Modification of a PES microfiltration membrane to enhance sterile filtration by inhibiting protein adsorption

Microfiltration membranes are increasingly used in sterilization processes in the pharmaceutical industry. However, in the pharmaceutical industry, product loss caused by the adsorption of high value-added proteins to membranes during the sterilization process is a critical problem. Hence, it is necessary to reduce protein adsorption and fouling through the hydrophilic modification of the entire membrane, not just the surface. We developed a method for fabricating a porous poly(ethersulfone) (PES) microfiltration membrane using vapor-induced phase separation (VIPS) and then conducting hydrophilic modification of the membrane. Two types of symmetric membranes with 0.2 μm pores were prepared using two different additives, one of which was an amphiphilic copolymer (Pluronic® PE6400) that is known to increase the hydrophilicity of PES membranes. Both membranes had high water permeability and suitable mechanical strength. However, protein filtration testing, including an adsorption study, revealed that the hydrophilicity imparted by Pluronic was not sufficient to effectively inhibit protein adhesion. In contrast, the modification via the atom transfer radical polymerization of a hydrophilic oligomer (poly(ethyleneglycol) methacrylate) significantly increased the hydrophilicity of the entire membrane while reducing the surface roughness. These properties reduced protein adsorption and membrane fouling, to the benefit of sterile filtration and protein filtration processes.