Enzyme-like Activity Research Articles

Composite nanofibrous dressing loaded with Prussian blue and heparin for anti-inflammation therapy and diabetic wound healing

Diabetic ulcer is a severe complication of diabetes that can lead to amputation due to the overproduction of pro-inflammatory factors and reactive oxygen species (ROS). In this study, a composite nanofibrous dressing was developed by combining Prussian blue nanocrystals (PBNCs) and heparin sodium (Hep) through electrospinning, electrospraying, and chemical deposition. The nanofibrous dressing (PPBDH) was designed to take advantage of the excellent pro-inflammatory factor-adsorbing capability of Hep and the ROS-scavenging capabilities of PBNCs, resulting in synergistic treatment. It is worth noting that the nanozymes were firmly anchored to the fiber surfaces through slight polymer swelling caused by the solvent during electrospinning, thereby guaranteeing the preservation of the enzyme-like activity levels of PBNCs. The PPBDH dressing was found to be effective in reducing intracellular ROS levels, protecting cells from ROS-induced apoptosis, and capturing excessive pro-inflammatory factors, including chemoattractant protein-1 (MCP-1) and interleukin-1β (IL-1β). Furthermore, a chronic wound healing evaluation conducted in vivo demonstrated that the PPBDH dressing was able to effectively alleviate the inflammatory response and accelerate wound healing. This research presents an innovative approach to fabricate nanozyme hybrid nanofibrous dressings, which have great potential in accelerating the healing of chronic and refractory wounds with uncontrolled inflammation.

Aurozyme: A Revolutionary Nanozyme in Colitis, Switching Peroxidase-Like to Catalase-Like Activity.

A therapeutic strategy that could address colitis of multiple etiologies while restoring the dysbiosis of gut microbiota is attractive. Here, Aurozyme, a novel nanomedicine comprised of gold nanoparticles (AuNPs) and glycyrrhizin (GL) with a glycol chitosan coating layer, as a promising approach for colitis, is demonstrated. The unique feature of Aurozyme is the conversion of harmful peroxidase-like activity of AuNPs to beneficial catalase-like activity due to the amine-rich environment provided by the glycol chitosan. This conversion process enables Aurozyme to oxidize the hydroxyl radicals derived from AuNP, producing water and oxygen molecules. In fact, Aurozyme effectively scavenges reactive oxygen/reactive nitrogen species (ROS/RNS) and damage-associated molecular patterns (DAMPs), which can attenuate the M1 polarization of macrophage. It exhibits prolonged adhesion to the lesion site, promoting sustained anti-inflammatory effects and restoring intestinal function in colitis-challenged mice. Additionally, it increases the abundance and diversity of beneficial probiotics, which are essential for maintaining microbial homeostasis in the gut. The work highlights the transformative potential of nanozymes for the comprehensive treatment of inflammatory disease and represents an innovative switching technology of enzyme-like activity by Aurozyme.

PH-responsive dual-enzyme mimics based on hollow metal organic framework-derivatives β-Co(OH)2 for multiple colorimetric assays.

Ahollow metal organic framework derivative β-Co(OH)2has been prepared, which possesses oxidase and peroxidase-like activities. Oxidase-like activity is derived from the generation of free radicals, and peroxidase-like activity is related to the electron transfer process. Unlike other nanozymes with dual enzyme-like activities, β-Co(OH)2 possesses pH-responsive enzyme-like activities, among which the β-Co(OH)2 exhibits superior oxidase and peroxidase-like activities under pH of 4 and 6, respectively, which could avoid mutual interference between multiple enzymes. Based on the phenomenon that enzyme-like activities of β-Co(OH)2 can catalyze colorless TMB to generate blue oxidized TMB (oxTMB) with absorption peak at 652 nm, the sensors integrating total antioxidant capacity and H2O2 quantification were developed. The oxidase-like activity-based colorimetric system has a sensitive response to ascorbic acid, Trolox, and gallic acid, in which the limit of detection for those antioxidant substances was 0.54 μM, 1.26 μM, and 14.34 μM, respectively. The sensors based on peroxidase-like activity hadlow limit of detection of 1.42 μM for H2O2 and alinear range of 5-1000 μM. Theproposed method can be well applied to the detection of the total antioxidant capacity of kiwi, Vc tables, orange and tea extract with high accuracy, and H2O2 determination in milk and glucose detection in beverages with satisfactory recovery (within 97-106%).

Fe Doping Enhances the Peroxidase-Like Activity of CuO for Ascorbic Acid Sensing

Although significant advances have been witnessed in the application of nanozymes in recent years, exploring new strategies to enhance the enzyme-like activity of nanozymes is of urgent importance. Herein, we investigate the feasibility of accelerating the peroxidase-like reaction rate of CuO nanostructures through Fe doping. The coprecipitation method was used to synthesize Fe-doped CuO (Fe-CuO) nanozymes, and the results indicate that the diversified valence of Fe benefits the redox reaction driven by CuO-based nanozymes. With the improved peroxidase-like activity, the Fe-CuO nanozyme enables the significant chromogenic oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB), facilitating the construction of a visual sensing platform for the sensitive and selective determination of ascorbic acid. Under optimal conditions, the absorbance at 652 nm decreases linearly with the concentration of ascorbic acid in the range of 5–50 μM, with a limit of detection as low as 4.66 μM. This work exemplifies the activity enhancement for peroxidase-mimicking nanozymes with a metal-doping strategy and provides a broad prospect for the design of more high-performance nanozymes for biosensing applications.

Bimetallic FeMn-N nanoparticles as nanocatalyst with dual enzyme-mimic activities for simultaneous colorimetric detection and degradation of hydroquinone

The transition element based N-doped carbon nanoparticles (NPs) with high catalytic activity and more active centers are regards as nanozymes with great potential for colorimetric detection and environmental degradation. Here, three-dimensional (3D) hierarchically porous of manganese-amplified Fe-N-doped carbon (Fe/Mn-N-C) catalysts with more Fe/Mn-N4 and C-N active groups was synthesized via pyrolysis of manganese(II) acetyllacetonate/ferrocene@ZIF-8 nanocomposites. Owing to its excellent peroxidase-like (POD-like) and superoxide (SOD) mimicking properties, the Fe/Mn-N-C nanozymes were selected to rapid and accurate colorimetric detection of hydroquinone (HQ), and the detection limit was determined as 0.21 μM in range of 0–100 μM. In addition, the rapid degradation of HQ via hydroxyl radical (•OH) and superoxide anion (O2•-) generated between Fe/Mn-N-C nanozymes and H2O2, and the degradation efficiency reached to over 92% under the optimum reaction conditions (pH 4.0, 100 mM H2O2). The reaction mechanisms were systematically explored. The manganese-amplified Fe-N-C single atom nanozyme with excellent enzyme-like activity and chemical stability will propose a feasible way for accurate detection and removal of pollutants in actual production.

Simple and highly sensitive electrochemical detection of Listeria monocytogenes based on aptamer-regulated Pt nanoparticles/hollow carbon spheres nanozyme activity

Listeria monocytogenes (LM) is one of the deadliest and most hazardous pathogens, posing extremely serious harm to the human health, hence developing simple and effective method for its highly sensitive detection is very important. In this work, by preparing Pt nanoparticles/hollow carbon spheres (Pt/HCNs) nanohybrid as nanozyme, a simple and highly sensitive nanozyme-based electrochemical sensor was developed for the first time to detect LM based on aptamer (Apt)-regulated Pt/HCNs nanozyme activity. The as-prepared Pt/HCNs nanozyme can catalyze the oxidation of o-phenylenediamine to generate electroactive 2,3-diaminophenazinc (DAP) which offers an obvious reduction peak current. However, once bound to LM-Apt to form Apt/Pt/HCNs, the related enzyme-like activity of Pt/HCNs is inhibited remarkably and the reduction current of DAP nearly disappear owing to the covering of the active sites. Interestingly, in the presence of LM, the nanozyme activity can be recovered through the specific recognition of Apt towards LM. After optimizing various conditions, the designed Apt-regulated nanozyme-based electrochemical sensor shows excellent sensing performances for LM. Meanwhile, the designed sensors exhibits superior selectivity, specificity, reproducibility, stability and real applications. This work offers a simple and novel strategy for the effective and highly sensitive determination of various pathogens via altering simply the specific Apt.

Alkali-Etched Imprinted Mn-Based Prussian Blue Analogues with Superior Oxidase-Mimetic Activity and Precise Recognition for Tetracycline Colorimetric Sensing.

As a typical antibiotic pollutant, tetracycline (TC) is producing increasing threats to the ecosystem and human health, and exploring convenient means for monitoring of TC is needed. Here, we proposed alkali-etched imprinted Mn-based Prussian blue analogues featuring superior oxidase-mimetic activity and precise recognition for the colorimetric sensing of TC. Simply etching Mn-based Prussian blue analogues (Mn-PBAs) with NaOH could expose the sites and surfaces to significantly improve their catalytic activity. Density functional theory calculations were employed to screen the molecularly imprinted polymer (MIP) layer for target identification. Consequently, the designed Mn-PBANaOH@MIP possessed the rich channels for substrates to get in touch with the active Mn-PBANaOH core, showing an excellent catalytic capacity to trigger the chromogenic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) without the use of H2O2. If TC was introduced, it would be recognized selectively by the MIP shell and masked the channels for TMB access, resulting in the obstruction of the chromogenic reaction. According to this mechanism, selective optical detection of TC was achieved, and performance stability, reusability, and reliability as well as practicability were also verified, promising potential for TC monitoring in complex matrices. Our work not only presents an effective way to enhance the enzyme-like activity of Prussian blue analogues but also provides a facile approach for TC sensing. Additionally, the work will inspire the exploration of molecularly imprinted nanozymes for various applications.

Catalytic Bioswitch of Platinum Nanozymes: Mechanistic Insights of Reactive Oxygen Species Scavenging in the Neurovascular Unit.

Oxidative stress is known to be the cause of several neurovascular diseases, including neurodegenerative disorders, since the increase of reactive oxygen species (ROS) levels can lead to cellular damage, blood-brain barrier leaking, and inflammatory pathways. Herein, we demonstrate the therapeutic potential of 5 nm platinum nanoparticles (PtNPs) to effectively scavenge ROS in different cellular models of the neurovascular unit. We investigated the mechanism underlying the PtNP biological activities, analyzing the influence of the evolving biological environment during particle trafficking and disclosing a key role of the protein corona, which elicited an effective switch-off of the PtNP catalytic properties, promoting their selective in situ activity. Upon cellular internalization, the lysosomal environment switches on and boosts the enzyme-like activity of the PtNPs, acting as an intracellular "catalytic microreactor" exerting strong antioxidant functionalities. Significant ROS scavenging was observed in the neurovascular cellular models, with an interesting protective mechanism of the Pt-nanozymes along lysosomal-mitochondrial axes.

Reactive Template-Engaged Synthesis of NiSx/MoS2 Nanosheets Decorated on Hollow and Porous Carbon Microtubes with Optimal Electronic Modulation toward High-Performance Enzyme-like Performance

As a promising cost-effective nanozyme, MoS2 nanosheets (NSs) have been considered as a good candidate for the enzyme-like catalysis. However, their catalytic activity is still restricted by the insufficient active sites and poor conductivity, and thus, the comprehensive performances are still unsatisfactory. To address these issues, herein, we design and fabricate an intelligent tubular nanostructure of hierarchical hollow nanotubes, which are assembled by NiSx/MoS2 NSs encapsulated into N-doped carbon microtubes (NiSx/MoS2@NCMTs). The N-doped carbon microtubes (NCMTs) serve as a conductive skeleton, integrating with NiSx/MoS2 NSs and ensuring their well-distribution, thereby maximally exposing more active sites. Additionally, the tube-like structure is favorable for increasing the mass transfusion to ensure their excellent catalytic performance. Profiting from their component and structural advantages, the obtained NiSx/MoS2@NCMTs exhibit a surprisingly enhanced enzyme-like activity. Based on these, a facile colorimetric sensing platform to detect H2O2 and GSH has been developed. This proposed approach can be expected to synthesize a series of tubular heterostructured MoS2-based composites, which will be widely applied in catalysis, energy storage, disease diagnosis, etc.

Bifunctional Zinc-Molybdate or Zinc molybdenum Oxide/Metal-Nitrogen-Carbon catalytic layers with improved four-electron selectivity for oxygen reduction in acidic medium

Platinum-group-metal-free metal-nitrogen-carbon catalysts for the oxygen reduction reaction have demonstrated high initial activity and power performance in proton exchange membrane fuel cells. The main challenge facing this class of catalysts is their poor durability in operating acidic fuel cells. Their key operando degradation mechanisms involve oxidative attacks triggered by the catalysis of the oxygen reduction on atomically-dispersed 3d transition metals. Reactive oxygen species such as H2O2 or radical species are particularly aggressive to the carbon matrix. Minimizing H2O2 by-product formation during oxygen reduction or actively scavenging any formed H2O2 are therefore promising routes to improve their durability.Here, we report that Zn-molybdate and Zn molybdenum oxide have low activity towards H2O2 decomposition and electro-reduction in acid, but result in a strong synergistic effect with various M-N-C catalysts. The addition of α-ZnMoO4 or Zn3(OH)2(MoO4)2 in cathode layers resulted in improved four-electron ORR selectivity of M-N-C catalysts (M = Fe, Co, Cr) as well as moderately improved durability in accelerated stress tests in O2-saturated pH 1 electrolyte. The improvement in selectivity could be rationalized by hydrogen peroxide electro-reduction measurements and catalase enzyme-like activity tests. Both types of measurements revealed higher reactivity towards H2O2 scavenging when Metal-N-C catalysts are physically mixed (in a catalytic layer) or together in a suspension in solution with Zn-molybdate or Zn molybdenum oxide, revealing a synergy effect. Control experiments with ZnCl2 and Na2MoO4 salts however suggest that leached ions from ZnMoO4 in acidic solution are likely at the root of the synergy effect.

G-/C-rich ssDNA-based Fe and Cu/Fe nanoclusters with peroxidase-like activity for intracellular ROS production and cytotoxicity applications.

Five G-/C-rich single-stranded DNA (ssDNA) with different sequences and lengths were templated to prepare the DNA-Cu, DNA-Fe, and bimetallic DNA-Cu/M nanoclusters (NCs). The peroxidase-like activities of these nanomaterials were studied using H2O2 and 3,3',5,5''-tetramethylbenzidine (TMB) as the reaction substrates in HAc-NaAc buffer. It was found that T30-G2-Fe NCs and T30-G2-Cu/Fe NCs, with a size of about 2nm, exhibit similar and the strongest enzyme-like activity under optimal conditions. Both NCs possess a similarly high affinity to substrates, and the Michaelis-Menten constant (Km) values to TMB and H2O2 are about 11 and 2-3 times lower than those of natural horseradish peroxidase (HRP), respectively. The activity of both nanozymes decreases to about 70% after being kept for one week in pH 4.0 buffer at 4°C, which is comparable with HRP. Hydroxyl radicals (•OH) are the main reactive oxygen species (ROS) produced in the catalytic reaction. Moreover, both NCs can facilitate in situ generation of ROS in HeLa cells using endogenous H2O2. MTT assays indicate that the T30-G2-Cu/Fe NCs exhibit the strong selective cytotoxicity to HeLa cells over HL-7702 cells. The cellular viability is about 70% and 50% after incubating with 0.6M NCs for 24h without or with 2mM H2O2, respectively. The current study shows that the T30-G2-Cu/Fe NCs have the potential for chemical dynamic treatment (CDT).

A Rational Design of Metal–Organic Framework Nanozyme with High-Performance Copper Active Centers for Alleviating Chemical Corneal Burns

HighlightsInspired by metalloenzymes with well-defined coordination structures, a series of Cu-X metal–organic frameworks (MOFs) nanozymes with tunable copper active centers were successfully constructed.Experimental and theoretical results strongly supported that precisely tuning the coordination of halogen atoms could directly regulate the enzyme-like activities of Cu-X MOFs by influencing their spatial configuration and electronic structure.The optimal Cu–Cl MOF with excellent enzyme-mimicking activities could effectively relieve ocular chemical burns by possible antioxidant and antiapoptotic mechanisms.

Peroxidase-like Activity of CeO2 Nanozymes: Particle Size and Chemical Environment Matter.

The enzyme-like activity of metal oxide nanoparticles is governed by a number of factors, including their size, shape, surface chemistry and substrate affinity. For CeO2 nanoparticles, one of the most prominent inorganic nanozymes that have diverse enzymatic activities, the size effect remains poorly understood. The low-temperature hydrothermal treatment of ceric ammonium nitrate aqueous solutions made it possible to obtain CeO2 aqueous sols with different particle sizes (2.5, 2.8, 3.9 and 5.1 nm). The peroxidase-like activity of ceria nanoparticles was assessed using the chemiluminescent method in different biologically relevant buffer solutions with an identical pH value (phosphate buffer and Tris-HCl buffer, pH of 7.4). In the phosphate buffer, doubling CeO2 nanoparticles' size resulted in a two-fold increase in their peroxidase-like activity. The opposite effect was observed for the enzymatic activity of CeO2 nanoparticles in the phosphate-free Tris-HCl buffer. The possible reasons for the differences in CeO2 enzyme-like activity are discussed.

A single-atom iron nanozyme reactor for α-ketoglutarate synthesis

Efficient removal of the by-product hydrogen peroxide (H2O2) in the oxidase-catalyzed reactions is a major challenge in biocatalysis that hinders the production of high yields of ketoacids. Here, we demonstrate the use of single-atom Fe nanozymes (SAFs) for H2O2 decomposition inspired by natural enzymes, to improve the efficiency of L-Glutamate oxidase (LGOX)-assisted catalysis for α-ketoglutarate (α-KG) synthesis. SAFs exhibit Metal-Nitrogen coordination and atomically dispersed active sites, providing superior enzyme-like activity for H2O2 decomposition. The SAFs@LGOX nanozyme-enzyme nanoreactors exhibit high catalytic efficiency due to in situ removal of H2O2 by SAFs during the deamination reaction. Additionally, SAFs enhance the pH and temperature tolerance, as well as thermal stability of LGOX. The nanoreactors achieved about 90% substrate conversion to α-KG within 2.5 h, compared to almost complete oxidation of the product in the absence of single atom Fe active sites. These findings suggest that the nanozyme-based strategy for rapid byproducts removal through mimicking enzymatic activity has promising applications in biocatalysis and may inspire the design of more effective nanozymes.

Nanomaterials against intracellular bacterial infection: from drug delivery to intrinsic biofunction.

Fighting intracellular bacteria with strong antibiotics evading remains a long-standing challenge. Responding to and regulating the infectious microenvironment is crucial for treating intracellular infections. Sophisticated nanomaterials with unique physicochemical properties exhibit great potential for precise drug delivery towards infection sites, along with modulating infectious microenvironment via their instinct bioactivity. In this review, we first identify the key characters and therapeutic targets of intracellular infection microenvironment. Next, we illustrate how the nanomaterials physicochemical properties, such as size, charge, shape and functionalization affect the interaction between nanomaterials, cells and bacteria. We also introduce the recent progress of nanomaterial-based targeted delivery and controlled release of antibiotics in intracellular infection microenvironment. Notably, we highlight the nanomaterials with unique intrinsic properties, such as metal toxicity and enzyme-like activity for the treatment of intracellular bacteria. Finally, we discuss the opportunities and challenges of bioactive nanomaterials in addressing intracellular infections.

Promoting sensitive colorimetric detection of hydroquinone and Hg2+ via ZIF-8 dispersion enhanced oxidase-mimicking activity of MnO2 nanozyme

Reducing the agglomeration and improving the dispersibility in water of two-dimensional (2D) nanozymes is one of the effective ways to improve their enzyme-like activity. In this work, we propose a method by constructing zeolitic imidazolate framework-8 (ZIF-8)-dispersed 2D manganese-based nanozymes to achieve the specific regulated improvement of oxidase-mimicking activity. By in-situ growth of manganese oxides nanosheets of MnO2(1), MnO2(2) and Mn3O4 on the surface of ZIF-8, the corresponding nanocomposites of ZIF-8 @MnO2(1), ZIF-8 @MnO2(2), and ZIF-8 @Mn3O4 were prepared at room temperature. The Michaelis-Menton constant measurements indicated that ZIF-8 @MnO2(1) exhibits best substrate affinity and fastest reaction rate for 3,3′,5,5′-tetramethylbenzidine (TMB). The ZIF-8 @MnO2(1)-TMB system was exploited to detection of trace hydroquinone (HQ) based on the reducibility of phenolic hydroxyl groups. In addition, by employing the fact that the cysteine (Cys) with the excellent antioxidant capacity can bind the Hg2+ based on the formation of “S-Hg2+” bonds, the ZIF-8 @MnO2(1)-TMB-Cys system was applied to detection of Hg2+ with high sensitivity and selectivity. Our findings not only provide a better understanding of the relationship between dispersion of nanozyme and enzyme-like activity, but also provide a general method for the detection of environmental pollutants using nanozymes.

Two birds with one stone: triple negative breast cancer therapy by PtCo bimetallic nanozyme coated with gemcitabine-hyaluronic acid-polyethylene glycol

For the treatment of triple-negative breast cancer (TNBC), without expression of estrogen, progesterone and HER2 receptors, specific treatment guideline is still under criticism, especially in tumor hypoxia. But assuming the molecular similarity of TNBC with breast cancer gene-1-related cancers, gemcitabine may be used in TNBC treatment on the nanozyme platform combined with photodynamic therapy (PDT). After designing the nanozyme with four components, platinum–cobalt: with catalase/peroxidase capabilities, hyaluronic acid: nanozyme targeting by interacting with CD44 receptor, poly[ethylene glycol]: water-soluble macromolecule for immune escape, and Gem: antitumor drug, its physicochemical properties was investigated by thermogravimetric, X-ray diffraction and energy dispersive X-ray, and therapeutic effects in in vitro and in vivo. The results show that platinum–cobalt@gemcitabine-hyaluronic acid-polyethylene glycol (PtCo@Gem-HA-PEG) especially synergized with PDT has high toxicity on 4T1 cells and tumor by enhancing the catalase-/peroxidase-like activities to produce O2, O2•− and •OH, and increase the intracellular free radicals. PtCo@Gem-HA-PEG inhibits tumor development by increasing drug accumulation in the tumor and enhancing apoptotic mechanisms through synergistic activity with PDT. Nevertheless, the major organ damage confirmed by the histological method in the long-term application of PtCo@Gem-HA-PEG, makes their application challenging due to permanent catalytic activity. However, results of improved drug permeability based on reduced hypoxia, higher drug retention, and enzyme-like activity that could be synergized with other therapeutic approaches like a PDT, have made their use attractive. Hence, this study provides a promising path in the TNBC treatment by nanozymes, which requires further toxicological investigations.Graphic

Reaction Mechanisms and Kinetics of Nanozymes: Insights from Theory and Computation.

"Nanozymes" usually refers to inorganic nanomaterials with enzyme-like catalytic activities. The research into nanozymes is one of the hot topics on the horizon of interdisciplinary science involving materials, chemistry, and biology. Although great progress has been made in the design, synthesis, characterization, and application of nanozymes, the study of the underlying microscopic mechanisms and kinetics is still not straightforward. Density functional theory (DFT) calculations compute the potential energy surfaces along the reaction coordinates for chemical reactions, which can give atomistic-level insights into the micro-mechanisms and kinetics for nanozymes. Therefore, DFT calculations have been playing an increasingly important role in exploring the mechanisms and kinetics for nanozymes in the past years. The calculations either predict the microscopic details for the catalytic processes to complement the experiments or further develop theoretical models to depict the physicochemical rules. In this review, the corresponding research progress is summarized. Particularly, the review focuses on the computational studies that closely interplay with the experiments. The relevant experimental results without DFT calculations will be also briefly discussed to offer a historic overview of how the computations promote the understanding of the microscopic mechanisms and kinetics of nanozymes.

Single-Atom Fe Nanozyme with Enhanced Oxidase-like Activity for the Colorimetric Detection of Ascorbic Acid and Glutathione

Single-atom nanozymes (SAzymes) have drawn ever-increasing attention due to their maximum atom utilization efficiency and enhanced enzyme-like activity. Herein, a facile pyrolysis strategy is reported for the synthesis of the iron-nitrogen-carbon (Fe-N-C) SAzyme using ferrocene trapped within porous zeolitic imidazolate framework-8 (ZIF-8@Fc) as a precursor. The as-prepared Fe-N-C SAzyme exhibited exceptional oxidase-mimicking activity, catalytically oxidizing 3,3',5,5'-tetramethylbenzidine (TMB) with high affinity (Km) and fast reaction rate (Vmax). Taking advantage of this property, we designed two colorimetric sensing assays based on different interaction modes between small molecules and Fe active sites. Firstly, utilizing the reduction activity of ascorbic acid (AA) toward oxidized TMB (TMBox), a colorimetric bioassay for AA detection was established, which exhibited a good linear range of detection from 0.1 to 2 μM and a detection limit as low as 0.1 μM. Additionally, based on the inhibition of nanozyme activity by the thiols of glutathione (GSH), a colorimetric biosensor for GSH detection was constructed, showing a linear response over a concentration range of 1-10 μM, with a detection limit of 1.3 μM. This work provides a promising strategy for rationally designing oxidase-like SAzymes and broadening their application in biosensing.

Nanozyme-Based Supramolecular Self-Assembly As an Artificial Host Defense System For Treatment of Bacterial Infections.

The proper functioning of host defense system (HDS) is the key to combating bacterial infection in biological organisms. However, the delicate HDS may be dysfunctional or dysregulated, resulting in persistent infection, tissue damage, or delayed wound healing. Herein, a powerful artificial "host defense system" (aHDS) is designed and constructed for treatment of bacterial infections. First, the aHDS can quickly trap the bacteria by electrostatic interactions. Next, the system can be stimulated to produce large amounts of cytotoxic reactive oxygen species (ROS) and exert strong antibacterial effects, which can further regulate the immune microenvironment, leading to macrophage polarization from M0 to pro-inflammatory phenotype (M1) for synergistic bacteria killing. At the later stages, the system can exhibit excellent antioxidant enzyme-like activities to reprogram the M1 macrophage to anti-inflammatory phenotype (M2) for accelerating wound healing. This powerful aHDS can effectively combat the bacteria and avoid excessive inflammatory responses for the treatment of bacteria-infected wounds.