Novel Membranes for Hydrophobic Interaction Chromatography

Responsive membranes have been developed for hydrophobic interaction chromatography.  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 contact angle.  ATRP allows us to independently control chain density and molecular weight.  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 1.8 M (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 20 mM phosphate buffer with and without 1.8 M (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.