Electrospun poly(styrene-co-maleic anhydride) nanofibrous membrane: A versatile platform for mixed mode membrane adsorbers

The traditional methods to introduce multi-functional groups onto the surface of membrane require unpleasant reaction conditions and complex procedures. Motivated by the need of an economical purification method in the downstream processing of therapic proteins, we develop a simple approach to fabricate mixed mode membrane adsorbers. Nanofibrous membrane support was fabricated by electrospinning a blend of poly(styrene-co-maleic anhydride) (SMA) with polyvinylidene fluoride (PVDF). Mixed mode ligands were then immobilized on the membrane through the conversion of anhydride moieties by aminolysis with functional amines, n-butylamine (BAE), n-octylamine(OAE), N-methyl-D-glumine(NMG). The obtained mixed-mode membrane adsorbers, PVDFS-g-BAE, PVDFS-g-OAE, and PVDFS-g-NMG, which contain hydrophobic interaction/ion exchange, reverse phase interaction/ion exchange, and hydrophilic interaction/ion exchange interactions respectively, were used for protein separation. The success of modification was supported by FTIR and XPS, indirectly confirmed by WCA measurements. Static protein binding property was measured with several model proteins. The PVDFS-g-BAE membrane showed a capacity of 120 mg/mL for IgG and fair selectivity over BSA or Lym; The PVDFS-g-OAE membrane showed a capacity of 140 mg/mL for alpha-CTP and high selectivity over CYT-C. In addition, the nanofibrous membrane has large total pore area, high porosity, and good mechanical property, which is sufficient for the demands of practical use.