Toward selectivity control of a heme peptide electrode by modification with a phase-transition polymer

Reduction currents for H2O2 at a heme peptide (HP)-modified electrodes are suppressed by inhibitors, such as imidazole derivatives. Although this inhibition effect allows determinations of the total inhibition ability of imidazole derivatives, it has no selectivity. In this study the selectivity control of HP-modified electrodes for imidazole derivatives was performed utilizing the thermoresponsive phase transition of poly(N-isopropylacrylamide), which was chemically immobilized on HP-modified electrodes. The inhibition ratios for imidazole derivatives appeared to be small at temperatures below the lower critical solution temperature (LCST), and to be large above the LCST. This change was ascribed to a steric hindrance caused by a phase transition of the polymer. On the other hand, the inhibition ratio for histamine, which has a larger molecular size relative to imidazole, was not significantly changed by the phase transition. Thus, the selectivity of the HP-modified electrode was found to be controllable using an immobilized phase-transition polymer.