Static protein adsorption, ultrafiltration behavior and cleanability of hydrophilized polysulfone membranes

A systematic study on the influence of incrementally increased hydrophilicity of UF membranes made from chemically modified polysulfone on static protein adsorption, protein ultrafiltration performance and cleanability was performed. Hydrophilicity was imparted to the polymeric backbone either by carboxylation or sulfonation. Membranes with 100% retention towards sulfhydryl modified bovine serum albumin (cys-BSA) were made by the phase inversion process from unmodified polysulfone, five carboxylated polysulfones (degrees of carboxylation ranging from 0.26 to 1.74) and two sulfonated polysulfones (degrees of sulfonation of 0.24 and 0.58). 1000 ppm aqueous solutions of cys-BSA at pH values 3, 4.8 and 9 were used in KCI medium at either low or high concentration. Static adsorption, ultrafiltration (UF) flux reduction and protein binding strength were lower at pH 3 than at pH 9 but reached an expected maximum at the protein's isoelectric point at pH 4.8. Hydrophilized polysulfone membranes show less static adsorption and lower UF flux reduction than hydrophobic unmodified membranes. In all experiments we found that the higher the degree of carboxylation or sulfonation, the greater this effect. High ionic strengths reduced these advantages at pH values above or below the IEP but had a positive effect at the IEP. (C) 1999 Elsevier Science B.V. All rights reserved.