DIRECT ELECTRICAL DETECTION OF DISSOLVED BIOTINYLATED HORSERADISH-PEROXIDASE, BIOTIN, AND AVIDIN

The uptake of biotin-labeled horseradish peroxidase (B-HRP) by an avidin-containing, electron-conducting redox hydrogel film on the surface of an electrode rotating in an H2O2 solution and poised at +0.1 V (Ag/AgCl) produced a substantial (50 mu A cm(-2)) electrocatalytic current. The current resulting from H2O2 electroreduction to water signaled promptly the occurrence of the avidin/B-HRP reaction. In competitive assays, dissolved biotin was detected through its blocking of the binding of B-HRP to the avidin-redox hydrogel-coated electrode, and dissolved avidin was detected through its competing for electrode-binding B-HRP in solution. Washing of the electrode was not required in any of these assays.