Preparation Of Complex Nanozyme Based On Cerium Dioxide And Investigation Of Their Application In Assays

As a type of vital biocatalysts,natural enzymes play an important role in the metabolism of living organisms.Under mild conditions,they can catalyze a host of biochemical reactions in living organisms with high efficiency and specificity.However,since most of the natural enzymes are proteins,their activity generally exhibits high dependence on the environment when they are subjected to harsh conditions（such as strong acid,base,or an excessively high temperature）.Their activity is easily lost due to the change of the structures.These shortcomings limit the large-scale applications of natural enzymes in real word.In order to circumvent these limitations,the preparation of mimic enzymes with high stability has been extensively studied and reported over recent decades.Among them,ascribe to the rapid development of nanotechnology,nanozymes with enzyme-mimicking properties have become one of the major research direction in this area.Compared with natural enzymes,nanozymes present many merits,including high stability,large specific surface area,tunable catalytic activity,easy preparation and low cost.To date,various nanomaterials with mimetic activities of natural enzymes（including peroxidase,superoxide dismutase,catalase and oxidase）have been reported.Furthermore,based on their excellent catalytic properties,these nanozymes have been extensively used in many fields such as detection,biomedical,environmental protection and so on.Among various nanozymes,CeO₂ has received special attention due to its excellent oxygen storage capacity,mixed oxidation states（Ce（III）and Ce（IV））,and high catalytic activity.Through the conversion between Ce（III）and Ce（IV）,CeO₂ exhibits strong redox behavior and mimicking properties of various enzymes such as oxidase,catalase,superoxide dismutase and peroxidase.Therefore,the rational design of nanocomposites based on CeO₂ can provide a very promising strategy to improve the overall catalytic performance of the material,thus developing a new type of highly efficient nanozyme.In this paper,two kinds of composite nanozymes were prepared based on CeO₂.The main research contents are as follows:（1）The CeO₂/GOx composite nanozyme was constructed and its catalytic activity was investigated.The experimental results showed that the CeO₂/GOx nanocomposite exhibited higher catalytic efficiency than the mixed CeO₂ and GOx.In addition,the nanozyme complex showed excellent cycle properties and stability.Furthermore,based on the excellent catalytic performance of CeO₂/GOx nanocomposite,a colorimetric biosensor has been constructed.This biosensor was used to detect glucose and it exhibited high selectivity and sensitivity.（2）The Pt/cube-CeO₂ nanocomposite was prepared based on the hybrid of CeO₂ nanocubes and platinum nanoparticles.Then the catalytic activity of the peroxide mimic enzyme was investigated.The results showed that the CeO₂/Pt nanocomplex enzyme exhibited a remarkably enhanced peroxidase-mimicking activity compared with CeO₂ and Pt nanoparticles alone.In addition,the nanocomposite enzyme presented good stability and can be reused for many times.Finally,based on this newly developed peroxide mimic enzyme,we have constructed a colorimetric biosensor and realized the detection of H₂O₂.