized ultrasmall platinum nanoparticles coated with polyvinylpyrrolidone (Pt NPs) with a diameter of nearly 5 nm for photoaging treatment. Thanks to multi-enzymatic capacities (catalase, peroxidase, and superoxide dismutase) of Pt NPs, they can effectively protect fibroblasts from UV-induced ROS attack, relieve fibroblasts from UV-induced cell cycle arrest, downregulate matrix metalloproteinases (MMPs) to regenerate type I collagen, and inhibit M1 macrophage polarization to decrease the expression of inflammatory factors. For photoaged mice treatment, we employ the concept of routine spray skincare and encapsulate Pt NPs solution in a spray bottle. In combination with roller needle, following Pt NPs nano-enzymatic spray given, UV-induced photoaged mice display reduced wrinkle formation in the collagen-depleted dermal tissue of mice and more youthful performance in both appearance and organizational structure. Consequently, multi-enzymatic functions of Pt NPs nano-spray offers a promising avenue for anti-photoaging therapy, providing potential benefits in both preventative and restorative skincare applications.

Nanozymes: Classification and Analytical Applications - A Review

The recent discovery of a new class of nanomaterials called nanozymes, which have the action of enzymes and are thus of tremendous significance, has altered our understanding of these previously believed to be biologically inert nanomaterials. As a significant and exciting class of synthetic enzymes, nanozymes have distinct advantages over natural enzymes. They are less expensive, more stable, and easier to work with and store, making them a viable substitute. This practical advantage of nanozymes over natural enzymes reassures us about the potential of this new technology. Peroxidase-like nanozymes have been investigated for the purpose of creating adaptable biosensors via the use of molecularly imprinted polymers (MIPs) or particular bio recognition ligands, including enzymes, antibodies, and aptamers. This review delves into the distinctions between synthetic and natural enzymes, explaining their structures and analytical applications. It primarily focuses on carbon-based nanozymes, particularly those that contain both carbon and hydrogen, as well as metal-based nanozymes like Fe, Cu, and Au, along with their metal oxide (FeO, CuO), which have applications in many fields today. Analytical chemistry finds great use for nanozymes for sensing and other applications, particularly in comparison with other classical methods in terms of selectivity and sensitivity. Nanozymes, with their unique catalytic capabilities, have emerged as a crucial tool in the early diagnosis of COVID-19. Their application in nanozyme-based sensing and detection, particularly through colorimetric and fluorometric methods, has significantly advanced our ability to detect the virus at an early stage.

A point of care sensor for detection of alcohols, aldehydes and esters in urinary metabolites of war veterans injured by sulfur mustard

To discriminate between different alcoholic, aldehyde, and ester species of urine samples, a colorimetric sensor array consisting of dopamine-capped copper-silver bimetallic nanoparticles (Ag@Cu BMNPs) combined with 12 organic dyes is introduced. Based on the sensing mechanism, the nanozyme catalyzed the reactions of oxidation, dehydrogenation, and hydrolysis of volatile organic compounds. The products could alter the amount of hydronium ions in the detection media, making a variation in the color intensity of pH-sensitive indicators. Also, they could be connected to other organic dyes through nucleophilic/electrophilic or H-bonding interactions in order to form new complexes. The colorimetric responses of the sensor were visible to the naked eye and evaluated by image analysis software, thereby obtaining a unique detection pattern for each sample. The statistical data indicated that the sensor can completely distinguish between compounds with different functional groups. As a practical study, the efficiency of the sensor was investigated for the identification of the war veterans who injured by sulfur mustard in Iran-Iraq war and their differentiation from control people. Based on the output of the assay, the sensor was found to create a special color pattern for each studied group, achieving a total accuracy of 78.0% for this discrimination. The color change of the proposed sensor has a good correlation with the severity of the injury, being independent of the metabolic changes caused by the age of the participants. Accordingly, the fabricated sensor array can be a suitable tool to detect oxygen-containing compounds in environmental or biological samples.

Surface Au-H Species as Self-Generated Prosthetic Groups of a Formate Dehydrogenase-like Au Nanozyme to Engineer Multienzymatic Activities

Although the past decade has witnessed a rapid development of oxidoreductase-mimicking nanozymes, the mimicry of cofactors that play key roles in mediating electron and proton transfer remains limited. This study explores how surface Au-H species conjugated to Au nanoparticles (NPs) that imitate formate dehydrogenase (FDH) can serve as cofactors, analogous to NADH in natural enzymes, offering diverse possibilities for FDH-mimicking Au nanozymes to mimic various enzymes. Once O2 is present, Au-H species assist Au NPs to complete the on-demand H2O2 generation for cascade reactions. Alternatively, when oxidizing organic molecules are introduced as substrates, Au-H species confer nitro reductase- and aldehyde reductase-like activities on Au NPs under anaerobic conditions. Furthermore, similar to the dehydrogenase-NADH complex, Au NPs possessing Au-H species are gifted with esterase-like activity for ester hydrolysis. By revealing that Au-H species are prosthetic groups for FDH-mimicking Au nanozymes, this work may inspire explorations into future self-generated cofactor mimics for nanozymes, thereby circumventing the need for exogenous cofactors.

Unveiling Generally-ignored Co-substrate Effect of Catalase-inherent Peroxidase Mimic for Self-verifiable Detection of High-concentration Hydrogen Peroxide

One nanoparticle possessing both peroxidase (POD) and catalase (CAT) activities is a prevalent co-substrate nanozyme system, distinct from the extensively researched cascade nanozyme system. During the sensing of hydrogen peroxide by POD, the impact of CAT is actually ignored in most studies. In this study, the CAT effect on hydrogen peroxide detection is thoroughly investigated based on POD catalysis by finely tuning the relative activity of POD and CAT. It is discovered that the CAT effect can be changed by delaying the injection of chromogenic substrate after adding hydrogen peroxide and that the linear range grows with the delayed time. Then, a theoretical mechanism showed that the time-delay mediated CAT effect magnification does not change the Vmax, but it causes Km to linearly increase with delayed time, consistent with the experiment results. Furthermore, the detection of high concentrations of hydrogen peroxide is successfully realized in contact lens care solutions by utilizing time-delay-mediated POD/CAT nanozyme. On the other hand, its linear range-tunable characteristic is used to produce multiple standard curves, then enabled self-verifying hydrogen peroxide detection. Overall, this work investigates the role of CAT in CAT-inherent POD nanozymes both theoretically and experimentally, and confirms POD/CAT nanozyme's priority in developing high-performance sensors.

Hollow Cu/CoS2 Nanozyme with Defect-Induced Enzymatic Catalytic Sites and Binding Pockets for Highly Sensitive Fluorescence Detection of Alkaline Phosphatase

Along with an ever-deepening understanding of the catalytic principle of natural enzymes, the rational design of high-activity biomimetic nanozymes has become a hot topic in current research. Inspired by the active centers of natural enzymes consisting of catalytic sites and binding pockets, a Cu-doped CoS2 hollow nanocube (Cu/CoS2 HNCs) nanozyme integrating substitution defects and vacancies is developed through a defect engineering strategy. It is shown that the vacancies and substitution defects in the developed Cu/CoS2 HNC nanozymes serve as binding pockets and catalytic sites, respectively. The construction of this key active center and the accelerated electron transfer from the Co/Cu redox cycle significantly improve the substrate affinity and catalytic efficiency of the Cu/CoS2 HNCs nanozymes, which results in the excellent catalytic performance of the Cu/CoS2 HNC nanozymes. Using the superior enzymatic activity of Cu/CoS2 HNCs, a fluorescence detection platform for alkaline phosphatase (ALP) is established, which is a wider detection range and lower limit of detection (LOD) than previous work. This work broadens the family of nanozymes and provide a new idea for the development of novel nanozymes with high enzyme activity, as well as a guideline for the construction of highly sensitive fluorescent sensors.

Monodispersed Au nanoparticles decorated MoS2 nanosheets with enhanced peroxidase-like activity based electrochemical H2O2 sensing for anticancer drug evaluations

BACKGROUND

The unique size, physical and chemical properties, and ultra-high stability of nanozymes have attracted extensive attentions in sensing, but improvement of catalytic activity of the nanozymes is still an urgent issue. Given the ultra-high simulated enzyme activity of metal nanoparticles and the advantage of multi-enzyme catalysis, an Au-decorated MoS2 nanosheets (MoS2/Au NS) integrating the double peroxidase-like (POD) activity is developed.

RESULTS

By optimizing and adjusting the density of AuNPs, as well as its morphology and other parameters, a monodisperse and high-density distribution of AuNPs on MoS2 nanosheets was obtained, which can greatly improve the POD-like activity of MoS2/Au NS. Nafion solution was applied to assist the modification of MoS2/Au NS on the electrode surface so as to improved its stability. An electrochemical H2O2 detection platform was constructed by modifying MoS2/Au NS nanozyme on the SPCE using the conductive Nafion solution. And the negatively charged sulfonic acid group can eliminate negatively charged electroactive substances to improve the specificity. Then ascorbic acid was used to stimulate tumor cells to produce H2O2 as therapeutic model, an ultrasensitive chronocoulometry detection for H2O2 in cell lysate was established. The logarithmically of ΔQ and the logarithmically of H2O2 concentration showed a good linear relationship between 1 μM and 500 mM, with a LOD value of 0.3 μM.

SIGNIFICANCE

The developed H2O2 sensor has excellent stability, reproducibility (RSD = 2.3 %, n = 6) and selectivity, realized the quantitative detection of H2O2 in cell lysate. Compared with commercial fluorescence detection kits for H2O2 in cell lysate, it is worth mentioning that the electrochemical H2O2 sensor developed in this study is simpler and faster, with higher sensitivity and lower cost. This provides a potential substitute for disease diagnosis and treatment evaluation based on accurate detection of H2O2.

Infectious and Inflammatory Microenvironment Self-Adaptive Artificial Peroxisomes with Synergetic Co-Ru Pair Centers for Programmed Diabetic Ulcer Therapy

Complex microenvironments with bacterial infection, persistent inflammation, and impaired angiogenesis are the major challenges in chronic refractory diabetic ulcers. To address this challenge, a comprehensive strategy with highly effective and integrated antimicrobial, anti-inflammatory, and accelerated angiogenesis will offer a new pathway to the rapid healing of infected diabetic ulcers. Here, inspired by the tunable reactive oxygen species (ROS) regulation properties of natural peroxisomes, this work reports the design of infectious and inflammatory microenvironments self-adaptive artificial peroxisomes with synergetic Co-Ru pair centers (APCR) for programmed diabetic ulcer therapy. Benefiting from the synergistic Co and Ru atoms, the APCR can simultaneously achieve ROS production and metabolic inhibition for bacterial sterilization in the infectious microenvironment. After disinfection, the APCR can also eliminate ROS to alleviate oxidative stress in the inflammatory microenvironment and promote wound regeneration. The data demonstrate that the APCR combines highly effective antibacterial, anti-inflammatory, and provascular regeneration capabilities, making it an efficient and safe nanomedicine for treating infectious and inflammatory diabetic foot ulcers via a programmed microenvironment self-adaptive treatment pathway. This work expects that synthesizing artificial peroxisomes with microenvironments self-adaptive and bifunctional enzyme-like ROS regulation properties will provide a promising path to construct ROS catalytic materials for treating complex diabetic ulcers, trauma, or other infection-caused diseases.

Catalase immobilization: Current knowledge, key insights, applications, and future prospects - A review

Catalase (CAT), a ubiquitous enzyme in all oxygen-exposed organisms, effectively decomposes hydrogen peroxide (H2O2), a harmful by-product, into water and oxygen, mitigating oxidative stress and cellular damage, safeguarding cellular organelles and tissues. Therefore, CAT plays a crucial role in maintaining cellular homeostasis and function. Owing to its pivotal role, CAT has garnered considerable interest. However, many challenges arise when used, especially in multiple practical processes. "Immobilization", a widely-used technique, can help improve enzyme properties. CAT immobilization offers numerous advantages, including enhanced stability, reusability, and facilitated downstream processing. This review presents a comprehensive overview of CAT immobilization. It starts with discussing various immobilization mechanisms, support materials, advantages, drawbacks, and factors influencing the performance of immobilized CAT. Moreover, the review explores the application of the immobilized CAT in various industries and its prospects, highlighting its essential role in diverse fields and stimulating further research and investigation. Furthermore, the review highlights some of the world's leading companies in the field of the CAT industry and their substantial potential for economic contribution. This review aims to serve as a discerning, source of information for researchers seeking a comprehensive cutting-edge overview of this rapidly evolving field and have been overwhelmed by the size of publications.

Rational design of Au-Bi bimetallic nanozyme for NIR-II laser mediated multifunctional combined tumor therapy

To maximize the therapeutic effects and minimize the adverse effects of synergistic tumor therapies, a multifunctional nanozyme Au-Bi/ZIF-8@DOX@HA (ABZ@DOX@HA) was designed and synthesized through the Au and Bi bimetallic doping of ZIF-8, loading of the DOX, and modifying with hyaluronic acid (HA). The ABZ@DOX@HA nanoparticles (NPs) could simulate the enzymatic activities of glucose oxidase (GOx) and peroxidase (POD). Upon irradiated by near-infrared region (NIR-II) laser, the strong synergism of the photothermal abilities of the loaded Au and Bi nanodots accelerated the collapse of the ABZ structure at the tumor site considerably and released Au, Bi nanodots and DOX. The results in vitro and in vivo proved that ABZ@DOX@HA nanozyme could effectively exert the combined tumor therapy of starvation treatment, photothermal therapy (PTT), chemodynamic therapy (CDT) and chemotherapy. The current research provides a new strategy to address the inherent challenges of easy clearance and short blood circulation of small-sized NPs during the treatment of tumors with nanomedicine, as well as the aggregation and oxidation of inorganic nanodots.

Electronic structure engineering of N-doped carbon nanozyme via incorporating Cl and sp3-hybridized defected carbon for organophosphorus pesticides assay

Metal-free carbon-based nanozymes often exhibit superior chemical stability and detection reliability compared to their metal-doped counterparts. However, their catalytic activity remains an area ripe for further enhancement. Herein, we successfully prepared a chlorine (Cl)-modified, metal-free, and porous N-doped carbon nanozyme (Clx-pNC) via NaCl molten etching. The incorporation of Cl induced an increase in the intrinsic defects of sp3-hybridized carbon within Clx-pNC and optimized the electronic structure of the N-connected carbon atoms. Remarkably, the peroxidase (POD)-like activity of Clx-pNC was enhanced twelvefold compared to porous N-doped carbon (pNC). Theoretical simulations highlighted that the introduction of Cl not only promoted H2O2 adsorption but also lowered the energy barrier for its decomposition, facilitating the generation of active intermediates and thus boosting POD-like activity. Based on the POD mimic activity of Clx-pNC, we developed a colorimetric platform for OPs detection utilizing a cascade amplification strategy. This work provides insights into the rational design of carbon-based nanozymes and the development of nanozyme-based colorimetric biosensors.

Colorimetric detection of Staphylococcus aureus with enhanced sensitivity based on phage covalently immobilized Co3O4 nanozyme through synergistic inhibition effect

Staphylococcus aureus (S. aureus) is a common foodborne pathogen, posing a serious threat to public health. Consequently, it is crucial to establish a platform for sensitive and specific determination of S. aureus in food. Herein, phage SapYZUH5, isolated by our lab, was covalently immobilized on Co3O4 to synthesize SapYZUH5@Co3O4. Notably, SapYZUH5@Co3O4 exhibited remarkable oxidase-like activity, enabling the catalysis of dissolved oxygen to generate superoxide anion free radicals and accelerate the TMB chromogenic reaction. Upon introduction of S. aureus, specific capture by SapYZUH5@Co3O4 resulted in inhibiting its oxidase-like activity and decelerating the 3,3',5,5'-tetramethylbenzidine (TMB) chromogenic reaction. Moreover, S. aureus can be lysed to release the reductive bacterial contents, which can further inhibit the TMB chromogenic reaction. Based on this principle, SapYZUH5@Co3O4 + TMB reaction system was employed for detection with enhanced sensitivity of S. aureus, yielding an equation: A =  - 0.092 Log (CSA) + 0.79 (R2 = 0.987), with an ultralow limit of detection (LOD) of 28 CFU mL-1. This system exhibited remarkable specificity and anti-interfere towards S. aureus, owing to the excellent affinity of SapYZUH5 towards S. aureus. In addition, S. aureus in the actual food samples was detected using this system, yielding recoveries ranging from 96.34 to 109.43%, demonstrating its exceptional accuracy. Hence, our proposed covalent immobilization of phage on the nanozyme can realize sensitive and specific colorimetric determination of S. aureus in food samples.

Engineering inorganic nanozyme architectures for decomposition of reactive oxygen species

Enzyme-mimicking nanomaterials (nanozymes) with antioxidant activity are at the forefront of research efforts towards biomedical and industrial applications. The selection of enzymatically active substances and their incorporation into novel inorganic nanozyme structures is critically important for this field of research. To this end, the fabrication of composites can be desirable as these can either exhibit multiple enzyme-like activities in a single material or show increased activity compared to the nanozyme components. Conversely, by modifying the structure of a nanomaterial, enzyme-like activities can be induced in formerly inert particles. We identify herein the three main routes of composite nanozyme synthesis, namely, surface functionalization of a particle with another compound, heteroaggregation of individual nanozymes, and modification of the bulk nanozyme structure to achieve optimal antioxidant activity. We discuss in particular the different inorganic support materials used in the synthesis of nanozyme architectures and the advantages brought forth by the use of composites.

Oxygen-bridged W-Pd atomic pairs enable H2O2 activation for sensitive immunoassays

Regulating the performance of peroxidase (POD)-like nanozymes is a prerequisite for achieving highly sensitive and accurate immunoassays. Inspired by natural enzyme catalysis, we design a highly active and selective nanozyme by loading atomically dispersed tungsten (W) sites on Pd metallene (W-O-Pdene) to construct an artificial three-dimensional (3D) catalytic center. The 3D asymmetric W-O-Pd atomic pairs can effectively stretch the O-O bonds in H2O2 and further promote the desorption of H2O to enhance POD-like activity. Moreover, the W-O-Pd sites with unique spatial structures demonstrate satisfactory specificity for H2O2 activation, effectively preventing the interference of dissolved oxygen. Accordingly, the highly active and specific W-O-Pdene nanozymes are utilized for sensitive and accurate prostate-specific antigen (PSA) immunoassay with a low detection limit of 1.92 pg mL-1, superior to commercial enzyme-linked immunosorbent assay.

Bimetallic Single-Atom Nanozyme-Based Electrochemical-Photothermal Dual-Function Portable Immunoassay with Smartphone Imaging

Rapid and accurate detection of human epidermal growth factor receptor 2 (HER2) is crucial for the early diagnosis and prognosis of breast cancer. In this study, we reported an iron-manganese ion N-doped carbon single-atom catalyst (FeMn-NCetch/SAC) bimetallic peroxidase mimetic enzyme with abundant active sites etched by H2O2 and further demonstrated unique advantages of single-atom bimetallic nanozymes in generating hydroxyl radicals by density functional theory (DFT) calculations. As a proof of concept, a portable device-dependent electrochemical-photothermal bifunctional immunoassay detection platform was designed to achieve reliable detection of HER2. In the enzyme-linked reaction, H2O2 was generated by substrate catalysis via secondary antibody-labeled glucose oxidase (GOx), while FeMn-NCetch/SAC nanozymes catalyzed the decomposition of H2O2 to form OH*, which catalyzed the conversion of 3,3',5,5'-tetramethylbenzidine (TMB) to ox-TMB. The ox-TMB generation was converted from the colorimetric signals to electrical and photothermal signals by applied potential and laser irradiation, which could be employed for the quantitative detection of HER2. With the help of this bifunctional detection technology, HER2 was accurately detected in two ways: photothermally, with a linear scope of 0.01 to 2.0 ng mL-1 and a limit of detection (LOD) of 7.5 pg mL-1, and electrochemically, with a linear scope of 0.01 to 10 ng mL-1 at an LOD of 3.9 pg mL-1. By successfully avoiding environmental impacts, the bifunctional-based immunosensing strategy offers strong support for accurate clinical detection.

Nanozyme-Enabled Biomedical Diagnosis: Advances, Trends, and Challenges

As nanoscale materials with the function of catalyzing substrates through enzymatic kinetics, nanozymes are regarded as potential alternatives to natural enzymes. Compared to protein-based enzymes, nanozymes exhibit attractive characteristics of low preparation cost, robust activity, flexible performance adjustment, and versatile functionalization. These advantages endow them with wide use from biochemical sensing and environmental remediation to medical theranostics. Especially in biomedical diagnosis, the feature of catalytic signal amplification provided by nanozymes makes them function as emerging labels for the detection of biomarkers and diseases, with rapid developments observed in recent years. To provide a comprehensive overview of recent progress made in this dynamic field, here an overview of biomedical diagnosis enabled by nanozymes is provided. This review first summarizes the synthesis of nanozyme materials and then discusses the main strategies applied to enhance their catalytic activity and specificity. Subsequently, representative utilization of nanozymes combined with biological elements in disease diagnosis is reviewed, including the detection of biomarkers related to metabolic, cardiovascular, nervous, and digestive diseases as well as cancers. Finally, some development trends in nanozyme-enabled biomedical diagnosis are highlighted, and corresponding challenges are also pointed out, aiming to inspire future efforts to further advance this promising field.

Ce12V6 Clusters with Multi-Enzymatic Activities for Sepsis Treatment

Artificial enzymes, especially nanozymes, have attracted wide attention due to their controlled catalytic activity, selectivity, and stability. The rising Cerium-based nanozymes exhibit unique SOD-like activity, and Vanadium-based nanozymes always hold excellent GPx-like activity. However, most inflammatory diseases involve polymerase biocatalytic processes that require multi-enzyme activities. The nanocomposite can fulfill multi-enzymatic activity simultaneously, but large nanoparticles (>10 nm) cannot be excreted rapidly, leading to biosafety challenges. Herein, atomically precise Ce12V6 clusters with a size of 2.19 nm are constructed. The Ce12V6 clusters show excellent glutathione peroxidase (GPx) -like activity with a significantly lower Michaelis-Menten constant (Km, 0.0125 mM versus 0.03 mM of natural counterpart) and good activities mimic superoxide dismutase (SOD) and peroxidase (POD). The Ce12V6 clusters exhibit the ability to scavenge the ROS including O2 ·- and H2O2 via the cascade reactions of multi-enzymatic activities. Further, the Ce12V6 clusters modulate the proinflammatory cytokines including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) and consequently rescue the multi-organ failure in the lipopolysaccharide (LPS)-induced sepsis mouse model. With excellent biocompatibility, the Ce12V6 clusters show promise in the treatment of sepsis.

Gold brocade coated CoFe PBA with enhanced peroxidase-like activity for a chemiluminescent imaging immunoassay

Traditional chemiluminescence (CL) imaging immunoassays usually rely on natural enzymes as catalytic probes, which has hampered their extensive application due to the susceptibility to inactivation of natural enzymes. In response, a gold brocade coated CoFe Prussian blue analogue (CoFe PBA@Au brocade) with enhanced peroxidase-like activity was synthesized and utilized as a powerful label probe for constructing a highly sensitive CL imaging immunosensor targeting disease biomarkers with excellent performance. This research offers a universal strategy for enhancing the sensitivity of CL imaging immunoassays and further expands the application of PBA nanozymes.

Fe/Cu MOFs of Fe2+-rich and Cu-doping via in situ reduction as nanozyme for peroxidase-like catalycity enhancement

Fe-MOFs of mixed valence was synthesized by a solvothermal method via the in-situ reduction of ethylene glycol (EG) pre-coordination with the proper ratio of Fe2+/Fe3+ between 0.83 and 2.46. Synchronously with copper introduction, the Fe/Cu MOFs of mixed valence (Fe/Cu-MVMOFs) was then one pot acquired to remarkably improve the affinity of Fe2+ and Cu+ to H2O2 and promote the conversion efficiency of Fe2+/Fe3+ via the electron transfer among Fe-Cu bimetal clusters (XPS and XRD). Hence, the maximum reaction rate of H2O2 with Fe/Cu-MVMOFs reached 16.65 M·s-1, along with Km as low as 0.0479 mM. H2O2 and glutathione (GSH) were efficiently detected, ranging from 0.25 to 60 µM and from 0.2 to 40 µM, respectively. The investigation of catalyzation selectivity and practical serum detection by Fe/Cu-MVMOFs illustrated the efficacy and efficiency, denoting Fe/Cu-MVMOFs as the promising peroxidase candidate.

Enhancing radiation-resistance and peroxidase-like activity of single-atom copper nanozyme via local coordination manipulation

The inactivation of natural enzymes by radiation poses a great challenge to their applications for radiotherapy. Single-atom nanozymes (SAzymes) with high structural stability under such extreme conditions become a promising candidate for replacing natural enzymes to shrink tumors. Here, we report a CuN3-centered SAzyme (CuN3-SAzyme) that exhibits higher peroxidase-like catalytic activity than a CuN4-centered counterpart, by locally regulating the coordination environment of single copper sites. Density functional theory calculations reveal that the CuN3 active moiety confers optimal H2O2 adsorption and dissociation properties, thus contributing to high enzymatic activity of CuN3-SAzyme. The introduction of X-ray can improve the kinetics of the decomposition of H2O2 by CuN3-SAzyme. Moreover, CuN3-SAzyme is very stable after a total radiation dose of 500 Gy, without significant changes in its geometrical structure or coordination environment, and simultaneously still retains comparable peroxidase-like activity relative to natural enzymes. Finally, this developed CuN3-SAzyme with remarkable radioresistance can be used as an external field-improved therapeutics for enhancing radio-enzymatic therapy in vitro and in vivo. Overall, this study provides a paradigm for developing SAzymes with improved enzymatic activity through local coordination manipulation and high radioresistance over natural enzymes, for example, as sensitizers for cancer therapy.

Arginine-Rich Peptide-Rhodium Nanocluster@Reduced Graphene Oxide Composite as a Highly Selective and Active Uricase-like Nanozyme for the Degradation of Uric Acid and Inhibition of Urate Crystal

Metal nanozymes have offered attractive opportunities for biocatalysis and biomedicine. However, fabricating nanozymes simultaneously possessing highly catalytic selectivity and activity remains a great challenge due to the lack of three-dimensional (3D) architecture of the catalytic pocket in natural enzymes. Here, we integrate rhodium nanocluster (RhNC), reduced graphene oxide (rGO), and protamine (PRTM, a typical arginine-rich peptide) into a composite facilely based on the single peptide. Remarkably, the PRTM-RhNC@rGO composite displays outstanding selectivity, activity, and stability for the catalytic degradation of uric acid. The reaction rate constant of the uric acid oxidation catalyzed by the PRTM-RhNC@rGO composite is about 1.88 × 10-3 s-1 (4 μg/mL), which is 37.6 times higher than that of reported RhNP (k = 5 × 10-5 s-1, 20 μg/mL). Enzyme kinetic studies reveal that the PRTM-RhNC@rGO composite exhibits a similar affinity for uric acid as natural uricase. Furthermore, the uricase-like activity of PRTM-RhNC@rGO nanozymes remains in the presence of sulfur substances and halide ions, displaying incredibly well antipoisoning abilities. The analysis of the structure-function relationship indicates the PRTM-RhNC@rGO composite features the substrate binding site near the catalytic site in a confined space contributed by 2D rGO and PRTM, resulting in the high-performance of the composite nanozyme. Based on the outstanding uricase-like activity and the interaction of PRTM and uric acid, the PRTM-RhNC@rGO composite can retard the urate crystallization significantly. The present work provides new insights into the design of metal nanozymes with suitable binding sites near catalytic sites by mimicking pocket-like structures in natural enzymes based on simple peptides, conducing to broadening the practical application of high-performance nanozymes in biomedical fields.

[Advances in the Application of Nanozymes in Joint Disease Therapy]

Nanozymes are nanoscale materials with enzyme-mimicking catalytic properties. Nanozymes can mimic the mechanism of natural enzyme molecules. By means of advanced chemical synthesis technology, the size, shape, and surface characteristics of nanozymes can be accurately regulated, and their catalytic properties can be customized according to the specific need. Nanozymes can mimic the function of natural enzymes, including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx), to scavenge reactive oxygen species (ROS). Reported findings have shown that nanozymes have the advantages of excellent stability, low cost, and adjustable catalytic activity, thereby showing great potential and broad prospects in the application of disease treatment. Herein, we reviewed the advances in the application of nanozymes in the treatment of joint diseases. The common clinical manifestations of joint diseases include joint pain, swelling, stiffness, and limited mobility. In severe cases, joint diseases may lead to joint destruction, deformity, and functional damage, entailing crippling socioeconomic burdens. ROS is a product of oxidative stress. Increased ROS in the joints can induce macrophage M1 type polarization, which in turn induces and aggravates arthritis. Therefore, the key to the treatment of joint diseases lies in ROS scavenging and increasing oxygen (O2) content. Nanozymes have demonstrated promising application potential in the treatment of joint diseases, including rheumatoid arthritis, osteoarthritis, and gouty arthritis. However, how to ensure their biosafety, reduce the toxicity, and increase enzyme activity remains the main challenge in current research. Precise control of the chemical composition, size, shape, and surface modification of nanomaterials is the main development direction for the future.

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.

Fine-Tuning Electron Transfer for Nanozyme Design

Nanozymes, with their versatile composition and structural adaptability, present distinct advantages over natural enzymes including heightened stability, customizable catalytic activity, cost-effectiveness, and simplified synthesis process, making them as promising alternatives in various applications. Recent advancements in nanozyme research have shifted focus from serendipitous discovery toward a more systematic approach, leveraging machine learning, theoretical calculations, and mechanistic explorations to engineer nanomaterial structures with tailored catalytic functions. Despite its pivotal role, electron transfer, a fundamental process in catalysis, has often been overlooked in previous reviews. This review comprehensively summarizes recent strategies for modulating electron transfer processes to fine-tune the catalytic activity and specificity of nanozymes, including electron-hole separation and carrier transfer. Furthermore, the bioapplications of these engineered nanozymes, including antimicrobial treatments, cancer therapy, and biosensing are also introduced. Ultimately, this review aims to offer invaluable insights for the design and synthesis of nanozymes with enhanced performance, thereby advancing the field of nanozyme research.

Magnetic Immunoassay Based on Au Pt Bimetallic Nanoparticles/Carbon Nanotube Hybrids for Sensitive Detection of Tetracycline Antibiotics

Misusage of tetracycline (TC) antibiotics residue in animal food has posed a significant threat to human health. Therefore, there is an urgent need to develop highly sensitive and robust assays for detecting TC. In the current study, gold and platinum nanoparticles were deposited on carbon nanotubes (CNTs) through the superposition method (Au@Pt/CNTs-s) and one-pot method (Au@Pt/CNTs-o). Au@Pt/CNTs-s displayed higher enzyme-like activity than Au@Pt/CNTs-o, which were utilized for the development of sensitive magnetic immunoassays. Under the optimized conditions, the limits of detection (LODs) of magnetic immunoassays assisted by Au@Pt/CNTs-s and Au@Pt/CNTs-o against TCs could reach 0.74 ng/mL and 1.74 ng/m, respectively, which were improved 6-fold and 2.5-fold in comparison with conventional magnetic immunoassay. In addition, the measurement of TC-family antibiotics was implemented by this assay, and ascribed to the antibody used that could recognize TC, oxytetracycline, chlortetracycline, and doxycycline with high cross-reactivity. Furthermore, the method showed good accuracy (recoveries, 92.1-114.5% for milk; 88.6-92.4% for pork samples), which also were applied for determination of the targets in real samples. This study provides novel insights into the rapid detection of targets based on high-performance nanocatalysts.

Ultrasmall CuMn-His Nanozymes with Multienzyme Activity at Neutral pH: Construction of a Colorimetric Sensing Array for Biothiol Detection and Disease Identification

Biothiol assays offer vital insights into health assessment and facilitate the early detection of potential health issues, thereby enabling timely and effective interventions. In this study, we developed ultrasmall CuMn-Histidine (His) nanozymes with multiple enzymatic activities. CuMn-His enhanced peroxidase (POD)-like activity at neutral pH was achieved through hydrogen bonding and electrostatic effects. In addition, CuMn-His possesses laccase (LAC)-like and superoxide dismutase (SOD)-like activities at neutral pH. Based on three different enzyme mimetic activities of CuMn-His at neutral pH, the colorimetric sensing array without changing the buffer solution was successfully constructed. The array was successfully used for the identification of three biothiols, glutathione (GSH), cysteine (Cys), and homocysteine (Hcy). Subsequently, excellent application results were shown in complex serum and cellular level analyses. This study provides an innovative strategy for the development of ultrasmall bimetallic nanozymes with multiple enzymatic activities and the construction of colorimetric sensing arrays.

Functional Nanomaterials for the Treatment of Osteoarthritis

Osteoarthritis (OA) is the most common degenerative joint disease, affecting more than 595 million people worldwide. Nanomaterials possess superior physicochemical properties and can influence pathological processes due to their unique structural features, such as size, surface interface, and photoelectromagnetic thermal effects. Unlike traditional OA treatments, which suffer from short half-life, low stability, poor bioavailability, and high systemic toxicity, nanotherapeutic strategies for OA offer longer half-life, enhanced targeting, improved bioavailability, and reduced systemic toxicity. These advantages effectively address the limitations of traditional therapies. This review aims to inspire researchers to develop more multifunctional nanomaterials and promote their practical application in OA treatment.

Self-assembled copper-based nanoparticles for enzyme catalysis-enhanced chemodynamic/photodynamic/antiangiogenic tritherapy against hepatocellular carcinoma

As an emerging cancer treatment strategy, reactive oxygen species-based tumor catalytic therapies face enormous challenges due to hypoxia and the overexpression of glutathione (GSH) in the tumor microenvironment. Herein, a self-assembled copper-based nanoplatform, TCCHA, was designed for enzyme-like catalysis-enhanced chemodynamic/photodynamic/antiangiogenic tritherapy against hepatocellular carcinoma. TCCHA was fabricated from Cu2+, 3,3'-dithiobis (propionohydrazide), and photosensitizer chlorine e6 via a facile one-pot self-assembly strategy, after which an aldehyde hyaluronic acid was coated, followed by loading of the antivascular drug AL3818. The obtained TCCHA nanoparticles exhibited pH/GSH dual-responsive drug release behaviors and multienzymatic activities, including Fenton, glutathione peroxidase-, and catalase-like activities. TCCHA, a redox homeostasis disruptor, promotes ⋅OH generation and GSH depletion, thus increasing the efficacy of chemodynamic therapy. TCCHA, which has catalase-like activity, can also reinforce the efficacy of photodynamic therapy by amplifying O2 production. In vivo, TCCHA efficiently inhibited tumor angiogenesis and suppressed tumor growth without apparent systemic toxicity. Overall, this study presents a facile strategy for the preparation of multienzyme-like nanoparticles, and TCCHA nanoparticles display great potential for enzyme catalysis-enhanced chemodynamic/photodynamic/antiangiogenic triple therapy against cancer.

Bioinspired Surface Ligand Engineering Regulates Electron Transfers in Gold Clusterzymes to Enhance the Catalytic Activity for Improving Sensing Performance

Metal nanoclusters feature a hierarchical structure, facilitating their ability to mimic enzyme-catalyzed reactions. However, the lack of true catalytic centers, compounded by tightly bound surface ligands hindering electron transfers to substrates, underscores the need for universal rational design methodologies to emulate the structure and mechanisms of natural enzymes. Motivated by the electron transfer in active centers with specific chemical structures, by integrating the peroxidase cofactor Fe-TCPP onto the surface of glutathione-stabilized gold nanoclusters (AuSG), we engineered AuSG-Fe-TCPP clusterzymes with a remarkable 39.6-fold enhancement in peroxidase-like activity compared to AuSG. Fe-TCPP not only mimics the active center structure, enhancing affinity to H2O2, but also facilitates the electron transfer process, enabling efficient H2O2 activation. By exemplifying the establishment of a detecting platform for trace H2O2 produced by ultrasonic cleaners, we substantiate that the bioinspired surface-ligand-engineered electron transfer can improve sensing performance with a wider linear range and lower detection limit.

CuCo2O4 Nanoflowers with Multiple Enzyme Activities for Treating Bacterium-Infected Wounds via Cuproptosis-like Death

Nanozyme-driven catalytic therapy provides a promising treatment strategy for bacterial biofilm-infected wounds. However, the single functionality and limited catalytic efficiency of nanozyme-based materials often restrict the effectiveness of wound infection treatment. In this study, CuCo2O4 nanoflowers with multiple enzymatic activities were prepared for antibacterial/antibiofilm treatment by cuproptosis-like death. CuCo2O4 exhibited peroxidase-like (POD-like) and oxidase-like (OXD-like) dual enzyme activities that generated large amounts of •OH and O2•-. Moreover, the glutathione peroxidase-like (GSH-Px-like) activity of CuCo2O4 was able to reduce the overexpression of GSH in the wound microenvironment, enhancing the therapeutic effects of reactive oxygen species (ROS). The morphology of CuCo2O4 was modified using a hydrothermal method with PEG4000 as the solvent, resulting in the exposure of more active center sites and a significant improvement in enzyme catalytic activity. The in vitro results demonstrated the pronounced disruption effect of CuCo2O4 on biofilms formed by bacteria. In vivo, CuCo2O4 significantly promoted angiogenesis, collagen deposition, and cell proliferation. Transcriptome sequencing revealed that elevated ROS levels in bacteria led to cell membrane damage and metabolic disruption. In addition, Cu2+ overload in bacteria induces lipid peroxidation accumulation and disrupts the respiratory chain and tricarboxylic acid (TCA) cycle, ultimately leading to bacterial cuproptosis-like death. This therapeutic strategy, which combines the synergistic effects of multiple enzyme-like activities with cuproptosis-like death, provides an approach for treating biofilm infections.

AI-Powered Knowledge Base Enables Transparent Prediction of Nanozyme Multiple Catalytic Activity

Nanozymes are unique materials with many valuable properties for applications in biomedicine, biosensing, environmental monitoring, and beyond. In this work, we developed a machine learning (ML) approach to search for new nanozymes and deployed a web platform, DiZyme, featuring a state-of-the-art database of nanozymes containing 1210 experimental samples, catalytic activity prediction, and DiZyme Assistant interface powered by a large language model (LLM). For the first time, we enable the prediction of multiple catalytic activities of nanozymes by training an ensemble learning algorithm achieving R2 = 0.75 for the Michaelis-Menten constant and R2 = 0.77 for the maximum velocity on unseen test data. We envision an accurate prediction of multiple catalytic activities (peroxidase, oxidase, and catalase) promoting novel applications for a wide range of surface-modified inorganic nanozymes. The DiZyme Assistant based on the ChatGPT model provides users with supporting information on experimental samples, such as synthesis procedures, measurement protocols, etc. DiZyme (dizyme.aicidlab.itmo.ru) is now openly available worldwide.

Self-assembled bifunctional nanoflower-enabled CRISPR/Cas biosensing platform for dual-readout detection of Salmonella enterica

Sensitive detection and point-of-care test of bacterial pathogens is of great significance in safeguarding the public health worldwide. Inspired by the characteristics of horseradish peroxidase (HRP), we synthesized a hybrid nanoflower with peroxidase-like activity via a three-component self-assembled strategy. Interestingly, the prepared nanozyme not only could act as an alternative to HRP for colorimetric biosensing, but also function as a unique signal probe that could be recognized by a pregnancy test strip. By combining the bifunctional properties of hybrid nanoflower, isothermal amplification of LAMP, and the specific recognition and non-specific cleavage properties of CRISPR/Cas12a system, the dual-readout CRISPR/Cas12a biosensor was developed for sensitive and rapid detection of Salmonella enterica. Moreover, this platform in the detection of Salmonella enterica had limits of detection of 1 cfu/mL (colorimetric assay) in the linear range of 101-108 cfu/mL and 102 cfu/mL (lateral flow assay) in the linear range of 102-108 cfu/mL, respectively. Furthermore, the developed biosensor exhibited good recoveries in the spiked samples (lake water and milk) with varying concentrations of Salmonella enterica. This work provides new insights for the design of multifunctional nanozyme and the development of innovative dual-readout CRISPR/Cas system-based biosensing platform for the detection of pathogens.

Sensitive dual-signal detection and effective removal of tetracycline antibiotics in honey based on a hollow triple-metal organic framework nanozymes

In this work, a colorimetric/fluorescent dual-signal mode sensor is proposed for the sensitive, selective and accurate detection and removal of tetracycline antibiotics (TCs). A triple-metal MOF of NiCoFe is successfully synthesized and controllable adjusted the shape of the hollow structure for the first time, and then modified with TCs aptamer. The as-prepared triple-atom MOF (apt-NiCoFe-MOF-74) exhibits well-defined hollow morphology, high crystallinity, and high surface areas endow their alluring adsorption and removal performances for TCs. More attractively, this triple-metal MOF show a good peroxidase-like activity and strong fluorescence property at 540 nm of apt-NiCoFe-MOF-74 when excitation wavelength was 370 nm. Inspire by this, a dual-signal output biosensor is constructed and the linear absorbance response is well correlated with wide range and low LOD for TCs. The biosensor provided an universal method with satisfactory sensitivity and accuracy for TCs analysis in real food samples.

Catalytic and biocatalytic degradation of microplastics

In recent years, there has been a surge in annual plastic production, which has contributed to growing environmental challenges, particularly in the form of microplastics. Effective management of plastic and microplastic waste has become a critical concern, necessitating innovative strategies to address its impact on ecosystems and human health. In this context, catalytic degradation of microplastics emerges as a pivotal approach that holds significant promise for mitigating the persistent effects of plastic pollution. In this article, we critically explored the current state of catalytic degradation of microplastics and discussed the definition of degradation, characterization methods for degradation products, and the criteria for standard sample preparation. Moreover, the significance and effectiveness of various catalytic entities, including enzymes, transition metal ions (for the Fenton reaction), nanozymes, and microorganisms are summarized. Finally, a few key issues and future perspectives regarding the catalytic degradation of microplastics are proposed.

Biomimetic Integrated Nanozyme for Flare and Recurrence of Gouty Arthritis

Flare and multiple recurrences pose significant challenges in gouty arthritis. Traditional treatments provide temporary relief from inflammation but fail to promptly alleviate patient pain or effectively prevent subsequent recurrences. It should also be noted that both anti-inflammation and metabolism of uric acid are necessary for gouty arthritis, calling for therapeutic systems to achieve these two goals simultaneously. In this study, we propose a biomimetic integrated nanozyme, HMPB-Pt@MM, comprising platinum nanozyme and hollow Prussian blue. It demonstrates anti-inflammatory properties by eliminating reactive oxygen species and reducing infiltration of inflammatory macrophages. Additionally, it rapidly targets inflamed ankles through the camouflage of macrophage membranes. Furthermore, HMPB-Pt@MM exhibits urate oxidase-like capabilities, continuously metabolizing locally elevated uric acid concentrations, ultimately inhibiting multiple recurrences of gouty arthritis. In summary, HMPB-Pt@MM integrates ROS clearance with uric acid metabolism, offering a promising platform for the treatment of gouty arthritis.

Probiotics Armed with In Situ Mineralized Nanocatalysts and Targeted Biocoatings for Multipronged Treatment of Inflammatory Bowel Disease

While oral probiotics show promise in treating inflammatory bowel disease, the primary challenge lies in sustaining their activity and retention within the inflamed gastrointestinal environment. In this work, we develop an engineered probiotic platform that is armed with biocatalytic and inflamed colon-targeting nanocoatings for multipronged management of IBD. Notably, we achieve the in situ growth of artificial nanocatalysts on probiotics through a bioinspired mineralization strategy. The resulting ferrihydrite nanostructures anchored on bacteria exhibit robust catalase-like activity across a broad pH range, effectively scavenging ROS to alleviate inflammation. The further envelopment with fucoidan-based shields confers probiotics with additional inflamed colon-targeting functions. Upon oral administration, the engineered probiotics display markedly improved viability and colonization within the inflamed intestine, and they further elicit boosted prophylactic and therapeutic efficacy against colitis through the synergistic interplay of nanocatalysis-based immunomodulation and probiotics-mediated microbiota reshaping. The robust and multifunctional probiotic platforms offer great potential for the comprehensive management of gastrointestinal disorders.

Transition-Metal-Based Nanozymes: Synthesis, Mechanisms of Therapeutic Action, and Applications in Cancer Treatment

Cancer, as one of the leading causes of death worldwide, drives the advancement of cutting-edge technologies for cancer treatment. Transition-metal-based nanozymes emerge as promising therapeutic nanodrugs that provide a reference for cancer therapy. In this review, we present recent breakthrough nanozymes for cancer treatment. First, we comprehensively outline the preparation strategies involved in creating transition-metal-based nanozymes, including hydrothermal method, solvothermal method, chemical reduction method, biomimetic mineralization method, and sol-gel method. Subsequently, we elucidate the catalytic mechanisms (catalase (CAT)-like activities), peroxidase (POD)-like activities), oxidase (OXD)-like activities) and superoxide dismutase (SOD)-like activities) of transition-metal-based nanozymes along with their activity regulation strategies such as morphology control, size manipulation, modulation, composition adjustment and surface modification under environmental stimulation. Furthermore, we elaborate on the diverse applications of transition-metal-based nanozymes in anticancer therapies encompassing radiotherapy (RT), chemodynamic therapy (CDT), photodynamic therapy (PDT), photothermal therapy (PTT), sonodynamic therapy (SDT), immunotherapy, and synergistic therapy. Finally, the challenges faced by transition-metal-based nanozymes are discussed alongside future research directions. The purpose of this review is to offer scientific guidance that will enhance the clinical applications of nanozymes based on transition metals.

Nanozymes for Treating Ocular Diseases

Nanozymes, characterized by their nanoscale size and enzyme-like catalytic activities, exhibit diverse therapeutic potentials, including anti-oxidative, anti-inflammatory, anti-microbial, and anti-angiogenic effects. These properties make them highly valuable in nanomedicine, particularly ocular therapy, bypassing the need for systemic delivery. Nanozymes show significant promise in tackling multi-factored ocular diseases, particularly those influenced by oxidation and inflammation, like dry eye disease, and age-related macular degeneration. Their small size, coupled with their ease of modification and integration into soft materials, facilitates the effective penetration of ocular barriers, thereby enabling targeted or prolonged therapy within the eye. This review is dedicated to exploring ocular diseases that are intricately linked to oxidation and inflammation, shedding light on the role of nanozymes in managing these conditions. Additionally, recent studies elucidating advanced applications of nanozymes in ocular therapeutics, along with their integration with soft materials for disease management, are discussed. Finally, this review outlines directions for future investigations aimed at bridging the gap between nanozyme research and clinical applications.

Preparation and Application of Carbon Dots Nanozymes

Carbon dot (CD) nanozymes have enzyme-like activity. Compared with natural enzymes, CD nanozymes offer several advantages, including simple preparation, easy preservation, good stability and recycling, which has made them a popular research topic in various fields. In recent years, researchers have prepared a variety of CD nanozymes for biosensing detection, medicine and tumor therapy, and many of them are based on oxidative stress regulation and reactive oxygen species clearance. Particularly to expand their potential applications, elemental doping has been utilized to enhance the catalytic capabilities and other properties of CD nanozymes. This review discusses the prevalent techniques utilized in the synthesis of CD nanozymes and presents the diverse applications of CD nanozymes based on their doping characteristics. Finally, the challenges encountered in the current utilization of CD nanozymes are presented. The latest research progress of synthesis, application and the challenges outlined in the review can help and encourage the researchers for the future research on preparation, application and other related researches of CD nanozymes.