Protein adsorption to poly(ethylenimine)-modified Sepharose FF: VIII: Impacts of surface ion-exchange groups at different polymer grafting densities.

Our previous studies on protein adsorption to the anion-exchangers of poly(ethylenimine) (PEI)-grafted Sepharose FF found that both adsorption capacity and uptake rate of bovine serum albumin (BSA) increased greatly when the PEI grafting density reached over a critical ionic capacity (cIC) due to the 3D protein binding and occurrence of "chain delivery" of bound proteins. Moreover, by the investigation on the anion-exchangers of diethylaminoethyl (DEAE)-modified and DEAE-dextran-grafted Sepharose FF, we found the unique role of surface ligand in facilitating protein uptake kinetics on dextran-functionalized anion exchangers as the "transfer station" for the "chain delivery" of bound proteins. However, what would be the contribution of surface ligands on the transport of bound proteins on PEI chains at a wide range across cIC, particularly at the lower IC range where no "chain delivery" was present? We have thus designed this research to answer the question.