A continuous glucose monitoring system based on microdialysis

The development of a system for continuous glucose measurement is described. A microdialysis fibre is used to continuously withdraw the glucose sample. After passing through the microdialysis fibre the perfusion liquid enters a micro-enzyme reactor which is filled with immobilized glucose oxidase. The enzyme activity, which varies with the glucose concentration, is monitored by an oxygen electrode. The measuring system can be adapted to a desired dynamic range by varying the perfusion rate. The measurement system has been calibrated for two different perfusion rates and shows a linear response to glucose concentrations between 0-3.5 mmol at 12 microliters/min and 0-8 mmol at 25 microliters/min. A probe, which can be configured with different lengths of the dialysing fibre, has also been designed to enable subcutaneous insertion of the microdialysis fibre in clinical studies. Subcutaneous glucose sampling by means of microdialysis is suggested to be used in the design of a glucose monitoring device for clinical use.