Electron transfer from diamond electrodes to heme peptide and peroxidase

Direct electron transfer from boron-doped diamond electrodes to heme undeca peptide and horseradish peroxidase (HRP) was examined and evaluated for the application to H2O2 biosensors. As-grown and oxygen plasma-treated diamond electrodes on which heme peptide is adsorbed exhibited cathodic current re sponses to H2O2 on the basis of the direct electron transfer. In a comparat ive study of carbon electrodes on which heme peptide was adsorbed, an oxyge n plasma-treated diamond electrode exhibited responses comparable with thos e of an edge-oriented pyrolytic graphite (EOPG) electrode, despite much sma ller roughness. However, electron transfer to compounds I and II of HRP fro m the diamond electrodes was much slower than that from EOPG or glassy carb on, suggesting that the pi electrons of an sp(2) carbon may play an importa nt role in the direct electron transfer to the heme moiety of HRP, To exami ne the applicability of heme peptide-modified diamond electrodes to oxidase -based biosensors, anodic current responses of the oxygen plasma-treated di amond electrode to possible interfering agents, ascorbic acid and uric acid , were examined and compared with those of EOPG. Since the diamond electrod e exhibited much less sensitivity to those interfering agents, the heme pep tide-modified diamond electrode should be a promising H2O2 biosensor for th e application to oxidase-based biosensors.