Synthesis of γ-Cyclodextrin-Reduced Fe(III) Nanoparticles with Peroxidase-like Catalytic Activity for Bacteriostasis of Food

Cyclodextrin reduced Fe(III) nanozyme-based colorimetric and photothermal dual-mode assay for early monitoring meat freshness by sensitive detection of hypoxanthine

A simple and sensitive method for monitoring the freshness of meat products is crucial for safeguarding food hygiene and human health. Here, we synthesized an environmentally friendly β-CD@Fe nanozyme through a one-pot solvothermal method, enabling colorimetric and photothermal dual-mode detection of hypoxanthine (Hx). In the xanthine oxidase (XOD)/nanozyme enzymatic cascade system, Hx ultimately led to the oxidation of colorless TMB to blue oxTMB, accompanied by enhanced absorbance at 652 nm and an increased temperature under 808 nm laser irradiation. The proposed dual-mode assay for Hx exhibited a good linear relationship in the range of 1-40 μM, achieving low detection limits of 0.29 μM (colorimetric) and 1.0 μM (photothermal), respectively. The β-CD@Fe nanozyme, characterized by its environmental friendliness, mild synthesis conditions, and high peroxidase-like activity, was successfully applied for the sensitive analysis of Hx in actual meat samples. This advancement offers promising potential for applications in food safety supervision.

Dual-functional Zn@melanin nanoparticles for enhanced antibacterial activity and prolonged fruit preservation

Mitigating food spoilage from microbial infections remains a critical challenge in food preservation. Although Zn2+ ions are used as chemical bactericides, their use alone often requires high doses. A novel nanomaterial, Zn@MNPs, combining photothermal properties with the controlled release of Zn2+, was synthesized through a coordination of Zn2+ with melanin nanoparticles (MNPs) derived from cuttlefish ink. Zn@MNPs were capable of attaching onto the bacterial surfaces, enabling high-efficiency release of Zn2+ under mildly acidic conditions typically associated with bacterial infections. This leads to sustained antibacterial activity, causing bacterial membrane rupture and leakage of intracellular components. Incorporating Zn@MNPs into polyvinyl alcohol (PVA)-based films improved their ability to block UV light and reduce oxygen and water vapor permeability. These films effectively reduced dehydration, preserved nutritional content, and extended fruit shelf life. This study highlights the potential of Zn@MNPs-based PVA films as biodegradable, bioactive packaging materials for enhancing food preservation and safety.

Multifunctional CuTax nanozyme-based chitosan edible coatings for fruit preservation

The preservation of fresh fruits is critically challenged by oxidative degradation and microbial contamination, which lead to quality deterioration and reduced shelf life. In this study, we took advantage of the multiple benefits of Taxfolin (Tax) and copper to develop CuTax nanozymes, and which were showed to have excellent free radical scavenging ability, as evidenced by 90.3 % ± 0.2 % DPPH and 85.61 % ± 0.08 % ABTS free radical scavenging rates. Additionally, the CuTax exhibited peroxidase-like (POD-like) activity and effective glutathione (GSH) depletion. Moreover, the CuTax were found to effectively suppress the colony formation of E. coli and S. aureus, reduce bacterial viability, and disrupt bacterial structures. Ultimately, a CuTax/CS composite coating/films for food preservation was successfully developed using chitosan (CS) as a carrier and the protective efficacy against food spoilage was evaluated using bananas and apples as representative fruits. These findings suggest that CuTax/CS composite coatings offer a multifunctional approach to active food packaging that effectively extend the shelf life and preserve the quality of fresh fruits.

Lignin-based nanoenzyme doped hydrogel for NO-enhanced chemodynamic therapy of bacterial infections

The infections triggered by bacteria often cause wound deterioration, and the development of safe and effective antimicrobial treatment is always highly desired. In this paper, naturally derived lignin was aminated to generate surface group functionalized lignin nanoparticles (NPs), efficiently loading Ag NPs and adsorbing L-arginine, to construct lignin-based nanoenzyme (SALL), which achieves synergistic antimicrobial treatment by chemodynamic therapy and NO gas therapy, while the dose of silver was decreased. The SALL is dispersed in eco-friendly hydrogel constructed using keratin and chitosan through realigned disulfide bond and diverse intermolecular interactions, the prepared SALL@K/C hydrogel has ideal rheological property, and strong adhesion capacity facilitating active bacteria capture, ensuring that the bacteria were immobilized within the effective range of reactive oxygen species and NO. The inhibition rates of S. aureus and E. coli were 98.5 % and 97.8 %, respectively. Meanwhile, the SALL@K/C hydrogel could achieve the delivery of hydrophobic drug curcumin for inhibiting inflammation. The study highlights a well-designed nanoenzyme-loaded hydrogel with excellent antibacterial, hemostatic, and antiinflammatory properties, offering new ideas for nanoenzyme design and antimicrobial hydrogel development.

One-pot synthesis smartphone-assisted test strip based on food-grade Fe-β-Cyclodextrin nanozymes for rapid colorimetric analysis of ascorbic acid in foods and supplements

Accurate on-site analysis of food quality is of great significance for ensuring public health. Among them, ascorbic acid (AA) is an essential micronutrient widely used as an additive in juices and drugs to improve food quality and human health. In this work, we developed food-grade Fe-β-Cyclodextrin(Fe-β-CD) nanozymes based on inexpensive and readily available β-cyclodextrin and iron ions for the detection of AA. Fe-β-CD confirmed excellent peroxidase-like activity and oxidized colorless 3,3',5,5'-tetramethylbenzidine (TMB) to oxide TMB. AA could inhibit the oxidation reaction and cause blue to fade. Based on the above principles, Fe-β-CD nanozymes exhibited a low detection limit (3.4 μM) for detecting AA, with a wide linear range (10-300 μM). This method had been successfully used for the detection of AA in fruits and vitamin C tablets, and the results were consistent with the specified values. More importantly, an integrated smartphone-assisted Fe-β-CD@test strip colorimetric application platform constructed by one-pot method, the test strip also had better stability, and could be combined with smartphones to achieve convenient AA detection without using any instruments, which showed enormous potential for rapid and low-cost colorimetric detection of AA.

Photocatalytic rice bran protein/carboxymethyl cellulose/ZrO2 fiber produced by microfluidics: Formation mechanism, bacteriostasis and strawberry preservation

Developing cost-effective and environmentally sustainable active packaging materials remains an important challenge. We have developed rice bran protein (RBP)-based fibers incorporating carboxymethyl cellulose (CMC) and ZrO2 nanoparticles (ZrO2 NPs, 0 %-7 %, m/m) using microfluidic spinning. The integration of RBP, CMC, and ZrO2 NPs formed a robust hydrogen bond network that enhanced the fibers' thermal stability and crystallinity, reduced surface hydrophobicity, and aligned the molecular orientation. Under the catalysis of visible light (300 W, 12 h), ZrO2 NPs in the fiber produced reactive oxygen species, which inhibited the oxidative stress resistance system of Bacillus subtilis and destroyed its biofilm and DNA, thus showing excellent antibacterial effect. Additionally, during storage, this fiber also showed the ability to scavenge ethylene, thereby reducing the rate of loss of luminance, hardness and weight of strawberries. This study offers a new idea for RBP fiber in food preservation, antibacterial, and value-added utilization of rice bran by-products.

Synergistic antimicrobial activities of peroxymonosulfate with Ce-FcDC as an activator

Ce-MOFs with ferrocenedicarboxylic acid ligands (Ce-FcDC) as a bifunctional nanozyme exhibited high peroxidase (POD)-mimicking activity and superoxide dismutase (SOD)-mimicking activity. H2O2 was produced from catalytic hydrolysis of peroxymonosulfate (PMS) using Ce-FcDC as a catalyst. The growth of E. coli and S. aureus were synergistically and more effectively suppressed by PMS in the presence of Ce-FcDC, in comparison with the sole use of PMS or Ce-FcDc. Under the catalysis of Ce-FcDC as the POD-mimicking nanozyme, PMS could be activated by Ce-FcDC to produce SO4•- and •OH and H2O2 from the hydrolysis of PMS was further derivatized to O2•- and •OH. Ce-FcDC as the SOD-mimicking nanozyme causes O2•- to form H2O2. The generation of O2•- and •OH were confirmed using p-benzoquinone and isopropanol alcohol as the scavengers. The resulted SO4•-, O2•-, and •OH from combination of PMS with Ce-FcDC as an activator may have key roles for suppressing the growth of E. coli and S. aureus. This strategy could be an effective approach for suppressing the growth and preventing infections or pollutions of some other microbial cells as well.

Construction of multifunctional hydrogel containing pH-responsive gold nanozyme for bacteria-infected wound healing

Nanozymes have become promising alternative antibacterial agents for bacteria-infected wounds. In this study, fucoidan-confined gold nanoparticles (Fuc@AuNPs) are developed by in situ reduction, and stabilized by sulfate groups of fucoidan. Fuc@AuNPs exhibit pH-responsive catalytic activity that can mimic oxidase (OXD) under acidic bacterial infection conditions and mimic superoxide dismutase (SOD) under normal physiological conditions. The OXD-like catalytic activity of Fuc@AuNPs generates active singlet oxygen (1O2), exhibiting effective antibacterial properties against both Gram-negative E. coli and Gram-positive S. aureus. Fuc@AuNPs and aldehyde grafted saponin incorporate with chitosan to form a hybrid hydrogel. This hydrogel exhibits superior mechanical, adhesive, and self-healing properties due to electrostatic complex coacervation networks and dynamic covalent Schiff base reactions. Animal experiments show that the hydrogel aids S. aureus-infected skin wound healing by reducing bacterial infection and promoting granulation tissue formation without causing excessive ROS-induced inflammation. This study presents the design of multifunctional nanozymes and bioactive hydrogels as a promising wound healing dressing for biomedical applications.

Chiral nanoenzymes: synthesis and applications

Chiral nanoenzymes are a new type of material that possesses both chiral nanostructures and enzymatic catalytic activity. These materials exhibit selectivity in their catalytic activity towards organisms due to the introduction of chiral features in nanomaterials and have inherent chiral discrimination in organisms. As synthetic enzymes, chiral nanoenzymes offer significant advantages over natural enzymes. Due to their unique chiral structure and distinctive physicochemical properties, chiral nanoenzymes play an important role in various fields, including biology, medicine, and environmental protection. Their strong stereospecificity and biocompatibility make them useful in disease therapy, biosensing, and chiral catalysis, setting them apart from conventional and natural enzymes. In recent years, the design of synthetic methods and biological applications of chiral nanoenzymes has received significant attention and extensive research among scientists. This paper provides a systematic review of the research progress in the discovery, development, and application of chiral nanoenzymes in the last decade. Additionally, it presents various applications of chiral nanoenzymes, such as disease therapy, biosensing, and chiral catalysis. Finally, the challenges and future prospects of chiral nanoenzymes are discussed.

Construction of carbon-doped iron-based nanozyme for efficient adsorption and degradation to synergistic removal of aflatoxin B1

The multifunctional composites Fe3O4/GO/NH2-MIL-53(Fe) with excellent adsorption-degradation performance was prepared for the removal of Aflatoxin B1 (AFB1). The adsorption function of Fe3O4/GO/NH2-MIL-53(Fe) was based on the large specific surface area and abundant adsorption sites. The degradation function of Fe3O4/GO/NH2-MIL-53(Fe) was based on the activation of H2O2 by the catalytic active center formed by the coordination of metal ions and oxygen-containing groups in the system, resulting in hydroxyl radicals (·OH), superoxide anion radicals (O2-) and singlet oxygen (1O2). The adsorption of nanozyme accelerated the degradation reaction process, and the adsorption site was further exposed as the degradation process progressed. The synergistic effect realized the efficient removal of AFB1. Construction of Fe3O4/GO/NH2-MIL-53(Fe) as the carbon-doped iron-based nanozyme provided novel approaches of the removal for risks control of AFB1. Accompanied by the AFB1 adsorption, the advanced oxidation of nanozyme to the AFB1 degradation provided a promising way for the synergistic removal of AFB1.

Nanozybiotics: Advancing Antimicrobial Strategies Through Biomimetic Mechanisms

Infectious diseases caused by bacterial, viral, and fungal pathogens present significant global health challenges. The rapid emergence of antimicrobial resistance exacerbates this issue, leading to a scenario where effective antibiotics are increasingly scarce. Traditional antibiotic development strategies are proving inadequate against the swift evolution of microbial resistance. Therefore, there is an urgent need to develop novel antimicrobial strategies with mechanisms distinct from those of existing antibiotics. Nanozybiotics, which are nanozyme-based antimicrobials, mimic the catalytic action of lysosomal enzymes in innate immune cells to kill infectious pathogens. This review reinforces the concept of nanozymes and provides a comprehensive summary of recent research advancements on potential antimicrobial candidates. Initially, nanozybiotics are categorized based on their activities, mimicking either oxidoreductase-like or hydrolase-like functions, thereby highlighting their superior mechanisms in combating antimicrobial resistance. The review then discusses the progress of nanozybiotics in treating bacterial, viral, and fungal infections, confirming their potential as novel antimicrobial candidates. The translational potential of nanozybiotic-based products, including hydrogels, nanorobots, sprays, bandages, masks, and protective clothing, is also considered. Finally, the current challenges and future prospects of nanozybiotic-related products are explored, emphasizing the design and antimicrobial capabilities of nanozybiotics for future applications.

pH‑responsive nanozyme cascade catalysis: A strategy of BiVO4 application for modulation of pathological wound microenvironment

Persistent inflammation and bacterial infection commonly occur during the wound healing process, necessitating urgent development of effective strategies for treating drug-resistant bacterial infections. In this study, bismuth vanadate (BiVO4) was successfully synthesized as an antibacterial agent that promotes wound healing. Through In vitro antibacterial experiments, it was observed that the prepared BiVO4 exhibited excellent performance in catalyzing H2O2 to produce hydroxyl radicals (OH) at a lower concentration (0.2 mg mL-1), resulting in significant antibacterial effects against Gram-negative Extended-Spectrum β-Lactamases-Producing Escherichia coli (ESBL-E. coli) strains. Furthermore, biosafety tests, cell scratch experiments, and ESBL-E. coli infected wound rat model experiments demonstrated high biocompatibility of BiVO4 with a cell survival rate exceeding 85 %. Additionally, BiVO4 promoted the production of vascular endothelial growth factors and fibroblasts migration while contributing to collagen production, effectively facilitating immune reconstruction at the wound site. By integrating peroxidase (POD)-like under acidic conditions (pH 4) and catalase (CAT)-like catalytic activities at under neutral conditions (pH 7), BiVO4 exhibited the ability to activate free radical sterilization and accelerate wound healing by activating O2. Therefore, our findings provide evidence for a dual enzyme regulatory mechanism involving antibacterial properties and promotion of wound tissue reconstruction for potential application in both antibacterial treatment and wound healing.

Cascade Reactions Catalyzed by Gold Hybrid Nanoparticles Generate CO Gas Against Periodontitis in Diabetes

The treatment of diabetic periodontitis poses a significant challenge due to the presence of local inflammation characterized by excessive glucose concentration, bacterial infection, and high oxidative stress. Herein, mesoporous silica nanoparticles (MSN) are embellished with gold nanoparticles (Au NPs) and loaded with manganese carbonyl to prepare a carbon monoxide (CO) enhanced multienzyme cooperative hybrid nanoplatform (MSN-Au@CO). The Glucose-like oxidase activity of Au NPs catalyzes the oxidation of glucose to hydrogen peroxide (H2O2) and gluconic acid，and then converts H2O2 to hydroxyl radicals (•OH) by peroxidase-like activity to destroy bacteria. Moreover, CO production in response to H2O2, together with Au NPs exhibited a synergistic anti-inflammatory effect in macrophages challenged by lipopolysaccharides. The underlying mechanism can be the induction of nuclear factor erythroid 2-related factor 2 to reduce reactive oxygen species, and inhibition of nuclear factor kappa-B signaling to diminish inflammatory response. Importantly, the antibacterial and anti-inflammation effects of MSN-Au@CO are validated in diabetic rats with ligature-induced periodontitis by showing decreased periodontal bone loss with good biocompatibility. To summarize, MSN-Au@CO is fabricate to utilize glucose-activated cascade reaction to eliminate bacteria, and synergize with gas therapy to regulate the immune microenvironment, offering a potential direction for the treatment of diabetic periodontitis.

Organic-Inorganic Heterointerface-Expediting Electron Transfer Realizes Efficient Plasmonic Catalytic Sterilization via a Carbon-Dot Nanozyme

Plasmonic nanozymes bring enticing prospects for catalytic sterilization by leveraging plasmon-engendered hot electrons. However, the interface between plasmons and nanozymes as the mandatory path of hot electrons receives little attention, and the mechanisms of plasmonic nanozymes still remain to be elucidated. Herein, a plasmonic carbon-dot nanozyme (FeCG) is developed by electrostatically assembling catalytic iron-doped carbon dots (Fe-CDs) with plasmonic gold nanorods. The energy harvesting and hot-electron migration are remarkably expedited by a spontaneous organic-inorganic heterointerface holding a Fermi level-induced interfacial electric field. The accumulated hot electrons are then fully utilized by conductive Fe-CDs to boost enzymatic catalysis toward overproduced reactive oxygen species. By synergizing with localized heating from hot-electron decay, FeCG achieves rapid and potent disinfection with an antibacterial efficiency of 99.6% on Escherichia coli within 5 min and is also effective (94.2%) against Staphylococcus aureus. Our work presents crucial insights into the organic-inorganic heterointerface in advanced plasmonic biocidal nanozymes.

Bactericidal and biofilm eradication efficacy of a fluorinated benzimidazole derivative, TFBZ, against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a major inducement of nosocomial infections and its biofilm formation render the high tolerance to conventional antibiotics, which highlights the requirement to develop new antimicrobial agents urgently. In this study, we identified a fluorinated benzimidazole derivative, TFBZ, with potent antibacterial efficacy toward planktonic MRSA (MIC = 4 μg/mL, MBC = 8 μg/mL) and its persistent biofilms (≥99%, MBEC = 8 μg/mL). TFBZ manifested significant irreversible time-dependent killing against MRSA as characterized by diminished cell viability, bacterial morphological change and protein leakage. Furthermore, the results from CBD devices, crystal violet assay in conjunction with live/dead staining and scanning electron microscopy confirmed that TFBZ was capable of eradicating preformed MRSA biofilms with high efficiency. Simultaneously, TFBZ reduced the bacterial invasiveness and exerted negligible hemolysis and cytotoxicity toward mammalian cells, which ensuring the robust therapeutic effect on mouse skin abscess model. The transcriptome profiling and quantitative RT-PCR revealed that a set of encoding genes associated with cell adhesion, biofilm formation, translation process, cell wall biosynthesis was consistently downregulated in MRSA biofilms upon exposure to TFBZ. In conclusion, TFBZ holds promise as a valuable candidate for therapeutic applications against MRSA chronic infections.

Advances in the Application of Transition-Metal Composite Nanozymes in the Field of Biomedicine

Due to the limitation that natural peroxidase enzymes can only function in relatively mild environments, nanozymes have expanded the application of enzymology in the biological field by dint of their ability to maintain catalytic oxidative activity in relatively harsh environments. At the same time, the development of new and highly efficient composite nanozymes has been a challenge due to the limitations of monometallic particles in applications and the inherently poor enzyme-mimetic activity of composite nanozymes. The inherent enzyme-mimicking activity is due to Au, Ag, and Pt, along with other transition metals. Moreover, the nanomaterials exhibit excellent enzyme-mimicking activity when composited with other materials. Therefore, this paper focuses on composite nanozymes with simulated peroxidase activity that have been prepared using noble metals such as Au, Ag, and Pt and other transition metal nanoparticles in recent years. Their simulated enzymatic activity is utilized for biomedical applications such as glucose detection, cancer cell detection and tumor treatment, and antibacterial applications.