Electron Transfer of Co-immobilized Cytochrome c and Horseradish Peroxidase in Chitosan-Graphene Oxide Modified Electrode

Cytochrome c (Cyt c ) and horseradish peroxidase (HRP) were co-immobilized on graphene oxide (GO)-chitosan (CHIT) modified Au electrode and the electron-transfer between the two proteins was investigated. The GO-CHIT nanocomposite was assembled on an Au electrode which covered by a mixed self-assembled monolayer of mecraptoundecanoic acid (MUA) and 6-mercapto-1-hexanol (MCH) and coated with Cyt c . The GO-CHIT nanocomposite as a novel electrochemical platform designed by combining the biocompatibility of CHIT and the conductivity of GO was used for the immobilization of the redox enzymes. Based on electrostatic interactions, the Cyt c -HRP/GO-CHIT/Cyt c /MUA-MCH/Au electrode was constructed by a layer-by-layer technique. Electron transfer and electrocatalytic performances of the modified electrode were investigated. Results showed that direct electron transfer has been established for the bi-protein system and the average rate constant of electron transfer k s , (Cyt c - HRP) =2.63 s -1 was larger than those values at the electrodes modified with single protein (k s , (Cyt c ) =1.44 s -1 , ks, (HRP) =1.53 s-1). The bi-protein modified electrode exhibited good electrocatalytic response to reduction of oxygen (O 2 ) and hydrogen peroxide (H 2 O 2 ), suggesting that a third-generation biosensor could be obtained for the detection of O 2 and H 2 O 2 .