Exploring the Specificity of Nanozymes

Colorimetric detection of fluoroquinolones via MOF inhibition and thiol-response oxidase-mimicking reactions

Developing a selective colorimetric assay for fluoroquinolones (FQs) that show visible color response is highly desired, which is challenging because FQs show extremely similarity in structure and inherently absorb light in the UV color range. In this work, a selective colorimetric assay for pefloxacin (PEF) was fabricated through integrating two rection systems: the inhibition effects of PEF on the AChE-like activities of Al3+ decorated MOF-808 (MOF-808-Al) and the thiol-response oxidase-mimicking reaction of MnO2 nanosheets. The MnO2 nanosheets, due to their oxidase-mimicking properties, can oxidize the colorless 3, 3', 5, 5'-tetramethylbenzidine (TMB) into its blue-colored oxidized form, TMB+. Assisted by the synergistic action of metal-OH and Lewis acid sites, MOF-808-Al exhibits AChE-like activities. These activities catalyze the decomposition of acetylthiocholine into thiocholine. Thiocholine has a stronger reactivity compared to TMB; it can reduce the MnO2 nanosheets, which in turn prevents the color response. In addition, PEF inhibits the AChE-like activities of MOF-808-Al by blocking its active sites. The quantitative detection of PEF is accomplished by recording the blue color response of the system, both in buffer solutions and in commercial meat samples. This assay demonstrates excellent tolerance and selectivity against various interfering substances, antibiotics, and pesticides.

A catalase-like nanozyme of high activity and stability in acidic solutions for enzyme immobilization and chemoenzymatic cascade conversion of glucose to gluconic acid

Gluconic acid is widely used in food and pharmaceutical. However, its bio-synthesis by glucose oxidase (GOx) is blocked by depletion of dissolved O2, reduction of pH value, and accumulation of hydrogen peroxide (H2O2). To remove the by-products and replenish O2, developing a nanozyme with high catalase (CAT)-like activity and stability under acidic conditions is a prescription. Herein, we developed a manganese-based nanozyme (ps-MnOx-BSA) through a stepwise strategy and encapsulated it in Fe-doped zeolitic imidazolate framework-8 (FZ). The as-prepared ps-MnOx-BSA@FZ (MFZ) exhibited not only high stability and CAT-like activity but also exceptionally no peroxidase-like activity at pH 5.5. Thereafter, GOx@MFZ was fabricated by the immobilization of GOx on MFZ and utilized for gluconic acid synthesis with a yield of 98.3 % within 30 min. GOx@MFZ retained 92.3 % of its initial activity after six batches. This work provided a novel strategy for the design of acid-resistant CAT-like nanozyme toward sustainable gluconic acid production.

Construction of nanozyme based with mixed valence manganese oxide loaded on defective metal-organic frameworks for sensitive detection of biomarker procalcitonin

Nanozymes possess the advantages of high stability, adjustable catalytic activity and simple preparation processes, which position them as a promising alternative to natural enzymes. In this work, an oxidase-like nanozyme has been prepared by loading mixed valence manganese oxides (MnxOy) on defective PCN-224 MOFs (dPCN). Dodecanoic acid was utilized to introduce abundant mesoporous defects into the dPCN, allowing manganese oxide to grow in situ on the surface and within the pores. The mixed valence state of manganese oxides endowed the MnxOy@dPCN nanozyme (MdP) with redox and catalytic properties, and the high oxidase-like catalytic performance of MdP for TMB substrate also originated from its favorable electrical conductivity and affinity to the substrate. The reactive oxygen species of the catalytic reaction were mainly singlet oxygen (1O2) and peroxyl radicals (·O2-). Without the existence of hydrogen peroxide (H2O2), the nanozyme can rapidly and efficiently oxidize TMB substrate into blue oxidation state, which has strong absorbance at 650 nm. An immunosensor for detecting biomarker procalcitonin (PCT) in human serum samples has been established based on the high catalytic property of MdP nanozyme. The immunoassay for PCT has satisfactory accuracy and repeatability, and its linear detection range can reach to be 0.05-100 ng mL-1 with a limit of detection (LOD) of 0.011 ng mL-1. The result affords a promising idea to construct oxidase-like nanozyme, and provides a method for sensitive determination of PCT in complex matrices.

Mannose-modified multifunctional iron-based nanozyme for hepatocellular carcinoma treatment by remodeling the tumor microenvironment

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths worldwide, with conventional treatments often accompanied by severe side effects. Recently, nanozymes have been extensively employed in cancer therapy due to their enhanced enzymatic activities, stability compared to native enzymes. However, a standalone nanozyme exhibits insufficient targeting capability and fails to specifically localize to the pathological site. In this study, we successfully synthesized a multifunctional iron-based-nanozyme delivery system - Fe3O4-OA-DHCA-PEI-MAN@DSF modified with PEI and MAN by the thermal decomposition method. This mannose-modified nanozyme can specifically target HCC cells via an external magnetic field and mannose-mannose receptor (MRC2) binding. In addition, it exhibits good biocompatibility and pH-dependent drug release characteristics. Within the acidic tumor microenvironment, the iron-based nanozyme initiates intracellular fenton reactions, boosting reactive oxygen species (ROS) production, which ultimately induces apoptosis in HCC cells. Concurrently, the disulfiram small molecule released from the Fe3O4-OA-DHCA-PEI-MAN@DSF nanozyme binds to the FROUNT factor within monocyte-macrophages, thereby inhibiting their response to chemotactic signals emitted by liver cancer cells. This process ultimately suppresses the recruitment of macrophages by HCC cells, reshaping the tumor microenvironment and supporting effective liver cancer treatment. Moreover, this nanozyme system holds potential for MRI-guided targeted chemotherapy combined with chemodynamic therapy, aiming to refine the early diagnosis and precision treatment of hepatic carcinoma, and paving the way for the creation of sophisticated integrated nanoplatforms melding diagnostic and therapeutic functionalities.

Selenium as a brightening agent for peroxidase-like activity regulation of MXene@CeO2 sensing platform

Selenium is a nutritionally essential trace element for human health, but efficient or excessive intake both causes physiological diseases. Here, we propose that selenium as a brightening agent significantly increase the peroxidase (POD)-like activity of MXene@CeO2, which CeO2 nanoparticles in-situ grow on MXene as the sensing platform. Based on the selenium-stimulated POD-like activity of MXene@CeO2, a simple, low-cost, and reliable colorimetric method is constructed for quantitative analysis of selenium. The great advantage of MXene@CeO2 platform selecting selenium as brightening agent exhibits good selectivity for other 23 interfering ions, allowing the discrimination of selenium in practical samples rapidly and precisely even at 3.5 nM. Moreover, MXene@CeO2 platform selectively catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) instead of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium (ABTS) under the same condition. This study not only offers a utility sensing platform for quick detection of selenium but also opens an avenue for the rational design of element sensors for point-of-care application.

A Bimetallic Nanozyme Synergistic Effect-Driven Enzyme Cascade Nanoreactor for Instant Immunoassay

This study presents a colorimetric sensor for cancer screening utilizing the bifunctional enzyme activity of NiCo Prussian blue analogue (PBA), a PBA material. By introducing oxygen vacancies and employing a dual-metal doping strategy, NiCo PBA overcomes the limitations in catalytic activity observed in single-metal-doped materials (such as Ni PBA and Co PBA), significantly enhancing both peroxidase-like (POD) and catalase-like (CAT) activities. Compared to single-metal-doped Ni PBA and Co PBA, NiCo PBA exhibited a 30.08-fold increase in POD activity and a 4.83-fold increase in CAT activity, demonstrating higher sensitivity in carcinoembryonic antigen (CEA) detection. By integrating NiCo PBA with a cascade catalytic reaction principle, we developed a highly efficient and sensitive CEA detection method. NiCo PBA was utilized as a catalytic material in this method. Under the action of glucose oxidase, the decomposition of hydrogen peroxide was catalyzed by NiCo PBA, and oxygen was generated. Furthermore, a blue flocculent substance was produced when NiCo PBA was reacted with a chromogenic substrate. Through mutual verification by these two methods, the quantitative determination of CEA in serum samples was achieved. The experimental results demonstrated that the POD-like activity detection range was 0.2-50 ng mL-1, with a limit of detection (LOD) of 0.061 ng mL-1, while the CAT-like activity detection range was 0.1-20 ng mL-1, with an LOD of 0.028 ng mL-1. The sensitivity of this method was substantially increased compared to monometallic materials. Furthermore, this strategy possesses good scalability and can be adapted for the detection of various analytes by replacing different recognition units, providing an efficient detection platform for early cancer screening.

Novel Nanozymes with Sample Pretreatment Function for Specific Multimodal Detection of Perfluorooctanesulfonate

Perfluorooctanesulfonate (PFOS), a ubiquitous and persistent organic pollutant, poses severe health risks due to its bioaccumulation and recalcitrance. Despite existing detection methods, the need for rapid, sensitive, and cost-effective PFOS quantification remains unmet, particularly for on-site and mass sample analysis. Here, we introduce an innovative "three-in-one" multifunctional nanohybrid, Fe3O4@MON-F@Ru, which revolutionizes the detection of PFOS through a novel integration of nanozymes and microporous organic networks (MONs). This nanohybrid enables sensitive colorimetric and photothermal signaling for PFOS detection, addressing the long-standing challenge of selectivity in nanozyme-based analytical methods. The Fe3O4 core enables magnetic separation, while the fluorinated MONs shell specifically interacts with PFOS through F-F bonding and electrostatic forces, concurrently serving as a high-density carrier for Ru nanozymes. The presence of PFOS significantly inhibits catalytic activity, offering a rapid and specific colorimetric method with a detection limit as low as 15.4 nM. Additionally, based on the near-infrared (NIR) laser-driven photothermal properties of oxidized 3,3',5,5'-tetramethylbenzidine (TMB), the photothermal analysis for PFOS detection was also established. This study not only advances the design of nanozymes with integrated sample pretreatment capabilities but also pioneers a portable, dual-signaling sensing strategy for PFOS detection, offering profound implications for environmental monitoring and public health safety.

Nanoarchitectured biomass-waste derived activated charcoal nanozymes and its application in visual analysis of nitrite in pickled food

The emerging field of nanozymes has introduced unprecedented opportunities and challenges for activated charcoal materials derived from biomass waste. By incorporating specific nanostructures or elements, it is possible to overcome the limitations of traditional activated charcoal, such as insufficient catalytic active sites and poor electron transfer efficiency, thereby unlocking its full potential for various applications. In this study, we successfully synthesized trace Fe-doped activated charcoal (Fe-AC) with a graphene-like structure from biomass waste. The Fe atoms were uniformly dispersed on the activated charcoal support, which possessed a high surface area. This not only significantly increased the number of catalytic active sites but also enhanced electron transfer efficiency, substrate mobility, and collision probability. Compared to pristine activated charcoal, the synthesized Fe-AC exhibited multiple enzyme-mimetic activities, including oxidase-like, peroxidase-like, and catalase-like activities. By leveraging its peroxidase-like activity in conjunction with nitrite-specific diazotization reactions, we developed a portable, smartphone-assisted, on-site ratiometric colorimetric hydrogel sensor for nitrite detection. Utilizing smartphone-based digital imaging, this sensor enabled the quantitative analysis of nitrite at concentrations ranging from 1 to 200 μmol/L, with a detection limit as low as 1 μmol/L. The approximate range of hazardous nitrite concentrations could be easily identified with the naked eye, and the proposed strategy was successfully applied to real sample analysis. This sensor not only maximizes the utilization of waste resources, thereby reducing production costs, but also offers greater economic feasibility and environmental sustainability. Given these advantages, it holds promise for broader applications in various fields.

Dual-mode sensing platform based on an iodide ion synergistic covalent triazine frameworks (CTFs) for point-of-care testing (POCT) of acetylcholinesterase

Acetylcholinesterase (AChE) plays a critical role in maintaining nervous system homeostasis and coordinating essential biological reactions. AChE is an important biomarker for early diagnosis and treatment, including Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD). Therefore, developing efficient and immediate sensing platforms for AChE detection is crucial for advancing early diagnostic tools. In this study, we developed a dual-mode colorimetric/photothermal sensing platform based on iodide ion-synergized covalent porphyrin-triazine backbone nanozymes (Zn-CTF/I) to detect AChE with high sensitivity and reliability. The synergistic interaction between iodide ions and zinc atoms effectively modulated the electronic structure of the catalytic active site, significantly enhancing the peroxidase-like (POD-like) activity of Zn-CTF/I. This enhancement led to a 10-fold reduction in the AChE detection limit compared to controls, with a minimum detection limit of 0.003 U L-1, outperforming other reported assays. The integration of temperature-based photothermal signals with colorimetric detection improved the platform's accuracy and reliability. The system also demonstrated excellent recovery performance in detecting AChE in complex serum samples. The proposed dual-mode sensing platform provides a sensitive, reliable, and robust tool for AChE detection, with promising applications in early diagnosis and treatment monitoring of neurodegenerative diseases.

Hydrogen Incorporation Selectively Modulates the Catalytic Performance of Pd Nanozymes for Cascade-Catalytic Tumor Therapy

Pd-based nanozymes have emerged as promising alternatives to natural enzymes, but their application is still constrained due to suboptimal activity and poor specificity. As efficient hydrogen storage nanomaterials, the specific implications of implanted hydrogen on the enzyme-mimicking activity of Pd-based nanomaterials remain largely uninvestigated. In this study, we discovered that hydrogenation process significantly enhances the enzyme-like activity of Pd-based nanomaterials, although reaction specificity varies in dependence on the synthetic route of Pd hydrides. Pd/H2 nanocubes (NCs), which are synthesized by directly injecting hydrogen gas into a solution containing Pd NCs, exhibit a selective enhancement in antioxidative activity against cytotoxic hydrogen peroxide (H2O2), superoxide anion (O2•-), and hydroxyl radical (•OH) due to the sustained release of bioreductive hydrogen. In contrast, stable Pd hydride NCs, which are prepared through the in situ catalytic decomposition of alternative sources of hydrogen atoms, exhibit a remarkable enhancement in exclusive H2O2 activation pathways, specifically exhibiting peroxidase (POD)-like and catalase (CAT)-like activities. Multiple spectroscopic characterizations and density functional theory (DFT) calculations confirmed that this high catalytic activity and specificity of PdH NCs arise from lattice tensile strain and electronic structure change. Based on these findings, a PdH/glucose oxidase (GOx) nanocomplex was developed for cascade catalysis in tumor therapy. This work not only reveals that hydride formation can influence both the activity and selectivity of Pd nanozymes but also provides a viable strategy for the precise regulation of specific enzyme-like activity in hydrogen-loading nanozymes.

Photosensitive Oxidase Mimics for Spontaneous and Sustainable Pathogen Disinfection in Personal Protective Equipment

The development of personal protective equipment (PPE) is essential to control the spread of infectious diseases. However, traditional PPE has significant drawbacks, such as a lack of antibacterial capacity and nonreusability, which may result in direct or indirect secondary infections. Herein, we propose an octahedral (Fe-O6) Fe-gallate (Fe-GA) metal-organic framework nanozyme with light-enhanced oxidase-like (OXD-like) activity and extend the use onto nonwoven fabric (Fe-GA/NWF) by hot pressing. Specifically, visible-light-mediated carrier migration and the activity of the OXD-like species synergistically enhance the production of reactive oxygen species, achieving superior antibacterial effects without the addition of any chemical additives. In this case, Fe-GA/NWF spontaneously inactivates over 99.9% of real microbial aerosols and demonstrates excellent mechanical properties, reusability (15 cycles), and biocompatibility. Moreover, Fe-GA/NWF can be used as an ideal antibacterial platform for KN95 masks and protective clothing and can be extended to other substrates. This work provides a promising strategy to develop self-antibacterial PPE in complex environments.

Dual FeCo single-atom nanozymes with specific oxidase-like activity for sensitive detection of aflatoxin B1

Single-atom nanozymes (SAzymes) with well-defined metal-nitrogen-carbon coordination structures are of great interest for the development of colorimetric biosensing. However, their catalytic efficiency and specificity is restricted due to the limited number of single metal atoms that can serve as catalytic centre. Therefore, the construction of SAzymes with high activity and specificity is vital but remains challenging. To address these issues, we prepared a bimetallic SAzymes with an independent iron and cobalt structure (FeCo/NC), and the oxidase-like activity was enhanced by >112.8% relative to Fe/NC. This preparation strategy increased the amount of single metal atoms loaded, resulting in a strong synergistic effect and proximity-orientation effects due to the unique structure of single Co and Fe atoms coexisting on graphene. The oxidase-mimicking activity of FeCo/NC was specifically enhanced by co doping, although the activities of peroxidase-, superoxide dismutase-, or catalase-like were not significantly affected. In light of these discoveries, as a symbol of the proof-of-concept, FeCo/NC-based colorimetric immunoassays were developed for sensitive detection of aflatoxin B1 (AFB1), achieving a linear range of 0.01-10 ng/mL and a detection limit of 0.005 ng/mL. This study provides a convenient strategy for promoting the catalytic activity and specificity of SAzymes, thereby enhancing their potential in biosensing.

Ligand-Engineering MoS2-Osmium Heterostructure as Highly Active and Specific Peroxidase-Mimic Nanozyme for Interference-Free and Multimode Biosensing

It is still a challenge to fabricate nanozymes with both of high catalytic activity and specificity. Herein, a ligand engineering method is developed to fabricate osmium (Os) nanocluster-Molybdenum disulfide (MoS2) heterostructure with superior peroxidase-specific activity. It has been verified that polyvinylpyrrolidone (PVP) as ligands can confine amorphous Os nanoclusters growing on the MoS2 nanosheet, mechanism studies indicated that PVP acts as appropriate size-limiting reagent and electronic transmission bridge between of Os and MoS2 which can synergistically improve the peroxidase-specific activity. Moreover, the ligand engineering will not affect the peroxidase-mimic specificity of MoS2-Os. Further, it is found that MoS2-Os possessed superior photothermal conversion efficiency, therefore, MoS2-Os can be used as colorimetric and photothermal dual-mode tags. MoS2-Os combined lateral flow strip is established for breast cancer HER2+ exosomes colorimetric and photothermal detection with superior sensitivity and broader liner range, MoS2-Os based interference-free salivary glucose biosensor is also established with a LOD of 0.1 µM, almost 100-fold sensitivity than that of Glucose Assay Kit. Therefore, this work developed a ligand-engineering strategy to regulate Os nanocluster on MoS2 and improve the peroxidase-specific activity, the multifunctional MoS2-Os nanozyme can be used for accurate and multimode biosensing in varies scenes.

Recent progress of noble metal-based nanozymes: structural engineering and biomedical applications

Due to their tunable catalytic activity, high chemical stability, and favorable electronic structure, noble metal-based nanozymes that can mimic important biocatalytic processes have attracted great attention. Rational structural design of noble metal-based nanozymes can endow them with excellent enzyme-like activities, enhanced sensitivity and stability, as well as unique physicochemical functionalities towards various biomedical applications such as sensing, diagnostics, and disease treatment. This review summarizes the recent progress in structural engineering of noble metal-based nanozymes and emphasizes the relationship between key structural factors of nanozymes and their enzyme-like properties in various enzyme-mimicking reactions. The diverse applications of noble metal-based nanozymes in biosensors, antibiosis, and disease treatment are further introduced. Finally, current challenges and future research directions in noble metal-based nanozymes are discussed. This review could offer scientific guidance to design and fabricate advanced nanozymes with enhanced functionality and performance towards clinical, environmental and biomedical applications.

Hyaluronic acid-modified PtPdCo-CQ nanocatalyst with triple enzyme-like activities regulates macrophage polarization and autophagy levels for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and imbalanced macrophage polarization. Pro-inflammatory M1 macrophages exacerbate joint damage through excessive production of reactive oxygen species (ROS), while anti-inflammatory M2 macrophages are prone to ferroptosis, limiting the long-term efficacy of existing nanozyme therapies. This study aimed to develop a novel nanocatalyst combining efficient ROS scavenging and M2 macrophage protection to synergistically regulate macrophage polarization and autophagy levels for sustained RA remission. We designed a hyaluronic acid-modified PtPdCo-CQ nanocatalyst (HPPCQ) with triple enzyme-like activities-superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). In vitro experiments demonstrated that HPPCQ activated the Nrf2/HO-1 antioxidant pathway by scavenging ROS, promoted M1-to-M2 phenotypic repolarization, and protected M2 macrophages from autophagy-dependent ferroptosis via controlled release of chloroquine (CQ). In a collagen-induced arthritis (CIA) mouse model, HPPCQ targeted inflamed joints, significantly reducing clinical scores, synovial hyperplasia, and pro-inflammatory cytokine levels (TNF-α, IL-1β). Histological analysis revealed markedly alleviated cartilage destruction and inflammatory infiltration in HPPCQ-treated mice. By integrating ROS scavenging, macrophage reprogramming, and ferroptosis inhibition, this work provides a novel therapeutic strategy with enhanced efficacy and durability for RA treatment.

Copper Nanoparticles Loaded on N-Doped Carbon Nanotubes with Enhanced Peroxidase-Like Performance for Gallic Acid Detection in Food

The accurate monitoring of gallic acid (GA) in foodstuffs is crucial for safeguarding human health. The application of nanozymes in colorimetric assays offers a promising route for assessing the GA level. However, the development of high-efficiency and cost-effective nanozymes for quick GA detection holds a substantial challenge. In this study, copper (Cu) nanoparticles (NPs) immobilized on N-doped carbon nanotubes (NCNTs) have been prepared, exhibiting exceptional peroxidase (POD)-like activity for GA detection in food. The anchoring of Cu nanoparticles with NCNTs enables their excellent antioxidant capacity. Then, the obtained Cu NPs/NCNTs show remarkable POD-like activity in catalyzing TMB oxidation, with the attributes of long-term storage stability and reproducibility. Electrochemical assays and radical scavenging experiments reveal a dual mechanism action (involving reactive oxygen species and electron transfer) for the POD-mimicking activity. Furthermore, the developed colorimetric catalytic platform is applied to detect GA in actual tea samples, demonstrating high reliability and potential utility for GA monitoring in the food industry.

Hierarchical Assembly of Hemin-Peptide Catalytic Systems on Graphite Surfaces

The formation of molecular hybrid systems with cofactors and peptides on graphite electrodes has recently been demonstrated. The design of peptide sequences is crucial for forming robust catalytic molecular systems on electrodes. However, the relationship between peptide sequences, molecular structure, and catalytic performance has not been fully explored. In this study, we employed peptides with simple dipeptide repeats, which effectively immobilize hemin, to construct a stable catalytic system and investigated the molecular basis of their self-assembly and catalytic activity by varying the sequence. Among peptides containing the dipeptide sequences (YH, VH, and LH), YH demonstrated the most efficient immobilization of hemin, which is catalytically active in electrochemical reactions. Using advanced molecular visualization techniques, specifically frequency modulation atomic force microscopy (FM-AFM), we characterized the well-ordered structures of these peptides on graphite electrodes, revealing their molecular-scale organization. Our findings in electrochemical characterizations include a quantitative evaluation of the surface density of hemin immobilized by self-assembled peptides and the catalytic activity of the peptide-hemin hybrid system under electrochemical conditions in the presence of H2O2. The strong peptide-peptide and peptide-hemin interactions, facilitated by π-π interactions of tyrosine residues, contribute to the system's stability and efficiency. The dipeptide repeats serve as a useful platform to investigate the role of important amino acids, beyond histidine, in stably immobilizing cofactors. These results highlight the potential for developing durable and efficient catalytic interfaces in electrochemical applications.

Amino-Acid-Engineered Bionanozyme Selectivity for Colorimetric Detection of Human Serum Albumin

Nanozymes are emerging nanomaterials owing to their superior stability and enzyme-mimicking catalytic functions. However, unlike natural enzymes with inherent amino-acid-based recognition motifs for target interactions, manipulating nanozyme selectivity toward specific targets remains a major challenge. In this study, we introduce the de novo strategy using the supramolecular assembly of l-tryptophan (l-Trp) as the recognition amino acid with copper (Cu) ions for creating a human serum albumin (HSA)-responsive bionanozyme. This amino-acid-engineered bionanozyme enables selective colorimetric detection of HSA, a critical urinary biomarker for kidney diseases, overcoming the challenge that HSA is neither a typical substrate nor an inhibitor for most nanozymes. Kinetic studies and competitive tests reveal that HSA subdomain IIIA binding to l-Trp sites limits the electron-transfer-induced structural changes of l-Trp-Cu chelate rings, resulting in noncompetitive inhibition. This inhibition effect is significantly stronger than that observed for canonical amino acids, common proteins, and urinary interference species. Colorimetric monitoring of bionanozyme activity enables sensitive HSA detection with a detection limit of 1.3 nM and a quantification range of 2 nM to 10 μM. This approach is exceptionally more sensitive and offers a broader detection range compared to conventional colorimetric and fluorescent methods, suitable for diagnostics across various clinical stages of disease. This innovative rational strategy to designing and manipulating selective nanozyme-target interactions not only addresses the limitations of nanozymes but also expands their precise applications in complex biological systems.

Nanozymes meet hydrogels: Fabrication, progressive applications, and perspectives

Nanozyme, a class of emerging enzyme mimics, is the nanomaterials with enzyme-mimicking activity, which has obtained significant and widespread applications in various fields. However, they still face many challenges in practical applications (e.g., instability and low biocompatibility in the physiological environments), which affect their widespread applications to a certain extent. Hydrogels with superior performances (e.g., the controllable degradability, good biocompatibility, hydrophilic properties, and adjustable physical properties) may provide a promising strategy to make up the existing deficiencies of nanozymes in practical applications. Thus, the sapiential combination of nanozymes with hydrogels endows nanozyme hydrogels with both characteristics of nanozymes and properties of hydrogels, making nanozyme hydrogels become novel multifunctional materials. In this review, we comprehensively summarizes the preparation, properties, and progressive applications of nanozyme hydrogels. First of all, the main design and preparation strategies of nanozyme hydrogels are considerately summarized. Then, the properties of different nanozyme hydrogels are introduced. In addition, sophisticated applications of nanozyme hydrogels in the fields of biosensing, biomedicine applications, and environmental are comprehensively summarized. Most importantly, future obstacles and chances in this emerging field are profoundly proposed. This review will provide a new horizon for the development and future applications of novel nanozyme hydrogels.

Hyaluronan-modified nanoceria for dry eye disease treatment

Dry eye disease (DED), a prevalent ocular disorder, affects nearly half the global population, bringing enormous health and economic burden. Currently, the predominant treatments for DED involve the administration of artificial tears, which is often hindered by continuous administration and constant reactive oxygen species (ROS) stimulus. Therefore, hyaluronan (HA)-modified cerium oxide (CeO2) nanoparticles, HA-CeO2, were developed to achieve simultaneous ROS scavenging and enhanced tear film stability. HA-CeO2 was demonstrated to effectively scavenge ROS while concurrently downregulating the expression of inflammatory factors, such as MMP9 and IL-1β. Moreover, the anti-oxidative and anti-inflammatory effects of HA-CeO2 were further confirmed through a DED mouse model. In addition, the biocompatibility and safety of HA-CeO2 make it a promising treatment option for DED associated with inflammation and oxidative stress, offering novel insights into utilizing nanozymes in treating inflammation-oxidative stress-related diseases.

Dual-driven selenium Janus single-atom nanomotors for autonomous regulating mitochondrial oxygen imbalance to catalytic therapy of rheumatoid arthritis

O2 deficiency and excessive reactive oxygen and nitrogen species (RONS) in macrophage mitochondria is a key factor causing oxygen imbalance in rheumatoid arthritis microenvironment (RAM). Although nanocatalytic therapy that simultaneously produce O2 and eliminate RONS offer a novel strategy for RA therapy, the therapeutic efficacy of nanozymes is limited by the lack of autonomous targeting into mitochondria. Herein, we constructed a Janus-structured nanomotor (Pd@MSe) with autonomous targeting ability by embedding Pd single-atom nanozymes into mesoporous selenium (MSe) nanozymes, and obtained a composite nanomotor (Pd@MSe-TPP) with dual-driven forces by modifying with triphenylphosphine (TPP) in MSe hemisphere. In RAM, Pd@MSe-TPP nanomotor achieved autonomously target into macrophages mitochondria with the driven of generation O2 and TPP targeting effect, moreover under the single-atom effect of the Pd nanozymes enhanced electronic transfer between nanozymes, which significantly boosted GPx catalytic activity further effectively enhanced the diffusion of Pd@MSe-TPP nanomotor, thus quickly resorted the oxygen balance. Additionally, while regulating oxygen imbalance, Pd@MSe-TPP nanomotor enable rapidly blocked the inflammatory cascade, restored mitochondrial function and alleviated inflammation, further prevented cartilage degradation and effectively inhibited RA progression. Therefore, the exquisitely designed nanoplatform to regulation arthritic microenvironment provides a new direction for the RA therapy and the clinical translation of nanomedicine.

Biomass spinach-drived metal-free carbon dots-based nanozyme for multimodal nitrite sensing and functionalized by glucose oxidase as ROS amplifiers to enhance tumor therapy

The metal-free carbon dots (CDs) nanozyme, which is endowed generation of multiple reactive oxygen species (ROS), followed by highly selective chemical sensing, remains a critical challenge. The exceptional biocatalytic properties of glucose oxidase (GOx) have spurred the development of GOx-functionalized nanocatalysts for cancer therapy. Here, the innovative free metal-doped CDs and CDs@GOx nanozymes with peroxidase (POD)-like activity were developed, which specifically catalyzed H₂O₂ to engender multiple ROS including •O2-, 1O2 and •OH, to oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue ox-TMB, indicating both nanozymes can be as ROS amplifiers to enhance tumor therapy. The introduction of NO₂- triggered a distinct color change from blue to green ascribed to the diazotization of ox-TMB along with quenching the fluorescence of CDs, which endowed high selectivity and sensitivity for NO2- detection. Furthermore, CDs catalyzed endogenous H₂O₂ within tumor cells, to effectively destroy cancer cells rather than normal cells. As expected, CDs@GOx preferentially catalyze glucose in cancer cells to further supply H2O2, allowing more ROS accumulation, thereby realizing the integration of starvation therapy and ROS therapy of cancer. Notably, in vivo anti-tumor efficacy demonstrated that CDs and CDs@GOx markedly inhibited tumor growth without external stimulation with neglected side effects. Compared to the saline group, the tumor size was reduced by 3 or 4 times for CDs and CDs@GOx, respectively. This metal-free CDs tailors a convenient and impactful nanoplatform for chemical sensing and as ROS amplifiers to enhance tumor therapy by non-invasive treatment.

Oxygen vacancy-enriched NiO nanozymes achieved via facile annealing in argon for detection of L-Cys

Nickel oxide (NiO) nanozymes, as an excellent oxidase mimic, have been widely used in fluorescence biological detection, water pollutant analysis, food safety and cell imaging. However, a great challenge in fully realising these applications is regulating their crystalline micro-/nano-structure and composites to achieve high enzyme activity and high specific surface area. Herein, we applied a very simple thermal annealing treatment to restructure the calcined precursor of NiO. Importantly, it was found that the oxygen vacancy (OV) concentration of the targeted NiO nanozyme significantly increased when the annealing atmosphere was argon rather than air. Moreover, the as-prepared novel NiO sample (NiO-OV) nanosheets achieved about 2-fold enhancement in their specific surface area. It is believed that a higher OV concentration and larger specific surface area increase enzyme activity by accelerating the electron transfer rate and improving catalytic interfaces. The significant improvement in the enzyme activity of NiO-OV was verified using the fluorescence "turn-on" experiment of Amplex Red (AR). Finally, using the NiO-OV/AR system, we constructed a highly sensitive enzyme sensor on L-Cys with a detection limit of 37.8 nM. The sensor also displayed excellent specificity for ten typical amino acid interferents.

Zinc Single-Atom Nanozyme As Carbonic Anhydrase Mimic for CO2 Capture and Conversion

Single-atom nanozymes (SANs) are a class of nanozymes with metal centers that mimic the structure of metalloenzymes. Herein, we report the synthesis of Zn-N-C SAN, which mimics the action of the natural carbonic anhydrase enzyme. The two-step annealing technique led to a metal content of more than 18 wt %. Since the metal centers act as active sites, this high metal loading resulted in superior catalytic activity. Zn-SAN showed a CO2 uptake of 2.3 mmol/g and a final conversion of CO2 to bicarbonate of more than 91%. CO2 was converted via a biomimetic process by allowing its adsorption by the catalyst, followed by the addition of the catalyst to HEPES buffer (pH = 8) to start the CO2 conversion into HCO3 -. Afterward, CaCl2 was added to form a white CaCO3 precipitate, which was then filtered, dried, and weighed. Active carbon and MCM-41 were used as controls under the same reaction conditions. According to the findings, the CO2 sequestration capacity was 42 mg of CaCO3/mg of Zn-SAN. Some amino acids (AAs) with binding affinity for Zn were able to suppress the enzymatic activity of Zn-SAN by blocking the active metal centers. This strategy was used for the detection of His, Cys, Glu, and Asp with detection limits of 0.011, 0.031, 0.029, and 0.062 μM, respectively, and hence was utilized for quantifying these AAs in commercial dietary supplements.

Heterojunction-Mediated Co-Adjustment of Band Structure and Valence State for Achieving Selective Regulation of Semiconductor Nanozymes

Improving reaction selectivity is the next target for nanozymes to mimic natural enzymes. Currently, the majority of strategies in this field are exclusively applicable to metal-organic-based or organic-based nanozymes, while limited in regulating metal oxide-based semiconductor nanozymes. Herein, taking semiconductor Co3O4 as an example, a heterojunction strategy to precisely regulate nanozyme selectivity by simultaneously regulating three vital factors including band structure, metal valence state, and oxygen vacancy content is proposed. After introducing MnO2 to form Z-scheme heterojunctions with Co3O4 nanoparticles, the catalase (CAT)-like and peroxidase (POD)-like activities of Co3O4 can be precisely regulated since the introduction of MnO2 affects the position of the conduction bands, preserves Co in a higher oxidation state (Co3+), and increases oxygen vacancy content, enabling Co3O4-MnO2 exhibit improved CAT-like activity and reduced POD-like activity. This study proposes a strategy for improving reaction selectivity of Co3O4, which contributes to the development of metal oxide-based semiconductor nanozymes.

Sensitive colorimetric sensing of dopamine and TYR based on enhanced HRP-like activity of CuNi/Fe LDHs nanozymes

CuNi/Fe LDHs with HRP-like activity (nanozyme) have been prepared. Contrary to the expected design, free dopamine (DA) was found to greatly enhance the catalytic performances of CuNi/Fe LDHs nanozyme. As far as we know, this is the first report that free DA boosts the catalytic performances of LDHs. Given the superior HRP-like enzyme activity of DA-CuNi/Fe LDHs, a colorimetric method for DA and tyrosinase (TYR) assay with high sensitivity and specificity was established, and it was successfully applied to quantify DA in artificial cerebrospinal fluid and TYR in newborn calf serum. The acquired insights in DA-CuNi/Fe LDHs will contribute to future rational design of other high-performance nanozymes. In addition, the novel DA and TYR assay pave a way for designing further nanozymes-based colorimetric chemo/biosensors.

Research progress on the synthesis, performance regulation, and applications of Prussian blue nanozymes

Nanocatalytic medicine offers a novel solution to address the issues of low efficacy, potential side effects, and the development of drug resistance associated with traditional therapies. Therefore, developing highly efficient and durable nanozymes is of great significance for treating diseases related to oxidative stress. In recent years, prussian blue nanoparticles (PBNPs) have been demonstrated to possess multiple enzyme-like catalytic activities and are thus referred to as prussian blue nanozymes (PBNZs). Their excellent biocompatibility and biodegradability make PBNZs promising candidates as biomedical materials. Due to their remarkable catalytic activities, PBNZs have shown great potential in various biomedical applications, such as heavy metal detoxification, antioxidative damage, and anticancer therapies. This paper systematically summarizes the Synthetic strategies of PBNZs, analyzes the regulatory factors of their catalytic performance, and highlights the corresponding modulation methods. Furthermore, the biomedical applications of PBNZs are also reviewed. This study aims to provide researchers with insights and inspirations for the design and preparation of high-performance PBNZs.

Supramolecular Nanozymes Based on Self-Assembly of Biomolecule for Cancer Therapy

Natural enzyme systems possess extraordinary functions and characteristics, making them highly appealing for use in eco-friendly technologies and innovative cancer treatments. However, their inherent instability and structural complexity often limit their practical applications, leading to the exploration of biomolecular nanozyme alternatives. Supramolecular nanozymes, constructed using self-assembly techniques and various non-covalent interactions, have emerged as a promising solution. Amino acids, peptides, and protein motifs offer flexible building blocks for constructing these nanozymes. Importantly, the well-defined structural regulation mechanisms of biomolecular nanozymes, along with their unique properties as fundamental biological modules in living systems-such as selectivity, permeability, retention, and biocompatibility-present new opportunities for cancer therapy. This review highlights recent advances in supramolecular self-assembled nanozymes, including peroxidases, oxidases, catalases, superoxide dismutases, and other nanozyme systems, as building blocks for tumor therapy. Additionally, it discusses precise functional modulation through supramolecular non-covalent interactions and their therapeutic applications in targeting the tumor microenvironment. These studies provide valuable insights that may inspire the design of novel supramolecular nanozymes with enhanced catalytic selectivity, biocompatibility, and tumor-killing efficacy.

Molecularly Imprinted Nanozymes with Substrate Specificity: Current Strategies and Future Direction

Molecular imprinting technology (MIT) stands out for its exceptional simplicity and customization capabilities and has been widely employed in creating artificial antibodies that can precisely recognize and efficiently capture target molecules. Concurrently, nanozymes have emerged as promising enzyme mimics in the biomedical field, characterized by their remarkable stability, ease of production scalability, robust catalytic activity, and high tunability. Drawing inspiration from natural enzymes, molecularly imprinted nanozymes combine the unique benefits of both MIT and nanozymes, thereby conferring biomimetic catalysts with substrate specificity and catalytic selectivity. In this review, the latest strategies for the fabrication of molecularly imprinted nanozymes, focusing on the use of organic polymers and inorganic nanomaterials are explored. Additionally, cutting-edge techniques for generating atom-layer-imprinted islands with ultra-thin atomic-scale thickness is summarized. Their applications are particularly noteworthy in the fields of catalyst optimization, detection techniques, and therapeutic strategies, where they boost reaction selectivity and efficiency, enable precise identification and quantification of target substances, and enhance therapeutic effectiveness while minimizing adverse effects. Lastly, the prevailing challenges in the field and delineate potential avenues for future progress is encapsulated. This review will foster advancements in artificial enzyme technology and expand its applications.

Nanozymes and Their Potential Roles in the Origin of Life

The origin of life has long been a central scientific challenge, with various hypotheses proposed. The chemical evolution, which supposes that inorganic molecules can transform into organic molecules and subsequent primitive cells, laid the foundation for modern theories. Inorganic minerals are believed to play crucial catalytic roles in the process. However, the harsh reaction conditions of inorganic minerals hinder the accumulation of organic molecules, preventing the efficient transition from inorganic molecules to biomacromolecules. Given the inherent physicochemical properties and enzyme-like activities, this study proposes that nanozymes, nanomaterials with enzyme-like activities, act as efficient prebiotic catalysts in the origin of life. This hypothesis is based on the following: First, unlike traditional minerals, nanominerals can catalyze organic synthesis under milder conditions. Second, nanominerals can not only protect biomolecules from radiation damage but also catalyze polymerization reactions to form functional biomacromolecules and further lipid vesicles. More importantly, nanominerals are abundant in terrestrial and extraterrestrial environments. This perspective will systematically discuss the potential roles of nanozymes in the emergence of life based on the functions of minerals and the characteristics of nanozymes. We hope the research on nanozymes and the origin of life will bridge the gap between inorganic precursors and biomolecules under primitive environments.

One-Pot and Gram-Scale Synthesis of Fe-Based Nanozymes with Tunable O2 Activation Pathway and Specificity Between Associated Enzymatic Reactions

Nanozymes have recently gained attention for their low cost and high stability. However, unlike natural enzymes, they often exhibit multiple enzyme-like activities, complicating their use in selective bioassays. Since H2O2 and O2 are common substrates in these reactions, controlling their activation-and thus reaction specificity-is crucial. Recent advances in tuning the chemical state of cerium have enabled control over H2O2 activation pathways for tunable peroxidase/haloperoxidase-like activities. In contrast, the control of O2 activation on an element in oxidase/laccase nanozymes and the impact of its chemical state on these activities remains unexplored. Herein, a facile one-pot method is presented for the gram-scale synthesis of Fe-based nanozymes with tunable compositions of Fe3O4 and Fe3C by adjusting preparation temperatures. The Fe3O4-containing samples exhibit superior laccase-like activity, while the Fe3C-containing counterparts demonstrate better oxidase-like activity. This divergent O2 activation behavior is linked to their surface Fe species: the abundant reactive Fe2+ in Fe3O4 promotes laccase-like activity via Fe3+-superoxo formation, whereas metallic Fe in Fe3C facilitates OH radical generation for oxidase-like activity. Controlled O2 activation pathways in these Fe-based nanozymes demonstrate improved sensitivity in the corresponding biomolecule detection, which should inform the design of nanozymes with enhanced activity and specificity.

Frontiers in laccase nanozymes-enabled colorimetric sensing: A review

In recent years, nanozyme-based analytics have become popular. Among these, laccase nanozyme-based colorimetric sensors have emerged as simple and rapid colorimetric detection methods for various analytes, effectively addressing natural enzymes' stability and high-cost limitations. Laccase nanozymes are nanomaterials that exhibit inherent laccase enzyme-like activity. They can oxidize phenolic compounds to generate a coloured product, independently or with a chromogenic agent. This chromogenic reaction provides the basis for developing simple and robust colorimetric assays for various analytes, enabling rapid and point-of-need analytical decision-making in food safety, clinical diagnostics, and environmental monitoring. This review article provides a concise overview of laccase nanozymes, including their classification and catalytic mechanisms. The article mainly discusses colorimetric and dual-mode detection methods and outlines various strategies to enhance the colorimetric sensing performance of laccase nanozymes. Additionally, the article highlights future research directions that could further improve laccase nanozyme-enabled colorimetric sensing. We hope this work will enhance the field's understanding and help future researchers identify gaps in developing simple, low-cost colorimetric sensors.

Integrated Microneedles and Hydrogel Biosensor Platform: Toward a Diagnostic Device for Collection and Dual-Mode Sensing of Monkeypox Virus A29 Protein

The outbreak of the monkeypox epidemic underscores the importance of developing a rapid and sensitive virus detection technique. Microneedles (MNs) offer minimally invasive sampling capabilities, providing a solution for the development of integrated extraction and diagnostic portable devices. Here, we report an integrated MNs and hydrogel biosensor (IMHB) platform, composed of an electronic device, an MN patch, and a hydrogel patch. The IMHB allowed for specific extraction of monkeypox virus (MPXV) directly from lesional skin and virus detection in both electrochemical and colorimetric modes. A bifunctional signal probe 3,3',5,5'-tetramethylbenzidine (TMB) was loaded in a hydrogel patch, providing measurable signals for dual-mode sensing. Additionally, a control area was designed in this platform to collect blank samples from normal skin, enabling ratio analysis and quality control functions. This dual-mode ratiometric sensing strategy exhibited a wide range of 10-1000 ng/mL for MPXV A29 protein, with detection limits of 0.1632 and 0.3017 ng/mL for electrochemical and colorimetric assay, respectively. The developed IMHB platform provides a novel way for rapid on-site determination of MPXV, demonstrating the potential for quick intervention in the early stages of infectious diseases.

Self-reduction of gold@platinum bimetallic nanoparticles on Ti3C2Tx MXene nanoribbons coupled with hydrogel and smartphone technology for colorimetric detection of silver ions

In recent years, numerous colorimetric methods have been developed for the detection of silver ions (Ag+), yet there remains a need for a simple, sensitive, real-time and quantitative sensing platform. Herein, Ti3C2Tx MXene nanoribbons (Ti3C2TxNRs) were utilized as the carrier material, and gold@platinum (Au@Pt) bimetallic nanoparticles were decorated onto the Ti3C2TxNR surface, for the first time, via a facile self-reduction method. The resulting Au@Pt-Ti3C2TxNR nanohybrid exhibited excellent catalytic activity, facilitating the oxidation of 3,3',5,5'-tetramethylbenzidine, a colorless substrate, to generate a blue product (oxTMB), displaying prominent peroxidase-like activity. In the presence of Ag+, a remarkable inhibiting effect was observed on the catalytic activity of the Au@Pt-Ti3C2TxNR nanohybrids, effectively halting the generation of oxTMB. Based on this, the as-obtained Au@Pt-Ti3C2TxNR nanozyme was then utilized to develop a novel colorimetric sensing platform for Ag+ detection, with a low detection limit of 1.57 nM and a wide linear detection range from 5.0 nM to 9.0 μM. In addition, by combining the unique advantages of hydrogel materials and smartphone technology, a simple, real-time and quantitative platform for Ag+ monitoring was constructed, highlighting its potential for practical applications in Ag+ detection.

A Cardiac-Targeting and Anchoring Bimetallic Cluster Nanozyme Alleviates Chemotherapy-Induced Cardiac Ferroptosis and PANoptosis

Doxorubicin (DOX), a potent antineoplastic agent, is commonly associated with cardiotoxicity, necessitating the development of strategies to reduce its adverse effects on cardiac function. Previous research has demonstrated a strong correlation between DOX-induced cardiotoxicity and the activation of oxidative stress pathways. This work introduces a novel antioxidant therapeutic approach, utilizing libraries of tannic acid and N-acetyl-L-cysteine-protected bimetallic cluster nanozymes. Through extensive screening for antioxidative enzyme-like activity, an optimal bimetallic nanozyme (AuRu) is identified that possess remarkable antioxidant characteristics, mimicking catalase-like enzymes. Theoretical calculations reveal the surface interactions of the prepared nanozymes that simulate the hydrogen peroxide decomposition process, showing that these bimetallic nanozymes readily undergo OH⁻ adsorption and O₂ desorption. To enhance cardiac targeting, the atrial natriuretic peptide is conjugated to the AuRu nanozyme. These cardiac-targeted bimetallic cluster nanozymes, with their anchoring capability, effectively reduce DOX-induced cardiomyocyte ferroptosis and PANoptosis without compromising tumor treatment efficacy. Thus, the therapeutic approach demonstrates significant reductions in chemotherapy-induced cardiac cell death and improvements in cardiac function, accompanied by exceptional in vivo biocompatibility and stability. This study presents a promising avenue for preventing chemotherapy-induced cardiotoxicity, offering potential clinical benefits for cancer patients.

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.

Developing oxygen vacancy-rich CuMn2O4/carbon dots dual-function nanozymes via Chan-Lam coupling reaction for the colorimetric/fluorescent determination of D-penicillamine

Defect engineering is a promising approach to construct high performance nanozymes due to its ability to regulate their physical and chemical properties. However, how to construct defects to improve the activity of nanozymes remains a challenge. Herein, for the first time, the Chan-Lam coupling reaction is used to construct the oxygen vacancy (OV)-rich CuMn2O4/carbon dots (CDs) (OV-CuMn2O4/CDs) dual-function nanozymes with fluorescent (FL) and oxidase-like properties, via regulating the low-valent metal ions (Cu+ and Mn2+) and Ov contents in the spinel CuMn2O4 and in-situ growth of β-cyclodextrin (β-CD)-derived CDs. Expectedly, relative to CuMn2O4, the OV-CuMn2O4/CDs exhibited 35.8%, 8.5%, and 14.6% rise in the contents of Cu+, Mn2+ and Ov, respectively. Abundant Ov provides more O2 adsorption/activation sites, and the charge transfer between Ov and metal atoms increases the charge density around metal atoms. This produces more low-valent metals (like Cu+ and Mn2+) to promote the electron transfer from metal to O atoms and O-O bond cleavage. Thus, the oxidase-like activity of OV-CuMn2O4/CDs is 4.1 times that of CuMn2O4. Also, the in-situ growth of β-CD-derived carbon dots on CuMn2O4 endows OV-CuMn2O4/CDs selective target recognition. Thus, a sensitive and selective colorimetric and fluorescence dual-mode method was established for determining D-penicillamine (D-PA), with the limit of detection of 0.25 and 0.048 μM, respectively. The method was applied to D-PA determination in real samples. This work demonstrates the Chan-Lam coupling reaction can be used to construct high performance nanozymes for developing dual-mode sensor for the detection of targets.

Biomimetic Materials for Antibacterial Applications

The rise of antibiotic resistance poses a critical threat to global health, necessitating the development of novel antibacterial strategies to mitigate this growing challenge. Biomimetic materials, inspired by natural biological systems, have emerged as a promising solution in this context. These materials, by mimicking biological entities such as plants, animals, cells, viruses, and enzymes, offer innovative approaches to combat bacterial infections effectively. This review delves into the integration of biomimicry with materials science to develop antibacterial agents that are not only effective but also biocompatible and less likely to induce resistance. The study explores the design and function of various biomimetic antibacterial materials, highlighting their therapeutic potential in anti-infection applications. Further, the study provides a comprehensive summary of recent advancements in this field, illustrating how these materials have been engineered to enhance their efficacy and safety. The review also discusses the critical challenges facing the transition of these biomimetic strategies from the laboratory to clinical settings, such as scalability, cost-effectiveness, and long-term stability. Lastly, the study discusses the vast opportunities that biomimetic materials hold for the future of antibacterial therapy, suggesting that continued research and multidisciplinary collaboration will be essential to realize their full potential.

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.

A Fe/Zn Dual Single-Atom Nanozyme with High Peroxidase Activities for Detection of Penicillin G

Penicillin G (PG) is a common antibiotic, and its accumulation in the environment can pose a threat to the ecological system and ultimately impact human health. Nanozymes have emerged as highly stable enzyme mimics that can be utilized as sensors to achieve the sensitive detection of specific antibiotics. Herein, we report on a dual single-atom Fe/Zn nanozyme (DSAzyme) synthesized from Fe-imidazole as the guest and zeolite imidazole framework-8 as the host. The DSAzyme exhibits intriguing properties that mimic the activities of two natural enzymes: peroxidase and lactamase. Both activities are utilized for the design of a colorimetric sensor for the specific detection of PG: the peroxidase activity enables color generation from 3,3',5,5'-tetramethylbenzidine and H2O2, and the lactamase activity provides the recognition of PG. The nanozyme consists of many Fe-N4 and Zn-N4 site and mechanistic characterizations by experimental investigations and theoretical calculations identify Fe-N4 as the main active center for the peroxidase activity and Zn-N4 as the main binding site for PG. The sensor can achieve a limit of detection of 47 nM, is able to detect PG from real-life samples, remains fully functional after 8-month storage, and retain high activities after reuse for fives times. Taken together, our study provides a new approach to the detection of antibiotics in environmental samples.

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.

An integrated bipolar electrode with shared cathode for dual-mode detection and imaging of CEA

In this paper, we designed a novel shared cathode bipolar electrode chip based on Ohm 's law and successfully constructed a dual-mode dual-signal biosensor platform (DD-cBPE). The device integrates ELISA, ECL, and ECL imaging to achieve highly sensitive detection and visual imaging of carcinoembryonic antigen (CEA). The unique circuit structure of the device not only realizes the dual signal detection of the target, but also breaks the traditional signal amplification concept. The total resistance of the system is reduced by series-parallel connection of BPE, and the total current in the circuit is increased. In addition, Au@NiCo2O4@MnO2 nanozyme activity probe was introduced into the common cathode to enhance the conductivity of the material. At the same time, due to the excellent peroxidase (POD) activity of NiCo2O4@MnO2, the decomposition of H2O2 was accelerated, so that more electrons flowed to the BPE anode, and finally the dual amplification of the ECL signal was realized. The device affects the current in the circuit by regulating the concentration of the co-reactant TPrA, thereby affecting the resistance of the system. Finally, different luminescent reagents emit light at the same potential and the luminous efficiency is similar. In addition, the chip does not need external resistance regulation, which improves the sensitivity of the immunosensor and meets the needs of timely detection. It provides a new idea for the deviceization of bipolar electrodes and has broad application prospects in biosensors, clinical detection, and environmental monitoring.

Single-Atom Iridium Nanozyme-Based Persistent Luminescence Nanoparticles for Multimodal Imaging-Guided Combination Tumor Therapy

Persistent luminescence nanoparticles (PLNPs) can achieve autofluorescence-free afterglow imaging, while near-infrared (NIR) emission realizes deep tissue imaging. Nanozymes integrate the merits of nanomaterials and enzyme-mimicking activities with simple preparation. Here PLNPs are prepared of Zn1.2Ga1.6Ge0.2O4:Cr0.0075 with NIR emission at 700 nm. The PLNPs are then incubated with IrCl3 solution, and the nanoparticles are collected and annealed at 750 °C to obtain iridium@PLNPs. Iridium is observed on the PLNPs at the atomic level as a single-atom nanozyme with peroxidase-like catalytic activity, photothermal conversion, and computed tomography (CT) contrast capability. After coating with exosome membrane (EM), the Ir@PLNPs@EM composite exhibits long-lasting NIR luminescence, peroxidase-like catalytic activity, photothermal conversion, and CT contrast capability, with the targeting capability and biocompatibility from EM. Thus, NIR afterglow/photothermal/CT trimodal imaging-guided photothermal-chemodynamic combination therapy is realized as validated with the in vitro and in vivo inhibition of tumor growth, while toxicity and side effects are avoided as drug-free treatment. This work offers a promising avenue for advanced single-atom nanozyme@PLNPs to promote the development of nanozymes and PLNPs for clinical applications.

Cascade catalysis nanozyme for interfacial functionalization in combating implant infections associated with diabetes via sonodynamic therapy and adaptive immune activation

Innovative solutions are required for the intervention of implant associated infections (IAIs), especially for bone defect patients with chronic inflammatory diseases like diabetes mellitus (DM). The complex immune microenvironment of infections renders implants with direct antibacterial ability inadequate for the prolonged against of bacterial infections. Herein, a synergistic treatment strategy was presented that combined sonodynamic therapy (SDT) with adaptive immune modulation to treat IAIs in diabetes patients. A multifunctional coating was created on the surface of titanium (Ti) implants, consisting of manganese dioxide nanoflakes (MnO2 NFs) with cascade catalytic enzyme activity and a responsive degradable hydrogel containing a sonosensitizer. The reactive oxygen species (ROS) generated by glucose-hydrogen peroxide (H2O2) cascade catalysis and ultrasound (US) activation sonosensitizer helped kill bacteria and release bacterial antigens. Meanwhile, Mn2+ facilitated dendritic cells (DCs) maturation, enhancing antigen presentation to activate both cellular and humoral adaptive immunity against bacterial infections. This approach effectively eliminated bacteria in established diabetic IAIs model and activated systemic antibacterial immunity, providing long-term antibacterial protection. This study presents a non-antibiotic immunotherapeutic strategy for fighting IAIs in chronic diseases.

Promotes M1-polarization and diabetic wound healing using Prussian blue nanozymes

Long-term inflammation and impaired angiogenesis are the main reasons for the difficulty of diabetic wound healing. What to do to effectively promote vascular endothelial cell response and immune cell reprogramming is the key to diabetic skin healing. However, contemporary therapies cannot simultaneously coordinate the promotion of vascular endothelial cells and macrophage polarization, which leads to an increased rate of disability in patients with chronic diabetes. Therefore, we developed a method of repair composed of self-assembling Prussian blue nanoenzymes, which achieved synergistic support for the immune microenvironment, and also contributed to macrophage polarization in the tissue regeneration cycle, and enhanced vascular endothelial cell activity. The template hydrothermal synthesis PB-Zr nanoplatform was prepared and locally applied to wounds to accelerate wound healing through the synergistic effect of reactive oxygen species (ROS). PB-Zr significantly normalized the wound microenvironment, thereby inhibiting ROS production and inflammatory response, which may be because it inhibited the M1 polarization of macrophages in a rat model of wound. PB-Zr treatment significantly promoted the activity of vascular endothelial cells, which better promoted the growth and regeneration of other tissues in the body. The results confirmed the disease microenvironment of PB-Zr-mediated wound therapy and indicated its application in other inflammation-related diseases.

pH-activated metal-organic layer nanozyme for ferroptosis tumor therapy

Nanozymes have made great achievements in the research of tumor therapy. However, due to the complex tumor microenvironment, the catalytic activity and biosafety of nanozymes are limited. High catalytic efficiency is a relentless pursuit for the preparation of high-performance nanozymes. Dimensional reduction from 3D nanoscale metal-organic frameworks (nMOFs) to 2D nanoscale metal-organic layers (nMOLs) increases the encounters frequency of nanozymes and substrate, which facilitates the diffusion of reactive oxygen species (ROS) from nMOLs, thus significantly improving the effectiveness of chemodynamic therapy. In this study, He@Ce-BTC nMOF and He@Ce-BTB nMOL based on Ce6 SBUs were synthesized by solvothermal reaction. Compared with the 3D nMOFs, the 2D nanozymes He@Ce-BTB nMOL possessed enhanced ROS catalytic efficiency, were able to be activated by the tumor acidic microenvironment with the polymerase mimetic activities (CAT, POD, GSH-OXD) that enhances the lipid peroxidation process and accelerates the process of ferroptosis thereby killing tumor cells. In addition, He@Ce-BTB does not affect normal tissue cells, thus avoiding diffusion-induced side effects. He@Ce-BTB has shown excellent therapeutic effects in vitro and in vivo, which indicates its potential for clinical application, and is expected to become a new generation of drugs for the treatment of tumors.

Tailoring metal oxide nanozymes for biomedical applications: trends, limitations, and perceptions

Nanomaterials with enzyme-like properties are known as 'nanozymes'. Nanozymes are preferred over natural enzymes due to their nanoscale characteristics and ease of tailoring of their physicochemical properties such as size, structure, composition, surface chemistry, crystal planes, oxygen vacancy, and surface valence state. Interestingly, nanozymes can be precisely controlled to improve their catalytic ability, stability, and specificity which is unattainable by natural enzymes. Therefore, tailor-made nanozymes are being favored over natural enzymes for a range of potential applications and better prospects. In this context, metal oxide nanoparticles with nanozyme-mimicking characteristics are exclusively being used in biomedical sectors and opening new avenues for future nanomedicine. Realising the importance of this emerging area, here, we discuss the mechanistic actions of metal oxide nanozymes along with their key characteristics which affect their enzymatic actions. Further, in this critical review, the recent progress towards the development of point-of-care (POC) diagnostic devices, cancer therapy, drug delivery, advanced antimicrobials/antibiofilm, dental caries, neurodegenerative diseases, and wound healing potential of metal oxide nanozymes is deliberated. The advantages of employing metal oxide nanozymes, their potential limitations in terms of nanotoxicity, and possible prospects for biomedical applications are also discussed with future recommendations.

Dual-electrode signal amplification self-powered biosensing platform based on nanozyme boosting target-induced DNA nanospace array for ultrasensitive detection of sugarcane Pokkah Boeng disease pathogenic bacteria

Sugarcane is a crop with significant economic importance worldwide. However, pokkah boeng disease poses a serious threat to its production and the sustainable development. There is a pressing necessity for precise and portable detection methods. We develop a dual-electrode signal amplification biosensing platform, for highly sensitive detection of sugarcane pokkah boeng disease pathogenic bacteria. This innovative platform integrates highly catalytic AuNPs/Mn3O4 nanozymes with N-GDY, along with a target-induced development of DNA nanostructure arrays. AuNPs/N-GDY serves as dual electrode substrates, and AuNPs/Mn3O4 nanozymes are surface-loaded as the bioanode. The biocathode is constructed by introducing DNA nanospace arrays onto the electrode through target-induced methods. [Ru(NH3)6]3+ is embedded into the nucleic acid double-helix scaffold via electrostatic adsorption, generating an EOCV signal that is strongly correlated with the target concentration. To further enhance sensitivity, the detection platform is combined with a capacitor to amplify the detection signal, utilizing its high power density, which results in a 22.5-fold increase in sensitivity. The method offers a linear detection range of 0.0001 to 10,000 pM and an detection limit of 32.5 aM (S/N = 3). This method supplies a novel approach for real-time monitoring and competent oversight of pokkah boeng disease pathogenic bacteria.

Doughnut-shaped bimetallic Cu-Zn-MOF with peroxidase-like activity for colorimetric detection of glucose and antibacterial applications

Metal-organic frameworks (MOFs), especially bimetallic MOFs, have attracted widespread attention for simulating the structure and function of natural enzymes. In this study, different morphologies of bimetallic Cu-Zn-MOF with different peroxidase (POD)-like activities were prepared by simply controlling the molar ratio of Cu2+ and Zn2+. Among them, the doughnut-shaped Cu9-Zn1-MOF exhibited the largest POD-like activity. Cu9-Zn1-MOF was combined with glucose oxidase to construct a sensitive and selective glucose colorimetric biosensor with a linear detection range of 10-300 μM and a detection limit of 7.1 μm. Furthermore, Cu9-Zn1-MOF can efficiently convert hydrogen peroxide (H2O2) into hydroxyl radicals that effectively kill both gram-negative and gram-positive bacteria at low H2O2 level. The results of this study may promote the synthesis of bimetallic MOFs and broaden their applications in the biomedical field.

Recent Advances in Nanozyme-Based Sensing Technology for Antioxidant Detection

Antioxidants are substances that have the ability to resist or delay oxidative damage. Antioxidants can be used not only for the diagnosis and prevention of vascular diseases, but also for food preservation and industrial production. However, due to the excessive use of antioxidants, it can cause environmental pollution and endanger human health. It can be seen that the development of antioxidant detection technology is important for environment/health maintenance. It is found that traditional detection methods, including high performance liquid chromatography, gas chromatography, etc., have shortcomings such as cumbersome operation and high cost. In contrast, the nanozyme-based detection method features advantages of low cost, simple operation, and rapidity, which has been widely used in the detection of various substances such as glucose and antioxidants. This article focuses on the latest research progress of nanozymes for antioxidant detection. Nanozymes for antioxidant detection are classified according to enzyme-like types. Different types of nanozyme-based sensing strategies and detection devices are summarized. Based on the summary and analysis, one can find that the development of commercial nanozyme-based devices for the practical detection of antioxidants is still challenging. Some emerging technologies (such as artificial intelligence) should be fully utilized to improve the detection sensitivity and accuracy. This article aims to emphasize the application prospects of nanozymes in antioxidant detection and to provide new ideas and inspiration for the development of detection methods.