Copper metal organic framework as natural oxidase mimic for effective killing of Gram-negative and Gram-positive bacteria

Copper-based fluorescent nanozyme used to construct a ratiometric sensor for visual detection of thiophanate methyl

Although nanozyme has shown great potential in designing fluorescent assays for pesticide residue, most of them are based on single emission, thus affecting the detection accuracy. Herein, a copper-based fluorescent nanozyme (Cu-BH) synthesized with dual-ligand, integrating fluorescence and oxidase-mimic into one spherical nanomaterial, was used firstly to establish a ratiometric approach for visual detection of thiophanate methyl (TM). Cu-BH possesses excellent oxidase-like activities, triggering the oxidation of colorless o-phenylenediamine (OPD) into yellow luminescent products (oxOPD, λem = 564 nm). Besides, the ligand of 2-amino-1,4-benzene-dicarboxylic acid imparts Cu-BH blue fluorescence (λem = 425 nm), which is quenched by oxOPD via inner filtration effect (IFE). The introduction of TM can prevent not only the oxidase-like activity remarkably but also the intrinsic luminescence of Cu-BH slightly because of the complexation of TM with Cu2+. As a result, the fluorescence intensity at 564 nm and 425 nm presents a significant decrease and a slight increase, respectively, producing a ratiometric fluorescent signal (F425/F564). Therefore, a novel ratiometric fluorescent strategy has been proposed to detect TM ranging from 0.1 to 100 μM with detection limit of 0.03 μM (S/N = 3). Besides, visual detection of TM can be achieved by RGB reading with the assistance of smartphone owing to the color variation from yellow to blue. This fluorescent nanozyme-based ratiometric strategy provides a specific method for the detection of TM in food samples.

Exploring the multifaceted roles of metal-organic frameworks in ecosystem regulation

Achieving microecological balance is a complex environmental challenge. This is because the equilibrium of microecological systems necessitates both the eradication of harmful microorganisms and preservation of the beneficial ones. Conventional materials predominantly target the elimination of pathogenic microorganisms and often neglect the protection of advantageous microbial species. Metal-organic frameworks (MOFs) with excellent physicochemical properties (such as crystalline particles of various dimensions with highly porous network topology, variable local networking structures, diverse compositions with functional groups, high specific surface areas and pore volumes for surface and porous guest molecular adsorption/adhesion/affinity/binding and separation) have been extensively studied as a type of bactericidal material. However, only recently, studies on using MOFs to protect microorganisms have been reported. This review provides a comprehensive analysis of the mechanisms and applications of various MOFs (such as ZIF-8, ZIF-90, HKUST-1, MOF-5, and MIL-101) in both microbial eradication and protection. Insights into previous studies on MOF development, the material-bacteria interaction mechanisms, and potential clinical and environmental applications are also elucidated. MOFs with different framework structures/topologies (zeolite, sodalite, scaffolding, diamond, one-dimensional, and spherical/cylindrical cavities/pore networks), particle dimensions, polyhedral, cubic, rod and open/uncoordinated metal centers or fully coordinated metal centers, and ligand functional groups are discussed to understand the varying degrees of activation and interaction of microorganisms. This review holds potential in guiding future research on the design, synthesis, utilization, and integration of MOFs for the targeted eradication and protection of microorganisms and generating novel MOFs with selective antimicrobial and protective properties. Moreover, this review delivers a timely update and outlines future prospects for MOFs and their interaction with microorganisms, emphasizing their potential as a promising candidate among the next generation of smart materials in the field of ecosystem regulation.

Excellent Laccase Mimic Activity of Cu-Melamine and Its Applications in the Degradation of Congo Red

Copper-based nanozyme has shown the superior in the oxidase-like activities due to its electron transfer ability between the Cu(I) and Cu(II) sites during the catalytic reactions. Herein, a Cu(I)-MOF (Cu-Mel) was readily synthesized by a traditional hydrothermal process using the precursors of Cu+ and melamine, which was then used in the laccase-like catalytic reactions for the first time. Some means, such as X-ray diffraction (XRD), Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), were employed to character the microstructure of the Cu-Mel. The catalytic oxidation of the 4-aminoantipyrine (4-AP) and 2,4-dichlorophenol (2,4-DP) was adopted to evaluate the laccase-like catalytic ability of the resulting Cu-Mel. The catalytic conditions including the temperatures, the presence of alcohols, and the ionic concentrations were varied to optimize the laccase-like activities, based on that, the highest laccase-like catalytic activity is presented with a higher maximum reaction rate (Vmax). The good storage stability is also presented by the Cu-Mel. The Cu-Mel was utilized in the degradation of Congo red, showing a good degradation efficiency. These findings facilitate the development of the laccase mimics and serve as a foundation for the design and applications of Cu-MOFs in the nanozyme realm.

A critical review on metal organic frameworks (MOFs)-based sensors for foodborne pathogenic bacteria detection

The pervasive threat of foodborne pathogenic bacteria necessitates advancements in rapid and reliable detection methods. Traditional approaches suffer from significant limitations including prolonged processing times, limited sensitivity and specificity. This review comprehensively examines the integration of metal organic frameworks (MOFs) with sensor technologies for the enhanced detection of foodborne pathogens. MOFs, with their unique properties such as high porosity, tunable pore sizes, and ease of functionalization, offer new avenues for sensor enhancement. This paper provides a comprehensive analysis of recent developments in MOFs-based sensors, particularly focusing on electrochemical, fluorescence, colorimetric, and surface-enhanced Raman spectroscopy sensors. We have provided a detailed introduction for the operational principles of these sensors, highlighting the role of MOFs play in enhancing their performance. Comparative analyses demonstrate MOFs' superior capabilities in enhancing signal response, reducing response time, and expanding detection limits. This review culminates in presenting MOFs as transformative materials in the detection of foodborne pathogens, paving the way for their broader application in ensuring food safety.

Aptamer modified CeCo MOF hybrid catalysts with multiple enzymatic activities for enhanced catalytic therapy of infected wounds

Designing and inventing synergistic emerging antimicrobial strategies is critical for mitigating potential resistance to conventional antibiotics. This task is challenging because these antimicrobial agents should need to eliminate bacteria, slow oxidative stress in wounds, and be safe and nontoxic. Here, we report a highly safe antimicrobial nanocatalyst for bacterial scavenging through aptamer-synergistic multienzyme activity. The nanocatalysts (termed as ASCM) were constructed by loading copper nanoparticles (Cu NPs), natural superoxide dismutase (SOD), and functionalized aptamers on bimetallic metal-organic frameworks (CeCo MOFs). The hybrid nanocatalysts exhibit remarkable SOD-like activity as well as its catalase (CAT)-, peroxidase (POD)- and glutathione peroxidase (GPx)-like activities to release highly toxic hydroxyl radicals (•OH) and oxygen (O2) to kill bacteria and relieve wound hypoxia. Systematic antimicrobial testing revealed that ASCM exhibited a high inactivation efficiency (>99 %) against both methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PA). Animal experiments have shown that ASCM can effectively treat MRSA-infected wounds and has a good biosafety profile while inhibiting the inflammatory response. Overall, this work describes the design of an efficient, strategically synergistic antibacterial nanocatalysts that can achieve safe bacterial scavenging and alleviate oxidative stress.

Recent advances in MOF-based nanozymes: Synthesis, activities, and bioapplications

Nanozymes have garnered considerable research interest for their unique capacity to bridge nanotechnology and biology. Current studies predominantly concentrate on exploring nanozymes with diverse catalytic activities and their potential applications across various disciplines. Among them, nanoscale metal-organic frameworks (MOFs) are promising nanomaterials for constructing nanozymes. In this review, we firstly introduce the general construction strategies for MOF-based nanozymes. In addition, we also classify the MOF-based nanozymes in detail based on their catalytic performance. Thirdly, the recent research progress of MOF-based nanozymes in the field of biosensing, cancer therapy, antibacterial infection, and antioxidation are also comprehensively reviewed. Finally, we discuss the current challenges and future perspectives of MOF-based nanozymes, with the aim of assisting in their construction and maximizing their potential in bioapplications. It is hoped that we could provide scientists in materials science and biomedical research with valuable and comprehensive information, fostering advancements in interdisciplinary fields.

Specific peptides targeting the myocardiocyte are prognostic markers for heart attack: Function of α-SMA protein

Myocardial infarction (MI) is a serious cardiovascular disease that often results in a significant decline in heart function and associated complications. α-SMA (α-smooth muscle cell actin) is an important biomarker in the process of cardiac remodeling and repair, and its expression level is closely related to myocardial remodeling and prognosis. Therefore, the purpose of this study was to investigate the potential of nanoparticles containing cardiomyocyte targeting peptides in predicting prognosis and α-SMA protein expression after myocardial infarction, with a view to providing new therapeutic strategies and clinical guidelines. In this study, a novel targeting nanoparticle was constructed, using cardiomyocyte specific peptides as targeting ligands, and characterized by loading different drugs. Subsequently, a mouse model of myocardial infarction was used to systematically evaluate the effect of nanoparticles on α-SMA protein expression and prognosis prediction ability after MI. The expression level of α-SMA was analyzed by Western blot and immunohistochemistry, and the prognosis was evaluated by cardiac function assessment. The study found that nanoparticles containing cardiomyocyte targeting peptides significantly increased α-SMA expression levels and improved heart function in animal models of myocardial infarction. Compared with the control group, the application of targeted nanoparticles was closely related to the level of myocardial cell repair and fibrosis, and could effectively predict the prognosis after myocardial infarction. Therefore, nanoparticles containing cardiomyocyte targeting peptides can not only effectively improve the expression of α-SMA, but also serve as an important prognostic tool after myocardial infarction.

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.

A NH2-Cu-MOF for promising antibacterial application

A copper-based metal-organic framework named NH2-Cu-MOF has been synthesized and utilized as an effective broad-spectrum antimicrobial material in this article. The obtained NH2-Cu-MOF exhibits satisfying antibacterial activity against both gram-positive bacteria (S. aureus and S. epidermidis) and gram-negative bacteria (E. coli and K. peneumoniae). Additionally, the biocompatibility of this NH2-Cu-MOF has been validated through animal studies, showing no significant adverse effects, thereby confirming its high biocompatibility. These findings prove that NH2-Cu-MOF has positive effects upon the treatment of bacteria-infected wounds, which holds great potential to be applied in biochemistry field.

Nanoarchitectonics of in Situ Antibiotic-Releasing Acicular Nanozymes for Targeting and Inducing Cuproptosis-like Death to Eliminate Drug-Resistant Bacteria

A series of progress has been made in the field of antimicrobial use of nanozymes due to their superior stability and decreased susceptibility to drug resistance. However, catalytically generated reactive oxygen species (ROS) are insufficient for coping with multidrug-resistant organisms (MDROs) in complex wound environments due to their low targeting ability and insufficient catalytic activity. To address this problem, chemically stable copper-gallic acid-vancomycin (CuGA-VAN) nanoneedles were successfully constructed by a simple approach for targeting bacteria; these nanoneedles exhibit OXD-like and GSH-px-like dual enzyme activities to produce ROS and induce bacterial cuproptosis-like death, thereby eliminating MDRO infections. The results of in vitro experiments showed that the free carboxylic acid of GA could react with the free ammonia of teichoic acid in the methicillin-resistant Staphylococcus aureus (MRSA) cell wall skeleton. Thus, CuGA-VAN nanoneedles can rapidly "capture" MRSA in liquid environments, releasing ROS, VAN and Cu2+ on bacterial surfaces to break down the MRSA barrier, destroying the biofilm. In addition, CuGA-VAN effectively promoted wound repair cell proliferation and angiogenesis to facilitate wound healing while ensuring biosafety. According to transcriptome sequencing, highly internalized Cu2+ causes copper overload toxicity; downregulates genes related to the bacterial glyoxylate cycle, tricarboxylic acid cycle, and oxidative respiratory chain; and induces lipid peroxidation in the cytoplasm, leading to bacterial cuproptosis-like death. In this study, CuGA-VAN was cleverly designed to trigger a cascade reaction of targeting, drug release, ROS-catalyzed antibacterial activity and cuproptosis-like death. This provides an innovative idea for multidrug-resistant infections.

Breaking the pH Limitation of Nanozymes: Mechanisms, Methods, and Applications

Although nanozymes have drawn great attention over the past decade, the activities of peroxidase-like, oxidase-like, and catalase-like nanozymes are often pH dependent with elusive mechanism, which largely restricts their application. Therefore, a systematical discussion on the pH-related catalytic mechanisms of nanozymes together with the methods to overcome this limitation is in need. In this review, various nanozymes exhibiting pH-dependent catalytic activities are collected and the root causes for their pH dependence are comprehensively analyzed. Subsequently, regulatory concepts including catalytic environment reconstruction and direct catalytic activity improvement to break this pH restriction are summarized. Moreover, applications of pH-independent nanozymes in sensing, disease therapy, and pollutant degradation are overviewed. Finally, current challenges and future opportunities on the development of pH-independent nanozymes are suggested. It is anticipated that this review will promote the further design of pH-independent nanozymes and broaden their application range with higher efficiency.

Research progress on antibacterial applications of metal-organic frameworks and their biomacromolecule composites

With the extensive use of antibiotics, resulting in increasingly serious problems of bacterial resistance, antimicrobial therapy has become a global concern. Metal-organic frameworks (MOFs) are low-density porous coordination materials composed of metal ions and organic ligands, which can form composite materials with biomacromolecules such as proteins and polysaccharides. In recent years, MOFs and their derivatives have been widely used in the antibacterial field as efficient antibacterial agents. This review offers a detailed summary of the antibacterial applications of MOFs and their composites, and the different synthesis methods and antibacterial mechanisms of MOFs and MOF-based composites are briefly introduced. Finally, the challenges and prospects of MOFs-based antibacterial materials in the rapidly developing medical field were briefly discussed. We hope this review will provide new strategies for the medical application of MOFs-based antibacterial materials.

Recent progress of metal-organic framework-based nanozymes with oxidoreductase-like activity

Nanozymes, a class of synthetic nanomaterials possessing enzymatic catalytic properties, exhibit distinct advantages such as exceptional stability and cost-effectiveness. Among them, metal-organic framework (MOF)-based nanozymes have garnered significant attention due to their large specific surface area, tunable pore size and uniform structure. MOFs are porous crystalline materials bridged by inorganic metal ions/clusters and organic ligands, which hold immense potential in the fields of catalysis, sensors and drug carriers. The combination of MOFs with diverse nanomaterials gives rise to various types of MOF-based nanozyme, encompassing original MOFs, MOF-based nanozymes with chemical modifications, MOF-based composites and MOF derivatives. It is worth mentioning that the metal ions and organic ligands in MOFs are perfectly suited for designing oxidoreductase-like nanozymes. In this review, we intend to provide an overview of recent trends and progress in MOF-based nanozymes with oxidoreductase-like activity. Furthermore, the current obstacles and prospective outlook of MOF-based nanozymes are proposed and briefly discussed. This comprehensive analysis aims to facilitate progress in the development of novel MOF-based nanozymes with oxidoreductase-like activity while serving as a valuable reference for scientists engaged in related disciplines.

Recent Progress and Prospect of Metal-Organic Framework-Based Nanozymes in Biomedical Application

A nanozyme is a nanoscale material having enzyme-like properties. It exhibits several superior properties, including low preparation cost, robust catalytic activity, and long-term storage at ambient temperatures. Moreover, high stability enables repetitive use in multiple catalytic reactions. Hence, it is considered a potential replacement for natural enzymes. Enormous research interest in nanozymes in the past two decades has made it imperative to look for better enzyme-mimicking materials for biomedical applications. Given this, research on metal-organic frameworks (MOFs) as a potential nanozyme material has gained momentum. MOFs are advanced hybrid materials made of inorganic metal ions and organic ligands. Their distinct composition, adaptable pore size, structural diversity, and ease in the tunability of physicochemical properties enable MOFs to mimic enzyme-like activities and act as promising nanozyme candidates. This review aims to discuss recent advances in the development of MOF-based nanozymes (MOF-NZs) and highlight their applications in the field of biomedicine. Firstly, different enzyme-mimetic activities exhibited by MOFs are discussed, and insights are given into various strategies to achieve them. Modification and functionalization strategies are deliberated to obtain MOF-NZs with enhanced catalytic activity. Subsequently, applications of MOF-NZs in the biosensing and therapeutics domain are discussed. Finally, the review is concluded by giving insights into the challenges encountered with MOF-NZs and possible directions to overcome them in the future. With this review, we aim to encourage consolidated efforts across enzyme engineering, nanotechnology, materials science, and biomedicine disciplines to inspire exciting innovations in this emerging yet promising field.

Propelling CuCo-based nanozyme design to new heights through triple enzyme-like power for high-efficiency bacterial eradication

Bacterial infection-related diseases are a serious issue that threatens human health, and it is highly desirable to develop a high-performance antibacterial agent to combat it. Herein, copper/cobalt-based metal sulfide nanoparticles (CCS NPs) as a new kind of antibacterial nanozyme were prepared by a facile hydrothermal method. Owing to its rich chemical states, the CCS NPs with intrinsic peroxidase- and oxidase-like activities could generate reactive oxygen species (ROS) to exert bactericidal capacity. The CCS NPs could also rapidly deplete glutathione (GSH) to aggravate the oxidative stress in bacteria, thus enhancing the sterilization effect. The results showed that, with the assistance of H2O2 at low concentrations, CCS NPs possessing peroxidase-like, oxidase-like, and GSH depletion activities could achieve remarkable antibacterial effects in vitro. The in vivo implantation demonstrated that CCS NPs with triple enzyme-like activities had efficient bacteria elimination and good biocompatibility in treating bacteria-infected wounds, indicating its wide potential application in the non-antibiotic treatment of bacteria-infected wounds.

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.

Diazo-reaction based dual-mode colorimetric-electrochemical sensing of nitrite in pickled food

Development of an effective and convenient sensor for sensitive detection of nitrites is of great concern since excessive amounts of nitrites can be harmful to both human health and the environment. In this work, Cu-MOF modified exfoliated graphite paper (EGP) was employed as a signal reporter to enable the visual and electrochemical dual-mode sensing of nitrites. Cu-MOFs were in situ synthesized on EGP, which exhibited an excellent oxidase enzyme-like activity to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) into its oxidation product (oxTMB). The multi-layer structure and the superior electrical conductivity of EGP not only facilitated the loading of the Cu-MOF nanozyme for colorimetric sensing but also enabled its use as an underlying backbone to support electroanalysis. Based on the recognition of nitrite through a highly specific diazo reaction between nitrite and oxTMB, the addition of nitrite caused the colorimetric sensing solution to change color from blue to green, which allowed for the colorimetric sensing of nitrite with a limit of detection (LOD) of 8.5 × 10-6 mol L-1. Meanwhile, the Cu-MOF/EGP electrochemical platform was employed for ratiometric detection of nitrite based on the electrochemical oxidation of nitrite and TMB. Compared with the colorimetric mode, the electrochemical mode possessed higher sensitivity with a LOD of 5.4 × 10-7 mol L-1, indicating the high sensitivity and accuracy of the proposed dual-mode sensing strategy. Furthermore, the determination of nitrite in different pickled food samples is demonstrated.

Different Dimensional Copper-Based Metal-Organic Frameworks with Enzyme-Mimetic Activity for Antibacterial Therapy

Fighting against bacterial infection and accelerating wound healing remain important and challenging in infected wound care. Metal-organic frameworks (MOFs) have received much attention for their optimized and enhanced catalytic performance in different dimensions of these challenges. The size and morphology of nanomaterials are important in their physiochemical properties and thereby their biological functions. Enzyme-mimicking catalysts, based on MOFs of different dimensions, display varying degrees of peroxidase (POD)-like activity toward hydrogen peroxide (H₂O₂) decomposition into toxic hydroxyl radicals (•OH) for bacterial inhibition and accelerating wound healing. In this study, we investigated the two most studied representatives of copper-based MOFs (Cu-MOFs), three-dimensional (3D) HKUST-1 and two-dimensional (2D) Cu-TCPP, for antibacterial therapy. HKUST-1, with a uniform and octahedral 3D structure, showed higher POD-like activity, resulting in H₂O₂ decomposition for •OH generation rather than Cu-TCPP. Because of the efficient generation of toxic •OH, both Gram-negative Escherichia coli and Gram-positive methicillin-resistant Staphylococcus aureus could be eliminated under a lower concentration of H₂O₂. Animal experiments indicated that the as-prepared HKUST-1 effectively accelerated wound healing with good biocompatibility. These results reveal the multivariate dimensions of Cu-MOFs with high POD-like activity, providing good potential for further stimulation of specific bacterial binding therapies in the future.