Integrated-circuit bio-calorimetric sensor for glucose

Two integrated-circuit temperature-sensitive devices, each composed of three Darlington-connected npn transistors and a CMOS constant-current circuit, are used for calorimetric determination of glucose concentration. One device is modified with a cellulose triacetate/1,8-diamino-4-aminomethyloctane membrane and used for glutaraldehyde immobilization of glucose oxidase. The difference in steady-state output voltage of the enzyme-modified sensor compared to the unmodified sensor after addition of glucose is related to the temperature change induced by the enzyme-catalyzed reaction. Glucose is determined in the range 5–100 mM after signal analysis by fast-Fourier transform. The enthalpy change approximates to that ofa spherical silicon conduction model.