Hydorgen Peroxide Biosensor Based on Direct Electrochemistry of Hemin in Egg-Phosphatidylcholine Films

The mixture of egg-PC vesicles and hemin was casted onto indium-tin oxide glass (ITO) electrode. The hemin showed a direct electrochemical behavior on the modified electrode. A well-defined pair of redox peaks was obtained from the cyclic voltammograms at ITO electrode modified by the mixture of hemin and egg-phosphatidylcholine (egg-PC). The average value of the surface coverage of electroactive hemin, Gamma, was 3.25 x 10(-12) mol cm(-2). The formal potential (E-o') of hemin in the lipid film was linearly varied with the pH of phosphate buffer solution in the range from 4.0 to 9.0 with a slope of -43.7 mV/pH. The pH value of buffer solution for measuring hydrogen peroxide was decided to be 4.0. The linear range of the biosensor was from 10 mu M to 200 mu M with a detection limit of 5 mu M. The modified electrode exhibited a good catalytic activity towards hydrogen peroxide. Therefore a third generation biosensor was developed.