Study Of Electrochcmical Biosensor Based On Functional Nanocomposite Materials

Electrochemical biosensors have some outsanding advantages includingexcellent selectivity, high sensitivity, rapid response, easy to be miniaturized andautomation. Therefore, they have potential applications in biology, environmentalmonitoring, chemical measurements in the agriculture and food industry.Nanomaterials as new material are attractive in the developement of biosensors dueto their novel optical, electrical, catalytic properties and favorable biocompatibility.With the introduction of nanomaterials, the performance of biosensor has a greatlyimprovement. In this paper, halloysite nanotubes(HNTs), carrageenan, graphene (GR),and carbon nanotubes were applied for the fabrication of electrochemical biosensors.The major contents in this thesis are deseribed as fllows:(1) A novel graphene/ionic liquid(HNTs/ILs) nanocomposite film was constructed.With the benefits of high speci?c surface area of HNTs and high ionic conductivity ofILs, the HNTs/ILs composite?lm provided not only high loading of hemoglobin(Hb)molecules, but also a more suitable microenvironment for immobilized Hb to realizea faster direct electron transfer and retain its good bioactivity. TheHb/HNTs/ILs-modified electrode exhibited high electrocatalytic activities toward thereduction of H2O2with a wide linearity range from7.5×10-6to9.75×10-5M, adetection limit of2.4M (S/N=3), high sensitivity of10.51μA mM-1and goodreproducibility. Therefore, the HNTs/ILs nanocomposite film could be used aspromising platform for developing novel types of third-generation biosensors.(2) A biocompatible IL-carrageenan composite?lm was successfully developed,it has been used for the immobilization of Hb to achieve its direct electron transferand biosensor application.At the same time, Hb-IL-carrageenan modified electrodeshowed good electrocatalytic activity for reduction of H2O2. The reduction peakcurrents have a linear response to H2O2concentration in the range of5×10-6～1.5×10-4M with a detection limit of2.12×10-7M (S/N=3).The sensitivity of theenzyme electrode was about13.42μA mM-1.(3) The preparation of a non-enzymatic glucose sensor was developed by electrodepositing Cu film onto the graphene(GR) modified glassy carbon electrode.FESEM was used to investigate the successful formation of the Cu/GR hybrid film.Electrochemical experiments showed that the GR greatly enhanced electrochemicalreactivity of the Cu film. The Cu/GR hybrid film modified electrode was used forsensitive detection of glucose. The sensor exhibited a wide linearity range from8×10?6M to9.4×10?4M with a correlation coefficient of0.9967, a detection limit of2.5μM (S/N=3), high sensitivity of0.225μA μM?1. These results indicated that GRand its composite materials have great promise in the electrochemical biosensingapplications.(4) A sensitive and simple electrochemical immunosensor based on enzymaticsilver deposition was constructed for the detection of aflatoxin B1(AFB1).Functionalized magnetic mutiwalled carbon nanotubes (MAGCNTs) were synthesizedelectrostatic adsorption. MAGCNTs-PEI and AFB1-BSA were immobilized on theelectrode surface. Then, a fixed amount of anti-AFB1was immobilized through theindirect competitive reaction between free AFB1and AFB1-BSA. The alkalinephosphatase (ALP) labeled anti-mouse IgG secondary antibody was bound to theelectrode surface through reaction with primary antibody. Finally, ALP catalyzed thesubstrate, ascorbic acid2-phosphate into ascorbic acid, and the silver ions in solutionto metal sinver deposited on the electrode surface. Differential Pulse Voltammetry(DPV) was carried out to quantify the metal silver.