An electrocatalytic glucose sensor for in vivo application has been developed 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 direct 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 demonstrated the potential feasibility of the sensor. The sensor values were simultaneously checked by the enzymatic analysis of glucose in blood samples drawn separately from a femoral vein. It was possible to determine the glucose concentration in sheep for more than 130 days with tolerable deviations from glucose reference measurements. The mean error was 2.5 mmol/l. One of the catheters was explanted after 211 days and the histological examination revealed a good biocompatibility of all materials used. In additional experiments, the differences of the glucose 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 long-term implantable glucose sensor.

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A catheter shaped electrocatalytic glucose sensor for in vivo application has been developed to determine the glucose level in blood and control the insulin dosage in a closed loop system for diabetes therapy. The principle of measurement is based on the electrochemical oxidation of glucose at a membrane-covered platium electrode. For various potential steps, the impedance obtained at two different frequencies is a function of the glucose concentration. A series of implantations in the vena cava of sheep demonstrated the potential feasibility of the sensor. It was possible to determine the glucose concentration in sheep for more than 130 days with tolerable deviations from glucose reference measurements. The mean error was 2.5 mmol/l. The catheter was explanted after 211 days and histological examination revealed a good biocompatibility of all materials used.

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