A novel ITO electrode surface modified with spherical and rod-shaped gold nanoparticles was prepared by a surfactant-assisted seeding growth approach, which provided a biocompatible matrix for the immobilization of hemoglobin (Hb). By electrochemical impedance measurements, gold nanoparticles modification and Hb immobilization on the electrode surfaces were characterized using [Fe(CN)(6)](3-)/[Fe(CN)(6)](4-) redox probe. Owing to the promoted electron transfer of Hb by gold nanoparticles, the Hb immobilized gold nanoparticles-modified ITO (Hb/Au/ITO) electrode exhibited an effective catalytic response to the reduction of H2O2 with good reproducibility and stability. The linear relationship existed between the catalytic current and the H2O2 concentration in the range of 1 x 10(-5) to 7 x 10(-3) M. The detection limit (S/N = 3) was 4.5 x 10(-6) M. (C) 2004 Elsevier Ltd. All rights reserved.