A Review on Metal-and Metal Oxide-Based Nanozymes:Properties,Mechanisms,and Applications

Since the ferromagnetic(Fe_(3)O_(4))nanoparticles were firstly reported to exert enzyme-like activity in 2007,extensive research progress in nanozymes has been made with deep investigation of diverse nanozymes and rapid development of related nanotechnologies.As promising alterna-tives for natural enzymes,nanozymes have broadened the way toward clinical medicine,food safety,environmental monitoring,and chemical production.The past decade has witnessed the rapid development of metal-and metal oxide-based nanozymes owing to their remarkable physicochemical proper-ties in parallel with low cost,high stability,and easy storage.It is widely known that the deep study of catalytic activities and mechanism sheds sig-nificant influence on the applications of nanozymes.This review digs into the characteristics and intrinsic properties of metal-and metal oxide-based nanozymes,especially emphasizing their catalytic mechanism and recent applications in biological analysis,relieving inflammation,antibacterial,and cancer therapy.We also conclude the present challenges and provide insights into the future research of nanozymes constituted of metal and metal oxide nanomaterials.

Photothermally Enhanced Dual Enzyme-mimic Activity of Gold-Palladium Hybrid Nanozyme for Cancer Therapy

Based on characteristics of the tumor microenvironment(TME),including acidity,hypoxia,inflammation and hydrogen peroxide overload,combined with emerging nanotechnologies,designing nanoplatforms with TME specificity/responsiveness for tumor treatment is a promising nanotherapeutic strategy.In this work,a multifunctional gold-palladium bimetallic cascade nanozyme was constructed for effective photothermal-enhanced cascade catalyzed synergistic therapy of tumors.The dumbbell-like Au-Pd bimetallic nanomaterial(Au NRs-Pd@HA)was obtained by reducing palladium on gold nanorods with ascorbic acid(AA)and further modified with hyaluronic acid(HA).The introduction of HA brings biocompatibility and targeting properties.The zebrafish embryos model showed that Au NRs-Pd@HA had good biocompatibility and low biotoxicity.Au NRs-Pd@HA can induce catalytic conversion of glucose to generate H_(2)O_(2) efficiently,and subsequently undergo cascade reaction to produce abundant·OH radicals,exhibiting peroxidase-like(POD-like)and glucose oxidase-like(GOD-like)capabilities.The generated·OH was a key factor for tumor ablation.Meanwhile,Au NRs-Pd@HA exhibits good photothermal performance under 808 nm irradiation,in favor of photothermal therapy(PTT).Especially,the POD-like and GOD-like activities were significantly enhanced due to the photothermal effect.The synergistic PTT and photothermal-enhanced nanozymes with cascade catalytic effect enabled efficient and safe cancer therapy.

GSH-triggered sequential catalysis for tumor imaging and eradication based on star-like Au/Pt enzyme carrier system

Distinctively different metabolism between tumor cells and normal cells endows tumor tissues unique microenvironment.In this regard,we have successfully prepared a sequential catalytic platform based on Au/Pt star for tumor theragnostic.The multifunctional probes consisted of a gold/platinum star-shaped core(Au/Pt star)conjugated with a GSH-sensitive disulfide bond(S–S),a targeting ligand(rHSA-FA),a near-infrared fluorophore(IR780)and glucose oxidase(GOx).When systemically administered in a xenografted murine model,the probes specifically targeted the tumor sites.As the disulfide linker was cleaved by intracellular GSH,the IR780 molecules could be released for photo-thermal therapy&photodynamic therapy(PTT&PDT)and imaging.Subsequently,the Pt nanolayer of the Au/Pt star and the GOx formed a sequential catalytic system:GOx effectively catalyzed intracellular glucose by consuming oxygen to generate H2O2 and enhance the local acidity,and the Pt layer exhibited peroxidase-like property to catalyze H2O2 producing toxic·OH for tumor oxidative damage.Here we demonstrated that our probes simultaneously possessed a GSH-sensitive release,real-time imaging ability,and synergetic cancer starving-like therapy/enzyme oxidative therapy/PTT/PDT features,which provides a potential strategy for effective tumor theragnostic.