Sol-Gel-Encapsulated Alcohol Dehydrogenase as a Versatile, Environmentally Stabilized Sensor for Alcohols and Aldehydes

Silicate-encapsulated yeast alcohol dehydrogenase (ADH) can be employed as a sensor for shortchained alcohols in standard aqueous, harsh nonaqueous, and gas-phase environments. Specifically, the implementation of sensing schemes based on encapsulated ADH/NAD+ or ADH/NADH, and utilization of changes in fluorescence from the soluble, reduced cofactor nicotinamide adenine dinucleotide (NADH) upon exposure to alcohols or aldehydes, allows for semiquantitative determination of both substrates. Additionally, by using fluorescence from NADH, we find that cycling of the enzymatic probe can be accomplished via successive exposure to alcohol and aldehyde substrates, thus converting the system into a multiple-use sensor. Finally, we find that the gel matrix provides sufficient enzyme stabilization to permit the assemblies to be used analytically in hostile and inherently denaturing sample environments, including vapor-phase and nonpolar liquid (e.g., hexane) environments.