Hybrid biosensor for simultaneous electrochemical and thermometric detection

Simultaneous detection of multiple signals for common biochemical/electrochemical reactions is a challenging area of research for comparative studies. Based on our previous work with electrochemically assisted thermal biosensors, a hybrid biosensor has been developed for the simultaneous monitoring of the electrochemically generated current and the thermal signal produced in association with enzymatic catalysis. The sensor combined the two measurement principles of electrochemical regeneration of substrate and flow injection biocalorimetry. The enzyme column was constructed of a platinum foil in electrical contact with a poly (pyrrole)-coated reticulated vitreous carbon (RVC) matrix onto which tyrosinase was immobilized. The column functioned as enzyme reactor, working electrode and thermally sensitive element together with the thermistors. Catechol was oxidized by tyrosinase to form 1,2-benzoquinone which was subsequently regenerated electrochemically on the electrode surface. The primary heat production developed by the enzyme reaction could be measured calorimetrically. At the same time, the electrochemical reduction of 1,2-benzoquinone generated a current that was detected by the working electrode (enzyme column). Preliminary results showed good correlation of the two signals at both high and low oxygen concentrations in the buffer. A linear range between 12.5 and 250 mu M catechol was obtained for the enzyme reaction. The sensitivity of the thermal measurement system was significantly enhanced by the recycling of catechol. The hybrid sensor provides a useful tool for comparative studies.