Deciphering the catalytic mechanism of superoxide dismutase activity of carbon dot nanozyme

Dual-mechanism detecting fluoride and tetracycline in food matrices using red-emitting carbon dots

Excessive exposure to fluoride and tetracycline can cause severe dental damage, including tetracycline-induced tooth discoloration and dental fluorosis. Herein, we introduce a dual-mechanism sensing strategy using red-emitting carbon dots (R-CDs) for the independent detection of fluoride and tetracycline. A key advantage of R-CDs as sensors is their ability to selectively identify both analytes through long-wavelength emission with a large Stokes shift. For fluoride detection, we developed a fluorescence-enhanced sensor based on R-CDs-Fe3+ via a competitive binding mechanism. Meanwhile, tetracycline detection was achieved using a fluorescence-quenching sensor leveraging static quenching and the internal filter effect (IFE). The successful quantification of fluoride and tetracycline in food matrices demonstrates the practical potential of R-CDs in food safety monitoring. Additionally, this study presents a novel framework for designing multi-target detection systems using a single type of carbon dots across different sensing mechanisms.

Metal-free antioxidant nanozyme incorporating bioactive hydrogel as an antioxidant scaffold for accelerating bone reconstruction

Oxidative stress at bone defect sites mediates inflammation and even osteoblast apoptosis, severely hindering the repair process. While current antioxidant bone tissue engineering (BTE) scaffolds lack broad-spectrum reactive oxygen species (ROS) scavenging capability and structure-activity elucidation. Herein, we report a three-dimensional nitrogen-doped carbon antioxidant nanozyme (ZIFC) derived from metal-organic frameworks, which exhibits cascading superoxide dismutase- and catalase-like activities, along with the ability to scavenge other harmful free radicals. Through the experimental studies and theoretical calculations, we reveal that the catalase-like activity arises from the synergistic catalytic interaction between graphitized pyridinic nitrogen and its adjacent carbon atom. Moreover, hybrid double network hydrogel integrated with ZIFC is utilized to construct composite scaffold (Gel/ZIFC) by 3D printing. In vivo transcriptome analysis confirms that Gel/ZIFC can rapidly activate antioxidant defense system and suppress local inflammation under oxidative stress microenvironment, thereby protecting cells from oxidative damage. Subsequently, owing to the unique osteoinductive property of carbon nanomaterials and the osteoconductive property of 3D-printed scaffold, Gel/ZIFC composite scaffold exhibits desirable bone repair efficacy. The elucidation of structure-activity relationship and therapeutic mechanism provides new insights and guidance for devising antioxidant BTE scaffolds, and demonstrates their feasibility for clinical application.

Multifunctional nanozymatic biosensors: Awareness, regulation and pathogenic bacteria detection

It is estimated that approximately 700,000 fatalities occur annually due to infections attributed to various pathogens, which are capable of dissemination via multiple environmental vectors, including air, water, and soil. Consequently, there is an urgent need to enhance and refine rapid detection technologies for pathogens to prevent and control the spread of associated diseases. This review focuses on applying nanozymes in constructing biosensors, particularly their advancement in detecting pathogenic bacteria. Nanozymes, which are nanomaterials exhibiting enzyme-like activity, combine unique magnetic, optical, and electronic properties with structural diversity. This blend of characteristics makes them highly appealing for use in biocatalytic applications. Moreover, their nanoscale dimensions facilitate effective contact with pathogenic bacteria, leading to efficient detection and antibacterial effects. This article briefly summarizes the development, classification, and strategies for regulating the catalytic activity of nanozymes. It primarily focuses on recent advancements in constructing biosensors that utilize nanozymes as probes for sensitively detecting pathogenic bacteria. The discussion covers the development of various optical and electrochemical biosensors, including colorimetric, fluorescence, surface-enhanced Raman scattering (SERS), and electrochemical methods. These approaches provide a reliable solution for the sensitive detection of pathogenic bacteria. Finally, the challenges and future development directions of nanozymes in pathogen detection are discussed.

Development of an aminoguanidine hybrid hydrogel composites with hydrogen and oxygen supplying performance to boost infected diabetic wound healing

Diabetic wounds tend to develop into non-healing wounds associated with a complex inflammatory microenvironment of uncontrollable bacterial infection, reactive oxygen species (ROS) accumulation, and chronic hypoxia. This study developed a multifunctional hydrogel system by integrating aminoguanidine and hydrogen and oxygen gas-release nanoparticles (PAP NPs) into phenylboronic acid-modified quaternized chitosan and an oxidized dextran network. Hollow mesoporous Prussian blue (HPB) nanozymes with superoxide dismutase- and catalase-like activities are promising bioreactors for simultaneously alleviating ROS accumulation and hypoxia by converting elevated endogenous hydrogen peroxide (H2O2) into oxygen in diabetic wounds. Simultaneously, incorporating ammonia borane (AB)-loaded HPB NPs served as a source of hydrogen, further reducing ROS overproduction and modulating pro-inflammatory cytokine responses. Aminoguanidine in the hydrogel network inhibits the formation of advanced glycation end products (AGEs), inhibiting skin cell apoptosis and promoting their proliferation and migration. Moreover, the hydrogel exhibited significant mechanical characteristics and self-healing capacity owing to the Schiff base and phenylboronate ester linkages. Incorporating PAP NPs into the hydrogel produced an exceptional photothermal response, effectively eradicating bacteria with a mortality rate exceeding 95 % within 10 min and protecting the wound from potential infections. In vivo studies demonstrated that PAP@Gel significantly accelerated the healing of infected diabetic wounds by mitigating oxidative stress, enhancing oxygenation, inhibiting inflammation and AGE formation, and reversing bacterial infections. This study highlights a promising nanomedicine approach for designing future diabetic wound dressings, providing a novel strategy for catalytic ROS scavenging and synergistic hydrogen and oxygen therapies.

Synergistic microglial modulation by laminarin-based platinum nanozymes for potential intracerebral hemorrhage therapy

Abnormal microglial activation increases inflammation, causing significant brain damage after intracerebral hemorrhage (ICH). To aid recovery, treatments should regulate oxidative stress and inhibit the M1-like phenotype (pro-inflammation) of microglia. Recently, antioxidant nanozymes have emerged as tools for modulating microglial states, but detailed studies on their role in ICH treatment are limited. To address this, we developed an ultra-small (3-4 nm) laminarin-modified platinum nanozyme (Pt@LA) for the synergistic regulation of microglial polarization, offering a novel therapeutic strategy for ICH. Pt@LA effectively scavenges reactive oxygen species (ROS) through superoxide dismutase (SOD) and catalase (CAT)-like activities. Laminarin may inhibit the Dectin-1 receptor on microglia and its inflammatory pathway, Syk/NF-κB, reducing neuroinflammation. In vitro, Pt@LA decreased pro-inflammatory microglia and cytokine expression by inhibiting the Dectin-1/Syk/NF-κB and ROS-mediated NF-κB pathways. Furthermore, Pt@LA protected neurons, inhibited glial scar formation, and improved neurological function in ICH rats. Overall, this study presents Pt nanozymes based on naturally extracted laminarin and explores their application in alleviating oxidative stress and neuroinflammation after ICH, bridging nanozyme research and neuroscience.

Antibacterial properties of folic acid-based hydrogel loaded with CeCDs and its potential application in food preservation

The development of novel preservation techniques capable of food safety and nutrition retention has received extensive attention. Herein, a biocompatible and biodegradable composite folate/zinc supramolecular hydrogel loaded with Ce-doped carbon dots (named FZCC hydrogel) has been fabricated. This hydrogel was synthesized through hydrogen bonds or metal-ligand coordination and held the advantages of superior antibacterial properties, self-healing properties, and washability. Particularly, CeCDs in the hydrogel possessed photodynamic capabilities under white light irradiation, endowing broad antibacterial ability against both Gram-positive and Gram-negative bacteria. The growth inhibition rate reached up to 83.98 % and 80.30 % for S. aureus and E. coli. Moreover, the hydrogels can release high concentrations of Zn2+ over 15 days, resulting in a sustained antimicrobial effect. The application of FZCC hydrogel to pakchoi cabbages, apples, and cooked meat can effectively prolong the shelf life and ensure food quality by controlling microbial contaminations, providing great potential for designing sustainable active food packaging materials.

Dual oxygen supply system of carbon dot-loaded microbubbles with acoustic cavitation for enhanced sonodynamic therapy in diabetic wound healing

Diabetic wounds present significant treatment challenges due to their complex microenvironment, marked by persistent inflammation from bacterial infections, hypoxia caused by diabetic microangiopathy, and biofilm colonization. Sonodynamic therapy (SDT) offers potential for treating such wounds by targeting deep tissues with antibacterial effects, but its efficacy is limited by hypoxic conditions and biofilm barriers. To overcome these obstacles, we developed a novel approach using oxygen-carrying microbubbles loaded with Mn2+-doped carbon dots (MnCDs@O2MBs) to enhance SDT and disrupt biofilms. Through precursor screening and design, MnCDs are engineered to exhibit tailored properties of sonodynamic activity and enzyme-like catalytic capabilities. This system provides a dual oxygen supply for amplifying the SDT effects: MnCDs, serving as a sonosensitizer, also chemically convert excess H2O2 at infection sites into oxygen, while the O2MBs physically release oxygen through ultrasound-induced cavitation. The cavitation effect also disrupts biofilms, improving the delivery of sonosensitizers and boosting SDT efficacy. In a diabetic wound model, this strategy downregulated TLR, NF-κB, and TNF inflammatory pathways, reduced pro-inflammatory factor secretion, promoted angiogenesis, and accelerated wound healing, thereby acting as a promising treatment approach for diabetic wound healing.

Hyperbranched polymer dots enhance hair follicle regeneration via Wnt/β-catenin activation: A drug-free nanozyme-based approach to hair growth therapy

BACKGROUND

Hair loss affects millions worldwide, yet current pharmacological treatments remain limited in efficacy and long-term sustainability. The Wnt/β-catenin pathway plays a crucial role in hair follicle regeneration, providing a promising target for novel therapeutic interventions.

METHODS

This study investigates the potential of Hyperbranched Polymer Dots (HPD) as a novel nanotherapeutic for hair follicle regeneration. Using a C57BL/6 mouse model, we assessed the effects of topically applied HPD on hair growth, follicular proliferation, and key molecular markers of follicular activation. Optical coherence tomography (OCT), histological analysis, and immunofluorescence staining for Ki67 and β-catenin were performed to evaluate follicular activity at multiple time points.

RESULTS

HPD treatment significantly accelerated hair regrowth (p < 0.05) and enhanced follicular density compared to minoxidil-treated controls. Immunofluorescence analysis revealed upregulation of Ki67 and β-catenin, indicating enhanced follicular stem cell proliferation and activation of the Wnt/β-catenin pathway. Furthermore, HPD-treated mice exhibited increased melanin deposition, suggesting early follicular entry into the anagen phase.

CONCLUSION

Our findings demonstrate that HPD serves as a potent activator of hair follicle regeneration, surpassing the efficacy of conventional minoxidil treatment. By modulating Wnt/β-catenin signaling and enhancing follicular proliferation, HPD presents a promising nanomedicine-based approach for non-invasive hair restoration therapies. Future studies should focus on optimizing HPD formulations for clinical translation in treating androgenetic alopecia and related hair disorders.

Synergistic healing of diabetic wounds through photothermal and peroxidase-like activity of heterogeneous Bi2S3/Au nanoparticles

Bacterial resistance and biofilm formation around diabetic wounds are major challenges that make the wounds difficult to heal. It is crucial for diabetic wound healing to improve the microenvironment around the wounds. In this study, a novel strategy for diabetic wound healing is developed by combining the peroxidase (POD)-like enzyme activity and photothermal therapy (PTT) to protect against bacterial infections around the wounds. Heterogeneous bismuth sulfide/gold nanoparticles (Bi2S3/Au NPs) are synthesized through a two-step wet chemical route. Results show that Bi2S3/Au nanozymes display high POD-like enzyme activity and can effectively convert H2O2 into ˙OH. The antibacterial rate against S. aureus and E. coli bacteria is 99.8 ± 0.03% and 99.9 ± 0.01%, respectively, in the presence of H2O2 under near-infrared light (NIR) irradiation. Animal experiments on infected diabetic wounds demonstrate that the synergistic actions of the Bi2S3/Au NPs significantly inhibit the formation of biofilms caused by bacteria, and promote the deposition of collagen and the formation of epithelial and dermal tissue. This study provides a promising solution for innovative therapy of refractory diabetic wounds, which is of great significance for reducing the abuse of antibiotics and the production of drug-resistant bacteria.

Rapid visual detection of glutathione in vegetables and distinguishing multiple sulfur-containing compounds by smartphone-assisted sensor based on calcined PPy@CuNi-ZIF-67 nanozyme with enhanced oxidase-like activity

In this work, polypyrrole-coated Cu, Ni co-doped ZIF-67 (PPy@CuNi-ZIF-67) was designed and prepared via a facile method. Calcined PPy@CuNi-ZIF-67 exhibited highly efficient oxidase-like activity and possessed excellent capacity to oxidize colorless 3,3',5,5'-tetramethyl benzidine (TMB) into blue oxidation products (oxTMB) within 4 min. Glutathione (GSH) and sulfur-containing compounds can inhibit its oxidase-like activity. Based on this principle, an effective colorimetric method was developed in combination with a smartphone for efficient, sensitive, and visual detection of GSH. Under optimal conditions, good linearity was achieved in the range of 0.83-33.33 μM, and the visual detection limit was 0.27 μM. Moreover, based on the response difference of different sulfur-containing compounds to different chromogenic substrates, a new array sensor was constructed with three chromogenic substrates. The array sensor was proven to quickly distinguish five sulfur-containing compounds at a concentration as low as 8.3 μM in combination with principal component analysis and hierarchical clustering analysis.

Nanozyme-based biosensors for food contaminants detection: advances, challenges, and prospects

The presence of food contaminants poses a growing threat to public health. Developing advanced and reliable biosensing methods with high sensitivity, specificity, and reproducibility for detecting food contaminants is an urgent requirement for food safety control. Nanozymes, recognized for their enzyme-mimicking catalytic activities and the unique physicochemical properties of nanomaterials, have been extensively utilized in the development of diverse biosensors for food safety assays. Recent years have witnessed an exponential surge in relevant publications, garnering considerable research interest. This review summarizes recent advancements in the catalytic mechanisms of peroxidase- and oxidase-like nanozymes and provides a comprehensive discussion on the construction, sensing mechanisms, and practical applications of nanozymes-based biosensors developed for detecting food contaminants over the past five years. These biosensors include colorimetric, fluorescence, chemiluminescent, electrochemical, surface-enhanced Raman scattering, multi-modal, and other types, used for detecting food contaminants such as mycotoxins, pathogens, pesticides, veterinary drugs, illegal additives, and heavy metals. The review also addresses current challenges and prospects in this field, aiming to summarize advancements and promote further exploration of nanozyme-based sensing platforms to guarantee food safety.

Engineering biocompatible carbon dots nano-enzymes hydrogel for efficient antioxidative and anti-inflammatory treatment of dry eye disease

Dry eye disease (DED) is a complex and multifactorial ocular surface disease. Reactive oxygen species (ROS) are of pivotal importance in the inflammatory processes and biological dysfunction associated with DED. In this study, an injectable hydrogel, designated as OHACDgel, was created by combining oxidized HA-containing aldehyde groups (OHA) and gelation (gel) via dynamic covalent linkages of the hydrazine bonds, is employed as the carrier, while polyethylene imine-functionalized carbon dots (PEI-CD) can form dynamic chemical bonds with the hydrogel, thus prolonging the retention time of the ocular surface. OHACDgel has been demonstrated to diminish ROS overproduction markedly, reduce the expression of pro-inflammatory factors, inhibit the transformation of macrophages into a pro-inflammatory phenotype, reverse corneal epithelial defects, restore goblet cell function, and enhance tear secretion. Furthermore, the biocompatibility of OHACDgel has been demonstrated, presenting a rapid and straightforward therapeutic option for potential applications in DED.

Nanoarchitectured biomass-waste derived activated charcoal nanozymes and its application in visual analysis of nitrite in pickled food

The emerging field of nanozymes has introduced unprecedented opportunities and challenges for activated charcoal materials derived from biomass waste. By incorporating specific nanostructures or elements, it is possible to overcome the limitations of traditional activated charcoal, such as insufficient catalytic active sites and poor electron transfer efficiency, thereby unlocking its full potential for various applications. In this study, we successfully synthesized trace Fe-doped activated charcoal (Fe-AC) with a graphene-like structure from biomass waste. The Fe atoms were uniformly dispersed on the activated charcoal support, which possessed a high surface area. This not only significantly increased the number of catalytic active sites but also enhanced electron transfer efficiency, substrate mobility, and collision probability. Compared to pristine activated charcoal, the synthesized Fe-AC exhibited multiple enzyme-mimetic activities, including oxidase-like, peroxidase-like, and catalase-like activities. By leveraging its peroxidase-like activity in conjunction with nitrite-specific diazotization reactions, we developed a portable, smartphone-assisted, on-site ratiometric colorimetric hydrogel sensor for nitrite detection. Utilizing smartphone-based digital imaging, this sensor enabled the quantitative analysis of nitrite at concentrations ranging from 1 to 200 μmol/L, with a detection limit as low as 1 μmol/L. The approximate range of hazardous nitrite concentrations could be easily identified with the naked eye, and the proposed strategy was successfully applied to real sample analysis. This sensor not only maximizes the utilization of waste resources, thereby reducing production costs, but also offers greater economic feasibility and environmental sustainability. Given these advantages, it holds promise for broader applications in various fields.

Keto-Oxygen on Graphitic Surface with Downshifted p-Band Center Achieves Efficient Metal-Free Transfer Hydrogenation of Nitroarenes

The critical challenge in utilizing carbon-based nanomaterials is identifying the active site. Herein, we demonstrate the keto-oxygen on the graphitic surface as active sites for catalytic transfer hydrogenation (CTH) and present an efficient nanocrystalline diamond (ND)-derived carbon-based catalyst for metal-free CTH of nitroarenes to imine with 99.9% nitrobenzene conversion and exclusive selectivity (99.9%). By selectively deconstructing the graphitic surface or eliminating carbonyl groups, the graphite-conjugated carbonyl group is confirmed as the catalytically active site. Moreover, kinetic studies display the lower activation barrier of benzylalcohol than that of nitrobenzene (88.8 vs 119.1 kJ mol-1, respectively), indicating that alcohol dehydrogenation occurs prior to the activation of nitrobenzene. Density functional theory calculations reveal the downshifted p-band center of keto-oxygen on the sp2 hybrid C surface affords moderate adsorption of benzaldehyde intermediates, which accelerates the formation of active H for the following hydrogenation step and is responsible for the high catalytic activity.

Photoswitchable Antioxidant and Prooxidant Activities of Mg-Doped Carbon Dot Nanozymes as Antibacterial and Anti-Inflammatory Agents

Multienzymatic nanozymes hold great potential in therapeutics due to their higher catalytic efficiency and multifunctionality. However, flexibly switching the antioxidant and prooxidant activities of multienzymic nanozymes at the same lesion remains a challenge. Herein, we design magnesium-doped carbon dot (Mg-CD) nanozymes with photoswitchable antioxidant and prooxidant activities under physiological conditions. The Mg-CD nanozymes exhibit superoxide dismutase (SOD)-like activity and can scavenge singlet oxygen and hydroxyl radicals without illumination. Interestingly, the antioxidant activity can be converted to oxidase-like activity under visible light illumination, producing singlet oxygen and superoxide anions. The mechanism of the switchable activities is attributed to the fact that coordination between magnesium and the CD skeleton enhances the excited-state electron transfer of singlet states and the energy transfer of triplet electrons. Therefore, Mg-CDs can act as antibacterial and anti-inflammatory agents. Mg-CDs exhibit antibacterial rates exceeding 99% within 5 min under illumination. They can scavenge reactive oxygen species, thereby showing excellent capacity in treating inflammatory wounds caused by lipopolysaccharide. These photoswitchable antioxidant and prooxidant activities of CD nanozymes offer an effective strategy for better manipulating the versatility of nanozymes, expanding their intelligent biomedical applications.

Advancements in herbal medicine-based nanozymes for biomedical applications

ABSTRACT

Nanozymes are a distinct category of nanomaterials that exhibit catalytic properties resembling those of enzymes such as peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). Nanozymes derived from Chinese herbal medicines exhibit the catalytic functions of their enzyme mimics, while retaining the specific medicinal properties of the herb (termed "herbzymes"). These nanozymes can be categorized into three main groups based on their method of synthesis: herb carbon dot nanozymes, polyphenol-metal nanozymes, and herb extract nanozymes. The reported catalytic activities of herbzymes include POD, SOD, CAT, and GPx. This review presents an overview of the catalytic activities and potential applications of nanozymes, introduces the novel concept of herbzymes, provides a comprehensive review of their classification and synthesis, and discusses recent advances in their biomedical applications. Furthermore, we also discuss the significance of research into herbzymes, including the primary challenges faced and future development directions.

Visual detection of glyphosate by Al3+-regulated carbon dots/CdTe quantum dots ratiometric fluorescent sensing platform

Highly sensitive monitoring of pesticides has garnered attention for food safety. Here, a ratiometric fluorescent probe (AG-CDs-Al3+/CdTe QDs) was fabricated for specific and sensitive sensing of glyphosate. Surface modifications revealed the chelation-enhanced fluorescence process between the surface -OH of AG-CDs and Al3+. Positively charged green-emission AG-CDs-Al3+ assembled with negatively charged red-emission CdTe QDs, and photoinduced electron transfer (PET) occurred from CdTe QDs to AG CDs-Al3+. Glyphosate specifically coordinated with Al3+, causing remarkable variations in F500/F630 (linear range, 0.2-4.0 μM; detection limit, 5.7 nM) and a distinguishable green-yellow-red color change on the paper platform (linear range, 0.5-8.0 μM; detection limit, 26 nM). Furthermore, for real sample analysis, the sensor has the advantages of fast response (5 min), excellent accuracy (spiked recoveries, 95.0-105.0 %), high precision (relative standard deviation, < 3.33 %), and superior specificity, which endowed the designed sensing platform with great potential practicality in the field of food analysis.

Optimizing cancer therapy through metal organic frameworks-based nanozymes

Cancer remains a leading global health challenge, with conventional treatments facing limitations due to drug resistance and adverse effects arising from tumor heterogeneity. Nanozymes, nanomaterials mimicking natural enzymes, have emerged as promising therapeutic agents owing to their catalytic efficiency, stability, and biocompatibility. Among nanozymes, MOFs-based nanozymes are particularly attractive due to the inherent tunability of MOFs, which allows for precise control over their structure, porosity, and catalytic activity. This review comprehensively explores the recent advancements in optimizing cancer therapy through MOFs-based nanozymes. We delve into the classification of these nanozymes based on their enzyme-mimicking activities, including peroxidase, oxidase, catalase, and superoxide dismutase, and discuss their underlying catalytic mechanisms. Additionally, emerging single-atom nanozymes are discussed as a distinct category. Furthermore, we highlight the diverse therapeutic strategies employing MOFs-based nanozymes, such as starvation therapy, oxygen supply, catalytic therapy, glutathione depletion, and activation of therapeutic agents within tumor microenvironment. By exploiting the unique properties of MOFs, these nanozymes demonstrate enhanced therapeutic efficacy in various cancer treatment modalities, including chemotherapy, radiotherapy, photodynamic therapy, and sonodynamic therapy. This review underscores the significant potential of MOFs-based nanozymes as a versatile platform for developing next-generation cancer therapeutics, offering improved targeting, reduced systemic toxicity, and enhanced treatment outcomes.

Inflammation-Targeting Multienzyme Activity Carbon Dots Loaded with Methotrexate for Synergistic Immunotherapy in Rheumatoid Arthritis

In rheumatoid arthritis (RA), excessive reactive oxygen species (ROS) and chronic inflammation drive damage to the synovium, cartilage, and bone. Developing precise and synergistic therapy for RA is crucial for improving remission rates. Here, carbon dots (CDs) with multienzyme activity and inflammation-targeting capabilities are designed to deliver methotrexate (MTX) for synergistic RA treatment. Specifically, positively charged CDs with porphyrin iron cores and amino-functionalized surfaces are synthesized to simultaneously scavenge hydrogen peroxide, superoxide anions, and hydroxyl radicals. Conjugation of MTX-loaded CDs with polyethylene glycol (CDs2-P@M) via Schiff base reaction significantly prolongs in vivo circulation time. In collagen-induced arthritis rats, CDs2-P@M accumulates in the diseased joints, reducing ROS and inflammatory cytokines, reprogramming macrophage phenotypes, inhibiting osteoclast activation, and markedly improving arthritis symptoms. This approach targets the RA microenvironment, minimizing MTX toxicity and effectively reshaping immune homeostasis, halting inflammation and tissue destruction, thus offering a new paradigm for RA immunotherapy.

Colorimetric detection of methotrexate leveraging the halogen peroxidase-mimicking activity of Bi2WO6 nanoflowers

This study explores Bi2WO6 nanoflowers as novel haloperoxidase (HPO) mimetics and their application in analytical science, aiming to develop an efficient colorimetric method for methotrexate (MTX) detection. Bi2WO6 nanoflowers were synthesized via a modified hydrothermal method and exhibited bromoperoxidase- and iodoperoxidase-like activities, catalyzing the bromination of phenol red (PR) and iodination of thymol blue (TB). After optimizing the reaction conditions, the kinetic parameters, including the Michaelis-Menten constant (Km) and maximum reaction velocity (Vmax), exceeded those of most of the reported HPO nanozymes. Investigation of the catalytic mechanism identified singlet oxygen (1O2) as a reactive intermediate. Leveraging the inhibitory effect of MTX on Bi2WO6-based nanozymes, a colorimetric assay for MTX was developed, demonstrating excellent detection performance in terms of a wide linear range and a low detection limit. Furthermore, the developed assay exhibited reliable performance in detecting actual samples. This study validates Bi2WO6 nanoflowers as efficient HPO nanozymes and provides a reliable approach for the rapid and simple detection of MTX.

Integrated cascade antioxidant nanozymes-Cu5.4O@CNDs combat acute liver injury by regulating retinol metabolism

Background: Acute liver failure (ALF) represents a critical medical condition marked by the abrupt onset of hepatocyte damage, commonly induced by etiological factors such as hepatic ischemia/reperfusion injury (HIRI) and drug-induced hepatotoxicity. Across various types of liver injury, oxidative stress, heightened inflammatory responses, and dysregulated hepatic retinol metabolism are pivotal contributors, particularly in the context of excessive reactive oxygen species (ROS). Methods: C-dots were combined with Cu5.4O USNPs to synthesize a cost-effective nanozyme, Cu5.4O@CNDs, which mimics the activity of cascade enzymes. The in vitro evaluation demonstrated the ROS scavenging and anti-inflammatory capacity of Cu5.4O@CNDs. The therapeutic potential of Cu5.4O@CNDs was evaluated in vivo using mouse models of hepatic ischemia/reperfusion injury and LPS/D-GalN induced hepatitis, with transcriptome analysis conducted to clarify the mechanism underlying hepatoprotection. Results: The Cu5.4O@CNDs demonstrated superoxide dismutase (SOD) and catalase (CAT) enzyme activities, as well as hydroxyl radical (·OH) scavenging capabilities, effectively mitigating ROS in vitro. Furthermore, the Cu5.4O@CNDs exhibited remarkable targeting efficacy towards inflammation cells induced by H2O2 and hepatic tissues in murine models of hepatitis, alongside exhibiting favorable biocompatibility in both in vitro and in vivo settings. Moreover, it has been demonstrated that Cu5.4O@CNDs effectively scavenged ROS, thereby enhancing cell survival in vitro. Additionally, Cu5.4O@CNDs exhibited significant therapeutic efficacy in mice models of HIRI and lipopolysaccharide-induced acute lung injury (LPS-ALI). This efficacy was achieved through the modulation of the ROS response and hepatic inflammatory network, as well as the amelioration of disruptions in hepatic retinol metabolism. Conclusions: In summary, this study demonstrates that Cu5.4O@CNDs exhibit significant potential for the treatment of various acute liver injury conditions, suggesting their promise as an intervention strategy for clinical application.

Nanozymes-Mediated Lateral Flow Assays for the Detection of Pathogenic Microorganisms and Toxins: A Review from Synthesis to Application

In today's context, there is an increasing awareness among individuals regarding the importance of healthy and safe food consumption. Consequently, there is a growing demand for food products that are safeguarded against the detrimental effects of pathogens and harmful microbial metabolites. Actually, these organisms and their associated toxins pose a significant risk to food safety and are recognized as a critical threat to human health because of their capacity to induce foodborne infections and intoxications. Consequently, in order to address such challenges, it is imperative to enhance recognizing systems comprising bio/nanosensors for detections, which are trustworthy, quick, beneficial and economical. The advent of digital color imaging technology has led to the gradual establishment of lateral flow assays (LFAs) as one of the most significant sensors for point-of-care applications. Unlike colloidal gold nanoparticles (AuNPs), nanozymes offer enhanced color intensity through target-induced precise enrichment of nanozymes at the test line. Additionally, they amplify the color signal by facilitating the catalytic oxidation of colorless substrates into colored products. This dual functionality presents significant potential for the development of well-organized LFAs. In light of this, significant attempts are dedicated to the development of nanozyme-based LFAs. This review aims to outline recent advancements in the synthesis and design of nanozymes with varying compositions that exhibit distinct activities, as well as the structure and employment of nanozyme-based LFAs for the detection of pathogenic microorganisms and their associated toxins. Furthermore, the existing challenges and prospective development directions are outlined to assist readers in advancing the nanozyme-based LFAs performance.

Advances in the Treatment of Spinal Cord Injury with Nanozymes

Spinal cord injury (SCI) with increasing incidence can lead to severe disability. The pathological process involves complex mechanisms such as oxidative stress, inflammation, and neuron apoptosis. Current treatment strategies focusing on the relief of oxidative stress and inflammation have achieved good effects, while many problems and challenges remain such as the side effect and short half-life of the therapeutic agents. Nanozymes exhibiting good biocatalytic activities can sustainably scavenge free radicals, inhibit neuroinflammation, and protect the neurons. With high stability in physiological conditions and cost-effectiveness, the nanozymes provide a new strategy for SCI treatment. In this Review, we outline the advances of nanozymes and their enzyme-mimicking activities and highlight the progress in the intervention of SCI-adopting nanozymes. We also propose future directions and clinical translation for the nanozyme strategy against SCI.

Metal-based mesoporous polydopamine with dual enzyme-like activity as biomimetic nanodrug for alleviating liver fibrosis

Liver fibrosis is a common pathological stage in the development of several chronic liver diseases, and early intervention can effectively reverse the developing process. Excessive reactive oxygen species (ROS) can promote the activation of hepatic stellate cells (HSCs), but existing treatments have not addressed this problem. In this study, different metal-based mesoporous polydopamine (MPDA) was prepared by the soft template method, and their free radical scavenging abilities, as well as the efficacy and safety of the carriers were investigated, so as to select Cu2+-coordinated MPDA (CMP) as the optimal nanocarrier. CMP exhibited superior SOD- and CAT-like activities compared to MPDA. Subsequently, a novel liver-targeted nanodrug delivery system (Cur/CMPH) with biosafety was constructed. Moreover, Cur/CMPH consisted of CMP loaded with the antifibrotic drug curcumin (Cur/CMP) and coated hyaluronic acid (HA) with liver-targeting properties on the surface of Cur/CMP, thus effectively intervening in the progression of liver fibrosis. Cur/CMPH possessed uniform particle size, negative Zeta potential, excellent antioxidant capacity, and pH-responsive drug release. Furthermore, Cur/CMPH in vitro studies demonstrated efficient cellular uptake, inhibition of the proliferation of HSCs, and excellent intracellular ROS scavenging without cytotoxicity. Besides, Cur/CMPH had specific targeting effect on fibrotic liver as well as good accumulation ability. In vivo studies, Cur/CMPH showcased the combined therapeutic effect of Cur and CMP, which significantly decreased the deposition of collagen fibers and alleviated the degree of liver fibrosis with good biosafety. In summary, the construction of Cur/CMPH opens up a novel idea in the field of nanodrug delivery systems for the treatment of liver fibrosis.

Achieving Room-Temperature Phosphorescence in Solution Phase from Carbon Dots Confined in Nanocrystals

Carbon dots (CDs) have attracted growing interest in the construction of room-temperature phosphorescent (RTP) materials. However, in the solution phase of CDs, it is still challenging to obtain efficient and stable phosphorescent emission due to the intense quenching effect by dissolved oxygen and solvent molecules. Herein, we report robust phosphorescence in the solution phase, achieved by encapsulating citrate-derived CDs into NaYF4 nanocrystals via a one-step method of high-temperature coprecipitation. Combined characterizations show that the triplet emission from CDs is related to the abundance of C=O in the CDs, the formation of ionic-bond networks around the CDs, and the spatial confinement and quenching inhibition effects of NaYF4 nanocrystals. Notably, the transition of CDs@NaYF4 from hydrophobicity to hydrophilicity can be easily achieved by simple surface modulation of NaYF4 nanocrystals, which allows the RTP of CDs to be maintained in either polar or nonpolar solvents. In addition, CDs@NaYF4 exhibits stable afterglow in different pH environments, suggesting its excellent stability. Finally, we demonstrated the application of CDs@NaYF4 in 3D printing, oily anti-counterfeiting patterns, and cell imaging. Our work can serve the controllable preparation of solution-phase RTP materials and their various applications.

Photoresponsive Blood-Derived Protein Hydrogels Packed with Bioactive Carbon Dots Modulate Mitochondrial Homeostasis and Reprogram Metabolism for Chronic Wound Healing in Diabetes

Autologous platelet concentrates (APC) represent a class of personalized regenerative materials for vascularized tissue regeneration. However, shortcomings including poor controllability of gel formation, lack of reactive oxygen species (ROS) scavenging ability, and deficient anti-inflammatory capacity restrict the tissue healing outcomes of APC. This study proposes an APC-based synergistic platform (CurCDs@iPRF-MA) for the treatment of chronic wounds in diabetes. Such a platform is composed of injectable platelet-rich fibrin (iPRF), gelatin methacryloyl (GelMA), and a carbogenic nanodrug from curcumin (CurCDs) that is injectable before the light-induced gel formation process, greatly facilitating the clinical applications of APC. Significantly, CurCDs@iPRF-MA can modulate the mitochondrial homeostasis under inflammatory conditions, activate the oxidative phosphorylation (OXPHOS) program, and regulate the diabetic microenvironment through metabolic reprogramming to achieve macrophage phenotype regulation and ROS elimination, as well as promote vascularization by releasing autologous growth factors, dramatically improving the healing efficacy of the chronic wounds in diabetes. This study offers a practical and effective approach to developing spatiotemporally controllable and multifunctional APC-based hydrogels for highly effective tissue regeneration.

Peroxidase-like Active Cu-MOFs Nanozymes for Colorimetric Detection of Total Antioxidant Capacity in Fruits and Vegetables

In this study, two types of Cu-MOFs (Cu-TCPP and CuO-TCPP) with a two-dimensional layered porous structure were prepared via in situ polymerization using Cu2+, CuO, and TCPP as raw materials. Both Cu-MOFs exhibited peroxidase-like activity, capable of catalyzing the oxidation of TMB by H2O2 to form oxTMB, resulting in an absorption peak at 652 nm and a color change from colorless to blue. Subsequently, the addition of AA can reduce oxTMB back to TMB, causing the color of the system to lighten or become colorless. Based on this principle, a simple and rapid colorimetric method for AA detection was established and successfully applied to the detection of TAC in fruits and vegetables. The results showed that Cu-TCPP and CuO-TCPP had a large linear range of ascorbic acid detection of 0.01-100 mM (Cu-TCPP) and 0.05-100 mM (CuO-TCPP). This study not only provides a novel method for preparing nanozymes with peroxidase-like activity, but also offers a simple approach for analyzing the TAC of food.

Amino-Acid-Engineered Bionanozyme Selectivity for Colorimetric Detection of Human Serum Albumin

Nanozymes are emerging nanomaterials owing to their superior stability and enzyme-mimicking catalytic functions. However, unlike natural enzymes with inherent amino-acid-based recognition motifs for target interactions, manipulating nanozyme selectivity toward specific targets remains a major challenge. In this study, we introduce the de novo strategy using the supramolecular assembly of l-tryptophan (l-Trp) as the recognition amino acid with copper (Cu) ions for creating a human serum albumin (HSA)-responsive bionanozyme. This amino-acid-engineered bionanozyme enables selective colorimetric detection of HSA, a critical urinary biomarker for kidney diseases, overcoming the challenge that HSA is neither a typical substrate nor an inhibitor for most nanozymes. Kinetic studies and competitive tests reveal that HSA subdomain IIIA binding to l-Trp sites limits the electron-transfer-induced structural changes of l-Trp-Cu chelate rings, resulting in noncompetitive inhibition. This inhibition effect is significantly stronger than that observed for canonical amino acids, common proteins, and urinary interference species. Colorimetric monitoring of bionanozyme activity enables sensitive HSA detection with a detection limit of 1.3 nM and a quantification range of 2 nM to 10 μM. This approach is exceptionally more sensitive and offers a broader detection range compared to conventional colorimetric and fluorescent methods, suitable for diagnostics across various clinical stages of disease. This innovative rational strategy to designing and manipulating selective nanozyme-target interactions not only addresses the limitations of nanozymes but also expands their precise applications in complex biological systems.

Crystal Facet Effect in Chiral PdPt3 Hollow Nanocages as Nanozymes for Use in Enantiomer Recognition

Understanding the crystal facet effect in chiral enantiomer recognition plays an important role in designing and fabricating chiral nanozymes for biosensing and biodetection applications. Herein, we design an ideal platform to study the crystal facet effect in chiral enantiomer recognition using cubic and icosahedral PdPt3 hollow nanocages (NCs) as peroxidase mimics via surface ligand decoration of l/d-cysteine (l/d-Cys). The two PdPt3 NCs have the same structure of surface ligand, particle size, wall thickness, surface area, and elemental composition, with the only difference of exposed crystal facets, i.e., {100} for cubic PdPt3 NC-l/d-Cys and {111} for icosahedral PdPt3 NC-l/d-Cys. The cubic PdPt3 {100} facet demonstrates 2.2-fold higher peroxidase-like catalytic activity than the icosahedral PdPt3 {111} facet, which also leads to the better enantiomer recognition performance of discerning 3,4-dihydroxy-l/d-phenylalanine. Our work provides the concept of crystal facet tuning for designing chiral nanozymes with high stereoselective properties.

Adhesive thermosensitive polydopamine hydrogel containing Mn3O4 anchored halloysite clay for treatment of ulcerative colitis

Ulcerative colitis (UC), a common inflammatory bowel disease, causes ulcers of the colon and rectum. One of the important reasons for intestinal lesions caused by UC is that immune cells produce large amounts of reactive oxygen species (ROS). Herein, we developed an adhesive thermosensitive polydopamine hydrogel containing Mn3O4 nanozyme anchored halloysite nanotubes (Mn3O4@HNTs@PDA) to remove ROS produced by immune cells and treatment of UC. Halloysite nanotubes (HNTs) were used as support for the synthesis of Mn3O4 nanoparticles (∼10 nm diameter), which decreased the nanozyme size and increased the catalysis activity. Mn3O4@HNTs can simultaneously remove H2O2 and ·OH through the mutual reaction conversion between SOD-like and CAT-like enzymes. The PDA coating enables Mn3O4@HNTs to adhere well to the damaged mucosa of the inflamed colon, as an artificial mucosal barrier inhibits local oxidative stress. In the dextran sulfate sodium (DSS)-induced UC mouse model, Mn3O4@HNTs@PDA hydrogel effectively transformed the local inflammatory microenvironment and restored intestinal barrier function by scavenging ROS through enzyme-like action, promoting the expression of intestinal mucosal junction proteins. Overall, this study provided a new dosing method to remove ROS by tissue adhesive hydrogel containing nanozyme modified clay mineral, which shows promising applications in clinic gastroenteritis treatment.

Atomic Artificial Enzyme for Acute and Chronic Pneumonia

Pneumonia involves complex immunological and pathological processes leading to pulmonary dysfunction, which can be life-threatening yet lacks effective specialized medications. Natural enzymes can be used as biological agents for the treatment of oxidative stress-related diseases, but limiting to catalytic and environmental stability as well as high cost. Herein, an artificial enzyme, gold nanoclusters (Au NCs) with excellent stability, bioactivity, and renal clearance can be used as the next-generation biological agents for acute lung injury (ALI) and allergic lung disease (ALD). The Au25 clusters can mimic catalase (CAT) and glutathione peroxidase (GPx), and the Km of Au24Er1 with H2O2 reaches 1.28 mM, about 22 times higher than natural CAT (≈28.8 mM). The clusters inhibit the oxidative stress in the mitochondria and promote the synthesis of adenosine triphosphate (ATP). The molecular mechanism shows that the TLR4/MyD88/NF-κB pathway and M1 macrophage-mediated inflammatory response are suppressed in ALI and the Th1/Th2 imbalance in ovalbumin (OVA)-induced ALD is rescued. Further, the clusters can notably improve lung function in both ALI and ALD models which paves the way for immunomodulation and intervention for lung injury and can be used as a substitute for natural enzymes and potential biopharmaceuticals in the treatment of various types of pneumonia.

Carbon Dot Nanozymes with Ferrous Ion-Chelating and Antioxidative Activity Inhibiting Ferroptosis to Alleviate Renal Ischemia-Reperfusion Injury

Renal ischemia-reperfusion (I/R) significantly contributes to acute kidney injury (AKI), causing substantial oxidative stress and metabolic disruptions. Ferroptosis, a Fe2+-dependent form of regulated cell death characterized by lipid peroxide accumulation, is the predominant cause of renal I/R injury (RIRI). Here, carbon dot (C-dot) nanozymes that inhibit ferroptosis by regulating Fe2⁺ levels and scavenging reactive oxygen species, offering a potential treatment for RIRI are reported. C-dots chelate Fe2⁺ via surface carbonyl, hydroxyl, and carboxyl groups to reduce free Fe2⁺ levels, suppress the Fenton reaction, and limit hydroxyl radical generation. Additionally, C-dots scavenge superoxide anions and hydroxyl radicals to restore redox balance. By targeting the kidneys, C-dots effectively reduce renal iron overload and lipid peroxidation to prevent ferroptotic cell death in the renal I/R male mice model. RNA sequencing (RNA-seq) analysis further confirms the crucial roles of C-dots in mitigating oxidative stress, preserving iron homeostasis, and downregulating acyl-CoA synthetase long-chain family member 4 (ACSL4) after I/R. This work emphasizes the perfect alignment between the multifunctional roles of C-dots and the conditions required for inhibiting ferroptosis and offers an innovative strategy to treat RIRI effectively.

AuI-incorporated metal-organic frameworks nanozymes for thioreduction and glutathione depletion-mediated efficient photoimmunotherapy

Tumor therapy has historically been a global research focus, with phototherapy garnered significant attention as a innovative treatment modality. However, the antioxidant defense system in the tumor microenvironment, characterized by excessive glutathione (GSH) and thiol-containing proteins, often limits the effectiveness of photodynamic therapy. In this study, we report the development of a new multifunctional integrated nanozyme with thioredoxin reductase-oxidase (TrxRox) and GSH-oxidase (GSHox)-like activities. This nanozyme, termed AuI-incorporated MOFs, was synthesized by embedding monovalent Au nanozymes into a light-sensitive metal-organic framework (MOFs) structure using an in-situ oxidation-reduction method. The intergrated AuI nanozyme exhibited inhibitory effects on TrxR and presented significant anti-tumor properties. Moreover, the integrated nanozyme also demonstrates peroxidase-like activity, catalyzing the decomposition of hydrogen peroxide (H2O2) into hydroxyl radicals (•OH). Additionally, this nanomedicine effectively depletes existing GSH and TrxR, thereby enhancing the efficacy of photodynamic and photothermal therapy. Notably, under light conditions, this nanozyme induces oxidative stress within cells, leading to apoptosis and necrosis of tumor cells. Of note, it triggers immunogenic cell death and activating antigen-presenting cells to convert cold tumors into hot tumors. Therefore, AuI-incorporated MOFs nanozyme demonstrates promising potential in photoimmunotherapy, offering new insights and strategies for tumor therapy.

Ratiometric Photoacoustic Imaging Probe for Self-Predicting Nanozyme Therapeutic Effects

Nanozymes with intrinsic enzyme-like properties have garnered significant attention in cancer treatment. However, effective methods to evaluate in situ the catalytic activity of nanozymes in living systems remain lacking. Herein, we pioneeringly present a novel probe (1-FCuSA) for self-reporting nanozyme catalytic activity, which integrates a diene electrochromic material (EM 1) and a copper single-atom nanozyme (FCuSA) with peroxidase (POD)-like activity. This system is designed to self-predict its catalytic activity through a ratiometric photoacoustic (PA) imaging signal. Initially, 1-FCuSA exhibits a low PA ratio (PA808/PA1064) between 808 and 1064 nm. Upon reaction with hydroxyl radicals (•OH) generated by the POD-like activity of FCuSA, the PA signal at 808 nm significantly increases, while the signal at 1064 nm remains stable. This results in an obvious increase in PA808/PA1064, enabling accurate monitoring of •OH production during nanozyme-catalyzed therapy. Thus, 1-FCuSA not only induces specific POD-like activity for in vivo tumor treatment but also provides real-time monitoring of catalytic efficiency through ratiometric PA imaging. This innovative approach may offer new insights into the early prediction of anticancer efficacy and guide the application of nanozymes in living systems.

Intervening with nanozymes in aging-related diseases: Strategies for restoring mitochondrial function

The decline in mitochondrial function has been identified as one of the central pathological mechanisms underlying a variety of aging-related diseases. Nanozymes are nanomaterials with intrinsic enzyme-like properties and are important alternatives to natural enzymes. As emerging biocatalysts, nanozymes exhibit significant potential in mimicking the activity of natural enzymes, enhancing mitochondrial function, and offering novel therapeutic strategies for aging-related conditions. This review provides an overview of various approaches to modulate the catalytic activity of nanozymes, considering factors such as particle size, shape, surface modifications, and constituent elements. It then examines the role of nanozymes in mitigating aging-related diseases by preserving mitochondrial health, with a particular focus on their ability to regulate three critical aspects: mitochondrial energy metabolism, quality control, and antioxidant capacity. By improving mitochondrial energy generation, supporting mitochondrial integrity, and eliminating excess reactive oxygen species (ROS), nanozymes offer new therapeutic possibilities for neurodegenerative diseases, bone-related disorders, and diabetes. Finally, this article discusses the major challenges faced in this field, including issues such as the scalability, biocompatibility, and targeting ability of nanozymes. It also emphasizes that future research should focus on enhancing clinical translation to ensure that nanozymes can play an effective role in practical therapeutic applications.

Spontaneous immobilization of single atom in Nb2CTx MXene as excellent nanozyme for detecting and preventing gastric mucosal injury

Early diagnosis and treatment of gastric mucosal injury is crucial to prevent further gastritis and even canceration. As an efficient biocatalyst, single-atom nanozyme (SAzyme) is proposed to be an ideal candidate for the construction of multifunctional platforms. Nevertheless, SAzyme still faces challenges in detecting and treating diseases due to the complexity of preparation methods, limitations of enzyme activity, and undesirable biocompatibility. Specifically, the Nb2CTx MXene with abundant Nb-deficit vacancy defects and high reductive capability can potentially be recognized as an effective support for stabilizing single atoms. Single-atom Pt-immobilized Nb2CTx nanosheet (SA Pt-Nb2CTx) possessing significant glutathione peroxidase (GPx)-like and superoxide dismutase (SOD)-like activities have been synthesized by a simple spontaneous reduction method. Based on the GPx-like activity of SA Pt-Nb2CTx, a simple Fe2+ fluorescence sensor is developed with a detection limit of 1.02 μM. Furthermore, the in vitro experiments reveal the excellent antioxidation capacity of this nanozyme, which effectively alleviates the inflammatory response. Importantly, the self-assembled SA Pt-Nb2CTx possesses a superior protective effect against ethanol-induced gastric mucosal damage, which is mainly related to the enhanced antioxidant and anti-inflammatory effects. Overall, engineered single-atom modified MXene as a multienzyme mimetic provides new insights for the manufacture of single-atom nanozyme and its application in protecting gastrointestinal health.

Nanozyme-Catalyzed Colorimetric Microfluidic Immunosensor for the Filtration Enrichment and Ultrasensitive Detection of Salmonella typhimurium in Food Samples

Rapid screening of foodborne pathogens is crucial to prevent food poisoning. In this study, we proposed a nanozyme-catalyzed colorimetric microfluidic immunosensor (Nano-CMI) for the filtration enrichment and ultrasensitive detection of Salmonella typhimurium in complex matrices. Gold-core porous platinum shell nanopompoms (Au@Pt nanopompoms) were synthesized with excellent peroxidase-like activity to oxidize 3,3',5,5'-tetramethylbenzidine with significant color change. The Au@Pt nanopompoms demonstrated a large reaction area, superior catalytic property, and good stability. The microfluidic chip used in the Nano-CMI was designed based on the size disparities among S. typhi, Au@Pt nanopompoms, and the pore sizes of filters I and II. Thus, a biosensor containing pretreatment, incubation, enrichment, and detection of four-in-one functions was established and performed under the drive of a medical plastic syringe. This biosensor can accomplish ultrasensitive detection of S. typhi with a limit of detection as low as 9 cfu/mL within 20 min, which makes it suitable for point-of-care testing. The proposed Nano-CMI also possessed high specificity and good repeatability (RSD < 2.1%) and can thus be applied directly to the analysis of real food samples, suggesting its great potential for practical application in the food safety field.

Carbon dot superoxide dismutase nanozyme enhances reactive oxygen species scavenging in diabetic skin wound repair

INTRODUCTION

The accumulation of reactive oxygen species (ROS) in diabetic wounds leads to inflammation and impaired neovascularization. Recent studies have indicated that carbon dot nanozymes (C-dots) exhibiting superoxide dismutase (SOD)-like activity can neutralize excessive ROS and mitigate diseases associated with oxidative stress.

OBJECTIVES

Our study was designed to evaluate the therapeutic impact of C-dots on the healing of diabetic wounds and to unravel the complex molecular mechanisms through which these nanozymes modulate oxidative stress and inflammatory responses within the wound microenvironment.

METHODS AND RESULTS

We synthesized C-dots from carbon fiber and confirmed their structure using transmission electron microscopy. The presence of carbon-carbon double bonds on the C-dots was verified with X-ray photoelectron spectroscopy. We assessed the scavenging capacity of C-dots for superoxide anion, hydroxyl radical, and nitric oxide radical using electron spin resonance spectroscopy. Their SOD-like activity and total antioxidant capacity were evaluated with commercial assay kits. In vitro experiments showed that C-dots effectively scavenged excessive ROS, protecting human keratinocytes, vascular endothelial cells, and fibroblasts from oxidative stress-induced damage. Concurrently, C-dots increased the migratory capacity of fibroblasts. In a streptozocin-induced diabetic mice model, C-dots application enhanced skin wound healing, evidenced by accelerated re-epithelialization and orderly collagen matrix assembly. Mechanistic investigations indicated that C-dots markedly suppressed ROS generation and diminished the levels of inflammatory cytokines in the wound environment. Additionally, C-dots induced an M2 polarization phenotype in macrophages and promoted neovascularization, indicating a transition from the inflammatory to the proliferative phase. Quantitative proteomic analysis was conducted to further clarify the underlying mechanisms of C-dots in ameliorating diabetic wounds.

CONCLUSION

C-dots represent a robust nanomaterial-based strategy for treating diabetic wounds, with the ability to accelerate healing by alleviating oxidative stress, mitigating harmful inflammatory responses, and fostering angiogenesis. This highlights their significant therapeutic potential in the field of biomedicine.

Surface moieties drive the superior protection of curcumin-derived carbon quantum dots against retinal ischemia-reperfusion injury

Despite the recognized neuroprotective benefits of curcumin, its clinical utility is constrained by poor bioavailability and high cytotoxicity at effective doses. This study evaluates the therapeutic potential of curcumin-derived carbon quantum dots (Cur-CQDs) for retinal protection against ischemia-reperfusion (IR) injury in rats. Cur-CQDs were synthesized via mild pyrolysis at varying temperatures and assessed for efficacy in rat retinal ganglion cells and a model of retinal IR injury. The Cur-CQDs, particularly those synthesized at 150 °C, displayed significant reductions in apoptosis in retinal tissues, as indicated by TUNEL assays, immunofluorescence localization of HIF-α, CD68, BCL-2, and Grp78, and Western blot analysis for HO-1, Grp78, CHOP, caspase 3, and Nrf2. These results suggest that Cur-CQDs not only enhance cell survival and reduce inflammation but also decrease oxidative and endoplasmic reticulum stress markers. Mechanistic insights reveal that Cur-CQDs modulate pathways involved in oxidative stress, apoptosis, and inflammation, specifically through the upregulation of BCL-2 and HO-1 and the downregulation of CHOP, caspase-3, and endoplasmic reticulum stress markers. The identification of cinnamic acid-, anisole-, guaiacol, and ferulic acid-like structures on Cur-CQDs' surfaces may contribute to their superior antioxidative and anti-inflammatory activities. Collectively, these findings position Cur-CQDs as a promising approach for treating retinal IR injuries, enhancing curcumin's bioavailability and therapeutic efficacy, and paving new pathways in ocular neuroprotection research and potential clinical applications.

Oxygen vacancy-enriched NiO nanozymes achieved via facile annealing in argon for detection of L-Cys

Nickel oxide (NiO) nanozymes, as an excellent oxidase mimic, have been widely used in fluorescence biological detection, water pollutant analysis, food safety and cell imaging. However, a great challenge in fully realising these applications is regulating their crystalline micro-/nano-structure and composites to achieve high enzyme activity and high specific surface area. Herein, we applied a very simple thermal annealing treatment to restructure the calcined precursor of NiO. Importantly, it was found that the oxygen vacancy (OV) concentration of the targeted NiO nanozyme significantly increased when the annealing atmosphere was argon rather than air. Moreover, the as-prepared novel NiO sample (NiO-OV) nanosheets achieved about 2-fold enhancement in their specific surface area. It is believed that a higher OV concentration and larger specific surface area increase enzyme activity by accelerating the electron transfer rate and improving catalytic interfaces. The significant improvement in the enzyme activity of NiO-OV was verified using the fluorescence "turn-on" experiment of Amplex Red (AR). Finally, using the NiO-OV/AR system, we constructed a highly sensitive enzyme sensor on L-Cys with a detection limit of 37.8 nM. The sensor also displayed excellent specificity for ten typical amino acid interferents.

ZnO-Cu/Mn nanozyme for rescuing the intestinal homeostasis in Salmonella-induced colitis

Salmonella is one of the most common foodborne pathogens, which can cause severe enteritis and intestinal microbiota imbalance. However, there are limited strategies currently available for preventing or treating Salmonella-induced colitis. Herein, we developed the Cu/Mn-co-doped ZnO tandem nanozyme (ZnO-CM) with pH-responsive multienzyme-mimicking activities via doping engineering for the treatment of Salmonella-induced colitis. Benefiting from the co-doping of Cu and Mn, ZnO-CM nanospheres exhibit remarkable peroxidase-like activity in acidic condition and superoxide dismutase- and catalase-like activities in neutral environment. Animal experiments show that ZnO-CM can efficiently inhibit bacterial growth, alleviate inflammation, and restore the intestinal barrier, resulting in good antibacterial and anti-inflammatory effects on Salmonella-induced colitis. Mechanistically, ZnO-CM functions through inhibiting the continuous accumulation of ROS, increasing the levels of tight junction proteins occludin and claudin-1, and decreasing the expression of pro-inflammatory cytokines IL-1β and IL-6 in intestine. This work not only presents an effective paradigm for Salmonella-induced colitis therapy, but also provides new sights into the prevention and treatment of other bacterial enteritis.

Molecularly Imprinted Polyaniline-Coated Cu-Zeolitic Imidazolate Framework Nanoparticles: Uricase-Mimicking "Polynanozyme" Catalyzing Uric Acid Oxidation

One of the drawbacks of nanozyme catalytic functions rests in their moderate catalytic activities due to the lack of effective binding sites concentrating the reaction substrate at the nanozyme catalytic interface. Methods to concentrate the substrates at the catalytic interface are essential to improving nanozyme functions. The present study addresses this goal by designing uric acid (UA) molecular-imprinted polyaniline (PAn)-coated Cu-zeolitic imidazolate framework (Cu-ZIF) nanoparticles as superior nanozymes, "polynanozymes", catalyzing the H2O2 oxidation of UA to allantoin (peroxidase activity) or the aerobic, uricase mimicking, oxidation of UA to allantoin (oxidase activity). While bare Cu-ZIF nanoparticles reveal only peroxidase activity and the nonimprinted PAn-coated Cu-ZIF nanoparticles reveal inhibited peroxidase activity, the molecular-imprinted PAn-coated Cu-ZIF nanoparticles reveal a 6.1-fold enhanced peroxidase activity, attributed to the concentration of the UA substrate at the catalytic nanoparticle interface. Moreover, the catalytic aerobic oxidation of UA to allantoin by the imprinted PAn-coated Cu-ZIF nanoparticles is lacking in the bare particles, demonstrating the evolved catalytic functions in the molecularly imprinted polynanozymes. Mechanistic characterization of the system reveals that within the UA molecular imprinting process of the PAn coating, Cu+ reactive units are generated within the Cu-ZIF nanoparticles, and these provide reactive sites for generating O2-• as an intermediate agent guiding the oxidase activities of the nanoparticles. The study highlights the practical utility of molecular-imprinted polynanozymes in catalytic pathways lacking in the bare nanozymes, thus broadening the scope of nanozyme systems.

Zinc Single-Atom Nanozyme As Carbonic Anhydrase Mimic for CO2 Capture and Conversion

Single-atom nanozymes (SANs) are a class of nanozymes with metal centers that mimic the structure of metalloenzymes. Herein, we report the synthesis of Zn-N-C SAN, which mimics the action of the natural carbonic anhydrase enzyme. The two-step annealing technique led to a metal content of more than 18 wt %. Since the metal centers act as active sites, this high metal loading resulted in superior catalytic activity. Zn-SAN showed a CO2 uptake of 2.3 mmol/g and a final conversion of CO2 to bicarbonate of more than 91%. CO2 was converted via a biomimetic process by allowing its adsorption by the catalyst, followed by the addition of the catalyst to HEPES buffer (pH = 8) to start the CO2 conversion into HCO3 -. Afterward, CaCl2 was added to form a white CaCO3 precipitate, which was then filtered, dried, and weighed. Active carbon and MCM-41 were used as controls under the same reaction conditions. According to the findings, the CO2 sequestration capacity was 42 mg of CaCO3/mg of Zn-SAN. Some amino acids (AAs) with binding affinity for Zn were able to suppress the enzymatic activity of Zn-SAN by blocking the active metal centers. This strategy was used for the detection of His, Cys, Glu, and Asp with detection limits of 0.011, 0.031, 0.029, and 0.062 μM, respectively, and hence was utilized for quantifying these AAs in commercial dietary supplements.

Atomically dispersed copper(I) on tungstosilicic acid for catalytic protection against cisplatin-induced hearing loss

The employment of platinum-based drugs for cancer chemotherapy, which might yield oxidative stress, is regarded as one main factor leading to hearing loss. The exact molecular mechanisms for cisplatin-induced hearing loss require further clarification, thus limiting the development of FDA-approved therapies. Herein, we mimicked the molecular structure of natural antioxidative enzymes to fabricate a four-oxygen-coordinating copper single-atom nanozyme (Cu SAN) exhibiting good superoxide dismutase and catalase activity, to alleviate the oxidative stress induced by platinum-based drugs. Notably, Cu SAN exhibited profound protective effects against cisplatin-induced hair cell damage with only 15 ng mL-1 of Cu species, successfully reversing cisplatin-induced hearing loss via oral administration. Due to its oxidation resistance, pretreatment with Cu SAN significantly improved cell viability and reduced ROS accumulation in cisplatin-triggered hair cell damage in HEI-OC1 cells and cochlear explants. Our results first demonstrated that cisplatin treatment induced cuproptosis in hair cells by modulating copper ion homeostasis. Further investigation revealed that Cu SAN nanozyme effectively alleviated hair cell cuproptosis by regulating FDX1 and reducing aggregated lipoacylated protein. This research underscores the promising potential of four-oxygen-coordinating Cu nanomaterials as a therapeutic approach to combat hearing loss, providing a new strategy for auditory protection.

Facile preparation of fluorescent carbon dots from water caltrop shells and their application in amikacin sensing

Amikacin (AMK) effectively treats infections from Gram-negative bacilli and penicillin-resistant Staphylococcus aureus. However, prolonged administration of AMK may result in adverse effects such as nausea, headache, ototoxicity, and hearing loss, necessitating a reliable detection method. Carbon dots (CDs), known for their excellent optical properties, are a promising fluorescent probe. This study developed cost-effective, eco-friendly WCS-CDs from water caltrop shells using a simple hydrothermal process for AMK detection and analysis. The WCS-CDs emitted at 380 nm when excited at 290 nm and demonstrated selective sensitivity to AMK, with fluorescence quenching linearly related to AMK concentration from 1.5 to 21.5 μg mL-1 (Y = 376.98 + 57.75X, R 2 = 0.992). This simple method allows for accurate AMK quantification in real samples, achieving recoveries of 95.58-105.63%.

Ultrasmall High-Entropy-Alloy Nanozyme Catalyzed In Vivo ROS and NO Scavenging for Anti-Inflammatory Therapy

High-entropy alloy (HEA) nanoparticles possess finely tunable and multifunctional catalytic activity due to their extremely diverse adsorption sites. Their unique properties enable HEA nanoparticles to mimic the complex interactions of the redox homeostasis system, which is composed of cascade and multiple enzymatic reactions. The application of HEAs in mimicking complex enzymatic systems remains relatively unexplored, despite the importance of regulating biological redox reactions. Here, it is reported that ultra-small (<10 nm in a diameter) HEA nanozymes consisting of five platinum-group metals with tunable morphologies from planar to dendritic structures are synthesized. The synthesized HEA nanozymes exhibited higher peroxidase-like activity compared to monometallic platinum-group nanoparticles. Additionally, HEA nanoparticles effectively mimicked RONS-regulation metabolism in cascade reactions involving superoxide dismutase and catalase, as well as in multiple reactions including HORAC and NO scavenging. As a result, the HEA nanozyme exhibited superior anti-inflammatory efficacy both in vitro and in vivo. The findings underscore the effectiveness of the high-entropy alloy structure in restoring in vivo enzymatic systems through intrinsic activity enhancements and cascade reaction mechanisms.

Ce12V6 Clusters with Multi-Enzymatic Activities for Sepsis Treatment

Artificial enzymes, especially nanozymes, have attracted wide attention due to their controlled catalytic activity, selectivity, and stability. The rising Cerium-based nanozymes exhibit unique SOD-like activity, and Vanadium-based nanozymes always hold excellent GPx-like activity. However, most inflammatory diseases involve polymerase biocatalytic processes that require multi-enzyme activities. The nanocomposite can fulfill multi-enzymatic activity simultaneously, but large nanoparticles (>10 nm) cannot be excreted rapidly, leading to biosafety challenges. Herein, atomically precise Ce12V6 clusters with a size of 2.19 nm are constructed. The Ce12V6 clusters show excellent glutathione peroxidase (GPx) -like activity with a significantly lower Michaelis-Menten constant (Km, 0.0125 mM versus 0.03 mM of natural counterpart) and good activities mimic superoxide dismutase (SOD) and peroxidase (POD). The Ce12V6 clusters exhibit the ability to scavenge the ROS including O2 ·- and H2O2 via the cascade reactions of multi-enzymatic activities. Further, the Ce12V6 clusters modulate the proinflammatory cytokines including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) and consequently rescue the multi-organ failure in the lipopolysaccharide (LPS)-induced sepsis mouse model. With excellent biocompatibility, the Ce12V6 clusters show promise in the treatment of sepsis.

Carbon-based nanozymes for cancer therapy and diagnosis: A review

Carbon-based nanozymes (CNs) have emerged as a significant innovation in targeted cancer therapy, demonstrating great potential for advancing cancer diagnosis and treatment. With exceptional catalytic properties, remarkable biocompatibility, and the ability to precisely target cancer cells, CNs provide a promising avenue for the development of novel oncological therapies. By functionalizing their surfaces with targeting ligands, such as antibodies or peptides, CNs can specifically recognize and bind to cancer cells. This targeted approach ensures that therapeutic agents are delivered directly to the tumor site, minimizing off-target effects, and reducing systemic toxicity. Additionally, the enzyme-like activities of CNs, when combined with conventional therapies such as chemotherapeutics, photothermal therapy, and photodynamic therapy, or other modalities can enhance therapeutic outcomes. Integrating CNs into clinical practice could significantly improve therapeutic efficacy, reduce probable side effects, enhance patient outcomes, and drive a shift towards more personalized cancer care. Besides, CNs can also be employed in biosensors and diagnostic nanomaterials, enabling rapid, selective, and highly accurate detection of specific biomarkers. Their versatile functionalities open new avenues for refining imaging techniques, ultimately contributing to early diagnosis and better clinical decision-making. This review consolidates recent studies exploring CNs in cancer targeting, highlighting both their diagnostic and therapeutic potential in oncology.