Direct Electrochemistry of Catalase at a Gold Electrode Modified with Single-Wall Carbon Nanotubes

The direct electrochemistry of catalase (Ct) was accomplished at a gold electrode modified with single-wall carbon nanotubes (SWNTs). A pair of well-defined redox peaks was obtained for Ct with the reduction peak potential at 0.414 Vand a peak potential separation of 32 mVat pH 5.9. Both reflectance FT-IR spectra and the dependence of the reduction peak current on the scan rate revealed that Ct adsorbed onto the SWNT surfaces. The redox wave corresponds to the Fe(III)/Fe(II) redox center of the heme group of the Ct adsorbate. Compared to other types of carbonaceous electrode materials (e.g., graphite and carbon soot), the electron transfer rate of Ct redox reaction was greatly enhanced at the SWNT-modified electrode. The peak current was found to increase linearly with the Ct concentration in the range of 8 10 6 ± 8 10 5 M used for the electrode preparation and the peak potential was shown to be pH dependent. The catalytic activity of Ct adsorbates at the SWNTs appears to be retained, as the addition of H2O2 produced a characteristic catalytic redox wave. This work demonstrates that direct electrochemistry of redox-active biomacromolecules such as metalloenzymes can be improved through the use of carbon nanotubes.