PHOTO-CROSS-LINKED COPOLYMERS OF 2-HYDROXYETHYL METHACRYLATE, POLY(ETHYLENE GLYCOL) TETRA-ACRYLATE AND ETHYLENE DIMETHACRYLATE FOR IMPROVING BIOCOMPATIBILITY OF BIOSENSORS

A copolymer containing 88% 2-hydroxyethyl methacrylate (HEMA), 9% poly (ethylene glycol) (MW 18.5 kDa) tetra-acrylate and 3% ethylene dimetha crylate was prepared and evaluated for use as a biocompatible interfac e between glucose biosensors and tissue in the rat. The glucose sensor utilizes glucose oxidase that is electrically 'wired' to a gold curre nt collector by a reduction-oxidation polymer. Coatings of the copolym er were crosslinked in situ on the sensors using long wavelength ultra violet light and 2,2-dimethoxy-2-phenyl-acetophenone as the initiator. The effect these films had on the current response to glucose was mea sured. Over a glucose concentration range of 0-30 mM, the average perc entage decrease in response was 45 +/- 28% (mean +/- 95% confidence in terval) at 37 degrees C for films that were about 0.1 mm thick, an acc eptable value. Copolymer-treated and control electrodes were implanted in the intrascapular subcutaneous tissue of male Sprague-Dawley rats for three days. The explanted samples were evaluated using scanning el ectron microscopy. The control electrodes were highly encapsulated wit h fibrous material, while the copolymer-treated electrodes induced muc h less encapsulation. The results show this copolymer to be a candidat e as a biocompatible coating for electrically wired oxidoreductase-bas ed subcutaneous biosensors.