Glucose Oxidase-graphene-chitosan modified electrode for direct electrochemistry and glucose sensing

Direct electrochemistry of a glucose oxidase (GOD)-graphene-chitosan nanocomposite was studied. The immobilized enzyme retains its bioactivity, exhibits a surface confined, reversible two-proton and two-electron transfer reaction, and has good stability, activity and a fast heterogeneous electron transfer rate with the rate constant (k(s)) of 2.83 s(-1). A much higher enzyme loading (1.12 x 10(-9) mol/cm(2)) is obtained as compared to the bare glass carbon surface. This GOD-graphene-chitosan nanocomposite film can be used for sensitive detection of glucose. The biosensor exhibits a wider linearity range from 0.08 mM to 12 mM glucose with a detection limit of 0.02 mM and much higher sensitivity (37.93 mu A mM(-1) cm(-2)) as compared with other nanostructured supports. The excellent performance of the biosensor is attributed to large surface-to-volume ratio and high conductivity of graphene, and good biocompatibility of chitosan, which enhances the enzyme absorption and promotes direct electron transfer between redox enzymes and the surface of electrodes. (C) 2009 Elsevier B.V. All rights reserved.