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Characteristics of ISFET-type β-Glucosidic Glucoside Sensor Using
Thermophilic Enzymes β-Glucosidase and Glucokinase

Kazuhito AOKI, Yoshihiro ISHIMARU and Takeaki IIDA*

Department of Functional Materials Science, Faculty of Engineering, Saitama University;
255 Shimo-okubo, Urawa-shi 338-8570 Japan

An ion sensitive field-effect transistor (ISFET) combined with immobilized thermophilic enzymes was applied to the determination of β-D-glucosidic glycosides. In order to improve the stability of the biosensor, the pH-sensing gate of ISFET was covered with the thermostable enzyme layer using thermophilic β-D-glucosidase and glucokinase. The characteristics of the developed bienzyme ISFET sensor were studied using the samples of β-glucosidic glycosides such as salicin and esculin. The dynamic range from 0.3 mM to 30 mM(1 M=1 mol dm−3) was obtained for salicin at pH 7.0. The responses were enhanced in the temperature range from 40 to 60 °C.
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