IMPLANTABLE ELECTROCATALYTIC GLUCOSE SENSOR

An electrocatalytic glucose sensor for in vivo application has been de veloped to determine the glucose level in blood and further to control the insulin dosage in a closed loop system for diabetes therapy. The principle of the electrocatalytic glucose sensor is based on the direc t electrochemical oxidation of glucose at a membrane-covered platinum electrode. For a possible clinical application the sensor was built as a catheter. A set of implantations in the vena cava of sheep demonstr ated the potential feasibility of the sensor. The sensor values were s imultaneously checked by the enzymatic analysis of glucose in blood sa mples drawn separately from a femoral vein. It was possible to determi ne the glucose concentration in sheep for more than 130 days with tole rable deviations from glucose reference measurements. The mean error w as 2.5 mmol/l. One of the catheters was explanted after 211 days and t he histological examination revealed a good biocompatibility of all ma terials used. In additional experiments, the differences of the glucos e concentration in vena cava as well as in the anterior and posterior femoral veins of a sheep were examined during glucose tolerance tests. These experiments verified our method of in vivo calibration of the l ong-term implantable glucose sensor.