Carbon felt-based reagentless amperometric hydrogen peroxide biosensor using co-immobilized toluidine blue O and horseradish peroxidase

The electron-transfer mediator, toluidine blue O (TBO), was covalently immobilized together with horseradish peroxidase (HRP) onto cyanuric chloride-activated porous carbon felt (CF) in order to fabricate a second generation reagentless H2O2 biosensor. Cyclic voltammetry (CV) indicated that the immobilized TBO efficiently mediates electrons from the CF electrode to the redox active center of the HRP. The resulting CF electrode (TBO-HRP-CF) exhibited amperometric responses to H2O2 with the relatively fast response time of similar to 15 s in the concentration range from 5 x 10(-5)M to 5 x 10(-3)M (M = mol dm(-3)) with a detection limit of 5 x 10(-5)M H2O2 in 0.1 M phosphate buffer (FH 7.0).