Single-atom Nanozymes Research Articles

Green synthesis of iron-doped graphene quantum dots: an efficient nanozyme for glucose sensing.

Single-atom nanozymes with well-defined atomic structures and electronic coordination environments can effectively mimic the functions of natural enzymes. However, the costly and intricate preparation processes have hindered further exploration and application of these single-atom nanozymes. In this study, we presented a synthesis technique for creating Fe-N central single-atom doped graphene quantum dot (FeN/GQDs) nanozymes using a one-step solvothermal process, where individual iron atoms form strong bonds with graphene quantum dots through nitrogen coordination. Unlike previous studies, this method significantly simplifies the synthesis conditions for single-atom nanozymes, eliminating the need for high temperatures and employing environmentally friendly precursors derived from pineapple (ananas comosus) leaves. The resulting FeN/GQDs exhibited peroxidase-like catalytic activity and kinetics comparable to that of natural enzymes, efficiently converting H2O2 into hydroxyl radical species. Leveraging their excellent peroxide-like activity, FeN/GQDs nanozymes have been successfully applied to construct a colorimetric biosensor system characterized by remarkably high sensitivity for glucose detection. This achievement demonstrated a promising approach to designing single-atom nanozymes with both facile synthesis procedures and high catalytic activity, offering potential applications in wearable sensors and personalized health monitoring.

Antioxidant activities of metal single-atom nanozymes in biomedicine.

Nanozymes are a class of nanomaterials with enzyme-like activity that can mimic the catalytic properties of natural enzymes. The small size, high catalytic activity, and strong stability of nanozymes compared to those of natural enzymes allow them to not only exist in a wide temperature and pH range but also maintain stability in complex environments. Recently developed single-atom nanozymes have metal active sites composed of a single metal atom fixed to a carrier. These metal atoms can act as independent catalytically active centers. Metal single-atom nanozymes have a homogeneous single-atom structure and a suitable coordination environment for stronger catalytic activity and specificity than traditional nanozymes. The antioxidant metal single-atom nanozymes with the ability of removing reactive oxygen species (ROS) can simulate superoxidase dismutase, catalase, and glutathione peroxidase to show different effects in vivo. Furthermore, due to the similar structure of antioxidant enzymes, a metal single-atom nanozyme often has multiple antioxidant activities, and this synergistic effect can more efficiently remove ROS related to oxidative stress. The versatility of single-atom nanozymes encompasses a broad spectrum of biomedical applications such as anti-oxidation, anti-infection, immunomodulatory, biosensing, bioimaging, and tumor therapy applications. Herein, the nervous, circulatory, digestive, motor, immune, and sensory systems are considered in order to demonstrate the role of metal single-atom nanozymes in biomedical antioxidants.

Atomically dispersed single-atom catalysts (SACs) and enzymes (SAzymes): synthesis and application in Alzheimer's disease detection.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline and memory loss. Conventional diagnostic methods, such as neuroimaging and cerebrospinal fluid analysis, typically detect AD at advanced stages, limiting the efficacy of therapeutic interventions. Early detection is crucial for improving patient condition by enabling timely administration of treatments that may decelerate disease progression. In this context, single-atom catalysts (SACs) and single-atom nanozymes (SAzymes) have emerged as promising tools offering highly sensitive and selective detection of Alzheimer's biomarkers. SACs, consisting of isolated metal atoms on a support surface, deliver unparalleled atomic efficiency, increased reactivity, and reduced operational costs, although certain challenges in terms of stability, aggregation, and other factors persist. The advent of SAzymes, which integrate SACs with natural metalloprotease catalysts, has further advanced this field by enabling controlled electronic exchange, synergistic productivity, and enhanced biosafety. Particularly, M-N-C SACs with M-Nx active sites mimic the selectivity and sensitivity of natural metalloenzymes, providing a robust platform for early detection of AD. This review encompasses the advancements in SACs and SAzymes, highlighting their pivotal role in bridging the gap between conventional enzymes and nanozyme and offering enhanced catalytic efficiency, controlled electron transfer, and improved biosafety for Alzheimer's detection.

Single atom nanozymes for bacterial infection therapy.

Bacterial infection-related diseases continue to pose a significant challenge to global human health. Antibiotic therapy, as a conventional therapeutic strategy, has been extensively employed in clinical settings to treat bacterial infections. However, the effectiveness of these conventional strategies is often impeded by the antimicrobial resistance of bacteria. Consequently, the development of alternative antibacterial agents has emerged as a promising approach to addressing this issue. In recent years, single-atom nanozymes (SAzymes), a novel class of nanocatalytic medicines, have garnered increasing attention due to their numerous advantages, including uniformly dispersed metal active sites, tunable coordination structures, and maximal metal atomic utilization efficiency. To date, a variety of SAzymes have been developed and widely applied in antibacterial therapy. In this minireview, we provide an overview of the latest advances in the synthesis and antibacterial application of different metal-based SAzymes. Furthermore, we discuss the future challenges and opportunities of utilizing SAzymes for bacterial infection treatment. It is our hope that this minireview will contribute to the development of the next generation of SAzyme-based antibacterial agents.

Theory-guided design of S-doped Fe/Co dual-atom nanozymes for highly efficient oxidase mimics.

The advent of dual-atom nanozymes (DAzymes) featuring distinctive bimetallic active sites garnered significant attention, representing enhanced iterations of conventional single-atom nanozymes. The quest for an effective and universal strategy to modulate the catalytic activity of DAzymes posed a formidable challenge, yet few published reports addressed this. Herein, we designed and synthesized S-doped Fe/Co DAzymes (S-FeCo-NC) under theoretical guidance and revealed their excellent oxidase-like activity. Experimental and theoretical calculations indicated that the superior oxidase-like activity exhibited by S-FeCo-NC was attributed to the S-doping, which modulated the local electronic structure of the dual-atom active site. This modulation of the local electronic structure significantly optimizes oxygen adsorption energy, thereby accelerating the rate of enzyme-catalyzed reactions. As a proof-of-concept, this study integrated S-FeCo-NC with the cascade inhibition reaction of acetylcholinesterase (AChE) to devise a sensitive analytical platform for detecting organophosphorus pesticides. This study paved the way for elucidating the correlation between the local electronic structure of the active site and enzyme activity, offering novel methodologies and insights for the rational design of DAzymes.

Engineering Atomically Dispersed Cu-N1S2 Sites via Chemical Vapor Deposition to Boost Enzyme-Like Activity for Efficient Tumor Therapy.

Single-atom nanozymes (SAzymes), with well-defined and uniform atomic structures, are an emerging type of natural enzyme mimics. Currently, it is important but challenging to rationally design high-performance SAzymes and deeply reveal the interaction mechanism between SAzymes and substrate molecules. Herein, this work reports the controllable fabrication of a unique Cu-N1S2-centred SAzyme (Cu-N/S-C) via a chemical vapor deposition-based sulfur-engineering strategy. Benefiting from the optimized geometric and electronic structures of single-atom sites, Cu-N/S-C SAzyme shows boosted enzyme-like activity, especially in catalase-like activity, with a 13.8-fold increase in the affinity to hydrogen peroxide (H2O2) substrate and a 65.2-fold increase in the catalytic efficiency when compared to Cu-N-C SAzyme with Cu-N3 sites. Further theoretical studies reveal that the increased electron density around single-atom Cu is achieved through electron redistribution, and the efficient charge transfer between Cu-N/S-C and H2O2 is demonstrated to be more beneficial for the adsorption and activation of H2O2. The as-designed Cu-N/S-C SAzyme possesses an excellent antitumor effect through the synergy of catalytic therapy and oxygen-dependent phototherapy. This study provides a strategy for the rational design of SAzymes, and the proposed electron redistribution and charge transfer mechanism will help to understand the coordination environment effect of single-atom metal sites on H2O2-mediated enzyme-like catalytic processes.

A Pt1Pd Single-Atom Alloy Nanozyme with Boosted Enzyme-Like Activity for Efficient Photo-Mediated Tumor Therapy.

Single-atom nanozymes (SAzymes) are emerging natural enzyme mimics and have attracted much attention in the biomedical field. SAzymes with Metal─Nx sites designed on carbon matrixes are currently the mainstream in research. It is of great significance to further expand the types of SAzymes to enrich the nanozyme library. Single-atom alloys (SAAs) are a material in which single-atom metal sites are dispersed onto another active metal matrix, and currently, there is limited research on their enzyme-like catalytic performance. In this work, a biodegradable Pt1Pd SAA is fabricated via a simple galvanic replacement strategy, and for the first time reveals its intrinsic enzyme-like catalytic performance including catalase-, oxidase-, and peroxidase-like activities, as well as its photodynamic effect. Experimental characterizations demonstrate that the introduction of single-atom Pt sites contributes to enhancing the affinity of Pt1Pd single-atom alloy nanozyme (SAAzyme) toward substrates, thus exhibiting boosted catalytic efficiency. In vitro and in vivo experiments demonstrate that Pt1Pd SAAzyme exhibits a photo-controlled therapeutic effect, with a tumor inhibition rate of up to 100%. This work provides vital guidance for opening the research direction of SAAs in enzyme-like catalysis.

Developing Single-Atomic Manganese Nanozymes for Synergistic Mild Photothermal/Multienzymatic Therapy.

Synergistic mild photothermal/nanozyme therapy with outstanding hyperthermia performance and excellent multienzyme properties is highly needed for osteosarcoma treatment. Herein, we have developed efficient single-atom nanozymes (SANs) consisting of Mn sites atomically dispersed on nitrogen-doped carbon nanosheets (denoted as Mn-SANs) for synergistic mild photothermal/multienzymatic therapy against osteosarcoma. Benefiting from their black N-doped carbon nanosheet matrices, Mn-SANs showed an excellent NIR-II-triggered photothermal effect. On the other hand, Mn-SANs with atomically dispersed Mn sites have outstanding multienzyme activities. Mn-SANs can catalyze endogenous H2O2 in osteosarcoma into O2 by catalase (CAT)-like activity, which can effectively ease osteosarcoma hypoxia and trigger the oxidase (OXD)-like catalysis that converts O2 to the cytotoxic superoxide anion radical (•O2-). At the same time, Mn-SANs can also mimic glutathione oxidase (GSHOx) to effectively consume the antioxidant glutathione (GSH) in osteosarcoma and inhibit intracellular glutathione peroxidase 4 (GPX4) expression. Such intratumoral •O2- production, GSH depletion, and GPX4 inactivation mediated by Mn-SANs can create a large accumulation of lipid peroxides (LPO) and •O2-, leading to oxidative stress and disrupting the redox homeostasis in osteosarcoma cells, which can ultimately induce osteosarcoma cell death. More importantly, heat shock proteins (HSPs) can be significantly destroyed via Mn-SAN-mediated plentiful LPO and •O2- generation, thus effectively impairing osteosarcoma cells resistant to mild photothermal therapy. Overall, through the cooperative effect of chemical processes (boosting •O2-, consuming GSH, and enhancing LPO) and biological processes (inactivating GPX4 and hindering HSPs), collaborative mild photothermal/multienzymatic therapy mediated by Mn-SANs is a promising strategy for efficient osteosarcoma treatment.

A smartphone-integrated colorimetric sensor for sensitive detection of organophosphorus pesticides based on large-scale synthesized Fe-N/C single-atom nanozymes

Single-atom nanozymes (SAzymes) have been wildly used to design high-performance biosensors for the quantification of organophosphorus pesticides (OPs) recently. However, the low yield and low metal loading of SAzymes often limit their practical use in biosensing field. Herein, a large-scale synthesis (6.60 g) of Fe-N /C SAzymes (Fe loading of 3.9 wt%) was achieved by using carbon black as a template. This prepared Fe-N/C SAzymes exhibit efficient oxidase-like activity that could catalyze the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) along with color variation. On this basis of Fe-N/C SAzymes, a colorimetric biosensor was designed for OPs detection. Then a smartphone combined with RGB analysis was used to digitize the color information. The B/ (R + G) value shows good linear detection range (1–100 nM) and low detection limit (0.4177 nM). More importantly, the large-scale synthetic approach and excellent catalytic performance of Fe-N/C SAzymes are significant for promoting the marketability of biosensors.

Employing Noble Metal-Porphyrins to Engineer Robust and Highly Active Single-Atom Nanozymes for Targeted Catalytic Therapy in Nasopharyngeal Carcinoma.

Single-atom nanozymes (SANzymes) emerge as promising alternatives to conventional enzymes. However, chemical instability limits their application. Here, a systematic synthesis of highly active and stable SANzymes is presented by leveraging noble metal-porphyrins. Four noble metal-porphyrins are successfully synthesized to mimic the active site of natural peroxidases through atomic metal-N coordination anchored to the porphyrin center. These noble metal-porphyrins are integrated into a stable and biocompatible Zr-based metal-organic framework (MxP, x denoting Ir, Ru, Pt, and Pd). Among these, MIrP demonstrates superior peroxidase-like activity (685.61 U mg-1 ), catalytic efficiency, and selectivity compared to horseradish peroxidase (267.71 U mg-1 ). Mechanistic investigations unveil heightened catalytic activity of MIrP arises from its robust H2 O2 adsorption capacity, unique rate-determining step, and low energy threshold. Crucially, MIrP exhibits remarkable chemical stability under both room temperature and high H2 O2 concentrations. Further, through modification with (-)-Epigallocatechin-3-Gallate, a natural ligand for Epstein-Barr virus (EBV)-encoded latent membrane protein 1, targeted SANzyme (MIrPHE) tailored for EBV-associated nasopharyngeal carcinoma is engineered. This study not only presents an innovative strategy for augmenting the catalytic activity and chemical stability of SANzymes but also highlights the substantial potential of MIrP as a potent nanomedicine for targeted catalytic tumor therapy.

An Erythrocyte-Templated Iron Single-Atom Nanozyme for Wound Healing.

Iron single-atom nanozymes represent a promising artificial enzyme with superior activity owing to uniform active sites that can precisely mimic active center of nature enzymes. However, current synthetic strategies are hard to guarantee each active site at single-atom state. In this work, an erythrocyte-templated strategy by utilizing intrinsic hemin active center of hemoglobin as sing-atom source for nanozyme formation is developed. By combining cell fixation, porous salinization, and high-temperature carbonization, erythrocytes are successfully served as uniform templates to synthesize nanozymes with fully single-atom FeN4 active sites which derived from hemin of hemoglobin, resulting in an enhanced peroxidase (POD)-like activity. Interestingly, the catalytic activity of erythrocyte-templated nanozyme (ETN) shows dependence on animal species, among which murine ETN performed superior catalytic efficiency. In addition, the as-prepared ETNs display a honeycomb-like network structure, serving as a sponge to accelerate hemostasis based on the interactions with prothrombin and fibrinogen. These features enable ETN to effectively kill methicillin-resistant Staphylococcus aureus (MRSA) by combining POD-like catalysis with near-infrared (NIR) induced photothermal effect, and subsequently suitable to promote wound healing. This study provides a proof-of-concept for facile fabrication of multifunctional nanozymes with uniform single-atom active sites by utilizing intrinsic iron structure characteristics of biogenic source like erythrocytes.

Embedding Atomically Dispersed Manganese/Gadolinium Dual Sites in Oxygen Vacancy-Enriched Biodegradable Bimetallic Silicate Nanoplatform for Potentiating Catalytic Therapy.

Due to their atomically dispersed active centers, single-atom nanozymes (SAzymes) have unparalleled advantages in cancer catalytic therapy. Here, loaded with chlorin e6 (Ce6), a hydrothermally mass-produced bimetallic silicate-based nanoplatforms with atomically dispersed manganese/gadolinium (Mn/Gd) dual sites and oxygen vacancies (OVs) (PMnSA GMSNs-V@Ce6) is constructed for tumor glutathione (GSH)-triggered chemodynamic therapy (CDT) and O2 -alleviated photodynamic therapy. The band gaps of silica are significantly reduced from 2.78 to 1.88eV by doping with metal ions, which enables it to be excited by a 650nm laser to produce electron-hole pairs, thereby facilitating the generation of reactive oxygen species. The Gd sites can modulate the local electrons of the atom-catalyzed Mn sites, which contribute to the generation of superoxide and hydroxyl radicals (• OH). Tumor GSH-triggered Mn2+ release can convert endogenous H2 O2 to • OH and realize GSH-depletion-enhanced CDT. Significantly, the hydrothermally generated OVs can not only capture Mn and Gd atoms to form atomic sites but also can elongate and weaken the O-O bonds of H2 O2 , thereby improving the efficacy of Fenton reactions. The degraded Mn2+ /Gd3+ ions can be used as tumor-specific magnetic resonance imaging contrast agents. All the experimental results demonstrate the great potential of PMnSA GMSNs-V@Ce6 as cancer theranostic agent.

Fe-N-C single-atom nanozyme-linked immunosorbent assay for quantitative detection of aflatoxin B1

Aflatoxin B1 (AFB1) is a prominent food contaminant known for its high toxicity. Rapid, low-cost, and sensitive detection of AFB1 is an urgent demand for food safety risk control. In the traditional enzyme-linked immunosorbent assay (ELISA) method for AFB1 detection, horseradish peroxide (HRP) is high-cost and possesses poor environmental stability. In this study, a direct competitive single-atom nanozymes (SAzymes) -linked immunosorbent assay was developed based on Fe-N-C SAzymes. The proposed methods exhibited excellent sensitivity, rapid detection, fabrication, and low cost. Under the optimal conditions, the limit of detection of the new assay was 3.3 pg mL−1, with a quantitative relationship between 0.0084 and 0.358 ng mL−1. In addition, the developed method presented good recoveries in spiked samples, ranging from 84.50% and 103.75%, with coefficients of variation below 10%. Furthermore, the developed detection method showed good consistency (R2 = 0.9852) with the reference method, liquid chromatography/mass spectrometry (LC-MS/MS). To our knowledge, this is the first report about single-atom nanozymes-based ELISA for AFB1 determination. This work provides a feasible strategy for the rapid and sensitive detection of food contaminants using SAzymes.

Oxidative Stress in Health and Disease.

Oxidative stress, resulting from the excessive intracellular accumulation of reactive oxygen species (ROS), reactive nitrogen species (RNS), and other free radical species, contributes to the onset and progression of various diseases, including diabetes, obesity, diabetic nephropathy, diabetic neuropathy, and neurological diseases, such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Oxidative stress is also implicated in cardiovascular disease and cancer. Exacerbated oxidative stress leads to the accelerated formation of advanced glycation end products (AGEs), a complex mixture of crosslinked proteins and protein modifications. Relatively high levels of AGEs are generated in diabetes, obesity, AD, and other I neurological diseases. AGEs such as Ne-carboxymethyllysine (CML) serve as markers for disease progression. AGEs, through interaction with receptors for advanced glycation end products (RAGE), initiate a cascade of deleterious signaling events to form inflammatory cytokines, and thereby further exacerbate oxidative stress in a vicious cycle. AGE inhibitors, AGE breakers, and RAGE inhibitors are therefore potential therapeutic agents for multiple diseases, including diabetes and AD. The complexity of the AGEs and the lack of well-established mechanisms for AGE formation are largely responsible for the lack of effective therapeutics targeting oxidative stress and AGE-related diseases. This review addresses the role of oxidative stress in the pathogenesis of AGE-related chronic diseases, including diabetes and neurological disorders, and recent progress in the development of therapeutics based on antioxidants, AGE breakers and RAGE inhibitors. Furthermore, this review outlines therapeutic strategies based on single-atom nanozymes that attenuate oxidative stress through the sequestering of reactive oxygen species (ROS) and reactive nitrogen species (RNS).

Current Advances of Atomically Dispersed Metal-Centered Nanozymes for Tumor Diagnosis and Therapy.

Nanozymes, which combine enzyme-like catalytic activity and the biological properties of nanomaterials, have been widely used in biomedical fields. Single-atom nanozymes (SANs) with atomically dispersed metal centers exhibit excellent biological catalytic activity due to the maximization of atomic utilization efficiency, unique metal coordination structures, and metal-support interaction, and their structure-activity relationship can also be clearly investigated. Therefore, they have become an emerging alternative to natural enzymes. This review summarizes the examples of nanocatalytic therapy based on SANs in tumor diagnosis and treatment in recent years, providing an overview of material classification, activity modulation, and therapeutic means. Next, we will delve into the therapeutic mechanism of SNAs in the tumor microenvironment and the advantages of synergistic multiple therapeutic modalities (e.g., chemodynamic therapy, sonodynamic therapy, photothermal therapy, chemotherapy, photodynamic therapy, sonothermal therapy, and gas therapy). Finally, this review proposes the main challenges and prospects for the future development of SANs in cancer diagnosis and therapy.

Ultrasensitive electrochemical sensing of catechol and hydroquinone via single-atom nanozyme anchored on MOF-derived porous carbon

Single-atom nanozymes (SANs) can significantly enhance the sensitivity and selectivity of electrochemical sensing platforms due to the homogeneity of their active sites, full atom utilization, and high catalytic activity. In this study, we demonstrate the synthesis and characterization of a high-density Co-based single-atom nanozyme anchored on activated MOF-derived porous carbon (Co-AcNC-3) via a cascade anchoring strategy for ultrasensitive, simultaneous electrochemical detection of catechol (CC) and hydroquinone (HQ). The Co-AcNC-3 displays a large specific surface area, high defectivity, and abundant oxygen-containing groups, with Co atoms being atomically dispersed throughout the carbon support via Co–N bonds. The Co-AcNC-3 biosensor exhibits superior electrochemical signals for CC and HQ, with linear ranges of 4.0 μM–300.0 μM. and detection limits of 0.072 μM and 0.034 μM, respectively. Moreover, the Co-AcNC-3 biosensor has shown excellent performance in accurately detecting CC and HQ in actual samples. Our findings highlight the potential of the proposed Co-AcNC-3 biosensor as a reliable and promising sensing platform for determining CC and HQ.

Fe-NC nanozymes-loaded TiO2 nanotube arrays endow titanium implants with excellent antioxidant capacity for inflammation inhibition and soft tissue integration

Titanium (Ti) and its alloys have been widely used as percutaneous and subcutaneous implants due to their excellent mechanical properties and biocompatibility. However, the aggregation of reactive oxygen species (ROS) and persistent inflammatory responses at the implant site severely affect the soft tissue integration of Ti implants, causing a series of biological complications. To address this issue, in this study, Fe-nitrogen-doped carbon single-atom nanozymes (Fe-NC nanozymes) loaded titanium oxide nanotube arrays (Fe-NC@TNT) were constructed by anodic oxidation and solvothermal method on medical titanium surfaces. The surface morphology, physical composition, enzyme-like catalytic activity, inflammatory response, and soft tissue compatibility of Fe-NC@TNT were investigated. The unique nanotube array fully exposes the catalytic active sites of Fe-NC nanozymes and significantly enhances their enzyme-like catalytic performance to eliminate superoxide anion, hydrogen peroxide, and more toxic hydroxyl radicals, which could effectively reduce the intracellular ROS levels of macrophages and fibroblasts, thereby inhibiting the inflammatory responses of macrophages and promoting the functional expression of fibroblasts. In vivo animal experiments have further demonstrated that Fe-NC@TNT can effectively regulate the immune response and promote the integration between the implant and the surrounding soft tissues.

Spatial Position Regulation of Cu Single Atom Site Realizes Efficient Nanozyme Photocatalytic Bactericidal Activity.

Recently, single-atom nanozymes have made significant progress in the fields of sterilization and treatment, but their catalytic performance as substitutes for natural enzymes and drugs is far from satisfactory. Here, a method is reported to improve enzyme activity by adjusting the spatial position of a single-atom site on the nanoplatforms. Two types of Cu single-atom site nanozymes are synthesized in the interlayer (CuL /PHI) and in-plane (CuP /PHI) of poly (heptazine imide) (PHI) through different synthesis pathways. Experimental and theoretical analysis indicates that the interlayer position of PHI can effectively adjust the coordination number, coordination bond length, and electronic structure of Cu single atoms compared to the in-plane position, thereby promoting photoinduced electron migration and O2 activation, enabling effective generate reactive oxygen species (ROS). Under visible light irradiation, the photocatalytic bactericidal activity of CuL /PHI against aureus is ≈100%, achieving the same antibacterial effect as antibiotics, after 10min of low-dose light exposure and 2h of incubation.

Burgeoning Single-Atom Nanozymes for Efficient Bacterial Elimination.

To fight against antibacterial-resistant bacteria-induced infections, the development of highly efficient antibacterial agents with a low risk of inducing resistance is exceedingly urgent. Nanozymes can rapidly kill bacteria with high efficiency by generating reactive oxygen species via enzyme-mimetic catalytic reactions, making them promising alternatives to antibiotics for antibacterial applications. However, insufficient catalytic activity greatly limits the development of nanozymes to eliminate bacterial infection. By increasing atom utilization to the maximum, single-atom nanozymes (SAzymes) with an atomical dispersion of active metal sites manifest superior enzyme-like activities and have achieved great results in antibacterial applications in recent years. In this review, the latest advances in antibacterial SAzymes are summarized, with specific attention to the action mechanism involved in antibacterial applications covering wound disinfection, osteomyelitis treatment, and marine antibiofouling. The remaining challenges and further perspectives of SAzymes for practical antibacterial applications are also discussed.

Modulating the Coordination Environment of Carbon-Dot-Supported Fe Single-Atom Nanozymes for Enhanced Tumor Therapy.

Herein, carbon dot (CD)-supported Fe single-atom nanozymes with high content of pyrrolic N and ultrasmall size (ph-CDs-Fe SAzyme) are fabricated by a phenanthroline-mediated ligand-assisted strategy. Compared with phenanthroline-free nanozymes (CDs-Fe SAzyme), ph-CDs-Fe SAzyme exhibit higher peroxidase (POD)-like activity due to their structure similar to that of ferriporphyrin in natural POD. Aberration-corrected high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure spectroscopy (XAFS) analyses show that metal Fe is dispersed in ph-CDs-Fe SAzyme as single atoms. Steady-state kinetic studies show that the maximum velocity (Vmax ) and turnover number (kcat ) of H2 O2 homolyticcleavage catalyzed by ph-CDs-Fe SAzyme are 3.0 and 6.2 more than those of the reaction catalyzed by CDs-Fe SAzyme. Density functional theory (DFT) calculations show that the energy barrier of the reaction catalyzed by ph-CDs-Fe SAzyme is lower than that catalyzed by CDs-Fe SAzyme. Antitumor efficacy experiments show that ph-CDs-Fe SAzyme can efficiently inhibit the growth of tumor cells both in vitro and in vivo by synergistic chemodynamic and photothermal effects. Here a new paradigm is provided for the development of efficient antitumor therapeutic approaches based on SAzyme with POD-like activity.