Enzymatic biosensor based on carbon paste electrodes modified with gold nanoparticles and polyphenol oxidase

The results presented here demonstrate the important catalytic effect of a carbon paste electrode modified by dispersion of gold nanoparticles towards different electroactive compounds. The oxidation of hydrogen peroxide starts at potentials 400 mV less positive than at bare carbon paste, while the reduction, almost negligible at bare carbon paste, starts at 0.100 V. The influence of the size and amount of gold nanoparticles in the composite matrix on the response of the electrode is discussed. The incorporation of albumin within the carbon paste facilitates the dispersion of gold nanoparticles, improving substantially the catalytic effects. At carbon paste modified with gold nanoparticles and albumin, the peak potential separation for hydroquinone decreases from 0.385 V to 0.209 V while the reduction current increases from 16.6 to 75.2 mu A. The immobilization of polyphenol oxidase within the carbon paste electrode modified with nanoparticles has allowed us to obtain a very sensitive biosensor for dopamine even in the presence of large excess of ascorbic acid.