Preparation and evaluation of dextran-grafted mixed-mode chromatography adsorbents

In the present work, mixed-mode chromatography adsorbents grafted with dextran of different molecular weight were prepared. Compared to non-grafted adsorbent (BA-6B), the morphology of dextran-grafted adsorbents (BA-6B-Ts) did not change significantly, while the water content (ω), porosity (P) and pore volume (V) decreased. Static adsorption, salt tolerance and dynamic adsorption behaviors of adsorbents BA-6B-Ts against BSA/IgG were studied. Compared to adsorbent BA-6B, adsorbents BA-6B-Ts had higher saturated adsorption capacity (Q_m) toward BSA/IgG, especially for BA-6B-T20, the Q_m values toward BSA and IgG increased by 32.8% and 39.5%, respectively. Adsorbents BA-6B-Ts showed enhanced salt tolerance toward BSA, and relatively weaker salt tolerance toward IgG. The relative adsorption capacity of BA-6B-T20 was 66.7% at 0.1 mol/L NaCl and 39.2% at 0.5 mol/L NaCl, higher than those of BA-6B. Moreover, for both BSA and IgG, the effective pore diffusivity (D_e) of BA-6B-Ts was higher than that of BA-6B. D_e values of BA-6B-T20 toward BSA and IgG increased by 77% and 139% compared to BA-6B, respectively. Dynamic binding capacities (DBCs) of BA-6B-Ts were also improved. DBC of BSA and IgG on BA-6B-T20 were 25.6% and 46.5% higher than those on BA-6B. The possible mechanisms for the above difference in adsorption behavior of dextran-grafted adsorbents toward BSA/IgG were discussed, providing some insights into protein adsorption and mass transport for dextran-grafted MMC resins.