Signal Amplification in Enzyme-Based Amperometric Biosensors

A unique mode of current amplification was investigated in reagentless biosensors based on the clinically significant enzymes including alcohol dehydrogenase, glucose 6-phosphate dehydrogenase, glycerol 3-phosphate dehydrogenase, and glucose oxidase. The biosensors were designed by sandwiching the enzyme–polymer film between an electrode and Nafion film. In particular, each enzyme and its cofactor were covalently attached to the chains of polysaccharide chitosan and mixed with carbon nanotubes on the electrode surface. The coating of such biosensors with Nafion resulted in the current increase by up to 1000%, depending on the enzyme. The results were analyzed considering the interplay between the enzyme activity–pH profiles and the Nafion-induced pH increase in the underlying chitosan film. The data were collected by using the rapid (