Responsive membranes for hydrophobic interaction chromatography

Abstract

Poly N-vinylcaprolactam (PVCL) chains were grown from the surface of regenerated cellulose membranes using atom transfer radical polymerization (ATRP). Modified membranes were characterized using scanning electron microscopy, infrared spectroscopy, X-ray photoelectron spectroscopy and by measuring surface contact angles. The grafting degree of PVCL increases with increasing ATRP initiator immobilization time. PVCL is a thermo-responsive polymer with a lower critical solution temperature (LCST) that depends on the concentration of salt ions present in solution. The LCST decreases below room temperature in buffer containing 1.8M (NH3)2SO4 where the polymer adopts a more hydrophobic/collapsed conformation. At low ionic strength, the LCST remains above room temperature. Contact angles for PVCL in 20mM phosphate buffer with and without 1.8M (NH3)2SO4 were determined. Contact angles in the buffer with high ionic strength were higher than those in low ionic strength.Adsorption and desorption of bovine serum albumin (BSA) and immunoglobulin G (IgG) have been investigated. Loading was conducted in high ionic strength buffer. Elution was conducted in low ionic strength buffer. By using a responsive ligand that changes its conformation during loading and elution, high protein recoveries were obtained. Ligands that respond to solution ionic strength show promise for high performance hydrophobic interaction chromatography.