PROTEIN ADSORPTION ONTO IONIC SURFACES

The hydrophobic surface of poly(ethylene terephthalate) fibers was subjected to graft polymerization of non-ionic and ionic monomers in the preparation of non-ionic and ionic hydrophilic polymer surfaces. In addition, ionic hydrogels were prepared by the crosslinking of anionic gelatin in the presence and absence of an anionic polymer. Batch adsorption tests on the grafted surfaces were conducted using proteins with different isoelectric points such as serum albumin, acidic immunoglobulin G, basic immunoglobulin G, and basic fibroblast growth factor. The results of protein adsorption onto these grafted surfaces and protein sorption into the hydrogels could be explained in terms of the electrostatic attraction and repulsion between the charged surfaces and the charged protein molecules. Surfaces grafted with negatively (or positively) charged polymer chains attracted positively (or negatively) charged proteins, whereas grafted surfaces and proteins with the same charge sign exhibited repulsion. Surfaces grafted with non-ionic polymer chains tended to reject protein adsorption, regardless of the isoelectric point of the protein, probably because of steric hindrance by the graft chains.