Gold electrodes were functionalized with an electropolymerized matrix of Au nanoparticles modified with 2-mercaptoethanesulfonic acid. 3-mercaptophenyl boronic acid and p-aminothiophenol. The resulting nanostructured electroconductive matrix was used as support for the oriented immobilization of horseradish peroxidase to construct a reagentless amperometric biosensor for H2O2. The electrode, poised at 0.0 mV, exhibited a rapid response within 8 s and a linear calibration range from 5 mu M to 1.1 mM H2O2. The sensitivity of the biosensor was determined as 498 mu A/M cm(2). and its detection limit was 1.5 mu M H2O2 at a signal-to-noise ratio of 3. The electrode retained 95% and 72% of its initial activity after 21 and 40 days of storage at 4 degrees C. (C) 2011 Elsevier Ltd. All rights reserved.