Diffusion-limited electrochemical D-fructose sensor based on direct electron transfer-type bioelectrocatalysis by a variant of D-fructose dehydrogenase at a porous gold microelectrode

Abstract

An electrochemical d-fructose sensor was fabricated by immobilizing a variant of d-fructose dehydrogenase on a porous gold microelectrode. The enzyme-modified electrode bioelectrocatalytically oxidizes d-fructose via direct electron transfer. The catalytic current reaches a steady-state limiting value at 0.05 V vs. Ag|AgCl (sat. KCl). The temperature dependence of the sensor suggests that its response is limited by the diffusion of d-fructose. Therefore, the sensor requires no calibration. The sensitivity of the sensor, (2.0 ± 0.2) × 10² μA cm⁻² mM⁻¹, is reproducible. The upper limit of detection is ~2.0 mM and the kinetics of the bioelectrocatalytic reaction is determined the limitation. The fabricated sensors were applied in the determination of d-fructose in commercial beverages as well as honey, and compared favorably with a more commonly used photometric method.