Electrochemical Biosensors Based On The Polymer Functionalized Graphene

Recently, the development of electrochemical research for investigations ofprotein structure, mechanisms of redox transformation of protein molecules, andmetabolic processes involving redox transformations has been attracted more andmore attention. Understanding of these reactions fundamentally can provide theinsight into physiological electron transfer process as well as an impetus to the furtherdevelopment of biosensors and bioelectrocatalytical systems. This paper mainly focusachieving the direct electrochemistry and electrocatalysis of glucose oxidase andhemoglobin. Several kinds of biocompatible cellulose derivatives functionalizedreduce graphenen oxide (rGO) were synthesized and then apllied for theimmobilization of hemoglobin or glucose oxidase. These composite materials notonly can promote the direct electron transfer between hemoglobin or glucose oxidaseand electrode, but also can provide favourable microenvironment to realize theirdirect electrochemistry and electrocatalysis. In this paper, the main works weresummarized as follows:(1) Carboxymethyl cellulose functionalized graphene was synthesized by asimple and friendly method, and constructed a novel carboxymethyl cellulose (CMC)functionalizde reduce graphenen oxide (rGO-CMC)-based biosensor was developed.Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used tocharacterize the rGO-CMC/Hb film. The direct electrochemistry of rGO-CMC/Hbmodify electrodes were investigated by cyclic voltammetry. The results indicated thatHb remained it’s bioactivity on the modified electrode and showed a couple ofwell-defined and quasi-reversible redox peaks. The immobilized Hb exhibitedexcellent bioelectrocatalytic activity toward NO and H2O2reduction.(2) A stable, biocompatible functionalized reduce graphenen oxide nanosheets(GR-QC) with quaternized cellulose were synthesized. It was used as animmobilization matrix to entrap hemoglobin (Hb) firstly. The direct electrochemistryHb in GR-QC composite film was studied. A pair of well-defined and quasi-reversibleredox peaks were observed and the formal potential was about-0.331V in pH7.0phosphate buffer solution. The immobilized Hb showed excellent bioelectrocatalysisin the reduction of nitric oxide (NO) and hydrogen peroxide (H2O2). The GR-QC/Hbmodified electrode exhibited good reproducibility, long-term stability and high sensibility. In addition the biosensor has been applied to monitoring the NO releasefrom biologic samples.(3) Quaternized cellulose nano-gold functionalized reduce graphenen oxide(rGO-Au@QC) was synthesized. Because of the composite material with highconductivity and good biocompatible, it was used to immobilize glucose oxidase.Au@QC can provides favourable microenvironment for glucose oxidase and rGOplays role in promoting the direct electron transfer. The immobilized GOD showedexcellent bioelectrocatalysis in the reduction of glucose. The results showed that thebiosensor with good stability, repeatability, wide linear range and low detection limit.