Fabrication of high-capacity protein ion-exchangers with polymeric ion-exchange groups grafted onto micron-sized beads by atom transfer radical polymerization

The static adsorption capacity for proteins is regarded as the benchmark for achieving high binding capacity in protein chromatography. This research provided an efficient and controlled approach for the synthesis of ion-exchange beads with high adsorption capacity via surface-initiated atom transfer radical polymerization (SI-ATRP) by grafting methacryloxyethyltrimethyl ammonium chloride to a micron-sized poly(glycidyl methacrylate) (pGMA) matrix. The result showed that grafting of polymeric ion-exchange groups significantly increased the ionic capacity of the micron-sized beads and the adsorption density for γ-globulin. The adsorption capacity for γ-globulin could be optimized by tuning the chain length and the density of the charged polymer grafted onto the beads. The maximal saturated adsorption capacity for γ-globulin reached 808 mg/g wet beads, which is nine times higher than that of non-grafted ion-exchange beads. In a batch kinetics experiment, γ-globulin achieved adsorption equilibriums rapidly (within 10 min). This finding indicates that the protein was involved in a distinct adsorption mechanism during the protein binding to surface-grafted polymer chains. The results demonstrated that polymer-grafted ion-exchange beads prepared by SI-ATRP possess a high adsorption capacity and rapid kinetics. Thus, these beads are expected to be highly useful as novel chromatographic materials for protein purification.