Evaluation of photochemically immobilized poly(2-ethyl-2-oxazoline) thin films as protein-resistant surfaces

Poly(2-ethyl-2-oxazoline) (PEOX) of various molecular weights were covalently immobilized on silicon wafers and gold slides to form protein-resistant surfaces via a fast and general photocoupling chemistry based on the CH insertion reaction of light-activated perfluorophenyl azide (PFPA). The thicknesses of the immobilized PEOX films ranged from 23 to 80 Å for molecular weight of 5000 to 500,000, and the grafting density reached 3.2 × 10(-3) Å(-2) for PEOX 5000. The protein-resistant property of the films was studied using bovine serum albumin (BSA) by fluorescence imaging, ellipsometry, and surface plasmon resonance imaging (SPRi). The fluorescence imaging and ellipsometry studies showed the largest amount of BSA adsorbed on PEOX 5000 and the smallest on PEOX 500,000. This was consistent with the kinetic analysis of BSA adsorption by SPRi showing that PEOX 5000 exhibited the fastest association rate and the slowest dissociation rate whereas PEOX 500,000 had the slowest association rate and the fastest dissociation rate. The PEOX film was then applied in the fabrication of carbohydrate microarrays to reduce the nonspecific adsorption of lectins and thus the background noises. Results showed that the microarray signals were significantly enhanced when the PEOX film was used.