(4er) Rapid Self-Assembly: Biomimetic Membranes from Membrane Protein-Block Copolymer Nanosheets

Biomimetic membrane, Self-assembly, 2D hybrid material, Membrane protein channel, Block copolymer

Biomimetic and bioinspired membranes (BBMs) containing membrane protein (MP) channels and MP-mimic functionalized materials have garnered significant attention as innovative platforms to develop membrane-based separations and purification with specific solute selectivity [1]. Relative to commercial polymeric membranes, BBMs, which incorporate well-defined pore forming structures that are designed to target precise molecular selectivity based on molecular size and shape of separating molecules, could be advantageous [2]. Nevertheless, integrating MP-based membranes into current manufacturing technology for separations has remained challenging. These constraints are possibly due to the compatibility of MPs and polymeric matrices, nanoscopic defects on membranes that affect separation performance, the usage of large amounts of functionalized porous materials and time-intensive synthesis techniques. In this study, we fabricated MP-block copolymer (BCP) biomimetic membranes with three different types of pore-forming MPs with pore sizes of 0.8 nm, 1.3 nm, and 1.5 nm, respectively, for conducting targeted molecular separations. MPs were integrated into BCP matrices, poly(butadiene)-poly(ethylene oxide) terminated by carboxylic acid group (PB₁₂-PEO₈-COOH), forming two-dimensional (2D) crystals and nanosheets in a 2-hour organic solvent based self-assembly method [3]. The formation of 2D MP-BCP crystals indicate an optimized packing density of MPs into membrane matrices, which is ~2 orders of magnitude higher than that in proteoliposomes. The resulting three MP-BCP membranes manifested water permeability of ~300-2,000 (l m^-2 h^-1 bar^-1), which is one to three orders of magnitude greater water permeability than commercial nanofiltration membranes, and still maintained a tunable solute selectivity inferred from pore sizes of three MP channels [4].

To explore affordable and sustainable solutions for creating tight MP-based membranes with fewer defects, we developed defect sealing strategies to construct BBMs with a single cycle deposition of MP-BCP nanosheets. The tight defect-sealed MP membranes fabricating by the incorporation of nanoscopic defect-filling materials, photo-polymerizable diacetylene fatty acids, 23:2 Diyne PC, achieved >7-log (or >99.99999%) MS2 bacteriophage viral particle removal, exceeding 4-log removal suggested by US Environmental Protection Agency (EPA) for water treatment. Additionally, an efficient dehydration method using chemical drying agent, Hexamethyldisilazane (HMDS), to preserve and chemically-fix the structures, integrity, and functionality of BBMs under the dry conditions is investigated. The resulting dehydrated MP-based membranes exhibited high water vapor transport rate (WVTR) of ~245 g m^-2 hr^-1, greater than the requirement for breathable fabrics (60-85 g m^-2 hr^-1) [5]. The preservation of MP-based membrane under dry conditions could extend the applications of BBMs such as protective fabrics for medical protections and barriers. This approach of combining MP channels and BCPs could offer the promise of incorporating MP channels or porous structures into membrane designs and develop BBMs for efficient transport and specific molecular-based separations in both aqueous and dry conditions.

References

• Song, W., Tu, Y.M., Oh, H., Samineni, L. and Kumar, M. "Hierarchical Optimization of High-Performance Biomimetic and Bioinspired Membranes." Langmuir, 35, no. 3 (2018): 589-607.
• Tu, Y.M., Samineni, L., Ren, T., Schantz, A.B., Song, W., Sharma, S. and Kumar, M. “Prospective Applications of Nanometer-Scale Pore Size Biomimetic and Bioinspired Membranes.” Journal of Membrane Science, (2020): 118968.
• Tu, Y.M.^†, Song, W.^†, Ren, T.^†, Kumar, M. et al. "Rapid Fabrication of Precise High-Throughput Filters from Membrane Protein Nanosheets." Nature Materials, 19, no. 3 (2020): 347-354.
• Kumar, M., Ren, T., Song, W., and Tu, Y.M. "Organic Solvent Method for Preparing Membrane Protein Based Nanosheets and Membranes Based on Nanosheets." S. Patent Application, (2019)
• Oh, H.^†, Tu, Y.M.^†, Freeman, B.D., and Kumar, M. et al. "Ultrabreathable and Protective Fabrics from Nanoporous Membrane Protein-Block Copolymer Nanosheets" (In preparation)