Bioelectrocatalysis by Microperoxidase-11 in a multilayer architecture of chitosan embedded gold nanoparticles

We report on the redox behaviour of the microperoxidase-11 (MP-11) which has been electrostatically immobilized in a matrix of chitosan-embedded gold nanoparticles on the surface of a glassy carbon electrode. MP-11 contains a covalently bound heme c as the redox active group that exchanges electrons with the electrode via the gold nanoparticles. Electroactive surface concentration of MP-11 at high scan rate is between 350±50pmol cm-2, which reflects a multilayer process. The formal potential (E°') of MP-11 in the gold nanoparticles-chitosan film was estimated to be -(267.7±2.9) mV at pH7.0. The heterogeneous electron transfer rate constant (ks) starts at 1.21s-1 and levels off at 6.45s-1 in the scan rate range from 0.1 to 2.0V s-1. Oxidation and reduction of MP-11 by hydrogen peroxide and superoxide, respectively have been coupled to the direct electron transfer of MP-11.