Novel continuous glucose monitoring techniques within reaction
Within REACTION two novel concepts for continuous glucose monitoring are followed. The first sensor concept integrates the glucose sensor into an insulin infusion catheter, exhibiting only a single-port body interface. The surface of the catheter is covered with an enzymatic luminescence-based glucose sensor and a reference oxygen sensor. The contactless read-out of the sensor is performed via NIR-radiation transcutaneously. Frequency-domain measurements in the near infrared region were possible in skin and subcutaneous tissue. In vivo experiments in pigs demonstrated that glucose concentration followed the glucose profile in blood and that simultaneous insulin delivery at the site of glucose measurement did not affect the measured glucose concentration. Adjusted glucose profiles were maintained via intravenous glucose infusion and subcutaneous insulin infusion and included hypo- and hyperglycaemic episodes (40-250 mg/dL). The insulin infusion rate was adapted to common insulin pumps and insulin infusion was synchronized with subcutaneous glucose measurement. The second sensor concept is based on infrared difference transmission spectroscopy in the first overtone band, using LED's. The optical transmission cells were integrated into a disposable polymer chip, connected to a microdialysis catheter. The glucose concentration correlates linearly with the difference signal, giving a limit of detection of about 18 mg/dL for signal-to-noise ratios of about 10,000. If signal drift is compensated, a relative accuracy of better than 5% for glucose concentrations above 50 mg/dL can be achieved. Measurements on blood plasma, demonstrated that similar results can be achieved as with the aqueous glucose solutions, if an individual calibration of the sensor is performed.