Giant unilamellar vesicle formation technique allows study of membrane-bound biological systems

Giant unilamellar vesicles (GUVs) are simple proxies for studying the complex dynamics of proteins bounded by membranes. However, for GUVs to better represent biological membranes, the vesicles need to be filled with a different solution from what they are suspended, and creating these types of asymmetric vesicles is challenging. By using focused acoustic waves to create a liquid jet in front of a lipid bilayer, Armstrong et al. developed a new way to form GUVs.

The group’s technique currently makes GUVs between 50 and over 400 microns in diameter, though this range could be expanded by altering the acoustic wavelength. They demonstrated its ability to load solutions into GUVs by encapsulating polystyrene beads suspended in water.

To fabricate the GUVs, the researchers placed an acrylic divider between two chambers, one filled with the fluid that will surround the GUV, the other with the fluid that will be inside the GUV. They used an acoustic jet formed by focused acoustic waves to deform a lipid bilayer suspended across a hole in the divider into a vesicle in the surrounding solution.

“By setting up the lipid bilayer in a planar configuration with the divider, we’re able to separately access each side of the bilayer. That means we can incorporate different lipids or proteins in each leaflet of the bilayer independently before using the acoustic jet to make the GUV,” said author Daniel Fletcher. “With this technique, we would like to explore how lipid asymmetry affects the movement and organization of transmembrane proteins.”

The group is working on improving the robustness, ease-of-use, and efficiency of their method.

Source: “Forming and loading giant unilamellar vesicles with acoustic jetting,” by Maxim Armstrong, Michael D. Vahey, Thomas P. Hunt, and Daniel A. Fletcher, Biomicrofluidics (2020). The article can be accessed at https://doi.org/10.1063/5.0021742 .