Bienzymatic synergism of vanadium oxide nanodots to efficiently eradicate drug-resistant bacteria during wound healing in vivo

Cell Wall Binding Strategies Based on Cu3SbS3 Nanoparticles for Selective Bacterial Elimination and Promotion of Infected Wound Healing

Utilizing nanomaterials as an alternative to antibiotics, with a focus on maintaining high biosafety, has emerged as a promising strategy to combat antibiotic resistance. Nevertheless, the challenge lies in the indiscriminate attack of nanomaterials on both bacterial and mammalian cells, which limits their practicality. Herein, Cu3SbS3 nanoparticles (NPs) capable of generating reactive oxygen species (ROS) are discovered to selectively adsorb and eliminate bacteria without causing obvious harm to mammalian cells, thanks to the interaction between O of N-acetylmuramic acid in bacterial cell walls and Cu of the NPs. Coupled with the short diffusion distance of ROS in the surrounding medium, a selective antibacterial effect is achieved. Additionally, the antibacterial mechanism is then identified: Cu3SbS3 NPs catalyze the generation of O2•-, which has subsequently been conversed by superoxide dismutase to H2O2. The latter is secondary catalyzed by the NPs to form •OH and 1O2, initiating an in situ attack on bacteria. This process depletes bacterial glutathione in conjunction with the disruption of the antioxidant defense system of bacteria. Notably, Cu3SbS3 NPs are demonstrated to efficiently impede biofilm formation; thus, a healing of MRSA-infected wounds was promoted. The bacterial cell wall-binding nanoantibacterial agents can be widely expanded through diversified design.

The potential use of nanozymes as an antibacterial agents in oral infection, periodontitis, and peri-implantitis

Several studies suggest that oral pathogenic biofilms cause persistent oral infections. Among these is periodontitis, a prevalent condition brought on by plaque biofilm. It can even result in tooth loss. Furthermore, the accumulation of germs around a dental implant may lead to peri-implantitis, which damages the surrounding bone and gum tissue. Furthermore, bacterial biofilm contamination on the implant causes soft tissue irritation and adjacent bone resorption, severely compromising dental health. On decontaminated implant surfaces, however, re-osseointegration cannot be induced by standard biofilm removal techniques such as mechanical cleaning and antiseptic treatment. A family of nanoparticles known as nanozymes (NZs) comprise highly catalytically active multivalent metal components. The most often employed NZs with antibacterial activity are those that have peroxidase (POD) activity, among other types of NZs. Since NZs are less expensive, more easily produced, and more stable than natural enzymes, they hold great promise for use in various applications, including treating microbial infections. NZs have significantly contributed to studying implant success rates and periodontal health maintenance in periodontics and implantology. An extensive analysis of the research on various NZs and their applications in managing oral health conditions, including dental caries, dental pulp disorders, oral ulcers, peri-implantitis, and bacterial infections of the mouth. To combat bacteria, this review concentrates on NZs that imitate the activity of enzymes in implantology and periodontology. With a view to the future, there are several ways that NZs might be used to treat dental disorders antibacterially.

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.

Multienzyme-Like Nanozymes: Regulation, Rational Design, and Application

Nanomaterials with more than one enzyme-like activity are termed multienzymic nanozymes, and they have received increasing attention in recent years and hold huge potential to be applied in diverse fields, especially for biosensing and therapeutics. Compared to single enzyme-like nanozymes, multienzymic nanozymes offer various unique advantages, including synergistic effects, cascaded reactions, and environmentally responsive selectivity. Nevertheless, along with these merits, the catalytic mechanism and rational design of multienzymic nanozymes are more complicated and elusive as compared to single-enzymic nanozymes. In this review, the multienzymic nanozymes classification scheme based on the numbers/types of activities, the internal and external factors regulating the multienzymatic activities, the rational design based on chemical, biomimetic, and computer-aided strategies, and recent progress in applications attributed to the advantages of multicatalytic activities are systematically discussed. Finally, current challenges and future perspectives regarding the development and application of multienzymatic nanozymes are suggested. This review aims to deepen the understanding and inspire the research in multienzymic nanozymes to a greater extent.

Enhancing diabetic wound healing with a pH-responsive nanozyme hydrogel featuring multi-enzyme-like activities and oxygen self-supply

Diabetic wound treating remains a challenging due to bacterial infections, oxidative stress, tissue hypoxia, and high glucose levels. Herein, a multi-enzyme-like activities nanocomposite (Mo,Fe/Cu,I-Ag@GOx) was designed and anchored to a multifunctional fluorescence hydrogel. The nanozyme gel, loaded with glucose-oxidase (GOx), exhibits intrinsic GOx, peroxidase (POD)-, oxidase (OXD)-, catalase (CAT)- and superoxide dismutase (SOD)-like activities with pH-switchable glucose-initiated cascade reaction for diabetic wound healing. In the first cascade-reaction, initiated by GOx, the nanozyme gel catalyzes glucose and O2 into gluconic acid and H2O2 to further generate superoxide anion radical (O2·-) and hydroxyl radicals (·OH) to eradicate bacteria. In the second cascade-reaction, as the wound pH changes alkalescent microenvironment, the nanozyme gel simulates SOD to transform O2·- into O2 and H2O2, and then decomposes endogenous and exogenous H2O2 into O2 via CAT-like activity to reduce oxidative stress and alleviate hypoxia. The gel by calcium ion (Ca2+) cross-linked sodium alginate (SA) and chitosan (CS) containing nanozyme was constructed with injectability, adhesion and fluorescence properties, as well as beneficial biocompatible. Importantly, the water/alcohol solubility of the nanozyme gel allows it to be used as a dressing without causing secondary injury to the wound. The multifunctional fluorescence hydrogel exhibits efficiently promote pro-angiogenesis and bacteria-infected wound healing.

The mechanism of nanozyme activity of ZnO-Co3O4-v: Oxygen vacancy dynamic change and bilayer electron transfer pathway for wound healing and virtual reality revealing

Since the catalyst's surface was the major active location, the inner structure's contribution to catalytic activity was typically overlooked. Here, ZnO-Co3O4-v nanozymes with several surfaces and bulk oxygen vacancies were created. The O atoms of H2O2 moved inward to preferentially fill the oxygen vacancies in the interior and form new "lattice oxygen" by the X-ray photoelectron spectroscopy depth analysis and X-ray absorption fine structure. The internal Co2+ continually transferred electrons to the surface for a continuous catalytic reaction, which generated a significant amount of reactive oxygen species. Inner and outer double-layer electron cycles accompanied this process. A three-dimensional model of ZnO-Co3O4-v was constructed using virtual reality interactive modelling technology to illustrate nanozyme catalysis. Moreover, the bactericidal rate of ZnO-Co3O4-v for Methionine-resistant Staphylococcus aureus and Multiple drug resistant Escherichia coli was as high as 99%. ZnO-Co3O4-v was biocompatible and might be utilized to heal wounds following Methionine-resistant Staphylococcus aureus infection. This work offered a new idea for nanozymes to replace of conventional antibacterial medications.

Biomimetic and bioorthogonal nanozymes for biomedical applications

Nanozymes mimic the function of enzymes, which drive essential intracellular chemical reactions that govern biological processes. They efficiently generate or degrade specific biomolecules that can initiate or inhibit biological processes, regulating cellular behaviors. Two approaches for utilizing nanozymes in intracellular chemistry have been reported. Biomimetic catalysis replicates the identical reactions of natural enzymes, and bioorthogonal catalysis enables chemistries inaccessible in cells. Various nanozymes based on nanomaterials and catalytic metals are employed to attain intended specific catalysis in cells either to mimic the enzymatic mechanism and kinetics or expand inaccessible chemistries. Each nanozyme approach has its own intrinsic advantages and limitations, making them complementary for diverse and specific applications. This review summarizes the strategies for intracellular catalysis and applications of biomimetic and bioorthogonal nanozymes, including a discussion of their limitations and future research directions.

Recent Advances in Nanozyme-Mediated Strategies for Pathogen Detection and Control

Pathogen detection and control have long presented formidable challenges in the domains of medicine and public health. This review paper underscores the potential of nanozymes as emerging bio-mimetic enzymes that hold promise in effectively tackling these challenges. The key features and advantages of nanozymes are introduced, encompassing their comparable catalytic activity to natural enzymes, enhanced stability and reliability, cost effectiveness, and straightforward preparation methods. Subsequently, the paper delves into the detailed utilization of nanozymes for pathogen detection. This includes their application as biosensors, facilitating rapid and sensitive identification of diverse pathogens, including bacteria, viruses, and plasmodium. Furthermore, the paper explores strategies employing nanozymes for pathogen control, such as the regulation of reactive oxygen species (ROS), HOBr/Cl regulation, and clearance of extracellular DNA to impede pathogen growth and transmission. The review underscores the vast potential of nanozymes in pathogen detection and control through numerous specific examples and case studies. The authors highlight the efficiency, rapidity, and specificity of pathogen detection achieved with nanozymes, employing various strategies. They also demonstrate the feasibility of nanozymes in hindering pathogen growth and transmission. These innovative approaches employing nanozymes are projected to provide novel options for early disease diagnoses, treatment, and prevention. Through a comprehensive discourse on the characteristics and advantages of nanozymes, as well as diverse application approaches, this paper serves as a crucial reference and guide for further research and development in nanozyme technology. The expectation is that such advancements will significantly contribute to enhancing disease control measures and improving public health outcomes.

Activity Regulating Strategies of Nanozymes for Biomedical Applications

On accounts of the advantages of inherent high stability, ease of preparation and superior catalytic activities, nanozymes have attracted tremendous potential in diverse biomedical applications as alternatives to natural enzymes. Optimizing the activity of nanozymes is significant for widening and boosting the applications into practical level. As the research of the catalytic activity regulation strategies of nanozymes is boosting, it is essential to timely review, summarize, and analyze the advances in structure-activity relationships for further inspiring ingenious research into this prosperous area. Herein, the activity regulation methods of nanozymes in the recent 5 years are systematically summarized, including size and morphology, doping, vacancy, surface modification, and hybridization, followed by a discussion of the latest biomedical applications consisting of biosensing, antibacterial, and tumor therapy. Finally, the challenges and opportunities in this rapidly developing field is presented for inspiring more and more research into this infant yet promising area.

A multi-enzyme-like activity exhibiting mussel-inspired nanozyme hydrogel for bacteria-infected wound healing

Bacterial infection, tissue hypoxia, and inflammatory and oxidative stress are several key problems in wound healing of chronic infections. Herein, a multi-enzyme-like activity exhibiting multifunctional hydrogel made up of mussel-inspired carbon dot reduced-Ag (CDs/AgNPs) and Cu/Fe-nitrogen-doped carbon (Cu,Fe-NC) was designed. Due to the loss of glutathione (GSH) and oxidase (OXD)-like activity of the nanozyme (decomposes O₂ to generate a superoxide anion radical (O₂˙^-) and hydroxyl radical production (˙OH)), the multifunctional hydrogel exhibited excellent antibacterial performance. More importantly, during the bacterial elimination within the inflammatory phase of wound healing, the hydrogel could act as a catalase (CAT)-like agent to supply adequate O₂ by catalyzing intracellular H₂O₂ for hypoxia abatement. The catechol groups on the CDs/AgNPs endowed them with the dynamic redox equilibrium properties of phenol-quinones, thus providing the hydrogel with mussel-like adhesion properties. The multifunctional hydrogel was shown to excellently promote bacterial infection wound healing and maximize the efficiency of nanozymes.

All-in-one smart dressing for simultaneous angiogenesis and neural regeneration

Wound repair, along with skin appendage regeneration, is challenged by insufficient angiogenesis and neural regeneration. Therefore, promoting both proangiogenic and neuro-regenerative therapeutic effects is essential for effective wound repair. However, most therapeutic systems apply these strategies separately or ineffectively. This study investigates the performance of an all-in-one smart dressing (ASD) that integrates angiogenic functional materials and multiple biological factors within a light crosslinked hydrogel, forming a multi-functional dressing capable of facilitating simultaneous micro-vascularization and neural regeneration. The ASD uses a zeolite-imidazolate framework 67 with anchored vanadium oxide (VO₂@ZIF-67) that allows for the on-demand release of Co²⁺ with fluctuations in pH at the wound site to stimulate angiogenesis. It can simultaneously release CXCL12, ligustroflavone, and ginsenoside Rg1 in a sustained manner to enhance the recruitment of endogenous mesenchymal stem cells, inhibit senescence, and induce neural differentiation to achieve in situ nerve regeneration. The ASD can stimulate rapid angiogenesis and nerve regeneration within 17 days through multiple angiogenic and neuro-regenerative cues within one dressing. This study provides a proof-of-concept for integrating functional nanomaterials and multiple complementary drugs within a smart dressing for simultaneous angiogenesis and neural regeneration.

ZIF@VO2 as an Intelligent Nano-Reactor for On-Demand Angiogenesis and Disinfection

Absent angiogenesis and bacterial infection are two major challenges that simultaneously delay the repair of injured tissues and organs. However, most current therapeutic systems deliver therapeutic cues in a separate and inaccurate manner which stimulates angiogenesis or inhibits infection leading to limited repair and side effects. Advanced therapeutic systems capable of providing accurate angiogenic stimulation and anti-infection signals in response to the changing microenvironment are urgently needed. Herein, a nano-reactor (ZFVO) involving zeolitic imidazolate framework-67 (ZIF-67)-deposited hollow vanadium oxide (VO₂ ) is developed to intelligently execute pro-angiogenesis and/or disinfection via the responsive release of cobalt ions and hydroxyl radicals to the injury and infection sites, respectively. ZFVO nano-reactor demonstrates a novel strategy for constructing drug-free nano-platforms with a hierarchical structure which has potential for the accurate treatment of trauma and orthopedic diseases.

Liquid exfoliation of V8C7 nanodots as peroxidase-like nanozymes for photothermal-catalytic synergistic antibacterial treatment

Nanozymes are effective antibiotics that use reactive oxygen species (ROS) produced by Fenton/Fenton-like reactions to kill bacteria. However, its activity is still not satisfactory and requires large amounts of hydrogen peroxide (H₂O₂) with side effects on normal tissues. Herein, ultrasmall V₈C₇ nanodots (NDs) are successfully constructed by the liquid-phase exfoliation method for photothermal-catalytic synergistic antibacterial treatment. The prepared V₈C₇ NDs are horseradish peroxidase (HRP)-like nanozymes that can efficiently catalyze H₂O₂ to produce a large amount of ROS. Unlike traditional HRP-like nanozymes, V₈C₇ NDs can have a good catalytic effect under slightly acidic conditions (pH=5.5). Moreover, V₈C₇ NDs have good near-infrared (NIR) absorption and high photothermal conversion efficiency (PTCE, 50.39%), which can be used for photothermal treatment (PTT) of bacteria. In addition, the mild photothermal effect can further enhance the HRP-like catalytic activity of V₈C₇ NDs, thereby further enhancing the antibacterial performance of V₈C₇ NDs. In vitro results show that V₈C₇ NDs can effectively eradicate Escherichia coli (E. coli, gram-negative) and methicillin-resistant Staphylococcus aureus (MRSA, gram-positive) under laser irradiation and the presence of H₂O₂, possessing spectral antibacterial properties. More importantly, V₈C₇ NDs display satisfactory therapeutic effects on wounds infected by MRSA in vivo, and their toxicity is negligible, suggesting that they may have great potential for application as powerful and safe antibacterial agents. This work presents a practical antibacterial strategy by combining PTT and catalytic therapy to achieve efficient treatment of bacteria-infected wounds. STATEMENT OF SIGNIFICANCE: (1) Ultrasmall V₈C₇ NDs were prepared by the liquid-phase exfoliation method. (2) V₈C₇ NDs showed good photothermal, catalytic properties. (3) V₈C₇ NDs achieved satisfactory photothermal-catalytic synergistic antibacterial treatment.

Self-template synthesis of mesoporous vanadium oxide nanospheres with intrinsic peroxidase-like activity and high antibacterial performance

Mesoporous vanadium oxide nanospheres are a very promising nanozyme for antibacterial and chemical sensing. However, controllable synthesis of mesoporous vanadium oxide nanospheres with uniform structure and small diameter (<200 nm) remains challenging. Herein, mesoporous vanadium oxide nanospheres (MVONs) with a small, uniform and adjustable particle size (52-105 nm), large mesopore size (5.1-5.8 nm), and high specific surface area (up to 63.7 m² g^-1) are constructed via a self-template strategy using tannic acid, formaldehyde and vanadium compounds as a polymerizable ligand, cross-linking agent and metal source, respectively. The relationships between synthesis conditions and material nanostructure are systematically investigated. The particle size and peroxidase-like activity of MVONs can be easily changed by adding different amounts of Pluronic block copolymer F127. Owing to the mesoporous structure, high specific surface area and small particle size, MVONs can effectively convert H₂O₂ into extremely toxic reactive oxygen species, and further kill Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). This research establishes a universal, reliable method for synthesizing mesoporous vanadium oxide nanospheres, which might be used in catalysis, biosensors, and antibacterial treatment.

Charge-Switchable CuxO Nanozyme with Peroxidase and Near-Infrared Light Enhanced Photothermal Activity for Wound Antibacterial Application

Bacterial infection is still a thorny problem threatening human health, and nanozymes offer a promising alternative strategy to combat the health threat posed by bacterial infection. However, the antibacterial efficacies of nanozymes are unsatisfactory because of low catalytic activity of nanozymes and their inability to trap bacteria. Herein, a multifunctional nanozyme, polydopamine (PDA)-modified copper oxide (Cu_xO-PDA) is designed to overcome this challenge. Cu_xO-PDA showed peroxidase-mimicking activity and the catalytic activity was enhanced upon near-infrared (NIR) irradiation. Cu_xO-PDA was negatively charged under neutral or alkaline condition and showed no obvious peroxidase-mimicking activity. On the contrary, the surface charge of Cu_xO-PDA can be switched to positive under acidic conditions, which can target negatively charged bacteria. More interestingly, well-dispersed Cu_xO-PDA can aggregate rapidly under NIR irradiation, which trapped the bacteria and nanozymes together. It was found that shortening the distance between nanozyme and bacteria could improve the antibacterial effect. The obtained Cu_xO-PDA can cause DNA degradation, lipid peroxidation, and biofilm eradication. Cu_xO-PDA showed good antibacterial effect against two kinds of representative bacteria, Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). The experiment in vivo further proved favorable antibacterial activity of Cu_xO-PDA nanozyme.

Nanozybiotics: Nanozyme-Based Antibacterials against Bacterial Resistance

Infectious diseases caused by bacteria represent a global threat to human health. However, due to the abuse of antibiotics, drug-resistant bacteria have evolved rapidly and led to the failure of antibiotics treatment. Alternative antimicrobial strategies different to traditional antibiotics are urgently needed. Enzyme-based antibacterials (Enzybiotics) have gradually attracted interest owing to their advantages including high specificity, rapid mode-of-action, no resistance development, etc. However, due to their low stability, potential immunogenicity, and high cost of natural enzymes, enzybiotics have limitations in practical antibacterial therapy. In recent years, many nanomaterials with enzyme-like activities (Nanozymes) have been discovered as a new generation of artificial enzymes and perform catalytic antibacterial effects against bacterial resistance. To highlight the progress in this field of nanozyme-based antibacterials (Nanozybiotics), this review discussed the antibacterial mechanism of action of nanozybiotics with a comparison with enzybiotics. We propose that nanozybiotics may bear promising applications in antibacterial therapy, due to their high stability, rapid bacterial killing, biofilm elimination, and low cost.

Catalytic antimicrobial therapy using nanozymes

Nanozymes are nanomaterials with enzyme-like characteristics, which catalyze the conversion of enzyme substrates and follow enzymatic kinetics under physiological conditions. As a new generation of artificial enzymes, nanozymes provide alternative approaches for those upon enzymatic catalysis. Compared with natural enzymes, nanozymes have the advantages of simple preparation, good stability and low cost, which makes nanozymes promising for application in many fields, such as antimicrobial infection treatment. Many studies have reported that nanozymes are capable of killing a number of pathogenic bacteria with resistance, fungi as well as viruses, and have shown great curative effects for diseases caused by these pathogens. Herein, we summarize the application of nanozymes for antibacterial, antiviral, and antifungal therapies and outline the issues needing resolution in the future. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Metal-Organic Framework Modified MoS2 Nanozyme for Synergetic Combating Drug-Resistant Bacterial Infections via Photothermal Effect and Photodynamic Modulated Peroxidase-Mimic Activity

Bacterial infections have become major threats to public health all over the world. With the emergence of antibiotic resistance, it is urgent to develop novel antimicrobial materials to efficiently overcome drug resistance with high bactericidal activity. In this work, UiO-66-NH-CO-MoS₂ nanocomposites (UNMS NCs) are constructed through the amidation reaction. The UNMS NCs are positively charged which is beneficial for capturing and restricting bacteria. Significantly, UNMS NCs possess a synergistic bactericidal efficiency based on near-infrared irradiation (808 nm) regulated combination of photothermal, photodynamic, and peroxidase-like enzymatic activities. Both the photodynamic property and nanozymatic activity of UNMS NCs can lead to the generation of reactive oxygen species. The UNMS NCs show high catalytic activity in a wide pH range and exhibit excellent antibacterial ability against ampicillin-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus with negligible cytotoxicity. Interestingly, due to the 808 nm irradiation-induced hyperthermia in the presence of UNMS NCs, the glutathione oxidation process can be accelerated, resulting in bacterial death more easily. Mice wound models are established to further manifest that UNMS NCs can promote wound healing with good biosafety in living systems.

Recent Advances in Nanozymes for Bacteria-Infected Wound Therapy

Bacterial-infected wounds are a serious threat to public health. Bacterial invasion can easily delay the wound healing process and even cause more serious damage. Therefore, effective new methods or drugs are needed to treat wounds. Nanozyme is an artificial enzyme that mimics the activity of a natural enzyme, and a substitute for natural enzymes by mimicking the coordination environment of the catalytic site. Due to the numerous excellent properties of nanozymes, the generation of drug-resistant bacteria can be avoided while treating bacterial infection wounds by catalyzing the sterilization mechanism of generating reactive oxygen species (ROS). Notably, there are still some defects in the nanozyme antibacterial agents, and the design direction is to realize the multifunctionalization and intelligence of a single system. In this review, we first discuss the pathophysiology of bacteria infected wound healing, the formation of bacterial infection wounds, and the strategies for treating bacterially infected wounds. In addition, the antibacterial advantages and mechanism of nanozymes for bacteria-infected wounds are also described. Importantly, a series of nanomaterials based on nanozyme synthesis for the treatment of infected wounds are emphasized. Finally, the challenges and prospects of nanozymes for treating bacterial infection wounds are proposed for future research in this field.

Nanodots Derived from Layered Materials: Synthesis and Applications

Layered 2D materials, such as graphene, transition metal dichalcogenides, transition metal oxides, black phosphorus, graphitic carbon nitride, hexagonal boron nitride, and MXenes, have attracted intensive attention over the past decades owing to their unique properties and wide applications in electronics, catalysis, energy storage, biomedicine, etc. Further reducing the lateral size of layered 2D materials down to less than 10 nm allows for preparing a new class of nanostructures, namely, nanodots derived from layered materials. Nanodots derived from layered materials not only can exhibit the intriguing properties of nanodots due to the size confinement originating from the ultrasmall size, but also can inherit some unique properties of ultrathin layered 2D materials, making them promising candidates in a wide range of applications, especially in biomedicine and catalysis. Here, a comprehensive summary on the materials categories, advantages, synthesis methods, and potential applications of these nanodots derived from layered materials is provided. Finally, personal insights about the challenges and future directions in this promising research field are also given.

Synergistical Starvation and Chemo-Dynamic Therapy for Combating Multidrug-Resistant Bacteria and Accelerating Diabetic Wound Healing

The application of the antibiotic drug has dramatically decreased the infection and promoted the development of surgery, but drug-resistant bacteria appeared along with the abuse of antibiotics. Especially, wound in diabetic patients provides more glucose for bacteria resulting in poor wound healing. Therefore, it is imminent to explore advanced agents for combating multidrug-resistant bacteria and accelerating diabetic wound healing. Herein, metal-organic frameworks based nanoreactors loaded with glucose oxidase (GOx) and peroxidase-like bovine hemoglobin (BHb) are designed to construct an effective cascaded catalytic antibacterial system. Therein, GOx can cost the glucose, and release H₂ O₂ simultaneously, which can then be transformed into hydroxyl radicals by BHb. As a result, the as-prepared nanoreactors can play the roles of both starving and killing toward the multidrug-resistant bacteria. Furthermore, the produced gluconic acid can reduce the pH of working condition, which is beneficial for both the enhancement of peroxidase activity and the inhibition of the bacteria growth. More importantly, the constructed nanoreactors can be degraded and excreted from the body in the form of feces, which render the as-proposed nanoreactors qualified as effective and safe materials for both combating multidrug-resistant bacteria in vitro and accelerating the diabetic wound healing in vivo of the mouse model.

Antipathogenic properties and applications of low-dimensional materials

A major health concern of the 21st century is the rise of multi-drug resistant pathogenic microbial species. Recent technological advancements have led to considerable opportunities for low-dimensional materials (LDMs) as potential next-generation antimicrobials. LDMs have demonstrated antimicrobial behaviour towards a variety of pathogenic bacterial and fungal cells, due to their unique physicochemical properties. This review provides a critical assessment of current LDMs that have exhibited antimicrobial behaviour and their mechanism of action. Future design considerations and constraints in deploying LDMs for antimicrobial applications are discussed. It is envisioned that this review will guide future design parameters for LDM-based antimicrobial applications.

In vivo guiding inorganic nanozymes for biosensing and therapeutic potential in cancer, inflammation and microbial infections

Researchers have recently introduced some artificial enzymes based on nanomaterials that show significant catalytic activity relative to native enzymes called nanozyme. These nanozymes show superior performance than conventional catalysts and are considered as fascinating candidates for introducing the next generation of biomaterials in various industrial and biomedical fields. Recently, nanozymes have received a great deal of attention in biomedical applications due to their potential properties such as long-term stability, low cost, mass production capability, and controllable catalytic activity. Due to the intrinsic catalytic activity of nanoparticles (NPs) as nanozymes and their ability to be regulated in biomedical processes, this review paper focuses on the in vivo applications of nanozymes in biosensing and therapeutic activities. Despite the challenges and benefits of each approach, this paper attempts to provide an appropriate motivation for the classification of different nanozymes followed by their application in biomedical activities including in vivo biosensing and therapeutic potential in cancer, inflammation and microbial infections. Finally, some ongoing challenges and future perspective of nanozymes in biomedical application were surveyed. In conclusion, this paper may provide useful information regarding the development of nanozymes as promising platforms in biomedical settings due to expedited diagnosis, the advancement of multifactorial therapies and their pronounced stability.

Nanozyme-based medicine for enzymatic therapy: progress and challenges

Nanozymes are nanomaterials with enzyme-like characteristics. As a new generation of artificial enzymes, nanozymes have the advantages of low cost, good stability, simple preparation, and easy storage, allowing them to overcome many of the limitations of natural enzymes in enzymatic therapy. Currently, most reported nanozymes exhibit oxidoreductase-like activities and can regulate redox balance in cells. Nanozymes with superoxide dismutase and catalase activity can be used to scavenge reactive oxygen species (ROS) for cell protection, while those with peroxidase and oxidase activity can generate ROS to kill harmful cells, such as tumor cells and bacteria. In this review, we summarize recent progress in nanozyme-based medicine for enzymatic therapy and highlight the opportunities and challenges in this field for future study.

Molybdenum disulfide-based materials with enzyme-like characteristics for biological applications

Nanozyme, a kind of nanomaterials with enzymatic activity, has been developing vigorously over the past years owing to its advantages such as low-cost, easy storage, ease of use in harsh environments and so on, compared with natural enzymes. At present, as a typical two-dimensional nanomaterial, molybdenum disulfide (MoS₂) and their hybrids with unexpected enzyme-like activities have caused wide attention. In this review, we mainly investigated the enzyme-like activities of MoS₂ based nanomaterials, including peroxidase-like activity, catalase-like activity and superoxide dismutase-like activity. Furthermore, we systematically introduce recent research progress of MoS₂ based nanomaterials in the fields of biological applications such as radiation protection, cancer therapy, antibacterial, and wound healing. Finally, the current challenges and perspectives of MoS₂ based nanomaterials in the future are also discussed and proposed. We expect this review may be significant to understand the properties of MoS₂ based nanomaterials and the development of two-dimensional nanomaterials with enzyme mimicking activities.

Iodine-doped carbon dots with inherent peroxidase catalytic activity for photocatalytic antibacterial and wound disinfection

A new type of nitrogen-iodine co-doped carbon dot (N/I-CD) was synthesized by a one-step hydrothermal method with a fluorescence quantum yield of 37%. The prepared N/I-CDs exhibit peroxidase-like activity, can catalyze bio-safety levels of H2O2 to generate hydroxyl radicals (•OH) under visible light and enhance the level of reactive oxygen species (ROS) in bacteria cells. All in vitro experiments showed that the designed system has strong photocatalytic antibacterial activity against both E. coli and S. aureus bacteria. The light-induced antibacterial function of N/I-CDs was evaluated under the conditions of changing other experimental parameters. When the visible light irradiation time was extended to 60 min, the antibacterial efficiency of N/I-CDs (0.21 mg·mL-1) against S. aureus and E. coli reached 100% in the presence of exogenous H2O2 (0.07 mM). More importantly, wound disinfection in vivo demonstrates the high antibacterial efficiency, low toxicity and application potential of good biocompatibility due to the nanozyme activity of N/I-CDs.

The In Vivo, In Vitro and In Ovo Evaluation of Quantum Dots in Wound Healing: A Review

Wound is defined as primarily damaged or disruption of skin contributed to the loss of its microstructure stability and which undergoes complex wound healing process. However, there are tons of factors that could affect the wound healing process such as infection and slow angiogenesis. Involvement of nanotechnologies therapies in wound care research aims to facilitates this healing process. Quantum dots (QDs) are an advanced nanomaterial technology found to be useful in clinical and biomedical applications. This review has been carried out to provide a summary of the application of QDs in acute or chronic wound healing. A thorough searching was done via Web of Science and SCOPUS database to obtain relevant articles including the in vivo, in vitro and in ovo studies. The results demonstrated a similar effect of different types of QDs, or an improvement of QDs in wound healing, antibacterial and angiogenesis properties. This review demonstrated the effectiveness of QDs for the wound healing process mainly by their antibacterial activity. Uniquely, the antibacterial effect unraveled an increasing trend over time influenced by the various concentration of QDs. In conclusion, the application of QDs support the wound healing phases and proven to be effective in vivo, in vitro and in ovo. However, the future QDs work should focus on the molecular level for the details of cellular interactions and pathways.

Near-Infrared Regulated Nanozymatic/Photothermal/Photodynamic Triple-Therapy for Combating Multidrug-Resistant Bacterial Infections via Oxygen-Vacancy Molybdenum Trioxide Nanodots

Bacterial infections have become a major danger to public health because of the appearance of the antibiotic resistance. The synergistic combination of multiple therapies should be more effective compared with the respective one alone, but has been rarely demonstrated in combating bacterial infections till now. Herein, oxygen-vacancy molybdenum trioxide nanodots (MoO_3-x NDs) are proposed as an efficient and safe bacteriostatic. The MoO_3-x NDs alone possess triple-therapy synergistic efficiency based on the single near-infrared irradiation (808 nm) regulated combination of photodynamic, photothermal, and peroxidase-like enzymatic activities. Therein, photodynamic and photothermal therapies can be both achieved under the excitation of a single wavelength light source (808 nm). Both the photodynamic and nanozyme activity can result in the generation of reactive oxygen species (ROS) to reach the broad-spectrum sterilization. Interestingly, the photothermal effect can regulate the MoO_3-x NDs to their optimum enzymatic temperature (50 °C) to give sufficient ROS generation in low concentration of H₂ O₂ (100 µm). The MoO_3-x NDs show excellent antibacterial efficiency against drug-resistance extended spectrum β-lactamases producing Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). Animal experiments further indicate that the MoO_3-x NDs can effectively treat wounds infected with MRSA in living systems.

Near-Infrared-Controlled Nanoplatform Exploiting Photothermal Promotion of Peroxidase-like and OXD-like Activities for Potent Antibacterial and Anti-biofilm Therapies

Nanozymes that mimic peroxidase (POD) activity can convert H₂O₂ into bactericidal free radicals, which is referred to as chemodynamic therapy (CDT). High glutathione (GSH) levels in the infectious tissue severely limit the performance of CDT. Herein, we report a near-infrared-controlled antibacterial nanoplatform that is based on encapsulating tungsten sulfide quantum dots (WS₂QDs) and the antibiotic vancomycin in a thermal-sensitive liposome. The system exploits the photothermal sensitivity of the WS₂QDs to achieve selective liposome rupture for the targeted drug delivery. We determined that WS₂QDs show a strong POD-like activity under physiological conditions and the oxidase-like activity, which can oxidate GSH to further improve the CDT efficacy. Moreover, we found that increased temperature promotes multiple enzyme-mimicking activities of WS₂QDs. This platform exerts antibacterial effects against Gram-positive Mu50 (a vancomycin-intermediate Staphylococcus aureus reference strain) and Gram-negative Escherichia coli and disrupts biofilms for improved penetration of therapeutic agents inside biofilms. In vivo studies with mice bearing Mu50-caused skin abscess revealed that this platform confers potent antibacterial activity without obvious toxicity. Accordingly, our work illustrates that the photothermal and nanozyme properties of WS₂QDs can be deployed alongside a conventional therapeutic to achieve synergistic chemodynamic/photothermal/pharmaco therapy for powerful antibacterial effects.

Hydrothermally Assisted Fabrication of TiO2-Fe3O4 Composite Materials and Their Antibacterial Activity

The TiO2-Fe3O4 composite materials were fabricated via the hydrothermal-assisted technique. It was determined how the molar ratio of TiO2 to Fe3O4 influences the crystalline structure and morphology of the synthesized composite materials. The effect of the molar ratio of components on the antibacterial activity was also analyzed. On the basis of XRD patterns for the obtained titanium(IV) oxide-iron(II, III) oxide composites, the two separate crystalline forms-anatase and magnetite -were observed. Transmission electron microscopy revealed particles of cubic and tetragonal shape for TiO2 and spherical for Fe3O4. The results of low-temperature nitrogen sorption analysis indicated that an increase in the iron(II, III) oxide content leads to a decrease in the BET surface area. Moreover, the superparamagnetic properties of titanium(IV) oxide-iron(II, III) oxide composites should be noted. An important aim of the work was to determine the antibacterial activity of selected TiO2-Fe3O4 materials. For this purpose, two representative strains of bacteria, the Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, were used. The titanium(IV) oxide-iron(II, III) oxide composites demonstrated a large zone of growth inhibition for both Gram-positive and Gram-negative bacteria. Moreover, it was found that the analyzed materials can be reused as antibacterial agents in three consecutive cycles with good results.

Natural Polyphenol-Vanadium Oxide Nanozymes for Synergistic Chemodynamic/Photothermal Therapy

The selection of suitable nanozymes with easy synthesis, tumor specificity, multifunction, and high therapeutics is meaningful for tumor therapy. Herein, a facile one-step assembly approach was employed to successfully prepare a novel kind of natural polyphenol tannic acid (TA) hybrid with mixed valence vanadium oxide nanosheets (TA@VO_x NSs). In this system, VO_x is assembled with TA through metal-phenolic coordination interaction to both introduce superior peroxidase-like activity and high near infrared (NIR) absorption owing to partial reduction of vanadium from V⁵⁺ to V⁴⁺ . The presence of mixed valence vanadium oxide in TA@VO_x NSs is proved to be the key for the catalytic reaction of hydrogen peroxide (H₂ O₂ ) to ^. OH, and the corresponding catalytic mechanism of H₂ O₂ by TA@VO_x NSs is proposed. Benefitting from such peroxidase-like activity of TA@VO_x NSs, the overproduced H₂ O₂ of the tumor microenvironment allows the realization of tumor-specific chemodynamic therapy (CDT). As a valid supplement to CDT, the NIR absorption enables TA@VO_x NSs to have NIR light-mediated conversion ability for photothermal therapy (PTT) of cancers. Furthermore, in vitro and in vivo experiments confirmed that TA@VO_x NSs can effectively inhibit the growth of tumors by synergistic CDT/PTT. These results offer a promising way to develop novel vanadium oxide-based nanozymes for enhanced synergistic tumor-specific treatment.

Nanozymes used for antimicrobials and their applications

Bacterial infection-related diseases have been growing year-by-year rapidly and raising health problems globally. The exploitation of novel, high efficiency, and bacteria-binding antibacterial agents are extremely need. As far as now, the most extensive treatment is restricted to antibiotics, which may be overused and misused, leading to increased multidrug resistance. Antibiotics abuse, as well as antibiotic-resistance of bacteria, is a global challenge in the current situation. It is highly recommended and necessary to develop novel bactericide to kill the bacteria effectively without causing further resistance development and biosafety issues. Nanozymes, inorganic nanostructures with intrinsic enzymatic activities, have attracted more and more interest from the researchers owing to their exceptional advantages. Compared to natural enzymes, nanozymes can destroy many Gram-positive, Gram-negative bacteria, which builds an important bridge between biology and nanotechnology. As the potent nanoantibiotics, nanozymes have exciting broad-spectrum antimicrobial properties and negligible biotoxicities. And we summarized and highlighted the recent advances on nanozymes including its antibacterial mechanism and applications. Finally, challenges and limitations for the further improvement of the antibacterial activity are covered to provide future directions for the use of engineered nanozymes with enhanced antibacterial function.

Ti3C2Tx MXene-derived TiO2/C-QDs as oxidase mimics for the efficient diagnosis of glutathione in human serum

A Ti₃C₂T_x MXene-derived TiO₂/C-QD oxidase mimic was developed and used for the efficient diagnosis of glutathione in human serum.