Characterization of immunoglobulin adsorption on dextran-grafted hydrophobic charge-induction resins: Cross-effects of ligand density and pH/salt concentration

Hydrophobic charge-induction chromatography (HCIC) is a promising technology for antibody purification. New HCIC resins MMI-B-XL with dextran-grafted agarose gel as the matrix and 2-mercapto-1 -methyl-imidazole (MMI) as the functional ligand were prepared with different ligand densities. The adsorption behaviors (static adsorption equilibrium and adsorption kinetics) of human immunoglobulin G (hIgG) on series of MMI-B-XL resins at varying pHs and salt concentrations were investigated. The cross-effects of solid phase property (ligand density) and liquid phase conditions (pH and salt concentration) were focused. The results showed that the new resins had typical pH-dependent and salt-tolerant characteristics for hIgG adsorption, but differences were found for the resins with different ligand densities. For MMI-B-XL resins with higher ligand density, an obvious higher saturated adsorption capacity (Q(m)) and effective pore diffusivity (De) could be obtained, which were less affected at pH 7.0 similar to 8.9 but dropped drastically at pH 5.0. Salt addition had less influence on protein adsorption onto MMI-B-XL with higher ligand density. Q(m) and D-e both reached minimum values at 0.2 mol/L NaCl for all MMI-B-XL resins tested. The results of dynamic binding in the column demonstrated that MMI-B-XL with higher ligand density had better performance for hIgG adsorption, especially under high linear velocities. The mechanism of the cross-effects of ligand density and pH/salt concentration on IgG adsorption was discussed, which provides new insights into protein adsorption and mass transport for dextran-grafted HCIC resins. (C) 2015 Elsevier B.V. All rights reserved.