Field-effect enzymatic amplifying detector with picomolar detection limit.

Voltage-controlled amplification of the output current of an enzymatic detector has been demonstrated. By application of an external voltage between the gating electrode and the working electrode on which the enzyme glucose oxidase was immobilized, the biocatalytic output current of the detector was increased significantly, allowing the detection limit of glucose to be lowered from the millimolar level to the picomolar level. The current amplification could be reversibly controlled by the applied voltage. Application of this technique to the ethanol-alcohol dehydrogenase system showed similar results. The detection setup suggests that the output current is controlled by the electric field at the interface between the solution and the working electrode. The enzyme's biospecificity was preserved in the presence of the field. The detector, with its output current controlled by a voltage applied at a third electrode, behaves as a field-effect transistor, whose current-generating mechanism is the conversion of an analyte to a product using an enzyme as catalyst. In a broader sense, the operation of the detector shows a means for manipulating a redox enzymatic reaction.