Renewable reagentless hydrogen peroxide sensor based on direct electron transfer of horseradish peroxidase immobilized on colloidal gold-modified electrode

A novel renewable reagentless hydrogen peroxide (H2O2) sensor based on the direct electron transfer of horseradish peroxidase (HRP) is proposed. The direct electrochemistry of HRP immobilized on a colloidal gold-modified carbon paste electrode (Au-CPE) was investigated using electrochemical methods. The immobilized HRP displayed a pair of redox peaks in 0.1 M phosphate buffer (PB), pH 7.0, with a formal potential of -0.346V. The response showed a surface-controlled electrode process with an electron transfer rate constant of 6.04 +/- 0.18 s(-1) determined in the scan rate range from 120 to 500 mV/s. The biosensor displayed an excellent electrocatalytic response to the reduction of H2O2 without the aid of an electron mediator. The sensor surface could be renewed quickly and reproducibly by a simple polish step. The calibration range of H2O2 was 0-0.3 mM with linear relation from 0.48 to 50 muM and a detection limit of 0.21 muM at 3sigma. The response showed Michaelis-Menten behavior at higher H2O2 concentrations. The K-M(app) value of HRP at HRP-Au-CPE was determined to be 3.69 +/- 0.71 mM. (C) 2002 Elsevier Science (USA). All rights reserved.