Engineering Inorganic Nanoflares with Elaborate Enzymatic Specificity and Efficiency for Versatile Biofilm Eradication

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

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

A ruthenium single atom nanozyme-based antibiotic for the treatment of otitis media caused by Staphylococcus aureus

Staphylococcus aureus (S. aureus) infection is a primary cause of otitis media (OM), the most common disease for which children are prescribed antibiotics. However, the abuse of antibiotics has led to a global increase in antimicrobial resistance (AMR). Nanozymes, as promising alternatives to traditional antibiotics, are being extensively utilized to combat AMR. Here, we synthesize a series of single-atom nanozymes (metal-C3N4 SANzymes) by loading four metals (Ag, Fe, Cu, Ru) with antibacterial properties onto a crystalline g-C3N4. These metal-C3N4 display a rob-like morphology and well-dispersed metal atoms. Among them, Ru-C3N4 demonstrates the optimal peroxidase-like activity (285.3 U mg-1), comparable to that of horseradish peroxidase (267.7 U mg-1). In vitro antibacterial assays reveal that Ru-C3N4 significantly inhibits S. aureus growth compared with other metal-C3N4 even at a low concentration (0.06 mg mL-1). Notably, Ru-C3N4 acts as a narrow-spectrum nanoantibiotic with relative specificity against Gram-positive bacteria. Biofilms formed by S. aureus are easily degraded by Ru-C3N4 due to its high peroxidase-like activity. In vivo, Ru-C3N4 effectively eliminates S. aureus and relieves ear inflammation in OM mouse models. However, untreated OM mice eventually develop hearing impairment. Due to its low metal load, Ru-C3N4 does not exhibit significant toxicity to blood, liver, or kidney. In conclusion, this study presents a novel SANzyme-based antibiotic that can effectively eliminate S. aureus and treat S. aureus-induced OM.

Carbon Dots in the Pathological Microenvironment: ROS Producers or Scavengers?

Reactive oxygen species (ROS), as metabolic byproducts, play pivotal role in physiological and pathological processes. Recently, studies on the regulation of ROS levels for disease treatments have attracted extensive attention, mainly involving the ROS-induced toxicity therapy mediated by ROS producers and antioxidant therapy by ROS scavengers. Nanotechnology advancements have led to the development of numerous nanomaterials with ROS-modulating capabilities, among which carbon dots (CDs) standing out as noteworthy ROS-modulating nanomedicines own their distinctive physicochemical properties, high stability, and excellent biocompatibility. Despite progress in treating ROS-related diseases based on CDs, critical issues such as rational design principles for their regulation remain underexplored. The primary cause of these issues may stem from the intricate amalgamation of core structure, defects, and surface states, inherent to CDs, which poses challenges in establishing a consistent generalization. This review succinctly summarizes the recently progress of ROS-modulated approaches using CDs in disease treatment. Specifically, it investigates established therapeutic strategies based on CDs-regulated ROS, emphasizing the interplay between intrinsic structure and ROS generation or scavenging ability. The conclusion raises several unresolved key scientific issues and prominent technological bottlenecks, and explores future perspectives for the comprehensive development of CDs-based ROS-modulating therapy.

Metal-doped carbon dots for biomedical applications: From design to implementation

Carbon dots (CDs), as a new kind of fluorescent nanomaterials, show great potential for application in several fields due to their unique nano-size effect, easy surface functionalization, controllable photoluminescence, and excellent biocompatibility. Conventional preparation methods for CDs typically involve top-down and bottom-up approaches. Doping is a major step forward in CDs design methodology. Chemical doping includes both non-metal and metal doping, in which non-metal doping is an effective strategy for modulating the fluorescence properties of CDs and improving photocatalytic performance in several areas. In recent years, Metal-doped CDs have aroused the interest of academics as a promising nano-doping technique. This approach has led to improvements in the physicochemical and optical properties of CDs by altering their electron density distribution and bandgap capacity. Additionally, the issues of metal toxicity and utilization have been addressed to a large extent. In this review, we categorize metals into two major groups: transition group metals and rare-earth group metals, and an overview of recent advances in biomedical applications of these two categories, respectively. Meanwhile, the prospects and the challenges of metal-doped CDs for biomedical applications are reviewed and concluded. The aim of this paper is to break through the existing deficiencies of metal-doped CDs and fully exploit their potential. I believe that this review will broaden the insight into the synthesis and biomedical applications of metal-doped CDs.

Advancements in the synthesis of carbon dots and their application in biomedicine

As a sort of fluorescent carbon nanomaterial with a particle size of less than 10 nm, carbon dots (CDs) have their own merits of good dispersibility in water, stable optical properties, strong chemical inertness, stable optical properties, and good biosecurity. These excellent peculiarities facilitated them like sensing, imaging, medicine, catalysis, and optoelectronics, making them a new star in the field of nanotechnology. In particular, the development of CDs in the fields of chemical probes, imaging, cancer therapy, antibacterial and drug delivery has become a hot topic in current research. Although the biomedical applications in CDs have been demonstrated in many research articles, a systematic summary of their role in biomedical applications is scarce. In this review, we introduced the basic information of CDs in detail, including synthesis approaches of CDs as well as their favorable properties including photoluminescence and low cytotoxicity. Subsequently, the application of CDs in the field of biomedicine was emphasized. Finally, the main challenges and research prospects of CDs in this field were proposed, which might provide some detailed information in designing new CDs in this promising biomedical field.

Nanomaterials with Enzyme-like Properties for Combatting Foodborne Pathogen Infections: Classifications, Mechanisms, and Applications in Food Preservation

During the transportation and storage of food, foodborne spoilage caused by bacterial and biofilm infection is prone to occur, leading to issues such as short shelf life, economic loss, and sensory quality instability. Therefore, the development of novel and efficient antibacterial agents capable of efficiently inhibiting bacteria throughout various stages of food processing, transportation, and storage is strongly recommended by researchers. The emergence of nanozymes is considered to be an effective candidate for inhibiting foodborne bacteria agents in the food industry. As potent antibacterial agents, nanozymes have the advantages of low cost, high stability, strong broad-spectrum antibacterial ability, and biocompatibility. Herein, we aim to summarize the classification status of various nanozymes. Furthermore, the general catalytic bacteriostatic mechanism of nanozymes against intracellular bacteria, planktonic bacteria, and biofilm activities are highlighted, mainly concerning the destruction of cell walls and/or membranes, reactive oxygen species regulation, HOBr/Cl generation, damage of intracellular components, and so forth. In particular, the review focuses on the pivotal role of nanozymes as antibacterial agents and delivery vehicles in the fields of food preservation applications. We look forward to the future prospects, especially in the field of food preservation, to promote broader applications based on antimicrobial nanozymes.

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.

Twin defect-rich Pt ultrathin nanowire nanozymes alleviate inflammatory skin diseases by scavenging reactive oxygen species

Nanozymes with superior antioxidant properties offer new hope for treating oxidative stress-related inflammatory skin diseases. However, lacking sufficient catalytic activity or having complex material designs limit the application of current metallic nanozymes in inflammatory skin diseases. Here, we report a simple and effective twin-defect platinum nanowires (Pt NWs) enzyme with multiple mimetic enzymes and broad-spectrum ROS scavenging capability for the treatment of inflammatory skin diseases in mice (including psoriasis and rosacea). Pt NWs with simultaneous superoxide dismutase, glutathione peroxidase and catalase mimetic enzyme properties exhibit cytoprotective effects against ROS-mediated damage at extremely low doses and significantly improve treatment outcomes in psoriasis- and rosacea-like mice. Meanwhile, these ultrasmall sizes of Pt NWs allow the nanomaterials to effectively penetrate the skin and do not produce significant biotoxicity. Therefore, Pt NWs have potential applications in treating diseases related to oxidative stress or inflammation.

Garlic-Derived Exosome-like Nanovesicles-Based Wound Dressing for Staphylococcus aureus Infection Visualization and Treatment

Garlic-derived exosome-like nanovesicles (GELNs) could function in interspecies communication and may serve as natural therapeutics to regulate the inflammatory response or as nanocarriers to efficiently deliver specific drugs. Staphylococcus aureus (S. aureus) is able to hide within host cells to evade immune clearance and antibiotics, leading to life-threatening infections. On-site detection and efficient treatment of intracellular S. aureus infection in wounds remain challenging. Herein, we report a thermosensitive, injectable, visible GELNs-based wound dressing, Van@GELNs/F127 hydrogel (gel Van@GELNs), which is H2O2-responsive and can slowly release vancomycin into host cells forS. aureus infection visualization and treatment in wounds. GELNs show inherent antibacterial activity, which is significantly enhanced after loading vancomycin. Both GELNs and Van@GELNs have the ability to be internalized by cells, so Van@GELNs are more effective than free vancomycin in killing S. aureus in RAW 264.7 macrophages. When applied to an S. aureus-infected wound on a mouse, the colorless HRP&ABTS/Van@GELNs/F127 solution immediately changes to a green hydrogel and shows better therapeutic effect than vancomycin. Thus, direct visualization by the naked eye and effective treatment of S. aureus infection in wounds are achieved by gel Van@GELNs. We anticipate gel Van@GELNs be applied for the theranostics of S. aureus infection diseases in the clinic in the near future.

Recent progress on bismuth-based light-triggered antibacterial nanocomposites: Synthesis, characterization, optical properties and bactericidal applications

Bacterial infections pose a seriously threat to the safety of the environment and human health. In particular, the emergence of drug-resistant pathogens as a result of antibiotic abuse and high trauma risk has rendered conventional therapeutic techniques insufficient for treating infections by these so-called "superbugs". Therefore, there is an urgent need to develop highly efficient and environmentally-friendly antimicrobial agents. Bismuth-based nanomaterials with unique structures and physicochemical characteristics have attracted considerable attention as promising antimicrobial candidates, with many demonstratingoutstanding antibacterial effects upon being triggered by broad-spectrum light. These nanomaterials have also exhibited satisfactory energy band gaps and electronic density distribution with improved photonic properties for extensive and comprehensive applications after being modified through various engineering methods. This review summarizes the latest research progress made on bismuth-based nanomaterials with different morphologies, structures and compositions as well as the different methods used for their synthesis to meet their rapidly increasing demand, especially for antibacterial applications. Moreover, the future prospects and challenges regarding the application of these nanomaterials are discussed. The aim of this review is to stimulate interest in the development and experimental transformation of novel bismuth-based nanomaterials to expand the arsenal of effective antimicrobials.

Carbon dot enhanced peroxidase-like activity of platinum nanozymes

As one of the most intriguing nanozymes, the platinum (Pt) nanozyme has attracted tremendous research interest due to its various catalytic activities but its application is still limited by its poor colloidal stability and low affinity to substrates. Here, we design a highly stable Pt@carbon dot (Pt@CD) hybrid nanozyme with enhanced peroxidase (POD)-like activity (specific activity of 1877 U mg-1). The Pt@CDs catalyze the decomposition of hydrogen peroxide (H2O2) to produce singlet oxygen and hydroxyl radicals and exhibit high affinity to H2O2 and high specificity to 3,3',5,5'-tetramethyl-benzidine. We reveal that both the hydroxyl and carbonyl groups of CDs could coordinate with Pt2+ and then regulate the charge state of the Pt nanozyme, facilitating the formation of Pt@CDs and improving the POD-like activity of Pt@CDs. Colorimetric detection assays based on Pt@CDs for H2O2, dopamine, and glucose with a satisfactory detection performance are achieved. Moreover, the Pt@CDs show a H2O2-involving antibacterial effect by destroying the cell membrane. Our findings provide new opportunities for designing hybrid nanozymes with desirable stability and catalytic performance by using CDs as nucleating templates and stabilizers.

Chitosan-chelated carbon dots-based nanozyme of extreme stability with super peroxidase activity and antibacterial ability for wound healing

Bacterial infection often leads to failed wound healing, causing one-third of death cases globally. However, antibacterial nanomaterials and natural enzymes face limitations including low antibacterial efficiency, lack of catalytic performance, low safety, and instability. Therefore, a new Fe/N-doped chitosan-chelated carbon dot-based nanozyme CS@Fe-N CDs was developed, which showed multiple advantages such as highly efficient antibacterial activity, excellent peroxidase-like activity, high stability, and high biocompatibility, shortening the wound healing time. The ultra-small (6.14 ± 3.38 nm) CS@Fe-N CDs nanozyme accelerated the H2O2 to ·OH conversion, exhibiting excellent antibacterial performance against Staphylococcus aureus. The antibacterial activity was increased by over 2000-fold after catalysis. The CS@Fe-N CDs nanozyme also displayed outstanding peroxidase activity (Vmax/Km = 1.77 × 10-6/s), 8.8-fold higher than horseradish peroxidase. Additionally, the CS@Fe-N CDs nanozyme exhibited high stability at broad pH values (pH 1-12) and temperature ranges (20-90 °C). In vitro evaluation of cell toxicity proved that the CS@Fe-N CDs nanozyme had negligible cytotoxicity. In vivo, wound healing experiments demonstrated that the CS@Fe-N CDs could shorten the healing time of rat wounds by at least 4 days, and even had a better curative effect than penicillin. In conclusion, this therapeutic platform provides an effective antibacterial and biologically safe healing strategy for skin wounds.

Ag-MXene as peroxidase-mimicking nanozyme for enhanced bacteriocide and cholesterol sensing

Reactive oxygen species (ROS) are ideal alternative antibacterial reagents for rapid and effective sterilization. Although a variety of ROS-based antimicrobial strategies have been developed, many are still limited by their inefficiency. Herein, we report the synthesis of the Ag-MXene nanozyme, which have superior peroxidase-like activity for antibacterial applications. As a result, Ag-MXene nanozyme can efficiently increase the level of intracellular ROS, converting H2O2 into hydroxyl radicals that effectively kill both Gram-negative and Gram-positive bacteria and disrupting the bacterial biofilm formation. Moreover, a sensitive and selective colorimetric biosensor was constructed for assaying cholesterol based on the Ag-MXene's prominent peroxidase-mimicking activity and the cholesterol oxidase cascade reaction. The biosensor exhibits high performance with a linear cholesterol detection range of 2-800 μM, and a detection limit of 0.6 μM. Ag-MXene nanozyme can be used for the rapid detection of cholesterol in serum without complicated sample pretreatment. Collectively, it is conceivable that the proposed Ag-MXene nanozyme could be used as a biocide and as a cholesterol sensor. This study provides a broad prospect for the rapid detection and sterilization of MXene nanozymes in the biomedical field.

Rational Engineering of a Multifunctional DNA Assembly for Enhanced Antibacterial Efficacy and Accelerated Wound Healing

DNA-based assemblies hold immense prospects for antibacterial application, yet are constrained by their poor specificity and deficient antibacterial delivery. Herein, the fabrication of a versatile rolling circle amplification (RCA)-sustained DNA assembly is reported, encoding simultaneously with multivalent aptamers and tandem antibacterial agents, for target-specific and efficient antibacterial application. In the compact RCA-sustained antibacterial platform, the facilely organized multivalent aptamers guarantee the target bacteria-specific delivery of sufficient antibacterial agents which is assembled through DNA-stabilizing silver nanostructures. It is shown that the biocompatible DNA system could enhance bacteria elimination and simultaneously facilitate wound healing in vivo. By virtue of the programmable RCA assembly, the present RCA-sustained system provides a highly modular and scalable approach to design versatile multifunctional therapeutic systems.

Detection and treatment of biofilm-induced periodontitis by histidine-doped FeSN nanozyme with ultra-high peroxidase-like activity

Pathogenic biofilm induced oral diseases have posed a significant treat to human health, such as periodontitis resulting from the formation of bacterial biofilm on teeth and gums. The traditional treatment methods such as mechanical debridement and antibiotic therapy encounter the poor therapeutic effect. Recently, numerous nanozymes with excellent antibacterial effect have been widely used in the treatment of oral diseases. In this study, a novel iron-based nanozyme (FeSN) generated by histidine-doped FeS2 with high peroxidase-like (POD-like) activity was designed for the oral biofilm removal and treatment of periodontitis. FeSN exhibited an extremely high POD-like activity, and enzymatic reaction kinetics and theoretical calculations had demonstrated its catalytic efficiency to be approximately 30 times than that of FeS2. The antibacterial experiments showed that FeSN had robust antibacterial activity against Fusobacterium nucleatum in the presence of H2O2, causing a reduction in the levels of glutathione reductase and ATP in bacterial cells, while increasing the level of oxidase coenzyme. The ultrahigh POD-like activity of FeSN allowed for easy detection of pathogenic biofilms and promoted the breakdown of biofilm structure. Furthermore, FeSN demonstrated excellent biocompatibility and low cytotoxicity to human fibroblast cells. In a rat model of periodontitis, FeSN exhibited significant therapeutic effects by reducing the extent of biofilm formation, inflammation, and alveolar bone loss. Taken together, our results suggested that FeSN, generated by self-assembly of two amino acids, represented a promising approach for biofilm removal and periodontitis treatment. This method has the potential to overcome the limitations of current treatments and provide an effective alternative for periodontitis treatment.

Carbon dots with light-responsive oxidase-like activity for colorimetric detection of dopamine and the catalytic mechanism

Introduction: Dopamine is one of the most significant neurotransmitters and plays an important role in the management of cognitive functions such as learning, memory, and behavior. The disorder of dopamine is associated with many major mental diseases. It is necessary to develop selective methods for the detection of dopamine. Methods: In this work, carbon dots (CDs) were synthesized by a solvothermal route using glutathione, L-histidine, and formamide as sources. Results: Under light irradiation, The CDs convert dissolved oxygen to singlet oxygen (1O2), which could oxidize TMB. When reduced dopamine was present, it suppressed the catalysis of CDs, then the absorption of the CDs-coupled TMB complex at 652 nm was diminished. Furthermore, it was revealed that the surface groups including hydroxyl, amino, carbonyl, and carboxyl groups of CDs were related to their light-responsive catalytic activity by surface modification. In the range of 0.5-15 μM, the CDs could afford a LOD of 0.25 μM for dopamine detection with fine linearity, also showing good selectivity. Discussion: The results from fetal bovine serum indicated the good applicability of the CDs in the determination of dopamine.

A comprehensive exploration of the latest innovations for advancements in enhancing selectivity of nanozymes for theranostic nanoplatforms

Nanozymes have captured significant attention as a versatile and promising alternative to natural enzymes in catalytic applications, with wide-ranging implications for both diagnosis and therapy. However, the limited selectivity exhibited by many nanozymes presents challenges to their efficacy in diagnosis and raises concerns regarding their impact on the progression of disease treatments. In this article, we explore the latest innovations aimed at enhancing the selectivity of nanozymes, thereby expanding their applications in theranostic nanoplatforms. We place paramount importance on the critical development of highly selective nanozymes and present innovative strategies that have yielded remarkable outcomes in augmenting selectivities. The strategies encompass enhancements in analyte selectivity by incorporating recognition units, refining activity selectivity through the meticulous control of structural and elemental composition, integrating synergistic materials, fabricating selective nanomaterials, and comprehensively fine-tuning selectivity via approaches such as surface modification, cascade nanozyme systems, and manipulation of external stimuli. Additionally, we propose optimized approaches to propel the further advancement of these tailored nanozymes while considering the limitations associated with existing techniques. Our ultimate objective is to present a comprehensive solution that effectively addresses the limitations attributed to non-selective nanozymes, thus unlocking the full potential of these catalytic systems in the realm of theranostics.

Tailoring the Surface and Composition of Nanozymes for Enhanced Bacterial Binding and Antibacterial Activity

With the advantages of diverse structures, tunable enzymatic activity, and high stability, nanozymes are widely used in medicine, chemistry, food, environment, and other fields. As an alternative to traditional antibiotics, nanozymes attract more and more attention from the scientific researchers in recent years. Developing nanozymes-based antibacterial materials opens up a new avenue for the bacterial disinfection and sterilization. In this review, the classification of nanozymes and their antibacterial mechanisms are discussed. The surface and composition of nanozymes are critical for the antibacterial efficacy, which can be tailored to enhance both the bacterial binding and the antibacterial activity. On the one hand, the surface modification of nanozymes enables binding and targeting of bacteria that improves the antibacterial performance of nanozymes including the biochemical recognition, the surface charge, and the surface topography. On the other hand, the composition of nanozymes can be modulated to achieve enhanced antibacterial performance including the single nanozyme-mediated synergistic and multiple nanozymes-mediated cascade catalytic antibacterial applications. In addition, the current challenges and future prospects of tailoring nanozymes for antibacterial applications are discussed. This review can provide insights into the design of future nanozymes-based materials for the antibacterial treatments.

A Multifunctional Nanozyme with NADH Dehydrogenase-Like Activity and Nitric Oxide Release under Near-Infrared Light Irradiation as an Efficient Therapeutic for Antimicrobial Resistance Infection and Wound Healing

In recent years, antimicrobial resistance (AMR) has become one of the greatest threats to human health. There is an urgent need to develop new antibacterial agents to effectively treat AMR infection. Herein, a novel nanozyme platform (Cu,N-GQDs@Ru-NO) is prepared, where Cu,N-doped graphene quantum dots (Cu,N-GQDs) are covalently functionalized with a nitric oxide (NO) donor, ruthenium nitrosyl (Ru-NO). Under 808 nm near-infrared (NIR) light irradiation, Cu,N-GQDs@Ru-NO demonstrates nicotinamide adenine dinucleotide (NADH) dehydrogenase-like activity for photo-oxidizing NADH to NAD+ , thus disrupting the redox balance in bacterial cells and resulting in bacterial death; meanwhile, the onsite NIR light-delivered NO effectively eradicates the methicillin-resistant Staphylococcus aureus (MRSA) bacterial and biofilms, and promotes wound healing; furthermore, the nanozyme shows excellent photothermal effect that enhances the antibacterial efficacy as well. With the combination of NADH dehydrogenase activity, photothermal therapy, and NO gas therapy, the Cu,N-GQDs@Ru-NO nanozyme displays both in vitro and in vivo excellent efficacy for MRSA infection and biofilm eradication, which provides a new therapeutic modality for effectively treating MRSA inflammatory wounds.

Engineering a gold nanoparticles-carbon dots nanocomposite with pH-flexibility for monitoring hydrogen peroxide released from living cells

Constructing nanozymes with satisfactory catalytic efficiency under physiological conditions is still in great demand for facilitating the advancement of biocatalysts. We herein present a gold nanoparticles-carbon dots nanocomposite (Au-CDs) as an efficient photo-activated nanozyme for monitoring H2O2 released from living cells. The integration of CDs with AuNPs remarkably accelerates the catalytic activity at neutral pH via engaging Mn3+ ions as the mediators. Meanwhile, the reserved cyclodextrin cavities also enhance the adsorption capacity towards chromogenic substrates through host-guest interactions. Moreover, taking advantage of the inhibitory effect of H2O2 on the photo-oxidation ability of the Au-CDs nanocomposite, the Au-CDs based colorimetric method was able to realize in situ assessment of the hydrogen peroxide (H2O2) released from living cells. This method paves a new way to establish a promising biosensing platform for unraveling biological events.

Carbon quantum dots as a nitric oxide donor can promote wound healing of deep partial-thickness burns in rats

INTRODUCTION

In this study, a new carbon quantum dots-NO (CQDs-NO) that is based on spermidine trihydrochloride and can be used as a nitric oxide donor was prepared using a two-step hyperthermia-intermittent ultrasonic method, after which its healing effect on deep partial-thickness burn wounds was tested in rats.

MATERIALS AND METHODS

CQDs-NO were prepared by a two-step hyperthermia-intermittent ultrasonic method. NO-released rate and biocompatibility of CQDs-NO were tested. The biological functions of CQDs-NO were measured by scratch assay, Western blotting, histology, and transcriptome sequencing.

RESULTS

CQDs-NO with a concentration of 1 μg/mL and 5 μg/mL showed no cytotoxicity. CQDs-NO could release NO when co-cultured with cells or glutathione peroxidase. We also found that CQDs-NO promotes the biological processes such as angiogenesis, cell-substrate adhesion, extracellular matrix organization, cell migration, and wound healing in human umbilical vein endothelial cells (HUVEC). Additionally, CQDs-NO promoted wound healing of deep partial-thickness burn by enhancing vascularization, matrix deposition, as well as regulating the inflammatory reactions of wounds.

CONCLUSIONS

CQDs-NO could be used as an alternative method for deep partial-thickness burn healing.

Plasma-activated liquids for mitigating biofilms on food and food contact surfaces

Plasma-activated liquids (PALs) are emerging and promising alternatives to traditional decontamination technologies and have evolved as a new technology for applications in food, agriculture, and medicine. Contamination caused by foodborne pathogens and their biofilms has posed challenges and concerns to the food industry in terms of safety and quality. The nature of the food and the food processing environment are major factors that contribute to the growth of various microorganisms, followed by the biofilm characteristics that ensure their survival in severe environmental conditions and against traditional chemical disinfectants. PALs show an efficient impact against microorganisms and their biofilms, with various reactive species (short- and long-lived ones), physiochemical properties, and plasma processing factors playing a crucial role in mitigating biofilms. Moreover, there is potential to improve and optimize disinfection strategies using a combination of PALs with other technologies for the inactivation of biofilms. The overarching aim of this study is to build a better understanding of the parameters that govern the liquid chemistry generated in a liquid exposed to plasma and how these translate into biological effects on biofilms. This review provides a current understanding of PALs-mediated mechanisms of action on biofilms; however, the precise inactivation mechanism is still not clear and is an important part of the research. Implementation of PALs in the food industry could help overcome the disinfection hurdles and can enhance biofilm inactivation efficacy. Future perspectives in this field to expand existing state of the art to seek breakthroughs for scale-up and implementation of PALs technology in the food industry are also discussed.

Detection of Gastric Cancer-Associated d-Amino Acids and Carcinoembryonic Antigen by Colorimetric and Immuno ECL Sensing Platform Based on the Catalysis of N/S-Doped Carbon Dots @ N-Rich Porous Carbon Nanoenzyme

Gastric cancer is a malignant tumor, and its early diagnosis remains challenging due to the lack of simple and sensitive detection methods and specific biomarkers. In this work, to improve the detection reliability, we developed a dual-mode detection strategy for the detection of two biomarkers associated with it. First, an N- and S-doped carbon dots-N-rich porous carbon nanoenzyme (N/S-CDs@NC) was prepared by a two-step pyrolysis of thiourea-penetrated zinc-based zeolite imidazole framework. It was then combined with the 3,3',5,5'-tetramethylbenzidine-H₂O₂ system for the colorimetric detection of d-amino acids (i.e., d-proline (d-Pro) and d-alanine (d-Ala)) in saliva, based on d-amino acid oxidase catalyzing d-amino acid oxidation to produce H₂O₂. In this way, the low detection limits (S/N = 3) of d-Pro and d-Ala were 0.14 and 0.35 μM, respectively. Furthermore, N/S-CDs@NC was combined with the luminol-H₂O₂ electrochemiluminescence (ECL) system and magnetic immune accumulation/separation strategy to detect the carcinoembryonic antigen (CEA) in serum. The porous N/S-CDs@NC could facilitate participant contact, promote the generation of hydroxyl radical (^•OH), and electrostatically attract ^•OH, thereby significantly amplifying the ECL signal of luminol and improving the signal stability. Thus, the detection mode showed considerable sensitivity and selectivity, with a low detection limit of 0.26 pg mL^-1. The strategy proposed in this work can also be used for the detection of other disease markers by substituting the recognition elements, thus having good application potential.

Structure design mechanisms and inflammatory disease applications of nanozymes

Nanozymes are artificial enzymes with high catalytic activity, low cost, and good biocompatibility, and have received ever-increasing attention in recent years. Various inorganic and organic nanoparticles have been found to exhibit enzyme-like activities and are used as nanozymes for diverse biomedical applications ranging from tumor imaging and therapeutics to detection. However, their further clinical applications are hindered by the potential toxicity and long-term retention of nanomaterials in vivo. Clarifying the catalytic mechanism of nanozymes and identifying the key factors responsible for their behavior can guide the design of nanozyme structure, enlighten the ways to improve their enzyme-like activities, and minimize the dosage of nanozymes, leading to reduced toxicity to the human body for a real biomedical application prospect. In particular, inflammation occurring in numerous diseases is closely related to reactive oxygen species, and the active oxygen scavenging ability of nanozymes potentially exerts excellent therapeutic effects on inflammatory diseases. In this review, we systematically summarize the structure-activity relationship of nanozymes, including regulation strategies for size and morphology, surface structure, and composition. Based on the structure-activity mechanisms, a series of chemically designed nanozymes developed to target various inflammatory diseases are briefly summarized.

A comprehensive review on the applications of carbon-based nanostructures in wound healing: from antibacterial aspects to cell growth stimulation

A wound is defined as damage to the integrity of biological tissue, including skin, mucous membranes, and organ tissues. The treatment of these injuries is an important challenge for medical researchers. Various materials have been used for wound healing and dressing applications among which carbon nanomaterials have attracted significant attention due to their remarkable properties. In the present review, the latest studies on the application of carbon nanomaterials including graphene oxide (GO), reduced graphene oxide (rGO), carbon dots (CDs), carbon quantum dots (CQDs), carbon nanotubes (CNTs), carbon nanofibers (CNFs), and nanodiamonds (NDs) in wound dressing applications are evaluated. Also, a variety of carbon-based nanocomposites with advantages such as biocompatibility, hemocompatibility, reduced wound healing time, antibacterial properties, cell-adhesion, enhanced mechanical properties, and enhanced permeability to oxygen has been reported for the treatment of various wounds.

Triple-synergistic MOF-nanozyme for efficient antibacterial treatment

The abuse of antibiotics makes bacterial infection an increasingly serious global health threat. Reactive oxygen species (ROS) are the ideal alternative antibacterial approach for quick and effective sterilization. Although various antibacterial strategies based on ROS have been developed, many of them are still limited by insufficient antibacterial efficiency. Here, we have developed an acid-enhanced dual-modal antibacterial strategy based on zeolitic imidazolate frameworks-8 (ZIF8) -derived nanozyme. ZIF8, which can release Zn2+, is chosen as the carrier to integrate glucose oxidase (GOx) and gold nanoparticles (Au NPs) which can produce ROS via a cascade catalytic reaction. Thus, the bactericidal capability of ROS and Zn2+ have been integrated. More importantly, gluconic acid, a "by-product" of the catalytic reaction, can generate an acidic environment to promote both the ROS-producing and Zn2+-releasing, enhancing the overall antibacterial performance further. This triple-synergistic strategy exhibits extraordinary bactericidal ability at a low dosage of 4 μg/mL (for S. aureus) and 8 μg/mL (for E. coli), which shows a great potential of MOF-derived nanozyme for efficient bacterial eradication and diverse biomedical applications.

Tannin coordinated nanozyme composite-based hybrid hydrogel eye drops for prophylactic treatment of multidrug-resistant Pseudomonas aeruginosa keratitis

Pseudomonas aeruginosa infection is a severe acute suppurative ulcer that engulfs virtually the entire tissue in a short period and leads to devastating destruction. Antibiotic therapy is a common approach for the prophylaxis and treatment of P. aeruginosa infection. However, it is often associated with serious side effects, complications, and multidrug resistance. Therefore, it has been a long-standing challenge to explore safe and effective methods for controlling P. aeruginosa infection. Herein, tannin-coordinated nanozyme composite-based hybrid hydrogels (TCNH) are developed and characterized for the prophylactic treatment of P. aeruginosa and multidrug-resistant P. aeruginosa infections using mouse keratitis as the animal model. The TCNH eye drops are constructed by photoinitiated free radical polymerization of acetylated gelatin solution containing self-synthesized tannin-coordinated Co₃O₄/Ag nanozyme composite. The as-prepared TCNH displays good dispersibility, peroxidase-like activity and in vitro/in vivo biocompatibility. The nanozyme composite in TCNH seems to penetrate the interior of bacteria and exhibited significant broad-spectrum antibacterial activity owing to its intrinsic and nanozymic catalytic properties. Furthermore, TCNH eye drops can be successfully applied to treat P. aeruginosa and multidrug-resistant P. aeruginosa keratitis. The findings of this study reveal the potential of tannin-coordinated nanozyme composite-based hybrid hydrogel eye drops for treating infectious diseases.

Biofilms: Formation, Research Models, Potential Targets, and Methods for Prevention and Treatment

Due to the continuous rise in biofilm-related infections, biofilms seriously threaten human health. The formation of biofilms makes conventional antibiotics ineffective and dampens immune clearance. Therefore, it is important to understand the mechanisms of biofilm formation and develop novel strategies to treat biofilms more effectively. This review article begins with an introduction to biofilm formation in various clinical scenarios and their corresponding therapy. Established biofilm models used in research are then summarized. The potential targets which may assist in the development of new strategies for combating biofilms are further discussed. The novel technologies developed recently for the prevention and treatment of biofilms including antimicrobial surface coatings, physical removal of biofilms, development of new antimicrobial molecules, and delivery of antimicrobial agents are subsequently presented. Finally, directions for future studies are pointed out.

H2O2-activated in situ polymerization of aniline derivative in hydrogel for real-time monitoring and inhibition of wound bacterial infection

Wound is highly susceptible to bacterial infection, which can cause chronic wound and serial complications. However, timely treatment is hampered by the lack of real-time monitoring of wound status and effective therapeutic systems. Herein, in situ biosynthesis of functional conjugated polymer in artificial hydrogel was developed via the utilization of biological microenvironment to realize monitoring in real time of wound infection and inhibition of bacteria for the first time. Specially, an easily polymerizable aniline dimer derivative (N-(3-sulfopropyl) p-aminodiphenylamine, SPA) was artfully in situ polymerized into polySPA (PSPA) in calcium alginate hydrogel, which was initiated via the catalysis of hydrogen peroxide (H₂O₂) overexpressed in infected wound to produce hydroxyl radical (•OH) by preloaded horseradish peroxidase (HRP). Benefitting from outstanding near infrared (NIR) absorption of PSPA, such polymerization can be ingeniously used for real-time monitoring of H₂O₂ via naked-eye and photoacoustic signal, as well as NIR light-mediated photothermal inhibition of bacteria. Furthermore, combining the persistent chemodynamic activity of •OH, the in vivo experimental data proved that the wound healing rate was 99.03% on the 11th day after treatment. Therefore, the present work opens the way to manipulate in situ biosynthesis of functional conjugated polymer in artificial hydrogels for overcoming the issues on wound theranostics.

Single-Atom Nanozymes: Fabrication, Characterization, Surface Modification and Applications of ROS Scavenging and Antibacterial

Nanozymes are nanomaterials with intrinsic natural enzyme-like catalytic properties. They have received extensive attention and have the potential to be an alternative to natural enzymes. Increasing the atom utilization rate of active centers in nanozymes has gradually become a concern of scientists. As the limit of designing nanozymes at the atomic level, single-atom nanozymes (SAzymes) have become the research frontier of the biomedical field recently because of their high atom utilization, well-defined active centers, and good natural enzyme mimicry. In this review, we first introduce the preparation of SAzymes through pyrolysis and defect engineering with regulated activity, then the characterization and surface modification methods of SAzymes are introduced. The possible influences of surface modification on the activity of SAzymes are discussed. Furthermore, we summarize the applications of SAzymes in the biomedical fields, especially in those of reactive oxygen species (ROS) scavenging and antibacterial. Finally, the challenges and opportunities of SAzymes are summarized and prospected.

Engineering efficient artificial nanozyme based on chitosan grafted Fe-doped-carbon dots for bacteria biofilm eradication

Bacterial biofilms have evoked worldwide attention owing to their serious threats to public health, but how to effectively eliminate bacterial biofilms still remains great challenges. Here, we rationally designed a novel and vigorous chitosan grafted Fe-doped-carbon dots (CS@Fe/CDs) as an efficient artificial nanozyme to combat rigid bacterial biofilms through the selective activation of Fenton-like reaction-triggered peroxidase-like catalytic activity and the synergistic antibacterial activity of CS. On the one hand, the peroxidase-like catalytic activity made CS@Fe/CDs catalyze H₂O₂ for producing hydroxyl radicals (•OH), resulting in efficient cleavage of extracellular DNA (eDNA). On the other hand, CS was capable of binding with the negatively charged cell membrane through electrostatic interaction, changing the cell membrane permeability and causing cell death within bacterial biofilms. Based on their synergistic effects, the fragments of bacterial biofilm and exposed bacteria were persistently eradicated. Remarkably, CS@Fe/CDs-based nanozyme not only enabled the effective destroying of gram-positive Staphylococcus aureus (S. aureus) biofilms, but also completely eliminated gram-negative Pseudomonas aeruginosa (P. aeruginosa) biofilms, showing great potential as a promising anti-biofilm agent against bacteria biofilms. This proposed synergistic strategy for bacterial biofilm eradication might offer a powerful modality to manage of bacterial biofilm fouling in food safety and environmental protection.

Emerging Prospects of Nanozymes for Antibacterial and Anticancer Applications

The ability of some nanoparticles to mimic the activity of certain enzymes paves the way for several attractive biomedical applications which bolster the already impressive arsenal of nanomaterials to combat deadly diseases. A key feature of such 'nanozymes' is the duplication of activities of enzymes or classes of enzymes, such as catalase, superoxide dismutase, oxidase, and peroxidase which are known to modulate the oxidative balance of treated cells for facilitating a particular biological process such as cellular apoptosis. Several nanoparticles that include those of metals, metal oxides/sulfides, metal-organic frameworks, carbon-based materials, etc., have shown the ability to behave as one or more of such enzymes. As compared to natural enzymes, these artificial nanozymes are safer, less expensive, and more stable. Moreover, their catalytic activity can be tuned by changing their size, shape, surface properties, etc. In addition, they can also be engineered to demonstrate additional features, such as photoactivated hyperthermia, or be loaded with active agents for multimodal action. Several researchers have explored the nanozyme-mediated oxidative modulation for therapeutic purposes, often in combination with other diagnostic and/or therapeutic modalities, using a single probe. It has been observed that such synergistic action can effectively by-pass the various defense mechanisms adapted by rogue cells such as hypoxia, evasion of immuno-recognition, drug-rejection, etc. The emerging prospects of using several such nanoparticle platforms for the treatment of bacterial infections/diseases and cancer, along with various related challenges and opportunities, are discussed in this review.

Recent development in antibacterial activity and application of nanozymes in food preservation

Nanozymes with excellent broad-spectrum antibacterial properties offers an alternative strategy for food preservation. This review comprehensively summarized the antibacterial mechanisms of nanozymes, including the generation of reactive oxygen species (ROS) and the destruction of biofilms. Besides, the primary factors (size, morphology, hybridization, light, etc.) regulating the antibacterial activity of different types of nanozymes were highlighted in detail, which provided effective guidance on how to design highly efficient antibacterial nanozymes. Moreover, this review presented elaborated viewpoints on the unique applications of nanozymes in food preservation, including the selection of nanozymes loading matrix, fabrication techniques of nanozymes-based antibacterial films/coatings, and the recent advances in the application of nanozymes-based antibacterial films/coatings in food preservation. In the end, the safety issues of nanozymes have also been mentioned. Overall, this review provided new avenues in the field of food preservation and displayed great prospects.

Incorporating Boron into Niobic Acid Nanosheets Enables Generation of Multiple Reactive Oxygen Species for Superior Antibacterial Action

Photocatalytic therapy is an alternative antibacterial pathway but most photocatalysts are limited by light absorption, charge transfer and insufficient production of reactive oxygen species (ROS). Herein, the authors utilize boron doped niobic acid nanosheets (B-HNbO₃ NSs) as a superior photocatalytic antibacterial platform. The experimental results and density functional theory (DFT) confirm that superior photocatalytic therapy activity is mainly due to boron doping, which not only promotes the generation and separation of electrons and holes, but also enhances the adsorption of water and oxygen molecules on B-HNbO₃ NSs. Consequently, multiple ROS including hydroxyl radicals (•OH), superoxide radicals (•O₂^- ), and singlet oxygen (¹ O₂ ) are generated under light irradiation, resulting in outstanding bacterial killing ability of B-HNbO₃ NSs. Besides, oxygen is produced during the therapy process, thus alleviating the inflammatory response caused by hypoxia. Furthermore, molecular dynamics (MD) simulations verify that the nanosheet structure makes it possess strong electrostatic attraction for bacterial cell membranes, leading to physical insertion and damage to bacterial cells. Therefore, bactericidal rates for four types of bacteria are all more than 99%, proving its excellent and broad-spectrum antibacterial capacity. Moreover, B-HNbO₃ NSs could be applied to treat biofilm-coated medical devices in vivo, suggesting its possibility in practical application.

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.

Reversible capturing and voltammetric determination of circulating tumor cells using two-dimensional nanozyme based on PdMo decorated with gold nanoparticles and aptamer

A novel cytosensor was constructed for the ultrasensitive detection and nondestructive release of circulating tumor cells (CTCs) by combining Au nanoparticles-loaded two-dimensional bimetallic PdMo (2D Au@PdMo) nanozymes and electrochemical reductive desorption. The 2D Au@PdMo nanozymes possessed high-efficiency peroxidase-like activity and were assembled with an aptamer composed of a thiol-modified epithelial specific cell adhesion molecule (EpCAM) to strengthen CTCs adhesion. Moreover, the electrode surface was decorated with highly fractal Au nanostructures (HFAuNSs) composites due to the similarity in fractal nanostructure with the CTCs membrane to enhance the CTCs anchoring efficiency and release capability. The captured CTCs could be further efficiently dissociated and nondestructively released from the modified electrodes upon electrochemical reductive desorption. The designed cytosensor showed an excellent analytical performance, with a wide linear range from 2 to 1 × 10⁵ cells mL^-1 and low limit of detection (LOD) of 2 cells mL^-1 (S/N = 3) at the working potential in the range  -0.6 to 0.2 V. A satisfactory CTCs release reaching a range of 93.7-97.4% with acceptable RSD from 3.55 to 6.41% and good cell viability was obtained. Thus, the developed cytosensor might provide a potential alternative to perform CTC-based liquid biopsies, with promising applications in early diagnosis of tumors. Preparation and mechanism of desorption of the cytosensor based on 2D Au@PdMo nanozymes and electrochemical reductive desorption for the detection and release of CTCs. A Preparation procedure of the Apt/Au@PbMo bioconjugates. B Fabrication process of the sandwich-type cytosensor. C Electrochemical signal produced by the Au@PdMo nanozymes. D Mechanism of electrochemical reductive desorption for CTCs release.

Construction of a Mesoporous Ceria Hollow Sphere/Enzyme Nanoreactor for Enhanced Cascade Catalytic Antibacterial Therapy

Nanozyme has been regarded as one of the antibacterial agents to kill bacteria via a Fenton-like reaction in the presence of H₂O₂. However, it still suffers drawbacks such as insufficient catalytic activity in near-neutral conditions and the requirement of high H₂O₂ levels, which would minimize the side effects to healthy tissues. Herein, a mesoporous ceria hollow sphere/enzyme nanoreactor is constructed by loading glucose oxidase in the mesoporous ceria hollow sphere nanozyme. Due to the mesoporous framework, large internal voids, and high specific surface area, the obtained nanoreactor can effectively convert the nontoxic glucose into highly toxic hydroxyl radicals via a cascade catalytic reaction. Moreover, the generated glucose acid can decrease the localized pH value, further boosting the peroxidase-like catalytic performance of mesoporous ceria. The generated hydroxyl radicals could damage severely the cell structure of the bacteria and prevent biofilm formation. Moreover, the in vivo experiments demonstrate that the nanoreactor can efficiently eliminate 99.9% of bacteria in the wound tissues and prevent persistent inflammation without damage to normal tissues in mice. This work provides a rational design of a nanoreactor with enhanced catalytic activity, which can covert glucose to hydroxyl radicals and exhibits potential applications in antibacterial therapy.

A pH-triggered fluorescence-switchable extracellular vesicle for tracing drug release and improving drug delivery

Extracellular vesicles have shown great potential in drug delivery for clinical applications. However, some obstacles still need to be overcome before their clinical translation, including on demand release of drugs to improve the efficacy and monitoring of the drug release process to ascertain drug dosage. Herein, a pH-triggered fluorescence-switchable extracellular vesicle as a smart nanocarrier is fabricated by loading zwitterionic fluorescent carbon dots (CDs) into macrophage cell-secreted vesicles to achieve improved drug delivery and real-time monitoring of drug release. When circulating in the blood, the zwitterionic CDs loaded in the vesicles can tightly bind the chemotherapeutic drug DOX through electrostatic interactions to avoid premature drug unload. The nanocarriers have a long blood circulation half-life of 15.12 h and a high tumor accumulation of 9.88% ID/g. Meanwhile, the fluorescence of the CDs is in the "off" state due to the fluorescence inner filter effect (IFE) between the DOX and the CDs. When the nanocarriers enter the tumor cells, the low pH of the lysosome leads to charge reversal of the CDs. DOX can be quickly released through electrostatic repulsion and the fluorescence of the CDs turns "on" after the release of the drugs, thus enabling an improved drug delivery and real-time tracking of the drug release process.

Sweetsop-like α-Fe2O3@CoNi catalyst with superior peroxidase-like activity for sensitive and selective detection of hydroquinone

Hydroquinone (HQ) is poorly degradable in the ecological environment and is highly toxic to human health even at a low concentration. The colorimetric method has the advantages of low cost and fast analysis, which provides the possibility for simple and rapid detection of HQ. In this work, a new colorimetric method has been developed for HQ detection based on a peroxidase-like catalyst, α-Fe2O3@CoNi. This sweetsop-like α-Fe2O3@CoNi catalyst enables H2O2 to produce hydroxyl (˙OH), leading to the oxidization of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxTMB. In the presence of HQ, the blue oxTMB is reduced to colorless, which allows for colorimetric detection of HQ in water samples. This method has been validated by detecting HQ in water samples with high selectivity, rapid response, broad detection range (0.50 to 30 μM), and low detection limit (0.16 μM).

Ultrasmall copper nanoclusters with multi-enzyme activities

Reactive oxygen species (ROS) as a key messenger of signal transduction mediate physiological activities, however, oxidative stress produced by excessive ROS can cause the destruction of cell homeostasis, which will result in a series of diseases. Therefore, effective control of ROS level is critical to the homeostasis of the cell. Here, we reported that glutathione (GSH)-stabilized copper nanoclusters (CuNCs) with about 9 Cu atoms can functionally mimic three major antioxidant enzymes, namely catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD). The rate of H2O2 decomposition was calculated to be ∼0.23 mg L-1 s-1 when the concentration of CuNCs was 100 μg mL-1. The SOD-like activity by catalyzing the disproportionation of superoxide to H2O2 and O2 reached 25.6 U mg-1 when the effective inhibition rate was ∼55.4%. Intracellular ROS scavenging studies further identified that CuNCs can obviously protect cells from oxidative stress and the cell viability recovered to above 90%. Hence, we expect that ultrasmall CuNCs will provide good therapeutic potential in the future treatment of ROS-related diseases.