An Ethanol Biosensor Based on Simple Immobilization of Alcohol Dehydrogenase on Fe3O4"Au Nanoparticles

Abstract

An ethanol biosensor based on alcohol dehydrogenase (ADH) attached to Au seeds decorated on magnetic nanoparticles (Fe3O4"Au NPs) is presented. ADH was immobilized on Fe3O4"Au NPs, which were subsequently fixed by a magnet on a carbon paste electrode modified with 5% (m:m) MnO2. Optimum conditions for the amperometric determination of ethanol with the biosensor were as follows: working potential +0.1 V (vs. Ag/AgCl); supporting electrolyte: 0.1 M phosphate buffer solution at pH 6.8 containing 0.25 mM of the coenzyme (NAD+); working electrode: carbon paste with magnetically attached Fe3O4"Au NPs (0.012 mg . cm(-2) electrode area) with immobilized alcohol dehydrogenase (120 units per cm(2) of electrode area). Linearity between signal and concentration was found for the range from 0.1 to 2.0 M ethanol (r(2) = 0.995) with a detection limit of 0.07 M, a sensitivity of 0.02 mu A . mM(-1) . cm(-2), a reproducibility of 4.0% RSD, and a repeatability of 2.7% RSD. The results for the determination of ethanol in alcoholic beverages showed good agreement with gas chromatography (GC) with recovery of 96.0-108.8%.