Study On Oxidase-like Activity Of Amino Acid @ Gold Clusters And Its Detection Of NO₂^-/NO

The research of biochemical analysis method has made great progress in recent years,and it has been applied in a wide range of fields.The biological analysis of nanomaterials has attracted wide attention of researchers.As a potential analytical probe,nanomaterials not only improve the sensitivity,but also provide a new platform for the analysis of monomolecular domain.As an emerging research field of artificial enzyme,nanozyme has attracted great interest of researchers because of its unique properties.Compared with natural enzymes and classical artificial enzymes,nanozyme has many advantages,such as low cost,easy mass production,robustness to harsh environment,long-term storage and size/composition dependence,etc.So far,many nanomaterials have been explored to simulate various natural enzymes,such as catalase,oxidase,peroxidase,superoxide dismutase(SOD)and laccase,etc.Some of them are used in biological analysis,environmental analysis and medical therapy,and various biomolecules are detected by colorimetric,fluorescent and electrochemical methods.Recently,the biosensing research on nano-materials is mainly focused on the nanozyme with mimic peroxidase activity,but there are few studies on nano-materials with mimic oxidase activity.Gold nanoclusters prepared with biomolecules as protective agents have the advantages of low toxicity,high water solubility,optical stability,electrical activity and good biocompatibility,and have been widely used in biological imaging,fluorescence labeling,and electrochemiluminescence and so on.Based on the above research background,this study combines the catalytic activity and electrocatalytic activity of nanozyme was applied to life analysis.In this study,four amino acid-protected gold clusters were selected,such as BSA@AuNCs,Cyt@AuNCs,His@AuNCs and Lys@AuNCs,of which only His@AuNCs have oxidase-like activity.The catalytic activity of nanozyme is generally lower than that of natural enzyme.Therefore,the His@AuNCs/RGO nanocomposites are easily and quickly prepared by the superposition of noncovalentπ-π,which greatly enhanced the oxidase-like activity of His@AuNCs.The catalytic activity of His@AuNCs/RGO mimetic enzyme obeys the typical Michaelis-Menten kinetics,and compared with His@AuNCs,His@AuNCs/G and His@AuNCs/GO,the catalytic activity of His@AuNCs/RGO mimetic enzyme greatly enhanced the mimic oxidase activity of His@AuNCs.His@AuNCs/RGO showed the highest affinity to substrate TMB.At the same time,compared with other nanocomposite modified electrodes,His@AuNCs/RGO-GCE has the highest electrocatalytic activity for TMB.Nitrite inhibits the enzymatic and electrocatalytic oxidation of TMB by His@AuNCs/RGO,which indicates that nitrite and TMB compete with each other for share the common catalytic activity sites.Based on the above findings,a highly efficient spectrophotometric and electrochemical sensor for the detection of nitrite has been developed,which fully combines the excellent enzyme catalytic and electrocatalytic properties of His@AuNCs/RGO.The linear range of nitrite concentration was 10 to 500μM(r~2=0.98),and the detection limit was 2μM.In electrochemical detection,there was a good linear relationship between 2.5μM and5700μM for the detection of nitrite by DPV,and the detection limit was 0.7μM.There is a good linear relationship between 1.0μM and 7000μM for nitrite in i-t technique,and the detection limit is 0.5μM.The method has been successfully applied to the determination of nitrite in sausage with a recovery of 94.67%~100.28%.Therefore,the developed sensor has high sensitivity,wide linear range and low detection limit,so it has high reliability in practical samples.To realize the detection of NO used the characteristics of His@AuNCs/RGO biosensor.This study could provide a new idea for the development and application of various biosensors in biochemistry and analytical chemistry.