Rapid detection of hyperglycaemia by a subcutaneously-implanted glucose sensor in the rat

The relationship between the concentration of polymer in the coat of an electrochemical glucose sensor and the lag time between changes in blood glucose and sensor output was explored. Sensors designed to be highly permeable to glucose were coated with a polyurethane mixture diluted 1:6.7 (15%) in trichloroethane. Coats of those designed to be less permeable were diluted 1:2.5 (40%). The in vitro response of the 40% sensors, but not the 15% sensors, was nearly linear up to a glucose level of 56 mM. When tested in 10 rats, the response of the 15% sensors to injected glucose was much more rapid than that of the 40% sensors. The time difference between the peak blood glucose level and peak sensor output was also much smaller for the 15% sensors. In conclusion, use of an electrochemical glucose sensor with high permeability to glucose demonstrates that glucose in the intravascular space equilibrates very rapidly with the subcutaneous space.