Electrochemical Biosensors Of Galactose Oxidase Based On Graphene Composite Film

Graphene has aroused wide concern since first reported in 2004. It is a new type of two dimension carbon nanomaterial and has become an ideal material for electrode modification widely used in the study on electrochemical sensor due to its high surface area, good conductivity and so on. Galactose oxidase(GAO) is a copper-oxidase which can oxidise alcohols to corresponding aldehydes. However, direct electron transfer between enzyme and the electrode is difficult to occur because the centre electrical activity of GAO is buried in its huge structure. In this paper graphene and polymer nano composites were used to immobilize galactose oxidase to form enzyme-based electrochemical biosensor which provided favorable microenviroments for GAO so that the enzyme retained its biological activity. The electrochemical biosensors realized direct electron transfer between the electrode and enzyme and had good electrocatalytic behaviors to the corresponding substrate. The main works of this paper are summarized below:(1) Polyvinyl alcohol functionalized graphene oxide(GO-PVA) was synthesized to immobilize galactose oxide for the first time. The film was characterized by scanning electron microscope(SEM) and electrochemical impedance spectroscopy(EIS). Direct electrochemical behavior of this modified electrode was examined and the influence of buffer solution’s PH value and the influence of sweep rate were also studied. GAO in the composite film realized its direct electrochemistry and the biosensor exhibited excellent bioelectrocatalytic activity toward galactose and DHA with wide linear range and low detection limit. Also, the biosensor exhibited good reproducibility and stability.(2) A composite film was developed by poly(L-lactide) stabilized gold nanoparticles(Au@PLLA) to modify reduced grapheme oxide. Galactose oxidase(GAO) was the first time immobilized in this composite film. The direct electron transfer of GAO was achieved by cyclic voltammetry and amperometric response was used as a function for determination of galactose and dihydroxyacetone(DHA). The developed biosensor exhibited excellent bioelectrocatalytic activity to galactose and DHA, the limit of detection was 0.79 μM(S/N = 3).(3) A graphene oxide(GO)- poly(ethylene) glycol diglycidyl ether(PEGDGE) composite film was fabricated, and a novel galactose biosensor based on GO-PEGDGE composite film was developed. Scanning electron microscopy(SEM) and electrochemical impedance spectroscopy(EIS) were used to characterize the GO-PEGDGE/GAO film. The direct electrochemistry of GAO in GO-PEGDGE composite film has been studied in pH 7.0 phosphate buffer solution by cyclic voltammetry. The results indicated that GAO was successfully immobilized on the film and a pair of well-defined and quasi-reversible redox peak were observed. The modified electrode showed execellent bioelectrocatalysis activity toward galactose.