In vitro and in vivo performance and lifetime of perfluorinated ionomer-coated glucose sensors after high-temperature curing.

In this paper we report that curing at 120 degrees C can be used to improve the in vivo durability of a miniaturized glucose sensor with an outer coating of the Dupont perfluorinated ionomer, Nafion. Sensors based on glucose oxidase trapped in an albumin/glutaraldehyde matrix were able to withstand curing at 120 degrees C without noticeable change in electrode sensitivity (+/- 22% SD). Curing above 120 degrees C caused a gradual decline in sensitivity, with no sensitivity seen at 170 degrees C. Curing Nafion at 120 degrees C eliminated ascorbic acid and urea interferences and improved selectivity for glucose against uric acid and acetaminophen, compared to room temperature-cured Nafion coatings. The Nafion film reduced O2 demand by the sensor, so the signal was O2 independent across a partial pressure range of 8-140 mmHg. Several of the fully assembled, heat-cured, needle-type glucose sensors remained functional for at least 10 days after subcutaneous implantation in dogs, without degradation of their sensitivity (average 3 nA/mM in vivo at 37 degrees C and 6 nA/mM in vitro at 37 degrees C).