An Organically Modified Silicate-Based Ethanol Biosensor

Abstract

A novel electrocatalytic ethanol biosensor using ferrocene-encapsulated palladium (Pd)-linked organically modified sol–gel glass (ormosil) is reported. The alkoxy precursors used to prepare the new ormosil-based electrocatalytic biosensor are Pd-linked glycidoxypropyltrimethoxysilane and trimethoxysilane. Pd-glycidoxypropyltrimethoxysilane (black solution) is made by mixing aqueous solutions of palladium chloride and glycidoxypropyltrimethoxysilane. The new ormosil is made using a Pd-linked silane precursor, trimethoxysilane, an aqueous solution of ferrocene monocarboxylic acid, and HCl. Alcohol dehydrogenase (ADH) is assembled over the ferrocene–ormosil layer using polyvinyl alcohol and then protecting the immobilized enzyme layer using Millipore filter membranes (pore size 1 μm). The electrocatalytic response of immobilized ADH, soluble nicotinamide adenine dinucleotide, and Pd-linked ormosil-encapsulated ferrocene is then observed. The electrocatalytic oxidation of NADH and the subsequent ADH-catalyzed formation of NADH are monitored electrochemically. Typical results recorded after the addition of varying concentrations of ethanol are reported; however, the sensor is sensitive to other alcohol and known ADH-sensitive substrates. The stability and reproducibility of the new ethanol biosensor are reported.