Search

Amperometric biosensors based on two different NADH catalytic systems are presented. Common to both types is the design strategy which consists in the direct mixing of the NAD' -dependent dehydrogenase enzymes and other modifying molecules with the carbon paste combined with physical barriers like dialysis membranes or conducting polymers. One type is based on the use of a redox mediator (the phenothiazine dye Toluidine Blue O) to make possible the electrocatalytic oxidation of the enzymatically produced NADH at potentials close to 0 V. The second type is based on the use of the electrochemically generated conducting polymers poly(o-aminophenol) (PAP) and poly(o­phenylenediamine) (PPD), which allow not only the immobilization of enzyme and cofactor at the electrode surface but also the amperometric detection of NADH at potentials as low as 0 V without other immobilized electron transfer mediators. An ethanol biosensor based on the first catalytic system and ethanol, lactate and glutamate sensors based on the second one are presented.