▎ 摘　　要

NOVELTY - Working electrode comprises (a) an electrode on which an enzyme and an electron transfer mediators are chemically immobilized, (b) a linker (I) which is fixed on the electrode by a covalent bond, (c) an enzyme which forms a covalent bond with the linker, and (d) an electron transport mediator forming a covalent bond with the linker. USE - The working electrode is useful in electrochemical biosensors and biofuel cells for measuring glucose (all claimed). ADVANTAGE - The working electrode continuously measures the concentration of glucose in bodily fluids such as sweat, saliva, tears, and urine in a non-invasive manner without blood sampling, and detects a low concentration of glucose of 9 mg/dl or less present in saliva, which is a significantly lower detection limit than that in blood. The change in redox potential for mass transfer in the solution is reduced through chemically complete immobilization, and the background current is very low through the surface electron exchange reaction, hence the electrode has excellent limit of detection (LOD) and limit of quantification (LOQ). DETAILED DESCRIPTION - Working electrode comprises (a) an electrode on which an enzyme and an electron transfer mediators are chemically immobilized, (b) a linker of formula (I) which is fixed on the electrode by a covalent bond, (c) an enzyme which forms a covalent bond with the linker, and (d) an electron transport mediator forming a covalent bond with the linker. INDEPENDENT CLAIMS are included for the following: method for preparing working electrode involves (a) preparing an electrode, (b) forming a hydroxy group on the electrode surface, (c) fixing a linker on the electrode through a covalent bond by reacting a silane having an epoxy group with the hydroxy group, and (d) reacting a mixture of an electron transfer mediator comprising an amine group and an enzyme comprising an amine group with the epoxy group to immobilize the electron transfer mediator and enzyme to the linker through a covalent bond; a planar type electrochemical biosensor comprising the working electrode, an auxiliary electrode and an verification electrode in one plane; a face-to-face type electrochemical biosensor comprising the working electrode and an auxiliary electrode facing each other on different planes; and a biofuel cell comprising the working electrode as an oxidizing electrode.