COVALENT IMMOBILIZATION OF GLUCOSE-OXIDASE ON SILANIZED PLATINUM MICROELECTRODE FOR THE MONITORING OF GLUCOSE

The use of glucose oxidase (GOD) in electrochemical sensors for glucose detection is reported. The aim of this study was to show the feasibility and the performances of enzymatic platinum electrodes prepared by direct covalent coupling of GOD. The glucose oxidase enzyme electrode is used in a batch and flow injection analysis (FIA) system. It has been demonstrated that oxidized Pt can be silanized with surface densities comparable to those of silica; the grafting densities do not depend on the preparation method of Pt oxide, but on the nature of the monofunctional silane used. The best sensitivities for glucose detection are obtained using the coupling of 1,2,4,5-benzene tetracarboxylic acid dianhydride (BTCAD) and succinic anhydride with the aminosilanized electrodes. This coupling procedure leads to a dynamic range of response up to 30 mM in batch conditions because of no limitation by diffusion. In comparison, the BSA crosslinking technique results in a much higher sensitivity (about 200-fold) but also in the dynamic range limited to 2 mM. The sensitivity after a two-month storage remains 50% of its initial level for BTCAD coupling. The sensitivity can be amplified by performing an additional coupling process using the CDI reagent on a BTCAD-coupled enzyme electrode, whereas the opposite effect is obtained with GA. Nevertheless, the succinic anhydride-coupled electrode exhibits high non-specific signals in yeast fermentation broth samples because of the presence of electroactive interferents.