Advances in organometallic/organic nanozymes and their applications

Photothermal amplified multizyme activity for synergistic photothermal-catalytic tumor therapy

Nano-enzymatic catalytic therapy has been widely explored as a promising tumor therapeutic method with specific responsiveness to the tumor microenvironment (TME). However, the inherent lower and simplex catalytic efficiency impairs their anti-tumor efficacy. Therefore, developing novel nanozymes with relatively high and multiple catalytic characteristics, simultaneously enhancing the enzyme-like activity of nanozymes using the proper method, photothermal promoted catalytic property, is a reliable way. In this paper, we report a manganese oxide/nitrogen-doped carbon composite nanoparticles (MnO-N/C NPs) with multi-enzyme mimetic activity and photothermal conversional effect. The peroxidase (POD)-like/oxidase (OXD)-like/catalase (CAT)-like activity of MnO-N/C nanozymes was accelerated upon exposure to an 808 nm NIR laser. In vitro and in vivo results proved that the MnO-N/C NPs shown excellent magnetic resonance imaging (MRI) guided synergistic photothermal-enhanced catalytic treatment and photothermal therapy of liver cancer. The photothermal enhanced multi-enzyme activity maximizes the efficacy of catalytic and photothermal therapy while reducing harm to healthy cells, thereby offering valuable insights for the development of next-generation photothermal nanozymes to enhance tumor therapy.

Ru-Ph Nanozyme-Based Hydrogels for Tumor Chemodynamic Therapy by Enhancing Enzyme Catalytic Efficiency Through Multiple Pathways

The discovery of nanozymes has opened new possibilities for tumor therapy. However, their reliance on the tumor microenvironment and limited catalytic efficiency hinder broader applications. In this study, ruthenium-phenanthroline nanoparticles (Ru-Phs) are synthesized by combining ruthenium with phenanthroline and subsequently coloaded with the proton pump inhibitor (PPI) pantoprazole into sodium alginate (ALG) to form a Ru-Phs-PPI-ALG hydrogel for in situ tumor therapy. This hydrogel demonstrates excellent chemodynamic properties, forming a gel within tumor tissues and gradually releasing Ru-Phs, which generates highly toxic reactive oxygen species (ROS) via peroxidase-like (POD-like) activity. The inclusion of PPI reduced the intracellular pH of tumor cells, accelerating the Fenton reaction and ROS accumulation. Additionally, the high photothermal conversion efficiency of Ru-Phs-PPI-ALG enables heat generation under near-infrared (NIR) irradiation, which not only disrupts tumor cell structures but also further enhances the POD-like catalytic activity of Ru-Phs. The hydrogel effectively killed 4T1 cells in vitro, and transcriptomic analysis confirms its potent chemodynamic efficacy. In vivo experiments demonstrate significant tumor ablation and excellent biocompatibility. This multipathway strategy to increase enzyme activity and improve chemodynamic effects provides a promising approach for advancing nanozyme applications in tumor therapy.

Supramolecular engineering of cellulose-polyaniline composites using CuTA for superior energy storage applications

Cellulose, the most abundant biomass, is highly appreciated for its robustness, biodegradability, and renewability, garnering significant interest for innovative applications in sustainable functional materials. Composites of cellulose and polyaniline (PANI) are particularly promising for flexible supercapacitors because of their ease of processing, excellent electrical conductivity, and high theoretical specific capacitance. However, challenges persist due to the tendency of PANI to agglomerate and the weak interfacial interactions between PANI and cellulose fibers (CFs). Herein, copper tannin (CuTA), a metal-phenolic supramolecular complex, is utilized to strengthen the interface between the cellulose and PANI, while also modulating the nanostructure of the PANI layer to create high-performance cellulose-based flexible electrodes. Consequently, after incorporating CuTA, the composite electrodes demonstrated a significantly high capacitance of 5147 mF/cm2. Furthermore, the mechanism underlying the superior energy density of supercapacitors is investigated. This strategy provides a novel method for promoting the development of green, economical, and high-performing cellulose-based supercapacitors.

A novel and facile oxygen-activated time-temperature indicator with wide temperature monitoring range and good stability based on the laccase-like nanozyme

BACKGROUND

Time-Temperature Indicator (TTI) is an indicator device for real-time monitoring of the thermal history of the product. Due to the enzymatic reactions are affected by both time and temperature, enzymatic TTIs have been extensively studied and developed in recent years. However, enzymatic TTIs contain biologically active molecules (enzymes), which require high storage and use conditions. Most of them are designed to mix the system species together and irreversible reaction is undertaken. Nanozymes are the synthetic nanomaterials with similar biocatalytic functions as natural enzymes, which have extensive applications in analytical chemistry, biosensing, and environmental protection due to their facile synthesis, low cost, high stability and durability.

RESULTS

This work proposed to replace the natural laccase to laccase-like nanozyme, designed a novel and facile O2-activated time-temperature indicator for the first time. Nanozyme had excellent thermal and storage stability, which could maintain fabulous catalytic activity in the wide temperature range of 10-80 °C and after a long-term storage. Based on the O2 was required to participate in the oxidation of laccase-catalyzed substrates, a squeeze-type O2-activated TTI was designed by controlling O2 in the TTI system. The TTI was activated through extruding the O2-coated airbag ruptured and producing an irreversible color reaction. Combined with a smartphone to extract the chromaticity for portable visual real-time monitoring. Five sets of TTIs were prepared based on the concentration of nanozyme, and the activation energies (Ea) ranging from 28.45 to 72.85 kJ mol-1, which were able to be fitted to products with Ea ranging from 3.45 to 97.8 kJ mol-1 and the monitoring-time of less than 7 days.

SIGNIFICANCE

Compared to the traditional enzymatic TTI, the TTIs designed based on nanozyme has the advantages of controlled activation, wider temperature monitor range and good stability. Providing a new approach to the development of real-time monitoring of smart devices.

Doughnut-shaped bimetallic Cu-Zn-MOF with peroxidase-like activity for colorimetric detection of glucose and antibacterial applications

Metal-organic frameworks (MOFs), especially bimetallic MOFs, have attracted widespread attention for simulating the structure and function of natural enzymes. In this study, different morphologies of bimetallic Cu-Zn-MOF with different peroxidase (POD)-like activities were prepared by simply controlling the molar ratio of Cu2+ and Zn2+. Among them, the doughnut-shaped Cu9-Zn1-MOF exhibited the largest POD-like activity. Cu9-Zn1-MOF was combined with glucose oxidase to construct a sensitive and selective glucose colorimetric biosensor with a linear detection range of 10-300 μM and a detection limit of 7.1 μm. Furthermore, Cu9-Zn1-MOF can efficiently convert hydrogen peroxide (H2O2) into hydroxyl radicals that effectively kill both gram-negative and gram-positive bacteria at low H2O2 level. The results of this study may promote the synthesis of bimetallic MOFs and broaden their applications in the biomedical field.

Transition-metal-based nanozymes for biosensing and catalytic tumor therapy

Nanozymes, as an emerging class of enzyme mimics, have attracted much attention due to their adjustable catalytic activity, low cost, easy modification, and good stability. Researchers have made great efforts in developing and applying high-performance nanozymes. Recently, transition-metal-based nanozymes have been designed and widely developed because they possess unique photoelectric properties and high enzyme-like catalytic activities. To highlight these achievements and help researchers to understand the research status of transition-metal-based nanozymes, the development of transition-metal-based nanozymes from material characteristics to biological applications is summarized. Herein, we focus on introducing six categories of transition-metal-based nanozymes and highlight their progress in biomarker sensing and catalytic therapy for tumors. We hope that this review can guide the further development of transition-metal-based nanozymes and promote their practical applications in cancer diagnosis and treatment.

Coencapsulating TMB Probes and Bimetallic MOF Nanozymes in a Hydrogel Patch for Fabricating Reusable Visual VC Sensors

As a typical chromogenic probe, 3,3',5,5'-tetramethylbenzidine (TMB) has been widely applied in the field of visual detection due to its low toxicity and highly sensitive response. Due to the hydrophobic nature of TMB, encapsulating it into a hydrogel, which serves as an ideal matrix for wearable sensors, presents significant challenges that complicate the fabrication of visual wearable devices. Herein, the TMB probe and bimetallic MOF nanozymes are coencapsulated in a hydrogel patch for the fabrication of reusable visual sensors. Hydrophobic TMB is oxidized to hydrophilic ox-TMB by a bimetallic MOF (CuFe-MOF), allowing its diffusion into a hydrophilic agarose hydrogel patch, where it is reduced back to TMB. This process allows the coimmobilization and coencapsulation of CuFe-MOF and TMB within the hydrogel patch. Leveraging the color change between TMB and ox-TMB, as a proof-of-concept application, a reusable visual "On-Off-On" sensor is simply constructed and successfully applied to detect vitamin C in human sweat. Color changes can be quickly read by the naked eye or by smart devices without the need for external equipment. Meanwhile, based on the reversible conversion relationship between TMB and ox-TMB, a reusable sensor construction strategy is proposed. This approach not only facilitates the use of a TMB probe in hydrogel applications but also offers inspiration for the development of point-of-care testing equipment, demonstrating significant application potential.

Two-dimensional black phosphorus/platinum catalase-like nanozyme-based Fenton reaction-mediated dual-mode immunoassays for the detection of enrofloxacin

Hydrogen peroxide-based Fenton reaction can effectively degrade many small-molecule fluorescent dyes, leading to notable alterations in fluorescence signals. Additionally, the two-dimensional black phosphorus/platinum nanocomposite (BP/Pt) demonstrates exceptional catalase (CAT) characteristics. Based on these, a colorimetric-fluorescence dual-mode signal output pattern based on BP/Pt-Fenton reaction-rhodamine B tandem reaction system is reported. The physical adsorption property of the BP/Pt nanozymes was utilized to couple with antibodies, thus constructing a novel dual-mode nanozyme-based immuno-sensing assay (NISA). By using the migratory antibiotic enrofloxacin (ENR) as the target, the NISA provided highly sensitive detection with the detection limits of 0.058 ng/mL for colorimetric-mode and 0.025 ng/mL for fluorescence-mode and achieved accurate quantitative detection in environmental water and crucian carp samples. This work provides an innovative design for monitoring antibiotics in the environment and broadens the idea for the application of nanozymes and Fenton systems in immunosensing assays.

Fast Reaction of the Prussian Blue Based Nanozyme "Artificial Peroxidase" with the Substrates: Pre-Steady-State Kinetic Approach

This letter introduces the pre-steady-state kinetic approach, which is traditional for evaluation of elementary constants in molecular (enzyme) catalysis, for nanozymes. Apparently, the most active peroxidase-mimicking nanozyme based on catalytically synthesized Prussian Blue nanoparticles has been chosen. The elementary constants (k1) for the nanozymes' reduction by an electron-donor substrate (being the fastest stage according to steady-state kinetic data) have been determined by means of stopped-flow spectroscopy. These constants have been found to be dependent on both the size of the nanozyme and the reducing substrate redox potential. For the smallest nanozymes (32 nm in diameter), log(k1) linearly decays with an increase of the substrate redox potential (cotangent value ≈125 mV). On the contrary, for the largest nanozymes with a diameter above 150 nm, k1 is almost independent of it. Moreover, for the substrate with the lowest redox potential (K4[Fe(CN)6]), the rate constant under discussion (k1) is almost independent of the nanozymes' size. Perhaps, the rate of the intrananozyme electron transfer causing bleaching becomes comparative or even lower than that of the nanoparticle interaction with the fastest substrate. Anyway, the elementary constant of nanozyme reduction with potassium ferrocyanide (k1) reaches the value of 1 × 1010 M-1 s-1, which is 3-4 orders of magnitude faster than for enzymes peroxidases. The obtained results obviously demonstrate that the pre-steady-state kinetic approach is able to discover novel advantages of nanozymes from both fundamental and practical points of view.

Ultrasmall polyvinylpyrrolidone-modified iridium nanoparticles with antioxidant and anti-inflammatory activity for acute pancreatitis alleviation

Acute pancreatitis (AP) is a common and serious acute inflammatory disease with high severity rate and mortality. Inflammation and oxidative stress play an extremely important role in the development of AP disease. Polyvinylpyrrolidone-modified iridium nanoparticles (IrNP-PVP) have multienzyme mimetic activity, and the aim of this article is to discuss the therapeutic alleviative effects of the ultrasmall nanozymes IrNP-PVP on AP through their antioxidant and anti-inflammatory effects. IrNP-PVP were proved to inhibit inflammation and scavenge reactive oxygen species (ROS) at the cellular level. The synthetic IrNP-PVP exhibit remarkable antioxidant and anti-inflammatory activities in the prevention and treatment of AP mice by establishing murine AP model, which can reduce the oxidative stress and inflammatory response. The results of this article indicated that the ultrasmall nanozymes IrNP-PVP effectively alleviate AP via scavenging ROS as well as suppressing inflammation both in vivo and in vitro, which might provide enormous promise for the AP management.

Research progress of chilled meat freshness detection based on nanozyme sensing systems

It is important to develop rapid, accurate, and portable technologies for detecting the freshness of chilled meat to meet the current demands of meat industry. This report introduces freshness indicators for monitoring the freshness changes of chilled meat, and systematically analyzes the current status of existing detection technologies which focus on the feasibility of using nanozyme for meat freshness sensing detection. Furthermore, it examines the limitations and foresees the future development trends of utilizing current nanozyme sensing systems in evaluating chilled meat freshness. Harmful chemicals are produced by food spoilage degradation, including biogenic amines, volatile amines, hydrogen sulfide, and xanthine, which have become new freshness indicators to evaluate the freshness of chilled meat. The recognition mechanisms are clarified based on the special chemical reaction with nanozyme or directly inducting the enzyme-like catalytic activity of nanozyme.

Multifunctional Metal-Organic Frameworks Driven Three-Dimensional Folded Paper-Based Microfluidic Analysis Device for Chlorpyrifos Detection

Chlorpyrifos (CPF) residues in food pose a serious threat to ecosystems and human health. Herein, we propose a three-dimensional folded paper-based microfluidic analysis device (3D-μPAD) based on multifunctional metal-organic frameworks, which can achieve rapid quantitative detection of CPF by fluorescence-colorimetric dual-mode readout. Upconversion nanomaterials were first coupled with a bimetal organic framework possessing peroxidase activity to create a fluorescence-quenched nanoprobe. After that, the 3D-μPAD was finished by loading the nanoprobe onto the paper-based detection zone and spraying it with a color-developing solution. With CPF present, the fluorescence intensity of the detection zone gradually recovers, the color changes from colorless to blue. This showed a good linear relationship with the concentration of CPF, and the limits of detection were 0.028 (fluorescence) and 0.043 (colorimetric) ng/mL, respectively. Moreover, the 3D-μPAD was well applied in detecting real samples with no significant difference compared with the high-performance liquid chromatography method. We believe it has huge potential for application in the on-site detection of food hazardous substance residues.

Overview on the Development of Electrochemical Immunosensors by the Signal Amplification of Enzyme- or Nanozyme-Based Catalysis Plus Redox Cycling

Enzyme-linked electrochemical immunosensors have attracted considerable attention for the sensitive and selective detection of various targets in clinical diagnosis, food quality control, and environmental analysis. In order to improve the performances of conventional immunoassays, significant efforts have been made to couple enzyme-linked or nanozyme-based catalysis and redox cycling for signal amplification. The current review summarizes the recent advances in the development of enzyme- or nanozyme-based electrochemical immunosensors with redox cycling for signal amplification. The special features of redox cycling reactions and their synergistic functions in signal amplification are discussed. Additionally, the current challenges and future directions of enzyme- or nanozyme-based electrochemical immunosensors with redox cycling are addressed.

Multifunctional N, Fe-doped carbon dots with peroxidase-like activity for the determination of H2O2 and ascorbic acid and cell protection against oxidation

Multifunctional N, Fe-doped carbon dots (N, Fe-CDs) were synthesized by the one-step hydrothermal method using ferric ammonium citrate and dicyandiamide as raw materials. The N, Fe-CDs exhibited peroxidase-like (POD) activity by catalyzing the oxidization of 3,3',5,5'-tetramethylbenzidine (TMB) to the green oxidation state ox-TMB in the presence of hydrogen peroxide (H2O2). Subsequently, based on the POD activity of N, Fe-CDs, an efficient and sensitive colorimetric method for the detection of H2O2 and ascorbic acid (AA) was established with a limit of detection of 0.40 µM and 2.05 µM. The proposed detection method has been successfully applied to detect AA in fruit juice, vitamin C tablets, and human serum samples and has exhibited excellent application prospects in biotechnology and food fields. Furthermore, N, Fe-CDs also showed a protective effect on the cell damage caused by H2O2 and could be used as an antioxidant agent.

Immobilization of a broad host range phage on the peroxidase-like Fe-MOF for colorimetric determination of multiple Salmonella enterica strains in food

A broad host range phage-based nanozyme (Fe-MOF@SalmpYZU47) was prepared for colorimetric detection of multiple Salmonella enterica strains. The isolation of a broad host range phage (SalmpYZU47) capable of infecting multiple S. enterica strains was achieved. Then, it was directly immobilized onto the Fe-MOF to prepare Fe-MOF@SalmpYZU47, exhibiting peroxidase-like activity. The peroxidase-like activity can be specifically inhibited by multiple S. enterica strains, benefiting from the broad host range capture ability of Fe-MOF@SalmpYZU47. Based on it, a colorimetric detection approach was developed for S. enterica in the range from 1.0 × 102 to 1.0 × 108 CFU mL-1, achieving a low limit of detection (LOD) of 11 CFU mL-1. The Fe-MOF@SalmpYZU47 was utilized for detecting S. enterica in authentic food samples, achieving recoveries ranging from 91.88 to 105.34%. Hence, our proposed broad host range phage-based nanozyme exhibits significant potential for application in the colorimetric detection of pathogenic bacteria.

A ratiometric fluorescence platform based on WS2 QDs/CoOOH nanosheet system for α-glucosidase activity detection

In this study, we have constructed a ratiometric fluorescence sensor for sensitive sensing of α-glucosidase activity based on WS2 QDs/ CoOOH nanosheet system. In this system, as an oxidase-imimicking nanomaterial, CoOOH nanosheet could convert o-phenylenediamine into 2,3-diaminophenazine (DAP), which had a high fluorescence emission at 575 nm. The DAP subsequently could quench the fluorescence of WS2 QDs via the inner filter effect (IFE). L-Ascorbic acid-2-O-α-D-glucopyranose could be hydrolyzed by α-glucosidase to yield ascorbic acid. CoOOH nanosheet can be converted to Co2+ ions by ascorbic acid, leading to the fluorescence decrease of DAP and the fluorescence recovery of WS2 QDs. Therefore, a novel ratio fluorescence sensing strategy was established for α-glucosidase detection based on WS2 QDs/CoOOH nanosheet system. This WS2 QDs/CoOOH nanosheet system has a low detection limit of 0.009 U/mL for α-Glu assay. The proposed strategy succeeded in detecting α-Glu in human serum samples.

The Interaction of Amines with Gold Nanoparticles

Understanding the interactions between amines and the surface of gold nanoparticles is important because of their role in the stabilization of the nanosystems, in the formation of the protein corona, and in the preparation of semisynthetic nanozymes. By using fluorescence spectroscopy, electrochemistry, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and molecular simulation, a detailed picture of these interactions is obtained. Herein, it is shown that amines interact with surface Au(0) atoms of the nanoparticles with their lone electron pair with a strength linearly correlating with their basicity corrected for steric hindrance. The kinetics of binding depends on the position of the gold atoms (flat surfaces or edges) while the mode of binding involves a single Au(0) with nitrogen sitting on top of it. A small fraction of surface Au(I) atoms, still present, is reduced by the amines yielding a much stronger Au(0)-RN.+ (RN. , after the loss of a proton) interaction. In this case, the mode of binding involves two Au(0) atoms with a bridging nitrogen placed between them. Stable Au nanoparticles, as those required for robust semisynthetic nanozymes preparation, are better obtained when the protein is involved (at least in part) in the reduction of the gold ions.

Nickel-Based Metal-Organic Frameworks Promote Diabetic Wound Healing via Scavenging Reactive Oxygen Species and Enhancing Angiogenesis

Chronic diabetic wounds remain a worldwide challenge for both the clinic and research. Given the vicious circle of oxidative stress and inflammatory response as well as the impaired angiogenesis of the diabetic wound tissues, the wound healing process is disturbed and poorly responds to the current treatments. In this work, a nickel-based metal-organic framework (MOF, Ni-HHTP) with excellent antioxidant activity and proangiogenic function is developed to accelerate the healing process of chronic diabetic wounds. The Ni-HHTP can mimic the enzymatic catalytic activities of antioxidant enzymes to eliminate multi-types of reactive species through electron transfer reactions, which protects cells from oxidative stress-related damage. Moreover, this Ni-based MOF can promote cell migration and angiogenesis by activating transforming growth factor-β1 (TGF-β1) in vitro and reprogram macrophages to the anti-inflammatory phenotype. Importantly, Ni-HHTP effectively promotes the healing process of diabetic wounds by suppressing the inflammatory response and enhancing angiogenesis in vivo. This study reports a versatile and promising MOF-based nanozyme for diabetic wound healing, which may be extended in combination with other wound dressings to enhance the management of diabetic or non-healing wounds.

A dual-functional single-atom Fe nanozyme-based sensitive colorimetric sensor for tannins quantification in brandy

Traditional methods of tannins detection suffer from complex pretreatment, long detection time, and limited sensitivity. Modern techniques like liquid chromatography require expertise, involve tedious result processing, and lack effective data visualization. Therefore, there is a need for an alternative detection method that simplifies pretreatment and detection steps, reduces analysis time, and provides visualized results. In this study, a novel colorimetric sensor based on single-atom Fe nanozyme (Fe@CN-20) was developed for tannins detection. Fe@CN-20 exhibited laccase-like and oxidase-like activities, enabling simultaneous oxidation of tannins and a substrate called TMB. Tannins competed with TMB, allowing quantification of tannins content. The Fe@CN-20/TMB system provided a detection range of 5-100 mg/L tannic acid, with a detection limit of 0.13 mg/L (S/N = 3). Analysis time was approximately 30 min. The platform successfully quantified tannins in brandy, showing less than 5% deviation compared to the standard method. The sensor was simple, sensitive, rapid, and provided strong visualization.

Selective sensing of catechol based on a fluorescent nanozyme with catechol oxidase activity

Nanozymes, an unusual category of nanomaterials possessing enzymatic properties, and have generated considerable interest regarding their application feasibilities on several important fronts. In the present work, an innovative sensing device for catechol was established ground on a fluorescent nanozyme (Cu-BDC-NH2) that exhibited catechol oxidase activity. The fluorescent nanozyme combines both functions of catechol recognition and response signal output, and can realize the sensing of catechol without the addition of other chromogenic agents. In the existence of Cu-BDC-NH2, catechol can be oxidized efficiently to produce quinones or polymers with strong electron absorption capacity, which immediately results in efficient fluorescence quenching of Cu-BDC-NH2. However, other common phenolic compounds, such as phenol, the other two diphenols (hydroquinone and resorcinol), phloroglucinol, and chlorophenol, do not result in efficient fluorescence quenching of Cu-BDC-NH2. The method shows a nice linear relationship between catechol concentration prep the fluorescence intensity of Cu-BDC-NH2 in the scope of 0-10 μM, with a detection limit of 0.997 μM. The detection of catechol in actual water samples has also achieved the satisfactory consequences, which provides a new strategy for the convenient and selective detection of catechol.

Metal-organic framework-modulated Fe3O4 composite au nanoparticles for antibacterial wound healing via synergistic peroxidase-like nanozymatic catalysis

Bacterial wound infections are a serious threat due to the emergence of antibiotic resistance. Herein, we report an innovative hybrid nanozyme independent of antibiotics for antimicrobial wound healing. The hybrid nanozymes are fabricated from ultra-small Au NPs via in-situ growth on metal-organic framework (MOF)-stabilised Fe3O4 NPs (Fe3O4@MOF@Au NPs, FMA NPs). The fabricated hybrid nanozymes displayed synergistic peroxidase (POD)-like activities. It showed a remarkable level of hydroxyl radicals (·OH) in the presence of a low dose of H2O2 (0.97 mM). Further, the hybrid FMA nanozymes exhibited excellent biocompatibility and favourable antibacterial effects against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. The animal experiments indicated that the hybrid nanozymes promoted wound repair with adequate biosafety. Thus, the well-designed hybrid nanozymes represent a potential strategy for healing bacterial wound infections, without any toxic side effects, suggesting possible applications in antimicrobial therapy.

The mechanism of nanozyme activity of ZnO-Co3O4-v: Oxygen vacancy dynamic change and bilayer electron transfer pathway for wound healing and virtual reality revealing

Since the catalyst's surface was the major active location, the inner structure's contribution to catalytic activity was typically overlooked. Here, ZnO-Co3O4-v nanozymes with several surfaces and bulk oxygen vacancies were created. The O atoms of H2O2 moved inward to preferentially fill the oxygen vacancies in the interior and form new "lattice oxygen" by the X-ray photoelectron spectroscopy depth analysis and X-ray absorption fine structure. The internal Co2+ continually transferred electrons to the surface for a continuous catalytic reaction, which generated a significant amount of reactive oxygen species. Inner and outer double-layer electron cycles accompanied this process. A three-dimensional model of ZnO-Co3O4-v was constructed using virtual reality interactive modelling technology to illustrate nanozyme catalysis. Moreover, the bactericidal rate of ZnO-Co3O4-v for Methionine-resistant Staphylococcus aureus and Multiple drug resistant Escherichia coli was as high as 99%. ZnO-Co3O4-v was biocompatible and might be utilized to heal wounds following Methionine-resistant Staphylococcus aureus infection. This work offered a new idea for nanozymes to replace of conventional antibacterial medications.

DNA-Encoded Bidirectional Regulation of the Peroxidase Activity of Pt Nanozymes for Bioanalysis

Rational regulation of nanozyme activity can promote biochemical sensing by expanding sensing strategies and improving sensing performance, but the design of effective regulatory strategies remains a challenge. Herein, a rapid DNA-encoded strategy was developed for the efficient regulation of Pt nanozyme activity. Interestingly, we found that the catalytic activity of Pt nanozymes was sequence-dependent, and its peroxidase activity was significantly enhanced only in the presence of T-rich sequences. Thus, different DNA sequences realized bidirectional regulation of Pt nanozyme peroxidase activity. Furthermore, the DNA-encoded strategy can effectively enhance the stability of Pt nanozymes at high temperatures, freezing, and long-term storage. Meanwhile, a series of studies demonstrated that the presence of DNA influenced the reduction degree of H₂PtCl₆ precursors, which in turn affected the peroxidase activity of Pt nanozymes. As a proof of application, the sensor array based on the Pt nanozyme system showed superior performance in the accurate discrimination of antioxidants. This study obtained the regulation rules of DNA on Pt nanozymes, which provided theoretical guidance for the development of new sensing platforms and new ideas for the regulation of other nanozyme activities.

Review: Synthesis of metal organic framework-based composites for application as immunosensors in food safety

Ensuring food safety continues to be one of the major global challenges. For effective food safety monitoring, fast, sensitive, portable, and efficient food safety detection strategies must be devised. Metal organic frameworks (MOFs) are porous crystalline materials that have attracted attention for use in high-performance sensors for food safety detection owing to their advantages such as high porosity, large specific surface area, adjustable structure, and easy surface functional modification. Immunoassay strategies based on antigen-antibody specific binding are one of the important means for accurate and rapid detection of trace contaminants in food. Emerging MOFs and their composites with excellent properties are being synthesized, providing new ideas for immunoassays. This article summarizes the synthesis strategies of MOFs and MOF-based composites and their applications in the immunoassays of food contaminants. The challenges and prospects of the preparation and immunoassay applications of MOF-based composites are also presented. The findings of this study will contribute to the development and application of novel MOF-based composites with excellent properties and provide insights into advanced and efficient strategies for developing immunoassays.

Iron-Coordinated L-Lysine-Based Nanozymes with High Peroxidase-like Activity for Sensitive Hydrogen Peroxide and Glucose Detection

It is crucial to develop sensitive and accurate sensing strategies to detect H₂O₂ and glucose in biological systems. Herein, biocompatible iron-coordinated L-lysine-based hydrogen peroxide (H₂O₂)-mimetic enzymes (Lys-Fe-NPs) were prepared by precipitation polymerization in aqueous solution. The coordinated Fe²⁺ ion acted as centers of peroxidase-like enzymes of Lys-Fe-NPs, and the catalytic activity was evaluated via the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H₂O₂. Therefore, a sensitive colorimetric detection sensor for H₂O₂ was constructed with a linear range of 1 to 200 μM and a detection limit of 0.51 μM. The same method could also be applied to highly sensitive and selective detection of glucose, with a linear range of 0.5 to 150 μM and a detection limit of 0.32 μM. In addition, an agarose-based hydrogel biosensor colorimetric was successfully implemented for visual assessment and quantitative detection of glucose. The design provided a novel platform for constructing stable and nonprotein enzyme mimics with lysine and showed great potential applications in biorelevant assays.

Tuning the enzyme-like activity of peptide-nanoparticle conjugates with amino acid sequences

We constructed peptide-nanoparticle conjugates (AuNP@CDs-Azo-peptide) by self-assembly of cyclodextrin capped gold nanoparticles (AuNP@CDs) and azobenzene terminated peptide (Azo-peptide) through host-guest interactions. AuNP@CDs-Azo-peptide shows hydrolase-like activity, which is tuned by amino acid sequences.

Single-atom nanozymes Co-N-C as an electrochemical sensor for detection of bioactive molecules

A properly designed sensing interface is crucial for the accurate and sensitive detection of biologically active molecules. Single-atom nanozymes from transition metal and nitrogen-doped carbon materials (M-N-C) have caught attention owing to their large surface area and strong bionic enzyme activity. Herein, a three-dimensional layered electrochemical electrode consisting of a Co-N-C nanoenzyme embedded in a reduced graphene oxide aerogel was prepared for the detection of hydrogen peroxide (H₂O₂), dopamine (DA) and uric acid (UA). Due to its unique three-dimensional layered structure, rGA has excellent electrical conductivity and high material loading and is used to enhance the electrocatalytic performance of Co-N-C. The combination of single-atom nanozymes and electrochemical detection shows unique advantages in catalytic activity and selectivity. The limit of detection and detection range are 0.74 μM and 3-2991 μM respectively for H₂O_2. Furthermore, it has been successfully implemented for the in-situ detection of H₂O₂ in living cells. In addition, their simultaneous detection is also realized by the sensors for DA and UA. And it can accurately capture the signal of UA and DA in the urine. Meanwhile, the electrode displays satisfactory stability and repeatability. Therefore, this paper provides a new detection strategy for a variety of bioactive molecules, showing great potential in cell biology, pathophysiology and diagnostics.

Ultra-small polydopamine nanomedicine-enabled antioxidation against senescence

Senescence is a cellular response characterized by cells irreversibly stopping dividing and entering a state of permanent growth arrest. One of the underlying pathophysiological causes of senescence is the oxidative stress-induced damage, indicating that eliminating the reactive oxygen and nitrogen species (RONS) may be beneficial to prevent and/or alleviate senescence. Herein, we developed ultra-small polydopamine nanoparticles (UPDA NPs) with superoxide dismutase (SOD)/catalase (CAT) enzyme-mimic activities, featuring broad-spectrum RONS-scavenging capability for inducing cytoprotective effects against RONS-mediated damage. The engineered UPDA NPs can restore senescence-related renal function, tissue homeostasis, fur density, and motor ability in mice, potentially associated with the regulation of multiple genes involved in lipid metabolism, mitochondrial function, energy homeostasis, telomerase activity, neuroprotection, and inflammatory responses. Importantly, the dietary UPDA NPs can enhance the antioxidant capacity, improve the climbing ability, and prolong the lifespan of Drosophila. Notably, UPDA NPs possess excellent biocompatibility stemming from the ultra-small size, ensuring quick clearance out of the body. These findings reveal that UPDA NPs can delay aging through reducing oxidative stress and provide a paradigm and practical strategy for treating senescence and senescence-related diseases.

Nanomaterials-Functionalized Hydrogels for the Treatment of Cutaneous Wounds

Hydrogels have been utilized extensively in the field of cutaneous wound treatment. The introduction of nanomaterials (NMs), which are a big category of materials with diverse functionalities, can endow the hydrogels with additional and multiple functions to meet the demand for a comprehensive performance in wound dressings. Therefore, NMs-functionalized hydrogels (NMFHs) as wound dressings have drawn intensive attention recently. Herein, an overview of reports about NMFHs for the treatment of cutaneous wounds in the past five years is provided. Firstly, fabrication strategies, which are mainly divided into physical embedding and chemical synthesis of the NMFHs, are summarized and illustrated. Then, functions of the NMFHs brought by the NMs are reviewed, including hemostasis, antimicrobial activity, conductivity, regulation of reactive oxygen species (ROS) level, and stimulus responsiveness (pH responsiveness, photo-responsiveness, and magnetic responsiveness). Finally, current challenges and future perspectives in this field are discussed with the hope of inspiring additional ideas.

Zeolitic imidazolate frameworks as light-responsive oxidase-like mimics for the determination of adenosine triphosphate and discrimination of phenolic pollutants

In this study, 3,3',5,5'-tetramethylbenzidine (TMB) was selected as a chromogenic substrate to evaluate the light-responsive oxidase-like activity of different zeolitic imidazolate frameworks (ZIFs). The synthesized ZIFs were systematically characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. Several main operational parameters, including ZIFs and TMB concentrations, pH value, radiation time, and working current, in the reaction process were optimized. The kinetic measurement results show that ZIF-90 exhibits higher affinity to the substrate than horseradish peroxidase. Furthermore, given that adenosine triphosphate (ATP) can specifically combine with Zn²⁺ binding site and destroy the structure of ZIF-90, a specific and sensitive colorimetric method was established for the quantitative detection of ATP within the range 10 - 240 μM. In addition, on the basis that phenolic pollutants can impact the reaction kinetics diversely on different ZIFs, a sensor array was constructed and successfully applied to differentiate five phenolic pollutants in lake water samples. This work is expected to shed light on the establishment of ZIF-based light-responsive oxidase-like nanozymes for the highly selective colorimetric detection and sensor array.

Plasmonic Nanozymes: Leveraging Localized Surface Plasmon Resonance to Boost the Enzyme-Mimicking Activity of Nanomaterials

Nanozymes, a type of nanomaterials that function similarly to natural enzymes, receive extensive attention in biomedical fields. However, the widespread applications of nanozymes are greatly plagued by their unsatisfactory enzyme-mimicking activity. Localized surface plasmon resonance (LSPR), a nanoscale physical phenomenon described as the collective oscillation of surface free electrons in plasmonic nanoparticles under light irradiation, offers a robust universal paradigm to boost the catalytic performance of nanozymes. Plasmonic nanozymes (PNzymes) with elevated enzyme-mimicking activity by leveraging LSPR, emerge and provide unprecedented opportunities for biocatalysis. In this review, the physical mechanisms behind PNzymes are thoroughly revealed including near-field enhancement, hot carriers, and the photothermal effect. The rational design and applications of PNzymes in biosensing, cancer therapy, and bacterial infections elimination are systematically introduced. Current challenges and further perspectives of PNzymes are also summarized and discussed to stimulate their clinical translation. It is hoped that this review can attract more researchers to further advance the promising field of PNzymes and open up a new avenue for optimizing the enzyme-mimicking activity of nanozymes to create superior nanocatalysts for biomedical applications.

Aptamer-Modified Au Nanoparticles: Functional Nanozyme Bioreactors for Cascaded Catalysis and Catalysts for Chemodynamic Treatment of Cancer Cells

Polyadenine-stabilized Au nanoparticles (pA-AuNPs) reveal dual nanozyme catalytic activities toward the H₂O₂-mediated oxidation of dopamine to aminochrome and toward the aerobic oxidation of glucose to gluconic acid and H₂O₂. The conjugation of a dopamine-binding aptamer (DBA) to the pA-AuNPs yields aptananozyme structures catalyzing simultaneously the H₂O₂-mediated oxidation of dopamine to aminochrome through the aerobic oxidation of glucose. A set of aptananozymes consisting of DBA conjugated through the 5'- or 3'-end directly or spacer bridges to pA-AuNPs were synthesized. The set of aptananozymes revealed enhanced catalytic activities toward the H₂O₂-catalyzed oxidation of dopamine to dopachrome, as compared to the separated pA-AuNPs and DBA constituents, and structure-function relationships within the series of aptananozymes were demonstrated. The enhanced catalytic function of the aptananozymes was attributed to the concentration of the dopamine at the catalytic interfaces by means of aptamer-dopamine complexes. The dual catalytic activities of aptananozymes were further applied to design bioreactors catalyzing the effective aerobic oxidation of dopamine in the presence of glucose. Mechanistic studies demonstrated that the aptananozymes generate reactive oxygen species. Accordingly, the AS1411 aptamer, recognizing the nucleolin receptor associated with cancer cells, was conjugated to the pA-AuNPs, yielding a nanozyme for the chemodynamic treatment of cancer cells. The AS1411 aptamer targets the aptananozyme to the cancer cells and facilitates the selective permeation of the nanozyme into the cells. Selective cytotoxicity toward MDA-MB-231 breast cancer cells (ca. 70% cell death) as compared to MCF-10A epithelial cells (ca. 2% cell death) is demonstrated.

Dual-mode colorimetric-photothermal sensing platform of acetylcholinesterase activity based on the peroxidase-like activity of Fe-N-C nanozyme

Sensors based on colorimetry, fluorescence, and electrochemistry have been widely employed to detect acetylcholinesterase and its inhibitors, however, there are only a minority of strategies for AChE detection based on photothermal method. This work reports a versatile dual-mode colorimetric and photothermal biosensing platform for acetylcholinesterase (AChE) detection and its inhibitor (paraoxon-ethyl, a model of AChE inhibitors) monitor based on Fe-N-C/H₂O₂/3,3',5,5'-tetramethylbenzidine (TMB) system. The Fe-N-C with abundant active Fe-Nx sites shows outstanding peroxidase-mimicking activity and can be used to promote the generation of •OH by H₂O₂ to oxidize TMB. However, the introduction of mercapto molecules tending to coordinate with metal atoms result in the block of action site in Fe-N-C, thereby decrease its peroxidase-mimetic activity. The designed biosensor principle is based on the block of active sites of Fe-N-C by thiocholine (TCh, one kind of mercapto molecules) that can be produced by acetylthiocholine (ATCh) in the presence of AChE. Under optimum conditions, the limit of detection (LOD) for AChE activity is 1.9 mU mL^-1 (colorimetric) and 2.2 mU mL^-1 (photothermal), while for paraoxon-ethyl is 0.012 μg mL^-1 (colorimetric) and 0.013 μg mL^-1 (photothermal), respectively. The assay we proposed not only can be designed to monitor AChE detection and its inhibitors, but also can be easily extended for the detection of other biomolecules relate to the generation or consumption of H₂O₂.

Bimetallic Metal-Organic Framework Fe/Co-MIL-88(NH2) Exhibiting High Peroxidase-like Activity and Its Application in Detection of Extracellular Vesicles

Metal-organic frameworks (MOFs) have many attractive features, including tunable composition, rigid structure, controllable pore size, and large specific surface area, and thus are highly applicable in molecular analysis. Depending on the MOF structure, a high number of unsaturated metal sites can be exposed to catalyze chemical reactions. In the present work, we report that using both Co(II) and Fe(III) to prepare the MIL-88(NH₂) MOF, we can produce the bimetallic MOF that can catalyze the conversion of 3,3',5,5″-tetramethylbenzidine (TMB) to a color product through a reaction with H₂O₂ at a higher reaction rate than the monometallic Fe-MIL-88(NH₂). The Michaelis constants (K_m) of the catalytic reaction for TMB and H₂O₂ are 3-5 times smaller, and the catalytic constants (k_cat) are 5-10 times higher than those of the horseradish peroxidase (HRP), supporting ultrahigh peroxidase-like activity. These values are also much more superior to those of the HRP-mimicking MOFs reported previously. Interestingly, the bimetallic MOF can be coupled with glucose oxidase (GOx) to trigger the cascade enzymatic reaction for highly sensitive detection of extracellular vesicles (EVs), a family of important biomarkers. Through conjugation to the aptamer that recognizes the marker protein on EV surface, the MOF can help isolate the EVs from biological matrices, which are subsequently labeled by GOx via antibody recognition. The cascade enzymatic reaction between MOF and GOx enables the detection of EVs at a concentration as low as 7.8 × 10⁴ particles/mL. The assay can be applied to monitor EV secretion by cultured cells and also can successfully detect the different EV quantities in the sera samples collected from cancer patients and healthy controls. Overall, we prove that the bimetallic Fe/Co-MIL-88(NH₂) MOF, with its high peroxidase activity and high biocompatibility, is a valuable tool deployable in clinical assays to facilitate disease diagnosis and prognosis.

Au3+ -Functionalized UiO-67 Metal-Organic Framework Nanoparticles: O2•- and •OH Generating Nanozymes and Their Antibacterial Functions

The synthesis and characterization of Au³⁺ -modified UiO-67 metal-organic framework nanoparticles, Au³⁺ -NMOFs, are described. The Au³⁺ -NMOFs reveal dual oxidase-like and peroxidase-like activities and act as an active catalyst for the catalyzed generation of O₂^•- under aerobic conditions or •OH in the presence of H₂ O₂ . The two reactive oxygen species (ROS) agents O₂^•- and •OH are cooperatively formed by Au³⁺ -NMOFs under aerobic conditions, and in the presence of H₂ O_2. The Au³⁺ -NMOFs are applied as an effective catalyst for the generation ROS agents for antibacterial and wound healing applications. Effective antibacterial cell death and inhibition of cell proliferation of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacterial colonies are demonstrated in the presence of the Au³⁺ -NMOFs. In addition, in vivo experiments demonstrate effective wound healing of mice wounds infected by S. aureus, treated by the Au³⁺ -NMOFs.

AIEgen-Based Bionic Nanozymes for the Interventional Photodynamic Therapy-Based Treatment of Orthotopic Colon Cancer

Relative to traditional photosensitizer (PS) agents, those that exhibit aggregation-induced emission (AIE) properties offer key advantages in the context of photodynamic therapy (PDT). At present, PDT efficacy is markedly constrained by the hypoxic microenvironment within tumors and the limited depth to which lasers can penetrate in a therapeutic context. Herein, we developed platelet-mimicking MnO2 nanozyme/AIEgen composites (PMD) for use in the interventional PDT treatment of hypoxic tumors. The resultant biomimetic nanoparticles (NPs) exhibited excellent stability and were able to efficiently target tumors. Moreover, they were able to generate O2 within the tumor microenvironment owing to their catalase-like activity. Notably, through an interventional approach in which an optical fiber was introduced into the abdominal cavity of mice harboring orthotopic colon tumors, good PDT efficacy was achieved. We thus propose that a novel strategy consisting of a combination of an AIEgen-based bionic nanozyme and a biomimetic cell membrane coating represents an ideal therapeutic platform for targeted antitumor PDT. This study is the first to have combined interventional therapy and AIEgen-based PDT, thereby overcoming the limited light penetration that typically constrains the therapeutic efficacy of this technique, highlighting a promising new AIEgen-based PDT treatment strategy.

Biodegradable MoSe2-polyvinylpyrrolidone nanoparticles with multi-enzyme activity for ameliorating acute pancreatitis

Exogenous antioxidant materials mimicking endogenous antioxidant systems are commonly used for the treatment of oxidative stress-induced injuries. Thus, artificial enzymes have emerged as promising candidates for balancing and treating the dysregulation of redox homeostasis in vivo. Herein, a one-pot hydrothermal strategy for the facile preparation of MoSe₂-polyvinylpyrrolidone (PVP) nanoparticles (NPs) is reported. The synthesized NPs were biodegradable due to their exposure to oxygen and exhibited high stability. Moreover, they effectively mimicked various naturally occurring enzymes (including catalase, superoxide dismutase, peroxidase, and glutathione peroxidase) and scavenged free radicals, such as 3-ethylbenzothiazoline-6-sulfonic acid, ·OH, ·O²⁻, and 1,1-diphenyl-2-picrylhydrazyl radical. Further apoptosis detection studies revealed that MoSe₂-PVP NPs significantly increased the cell survival probability in H₂O₂ in a concentration-dependent manner. The cytoprotective effect of MoSe₂-PVP NPs was explored for an animal model of acute pancreatitis, which confirmed its remarkable therapeutic efficacy. Owing to the biodegradable and biocompatible nature of MoSe₂-PVP NPs, the findings of this work can stimulate the development of other artificial nanoenzymes for antioxidant therapies.

Reversible down-regulation and up-regulation of catalytic activity of poly(N-isopropylacrylamide)-anchored gold nanoparticles

Regulating catalytic activity plays an important role in further optimizing and developing multifunctional catalysts with high selectivity and high activity. Reversible dual regulation of catalytic activity has always been a challenging task. Here, we prepared poly(N-isopropylacrylamide)-anchored gold nanoparticles (AuNP@CDs-Azo-PNIPAM) through host-guest interaction of cyclodextrin capped gold nanoparticles (AuNP@CDs) and azobenzene-terminated poly(N-isopropylacrylamide) (Azo-PNIPAM). Azo-PNIPAM as thermal and light responsive ligand allows reversible dual regulation of catalytic activity. When the temperature is higher than the lowest critical solution temperature, the PNIPAM chain shrinks rapidly, increasing the steric hindrance around AuNPs and reducing the catalytic activity. Under ultraviolet light irradiation,cis-azobenzene disassembles from cyclodextrin and the number of surface active sites of AuNPs increases, which improves the catalytic activity. The reaction rate of UV irradiation is almost 1.3 times that of visible light irradiation. This work provides a simple and effective strategy for the construction of reversible catalysts.

A two-dimensional thin Co-MOF nanosheet as a nanozyme with high oxidase-like activity for GSH detection

A two-dimensional thin Co-MOF (ZIF-67) nanosheet with high oxidase-like activity was applied for sensitive visual GSH detection.

A ratiometric electrochemical biosensor for glycated albumin detection based on enhanced nanozyme catalysis of cuprous oxide-modified reduced graphene oxide nanocomposites

Nanozymes have enzyme-like characteristics and nanozyme-based electrochemical sensors have been widely studied for biomarker detection. In this work, cuprous oxide-modified reduced graphene oxide (Cu₂O-rGO) nanozyme was prepared by simultaneous reduction of copper chloride and graphene oxide. This Cu₂O-rGO nanozyme displayed an outstanding electrocatalytic activity to glucose oxidation and was used as the modified material of a glassy carbon electrode to fabricate an electrochemical ratiometric biosensor for glycated albumin (GA) detection. In this ratiometric biosensor, methylene blue-labeled DNA tripods (MB-tDNA) were adsorbed on the Cu₂O-rGO/GCE surface to form a bioinspired electrode (MB-tDNA/Cu₂O-rGO/GCE), in which the catalytic sites of Cu₂O-rGO were covered by MB-tDNA. In the presence of target GA, GA could be identified by the aptamer sequence contained in MB-tDNA, and a MB-tDNA/GA complex was formed and released into the solution, so the reduced current of MB-tDNA was decreased. Simultaneously, the oxidized current of the outer added glucose was increased since more catalytic sites of Cu₂O-rGO nanozyme on the substrate electrode surface were exposed. The ratio of the peak currents of glucose oxidation and methylene blue reduction (I_Glu/I_MB) was used to monitor the GA level and ultimately improve the accuracy of the method. The electrochemical sensor showed a low detection limit of 0.007 μg mL^-1 and a wide linear range from 0.02 to 1500 μg mL^-1. The proposed sensor was also successfully used to measure the GA expression level in the blood serum of a diabetic mouse model.

Enzyme (Single and Multiple) and Nanozyme Biosensors: Recent Developments and Their Novel Applications in the Water-Food-Health Nexus

The use of sensors in critical areas for human development such as water, food, and health has increased in recent decades. When the sensor uses biological recognition, it is known as a biosensor. Nowadays, the development of biosensors has been increased due to the need for reliable, fast, and sensitive techniques for the detection of multiple analytes. In recent years, with the advancement in nanotechnology within biocatalysis, enzyme-based biosensors have been emerging as reliable, sensitive, and selectively tools. A wide variety of enzyme biosensors has been developed by detecting multiple analytes. In this way, together with technological advances in areas such as biotechnology and materials sciences, different modalities of biosensors have been developed, such as bi-enzymatic biosensors and nanozyme biosensors. Furthermore, the use of more than one enzyme within the same detection system leads to bi-enzymatic biosensors or multi-enzyme sensors. The development and synthesis of new materials with enzyme-like properties have been growing, giving rise to nanozymes, considered a promising tool in the biosensor field due to their multiple advantages. In this review, general views and a comparison describing the advantages and disadvantages of each enzyme-based biosensor modality, their possible trends and the principal reported applications will be presented.

A metastasis suppressor Pt-dendrimer nanozyme for the alleviation of glioblastoma

Nanozymes are nanostructure-based materials which mimic the enzymatic characteristics of natural enzymes. Biological applications of nanozymes have been highlighted in basic research, industry, and translational medicine as a new cutting-edge tool. In this work, and for the first time, we disclose a tumor alleviation property of a nanozyme that is made up of amine-terminated sixth-generation polyamidoamine dendrimers with encapsulated tiny platinum nanoparticles. We systematically conducted the synthesis and characterization of the dendrimer-encapsulated Pt nanoparticles (denoted Pt-dendrimer) and confirmed their enzymatic function (hydrogen peroxide (H2O2) decomposition) within various cell lines (normal, cancerous), including glioblastoma (GBM) cells. By understanding the effects of the Pt-dendrimer at the gene level, especially related to cancer cell metastasis, we have thoroughly demonstrated its ability for tumor alleviation and suppressing GBM migration, invasion, and adhesion. The present findings show great promise for the application of the nanozyme for use in GBM-related basic research as well as at clinical sites.

Superoxide dismutase nanozymes: an emerging star for anti-oxidation

Superoxide dismutases (SODs) are a group of metalloenzymes that catalyze the dismutation of superoxide radicals (O2˙-) into hydrogen peroxide (H2O2) and oxygen (O2). As the first line of defense against reactive oxygen species (ROS)-mediated damage, SODs are expected to play an important role in the treatment of oxidative stress-related diseases. However, the clinical applications of SODs have been severely limited by their structural instability and high cost. Compared with natural enzymes, nanozymes, nanomaterials with enzyme-like activity, are more stable, and economical, can be easily modified and their activities can be adjusted. Due to their excellent characteristics, nanozymes have attracted widespread attention in recent years and are expected to become effective substitutes for natural enzymes in many application fields. Importantly, some nanozymes with SOD-like activity have been developed and proved to have a mitigating effect on diseases caused by oxidative stress. These studies on SOD-like nanozymes provide a feasible strategy for breaking through the dilemma of SOD clinical applications. However, at present, the specific catalytic mechanism of SOD-like nanozymes is still unclear, and many important issues need to be resolved. Although there are many comprehensive reviews to introduce the overall situation of the nanozyme field, the research on SOD-like nanozymes still lacks a systematic review. From the structure and mechanism of natural SOD enzymes to the structure and regulation of SOD-like nanozymes, and then to the measurement and application of nanozymes, this review systematically summarizes the recent progress in SOD-like nanozymes. The existing shortcomings and possible future research hotspots in the development of SOD-like nanozymes are summarized and prospected. We hope that this review would provide ideas and inspirations for further research on the catalytic mechanism and rational design of SOD-like nanozymes.

An enzyme cascade sensor with resistance to the inherent intermediate product by logic-controlled peroxidase mimic catalysis

Enzyme cascade sensors usually could not discriminate between the target and intermediate product. Herein, based on "AND" logic-controlled activation of the glucose oxidase-copper peroxide sensing system, enzyme cascade detection for glucose with resistance to inherently existing intermediate product H₂O₂ was reported for the first time, which may provide a novel way for facilitating enzyme cascade sensing.