A H2O2 biosensor based on immobilization of horseradish peroxidase in electropolymerized methylene green film on GCE

A novel H2O2 sensor is achieved by immobilizing horseradish peroxidase (HRP) in an electropolymerized methylene green (PMG) redox film. The electropolymerization of MG is carried out in a neutral phosphate buffer solution with 5x10(-5) M methylene green (MG) by using a two-step method. The polymer film only occurs on glassy carbon (electrodes and the reason for this is identified. The critical factor for the electropolymerization of MG lies in the preanodization on a glassy carbon) electrode, because a large amount of positive charges are accumulated and used to create the cation radicals form the polymer film. The formal potentials of PMG is pH dependent with a slope of 57 mV per pH unit between pH 6.0 and 8.0, which is close to the anticipated Nernstian value of 59 mV for a two-electron, two-proton process. The PMG itself and the PMG on the H2O2 sensor show electrochemical behaviour with a linear plot of peak current against scan rate in the range 20 to 100 mV s(-1).