An emerging direction for nanozyme design: from single-atom to dual-atomic-site catalysts

Dual-atom nanozymes: Synthesis, characterization, catalytic mechanism and biomedical applications

Dual-atom nanozymes (DAzymes), a novel class of nanozymes featuring dual-metal atomic active centers, mimic the multi-metal synergistic mechanisms of natural enzymes to achieve superior catalytic activity compared to conventional single-atom nanozymes. Their unique dual-atom architecture not only effectively mitigates metal atom aggregation but also significantly enhances substrate adsorption capacity and catalytic efficiency through interatomic electronic coupling and spatial synergy. This structural innovation addresses critical limitations of single-atom nanozymes, including low metal loading and homogeneous active sites. This review systematically summarizes recent advancements in DAzymes: First, we elucidate their design principles and structural advantages, with a focus on precise synthesis strategies (e.g., spatial confinement, coordination stabilization) and atomic-level characterization techniques (e.g., synchrotron radiation-based X-ray absorption spectroscopy, spherical aberration-corrected electron microscopy). By unraveling structure-activity relationships, we clarify the multi-dimensional regulatory mechanisms of dual-atom systems-including coordination environments, electronic coupling, and spatial configurations-on redox enzyme-like activities such as peroxidase and superoxide dismutase mimics. Furthermore, we elaborate on their groundbreaking biomedical applications, including antibacterial and antitumor therapies via reactive oxygen species (ROS) regulation, antioxidant damage repair, and biosensing. This review aims to provide theoretical guidance for the rational design of high-performance DAzymes and to advance their translational applications in precision medicine and intelligent biomaterials.

Tuning Atomically Dispersed Metal Sites in Nanozymes for Sensing Applications

Nanozymes with atomically dispersed metal sites (ADzymes), especially single-atom nanozymes, have attracted widespread attention in recent years due to their unique advantages in mimicking the active sites of natural enzymes. These nanozymes not only maximize exposure of catalytic sites but also possess superior catalytic activity performance, achieving challenging catalytic reactions. These advantages position ADzymes as highly promising candidates in the field of sensing and biosensing. This review summarizes the classification and properties of ADzymes, systematically highlighting some typical regulation strategies involving central metal, coordination environment, etc., to achieve their catalytical activity, specificity, and multifunctionality. Then, we present the recent advances of ADzymes in different sensing fields, including colorimetry, fluorescence, electrochemistry, chemiluminescence, photoelectrochemistry, and electrochemiluminescence. Taking advantage of their unique catalytic performance, the resultant ADzymes show great potential in achieving the goal of sensitivity, selectivity and accuracy for the detection of various targets. Specifically, the underlying mechanisms in terms of signal amplification were discussed in detail. Finally, the current challenges and perspectives on the development of advanced ADzymes are discussed.

The effect of photodynamic therapy using gentamicin and imipenem-derived carbon dots on Pseudomonas aeruginosa isolates

The increasing prevalence of antibiotic resistance poses a significant threat to the ability of healthcare systems to manage Pseudomonas aeruginosa infections, highlighting the need for innovative therapeutic strategies. The aim of this study was to evaluate the effects of photodynamic therapy (PDT) using carbon dots (CDs) derived from gentamicin and imipenem against P. aeruginosa isolates. A hydrothermal method was used to synthesise amine-functionalised CDs (CDsGEN-NH2, CDsIMP-NH2) from gentamicin and imipenem precursors, respectively. Conjugation of imipenem to CDsGEN-NH2 (CDsGEN-IMP) and gentamicin to CDsIMP-NH2 (CDsIMP-GEN) was achieved using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The synthesised CDs were analysed by HRTEM, zeta potential, UV-Vis, FTIR and fluorescence. The efficacy of photodynamic therapy (PDT) against P. aeruginosa ATCC27853 and two clinical P. aeruginosa isolates was evaluated using a combination of sub-minimum inhibitory concentrations (sub-MIC) and sub-lethal doses of UVA light (sDL) irradiation. The nanoscale size, electrical charge and photophysical properties of the synthesised CDs were confirmed by HRTEM, zeta potential, UV-Vis, FTIR and fluorescence techniques. Treatment with CDsGEN-NH2, CDsIMP-NH2 and CDsGEN-IMP at concentrations of 3 mg/mL (sub-MIC) and sDL irradiation for 10 s (3.12 J/cm2) resulted in significantly reduced viability in P. aeruginosa ATCC27853 compared to the control (P ≤ 0.05), achieving viable cell reductions of 3.44, 3.11 and 2.65 log, respectively. Treatment with CDsIMP-GEN at a concentration of 125 µg/mL (sub-MIC) and sDL irradiation for 10 s (3.12 J/cm2) also significantly reduced viability in P. aeruginosa ATCC27853 compared to the control (P ≤ 0.05), achieving a viable cell reduction of 3.75 log. These results demonstrate that CDs derived from imipenem and gentamicin can serve as effective antimicrobial agents in combination with UVA light irradiation for antimicrobial photodynamic therapy.

Construction of a CuO2@PDA Nanozyme with Switchable Dual Enzyme-Mimic Activities for Colorimetric Sensing of Catechol and Hydroquinone

The development of metal-based redox nanozymes represents a new frontier in pollutant sensing. In this field, designing highly active nanozymes and precisely regulating their enzymatic activity are key challenges. In this work, we report the construction of a copper peroxide@polydopamine (CuO2@PDA) nanozyme with dual enzyme-like activity, mimicking the active centers of laccase and peroxidase. Here, CuO2 acts as the catalytic center, while PDA serves as a carrier to prevent CuO2 aggregation and promotes conversion of CuII/CuI active sites via the reduction effect of its surface catechol groups to complete the catalytic cycle. As expected, the obtained CuO2@PDA nanozyme exhibits significant laccase- and peroxidase-mimetic activities. Moreover, its dual enzymatic activity can be systematically switched by adjusting pH and temperature. Specifically, laccase activity dominates near neutral pH, while CuO2 decomposition into Cu ions and H2O2 at acidic pH triggers peroxidase activity. Similarly, CuO2@PDA exhibits temperature-dependent dual enzymatic activity with peroxidase activity prevailing at low temperatures and laccase activity at high temperatures. According to enzymatic performance and XPS results, a possible catalytic mechanism of the dual enzymatic activity of CuO2@PDA has been proposed. Then, based on the pH-dependent dual enzymatic activity of CuO2@PDA, we constructed a detection system for the isomers of organic pollutants, catechol (CC) and hydroquinone (HQ). The laccase-like activity of CuO2@PDA enables direct oxidation of CC into yellow o-benzoquinone, while HQ discolors the preoxidized substrate generated via the peroxidase-like activity of CuO2@PDA. Moreover, selective sensing for CC and HQ with high sensitivity was achieved in real water samples. This approach can guide the design of nanozymes with multienzymatic activity and unveil their potential uses in environmental pollutant discrimination.

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.

New horizons for the therapeutic application of nanozymes in cancer treatment

The advent of nanozymes has revolutionized approaches to cancer diagnosis and therapy, introducing innovative strategies that address the limitations of conventional treatments. Nanozyme nanostructures with enzyme-mimicking catalytic abilities exhibit exceptional stability, biocompatibility, and customizable functions, positioning them as promising tools for cancer theranostics. By emulating natural enzyme reactions, nanozymes can selectively target and eradicate cancer cells, minimizing harm to adjacent healthy tissues. Nanozymes can also be functionalized with specific targeting ligands, allowing for the precise delivery and regulated release of therapeutic agents, improving treatment effectiveness and reducing adverse effects. However, issues such as biocompatibility, selectivity, and regulatory compliance remain critical challenges for the clinical application of nanozymes. This review provides an overview of nanozymes, highlighting their unique properties, various classifications, catalytic activities, and diverse applications in cancer treatments. The strategic oncological deployment of nanozymes could profoundly impact future advancements in personalized medicine, highlighting recent progress and prospective directions in enzyme-mimetic approaches for cancer treatment. This review summarizes an overview of nanozymes, highlighting their unique properties, various classifications, catalytic activities, and diverse applications in cancer treatments.

Construction of bimetallic oxy-hydroxides based on Ni(OH)2 nanosheets for sensitive non-enzymatic glucose detection via electrochemical oxidation and incorporation

Due to their ease of synthesis and large specific surface area, Ni(OH)2 nanosheets have emerged as promising electrochemical sensing materials, attracting significant attention in recent years. Herein, a series of oxy-hydroxides based on Ni(OH)2 nanosheets, including NiOx/Ni(OH)2@NF and (MNi)Ox/Ni(OH)2@NF (M = Co, Fe, or Cr), are successfully synthesized via the electrochemical oxidation and incorporation strategies. Electrochemical tests demonstrate that these Ni(OH)2-based oxy-hydroxides exhibit excellent electrochemical oxidation activity for glucose in alkaline electrolyte. Among these, (CoNi)Ox/Ni(OH)2@NF displays higher sensitivity of 3590.3 μA mM-1 cm-2 across a broad linear range of 10 μM to 1.14 mM, with a rapid current response time of less than 4 s. The superior sensing performances of (CoNi)Ox/Ni(OH)2@NF are attributed to the formation of abundant Ni3+ species and reactive-O atoms due to the electrochemical oxidation, and the synergistic effects of Co/Ni active sites resulting from the electrochemical incorporation process. In addition, the (CoNi)Ox/Ni(OH)2@NF demonstrates good stability and reproducibility for glucose sensing. This work fully leverages the significance of surface reconstruction of Ni(OH)2, providing new insights for the application of transition metal-based oxy-hydroxide materials in bio-sensing.

Advances and Future Trends in Nanozyme-Based SERS Sensors for Food Safety, Environmental and Biomedical Applications

Nanozymes, a kind of nanoparticles with enzyme-mimicking activities, have attracted considerable attention due to their robust catalytic properties, ease of preparation, and resistance to harsh conditions. By combining nanozymes with surface-enhanced Raman spectroscopy (SERS) technology, highly sensitive and selective sensors have been developed. These sensors are capable of detecting a wide range of analytes, such as foodborne toxins, environmental pollutants, and biomedical markers. This review provides an overview of recent advancements in the synthesis and surface modification of nanozymes, highlighting their ability to mimic multiple enzymes and enhance catalytic performance. In addition, we explore the development and applications of nanozyme-based SERS sensors in food contaminants, environmental pollutants, and biomedical markers. The review concludes with perspectives and challenges facing the field, involving the need for deeper understanding of nanozyme principles and mechanisms, development of standardized systems for characterization, and the engineering of nanozymes with tailored properties for specific applications. Finally, we discuss the potential for integrating various techniques with nanozymes to create multi-modal detection platforms, paving the way for the next generation of analytical tools in the fields of food safety, environmental monitoring, and biomedical diagnostics.

Nanozyme-based therapeutic strategies for rheumatoid arthritis

Rheumatoid arthritis (RA) is a prevalent chronic autoimmune disease that leads to severe joint damage and disability. Conventional treatment options are limited by their efficacy and side effect profiles. Nanozymes, nanomaterials with enzyme-like activities, offer a novel therapeutic approach for RA. This review summarizes recent advances in nanozyme-based treatments, focusing on their antioxidant and immunomodulatory roles in mitigating RA. We discuss various nanozymes, including those based on cerium, iron, manganese, silver, copper, platinum, rhodium, and multi-metallic nanozymes, which mimic natural enzymes such as superoxide dismutase, catalase, and peroxidase to reduce oxidative stress. Additionally, we explore nanozyme-based combination therapies that integrate with other strategies, such as vesicles and phototherapy, to achieve synergistic effects and enhance efficacy. This review highlights the significant potential of nanozymes in improving RA treatment, offering a new perspective for future research and clinical applications.

Synergistic Co-Cu Dual-Atom Nanozyme with Promoted Catalase-like Activity for Parkinson's Disease Treatment

Neurodegenerative diseases like Parkinson's disease (PD) are intimately associated with oxidative stress due to the excessive highly reactive oxygen species (ROS), leading to the damage of dopaminergic neurons. Herein, we develop a Co-Cu dual-atom nanozyme (CoCu-DAzyme) by uniformly anchoring Co and Cu active sites onto an AlO(OH) substrate that exhibits remarkable catalase-like catalytic activity, far exceeding that of the Co or Cu single-atom counterparts. The following density functional theory calculations reveal that the Co sites efficiently enable H2O2 adsorption, while Cu sites promote charge transfer, synergistically promoting the catalytic decomposition of H2O2 into H2O and O2. Encouragingly, the developed CoCu-DAzyme notably ameliorates α-synuclein aggregation and alleviates the motor dysfunction inCaenorhabditis elegansPD models by substantively scavenging in vivo ROS. This research shows a novel therapeutic strategy for oxidative-stress-related neurodegenerative disorders by developing well-engineered nanozymes.

Synthesis of Mo-Pt/CeO2 Dual Single-Atom Nanozyme for Multifunctional Biochemical Detection Applications

Elaborated structural modulation of Pt-based artificial nanozymes can efficiently improve their catalytic activity and expand their applications in clinical diagnosis and biochemical sensing. Herein, a highly efficient dual-site peroxidase mimic composed of highly dispersed Pt and Mo atoms is reported. The obtained Mo-Pt/CeO2 exhibits exceptional peroxidase-like catalytic activity, with a Vmax as high as 34.16 × 10-8 m s-1, which is 37.5 times higher than that of the single-site counterpart. Mechanism studies suggest that the Mo atoms can not only serve as adsorption and activation sites for the H2O2 substrate but also regulate the charge density of Pt centers to promote the generation ability of •OH. As a result, the synergistic effect between the dual active sites significantly improves the catalytic efficiency. Significantly, the application of the Mo-Pt/CeO2 catalyst's excellent peroxidase-like activity is extended to various biochemical detection applications, including the trace detection of glucose and cysteine, as well as the assessment of antioxidants' antioxidant capacity. This work reveals the great potential of rational design dual-site active centers for constructing high-performance artificial nanozymes.

Aptamer-functionalized Fe3O4/MWCNTs@Mo-CDs nanozyme for rapid colorimetric detection toward Escherichia coli

The pathogenic bacteria induced foodborne disease has been detrimental to public health worldwide. Herein, the peroxidase (POD)-like Fe3O4/MWCNTs@Mo-CDs (FMMC) nanozyme was applied for the detection of Escherichia coli (E. coli). The E. coli aptamer was conjugated with the surface of the FMMC, which effectively enhanced the POD-like activity attributing to the higher affinity to the substrate, and then specific capture of E. coli in food matrices, leading to the reduction of POD-like activity. Therefore, a robust and facile colorimetric aptasensor was developed for detecting E. coli with a wide linear range of 101-106 CFU/mL, low LOQ of 101 CFU/mL and LOD of 0.978 CFU/mL. The aptasensor demonstrated the satisfied selectivity for E. coli compared to the other strains. This method possessed the potential application for fast in situ screening of foodborne pathogens in food products.

Unleashing the Potential of Single-Atom Nanozymes: Catalysts for the Future

Single-atom nanozymes (SANs) have become a breakthrough in atomically precise catalysis, which relies on the catalytic active site formed by the single-atom itself. From this angle, SANs and their advantages compared to natural enzymes as well as spaces for their application are emphasized. The SANs have outstanding control over their catalytic activities; this is compared with bulk materials and natural enzymes. The structure of the SANs has very promising potential for the next generation of biosensing and biomedical devices and environmental remediation. Although their capabilities are high, difficulties still arise. The specificity, scalability, biosafety, and catalysis mechanisms raise additional issues that require further research. We build up a vision of the perspectives of the better implementation of SANs, which are designed for diagnostic purposes, improving industrial technologies, and creating new sustainable technologies in the food processing industry. AI and machine learning systems may clarify the structure-performance relationship of SANs for improved material and process selectivity. The future of SANs is very promising, and by addressing these challenges and leveraging advancements in artificial intelligence and materials science, SANs have the potential to become powerful tools for a sustainable future.

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.

Diagnosis of Mycobacterium tuberculosis using palladium-platinum bimetallic nanoparticles combined with paper-based analytical devices

In this study, we demonstrate that palladium-platinum bimetallic nanoparticles (Pd@Pt NPs) as the nanozyme, combined with a multi-layer paper-based analytical device and DNA hybridization, can successfully detect Mycobacterium tuberculosis. This nanozyme has peroxidase-like properties, which can increase the oxidation rate of the substrate. Compared with horseradish peroxidase, which is widely used in traditional detection, the Michaelis constants of Pd@Pt NPs are fourteen and seventeen times lower than those for 3,3',5,5'-tetramethylbenzidine and H2O2, respectively. To verify the catalytic efficiency of Pd@Pt NPs, this study will execute molecular diagnosis of Mycobacterium tuberculosis. We chose the IS6110 fragment as the target DNA and divided the complementary sequences into the capture DNA and reporter DNA. They were modified on paper and Pd@Pt NPs, respectively, to detect Mycobacterium tuberculosis on a paper-based analytical device. With the above-mentioned method, we can detect target DNA within 15 minutes with a linear range between 0.75 and 10 nM, and a detection limit of 0.216 nM. These results demonstrate that the proposed platform (a DNA-nanozyme integrated paper-based analytical device, dnPAD) can provide sensitive and on-site infection prognosis in areas with insufficient medical resources.