Description
A fundamental component of biological cells is their membrane which is constituted by lipidic bi-layer contributing to their mechanical properties and transfer processes. Similarly, Giant Unilamellar Vesicles (GUVs) are micrometer-sized (1-100 µm) droplets within a bi-layer of arranged lipids, making them an ideal candidate for quantitatively studying cell behavior, specifically ion transport through the cell membrane.
In this context, monodispersity of the GUVs, control of the bi-layer composition and throughput are key parameter in their synthesis. Here, we present a microfluidic approach using double emulsions of water in oil in water as templates for the GUVs.
With a non-embedded co-flow-focusing configuration for microfluidic droplet generation, called RayDrop, we generate in water octanol-shell (oil phase) double emulsions of controlled thickness by tuning the flow-rates during generation. For thin shells (1-2 µm), such objects eventually collapse at rest. By using a lipid-octanol mixture instead, we observe that octanol de-wets after few minutes and separates from the droplet, leaving an extra-thin shelled object.
We show that the templates can remain stable for several days and that de-wetting of the octanol from the shell can be triggered by external medium change. We explore the influence of dilution of the templates suspension caused by the medium change. We also investigate the effect of octanol-saturation in the outer medium surrounding the templates and its effect on de-wetting. We then rationalize the drainage dynamics leading to de-wetting in the context of the lubrication theory.
Regarding the extra-thin shelled object resulting from the de-wetting, preliminary mechanical and osmotic tests show a membrane-like behavior. Moreover, With the adequate shell composition, one can also induce ion transport phenomenon through said membrane. In addition, using the RayDrop, we access a large range of template sizes.
The above make this microfluidic approach a straightforward and simple strategy towards the fabrication of monodisperse size-controlled GUVs with customizable membrane-composition.