Effect of the matrix structure and concentration of polymer-immobilized Ni2+-iminodiacetic acid complexes on retention of IgG1.

Terpolymer bead particles (100–350 μm in diameter) were prepared by suspension radical polymerization from methacrylate esters [2,3-epoxypropyl methacrylate (GMA), 2-(2-hydroxyethoxy)ethyl methacrylate (DEGMA) and ethylene dimethacrylate (EDMA)] and subsequently derivatized affording iminodiacetic acid (IDA) chelating sorbents. The sorbents differed in pore volumes (0–0.7 cm3/g) and specific surface areas (0.03–9.8 m2/g) of their matrices as well as in the amounts of immobilized Ni2+–IDA complexes (0.03–1.58 mmol/g). The binding of imidazole was studied by frontal chromatography to evaluate the accessibility of Ni2+–IDA complexes. It was found that an increase in the bonded imidazole content with increasing immobilized Ni2+–IDA concentration was strongly dependent on the matrix morphology. A higher pore volume of the matrix significantly improved the utilizability of Ni2+–IDA complexes for imidazole binding. The performance of the sorbents based on two porous matrices with immobilized Ni2+–IDA concentration (0.1–1.58 mmol/g) differing in pore size distributions was compared in immobilized metal affinity chromatography (IMAC) of monoclonal mouse immunoglobulin IgG1 specific against human choriogonadotropic hormone (GTH-spec IgG1). The results have shown that sorbents based on matrix with large pores (up to 20 μm in diameter) exhibited high protein binding capacities. The GTH-spec IgG1 (Mw=158,000) was eluted from all the sorbents in its native form as was confirmed by MALDI-TOF.