Yoshio Hanazato

Integrated multi-biosensors based on an ion-sensitive field-effect transistor using photolithographic techniques

Two kinds of multifunctional biosensors, one sensitive to glucose and triolein and the other to glucose and urea, have been constructed using semiconductor fabrication techniques. An integrated ISFET (ion-sensitive field-effect transistor) with three hydrogen-ion-sensitive FET elements on one chip was used as a transducer for the biosensor. A photolithographic technique with a water-soluble photocrosslinkable polymer made possible the deposition of patterned enzyme membranes (glucose oxidase, lipase, and urease membranes) and bovine serum albumin membrane around each gate surface of ISFET elements. The multibiosensor for measuring glucose and triolein concentrations determined both glucose concentrations up to 5 mM and triolein concentrations up to 3 mM simultaneously. The biosensor for glucose and urea has a detection range of 0.03 to 3 mM for glucose and 0.1 to 20 mM for urea. Some multibiosensors showed a cross-sensitivity problem due to enzyme contamination. An improved membrane fabrication method to prevent the enzyme contamination is described. >

Neutral lipid enzyme electrode based on ion-sensitive field effect transistors

Abstract An enzyme electrode for neutral lipid determination based on hydrogen ion-sensitive field effect transistors (pH-FETs) is described. The electrode is composed of two pH-FETs with an immobilized lipase membrane on one pH-FET, and a platinum wire. Triglycerides are solubilized with 10% (v/v) Triton X-100. The electrode is used to determine triglycerides over wide concentration ranges with response times of ca. 2 min. Relations between signal and the logarithm of the concentration are linear over the ranges 100–400 mM triacetin, 3–50 mM tributylin and 0.6–3 mM triolein. In the case of triolein, the detection limit is 9 μg ml −1 (signal/noise = 3:1). The effect of Triton X-100 on the electrode response is discussed.