Development of a Miniaturized Glucose Monitoring System by Combining a Needle-Type Glucose Sensor With Microdialysis Sampling Method: Long-term subcutaneous tissue glucose monitoring in ambulatory diabetic patients

OBJECTIVE To develop a reliable and practical glucose monitoring system by combining a needle-type glucose sensor with a microdialysis sampling technique for long-term subcutaneous tissue glucose measurements.

RESEARCH DESIGN AND METHODS A microdialysis Cuprophan hollowfiber probe (inner diameter, 0.20 mm; length, 15 mm) was perfused with isotonic saline solution (120 μl/h) and glucose concentrations in the dialysate were measured by a needle-type glucose sensor extracorporeally. This system was tested both in vitro and in vivo. Subcutaneous tissue glucose concentrations were then monitored continuously in 5 healthy and 8 diabetic volunteers for 7 to 8 days. A hollow-fiber probe was inserted into the abdominal subcutaneous tissue.

RESULTS This monitoring system achieved excellent results in vitro. Subcutaneous tissue glucose concentrations were measured in a wide range from 1.7 to >027.8 mM glucose, with a time delay of 6.9 ±1.2 min associated with a rise in glucose and 8.8 ±1.6 min with a fall in the glucose level (means ± SE). The overall correlation between subcutaneous tissue (Y) and blood (X) glucose concentration was Y = 1.08X ± 0.19 (r = 0.99). The subcutaneous tissue glucose concentration could be monitored precisely for 4 days without any in vivo calibrations and for 7 days by introducing in vivo calibrations.

CONCLUSIONS Glycemic excursions could be monitored precisely in the subcutaneous tissue by this microdialysis sampling method with a needle-type glucose sensor in ambulatory diabetic patients.