Development of a bio-thermochip and its application for the detection of glucose in urine

A portable and inexpensive biothermistor system (bio-thermochip) has been developed by constructing the enzyme immobilization support around the bead thermistor. The support enhances the enzyme loading and heat production around the thermistor. Glucose oxidase (GOD) and bovine serum albumin (BSA) were immobilized around the two bead thermistors, respectively. The temperature difference between the GOD immobilized thermistor and the BSA immobilized reference thermistor was measured in an insulated cell, allowing detection of small temperature changes. A linear calibration graph was obtained for glucose concentrations in the range of 1 to 4 mM. The response of the bio-thermochip was about a factor of two larger than the thermistor without enzyme support. The response was maximum at pH 6 and independent of the presence of ascorbic acid and other reducing components in urine. This system is suitable for the measurement of glucose in urine.