Copper single-atom catalysts with photothermal performance and enhanced nanozyme activity for bacteria-infected wound therapy

Inactivation of antibiotic resistant bacteria by nitrogen-doped carbon quantum dots through spontaneous generation of intracellular and extracellular reactive oxygen species

The widespread antibiotic resistance has called for alternative antimicrobial agents. Carbon nanomaterials, especially carbon quantum dots (CQDs), may be promising alternatives due to their desirable physicochemical properties and potential antimicrobial activity, but their antimicrobial mechanism remains to be investigated. In this study, nitrogen-doped carbon quantum dots (N-CQDs) were synthesized to inactivate antibiotic-resistant bacteria and treat bacterial keratitis. N-CQDs synthesized via a facile hydrothermal approach displayed a uniform particle size of less than 10 nm, featuring a graphitic carbon structure and functional groups including -OH and -NH2. The N-CQDs demonstrated antimicrobial activity against Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus, which was both dose- and time-dependent, reducing the survival rate to below 1 %. The antimicrobial activity was confirmed by live/dead staining. In in vivo studies, the N-CQDs were more efficient in treating drug-resistant bacterial keratitis and reducing corneal damage compared to the common antibiotic levofloxacin. The N-CQDs were shown to generate intracellular and extracellular ROS, which potentially caused oxidative stress, membrane disruption, and cell death. This antimicrobial mechanism was supported by scanning and transmission electron microscopy, significant regulation of genes related to oxidative stress, and increased protein and lactate dehydrogenase leakage. This study has provided insight into the development, application, and mechanism of N-CQDs in antimicrobial applications.

Photodynamic and photothermal bacteria targeting nanosystems for synergistically combating bacteria and biofilms

The escalating hazards posed by bacterial infections underscore the imperative for pioneering advancements in next-generation antibacterial modalities and treatments. Present therapeutic methodologies are frequently impeded by the constraints of insufficient biofilm infiltration and the absence of precision in pathogen-specific targeting. In this current study, we have used chlorin e6 (Ce6), zeolitic imidazolate framework-8 (ZIF-8), polydopamine (PDA), and UBI peptide to formulate an innovative nanosystem meticulously engineered to confront bacterial infections and effectually dismantle biofilm architectures through the concerted mechanism of photodynamic therapy (PDT)/photothermal therapy (PTT) therapies, including in-depth research, especially for oral bacteria and oral biofilm. Ce6@ZIF-8-PDA/UBI nanosystem, with effective adhesion and bacteria-targeting, affords a nuanced bacterial targeting strategy and augments penetration depth into oral biofilm matrices. The Ce6@ZIF-8-PDA/UBI nanosystem potentiated bacterial binding and aggregation. Upon exposure to red-light (RL) irradiation, Ce6@ZIF-8-PDA/UBI showed excellent antibacterial effect on S. aureus, E. coli, F. nucleatum, and P. gingivalis and exceptional light-driven antibiofilm activity to P. gingivalis biofilm, which was a result of the efficient bacterial localization mediated by PDA/UBI, as well as the PDT/PTT facilitated by Ce6/PDA interactions. Collectively, these versatile nanoplatforms augur a promising and strategic avenue for controlling infection and biofilm, thereby holding significant potential for future integration into clinical paradigms. The original application of the developed nanosystem in oral biofilms also provides a new strategy for effective oral infection treatment.

Copper-Based Nanozymes: Potential Therapies for Infectious Wounds

Bacterial infections are a significant obstacle to the healing of acute and chronic wounds, such as diabetic ulcers and burn injuries. Traditional antibiotics are the primary treatment for bacterial infections, but they present issues such as antibiotic resistance, limited efficacy, and potential side effects. This challenge leads to the exploration of nanozymes as alternative therapeutic agents. Nanozymes are nanomaterials with enzyme-like activities. Owing to their low production costs, high stability, scalability, and multifunctionality, nanozymes have emerged as a prominent focus in antimicrobial research. Among various types of nanozymes, metal-based nanozymes offer several benefits, including broad-spectrum antimicrobial activity and robust catalytic properties. Specifically, copper-based nanozymes (CuNZs) have shown considerable potential in promoting wound healing. They exhibit strong antimicrobial effects, reduce inflammation, and enhance tissue regeneration, making them highly advantageous for use in wound care. This review describes the dual functions of CuNZs in combating infection and facilitating wound repair. Recent advancements in the design and synthesis of CuNZs, evaluating their antimicrobial efficacy, healing promotion, and biosafety both in vitro and in vivo on the basis of their core components, are critically important.

Catalytic Biomaterials-Activated In Situ Chemical Reactions: Strategic Modulation and Enhanced Disease Treatment

Chemical reactions underpin biological processes, and imbalances in critical biochemical pathways within organisms can lead to the onset of severe diseases. Within this context, the emerging field of "Nanocatalytic Medicine" leverages nanomaterials as catalysts to modulate fundamental chemical reactions specific to the microenvironments of diseases. This approach is designed to facilitate the targeted synthesis and localized accumulation of therapeutic agents, thus enhancing treatment efficacy and precision while simultaneously reducing systemic side effects. The effectiveness of these nanocatalytic strategies critically hinges on a profound understanding of chemical kinetics and the intricate interplay of reactions within particular pathological microenvironments to ensure targeted and effective catalytic actions. This review methodically explores in situ catalytic reactions and their associated biomaterials, emphasizing regulatory strategies that control therapeutic responses. Furthermore, the discussion encapsulates the crucial elements-reactants, catalysts, and reaction conditions/environments-necessary for optimizing the thermodynamics and kinetics of these reactions, while rigorously addressing both the biochemical and biophysical dimensions of the disease microenvironments to enhance therapeutic outcomes. It seeks to clarify the mechanisms underpinning catalytic biomaterials and evaluate their potential to revolutionize treatment strategies across various pathological conditions.

Ultralow Dose Iron-Copper Bimetallic Single-Atom Nanozymes for Efficient Photothermal-Chemodynamic Antibacterial and Wound Healing

The combination of photothermal and chemodynamic therapy (PTT-CDT) using single-atom nanozymes (SAzymes) shows great promise in combating pathogenic and drug-resistant bacteria. However, the photothermal conversion efficiency and catalytic activity of SAzymes with solely metal sites remain inadequate, often requiring high doses for effectiveness. Herein, a bimetallic single-atomic nanozymes with Fe and Cu active sites (FeCu BSNs) designed is reported for efficient treatment of bacterial infections through hyperthermia-amplified nanozyme catalysis strategy. The FeCu BSNs demonstrate remarkable peroxidase (POD) activity with a specific activity (SA) of 752.25 U mg-1, which is 2.3 folds larger than that of Fe SAzymes (323.45 U mg-1). Additionally, their photothermal effect achieve a photothermal conversion efficiency up to 56.26%, which is two times higher that of Fe SAzymes (29.69%) and Cu SAzymes (25.55%). These enhancements can be attributed to the hybridization of Fe and Cu sites. The FeCu BSNs-mediated PTT-CDT combination therapy demonstrates potent antibacterial effects in both in vitro and in vivo models, attributed to high levels of reactive oxygen species (ROS) generation and hyperthermia. This study effectively validates the application of ultralow-dose bimetallic single-atom nanozymes in PTT-CDT for wound healing, offering a promising approach for enhanced wound recovery.

NIR-II Light-Driven Multifunctional Nanozymes PS@CS for Efficient Therapy against Melanoma and Post-tumor Surgery Infection

Melanoma, the most prevalent form of skin cancer, is primarily treated with surgical intervention. However, complete tumor cell removal is challenging, and surgical wounds are prone to infection, complicating treatment and increasing costs. The successful treatment of melanoma generally requires multifunctional agents that are coordinated in tumor therapy and wound healing. In this study, we developed platinum (Pt)- and selenium (Se)-based nanozymes, Pt-Se@Chitosan (PS@CS), which exhibit synergistic antitumor and bactericidal efficacy attributed to their multienzyme activity and strong photothermal conversion efficiency. Furthermore, we engineered PS@CS hydrogels capable of inhibiting tumor regrowth postsurgery and accelerating healing of infected wounds. The PS@CS and PS@CS hydrogels presented herein incorporate characteristics including catalytic therapy, photothermal therapy, antibacterial properties, and skin damage healing, providing an innovative and comprehensive therapeutic approach for melanoma treatment.

Single Atom Engineered Antibiotics Overcome Bacterial Resistance

The outbreak of antibiotic-resistant bacteria, or "superbugs", poses a global public health hazard due to their resilience against the most effective last-line antibiotics. Identifying potent antibacterial agents capable of evading bacterial resistance mechanisms represents the ultimate defense strategy. This study shows that -the otherwise essential micronutrient- manganese turns into a broad-spectrum potent antibiotic when coordinated with a carboxylated nitrogen-doped graphene. This antibiotic material (termed NGA-Mn) not only inhibits the growth of a wide spectrum of multidrug-resistant bacteria but also heals wounds infected by bacteria in vivo and, most importantly, effectively evades bacterial resistance development. NGA-Mn exhibits up to 25-fold higher cytocompatibility to human cells than its minimum bacterial inhibitory concentration, demonstrating its potential as a next-generation antibacterial agent. Experimental findings suggest that NGA-Mn acts on the outer side of the bacterial cell membrane via a multimolecular collective binding, blocking vital functions in both Gram-positive and Gram-negative bacteria. The results underscore the potential of single-atom engineering toward potent antibiotics, offering simultaneously a long-sought solution for evading drug resistance development while being cytocompatible to human cells.

Near-Infrared Carbon Dots With Antibacterial and Osteogenic Activities for Sonodynamic Therapy of Infected Bone Defects

Repairing infected bone defects is hindered by the presence of stubborn bacterial infections and inadequate osteogenic activity. The incorporation of harmful antibiotics not only fosters the emergence of multidrug-resistant bacteria, but also diminishes the osteogenic properties of scaffold materials. In addition, it is essential to continuously monitor the degradation kinetics of scaffold materials at bone defect sites, yet the majority of bone repair materials lack imaging capability. To address these issues, this study reports for the first time the development of a single nanomaterial with triple functionality: efficient sonodynamic antibacterial activity, accelerated bone defect repair capability, and NIR imaging ability for visualized therapy of infected bone defects. Through rationally regulating the surface functional groups, the obtained multifunctional NIR carbon dots (NIR-CD) exhibit p-n junction-enhanced sonodynamic activity, narrow bandgap-facilitated NIR imaging capability, and negative charge-augmented osteogenic activity. The validation of NIR-CDs antibacterial and osteogenic activities in vivo is conducted by constructing 3D injectable hydrogels encapsulated by NIR-CDs (NIR-CD/GelMA). The implantation of multifunctional NIR-CD/GelMA hydrogel scaffolds in a model of MRSA-infected craniotomy defects results in almost complete restoration of the infected bone defects after 60 days. These findings will provide traceable, renewable, repairable and antibacterial candidate biomaterials for bone tissue engineering.

Copper Single-Atom Nanozyme Mimicking Galactose Oxidase with Superior Catalytic Activity and Selectivity

Due to the low stability and high cost of some natural enzymes, nanozymes have been developed as enzyme-imitating nanomaterials. Single-atom nanozymes are a class of nanozymes with metal centers that mimic the structure of metal-based natural enzymes. Herein, Cu-N-C single-atom nanozyme (SAN) is synthesized with excellent peroxidase- and enhanced oxidase-like activities to mimic the action of natural galactose oxidase. Cu-SAN demonstrates stereospecific activity akin to that of natural galactose oxidase by oxidizing D-galactose and primary alcohol but not L-Galactose or other carbohydrates. The SAN can catalyze the oxidation of galactose in the presence of oxygen, producing hydrogen peroxide as a sub-product. The produced hydrogen peroxide then oxidizes 3,3',5,5'-tetramethylbenzidine catalyzed by the SAN, yielding the typical blue product. The relationship between absorbance and galactose concentration is linear in the 1-60 µm range with a detection limit as low as 0.23 µm. This strategy can be utilized in the diagnosis of galactosemia disorder and detection of galactose in some dairy and other commercial products. DFT calculations clarify the high activity of the Cu sites in the POD-like reaction and explain the selectivity of the Cu-SAN oxidase-like reaction toward D-galactose.

Coordination-Driven in Situ Grown Copper Peroxide in Mesoporous Dopamine with Self-Supplied H2O2 for Synergistic Enhanced PTT/CDT Antibacterial Treatment and Wound Healing

As antibiotic resistance increases, alternative antimicrobial methods become essential. Chemical dynamics therapy (CDT) utilizing copper peroxide (CuO2) nanodots shows significant potential in antibacterial applications due to its ability to self-supply hydrogen peroxide (H2O2) on its own. This characteristic effectively addresses the challenges of low H2O2 levels and high glutathione (GSH) expression in the bacterial infection microenvironment. However, its tendency to aggregate and instability greatly affect its effectiveness. Therefore, this study developed a coordination-driven strategy to prepare copper peroxide-loaded mesoporous polydopamine nanomaterials (CuO2@MPDA) through in situ growth of CuO2 in mesoporous polydopamine utilizing the chelating interaction between amino and catechol structures of MPDA with copper ions. This strategy not only ensures that copper peroxide is evenly distributed within the pores of mesoporous polydopamine but also protects it through the shielding effect of pores, greatly enhancing its dispersibility and stability. More notably, the loading of CuO2 enhances the photothermal performance of MPDA by broadening its light absorption range, and MPDA-mediated photothermal therapy (PTT) can accelerate CuO2 to produce more hydroxyl radicals by speeding up chemical reactions, resulting in a combined boost in PTT and CDT. The developed CuO2@MPDA nanomaterials at very low concentrations exhibit improved antibacterial efficiency both in vitro and in vivo. Overall, this study provides an innovative strategy to construct an antibacterial nanoplatform for synergistically enhanced PTT/CDT dual-mode antibacterial treatment, exhibiting great potential for future biomedical applications.

Integrating enzyme-nanoparticles bring new prospects for the diagnosis and treatment of immune dysregulation in periodontitis

Enzymes play a significant role in mediating inflammatory and immune responses in periodontitis. Effective diagnosis, timely treatment, and continuous management of periodontal enzymes are essential to prevent undesirable consequences; however, this remains a significant challenge. Nanoparticles (NPs) have attracted significant attention in biomedicine because of their advantageous nanosized effects. NPs are conjugated with specific enzyme substrates at responsive sites that are triggered by periodontitis enzyme biomarkers, leading to functional or characteristic changes. In contrast, NPs with enzyme-mimetic activities exhibit catalytic activity, effectively destroying pathogenic biofilms and modulating the immune response in periodontitis. The unique properties of enzyme-targeting NPs have enabled the development of biosensors and fluorescent probes capable of identifying enzyme biomarkers associated with periodontitis. Enzyme-responsive and enzyme-mimetic NPs both exert therapeutic applications in the treatment of periodontitis. In this review, we provide a comprehensive overview of the enzymes associated with periodontitis, the mechanisms of enzyme-responsive and enzyme-mimetic NPs, recent advancements in the use of NPs for detecting these enzymes, and the therapeutic applications of NPs in targeting or mimicking enzyme functions. We also discuss the challenges and prospects of using NPs in the diagnosis and treatment of periodontitis.

Single-atom nanozymes for antibacterial applications

Bacteria have always been a thorny problem that threatens human health and food safety. Conventional antibiotic treatment often leads to the emergence of drug resistance. Therefore, the development of more effective antibacterial agents is urgently needed. Single-atom nanozymes (SAzymes) can efficiently eliminate bacteria due to their high atomic utilization, abundant active centers, and good natural enzyme mimicry, providing a potential alternative choice for antibiotics in antibacterial applications. Here, the antibacterial applications of SAzymes are reviewed and their catalytic properties are discussed from the aspects of active sites, coordination environment regulation and carrier selection. Then, the antibacterial effect of SAzymes is elaborated in combination with photothermal therapy (PTT) and sonodynamic therapy (SDT). Finally, the problems faced by SAzymes in antibacterial applications and their future development potential are proposed.

Recent Development of Nanozymes for Combating Bacterial Drug Resistance: A Review

The World Health Organization has warned that without effective action, deaths from drug-resistant bacteria can exceed 10 million annually, making it the leading cause of death. Conventional antibiotics are becoming less effective due to rapid bacterial drug resistance and slowed new antibiotic development, necessitating new strategies. Recently, materials with catalytic/enzymatic properties, known as nanozymes, have been developed, inspired by natural enzymes essential for bacterial eradication. Unlike recent literature reviews that broadly cover nanozyme design and biomedical applications, this review focuses on the latest advancements in nanozymes for combating bacterial drug resistance, emphasizing their design, structural characteristics, applications in combination therapy, and future prospects. This approach aims to promote nanozyme development for combating bacterial drug resistance, especially towards clinical translation.

Multifunctional Photothermal Nanorods for Targeted Treatment of Drug-Resistant Bacteria-Induced Wound Healing

The challenge of drug-resistant bacteria-induced wound healing in clinical and public healthcare settings is significant due to the negative impacts on surrounding tissues and difficulties in monitoring the healing progress. We developed photothermal antibacterial nanorods (AuNRs-PU) with the aim of selectively targeting and combating drug-resistant Pseudomonas aeruginosa (P. aeruginosa). The AuNRs-PU were engineered with a bacterial-specific targeting polypeptide (UBI29-41) and a bacterial adhesive carbohydrate polymer composed of galactose and phenylboronic acid. The objective was to facilitate sutureless wound closure by specially distinguishing between bacteria and nontarget cells and subsequently employing photothermal methods to eradicate the bacteria. AuNRs-PU demonstrated high photothermal conversion efficiency in 808 nm laser and effectively caused physical harm to drug-resistant P. aeruginosa. By integrating the multifunctional bacterial targeting copolymer onto AuNRs, AuNRs-PU showed rapid and efficient bacterial targeting and aggregation in the presence of bacteria and cells, consequently shielding cells from bacterial harm. In a diabetic rat wound model, AuNRs-PU played a crucial role in enhancing healing by markedly decreasing inflammation and expediting epidermis formation, collagen deposition, and neovascularization levels. Consequently, the multifunctional photothermal therapy shows promise in addressing the complexities associated with managing drug-resistant infected wound healing.

Nanozymes in Biomedical Applications: Innovations Originated From Metal-Organic Frameworks

Nanozymes exhibit significant potential in medical theranostics, environmental protection, energy development, and biopharmaceuticals due to their exceptional catalytic performance. Compared with natural enzymes, nanozymes have the advantages of simple preparation and purification, convenient production and low cost. Therefore, it is very important to prepare nanozymes quickly and efficiently, which not only helps to expand their application scope, but also can further exert their great potential in various fields. Metal-organic frameworks (MOF) materials serve as versatile substrates for constructing nanozymes, offering unique advantages like adjustable structure, high specific surface area, and porous channels. MOF coordination nodes constructed from metal ions or metal clusters have unique properties that can be leveraged to tailor nanozyme characteristics for different applications. This review describes and analyzes recent methods for constructing nanozymes using MOF materials, and explores their application prospects in biomedicine. By expounding the preparation techniques and biomedical applications of nanozymes, this review aims to inspire researchers to develop innovative nanozyme materials and explore new application directions.

Multifunctional Adaptable Injectable TiN-Based Hydrogels for Antitumor and Antidrug-Resistant Bacterial Therapy

The close relationship between bacteria and tumors has recently attracted increasing attention, and an increasing number of resources are being invested in the research and development of biomedical materials designed for the treatment of both. In this study, prefabricated TiN nanodots (NDs) and Fe(CO)5 nanoparticles are combined into sodium alginate (ALG) hydrogels to create a biomedical material for the topical treatment of breast cancer and subcutaneous abscesses, and a pseudocatalytic hydrogel with intrinsic photothermal and antibacterial activities is synthesized. TiN+Fe(CO)5+ALG hydrogels are used to determine the ability of Fe(CO)5 to promote CO production. Moreover, TiN NDs catalyze the production of reactive oxygen species (ROS) from hydrogen peroxide in tumor microenvironments and exhibit excellent photothermal conversion properties. After local injection of the TiN+Fe(CO)5+ALG hydrogel into subcutaneous tumors and subcutaneous abscesses, and two-zone near-infrared (NIR-II) irradiation, tumor cells and methicillin-resistant Staphylococcus aureus are effectively removed by the hydrogel, the mouse epidermis exhibiting complete recovery within 8 d, indicating that this hydrogel exhibits better antibacterial efficacy than the small-molecule antibiotic penicillin. This study demonstrates the potential of novel hydrogels for antitumor and antimicrobial combination therapy and aims to provide design ideas for the research and development of multifunctional antitumor and antimicrobial drug combinations.

Copper-doped cherry blossom carbon dots with peroxidase-like activity for antibacterial applications

Safety concerns arising from bacteria present a significant threat to human health, underscoring the pressing need for the exploration of novel antimicrobial materials. Nanozymes, as a new type of nanoscale material, have attracted widespread attention for antibacterial applications owing to their ability to mimic the catalytic activity of natural enzymes. In this work, we have constructed copper-doped cherry blossom carbon dots (Cu-CDs) with excellent peroxidase-like (POD) activity using a one-pot hydrothermal method. The utilization of cherry blossom as a natural material precursor significantly enhances its biocompatibility. Furthermore, the incorporation of copper ions initiates Fenton-like reaction-triggered POD-like catalytic activity, effectively eradicating bacteria by converting hydrogen peroxide (H2O2) into hydroxyl radicals (·OH). The antibacterial test results demonstrate that Cu-CDs exhibit a bactericidal efficacy of over 90% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). This study presents a novel environmentally friendly nanozyme material derived from natural sources, exhibiting significant antimicrobial properties and offering innovative insights for the advancement of antimicrobial materials.

A Glutathione-Consuming Bimetallic Nano-Bomb with the Combination of Photothermal and Chemodynamic Therapy for Tumors: An in vivo and in vitro Study

Background

Chemodynamic therapy (CDT) faces challenges of low catalytic ion efficiency and ROS production. We developed a ROS nano-bomb, Cu/ZIF-8@GA-Fe, to address these issues.

Methods

The nano-bomb was synthesized by doping copper into ZIF-8 and assembling Fe3+ and gallic acid (GA). It was tested for reactive oxygen species (ROS) generation in acidic conditions and its photothermal properties.

Results

In an acidic micro environment, Cu/ZIF-8@GA-Fe effectively released Fe3+ and Cu2+, depleting GSH and generating ROS. The GA-Fe coating provided photothermal heat and was used to enhance Fenton reactions via dual ions for increasing ROS production. In vivo and in vitro experiments, Cu/ZIF-8@GA-Fe inhibited tumor growth with minimal side effects.

Conclusion

Cu/ZIF-8@GA-Fe shows promise for safe and effective CDT, offering a synergistic approach to tumor therapy.

Novel Biomaterials for Wound Healing and Tissue Regeneration

Skin is the first defense barrier of the human body, which can resist the invasion of external dust, microorganisms and other pollutants, and ensure that the human body maintains the homeostasis of the internal environment. Once the skin is damaged, the health threat to the human body will increase. Wound repair and the human internal environment are a dynamic process. How to effectively accelerate the healing of wounds without affecting the internal environment of the human body and guarantee that the repaired tissue retains its original function as much as possible has become a research hotspot. With the advancement of technology, researchers have combined new technologies to develop and prepare various types of materials for wound healing. This article will introduce the wound repair materials developed and prepared in recent years from three types: nanofibers, composite hydrogels, and other new materials. The paper aims to provide reference for researchers in related fields to develop and prepare multifunctional materials. This may be helpful to design more ideal materials for clinical application, and then achieve better wound healing and regeneration effects.

Iron/Molybdenum Sulfide Nanozyme Cocatalytic Fenton Reaction for Photothermal/Chemodynamic Efficient Wound Healing

The issue of bacterial infectious diseases remains a significant concern worldwide, particularly due to the misuse of antibiotics, which has caused the emergence of antibiotic-resistant strains. Fortunately, the rapid development of nanomaterials has propelled significant progress in antimicrobial therapy, offering promising solutions. Among them, the utilization of nanoenzyme-based chemodynamic therapy (CDT) has become a highly hopeful approach to combating bacterial infectious diseases. Nevertheless, the application of CDT appears to be facing certain constraints for its low efficiency in the Fenton reaction at the infected site. In this study, we have successfully synthesized a versatile nanozyme, which was a composite of molybdenum sulfide (MoS2) and iron sulfide (FeS2), through the hydrothermal method. The results showed that iron/molybdenum sulfide nanozymes (Fe/Mo SNZs) with desirable peroxidase (POD) mimic activity can generate cytotoxic reactive oxygen species (ROS) by successfully triggering the Fenton reaction. The presence of MoS2 significantly accelerates the conversion of Fe2+/Fe3+ through a cocatalytic reaction that involves the participation of redox pairs of Mo4+/Mo6+, thereby enhancing the efficiency of CDT. Additionally, based on the excellent photothermal performance of Fe/Mo SNZs, a near-infrared (NIR) laser was used to induce localized temperature elevation for photothermal therapy (PTT) and enhance the POD-like nanoenzymatic activity. Notably, both in vitro and in vivo results demonstrated that Fe/Mo SNZs with good broad-spectrum antibacterial properties can help eradicate Gram-negative bacteria like Escherichia coli and Gram-positive bacteria like Staphylococcus aureus. The most exciting thing is that the synergistic PTT/CDT exhibited astonishing antibacterial ability and can achieve complete elimination of bacteria, which promoted wound healing after infection. Overall, this study presents a synergistic PTT/CDT strategy to address antibiotic resistance, providing avenues and directions for enhancing the efficacy of wound healing treatments and offering promising prospects for further clinical use in the near future.

Electric Field-Responsive Gold Nanoantennas for the Induction of a Locoregional Tumor pH Change Using Electrolytic Ablation Therapy

Electrolytic ablation (EA) is a burgeoning treatment for solid tumors, in which electrical energy catalyzes a chemical reaction to generate reactive species that can eradicate cancer cells. However, the application of this technique has been constrained owing to the limited spatial effectiveness and complexity of the electrode designs. Therefore, the incorporation of nanotechnology into EA is anticipated to be a significant improvement. Herein, we present a therapeutic approach based on difructose dianhydride IV-conjugated polyethylenimine-polyethylene glycol-modified gold nanorods as electric nanoantennas and nanoelectrocatalysts for EA. We demonstrate that square-wave direct current (DC) fields trigger a reaction between water molecules and chloride ions on the gold nanorod surface, generating electrolytic products including hydrogen, oxygen, and chlorine gases near the electrodes, changing the pH, and inducing cell death. These electric nanoantennas showed significant efficacy in treating colorectal cancer both in vitro and in vivo after DC treatment. These findings clearly indicate that gold nanoantennas enhance the effectiveness of EA by creating a localized electric field and catalyzing electrolytic reactions for the induction of locoregional pH changes within the tumor. By overcoming the limitations of traditional EA and offering an enhanced level of tumor specificity and control, this nanotechnology-integrated approach advances further innovations in cancer therapies.

A Versatile Chitosan-Based Hydrogel Accelerates Infected Wound Healing via Bacterial Elimination, Antioxidation, Immunoregulation, and Angiogenesis

Drug-resistant bacterial infection of cutaneous wounds causes great harm to the human body. These infections are characterized by a microenvironment with recalcitrant bacterial infections, persistent oxidative stress, imbalance of immune regulation, and suboptimal angiogenesis. Treatment strategies available to date are incapable of handling the healing dynamics of infected wounds. A Schiff base and borate ester cross-linked hydrogel, based on phenylboronic acid-grafted chitosan (CS-PBA), dibenzaldehyde-grafted poly(ethylene glycol), and tannic acid (TA), is fabricated in the present study. Customized phenylboronic acid-modified zinc oxide nanoparticles (ZnO) are embedded in the hydrogel prior to gelation. The CPP@ZnO-P-TA hydrogel effectively eliminates methicillin-resistant Staphylococcus aureus (MRSA) due to the pH-responsive release of Zn2+ and TA. Killing is achieved via membrane damage, adenosine triphosphate reduction, leakage of intracellular components, and hydrolysis of bacterial o-nitrophenyl-β-d-galactopyranoside. The CPP@ZnO-P-TA hydrogel is capable of scavenging reactive oxygen and nitrogen species, alleviating oxidative stress, and stimulating M2 polarization of macrophages. The released Zn2+ and TA also induce neovascularization via the PI3K/Akt pathway. The CPP@ZnO-P-TA hydrogel improves tissue regeneration in vivo by alleviating inflammatory responses, stimulating angiogenesis, and facilitating collagen deposition. These findings suggest that this versatile hydrogel possesses therapeutic potential for the treatment of MRSA-infected cutaneous wounds.

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

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

Metabolomics and network pharmacology reveal the mechanism of Castanopsis honey against Streptococcus pyogenes

Streptococcus pyogenes (GAS) is one of the most virulent and infectious bacteria, severely threatening health and lives of people worldwide. Honey has been proven to have effective capability against GAS, but the underlying metabolites and mechanisms are still unclear. In this study, the Castanopsis honey (CH) showed significant antibacterial ability compared to other seven kinds of honey and artificial honey. Furthermore, the antibacterial metabolites and their targets in CH were screened by combined method of metabolomics, network pharmacology, and molecular docking. The results suggested that the activities of two antioxidant enzymes, glutathione peroxidase and tyrosyl tRNA synthetase identified as the primary targets, were significantly inhibited by CH, which significantly increased the level of oxidative stress in GAS. The results revealed a possibly novel mechanism regulating the oxidative stress and inhibits the growth in bacteria, providing strong experimental evidence to support the further development of CH as a novel antibacterial agent.

Single-atom nanozymes shines diagnostics of gastrointestinal diseases

Various clinical symptoms of digestive system, such as infectious, inflammatory, and malignant disorders, have a profound impact on the quality of life and overall health of patients. Therefore, the chase for more potent medicines is both highly significant and urgent. Nanozymes, a novel class of nanomaterials, amalgamate the biological properties of nanomaterials with the catalytic activity of enzymes, and have been engineered for various biomedical applications, including complex gastrointestinal diseases (GI). Particularly, because of their distinctive metal coordination structure and ability to maximize atom use efficiency, single-atom nanozymes (SAzymes) with atomically scattered metal centers are becoming a more viable substitute for natural enzymes. Traditional nanozyme design strategies are no longer able to meet the current requirements for efficient and diverse SAzymes design due to the diversification and complexity of preparation processes. As a result, this review emphasizes the design concept and the synthesis strategy of SAzymes, and corresponding bioenzyme-like activities, such as superoxide dismutase (SOD), peroxidase (POD), oxidase (OXD), catalase (CAT), and glutathione peroxidase (GPx). Then the various application of SAzymes in GI illnesses are summarized, which should encourage further research into nanozymes to achieve better application characteristics.

Single-Atom-Based Nanoenzyme in Tissue Repair

Since the discovery of ferromagnetic nanoparticles Fe3O4 that exhibit enzyme-like activity in 2007, the research on nanoenzymes has made significant progress. With the in-depth study of various nanoenzymes and the rapid development of related nanotechnology, nanoenzymes have emerged as a promising alternative to natural enzymes. Within nanozymes, there is a category of metal-based single-atom nanozymes that has been rapidly developed due to low cast, convenient preparation, long storage, less immunogenicity, and especially higher efficiency. More importantly, single-atom nanozymes possess the capacity to scavenge reactive oxygen species through various mechanisms, which is beneficial in the tissue repair process. Herein, this paper systemically highlights the types of metal single-atom nanozymes, their catalytic mechanisms, and their recent applications in tissue repair. The existing challenges are identified and the prospects of future research on nanozymes composed of metallic nanomaterials are proposed. We hope this review will illuminate the potential of single-atom nanozymes in tissue repair, encouraging their sequential clinical translation.

Atomic Engineering of Single-Atom Nanozymes for Biomedical Applications

Single-atom nanozymes (SAzymes) showcase not only uniformly dispersed active sites but also meticulously engineered coordination structures. These intricate architectures bestow upon them an exceptional catalytic prowess, thereby captivating numerous minds and heralding a new era of possibilities in the biomedical landscape. Tuning the microstructure of SAzymes on the atomic scale is a key factor in designing targeted SAzymes with desirable functions. This review first discusses and summarizes three strategies for designing SAzymes and their impact on reactivity in biocatalysis. The effects of choices of carrier, different synthesis methods, coordination modulation of first/second shell, and the type and number of metal active centers on the enzyme-like catalytic activity are unraveled. Next, a first attempt is made to summarize the biological applications of SAzymes in tumor therapy, biosensing, antimicrobial, anti-inflammatory, and other biological applications from different mechanisms. Finally, how SAzymes are designed and regulated for further realization of diverse biological applications is reviewed and prospected. It is envisaged that the comprehensive review presented within this exegesis will furnish novel perspectives and profound revelations regarding the biomedical applications of SAzymes.

Metal natural product complex Ru-procyanidins with quadruple enzymatic activity combat infections from drug-resistant bacteria

Bacterial infection hampers wound repair by impeding the healing process. Concurrently, inflammation at the wound site triggers the production of reactive oxygen species (ROS), causing oxidative stress and damage to proteins and cells. This can lead to chronic wounds, posing severe risks. Therefore, eliminating bacterial infection and reducing ROS levels are crucial for effective wound healing. Nanozymes, possessing enzyme-like catalytic activity, can convert endogenous substances into highly toxic substances, such as ROS, to combat bacteria and biofilms without inducing drug resistance. However, the current nanozyme model with single enzyme activity falls short of meeting the complex requirements of antimicrobial therapy. Thus, developing nanozymes with multiple enzymatic activities is essential. Herein, we engineered a novel metalloenzyme called Ru-procyanidin nanoparticles (Ru-PC NPs) with diverse enzymatic activities to aid wound healing and combat bacterial infections. Under acidic conditions, due to their glutathione (GSH) depletion and peroxidase (POD)-like activity, Ru-PC NPs combined with H2O2 exhibit excellent antibacterial effects. However, in a neutral environment, the Ru-PC NPs, with catalase (CAT) activity, decompose H2O2 to O2, alleviating hypoxia and ensuring a sufficient oxygen supply. Furthermore, Ru-PC NPs possess exceptional antioxidant capacity through their superior superoxide dismutase (SOD) enzyme activity, effectively scavenging excess ROS and reactive nitrogen species (RNS) in a neutral environment. This maintains the balance of the antioxidant system and prevents inflammation. Ru-PC NPs also promote the polarization of macrophages from M1 to M2, facilitating wound healing. More importantly, Ru-PC NPs show good biosafety with negligible toxicity. In vivo wound infection models have confirmed the efficacy of Ru-PC NPs in inhibiting bacterial infection and promoting wound healing. The focus of this work highlights the quadruple enzymatic activity of Ru-PC NPs and its potential to reduce inflammation and promote bacteria-infected wound healing.

Multi-Enzyme-Based Superabsorbent Hydrogel for Self-Enhanced NIR-II Photothermal-Catalytic Antibacterial Therapy

The synergistic strategy of nanozyme-based catalytic therapy and photothermal therapy holds great potential for combating bacterial infection. However, challenges such as single and limited enzyme catalytic property, unfavorable catalytic environment, ineffective interaction between nanozymes and bacteria, unsafe laser irradiation ranges, and failed trauma fluid management impede their antibacterial capability and wound healing speed. Herein, for the first time, a PNMn hydrogel is fabricated with multi-enzyme activities and excellent near-infrared (NIR)-II photothermal performance for self-enhanced NIR-II photothermal-catalytic capabilities to efficiently eradicate bacteria. This hydrogel triggers parallel and cascade reactions to generate •OH, •O2 -, and 1O2 radicals from H2O2 and O2 without external energy input. Notably, it provides a suitable catalytic environment while capturing bacteria (≈30.1% of Escherichia coli and ≈29.3% of Staphylococcus aureus) to reinforce antibacterial activity. Furthermore, the PNMn hydrogel expedites skin wound healing by managing excess fluid (swelling rate up to ≈7299%). The PNMn hydrogel possesses remarkable stretching, elasticity, toughness, and adhesive characteristics under any shape of the wound, thus making it suitable for wound dressing. Therefore, the PNMn hydrogel has great potential to be employed as a next-generation wound dressing in the clinical context, providing a non-antibiotic strategy to improve the antibacterial performance and promote wound healing.

Electrogenerated Chemiluminescence Imaging of Single-Atom Nanocatalysts

Single-atom catalysts (SACs), distinguished by their maximum atom efficiency and precise control over the coordination and electronic properties of individual atoms, show great promise in electrocatalysis. Gaining a comprehensive understanding of the electrochemical performance of SACs requires the screening of electron transfer process at micro/nano scale. This research pioneers the use of electrogenerated chemiluminescence microscopy (ECLM) to observe the electrocatalytic reactions at individual SACs. It boasts sensitivity at the single photon level and temporal resolution down to 100 ms, enabling real-time capture of the electrochemical behavior of individual SACs during potential sweeping. Leveraging the direct correlation between ECL emission and heterogeneous electron transfer processes, we introduced photon flux density for quantitative analysis, unveiling the electrocatalytic efficiency of individual SACs. This approach systematically reveals the relationship between SACs based on different metal atoms and their peroxidase (POD)-like activity. The outcomes contribute to a fundamental understanding of SACs and pave the way for designing SACs with diverse technological and industrial applications.

Single-Mg-Atom Catalyst with a Dual Active Center as an Emerging Promising Sensing Platform

Bisphenol compounds [bisphenol A (BPA), etc.] are one class of the most important and widespread pollutants in food and environment, which pose severe endocrine disrupting effect, reproductive toxicity, immunotoxicity, and metabolic toxicity on humans and animals. Simultaneous rapid determination of BPA and its analogues (bisphenol S, bisphenol AF, etc.) with extraordinary potential resolution and sensitivity is of great significance but still extremely challenging. Herein, a series of single-atom catalysts (SACs) were synthesized by anchoring different metal atoms (Mg, Co, Ni, and Cu) on N-doped carbon materials and used as sensing materials for simultaneous detection of bisphenols with similar chemical structures. The Mg-based SAC enables the potential discrimination and simultaneous rapid detection of multiple bisphenols, showing outstanding analytical performances, outperforming all other SACs and traditional electrode materials. Our experiments and density functional theory calculations show that pyrrolic N serves as the adsorption site for the adsorption of bisphenols and the Mg atom serves as the active site for the electrocatalytic oxidation of bisphenols, which play a synergistic role as dual active centers in improving the sensing performance. The results of this work may pave the way for the rational design of SACs as advanced sensing and catalytic materials.

Ultralow Loading Copper-Intercalated MoO3 Nanobelts with High Activity against Antibiotic-Resistant Bacteria

In recent years, the infection rate of antibiotic resistance has been increasing year by year, and the prevalence of super bacteria has posed a great threat to human health. Therefore, there is an urgent need to find new antibiotic alternatives with long-term inhibitory activity against a broad spectrum of bacteria and microorganisms in order to avoid the proliferation of more multidrug-resistant (MDR) bacteria. The presence of natural van der Waals (vdW) gaps in layered materials allows them to be easily inserted by different guest species, providing an attractive strategy for optimizing their physicochemical properties and applications. Here, we have successfully constructed a copper-intercalated α-MoO3 nanobelt based on nanoenzymes, which is antibacterial through the synergistic effect of multiple enzymes. Compared with α-MoO3, MoO3-x/Cu nanobelts with a copper loading capacity of 2.11% possess enhanced peroxidase (POD) catalytic activity and glutathione (GSH) depletion, indicating that copper intercalation significantly improves the catalytic performance of the nanoenzymes. The MoO3-x/Cu nanobelts are effective in inducing POD and oxidase (OXD) and catalase (CAT) activities in the presence of H2O2 and O2, which resulted in the generation of large amounts of reactive oxygen species (ROS), which were effective in bacterial killing. Interestingly, MoO3-x/Cu nanobelts can serve as glutathione oxidase (GSHOx)-like nanoenzymes, which can deplete GSH in bacteria and thus significantly improve the bactericidal effect. The multienzyme-catalyzed synergistic antimicrobial strategy shows excellent antimicrobial efficiency against β-lactamase-producing Escherichia coli (ESBL-E. coli) and methicillin-resistant Staphylococcus aureus (MRSA). MoO3-x/Cu exhibits excellent spectral bactericidal properties at very low concentrations (20 μg mL-1). Our work highlights the wide range of antibacterial and anti-infective biological applications of copper-intercalated MoO3-x/Cu nanobelt catalysts.

Engineering Copper-Containing Nanoparticles-Loaded Silicene Nanosheets with Triple Enzyme Mimicry Activities and Photothermal Effect for Promoting Bacteria-Infected Wound Healing

Skin wounds accompanied by bacterial infections threaten human health, and conventional antibiotic treatments are ineffective for drug-resistant bacterial infections and chronically infected wounds. The development of non-antibiotic-dependent therapeutics is highly desired but remains a challenging issue. Recently, 2D silicene nanosheets with considerable biocompatibility, biodegradability, and photothermal-conversion performance have received increasing attention in biomedical fields. Herein, copper-containing nanoparticles-loaded silicene (Cu2.8O@silicene-BSA) nanosheets with triple enzyme mimicry catalytic (peroxidase, catalase, and oxidase-like) activities and photothermal function are rationally designed and fabricated for efficient bacterial elimination, angiogenesis promotion, and accelerated wound healing. Cu2.8O@silicene-BSA nanosheets display excellent antibacterial activity through synergistic effects of reactive oxygen species generated from multiple catalytic reactions, intrinsic bactericidal activity of released Cu2+ ions, and photothermal effects, achieving high antibacterial efficiencies on methicillin-resistant Staphylococcus aureus (MRSA) of 99.1 ± 0.7% in vitro and 97.2 ± 1.6% in vivo. In addition, Cu2.8O@silicene-BSA nanosheets exhibit high biocompatibility for promoting human umbilical vein endothelial cell (HUVEC) proliferation and angiogenic differentiation. In vivo experiments reveal that Cu2.8O@silicene-BSA nanosheets with synergistic photothermal/chemodynamic therapeutics effectively accelerate MRSA-infected wound healing by eliminating bacteria, alleviating inflammation, boosting collagen deposition, and promoting angiogenesis. This research presents a promising strategy to engineer photothermal-assisted nanozyme catalysis for bacteria-invaded wound healing.

Iron-Single-Atom Nanozyme with NIR Enhanced Catalytic Activities for Facilitating MRSA-Infected Wound Therapy

Patients with methicillin-resistant Staphylococcus aureus (MRSA) infections may have higher death rates than those with non-drug-resistant infections. Nanozymes offer a promising approach to eliminating bacteria by producing reactive oxygen species. However, most of the conventional nanozyme technologies encounter significant challenges with respect to size, composition, and a naturally low number of active sites. The present study synthesizes a iron-single-atom structure (Fe-SAC) via nitrogen doped-carbon, a Fe-N5 catalyst (Fe-SAC) with a high metal loading (4.3 wt.%). This catalyst permits the development of nanozymes consisting of single-atom structures with active sites resembling enzymes, embedded within nanomaterials. Fe-SAC displays peroxidase-like activities upon exposure to H2O2. This structure facilitates the production of hydroxyl radicals, well-known for their strong bactericidal effects. Furthermore, the photothermal properties augment the bactericidal efficacy of Fe-SAC. The findings reveal that Fe-SAC disrupts the bacterial cell membranes and the biofilms, contributing to their antibacterial effects. The bactericidal properties of Fe-SAC are harnessed, which eradicates the MRSA infections in wounds and improves wound healing. Taken together, these findings suggest that single Fe atom nanozymes offer a novel perspective on the catalytic mechanism and design, holding immense potential as next-generation nanozymes.

Bimetallic PtPd Atomic Clusters as Apoptosis/Ferroptosis Inducers for Antineoplastic Therapy through Heterogeneous Catalytic Processes

Active polymetallic atomic clusters can initiate heterogeneous catalytic reactions in the tumor microenvironment, and the products tend to cause manifold damage to cell metabolic functions. Herein, bimetallic PtPd atomic clusters (BAC) are constructed by the stripping of Pt and Pd nanoparticles on nitrogen-doped carbon and follow-up surface PEGylation, aiming at efficacious antineoplastic therapy through heterogeneous catalytic processes. After endocytosed by tumor cells, BAC with catalase-mimic activity can facilitate the decomposition of endogenous H2O2 into O2. The local oxygenation not only alleviates hypoxia to reduce the invasion ability of cancer cells but also enhances the yield of •O2- from O2 catalyzed by BAC. Meanwhile, BAC also exhibit peroxidase-mimic activity for •OH production from H2O2. The enrichment of reactive oxygen species (ROS), including the radicals of •OH and •O2-, causes significant oxidative cellular damage and triggers severe apoptosis. In another aspect, intrinsic glutathione (GSH) peroxidase-like activity of BAC can indirectly upregulate the level of lipid peroxides and promote ferroptosis. Such deleterious redox dyshomeostasis caused by ROS accumulation and GSH consumption also results in immunogenic cell death to stimulate antitumor immunity for metastasis suppression. Collectively, this paradigm is expected to inspire more facile designs of polymetallic atomic clusters in disease therapy.

H2O2 self-supplying and GSH-depleting nanosystem for amplified NIR mediated-chemodynamic therapy of MRSA biofilm-associated infections

Reactive oxygen species (ROS) has emerged as potent therapeutic agents for biofilm-associated bacterial infections. Chemodynamic therapy (CDT), involving the generation of high-energy ROS, displays great potential in the therapy of bacterial infections. However, challenges such as insufficient hydrogen peroxide (H2O2) and over-expressed glutathione (GSH) levels within the microenvironment of bacterial biofilms severely limit the antibacterial efficacy of CDT. Herein, we have developed a multifunctional nanoplatform (CuS@CaO2@Dex) by integrating copper sulfide (CuS) and calcium peroxide (CaO2) into dextran (Dex)-coated nanoparticles. This innovative platform enhanced ROS generation for highly efficient biofilm elimination by simultaneously supplying H2O2 and depleting GSH. The Dex-coating facilitated the penetrability of CuS@CaO2@Dex into biofilms, while CaO2 generated a substantial amount of H2O2 in the acidic biofilm microenvironment. CuS, through a Fenton-like reaction, catalyzed the conversion of self-supplied H2O2 into hydroxyl radicals (•OH) and consumed the overexpressed GSH. Additionally, the incorporation of near-infrared II (NIR II) laser irradiation enhanced the photothermal properties of CuS, improving the catalytic efficiency of the Fenton-like reaction for enhanced antibacterial effects. In vivo experiments have demonstrated that CuS@CaO2@Dex exhibited remarkable antibacterial and antibiofilm efficacy, exceptional wound healing capabilities, and notable biosafety. In summary, the Dex-coated nanoplatform proposed in this study, with its self-sterilization capability through ROS, holds significant potential for future biomedical applications.

MgO@polydopamine Nanoparticle-Loaded Photothermal Microneedle Patches Combined with Chitosan Gel Dressings for the Treatment of Infectious Wounds

As for wound drug delivery, microneedles (MNs) have attracted wide attention. However, while effective at increasing the depth of drug delivery, traditional MNs often have limited drug loads and have difficulty penetrating scabs on wounds. Herein, we develop a drug delivery system combining MgO@polydopamine (MgO@PDA) nanoparticle-loaded photothermal MN patches and chitosan (CS) gel to inhibit the formation of scabs and deliver sufficient drugs into deep tissue. When inserted into the wound, the MN system can keep the wound bed moist and weakly acidic to inhibit the formation of scabs and accelerate wound closure. The released MgO@PDA nanoparticles from both the tips and the backing layer, which immensely increase the drug load, continuously release Mg2+ in the moist, weakly acidic wound bed, promoting tissue migration and the formation of microvessels. MgO@PDA nanoparticles show excellent antibacterial activity under near-infrared irradiation synergized with the CS gel, and the PDA coating can also overcome the adverse effects of oxidative stress. Through in vitro and in vivo experiments, the MN system showed remarkable antibacterial, antioxidant, anti-inflammatory, and pro-angiogenic effects, indicating its potential in the treatment of infectious wounds.

Current Advances on the Single-Atom Nanozyme and Its Bioapplications

Nanozymes, a class of nanomaterials mimicking the function of enzymes, have aroused much attention as the candidate in diverse fields with the arbitrarily tunable features owing to the diversity of crystalline nanostructures, composition, and surface configurations. However, the uncertainty of their active sites and the lower intrinsic deficiencies of nanomaterial-initiated catalysis compared with the natural enzymes promote the pursuing of alternatives by imitating the biological active centers. Single-atom nanozymes (SAzymes) maximize the atom utilization with the well-defined structure, providing an important bridge to investigate mechanism and the relationship between structure and catalytic activity. They have risen as the new burgeoning alternative to the natural enzyme from in vitro bioanalytical tool to in vivo therapy owing to the flexible atomic engineering structure. Here, focus is mainly on the three parts. First, a detailed overview of single-atom catalyst synthesis strategies including bottom-up and top-down approaches is given. Then, according to the structural feature of single-atom nanocatalysts, the influence factors such as central metal atom, coordination number, heteroatom doping, and the metal-support interaction are discussed and the representative biological applications (including antibacterial/antiviral performance, cancer therapy, and biosensing) are highlighted. In the end, the future perspective and challenge facing are demonstrated.

Nanozyme-Based Regulation of Cellular Metabolism and Their Applications

Metabolism is the sum of the enzyme-dependent chemical reactions, which produces energy in catabolic process and synthesizes biomass in anabolic process, exhibiting high similarity in mammalian cell, microbial cell, and plant cell. Consequently, the loss or gain of metabolic enzyme activity greatly affects cellular metabolism. Nanozymes, as emerging enzyme mimics with diverse functions and adjustable catalytic activities, have shown attractive potential for metabolic regulation. Although the basic metabolic tasks are highly similar for the cells from different species, the concrete metabolic pathway varies with the intracellular structure of different species. Here, the basic metabolism in living organisms is described and the similarities and differences in the metabolic pathways among mammalian, microbial, and plant cells and the regulation mechanism are discussed. The recent progress on regulation of cellular metabolism mainly including nutrient uptake and utilization, energy production, and the accompanied redox reactions by different kinds of oxidoreductases and their applications in the field of disease therapy, antimicrobial therapy, and sustainable agriculture is systematically reviewed. Furthermore, the prospects and challenges of nanozymes in regulating cell metabolism are also discussed, which broaden their application scenarios.

One-Stop Integrated Nanoagent for Bacterial Biofilm Eradication and Wound Disinfection

To meet the requirements of biomedical applications in the antibacterial realm, it is of great importance to explore nano-antibiotics for wound disinfection that can prevent the development of drug resistance and possess outstanding biocompatibility. Therefore, we attempted to synthesize an atomically dispersed ion (Fe) on phenolic carbon quantum dots (CQDs) combined with an organic photothermal agent (PTA) (Fe@SAC CQDs/PTA) via a hydrothermal/ultrasound method. Fe@SAC CQDs adequately exerted peroxidase-like activity while the PTA presented excellent photothermal conversion capability, which provided enormous potential in antibacterial applications. Based on our work, Fe@SAC CQDs/PTA exhibited excellent eradication of Escherichia coli (>99% inactivation efficiency) and Staphylococcus aureus (>99% inactivation efficiency) based on synergistic chemodynamic therapy (CDT) and photothermal therapy (PTT). Moreover, in vitro experiments demonstrated that Fe@SAC CQDs/PTA could inhibit microbial growth and promote bacterial biofilm destruction. In vivo experiments suggested that Fe@SAC CQDs/PTA-mediated synergistic CDT and PTT exhibited great promotion to wound disinfection and recovery effects. This work indicated that Fe@SAC CQDs/PTA could serve as a broad-spectrum antimicrobial nano-antibiotic, which was simultaneously beneficial for bacterial biofilm eradication, wound disinfection, and wound healing.

Nanozyme-Engineered Hydrogels for Anti-Inflammation and Skin Regeneration

Inflammatory skin disorders can cause chronic scarring and functional impairments, posing a significant burden on patients and the healthcare system. Conventional therapies, such as corticosteroids and nonsteroidal anti-inflammatory drugs, are limited in efficacy and associated with adverse effects. Recently, nanozyme (NZ)-based hydrogels have shown great promise in addressing these challenges. NZ-based hydrogels possess unique therapeutic abilities by combining the therapeutic benefits of redox nanomaterials with enzymatic activity and the water-retaining capacity of hydrogels. The multifaceted therapeutic effects of these hydrogels include scavenging reactive oxygen species and other inflammatory mediators modulating immune responses toward a pro-regenerative environment and enhancing regenerative potential by triggering cell migration and differentiation. This review highlights the current state of the art in NZ-engineered hydrogels (NZ@hydrogels) for anti-inflammatory and skin regeneration applications. It also discusses the underlying chemo-mechano-biological mechanisms behind their effectiveness. Additionally, the challenges and future directions in this ground, particularly their clinical translation, are addressed. The insights provided in this review can aid in the design and engineering of novel NZ-based hydrogels, offering new possibilities for targeted and personalized skin-care therapies.

Arginine-Enhanced Antimicrobial Activity of Nanozymes against Gram-Negative Bacteria

The continuous reduction of clinically available antibiotics has made it imperative to exploit more effective antimicrobial therapies, especially for difficult-to-treat Gram-negative pathogens. Herein, it is shown that the combination of an antimicrobial nanozyme with the clinically compatible basic amino acid L-arginine affords a potent treatment for infections with Gram-negative pathogens. In particular, the antimicrobial activity of the antimicrobial nanozyme is dramatically increased by ≈1000-fold after L-arginine stimulation. Specifically, the combination therapy enhances bacterial outer and inner membrane permeability and promotes intracellular reactive oxygen species (ROS) generation. Moreover, the metabolomic and transcriptomic results reveal that combination treatment leads to the increased ROS-mediated damage by inhibiting the tricarboxylic acid cycle and oxidative phosphorylation, thereby inducing an imbalance of the antioxidant and oxidant systems. Importantly, L-arginine dramatically significantly accelerates the healing of infected wounds in mouse models of multidrug-resistant peritonitis-sepsis and skin wound infection. Overall, this work demonstrates a novel synergistic antibacterial strategy by combining the antimicrobial nanozymes with L-arginine, which substantively facilitates the nanozyme-mediated killing of pathogens by promoting ROS production.

Fe-Capsaicin Nanozymes Attenuate Sepsis-Induced Acute Lung Injury via NF-κB Signaling

Background

In sepsis, the lungs are one of the most severely affected organs, usually resulting in acute lung injury (ALI). Capsaicin (CAP) is a natural compound found in chili peppers that has pain-relieving and anti-inflammatory properties. Here, we report that nanoparticles containing capsaicin and iron (Fe-CAP NPs) exhibited anti-inflammatory effects in the treatment of ALI.

Methods

The morphological characteristics of nanozymes were detected. RAW 264.7 cells were divided into four groups: control, lipopolysaccharide (LPS), CAP+LPS and Fe-CAP+LPS groups. The expression of inducible nitric oxide synthase (iNOS), transforming growth factor-β (TGF-β), and tumor necrosis factor-α (TNF-α) was assessed by immunofluorescence, Western blot, and enzyme-linked immunosorbent assay (ELISA). Nuclear factor kappa-B (NF-κB) expression was determined by Western blot. C57 mice were divided into control, LPS, CAP+LPS and Fe-CAP+LPS groups. Interleukin-6 (IL-6) and iNOS expression in the lung was detected by Western Blot. IL-6 and TNF-α expression in serum was detected by ELISA. Extravasated Evans blue, histopathological evaluation and wet-to-dry (W/D) weight ratio were used to assess pulmonary capillary permeability. The blood and major organs (heart, liver, spleen, lung and kidney) of mice were tested for the toxicity of Fe-CAP NPs.

Results

In the LPS group, TNF-α, iNOS, p-NF-κB and p-IKBα expression increased. However, their expression was significantly decreased in the Fe-CAP+LPS group. TGF-β expression showed the opposite trend. In vivo, IL-6 and iNOS expression was notably increased in the lungs of LPS group of mice but decreased with Fe-CAP pretreatment. Fe-CAP significantly ameliorated lung EB leakage, improved the histopathology of lung tissue and reduced the W/D weight ratio. The nanoparticles showed non-cytotoxicity, when studying these biological activities.

Conclusion

Fe-CAP NPs could alleviated inflammation by inhibiting the expression of pro-inflammatory factors in macrophages, increasing the expression of anti-inflammatory factors, and alleviating lung tissue damage.

Copper incorporated biomaterial-based technologies for multifunctional wound repair

The treatment of wounds is a worldwide challenge, and wound infection can affect the effectiveness of wound treatment and further increase the disease burden. Copper is an essential trace element that has been shown to have broad-spectrum antibacterial effects and to be involved in the inflammation, proliferation, and remodeling stages of wound healing. Compared to treatments such as bioactive factors and skin grafts, copper has the advantage of being low-cost and easily available, and has received a lot of attention in wound healing. Recently, biomaterials made by incorporating copper into bioactive glasses, polymeric scaffolds and hydrogels have been used to promote wound healing by the release of copper ions. In addition, copper-incorporated biomaterials with catalytic, photothermal, and photosensitive properties can also accelerate wound healing through antibacterial and wound microenvironment regulation. This review summarizes the antibacterial mechanisms of copper- incorporated biomaterials and their roles in wound healing, and discusses the current challenges. A comprehensive understanding of the role of copper in wounds will help to facilitate new preclinical and clinical studies, thus leading to the development of novel therapeutic tools.

The One-Stop Integrated Nanoagent Based on Photothermal Therapy for Deep Infection Healing and Inflammation Inhibition

Chronic wounds caused by bacterial infections are a major challenge in medical fields. The hypoxia condition extremely induces reactive oxygen species (ROS) generation and upregulates the expression of hypoxia-inducible factor, both of which can increase the pro-inflammatory M1 subtype macrophages production while reducing the anti-inflammatory M2 subtype macrophages. Besides, bacteria-formed biofilms can hinder the penetration of therapeutic agents. Encouraged by natural motors automatically executing tasks, hypothesized that supplying sufficient oxygen (O2 ) would simultaneously drive therapeutic agent movement, rescue the hypoxic microenvironment, and disrupt the vicious cycle of inflammation. Here, small organic molecule-based nanoparticles (2TT-mC6B@Cu5.4 O NPs) that possess high photothermal conversion efficiency and enzymatic activities are developed, including superoxide dismutase-, catalase-, and glutathione peroxidase-like activity. 2TT-mC6B@Cu5.4 O NPs exhibit superior ROS-scavenging and O2 production abilities that synergistically relieve inflammation, alleviate hypoxia conditions, and promote their deep penetration in chronic wound tissues. Transcriptome analysis further demonstrates that 2TT-mC6B@Cu5.4O NPs inhibit biological activities inside bacteria. Furthermore, in vivo experiments prove that 2TT-mC6B@Cu5.4 O NPs-based hyperthermia can effectively eliminate bacteria in biofilms to promote wound healing.

Recent Development of Copper-Based Nanozymes for Biomedical Applications

Copper (Cu), an indispensable trace element within the human body, serving as an intrinsic constituent of numerous natural enzymes, carrying out vital biological functions. Furthermore, nanomaterials exhibiting enzyme-mimicking properties, commonly known as nanozymes, possess distinct advantages over their natural enzyme counterparts, including cost-effectiveness, enhanced stability, and adjustable performance. These advantageous attributes have captivated the attention of researchers, inspiring them to devise various Cu-based nanomaterials, such as copper oxide, Cu metal-organic framework, and CuS, and explore their potential in enzymatic catalysis. This comprehensive review encapsulates the most recent advancements in Cu-based nanozymes, illuminating their applications in the realm of biochemistry. Initially, it is delved into the emulation of typical enzyme types achieved by Cu-based nanomaterials. Subsequently, the latest breakthroughs concerning Cu-based nanozymes in biochemical sensing, bacterial inhibition, cancer therapy, and neurodegenerative diseases treatment is discussed. Within this segment, it is also explored the modulation of Cu-based nanozyme activity. Finally, a visionary outlook for the future development of Cu-based nanozymes is presented.

Recent Progress in antibacterial hydrogel coatings for targeting biofilm to prevent orthopedic implant-associated infections

The application of orthopedic implants for bone tissue reconstruction and functional restoration is crucial for patients with severe bone fractures and defects. However, the abiotic nature of orthopedic implants allows bacterial adhesion and colonization, leading to the formation of bacterial biofilms on the implant surface. This can result in implant failure and severe complications such as osteomyelitis and septic arthritis. The emergence of antibiotic-resistant bacteria and the limited efficacy of drugs against biofilms have increased the risk of orthopedic implant-associated infections (OIAI), necessitating the development of alternative therapeutics. In this regard, antibacterial hydrogels based on bacteria repelling, contact killing, drug delivery, or external assistance strategies have been extensively investigated for coating orthopedic implants through surface modification, offering a promising approach to target biofilm formation and prevent OIAI. This review provides an overview of recent advancements in the application of antibacterial hydrogel coatings for preventing OIAI by targeting biofilm formation. The topics covered include: (1) the mechanisms underlying OIAI occurrence and the role of biofilms in exacerbating OIAI development; (2) current strategies to impart anti-biofilm properties to hydrogel coatings and the mechanisms involved in treating OIAI. This article aims to summarize the progress in antibacterial hydrogel coatings for OIAI prevention, providing valuable insights and facilitating the development of prognostic markers for the design of effective antibacterial orthopedic implants.

Hollow Mesoporous Molybdenum Single-Atom Nanozyme-Based Reactor for Enhanced Cascade Catalytic Antibacterial Therapy

Purpose

The remarkable peroxidase-like activity of single-atom nanozymes (SAzymes) allows them to catalyze the conversion of H2O2 to •OH, rendering them highly promising for antibacterial applications. However, their practical in vivo application is hindered by the near-neutral pH and insufficient H2O2 levels present in physiological systems. This study was aimed at developing a SAzyme-based nanoreactor and investigating its in vivo antibacterial activity.

Methods

We developed a hollow mesoporous molybdenum single-atom nanozyme (HMMo-SAzyme) using a controlled chemical etching approach and pyrolysis strategy. The HMMo-SAzyme not only exhibited excellent catalytic activity but also served as an effective nanocarrier. By loading glucose oxidase (GOx) with HMMo-SAzyme and encapsulating it with hyaluronic acid (HA), a nanoreactor (HMMo/GOx@HA) was constructed as glucose-triggered cascade catalyst for combating bacterial infection in vivo.

Results

Hyaluronidase (HAase) at the site of infection degraded HA, allowing GOx to convert glucose into gluconic acid and H2O2. An acid environment significantly enhanced the catalytic activity of HMMo-SAzyme to promote the further catalytic conversion of H2O2 to •OH for bacterial elimination. In vitro and in vivo experiments demonstrated that the nanoreactor had excellent antibacterial activity and negligible biological toxicity.

Conclusion

This study represents a significant advancement in developing a cascade catalytic system with high efficiency based on hollow mesoporous SAzyme, promising the advancement of biological applications of SAzyme.

CuFe Layered Double Hydroxide as Self-Cascade Nanoreactor for Efficient Antibacterial Therapy

Nanozyme-induced reactive oxygen species (ROS)-dependent catalytic therapy has been developed into a powerful strategy against bacterial wound infections. However, the limited endogenous supply or instability of H2O2, the reliance on external stimuli for the generation of ROS, and the highly expressed glutathione (GSH) level make it a challenge to achieve high-performance therapeutic efficiency. In this work, a facile therapeutic strategy against bacterial infections with pristine CuFe layered double hydroxide (LDH) as the self-cascade nanoreactor is proposed without modification or additional energy input. CuFe LDH with an oxidase-like feature can catalyze the generation of multiple ROS, such as 1O2, ·O2-, and H2O2. And the self-generated H2O2 in the cascade nanoreactor could be further in situ transformed to ·OH owing to the peroxidase-like activity. As a result, the cell membrane of bacteria is destroyed, leading to death. Furthermore, its ultrahigh enzyme-like activity of CuFe LDH could effectively promote the breakdown of the biofilm structure. Additionally, the Cu2+-mediated GSH exhaustion of CuFe LDH further avoids the consumption of oxidized ROS and thereby significantly improves the sterilization effect. Finally, the as-prepared CuFe LDH with negligible side effects on normal tissues can be successfully used to eliminate the methicillin-resistant Staphylococcus aureus-infected wounds and accelerate their healing in the mouse model, which paves a new avenue as an antibacterial agent for clinical anti-infective treatment.

Injectable and photothermal antibacterial bacterial cellulose cryogel for rapid hemostasis and repair of irregular and deep skin wounds

For irregular and deep skin wounds, it's difficult for wound dressing to reach the injured site to achieve rapid hemostasis and provide wound protection. Bacterial cellulose (BC) has high strength and natural three-dimensional pore structure, which endows it shape recovery ability after absorbing blood when injected to the wound. Therefore, in the study, an injectable aldehyde bacterial cellulose/polydopamine (DBC/PDA) photothermal cryogel was prepared by oxidation polymerization method for hemostasis and repair of irregular and deep skin wounds. BC was oxidized by NaIO4 to form DBC and dopamine (DA) was introduced into DBC by reacting with the aldehyde group in DBC through Schiff base reaction. Under oxidation effect of NaIO4 and with freezing condition, water crystallization led to local aggregation of DA and DBC, and at the same time DA was oxidized to PDA and polymerized with DA on DBC. After the melting process, the porous cryogel was obtained. The introduction of PDA enhances the photothermal properties of DBC/PDA cryogel. DBC/PDA cryogel can kill most bacteria and provide wound protection under near-infrared light. In vitro and in vivo hemostatic tests show that the DBC/PDA cryogel can quickly absorb blood and stop bleeding. Combined with its good injectable, DBC/PDA cryogel can provide rapid hemostatic and protection in the face of irregular and deep skin wounds.