Modification of Macroporous Electrodes: A Spectroscopic and Bioelectrochemical Study

Samia Ben Ali 1,  Bernard Desbat 3,  D. A. Cook 2,  P. N. Bartlett 2,  Alexander Kuhn 1

1. Laboratoire d'Analyse Chimique par Reconnaissance Moléculaire, Ecole Nationale Supérieure de Chimie et de Physique de Bordeaux (LACReM), 16 Avenue Pey Berland, Pessac 33607, France
2. University of Southampton, Department of Chemistry, Southampton SO17 1BJ, United Kingdom
3. Laboratoire de Pysicochimie Moléculaire - Université Bordeaux I, 351 Cours de la Libération, Talence 33405, France

Abstract

The performance of the enzyme based biosensors depends on many parameters, in particular on the enzyme activity. Our approach consists in layer-by-layer building of a dehydrogenase biosensor using electrostatic interactions in order to prevent damaging of the enzyme by direct interactions with the electrode. In order to increase the sensitivity and stability of the sensors, organised porous metal structures has been used as electrode substrates [1].
Our attention is focused on one particular mediator family based on a skeleton of nitrofluorenone, i.e., (2,4,7-trinitro-9-fluorenylidene)-malonitrile, (TNFM), which adsorbs on the surface of gold electrodes and exhibits appreciable electrocatalytic activity towards NADH (nicotinamide adenine dinucleotide) oxidation [2, 3]. The adsorption of this molecule has been studied by cyclic voltammetry and surface infrared spectroscopy in order to elucidate the detailed mechanism of the molecule-surface and mediator-NADH interactions. These studies suggest that the monolayer of redox mediator is irreversibly bound to the gold surface via the CN groups when the electrode is exposed to negative potentials in order to transform one ore more nitro groups into the catalytically active NO/NHOH couple. Electrochemical results show that macroporous electrodes can be modified with the redox mediator on their entire inner surface. Therefore, the amount of the adsorbed mediator directly depends on the surface area of the electrode and the total inner surface is also accessible for the catalytic NADH oxidation. The currents can be further enhanced by adding Ca2+ ions to the solution and the produced NAD+ seems to be enzymatically active [4].

References
[1] S.A.G. Evans, J.M.Elliott, L. M. Andrews, P.N. Bartlett, P. J. Doyle, and G. Denault, Anal. Chem. 74, 1322-1326, (2002).
[2] N. Mano and A. Kuhn, Electroanal. Chem., 477, 79-88, (1999).
[3] N. Mano and A. Kuhn, Biosensors & Bioelectronics, 16, 653-660, (2001).
[4] S. Ben Ali, D.A. Cook, A. Thienpont, P.N. Bartlett and A. Kuhn. Electrochem. Commun., 5, 747-751, (2003).

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Presentation: Short communication at SMCBS 2003 Workshop, by Samia Ben Ali
See On-line Journal of SMCBS 2003 Workshop

Submitted: 2003-10-08 18:29
Revised:   2009-06-08 12:55
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