APPLICATIONS AND STABILITY OF A THERMOELECTRIC ENZYME SENSOR

Remarkable room-temperature sensitivity and stability have been achieved with thermoelectric enzyme sensors that detect the heat generated by various substrates reacting selectively on their enzyme-immobilized surfaces. Thin-film thermopiles together with cross-linked membranes of glucose oxidase and catalase have been employed to measure a linear voltage response to glucose [30 nV/ (mg/dl)] for concentrations ranging from 16 to 280 mg/dl in oxygen-saturated solutions. 90% response time values are typically less than six seconds. One sensor stored at room temperature and operated intermittently did not significantly change its response to glucose over the course of five days, and ultimately failed after nine days. Another sensor stored at 37°C exhibited a daily decrease in sensitivity and failed after five days. Four sensors operated continuously at room temperature showed an average normalized decline in response to glucose of 0.0087 ± 0.0005 h-1 and operating times ranging between 30 and 78 h. Through the use of alternative enzymes, other sensors have been made that respond to either hydrogen peroxide or urea. The use of an alternative sensing mode in which the rate of voltage change is measured following a step change in concentration appears to extend the upper range of linear response to glucose. © 1990.