(45a) Innovative Lipid Carriers for Developing Biomimetic Desalination Membranes

Desalination membranes are crucial for addressing global water scarcity; however, synthetic membranes often encounter challenges such as low permeability and high energy consumption¹. In contrast, biologically derived aquaporins (AqpZ) provide high permeability, selective transport, and frictionless water flow, making them a promising platform for the development of highly efficient desalination membranes². A common strategy for incorporating AqpZ into synthetic membranes involves stabilizing it within vesicular structures, typically made from lipids or synthetic amphiphilic block copolymers. However, the random localization of AqpZ channels in these vehicles, along with disrupted transport pathways and opposing osmotic gradients, can limit their ability to enhance permeability in biomimetic membranes.

Here, we employed lipid carriers (LCs) to stabilize and incorporate AqpZ channels into synthetic membranes. Their structure enables direct water transport through AqpZ, avoiding the tortuosity caused by vesicular structures. Additionally, their versatile design allows precise control over size, composition, and functional modifications.

To achieve this, we first reconstitute AqpZ proteins into lipid particles. These stabilized channel proteins are then incorporated into the polyamide (PA) layer through interfacial polymerization (IP) to produce membranes. The pH of the aqueous phase in the IP process is adjusted to approximately 8 to ensure biocompatibility with the protein solution. The separation performance of LCs-based membranes is compared with that of membranes developed using block copolymeric vesicles made of poly(methyloxazoline)-polybutadiene, which also contain aquaporins and have a diameter of approximately 100-120 nm, as determined by dynamic light scattering (DLS). These block copolymer vesicles have a bilayer thickness of roughly 5-7 nm, similar to that of a lipid bilayer (approximately 5 nm), thereby replicating the natural phospholipid-like environment of protein channels.

Microscopy images confirm the uniform distribution of LCs within the membrane matrix and the formation of the PA layer. The desalination membranes developed using AqpZ LCs exhibit 50% higher permeability compared to control membranes made from LCs without protein channels, demonstrating the crucial role of protein channels in facilitating water transport in biomimetic membranes. Additionally, a comparison of permeability and salt rejection between AqpZ-reconstituted vesicles and LCs reveals that membranes based on AqpZ-LCs exhibit superior permeability and salt rejection, owing to their enhanced water transport efficiency, which is facilitated by their structure and direct pathways for water transport. These results underscore the significant potential of AQPz-stabilized LCs in developing efficient biomimetic membranes.

Competing interests

The results presented in this abstract were submitted as part of a patent application by Vandstrom Inc.

References

1. Park, H. B., Kamcev, J., Robeson, L. M., Elimelech, M. & Freeman, B. D. Maximizing the right stuff: The trade-off between membrane permeability and selectivity. Science 356, eaab0530 (2017).

2. Fuwad, A. et al. Highly permeable and shelf-stable aquaporin biomimetic membrane based on anodic aluminum oxide substrate. Npj Clean Water 7, 1–11 (2024).