The nonspecific protein binding of polymeric microporous membranes.

Sterile filtration of high value biotechnology products is commonly employed as the final processing step of protein or drug production. The nonspecific binding (NSB) of proteins to the vast internal surface area of polymeric microporous membranes can effect product recovery. The objective of these experiments is to determine the NSB of some representative proteins and product recovery using commonly employed microporous membranes composed of different materials. The adsorption of the following four proteins was studied: (1) Porcine Insulin, (2) Human Chorionic Gonadotrophs (HCG), (3) Bovine Serum Albumin (BSA), and (4) Sheep Immunoglobulin G (IgG). Two basic types of experiments were performed: (a) Adsorption was determined by gamma counting of washed membrane disks after “static” exposure to known protein solutions. Static experiments were also performed to determine both kinetics and concentration effects on the protein adsorption; and (b) Protein recovery and adsorption were determined after typical dynamic sterile filtration. A variety of polymeric microporous membrane materials were evaluated including hydrophilic polyvinylidene fluoride (PVDF) , nylon, and polysulfone (PS-B, or C). In summary, the hydrophilic PVDF membranes were found to be extremely inert based on both NSB and product recovery when compared to microporous membranes composed of other polymeric materials.