RESUMEN

Various strategies based on the use of chemically modified electrodes for the development of amperometric biosensors are described. Particular emphasis is placed on materials capable of catalyzing the oxidation of NADH and coupling these with enzymatic activities for biosensor construction. In terms of electrocatalysts, the discussion will centre on electrodeposited films of 3,4-dihydroxy benzaldehyde (3,4-DHB) and related analogs as well as on electrodeposited films of transition metal complexes of 1,10-phenanthroline-5,6-dione (phen-dione). Electrodeposited films of these materials have been coupled to the enzymatic activity of aldehyde dehydrogenase and alcohol dehydrogenase for the development of biosensors for aldehydes and ethanol, respectively.

Asunto(s)

Técnicas Biosensibles , Electrodos , NAD/química , Alcohol Deshidrogenasa , Aldehído Deshidrogenasa , Ácido Ascórbico , Benzaldehídos , Carbono , Catálisis , Catecoles , Electroquímica , Concentración de Iones de Hidrógeno , Oxidación-Reducción , Fenantrolinas , Reproducibilidad de los Resultados , Soluciones

RESUMEN

Studies of the electrocatalytic oxidation of ß-nicotinamide adenine dinucleotide (NADH) at glassy carbon rotated disk electrodes modified with electrodeposited films derived from 3,4-dihydroxybenzaldehyde (3,4-DHB) indicate that the mechanism of such electrooxidation proceeds via the formation of an intermediate complex. The reaction also appears to be strongly influenced by the presence of Ca(2+) and Mg(2+) ions as well as by pH. Ascorbate can also be electrocatalytically oxidized at these modified electrodes, giving rise to an electrochemical response very similar to that obtained for NADH. Due to this similarity, the presence of ascorbate in NADH determinations presents a severe interference that cannot be mitigated on the basis of electrochemical responses alone. However, this interference effect can be virtually suppressed by the presence of ascorbate oxidase in solution or immobilized on a nylon mesh which, in turn, is in contact with the electrode modified with the film of 3,4-DHB. Using this approach, we describe the construction of an alcohol biosensor based on alcohol dehydrogenase and which is, furthermore, free from interference effects due to ascorbate.