An implantable glucose sensor for closed-loop artificial pancreas

A needle-type glucose sensor, which was based on teflon coated platinum-iridium (Pt-Ir) alloy wire of 0.2 mm diameter, 1.2 mm/sup 2/ area of sensing part and 4 cm total length, was fabricated and its characteristics were examined. Carefully optimized inner, enzyme and outer layers were constructed on the Pt-Ir surface to enhance H/sub 2/O/sub 2/ permeation and suppress interferences. An in vitro test of the resultant sensor in phosphate buffered saline (PBS) showed so high a selectivity that the electrochemical response to normal human glucose levels suffered only from limited drifts by physiological maximums of major interferents such as ascorbic acid, acetaminophenol, urea, and uric acid. In addition, good sensitivity and reproducibility over a month were observed. Continuous measurements in vivo with a surface modified sensor implanted in the subcutaneous layer were taken successfully.