The immobilization of glucose oxidase onto radio-frequency plasma-modified poly(etherurethaneurea)

Abstract

Glucose oxidase was covalently immobilized onto a radio-frequency plasma-modified poly(etherurethaneurea). Thin (90-100 nm) plasma-polymerized N-vinyl-2-pyrrolidone films were deposited onto poly(etherurethaneurea) films. Active sites for the immobilization were obtained via reduction with aqueous sodium borohydride and activation with 1-cyano-4-dimethylaminopyridinium tetrafluoroborate. Modified poly(etherurethaneurea) films were assayed for binding and activity of the immobilized glucose oxidase layer. The results of a modified radioimmunoassay and an 'immunochemical stain' indicated that washing in 900 ml of continuously stirred 2% sodium dodecyl sulfate, 2% Triton X-100, and 20 mM sodium phosphate, pH 7.0, for 24 h each at 4 degrees C was necessary to remove physically adsorbed glucose oxidase from the solid supports. An amperometric activity determination in 9 ml of well-stirred 20 mM sodium phosphate-0.1 M sodium chloride, pH 7.4, gave a qualitative demonstration of the activity of the immobilized enzyme on 18.75 cm2 of modified poly(etherurethaneurea) film. A colorometric activity determination using the coupled reaction with o-dianisidine and peroxidase indicated that glucose oxidase covalently immobilized on approximately 2.4 cm2 of modified poly(etherurethaneurea) film had an activity approximately equal to that of 13.4 nM glucose oxidase in 50 mM sodium acetate, pH 5.1, with a specific activity of approximately 32.0 U/mg at pH 5.1 and room temperature.