Preparation,properties And Biological Applications Of Monolayer BiO_2-x Nanomaterials

Most of the natural enzymes are essentially proteins with high cost and poor stability,which is easily to be inactivated by many factors.Therefore,variety of artificial enzymes with high stability and low cost struggle to be the alternatives of natural enzymes in the past several decades,in order to mimic partial structure and function of enzyme.With the rapid development of nanotechnology,as a new field of artificial enzyme research,nanozymes have captured wide interest of the scientific personnel because of their distinctive character by comparison with other enzymes.By contrast with natural enzymes,nano-enzymes have the preponderance of low-budget,uncomplicated synthesis method,easier massive manufacture,long-standing storage,and strong constancy,etc.By contrast with additional artificial enzymes,nano-enzymes also exhibit distinctive character,such as great superficial area for more embellishment and biological conjugation,their dimension-?form-,framework-,composition-?reliant activities of catalysis,intelligent reply to exoteric stimulation,capability beyond catalysis,the ability of self-assembly,etc.The study of nanozymes is of great significance for the development of nanotechnology,materials,biology and chemistry.Here,monolayer bismuth oxide nanosheets with rich vacancies were synthesized and chemically modified with dextran.The enzyme activity and catalytic mechanism of the materials before and after modification were explored.And the materials were applied to regulate the phenotype of macrophages and detect ascorbic acid.?1?The BiO_2-x nanosheets were synthetized by hydro-thermal method,and then the BiO_2-x nanosheets were peeled off into monolayer BiO_2-x by liquid phase stripping using 50%ethanol as the stripping and dispersing solvent.By controlling the pulverization and ultrasonic time,the size of the monolayer BiO_2-x is controlled to about 100 nm.In order to improve the water solubility and stability of the monolayer BiO_2-x,a glucan-modified monolayer BiO_2-x(dex-BiO_2-x)was prepared.The two materials were characterized separately.?2?The enzymatic properties of monolayer BiO_2-x and dex-BiO_2-x were studied.The results show that monolayer BiO_2-x possesses the catalytic activity of oxidase and catalase.It mainly exhibits oxidase activity at acidic pH,but mainly exhibits catalase activity under neutral conditions.While dex-BiO_2-x has almost no change in the catalytic activity of the simulated oxidase compared to the u nmodified monolayer BiO_2-x,the catalytic activity of the simulated catalase is almost reduced to zero.The catalytic mechanism of the enzymatic activity of monolayer BiO_2-x was subsequently explored.The results show that monolayer BiO_2-x contains a large number of vacancies,which makes monolayer BiO_2-x more catalytic than other bismuth oxide materials.?3?The process of exerting oxidase activity is related to the production of ROS,the process of exerting catalase activity is related to the removal of ROS,while the production of ROS can induce M1 activation of macrophages,and the removal of ROS can induce M2 activation of macrophages.Therefore,the activity of monolayer BiO_2-x-x and dex-BiO_2-x can be used to regulate the ROS in macrophages so as to regulate the phenotype of macrophages.In addition,dex-BiO_2-x has only the activity of simulated oxidase,so it has more advantages than other nanomaterials with multiple simulated enzyme activities in TMB colorimetric sensing system.In this paper,dex-BiO_2-x has been successfully applied to the detection of ascorbic acid.