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Nanozymes have been designed to address the limitations of high cost and poor stability involving natural enzymes in analytical applications. However, the catalytic efficiency of the nanozyme still needs to be improved so that it can meet the selectivity and stability requirements of accurate biomolecule analysis. Here, we presented structure defects of metal-organic frameworks (MOFs) as a tuning strategy to regulate the catalytic efficiency of artificial nanozymes and investigated the roles of defects on the catalytic activity of oxidase-like MOFs. Structural defects were introduced into a novel Co-containing zeolitic imidazolate framework with gradually loosened morphology (ZIF-L-Co) by doping cysteine (Cys). It was found that with the increase in defect degree, the properties of materials such as ascorbate oxidase-like, glutathione oxidase-like, and laccase-like were obviously enhanced by over 5, 2, and 3 times, respectively. In-depth structural investigations indicate that the doping of sulfur inducing structural defects which may destroy the equilibrium state between cobalt and nitrogen in 2-methylimidazole and distort the crystal lattice, thereby enhancing the adsorption of oxygen and thus promoting the oxidase-like activity. The ZIF-L-Co-10 mg with enhanced ascorbate oxidase- and laccase-like activity was loaded into a microreactor and integrated into an online electrochemical system (OECS) in the upstream of the detector. This nanozyme-based microreactor can completely remove ascorbic acid, dopamine, and 3,4-dihydroxyphenylacetic acid which are the main interference toward uric acid (UA) electrochemical measurement, and the ZIF-L-Co-10 mg Cys-based OECS system is capable of continuously capturing UA change in rat brain following ischemia-reperfusion injury. Structure defect tuning of ZIF-L-Co not only provides a new regulatory strategy for artificial nanozyme activity but also provides a critical chemical platform for the investigation of UA-related brain function and brain diseases.

The elevated antioxidant defense system in cancer cells can lead to resistance to treatments involving ROS. Breaking the redox balance of the cell system through a "open up the source and regulate the flow" strategy can inhibit the growth of cancer cells and thus design a cancer treatment strategy. Here, cobalt single atom-supported N-doped carbon nanozymes (Co SA-N/C) were synthesized via a simple sacrificial template method, which can mimic the properties of ascorbate oxidase and glutathione oxidase effectively. The synthesized Co SA-N/C can induce the generation of active oxygen by accelerating the oxidation of ascorbic acid (AA) and destroy the endogenous active oxygen scavenging system by consuming the main antioxidant, glutathione (GSH). In-depth in vitro and in vivo investigations indicate that compared with solo therapy, Co SA-N/C together with AA can significantly enhance the anti-tumor efficiency by simultaneously elevating oxidative stress and consuming the overexpressed glutathione (GSH) through the redox reaction catalyzed by Co SA-N/C. This work provides a promising route for developing nanozyme-guided and ascorbate-based antitumor agents.

Despite the extensive investigation of the nanozymes exhibit their favorable performance compared to natural enzymes, nevertheless, the highly specific nanozyme still needs to be developed so that it can meet the requirements of exploring the mechanism as well as administration of related diseases and selective monitoring in biological system. In this study, self-assembled glutathione-Cu/Cu

Compared with typical two-dimensional electrodes, the three-dimensional (3D) cell culture platform can simulate the real cell survival environment for cell growth to accurately reproduce cell functions. Moreover, considering that living cells are exposed to various of mechanical force in the microenvironment, the construction of 3D electrodes with excellent flexible, stretchable, and biocompatibility is of great significance to real-time monitor mechanically evoked biomolecule release from cells. Herein, we demonstrated a straightforward and effective three-step approach to fabricate three-dimensional flexible and stretchable gold foam scaffold (3D Au foam scaffold) for construction of 3D cell culture integrated electrochemical sensing platform. The excellent biological and electrical properties of Au nanostructures and porous networks of the 3D scaffold endow the platform with desirable biocompatibility and sensitive electrochemical sensing performance. As a proof of concept, the 3D Au foam scaffold functionalized with cobalt based nanocubes (Co NCs/Au foam scaffold) was validated to provide 3D culture for human umbilical vein endothelial cells (HUVECs), and synchronously real-time monitor superoxide anion (O

Dehydrogenases (DHs) are widely explored bioelectrocatalysts in the development of enzymatic bioelectronics like biosensors and biofuel cells. However, the relatively low intrinsic reaction rates of DHs which mostly depend on diffusional coenzymes (e.g., NAD+) have limited their bioelectrocatalytic performance in applications such as biosensors with a high sensitivity. In this study, we find that rare-earth elements (REEs) can enhance the activity of NAD+-dependent glutamate dehydrogenase (GDH) toward highly sensitive electrochemical biosensing of glutamate in vivo. Electrochemical studies show that the sensitivity of the GDH-based glutamate biosensor is remarkably enhanced in the presence of REE cations (i.e., Yb3+, La3+ or Eu3+) in solution, of which Yb3+ yields the highest sensitivity increase (ca. 95%). With the potential effect of REE cations on NAD+ electrochemistry being ruled out, homogeneous kinetic assays by steady-state and stopped-flow spectroscopy reveal a two-fold enhancement in the intrinsic reaction rate of GDH by introducing Yb3+, mainly through accelerating the rate-determining NADH releasing step during the catalytic cycle. In-depth structural investigations using small angle X-ray scattering and infrared spectroscopy indicate that Yb3+ induces the backbone compaction of GDH and subtle β-sheet transitions in the active site, which may reduce the energetic barrier to NADH dissociation from the binding pocket as further suggested by molecular dynamics simulation. This study not only unmasks the mechanism of REE-promoted GDH kinetics but also paves a new way to highly sensitive biosensing of glutamate in vivo., This study demonstrated that REEs serve as allosteric promoters for bioelectrocatalysis of glutamate dehydrogenase by triggering subtle reorientation of peptide segments, consequently expediting phase coupling along with the catalytic scheme.

The continuous detection of glucose is significant for revealing its role in neuron protection and for diagnosis of various diseases. In this study, for the first time, a nonenzymatic online optical detection platform (OODP) for glucose measurement in rat brain utilizing the tandem enzyme activity of V2O5 nanobelts is developed. V2O5 nanobelts were synthesized via a facile solvothermal strategy, and for the first time it is found that the V2O5 nanobelts possess dual enzyme-like activity, i.e., glucose oxidase (GOx)-like and peroxidase-like activity, and can act as a "tandem nanozyme". To investigate the mechanisms of the GOx-like property, we built an adsorption model, and the RPBE density functional calculations indicate that the glucose molecule can be adsorbed on the V2O5 plane. Based on the ability of V2O5 nanobelts to mimick tandem enzymes, a nonenzymatic online optical detection platform (OODP) for the continuous monitoring of glucose in rat brain was designed, which exhibits excellent stability, high selectivity, and a wide linear detection range from 0.2 to 5 mM and records cerebral glucose alterations in the calm/ischemia model. This facile but reliable nonenzymatic online optical glucose measurement compares favorably with natural enzyme-based online electrochemical glucose analytical systems, and its ready adoption by physiologists and pathologists will facilitate the understanding of brain function and the pathogenesis of diabetes.

Dual biocidal groups of N-halamine and pyridinium were used to modify surface of magnetic sub-microparticles to exert enhanced synergistic antibacterial capacity. Magnetic silica Fe3O4 sub-microparticles (SMPs) were synthesized and then encapsulated with interpenetrating polymer network (IPN) of polystyrene (PS) and poly(acrylic acid) (PAA). The carboxylic acid groups of PAA were used as surface reactive sites to bond with amino groups of 4-aminopyridine through amidation reaction. N-halamine/pyridinium-derivatized magnetic sub-microparticles were sequentially produced by quaternization of the pyridine to pyridinium with 1-chlorohexane and chlorination of amide N–H to N-halamine with NaClO. The synthetic steps and products were characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectrocsopy (XPS). The N-halamine/pyridinium-derivatized SMPs with dual biocidal functionalities showed faster deactivation abilities against both Escherichia coli and Staphylococcus aureus compared with their counterparts that contained only N-halamine or pyridinium, and exhibited promising stability toward repeated washing and long-term storage. The designed SMPs in this study offer potential and ideal candidates for sterilization application due to multiple advantages including improved synergistic biocidal ability, high surface area, and easy recyclability.

Due to its unique structure and high porosity, metal-organic frameworks (MOFs) can act not only as nanozyme materials but also as carriers to encapsulate natural enzymes and thus have received extensive attention in recent years. However, a few research studies have been conducted to investigate MOF as a template to generate and tune nanozymes in the structure and performance. In this work, the "raisin pudding"-type ZIF-67/Cu0.76Co2.24O4 nanospheres (ZIF-67/Cu0.76Co2.24O4 NSs) were obtained by rationally regulating the weight ratio of ZIF-67 and Cu(NO3)2 in the synthesis process. Here, ZIF-67 not only acts as a template but also provides a cobalt source for the synthesis of cobalt copper oxide on the surface of ZIF-67/Cu0.76Co2.24O4 NSs with multiple enzyme-like activities. The ZIF-67/Cu0.76Co2.24O4 NSs can mimic four kinds of enzymes with peroxidase-like, glutathione peroxidase-like, superoxide dismutase-like, and laccase-like activities. Based on its laccase-like activity, an online electrochemical system for continuous monitoring of 3,4-dihydroxyphenylacetic acid with good linearity in the range of 0.5-20 μM and a detection limit of 0.15 μM was established. Furthermore, the alteration of DOPAC in the brain microdialysate before and after ischemia of the rats' brain was also successfully recorded. This work not only raises a new idea for the synthesis of nanozyme materials with multiple enzyme activities but also provides a new solution for the detection of neurotransmitters in living brains.

A novel electrochemical online system for indirect, highly sensitive and selective online monitoring of ATP in the cerebral microdialysate is presented based on the particular reaction of ATP with zeolitic imidazole framework-90 (ZIF-90) encapsulated laccase microcrystals (laccase@ZIF-90) and the natural catalytic activity of laccase.

Artificial nanozymes have been designed to solve the problems of high cost and poor stability involving natural enzymes in analytical applications. Nevertheless, the catalytic efficiency of the nanozyme still needs to be improved so that it can meet the stability and sensitivity requirements of continuous biological detection. We presented an effective tailoring strategy to enhance the enzyme-like activities of Prussian-blue-analog-based nanozymes. Molybdenum-polysulfide-deposited nickel-iron bimetal Prussian-blue-analog-based hollow nanocages (Nanocages) with peroxidase-, catalase-, and laccase-mimicking activities were synthesized. The doping of molybdenum successfully tailored the size, morphology, composition, and complex structure of the Nanocage, and the peroxidase- and laccase-mimicking activities of the Nanocage nanozyme were enhanced by over 37 and 27 times, respectively, compared with pristine Prussian blue analogs. Moreover, in environments of harsh pH, high temperature, and high salt concentration, Nanocages exhibited much higher stability than natural enzymes. The peroxidase- and catalase-mimicking activities were applied to eliminate reactive oxygen species in cells, whereas the laccase-like activity of Nanocages was integrated with an online sensing platform for in vivo and continuous optical hydrogen sulfide monitoring in the brains of living rats. Our findings may provide possibilities for advancing the design strategy of highly active nanozymes as well as nanozyme-based in vivo detection methods and will offer unique opportunities for their involvement in bioanalytical chemistry.

The continuous detection of glucose is significant for revealing its role in neuron protection and for diagnosis of various diseases. In this study, for the first time, a nonenzymatic online optical detection platform (OODP) for glucose measurement in rat brain utilizing the tandem enzyme activity of V

Antibacterial modification of polymers with potent biocides via an efficient and universal approach is very desirable in both academia and industry. A polysiloxane with both quaternary ammonium and N-chloramine was prepared via a facile three-step synthetic route. Poly(methylhydrosiloxane) (PMHS) was first reacted with 2-(dimethylamino)ethyl acrylate to introduce an ending tertiary amine that was subsequently quaternized with 3-(3-chloropropyl)-5,5-dimethylhydantoin (CPDMH). The 5,5-dimethylhydantoin moiety was then transformed into its N-chloramine counterparts by chlorination with tert-butyl hypochlorite to produce quaternary ammonium (quat)/N-chloramine polysiloxane. The CO2-philic quat/N-chloramine polysiloxane was interpenetrated into polyethylene terephthalate (PET) in supercritical carbon dioxide (scCO2) and formed a 70 nm biocidal layer. The synthetic procedures and interpenetration results were characterized with Fourier transform infrared spectroscopy (FTIR), 1H NMR, scanning electron microscopy...