Intrinsic Oxidase-like Nanoenzyme Co4S3/Co(OH)2 Hybrid Nanotubes with Broad-Spectrum Antibacterial Activity

Durable Rapid Self-Disinfection, Reusable Protective Clothing Based on the Ag-Pd@MoS2 Nanozyme with Enhanced Triple-Mode Synergistic Antibacterial Effect

Personal protective clothing plays an important role in isolating microorganisms and harmful ultrafine dust, but it cannot quickly inactivate bacteria intercepted on the surface, making it a potential source of infection. However, spontaneous and durable rapid sterilization is a major challenge for commercial protective clothing. Herein, we exquisitely engineered a visible light-enhanced Ag-Pd@MoS₂ nanozyme-based fabric, named PVDF/Ag-Pd@MoS₂/PAN fabric (PAPMP fabric), with prominent triple-mode synergistic antibacterial effect through the replacement reaction, electrospinning technique, and vacuum filtration method. The modification of Ag-Pd greatly strengthened the absorption of MoS₂ nanosheets to the visible light spectrum (390-780 nm) and its corresponding catalytic performance. Meanwhile, the combination of MoS₂ nanosheets significantly enhanced the oxidase-like characteristics of Ag-Pd under sunlight irradiation, increasing the yield of surface-bound ¹O₂ ∼4.54 times in 5 min. In addition, the obtained Ag-Pd@MoS₂ nanozyme showed an excellent photo-to-thermal conversion property (36.12%), which enabled the sharp increase in the surface temperature of the PAPMP fabric to 62.8 °C in 1 min under a solar simulator (1 W/cm²). Correspondingly, the obtained PAPMP fabric exhibited excellent intrinsic antibacterial effect and greatly shortened the sterilization time from 4 h to only 5 min under sunlight stimulation. The rapid antibacterial effect of the fabric was attributable to the enhanced production rate of surface-bound reactive oxygen species and the increased temperature by solar irradiation. Notably, the fabric still maintained the efficient germicidal effect even after 30 washing cycles. In addition to high reusability, the fabric also had outstanding biological compatibility and water resistance. Our work provides a novel strategy to improve the inherent timely sterilization and heat preservation efficiency of protective clothing.

Exploring the Antibacterial and Biosensing Applications of Peroxidase-Mimetic Ni0.1Cu0.9S Nanoflower

Nanozymes, as artificial enzymes with the biological action of natural enzymes, have enormous potential in the fields of disease diagnosis, bacteriostasis, biosensing, etc. In this work, the Ni_0.1Cu_0.9S nanoflower was successfully synthesized through a one-step hydrothermal method. A combined strategy of Ni doping and morphology design was employed to adjust its electronic structure and active sites, endowing the Ni_0.1Cu_0.9S nanoflower with excellent peroxidase-like activity. Therefore, it can catalyze the decomposition of H₂O₂ to generate •OH with higher antibacterial activity, establishing a broad-spectrum antibacterial system based on the Ni_0.1Cu_0.9S nanoflower against E. coli and S. aureus, which avoids the harm of a high concentration of H₂O₂. Additionally, the colorless substrate TMB can be catalytically oxidized into blue ox-TMB via •OH. As a result, a colorimetric technique with rapid and accurate detection of ascorbic acid (AA) by the unaided eye was designed, in view of the specific inhibition effect towards the oxidation of TMB. This detection platform has a wide linear range (10~800 μM) with a low limit of detection (0.84 μM) and exhibits a satisfactory selectivity toward the detection of AA. This study sheds new light on the application of copper-containing nanozymes in the fields of biomedicine and bioassay.

Recent Trends in Composite Nanozymes and Their Pro-Oxidative Role in Therapeutics

Nanozymes are inorganic nanostructures whose enzyme mimic activities are increasingly explored in disease treatment, taking inspiration from natural enzymes. The catalytic ability of nanozymes to generate reactive oxygen species can be used for designing effective antimicrobials and antitumor therapeutics. In this context, composite nanozymes are advantageous, particularly because they integrate the properties of various nanomaterials to offer a single multifunctional platform combining photodynamic therapy (PDT), photothermal therapy (PTT), and chemodynamic therapy (CDT). Hence, recent years have witnessed great progress in engineering composite nanozymes for enhanced pro-oxidative activity that can be utilized in therapeutics. Therefore, the present review traverses over the newer strategies to design composite nanozymes as pro-oxidative therapeutics. It provides recent trends in the use of composite nanozymes as antibacterial, antibiofilm, and antitumor agents. This review also analyzes various challenges yet to be overcome by pro-oxidative composite nanozymes before being used in the field.

How to Make Personal Protective Equipment Spontaneously and Continuously Antimicrobial (Incorporating Oxidase-like Catalysts)

The inability of commercial personal protective equipment (PPE) to inactivate microbes in the droplets/aerosols they intercept makes used PPE a potential source of cross-contamination. To make PPE spontaneously and continuously antimicrobial, we incorporate PPE with oxidase-like catalysts, which efficiently convert O₂ into reactive oxygen species (ROS) without requiring any externally applied stimulus. Using a single-atom catalyst (SAC) nanoparticle containing atomically dispersed copper atoms as the reactive centers (Cu-SAC) and a silver-palladium bimetallic alloy nanoparticle (AgPd_0.38) as models for oxidase-like catalysts, we show that the incorporation of oxidase-like catalysts enables PPE to inactivate bacteria in the droplets/aerosols they intercept without requiring any externally applied stimulus. Notably, this approach works both for PPE that are fibrous and woven such as a commercial KN95 facial respirator and for those made of solid plastics such as an apron. This work suggests a feasible and global approach for preventing PPE from spreading infectious diseases.

Hydrogels for Antitumor and Antibacterial Therapy

As a highly absorbent and hydrophobic material with a three-dimensional network structure, hydrogels are widely used in biomedical fields for their excellent biocompatibility, low immunogenicity, adjustable physicochemical properties, ability to encapsulate a variety of drugs, controllability, and degradability. Hydrogels can be used not only for wound dressings and tissue repair, but also as drug carriers for the treatment of tumors. As multifunctional hydrogels are the focus for many researchers, this review focuses on hydrogels for antitumor therapy, hydrogels for antibacterial therapy, and hydrogels for co-use in tumor therapy and bacterial infection. We highlighted the advantages and representative applications of hydrogels in these fields and also outlined the shortages and future orientations of this useful tool, which might give inspirations for future studies.

3D V2O5-MoS2/rGO nanocomposites with enhanced peroxidase mimicking activity for sensitive colorimetric determination of H2O2 and glucose

In this work, we reported a novel nanozyme (3D V₂O₅-MoS₂/rGO) by decorating MoS₂ nano-flowers and V₂O₅ nanoparticles on reduced graphene oxide (rGO). The 3D V₂O₅-MoS₂/rGO nanocomposites exhibited intrinsic peroxidase mimicking activity and catalyzed the oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) to produce a blue colored product in the presence of H₂O₂. Compared with horseradish peroxidase (HRP), 3D V₂O₅-MoS₂/rGO nanocomposites displayed high catalytic velocity (V_max) and affinity (K_m) for substrates (H₂O₂ and TMB). The study of the catalytic mechanism showed that the reduction of V⁵⁺ and the oxidation of S^2- in the 3D V₂O₅-MoS₂/rGO nanocomposites accelerate electron transfer between H₂O₂ and TMB, which enhanced the peroxidase mimicking activity of 3D V₂O₅-MoS₂/rGO nanocomposites. The as-synthetized 3D V₂O₅-MoS₂/rGO could be used for the colorimetric detection of H₂O₂ in the range of 20.00-800.00 μM with the LOD of 12.40 μM (3σ/S). Moreover, the 3D V₂O₅-MoS₂/rGO could also be used for the detection of glucose in the range of 4.00-300.00 μM with the LOD of 3.99 μM (3σ/S). In addition, the as-synthetized novel peroxidase mimics has good applicability for sensitive colorimetric determination of glucose in human blood samples and artificial urine samples, and has broad application prospects as a multi-functional sensing platform in clinical diagnosis.

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.

Nanozymes-recent development and biomedical applications

Nanozyme is a series of nanomaterials with enzyme-mimetic activities that can proceed with the catalytic reactions of natural enzymes. In the field of biomedicine, nanozymes are capturing tremendous attention due to their high stability and low cost. Enzyme-mimetic activities of nanozymes can be regulated by multiple factors, such as the chemical state of metal ion, pH, hydrogen peroxide (H₂O₂), and glutathione (GSH) level, presenting great promise for biomedical applications. Over the past decade, multi-functional nanozymes have been developed for various biomedical applications. To promote the understandings of nanozymes and the development of novel and multifunctional nanozymes, we herein provide a comprehensive review of the nanozymes and their applications in the biomedical field. Nanozymes with versatile enzyme-like properties are briefly overviewed, and their mechanism and application are discussed to provide understandings for future research. Finally, underlying challenges and prospects of nanozymes in the biomedical frontier are discussed in this review.

Development of enzyme-free single-step immunoassays for glycocholic acid based on palladium nanoparticle-mediated signal generation

Palladium nanoparticles (PdNPs) are composed mainly of inert noble metals, and their outstanding properties have attracted wide attention. PdNPs are not only capable of mimicking the oxidase-like characteristics of natural bio-enzymes, but they also present a clear black band in the test zone. In this work, the synthesized PdNPs promoted a transformation of colorless tetramethylbenzidine (TMB) to a blue oxidation product of TMB, providing a K_m value of 0.09 mM for TMB, and revealing the good catalytic performance of the synthesized PdNPs. For both signal generation and amplification, PdNPs effectively replaced natural bio-enzymes as a new labeling tag. Thus, the PdNP-based enzyme-free single-step immunoassays were successfully developed for efficient and sensitive detection of glycocholic acid (GCA). Under optimal conditions, a noticeable linear relationship was identified by the enzyme-linked immunosorbent assay (ELISA) over a range of 8-2390 ng/mL, while the visual limit of detection (vLOD) in the constructed lateral flow immunoassay (LFA) was 10 ng/mL for GCA. The recovery rate in spiked urine samples obtained by the ELISA ranged from 84.2 to 117.9%, which was consistent with the results in LFA. The present work demonstrates the potential of PdNPs as labeling matrices in enzyme-free single-step immunoassays.

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.