Highly stable amplified low-potential electrocatalytic detection of NAD+ at azure-chitosan modified carbon electrodes

The incorporation of chitosan (CHIT) into an Azure-C (AZU) film, covering a glassy carbon electrode, greatly facilitates the electroreduction of NAD(+) to allow a highly stable low-potential amplified cathodic detection of this enzymatic cofactor. Higher and sharper NAD(+) reduction peaks are thus observed at lower potentials at the AZU/CHIT coated electrode, compared to those observed at the AZU-modified electrode. Such formation of an AZU/CHIT surface layer leads also to a highly stable NAD(+) response. For example, 98% of the initial amperometric response of NAD(+) at the AZU/CHIT coated electrode is retained after 20 min stirring 6 x 10(-3) M NAD(+) solution (compared to 69% at the AZU-modified electrode). Factors affecting the enhanced electrocatalytic response, including the composition of the AZU/CHIT layer or pH, are examined. Electrochemical parameters for the NAD(+) reduction, including the alpha, k or E-0', are estimated by cyclic voltammetry. The improved NAD(+) detection of NAD(+) reflects the improved film formation imparted by the CHIT component. The new modified electrode could find a wide range of biotechnological applications, including biosensors, bioreactors and biofuel cells. (c) 2006 Elsevier B.V. All rights reserved.