Electroreduction of Hydrogen Peroxide Using Direct Electrocatalysis of Cytochrome c on a Graphene-Modified Electrode

In the mitochondrial intermembrane space, the redox protein heme-Cytochrome c (Cyt c) acts as an electron carrier. The translocation of Cyt c out of mitochondria triggers programmed cell death. In this study, direct electrochemistry of Cyt c adsorbed onto the surface of a graphene-modified electrode was investigated. Owing to the high electron mobility of one-atom thick graphene, it serves as a unique platform for facilitating direct electron transfer of proteins. The redox peak currents of the Cyt c-immobilized graphene increased linearly with increasing the scan rate, revealing a surface-controlled electrochemical process. The enzyme-mimetic activity of the Cyt c-immobilized graphene in the electroreduction of H2O2, from 2.0 μM to 4.0 mM with a detection limit of 0.4 μM, demonstrated that the graphene maintained the bioactivity of Cyt c. This intriguing enzyme-liked catalytic activity makes the Cyt c-modified graphene electrode a suitable candidate for fabricating H2O2 sensors. This direct electron-based electroreduction opens a new horizon for highly sensitive targeted bioanalysis with a functional nanomaterial design.