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The role of polymer nanolayer architecture on the separation performance of anion‐exchange membrane adsorbers: I. Protein separations
Author(s) -
Bhut Bharat V.,
Weaver Justin,
Carter Andrew R.,
Wickramasinghe S. Ranil,
Husson Scott M.
Publication year - 2011
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.23221
Subject(s) - membrane , polymer , polyelectrolyte , ion exchange , polymerization , chemical engineering , macromolecule , chemistry , materials science , polymer chemistry , biophysics , chromatography , ion , organic chemistry , biochemistry , engineering , biology
This contribution describes the preparation of strong anion‐exchange membranes with higher protein binding capacities than the best commercial resins. Quaternary amine (Q‐type) anion‐exchange membranes were prepared by grafting polyelectrolyte nanolayers from the surfaces of macroporous membrane supports. A focus of this study was to better understand the role of polymer nanolayer architecture on protein binding. Membranes were prepared with different polymer chain graft densities using a newly developed surface‐initiated polymerization protocol designed to provide uniform and variable chain spacing. Bovine serum albumin and immunoglobulin G were used to measure binding capacities of proteins with different size. Dynamic binding capacities of IgG were measured to evaluate the impact of polymer chain density on the accessibility of large size protein to binding sites within the polyelectrolyte nanolayer under flow conditions. The dynamic binding capacity of IgG increased nearly linearly with increasing polymer chain density, which suggests that the spacing between polymer chains is sufficient for IgG to access binding sites all along the grafted polymer chains. Furthermore, the high dynamic binding capacity of IgG (>130 mg/mL) was independent of linear flow velocity, which suggests that the mass transfer of IgG molecules to the binding sites occurs primarily via convection. Overall, this research provides clear evidence that the dynamic binding capacities of large biologics can be higher for well‐designed macroporous membrane adsorbers than commercial membrane or resin ion‐exchange products. Specifically, using controlled polymerization leads to anion‐exchange membrane adsorbers with high binding capacities that are independent of flow rate, enabling high throughput. Results of this work should help to accelerate the broader implementation of membrane adsorbers in bioprocess purification steps. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc.