IMMOBILIZATION OF PROTEIN TO SURFACE-GRAFTED PEO/PPO BLOCK COPOLYMERS

Adsorption and covalent immobilization of Ig G to a grafted tetra-branched PEO/PPO block copolymer have been studied and related to the temperature-dependent properties of the grafted polymer. The investigation was performed by means of in situ ellipsometry, as well as by ESCA and ELISA measurements. The results show that the copolymer grafted to polystyrene (PS) surface contracts substantially upon increasing the temperature. A close interrelation was found between the properties of the grafted layer and the amount of protein (Ig G) that could be either adsorbed or covalently immobilized to the modified PS surface. By utilizing the reversed temperature phase behavior exhibited by these copolymers a relatively high loading of protein was obtained at temperatures close to the cloud point. By lowering the temperature after immobilization, the grafted layer regains its hydrophilicity and protein-rejecting properties. Thus, problems associated with interaction between bound protein and the underlying solid surface are minimized.