Hydrogen peroxide biosensor based on direct electron transfer of horseradish peroxidase with vapor deposited quantum dots

Horseradish peroxidase (HRP) and lipophilic quantum dots (QDs) were incorporated onto the surface of glassy carbon (CC) electrodes in various ways. It was found that HRP transfers electron directly onto the CC electrode only when the electrode was modified with QDs through vapor deposition. The response currents were linearly correlated with scan rate, indicating that the reaction is a surface controlled process. The average coverage of HRP on the electrode surface can be calculated as 2.29 x 10(-11) mol cm(-2), and the heterogeneous electron transfer rate constant k was 5.80 +/- 0.70 s(-1). Absorption spectra and Fourier-transform infrared spectra showed that the conformation of HRP immobilized on the electrode has no obvious change. Further studies indicated that immobilized HRP retains excellent catalytic activity to H2O2. The apparent Michaelis-Menten constant was calculated as 0.152 mM. It was also found that the modified electrode could be used as a sensor for H2O2, and the linear range of detection was 5.0 x 10(-6) to 1.0 X 10(-4) M, with a detection limit of 2.84 x 10(-7) M. The sensor exhibited reproducibility, stability. (C) 2008 Elsevier B.V. All rights reserved.