NADH detection

NADH. Immobilized redox mediators, such as the phenoxazine Meldola Blue or phenothiazine compoimds, have been particularly useful for this purpose (20) (see also Figure 4-12). Such mediation should be useful for many other dehydrogenase-based biosensors. High sensitivity and speed are indicated from the flow-injection response of Figure 3-21. The challenges of NADH detection and the development of dehydrogenase biosensors have been reviewed (21). Alcohol biosensing can also be accomplished in the presence of alcohol oxidase, based on measurements of the liberated peroxide product. 

M. Musameh, J. Wang, A. Merkoci, and Y. Lin, Low-potential stable NADH detection at carbon-nanotube-modified glassy carbon electrode. Electrochem. Common. 4, 743-746 (2002). 

Suaud-Chagny and Goup (1986) immobilized LDH on a pyrolytic carbon fiber microelectrode by impregnation in an inert protein sheath that was first electrochemically deposited around the active tip of the electrode. The NADH detection was improved by electrochemical treatment of the electrode. The detection limit for pyruvate was lower than 1 pmolA. The sensor was used to estimate pyruvate concentration in rat cerebrospinal fluid. 

PoPD deposited onto GCE, pre-modified with MWCNT, is also used for determination of / -nicotinamide adenine dinucleotide [NADH] [58], The main problem in NADH detection on bare GCE is the considerable overpotential (>1 V] causing fouling of the electrode. PoPD-MWCNT decreased the oxidation potential of NADH allowing the amperometric detection of j8-nicotinamide at 0.07 V. 

Banks, C.E. and Compton, R.G. (2005) Exploring the electrocatalytic sites of carbon nanotubes for NADH detection an edge plane pyrolytic graphite electrode study. Analyst, 130 (9), 1232-1239. 

A drastic oxidation of carbon electrodes will introduce in a rather unselective way, oxygen-containing functionalities on its surface [90,132-137,172, 381-383]. Base-pretreated GC electrodes have been used to decrease the overpotential to around 350 mV, allowing LC-EC detection at 0.5 V versus Ag/AgCl with NADH limit of detection in the order of fmol [173]. Carbon-fiber microelectrodes, after electrochemical pretreatment [101-105,175], have been used for NADH detection using fast scan (100 V/s) conditions to discriminate between NADH and other compounds that are also oxidized. The long-term stability of the pretreated carbon electrode surface is, however, far from great. 

Agboola et al. [57] reported the utilization of phenylamine-modified SWCNTs integrated with cobalt(II) octa[(3,5-biscarboxylate)-phenoxy] phthalocyanine (CoOBPPc) for (5-nicotinamide adenine dinucleotide (NADH) detection (Fig. 10a). The sensor showed good ability to detect low concentrations of NADH even in the presence of high concentration of ascorbic acid, which frequently interferes in the electrochemical determination of this analyte. Comparative cyclic voltammograms at bare GC and CNTs-modified electrode can be seen in Fig. 10b. 

Musameh, M., Wang, J., Merkoci, A. et al. 2002. Low-potential stable NADH detection at carbon-nanotube-modifled glassy carbon electrodes. Electrochem. Commun. 4 743-746. 

Harper JC, Polsky R, Dirk SM, Wheeler DR, Brozik SM (2007) Electroaddressable selective functionalization of electrode arrays catalytic NADH detection using aryl diazonium modified gold electrodes. Electroanalysis 19 1268-1274... 

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