Mamiko Nakako

Glucose sensor based on a field-effect transistor with a photolithographically patterned glucose oxidase membrane

Abstract A photopolymer solution consisting of polyvinylpyrrolidone and 2,5-bis(4′-azido-2′-sulfobenzal)cyclopentanone is used to make a patterned glucose oxidase membrane for a FET-glucose sensor by photolithography. A small patterned glucose oxidase membrane, 0.2 mm wide and 1 mm long, is made on the gate surface of an ISFET by developing a photocross-linked glucose oxidase membrane with aqueous 1–3% glutaraldehyde solution. The optimum composition of the enzyme/photopolymer solution is described. The sensor with the patterned membrane showed linear response to glucose concentration from 0.3 to 2.2 mM and useful response up to 5 mM.

Glucose-sensitive field-effect transistor with a membrane containing co-immobilized gluconolactonase and glucose oxidase

Abstract A glucose-sensitive field-effect transistor (FET) with a two-enzyme membrane containing gluconolactonase and glucose oxidase is investigated. The two-enzyme membrane (ca. 1 μm thick) is formed on the ion-sensitive gate of the FET by photopolymerization. The gluconolactonase used was a partially purified product prepared from crude glucose oxidase by gel filtration. A glucose sensor with only purified glucose oxidase has little response for glucose, but the co-immobilization of gluconolactonase and glucose oxidase considerably enhanced the response amplitude of the glucose sensor. The composition of the two-enzyme/photopolymer solution is optimized; gluconolactonase with an activity at least twice that of glucose oxidase is necessary. The linear calibration graph extends from 0.2 to 2 mM glucose.

A flow-through cell for use with an enzyme-modified field effect transistor without polymeric encapsulation and wire bonding

Abstract A new type of flow-through cell for an enzyme-modified field effect transistor (FET) is described. The cell makes it possible to use a FET without polymeric encapsulation and wire bonding. Electrical evaluation of a FET used with the flow cell demonstrates that the flow cell has no practical problems causing sensor malfunctions. The noise and drift levels of tbe FET sensor with the flow cell are shown to be similar to those of an epoxy-encapsulated FET sensor. The application of the flow cell with a urease-modified FET is described. Useful responses are obtained for 0.25–50 mg l−1 urea with relative standard deviations of