Several New Electrochemical Biosensors Based On Graphene Materials

Graphene based electrochemical bioensors has been extensively investigated inthe fields of medicine and health, food, environment, agriculture, defense and so on.Graphene provides unique and new opportunities for biosensor applications, due to itsoutstanding structural and physicochemical properties. However, graphene gatheredeasily and was insoluble in water and general solvent.Rencently, the functionalizationof graphene materials and their application for the development of electrochemicalbiosensors was highlighted. Layer-by-Layer self-assembly (LBL) technique has a lotof advantages such as simple operation, mild preparation conditions and suitableapplication for any basal size and shape. Consequently, it is a widely used method forthe construction of sensors. Therefore, construction of electrochemical biosensorsbased on functionalized graphene materials by using LBL method is of greatsignificance.This thesis studied the functionalization of graphene using two polymer.Polyelectrolyte-poly diallyl dimethyl ammonium chloride functionalized graphene(PDDA-G) and redox polymer-ferrocene graft polyethyleneimine functionalizedgraphene (PEI-Fc-G) were prepared and investigated. The non-covalently modifiedgraphene with PDDA and PEI-Fc exhibited good dispersivity and stability in water.PDDA and PEI-Fc not only play as dispersion but also change the surface charge ofgraphene, which provided an efficient way for the construction of electrochemicalbiosensors through LBL method. In addition, Fc exhibit electrochemical activity.Consequently, FEI-Fc-G nanocomposite might be of favorable interest for theconstruction of label-free electrochemical system.The morphology, thickness, size,roughness, homogeneity and stability of the PDDA-G and PEI-Fc-G werecharacterized by transmission electron microscope (TEM)、atomic force microscope(AFM) and Zeta potential, respectively. Results showed that the PDDA-G andPEI-Fc-G composites exhibixed net positive charge with single plate struction.This thesis studied the fabrication and application of PDDA-G/horseradish peroxidase (HRP) multilayer biosensor. UV-vis results revealed that an orderly(PDDA-G/HRP)nmultilayer were formed. Based on the inhibition of the activity ofHRP,(PDDA-G/HRP)nmodified electrode was used for the determination of cysteine,a wider linear range (4-28μM,28-146μM) was evaluated.The thesis studied the fabrication and application of PDDA-G/Prussian blueelectrochemical sensor. The TEM images indicated that the successful preparation ofPDDA-G and mercaptopropionic acid-protected gold nanoparticles (MPA@AuNPs),the scanning electron microscope (SEM) pictures indicated that PDDA-G andMPA@AuNPs were combined effectively. Uniform and orderly multilayers ofPDDA-G/MPA@AuNPs/CuHCF/(MPA/CuHCF)4was obtained through LBL method.The Prussian blue sensor can be used to detect hydrazine with high sensitivity, whichprovided a linear response from0.4to130μM with a detection limit of72nM.The thesis studied the fabrication and application of PEI-Fc-G/antibody(HRP-Ab) immunosensor. Concanavalin A (Con A) and HRP-Ab were LBLassembled on the PEI-Fc-G modified electrode by means of biological affinityfunction. Fc from the PEI-Fc-G served as the immobilized electrochemical probe, andthis platform displayed an excellent sensitivity for label-free detecting ofcarcinoembryonic antigen (CEA). The immunosensor exhibited good reversibility andexcellent stability according to the cyclic voltammetry. A linear relationship betweenthe differential pulse voltammetry peak current change and the concentration of CEAin the range of0.1-10.0ng/mL and10.0-180.0ng/mL with a detection limit of0.04ng/mL was obtained. The immunosensor achieved direct, simple and rapiddetermination of CEA, and showed great promise in practical sample testing.