Over the past few years, we have developed UV-grafting techniques to prepare ion exchange membranes with protein binding capacities approaching or exceeding 200 mg/mL of membrane volume, potentially enabling true membrane chromatography. In a particularly successful approach, we’ve utilized the hydrogen abstracting ability of benzophenone derivatives to graft ionic monomers out of water from a variety of membrane substrates. We utilize these grafted membranes for the purification of biopharmaceutical proteins, such as monoclonal antibodies. Through detailed studies of ligand monomer structure and the variables involved in the grafting process, we’ve developed an understanding of how graft polymer architecture affects protein binding ability. For instance, we find that a long spacer arm (<u>&gt;</u> 6 atoms) between the ionic ligand group and the polymerizable double bond of the monomer results in graft polymers that interact more efficiently with proteins (i.e., molar ratio of ionic groups to protein molecules is smaller) than for monomers with shorter spacer arms. This type of spacer effect has not been seen previously for ion exchange type interactions, whereas we see it to be generally applicable to both anion exchange and cation exchange. Finally, somewhat out of frustration with our inability to gain a better understanding of the molecular weight and MW distribution of our grafted chains, we have recently developed a very simple technique for attaching controlled radical initiators to polymer substrates, in the hopes that we could more effectively control the grafting process and subsequently relate that to protein binding efficiency.

UV-grafting and the impacts of monomer structure on ion-exchange membrane performance

2019 Spring National Meeting

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