TRANSIENT MEASUREMENT OF GLUCOSE USING ON-OFF CONTROLLABLE ENZYME ELECTRODE WITH POLYPYRROLE MEMBRANE

A glucose sensor, using glucose oxidase immobilized in an electrically conductive polymer membrane, is developed for transient-mode measurem ent by on-off reaction control in the present work. An implantable glu cose sensor loses its stability under the skin by fouling resulting fr om fibroblast adhesion on the glucose oxidase-immobilized membrane. Ch ange in glucose distribution inside the membrane and in the vicinity o f the surface of the membrane resulting from the fouling makes the mea surement of the glucose concentration unstable. A technique of measuri ng transient current of the glucose sensor after activation of glucose oxidase may hardly be affected by the fouling as oxidation of coenzym e of glucose oxidase is rapid and the transient current is sensitive t o glucose concentration. A glucose sensor with glucose oxidase immobil ized in an electrically conductive polypyrrole membrane was fabricated . The activity of the glucose oxidase is switched on and off by a step wise change of potential of the polypyrrole membrane from 0.15 V to 0. 45 V versus a saturated calomel electrode. The two conditions describe d above can be confirmed by measuring transient current. Current incre ased momentarily after activation of glucose oxidase and decreased mod erately after that. The oxidation and reduction of glucose oxidase is sufficiently rapid, and current intensity depends on glucose concentra tion in the test solution.