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

Abstract

Abstract An ethanol biosensor based on alcohol dehydrogenase (ADH) attached to Au seeds decorated on magnetic nanoparticles (Fe 3 O 4 @Au NPs) is presented. ADH was immobilized on Fe 3 O 4 @Au NPs, which were subsequently fixed by a magnet on a carbon paste electrode modified with 5 % (m : m) MnO 2 . 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 Fe 3 O 4 @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 µA ⋅ 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 %.