Study On Catalytic Performance And Application Of Mimetic Enzymes Based On Gold Nanocomposites

Nano-mimetic enzymes are a new milestone in the history of artificial enzymes.Their catalytic efficiency is slightly weak,compared with natural enzymes.However,they have some advanteges such as high stability against stringent conditions,low cost,long shelf life and so on.In recent years,some of the precious metals and their compounds have been found with the catalytic activity of the enzyme.Among enzyme mimetics developed,Nano-gold and its nanocomposites have received considerable attention because of their unique size,shape,composition and structure-dependent properties.In this thesis,we studied gold nanocomposites and constructed the new nanomaterial-based artificial enzymes.The catalytic properties and kinetics of their mimetic peroxidase were studied in detail.Based on their peroxidase-like activity,we developed some colorimetric methods for the determination of MT and glucose in practical samples.In the first chapter,we briefly introduce the research status of nanomaterial mimetic enzymes and their detection application.The definition of nanometer mimetic enzyme,the preparation method of nano-gold and the research progress of mimetic enzyme in application of biomolecule and heavy metal were mainly introduced.At last,the purpose and main content of the study were introduced.In the second chapter,based on the mechanism that in the buffer of sodium acetate solution of pH 4.5,mercury that reduced to Hg⁰ and Hg⁺by sodium citrate.Then,Hg⁰ and Hg⁺was adsorbed on the surface of gold nano to form a peroxidase-like activity gold-mercury complex.While MT and gold-mercury complexes were formed Au NP-MT-Hg complex which with stronger peroxidase-like catalyzed activity by the bond of-SH and–NH_X.The complex can catalyze hydrogen peroxide oxidation of ABTS to generate ABTS^+..There by,we established a fast,sensitive photometric method for the determination of MT.The detection limit of this method was 1.55nM.The regression equation for measuring MT was?A=9.42c??M?-0.255,and the correlation coefficient was 0.997.The recoveries of MT were from 98.45%to 103.4%.In the third chapter,based on the phenomenon of the peroxidase-like activity of rGO-Hg-AuNPs complex which formed by the deposition of gold-mercury complex on the surface of GO being higher than rGO-AuNPs compounds.We studied the catalytic kinetics of rGO-Hg-AuNPs complex by UV-Vis spectrophotometer.Also we compared the rGO-Hg-AuNPs complex with HRP.It was found that the catalytic mechanism of the mimic enzyme was in accordance with the ping-pong mechanism and its affinity to TMB was stronger than HRP.At the same time,the mechanism of Hg enhancing the catalytic activity of rGO-AuNPs complex was analyzed by XPS,FTIR and TEM.In the fourth chapter,We established a new method for the determinationofglucose.Whichbasedontheprincipleof rGO-Hg-AuNPs has the activity of peroxidaze mimetic which can catalyze the hydrogen peroxide generated by the decomposition of glucose with GOD to oxidase.Then the enzyme substrate of TMB was oxidized by the resulting reactive oxygen species.This produced a color change.When the concentration of glucose in the reaction system is from2.0×10^-6 to 4.0×10^-4mol/L,the absorbance change value??A?has a good linear relationship its concentration.The linear regression equation is?A=7.95×10^-3+2.50c?mM?with the correlation coefficient of 0.997,and the detection limit was 1.79?M,and the spiked recovery rate range was from 99.7%to 104.2%.The the method have been used to detect the actual glucose in blood samples.