PROTEIN ADSORPTION TO HEMA/EMA COPOLYMERS STUDIED BY INTEGRATED OPTICAL TECHNIQUES

Adsorption of chromophore-labeled bovine serum albumin (BSA) to homopolymers and copolymers of hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) was measured using integrated optical waveguide attenuated total reflection (IOW-ATR) spectrometry. In IOW-ATR, the intrinsic propagation loss of the waveguide, usually on the order of 1 dB/cm, is increased by the adsorption of a chromophoric molecule to the waveguide/solution interface. Measuring the difference in propagation losses before and after protein adsorption allows one to calculate the amount of protein adsorption (e.g., ng/cm2) directly from the Beer-Lambert law without calibration. Adsorbed amounts ranged from 35 ± 2 to 684 ± 55 ng/cm2 for the HEMA and EMA homopolymers, respectively. Radiolabeling experiments of 125I-BSA adsorption to the HEMA/EMA polymers performed in tandem correlated strongly with the IOW-ATR results (R2 = 0.934). Except for the EMA homopolymer, both techniques showed BSA surface densities that increased linearly with decreasing mol% HEMA of the polymer. © 1993 Academic Press, Inc.