Adsorption of bovine serum albumin onto homo- and copolymer latices

Abstract

The adsorbability of bovine serum albumin (BSA) onto various synthetic polymer latices was studied at different ionic strengths as a function of pH by determining the amount of protein adsorbed. Homopolymer latices—polystyrene (PS), polymethyl methacrylate (PMMA), and polyvinyl acetate (PVAc)—and copolymer latices—polystyrene/polymethacrylic acid (PS/PMAA) and polystyrene/polymethyl methacrylate/polymethacrylic acid (PS/PMMA/PMAA)—were prepared without emulsifier and monodisperse. All these materials were anionic latices. The initial BSA concentration was 50 mg/dl, which corresponded to the first plateau level of the adsorption isotherm. With an increase of the ionic strength, the amount of BSA adsorbed onto each latex increased except in the isoelectric region. The pH at maximum adsorption shifted to a more acidic region with increasing ionic strength. The amount adsorbed showed a maximum in the neighborhood of the isoelectric point of BSA. This maximum adsorption at each ionic strength increased in the order of PVAc, PMMA, PS, PS/PMMA/PMAA, and PS/PMAA. In the cases of PS/PMAA and PS/PMMA/PMAA latices, it was suggested that the increment of the amount adsorbed was related to hydrogen bond formation between protein and the latex. The amount of BSA adsorbed was found to be dependent not only on pH and ionic strength but on the characterization of polymer latex surface.