A thermodynamic evaluation of antibody-surface interactions in multimodal cation exchange chromatography.

In this study, the thermodynamics of binding of two industrial mAbs to multimodal cation exchange systems was investigated over a range of buffer and salt conditions via a van't Hoff analysis of retention data. Isocratic chromatography was first employed over a range of temperature and salt conditions on three multimodal resins and the retention data were analyzed in both the low and high salt regimes. While mAb retention decreased with salt for all resins at low salts, retention increased at high salts for two of the resins, suggesting a shift from electrostatic to more hydrophobic driven interactions. The retention data at various temperatures were then employed to generate non-linear van't Hoff plots which were fit to the quadratic form of the van't Hoff equation. At low salts, retention of both mAbs decreased with increasing temperature and the van't Hoff plots were concave downward on Capto MMC and Nuvia cPrime, while being concave upward on Capto MMC ImpRes. Different trends were observed on some of the resins with respect to both the concavity of the van't Hoff plots as well as the impact of temperature on the favorable enthalpies in the low salt regime. Interestingly, while increasingly favorable enthalpy with temperature was observed with Capto MMC and Nuvia cPrime at low salt, favorable enthalpy decreased with temperature for Capto MMC ImpRes. At high salts, binding of both mAbs on the two Capto resins were consistently entropically driven, consistent with desolvation. While the negative heat capacity data at low salts indicated that desolvation of polar/charged groups were important in Capto MMC and Nuvia cPrime, the positive data suggested that desolvation of non-polar groups were more important with Capto MMC ImpRes. Finally, the data at high salts indicated that desolvation of non-polar groups was the major driver for binding of both mAbs to the Capto resins under these conditions.