Generation of amphoteric surfaces via glow-discharge technique with single precursor and the behavior of bovine serum albumin at the surface.

Amphoteric surfaces were generated on silicone substrates via plasma polymerization technique using a single monomer; diethyl allyl phosphate (DAP). Surface characterization was performed by the means of contact angle titration and Fourier transform infrared (FTIR) spectroscopy. The surface of silicone was found to be slightly basic with an apparent basicity of 0.12 μmol/m(2) while plasma surface modification made the surfaces amphoteric with the surface acid/base concentration adjustable by varying plasma parameters. The adsorption of model protein; bovine serum albumin (BSA) on the surfaces was found to be correlated to the surface acid/base ratio. Percent reduction on modified surfaces compared to bare silicone surface was 32, 59 and 92% for 20 W 5 min, 60 W 5 min and 100 W 5 min modified surfaces respectively. Conformational change of BSA upon adsorption to the surfaces was investigated with FTIR-ATR spectroscopy. It has been shown that BSA preserves more of its secondary structure upon adsorption to plasma modified surfaces than the bare silicone surface. It has been concluded that DAP modified surfaces reduces the amount of protein adsorption on the surfaces due to the modified surfaces amphoteric nature and the ability of modified surfaces to preserve the secondary structure of adsorbed protein better than the bare silicone surface.