Electrochemistry of Cytochrome c Immobilized on Colloidal Gold Modified Carbon Paste Electrodes and Its Electrocatalytic Activity

Colloidal gold modified carbon paste electrodes were prepared by mixing 24-nm-diameter colloidal Au particles with carbon paste. The modified electrodes displayed a low charging current and a favorable electrochemical response of hexacyanoferrate (III). The direct electrochemical behavior of a horse-heart cytochrome c (cyt.c) adsorbed on this electrode surface is described. It showed a surface-controlled electrode process with the electron transfer rate constant of (1.21±0.08) s−1 and α of 0.67. Cyclic voltammograms showed small peak-to-peak separations at low scan rates. The adsorbed cyt.c maintained its activity and could also electrocatalyze the reduction of hydrogen peroxide. Since this behavior was quite pronounced the electrode was used for H2O2 detection. The KMapp value for this sensor was found to be 2.28±0.17 mM, allowing measurements down to 0.01 mM H2O2.