Adsorption of protein streptavidin to the plasma treated surface of polystyrene

Abstract

Immobilization of protein streptavidin to the surface of polystyrene (PS) polymer was studied by X-ray photoelectron spectroscopy (XPS). Two different protocols were used to attach streptavidin to the PS surface: physical adsorption and chemical coupling. In both cases the surface properties of PS samples were modified by exposure to cold oxygen plasma for 10s. Plasma was created in oxygen at 75Pa by en electrode-less RF discharge. The RF generator operated at 27.12MHz and the nominal power was about 120W. The electron temperature was about 3eV, the plasma density was about 3×1015m−3 and the neutral oxygen atom density was about 3×1021m−3. Oxygen plasma treatment caused formation of O-rich functional groups on the surface of PS. The concentration of oxygen was determined by XPS and was about 28at.%. A thin film of streptavidin was deposited by physical adsorption and chemical bonding. The appearance of streptavidin on the surface was determined from XPS spectra measuring the ratio between N and C peaks. The plasma treatment caused poor adsorption and but strong chemisorption of streptavidin. The results were explained by specific interaction of protein with polar functional groups on the surface of PS after plasma treatment.