REAGENTLESS MEDIATED LACCASE ELECTRODE FOR THE DETECTION OF ENZYME MODULATORS

We have investigated aerobic mediation of electron transfer to a lacca se enzyme by the solution redox couples [OsO(bpy)(2)Cl-2](+/0) and [Os (bpy)(2)(MeIm)Cl](2+/+), where bpy is 2,2-bipyridine and MeIm is N-met hylimidazole. The factors that influence the homogeneous mediation rea ction are investigated and discussed. Investigation of ionic strength, pH, and temperature effects on the kinetics of intermolecular electro n transfer elucidates the governing factors in the mediator-enzyme rea ctions. Coimmobilization of both enzyme and an osmium redox mediator i n a hydrogel on glassy carbon electrodes results in a biosensor for th e reagentless addressing of enzyme activity, consuming only oxygen pre sent in solution. Thus, these immobilized enzyme biosensors can be uti lized for the detection of modulators of laccase activity, such as the inhibitor sodium azide. The enzyme inhibition biosensor can detect le vels of azide as low as 2.5 x 10(-6) mol dm(-3) in solution.