4-ferrocenylphenol as an electron transfer mediator in PQQ-dependent alcohol and glucose dehydrogenase-catalyzed reactions

Enzyme electrodes containing pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase (ADH) and glucose dehydrogenase (GDH) as a biological component in combination with 4-ferrocenylphenol (I) as an electron transfer mediator between PQQ and a carbon electrode were constructed and used for measurements of ethanol and D-glucose. Analysis of the current response of the carbon electrodes modified with 1 at different pH and potentials demonstrated that 1 participates in the bioelectrocatalytic oxidation of D-glucose or ethanol. The biosensors showed the highest response at pH 5.5 and the working potentials of 0.3 and 0.4 V (versus Ag \AgCl) for ADH and GDH, respectively. The electrocatalytic processes under such conditions at these electrodes are characterized by the apparent values of the Michaelis constants K-M(app) of 7.1 and 13 mM and the maximal current density j(max) 40 and 26 mu A cm(-2) for ethanol and D-glucose, respectively. No electrocatalysis was found when glucose oxidase from Aspergillus niger was used instead of GDH. (C) 2000 Elsevier Science S.A. All rights reserved.