Control of Protein Adsorption to Cyclo Olefin Polymer by the Hofmeister Effect

Cyclo olefin polymer (COP) is an attractive plastic because it has low protein adsorption despite its hydrophobic chemical structure. Here, the adsorption of model proteins to the COP was evaluated in comparison with a representative plastic, polystyrene (PSt), using reflectometry interference spectroscopy (RIfS) technology. The effects of different salts on adsorption were then examined. The adsorption of bovine serum albumin onto COP increased in the presence of kosmotropic salts, whereas adsorption of IgG increased in the presence of chaotropic salts. By contrast, the adsorption of these 2 proteins to PSt was unaffected by these Hofmeister salts. Langmuir-Freundlich model of COP adsorption suggested that the COP surface is more homogeneous for protein binding than the PSt surface. Furthermore, RIfS and sum frequency generation analyses indicated that water molecules bind more weakly to COP than to PSt. Our data propose a novel viewpoint of the way protein binds to COP surface that is different from the way it binds to PSt.