Synthesis of Amorphous/Crystalline Hetero-Phase Nanozymes With Peroxidase-Like Activity by Coordination-Driven Self-Assembly for Biosensors

Nanozymes and amorphous nanomaterials attract great attention owing to their extraordinary properties. However, the requirements for special synthesis conditions become the bottleneck of their development. Herein, a new strategy involving the DNA-based coordination-driven self-assembly is reported for the synthesis of a novel amorphous/crystalline hetero-phase nanozyme (Fe-DNA). For the synthesis of both nanozymes and amorphous materials, this strategy is simple and controllable, avoiding the traditionally employed harsh conditions. Benefitting from the amorphous structure and the superior physicochemical properties, the synthesized Fe-DNA nanozyme is subsequently found to exhibit a smaller Michaelis constant value for hydrogen peroxide (H₂O₂) (0.81 mm ) than that of horseradish peroxidase (HRP) (3.70 mm ), demonstrating the stronger affinity of the Fe-DNA nanozyme toward H₂O₂. The Fe-DNA nanozyme also shows significant peroxidase-like activity but only negligible oxidase-like activity, a characteristic which releases the corresponding assay system from oxygen interference, thereby improving the performance of the nanozyme-based sensing platform. In addition, compared with other nanozymes, the novel Fe-DNA nanozyme is degradable via phosphate; thus, mitigating potential environmental threat. This work provides novel amorphous/crystalline hetero-phase nanozymes and opens a new avenue for the design of amorphous nanomaterials and nanozymes.     

Integrating Incompatible Nanozyme-Catalyzed Reactions for Diabetic Wound Healing

Multi-nanozymes are widely applied in disease treatment, biosensing, and other fields. However, most current multi-nanozyme systems exhibit only moderate activity since reaction microenvironments of different nanozyme are often distinct or even incompatible. Conventional assemble strategies are inapplicable for designing multi-nanozymes consisting of incompatible nanozymes. Herein, a versatile fiber-based compartmentalization strategy is developed to construct multi-nanozyme system capable of simultaneously performing incompatible reactions. In this system, the incompatible nanozymes are spatially distributed in distinct compartmentalized fibers, where different microenvironments can be tailored by controlling the doping reagent, endowing each nanozymes with the preferential microenvironments to exhibit their highest activity. As a proof of concept, pH-incompatible peroxidase-like and catalase-like catalytic reactions are tested to verify the feasibility of this strategy. By doping with benzoic acid in the desired location, the two pH-incompatible nanozymes can work simultaneously without interference. Further, it is demonstrated that the oxygen supply and antimicrobial power of the integrated platform can be applied for accelerating diabetic wound healing. It is hoped that this work provides a way to integrate incompatible nanozyme and broadens the application potential of multi-nanozymes.     

Chiral Ruthenium Nanozymes with Self-Cascade Reaction Driven the NO Generation Induced Macrophage M1 Polarization Realizing the Lung Cancer “Cocktail Therapy”

Macrophages as the main cause of cancer immunosuppression, how to effectively induce macrophage M1 polarization remain the major challenge in lung cancer therapy. Herein, inspired by endogenous reactions, a strategy is proposed to coactivate macrophage M1 polarization by reactive oxygen species (ROS) and nitric oxide (NO) with self-autocatalytic cascade reaction. To enhance the generation of NO and ROS, NO Precursor-Arginine as capping agents for inducing synthesis two kinds of chiral ruthenium nanozyme (D/L-Arginine@Ru). Under the properties of Ru nanozymes through synchronously mimicking the activity of oxidase and nitric oxide synthase (NOS), chiral Ru nanozyme can rapidly generate ¹O₂ and O₂ at first stage, and then catalyze Arginine to produce sufficient NO, thus enhance macrophage M1 polarization to reverse tumor immunosuppression. Moreover, combination the antitumor activity of ¹O₂, NO, the chiral Ru nanozymes realize the “cocktail therapy” by inducing tumor cell apoptosis as well as ferroptosis. In addition, the chirality influences the bioactivity of Ru nanozymes that L-Arginine@Ru shows the better therapeutic effect with stronger catalytic activity and natural homology. It is hoped the high performance of chiral Ru nanozyme with “cocktail therapy” is an effective therapeutic reagent and can provide a feasible treatment strategy for tumor catalytic therapy.     

In Situ Fabrication of Ultrasmall Gold Nanoparticles/2D MOFs Hybrid as Nanozyme for Antibacterial Therapy

As one of the common reactive oxygen species, H₂O₂ has been widely used for combating pathogenic bacterial infections. However, the high dosage of H₂O₂ can induce undesired damages to normal tissues and delay wound healing. In this regard, peroxidase‐like nanomaterials serve as promising nanozymes, thanks to their positive promotion toward the antibacterial performance of H₂O₂, while avoiding the toxicity caused by the high concentrations of H₂O₂. In this work, ultrasmall Au nanoparticles (UsAuNPs) are grown on ultrathin 2D metal–organic frameworks (MOFs) via in situ reduction. The formed UsAuNPs/MOFs hybrid features both the advantages of UsAuNPs and ultrathin 2D MOFs, displaying a remarkable peroxidase‐like activity toward H₂O₂ decomposition into toxic hydroxyl radicals (·OH). Results show that the as‐prepared UsAuNPs/MOFs nanozyme exhibits excellent antibacterial properties against both Gram‐negative (Escherichia coli) and Gram‐positive (Staphylococcus aureus) bacteria with the assistance of a low dosage of H₂O₂. Animal experiments indicate that this hybrid material can effectively facilitate wound healing with good biocompatibility. This study reveals the promising potential of a hybrid nanozyme for antibacterial therapy and holds great promise for future clinical applications.     

RhRu Alloy-Anchored MXene Nanozyme for Synergistic Osteosarcoma Therapy

Noble metal nanozymes hold promise in cancer therapy due to adjustable enzyme-like activities, unique physicochemical properties, etc. But catalytic activities of monometallic nanozyme are confined. In this study, 2D titanium carbide (Ti₃C₂T_x)-supported RhRu alloy nanoclusters (RhRu/Ti₃C₂T_x) are prepared by a hydrothermal method and utilized for synergistic therapy of chemodynamic therapy (CDT), photodynamic therapy (PDT), and photothermal therapy (PTT) on osteosarcoma. The nanoclusters are small in size (3.6 nm), uniform in distribution, and have excellent catalase (CAT) and peroxidase (POD)-like activities. Density functional theory calculations show that there is a significant electron transfer interaction between RhRu and Ti₃C₂T_x, which has strong adsorption to H₂O₂ and is beneficial to enhance the enzyme-like activity. Furthermore, RhRu/Ti₃C₂T_x nanozyme acts as both PTT agent for converting light into heat, and photosensitizer for catalyzing O₂ to ¹O₂. With the NIR-reinforced POD- and CAT-like activity, excellent photothermal and photodynamic performance, the synergistic CDT/PDT/PTT effect of RhRu/Ti₃C₂T_x on osteosarcoma is verified by in vitro and in vivo experiments. This study is expected to provide a new research direction for the treatment of osteosarcoma and other tumors.     

An Organelle-Specific Nanozyme for Diabetes Care in Genetically or Diet-Induced Models

The development of nanozymes has made active impact in diagnosis and therapeutics. However, understanding of the full effects of these nanozymes on biochemical pathways and metabolic homeostasis remains elusive. Here, it is found that iron oxide nanoparticles (Fe₃O₄ NPs), a type of well-established nanozyme, can locally regulate the energy sensor adenosine 5′-monophosphate-activated protein kinase (AMPK) via their peroxidase-like activity in the acidic lysosomal compartment, thereby promoting glucose metabolism and insulin response. Fe₃O₄ NPs induce AMPK activation and enhance glucose uptake in a variety of metabolically active cells as well as in insulin resistant cell models. Dietary Fe₃O₄ NPs display therapeutic effects on hyperglycemia and hyperinsulinemia in Drosophila models of diabetes induced by genetic manipulation or high-sugar diet. More importantly, intraperitoneal administration of Fe₃O₄ NPs stimulates AMPK activities in metabolic tissues, reduces blood glucose levels, and improves glucose tolerance and insulin sensitivity in diabetic ob/ob mice. The study reveals intrinsic organelle-specific properties of Fe₃O₄ NPs in AMPK activation, glycemic control, and insulin-resistance improvement, suggesting their potential efficacy in diabetes care.     

Oxidase‐Like Fe‐N‐C Single‐Atom Nanozymes for the Detection of Acetylcholinesterase Activity

Single‐atom catalysts (SACs) have attracted extensive attention in the catalysis field because of their remarkable catalytic activity, gratifying stability, excellent selectivity, and 100% atom utilization. With atomically dispersed metal active sites, Fe‐N‐C SACs can mimic oxidase by activating O₂ into reactive oxygen species, O₂^?? radicals. Taking advantages of this property, single‐atom nanozymes (SAzymes) can become a great impetus to develop novel biosensors. Herein, the performance of Fe‐N‐C SACs as oxidase‐like nanozymes is explored. Besides, the Fe‐N‐C SAzymes are applied in biosensor areas to evaluate the activity of acetylcholinesterase based on the inhibition toward nanozyme activity by thiols. Moreover, this SAzymes‐based biosensor is further used for monitoring the amounts of organophosphorus compounds.     

Peroxidase-Like FeCoZn Triple-Atom Catalyst-Based Electronic Tongue for Colorimetric Discrimination of Food Preservatives

Recently, single-atom catalysts are attracting much attention in sensor field due to their remarkable peroxidase- or oxidase-like activities. Herein, peroxidase-like FeCoZn triple-atom catalyst supported on S- and N-doped carbon derived from ZIF-8 (FeCoZn-TAC/SNC) serves as a proof-of-concept nanozyme. In this paper, a dual-channel nanozyme-based colorimetric sensor array is presented for identifying seven preservatives in food. Further experiments reveal that the peroxidase-like activity of the FeCoZn TAzyme enables it to catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) and o-phenylenediamine (OPD) in the presence of H₂O₂, yielding the blue oxTMB and yellow oxOPD, respectively. However, food preservatives are adsorbed on the nanozyme surface through π–π stacking interaction and hydrogen bond, and the reduction in catalytic activity of FeCoZn TAzyme causes differential colorimetric signal variations, which provide unique “fingerprints” for each food preservative.     

Photothermal-Switched Single-Atom Nanozyme Specificity for Pretreatment and Sensing

Various applications lead to the requirement of nanozymes with either specific activity or multiple enzyme-like activities. To this end, intelligent nanozymes with freely switching specificity abilities hold great promise to adapt to complicated and changeable practical conditions. Herein, a nitrogen-doped carbon-supported copper single-atom nanozyme (named Cu SA/NC) with switchable specificity is reported. Atomically dispersed active sites endow Cu SA/NC with specific peroxidase-like activity at room temperature. Furthermore, the intrinsic photothermal conversion ability of Cu SA/NC enables the specificity switch by additional laser irradiation, where photothermal-induced temperature elevation triggers the expression of oxidase-like and catalase-like activity of Cu SA/NC. For further applications in practice, a pretreatment-and-sensing integration kit (PSIK) is constructed, where Cu SA/NC can successively achieve sample pretreatment and sensitive detection by switching from multi-activity mode to specific-activity mode. This study sets the foundation for nanozymes with switchable specificity and broadens the application scope in point-of-care testing.     

Immunomodulation-Enhanced Nanozyme-Based Tumor Catalytic Therapy

Nanozyme-based tumor catalytic therapy has attracted widespread attention in recent years. However, its therapeutic outcomes are diminished by many factors in the tumor microenvironment (TME), such as insufficient endogenous hydrogen peroxide (H₂O₂) concentration, hypoxia, and immunosuppressive microenvironment. Herein, an immunomodulation-enhanced nanozyme-based tumor catalytic therapy strategy is first proposed to achieve the synergism between nanozymes and TME regulation. TGF-β inhibitor (TI)-loaded PEGylated iron manganese silicate nanoparticles (IMSN) (named as IMSN-PEG-TI) are constructed to trigger the therapeutic modality. The results show that IMSN nanozyme exhibits both intrinsic peroxidase-like and catalase-like activities under acidic TME, which can decompose H₂O₂ into hydroxyl radicals (•OH) and oxygen (O₂), respectively. Besides, it is demonstrated that both IMSN and TI can regulate the tumor immune microenvironment, resulting in macrophage polarization from M2 to M1, and thus inducing the regeneration of H₂O₂, which can promote catalytic activities of IMSN nanozyme. The potent antitumor effect of IMSN-PEG-TI is proved by in vitro multicellular tumor spheroids (MCTS) and in vivo CT26-tumor-bearing mice models. It is believed that the immunomodulation-enhanced nanozyme-based tumor treatment strategy is a promising tool to kill cancer cells.     

GSH-Depleted Nanozymes with Hyperthermia-Enhanced Dual Enzyme-Mimic Activities for Tumor Nanocatalytic Therapy

Nanocatalytic therapy, using artificial nanoscale enzyme mimics (nanozymes), is an emerging technology for therapeutic treatment of various malignant tumors. However, the relatively deficient catalytic activity of nanozymes in the tumor microenvironment (TME) restrains their biomedical applications. Here, a versatile and bacteria-like PEG/Ce-Bi@DMSN nanozyme is developed by coating uniform Bi₂S₃ nanorods (NRs) with dendritic mesoporous silica (Bi₂S₃@DMSN) and then decorating ultrasmall ceria nanozymes into the large mesopores of Bi₂S₃@DMSN. The nanozymes exhibit dual enzyme-mimic catalytic activities (peroxidase-mimic and catalase-mimic) under acidic conditions that can regulate the TME, that is, simultaneously elevate oxidative stress and relieve hypoxia. In addition, the nanozymes can effectively consume the overexpressed glutathione (GSH) through redox reaction. Photothermal therapy (PTT) is introduced to synergistically improve the dual enzyme-mimicking catalytic activities and depletion of the overexpressed GSH in the tumors by photonic hyperthermia. This is achieved by taking advantage of the desirable light absorbance in the second near-infrared (NIR-II) window of the PEG/Ce-Bi@DMSN nanozymes. Subsequently the reactive oxygen species (ROS)-mediated therapeutic efficiency is significantly improved. Therefore, this study provides a proof of concept of hyperthermia-augmented multi-enzymatic activities of nanozymes for tumor ablation.     

Surface modification of nanozymes

Nanoparticles and proteins are similar in a number of aspects,and using nanoparticles to mimic the catalytic function of enzymes is an interesting yet challenging task.Impressive developments have been made over the past two decades on this front.The term nanozyme was coined to refer to nanoparticlebased enzyme mimics.To date,many different types of nanozymes have been reported to catalyze a broad range of reactions for chemical,analytical,and biomedical applications.Since chemical reactions happen mainly on the surface of nanozymes,an interesting aspect for investigation is surface modification.In this review,we summarize three types of nanozyme materials catalyzing various reactions with a focus on their surface chemistry.For metal oxides,cerium oxide and iron oxide are discussed as they are the most extensively studied.Then,gold nanoparticles and graphene oxide are reviewed to represent metallic and carbon nanomaterials,respectively.Types of modifications include ions,small molecules,and polymers mainly by physisorption,while in a few cases,covalent modifications were also employed.The functional aspect of such modification is to improve catalytic activity,substrate specificity,and stability.Future perspectives of this field are speculated at the end of this review.     

High‐Performance Integrated Enzyme Cascade Bioplatform Based on Protein–BiPt Nanochain@Graphene Oxide Hybrid Guided One‐Pot Self‐Assembly Strategy

Nanozymes provide new opportunities for facilitating next generation artificial enzyme cascade platforms. However, the fabrication of high‐performance integrated artificial enzyme cascade (IAEC) bioplatforms based on nanozymes remains a great challenge. A facile and effective self‐assembly strategy for constructing an IAEC system based on an inorganic/protein hybrid nanozyme, β‐casein‐BiPt nanochain@GO (CA‐BiPtNC@GO) nanohybrid with unique physicochemical surface properties and hierarchical structures, is introduced here. Due to the synergetic effect of the protein, GO, and Bi³⁺, the hybrid acts as highly adaptable building blocks to immobilize natural enzymes directly and noncovalently without the loss of enzyme activity. Simultaneously, the CA‐BiPtNC@GO nanohybrid exhibits outstanding peroxidase‐mimicking activity and works well with natural oxidases, resulting in prominent activity in catalyzing cascade reactions. As a result, the proposed IAEC bioplatform exhibits excellent sensitivity with a wide linear range of 0.5 × 10^‐6 to 100 × 10^‐6 m and a detection limit of 0.05 × 10^‐6 m for glucose. Meticulous design of ingenious hierarchically nanostructured nanozymes with unique physicochemical surface properties can provide a facile and efficient way to immobilize and stabilize nature enzymes using self‐assembly instead of chemical processes, and fill the gap in developing robust nanozyme–triggered IAEC systems with applications in the environment, sensing, and synthetic biology.     

Defect engineering in nanozymes

Due to the high stability, various synthesis strategies, low cost, and tunable performance, nanozymes have gained much attention as the replacement of natural enzymes. To widen the application, highly active, specific, and robust nanozymes are in need. Recently, defects in nanomaterials have been verified to play a significant role in enhancing catalytic performances. Therefore, the marriage between defect engineering and nanozymes is expected to spark new possibilities. In this review, defect engineering strategies in nanozymes are summarized and the close relationships between defects and nanozyme properties are highlighted. It is anticipated that defect engineering will bring new opportunities to the evolving field of nanozymes.     

Rapid and Superior Bacteria Killing of Carbon Quantum Dots/ZnO Decorated Injectable Folic Acid‐Conjugated PDA Hydrogel through Dual‐Light Triggered ROS and Membrane Permeability

One of the most difficult challenges in the biomedical field is bacterial infection, which causes tremendous harm to human health. In this work, an injectable hydrogel is synthesized through rapid assembly of dopamine (DA) and folic acid (FA) cross‐linked by transition metal ions (TMIs, i.e., Zn²⁺), which was named as DFT‐hydrogel. Both the two carboxyl groups in the FA molecule and catechol in polydopamine (PDA) easily chelates Zn²⁺ to form metal–ligand coordination, thereby allowing this injectable hydrogel to match the shapes of wounds. In addition, PDA in the hydrogel coated around carbon quantum dot‐decorated ZnO (C/ZnO) nanoparticles (NPs) to rapidly generate reactive oxygen species (ROS) and heat under illumination with 660 and 808 nm light, endows this hybrid hydrogel with great antibacterial efficacy against Staphylococcus aureus (S. aureus, typical Gram‐positive bacteria) and Escherichia coli (E. coli, typical Gram‐negative bacteria). The antibacterial efficacy of the prepared DFT‐C/ZnO‐hydrogel against S. aureus and E. coli under dual‐light irradiation is 99.9%. Importantly, the hydrogels release zinc ions over 12 days, resulting in a sustained antimicrobial effect and promoted fibroblast growth. Thus, this hybrid hydrogel exhibits great potential for the reconstruction of bacteria‐infected tissues, especially exposed wounds.     

Polyoxometalate-based nanozyme: Design of a multifunctional enzyme for multi-faceted treatment of Alzheimer’s disease

Proteolytic degradation of amyloid-β (Aβ) aggregates and clearance of Aβ-induced reactive oxygen species (ROS) have received significant attention for the treatment of Alzheimer’s disease (AD). However, it is difficult, and often unfeasible, to directly upregulate or transport intracellular native enzymes. More importantly, penetration of the blood-brain barrier (BBB) has presented a major impediment. Herein, we report on the rational design of a polyoxometalatebased nanozyme with both protease-like activity for depleting Aβ aggregates, and superoxide dismutase (SOD)-like activity for scavenging Aβ-mediated ROS. Furthermore, this nanozyme acts as a metal chelator to remove Cu from Cu-induced Aβ oligomers. More intriguingly, the nanozyme can cross the BBB and exhibits low toxicity. This work provides new insights into the design and synthesis of inorganic nanozymes as multifunctional therapeutic agents in the treatment of AD.

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Tumor associated macrophages reprogrammed by targeted bifunctional bioorthogonal nanozymes for enhanced tumor immunotherapy

Cancer immunotherapy has emerged as a promising cancer treatment. However, its efficacy is often limited by the immunosuppressive tumor microenvironment (TME) in solid tumors. Herein, a new strategy has been presented by using bioorthogonal chemistry to reprogram TME. We designed a bifunctional mannose (Man) vector decorated palladium bioorthogonal nanozyme for in-situ synthesis of histone deacetylase inhibitor (HDACi) vorinostat (FDA approved) with the ability to remodel tumor microenvironment. To the best of our knowledge, this is the first report to use a bioorthogonal nanozyme for cancer immunotherapy. In particular, the nanozyme could preferentially accumulate in M2 macrophages (termed M2Φ) to achieve local M2 re-education, which effectively avoided unnecessary inflammation in normal tissues. Moreover, vorinostat-induced TME reprogramming was synergistic with peroxidase-like activity of the nanozyme, and achieved enhanced tumor synergistic immunotherapy. In colon cancer (CT26)-tumor-bearing BALB/c mice, the nanozyme demonstrated macrophages polarization targeting M2Φ and activation of innate immune system, resulting in significantly enhanced tumor growth inhibition. Our work not only provides a new effective way to reprogram TME in vivo, but also shed light on the design of novel bioorthogonal nanozymes for cancer immunotherapy.     

Photoactivated Trifunctional Platinum Nanobiotics for Precise Synergism of Multiple Antibacterial Modes

Integrating multiple strategies of antibacterial mechanisms into one has been proven to have tremendous promise for improving antimicrobial efficiency. Hence, dual‐valent platinum nanoparticles (dvPtNPs) with a zero‐valent platinum core (Pt⁰) and bi‐valent platinum shell (Pt²⁺ ions), combining photothermal and photodynamic therapy, together with “chemotherapy,” emerge as spatiotemporally light‐activatable platinum nano‐antibiotics. Under near‐infrared (NIR) exposure, the multiple antibacterial modes of dvPtNPs are triggered. The Pt⁰ core reveals significant hyperthermia via effective photothermal conversion while an immediate release of chemotherapeutic Pt²⁺ ions occurs through hyperthermia‐initiated destabilization of metallic interactions, together with reactive oxygen species (ROS) level increase, thereby resulting in synergistic antibacterial effects. The precise cooperative effects between photothermal, photodynamic, and Pt²⁺ antibacterial effects are achieved on both Gram‐negative Escherichia coli and Gram‐positive methicillin‐resistant Staphylococcus aureus, where bacterial viability and colony‐forming units are significantly reduced. Moreover, similar results are observed in mice subcutaneous abscess models. Significantly, after NIR treatment, dvPtNP exhibits a more robust bacteria‐killing efficiency than other PtNP groups, owing to its integration of dramatic damage to the bacterial membrane and DNA, and alteration to ATP and ROS metabolism. This study broadens the avenues for designing and synthesizing antibacterial materials with higher efficiency.     

Magnetic nanoparticles/graphitic carbon nanostructures composites: Excellent magnetic separable adsorbents for precious metals from aqueous solutions

A facile, low-cost and high-yield route was used for synthesis of magnetic nanoparticles/graphitic carbon nanostructures (MNPs/GCNs) adsorbents with adjustable GCNs structues, in which the cheap ion-exchanged resins and iron salts were adopted as the precursors. The synthesized MNPs/GCNs composites could be used as effective mobile adsorbents for removal of precious metal ions (Ag⁺ and Au³⁺). The adsorption quantity of the adsorbents for Ag⁺ and Au³⁺ ions is up to 7.88 mg/g and 7.92 mg/g, respectively, which is much higher than that of activated carbon. Notably, the adsorbents could be easily separated from solution with a commercial magnet due to the magnetic property, which is very beneficial to their practical application. The kinetics for Ag⁺ and Au³⁺ ions adsorption on MNPs/GCNs composites followed the pseudo-second-order kinetics. The XPS analyses demonstrated that the adsorbed Ag⁺ and Au³⁺ ions exsited in the form of the zero valence state silver and gold, respectively.