Electrodeposition of Redox-Active Films of Dihydroxybenzaldehydes and Related Analogs and Their Electrocatalytic Activity toward NADH Oxidation

Abstract

Dihydroxybenzaldehyde (DHB) isomers can be oxidatively electrodeposited onto glassy carbon electrodes previously activated in base solution. We have studied the mechanism of such electrodeposition as well as the electrochemical features of films derived from 2,3-DHB, 3,4-DHB, 2,5-DHB, and 2,4-DHB isomers as well as related analogs including 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, and 4-nitrocatechol. The electrodeposition process and the electrochemical behavior of the modified electrodes were strongly dependent on pH as anticipated for quinone/hydroquinone functionalities. Glassy carbon electrodes modified with films derived from 2,3-DHB and 3,4-DHB exhibit catalytic activity in the electrooxidation of NADH. The catalytic currents are proportional to the concentration of NADH over the range 0.01−1.2 and 0.01−0.9 mM for films derived from 3,4-DHB and 2,3-DHB, respectively. These modified electrodes can be used in the design of biosensors based on coupled dehydrogenase enzymatic activities.

Mechanism of 3,4-dihydroxybenzaldehyde electropolymerization at carbon paste electrodes: catalytic detection of NADH

“…At pH values between 2.6 and 7.8 the anodic and cathodic peak potentials for the reversible pair changed linearly with pH 37,40,48 , according to the equations: E p,a1 = 0.65 -0.064 pH (r 2 = 0.9995) and E p,c1 = 0.61 -0.064 pH (r 2 = 0.9997 ). During successive cycles in supporting electrolyte, the current peaks decreased, probably due to film inactivation as consequence of secondary reactions or desorption of species weakly bound to the electrode surface.…”

“…However, in our work the peak potential did not change upon increasing scan rate up to 100 mVs -1 . Additional studies have been done 40,44 and the oxidation of 3,4-DHB to the correspondent quinone, with a subsequent nucleophilic attack from active functional groups from the electrode surface, was then considered.…”

“…Several studies on electrocatalytic oxidation of NADH using chemically modified electrodes were reported since early 80's . Modified electrodes with 3,4-dihydroxybenzaldehyde and related analogs have been described [37][38][39][40]42 and used to develop new 39,[42][43][44] aldehyde and alcohol biosensors. The best procedure to prepare modified electrodes was using constant applied potentials 37,39,43 .…”

“…The best procedure to prepare modified electrodes was using constant applied potentials 37,39,43 . Mechanisms for 3,4-DHB electropolymerization processes involving phenoxyl radical formation with further dimerization process on the electrode surface 37 , oxidation to the correspondent quinone with subsequent nucleophil-c attack from active functional groups on the electrode surface 40,44 and chain propagation of 3,4-DHB through the aldehyde functionality 45 have been proposed, but they do not suggest possible pathways for electropolymerization processes and film growing. Additionally, the appearance of a reversible redox pair at potentials lower than those necessary to oxidize 3,4-DHB molecules is still unknown.…”

Immobilized redox mediators for electrochemical NAD(P)+ regeneration

“…Mediated oxidation of NADH can be accomplished with a large number of compounds such as metal complexes (Hilt et al 1997;Hilt and Steckhan 1993), quinones (Ciszewski and Milczarek 2000;Ghanem et al 2009;Pariente et al 1996;Prieto-Simón et al 2007), fluorenones (Mano and Kuhn 1999b;Mano et al 2001;Munteanu et al 2002), phenazines (Arechederra et al 2011;Curulli et al 1997;Lu et al 2010), phenoxazine (Lobo et al 1996), and phenothiazines (Lobo et al 1996). Furthermore, conducting polymers (Bartlett et al 1997;Toh et al 2003) and selfassembled monolayers (SAM; Barzegar et al 2009;Ju et al 2002) can be used as catalysts.…”