Potentialities of expanded natural graphite as a new transducer for NAD+-dependent dehydrogenase amperometric biosensors

The present work deals with the use of the porous texture of expanded natural graphite (ENG) as transducer in order to design electrochemical biosensors. The sensing element is a NAD(+)-dependent dehydrogenase. An electrochemical pretreatment of the ENG is favorable because it allows on one hand generating functional surface groups that may act as mediators for NADH oxidation and, on the other hand, eliminating enzyme-toxic compounds. The electrocatalytic oxidation of NADH on the pretreated material leads to the formation of enzymatically active NAD(+). However, some persistent problems, mainly related to enzyme instability, still hamper the development of the biosensors. (C) 2003 Elsevier Science B.V. All rights reserved.