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Phospholipid Vesicles

Phospholipids, a major component of cell membranes, are amphiphilic molecules. As a consequence they self assemble in water, forming bilayers. Usually bilayers form spontaneously closed objects of various topologies. Spherical capsules formed by phospholipid bilayers are called liposomes or vesicles. Depending on their formation conditions, vesicles are categorized into Small/Large/Giant Vesicles (SV, LV, GV), with diameters sizing within the range of a few tens of nm to a few tens of µm.

Our research often focuses on Giant Unilamellar Vesicles (GUVs), of typical sizes 10-40 µm. We study various properties of GUVs using optical microscopy or confocal microscopy.

  • Traditionaly GUVs are formed using the well known ’electroformation’ technique; we have developped alternate growing methods that facilitate GUV formation, for exemple in presence of a salted buffer or when charged lipids are used.
  • Fluorescence microscopy is an ideal tool to visualize lipid domains within the bilayer. Those are the result of an in-plane phase separation between various lipid species exhibiting low affinity. As an exemple, the picture below shows the phase separation in a GUV containing DPPC, POPC and cholesterol during the POPC light-induced peroxidation (time evolution from left to right).
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  • Mechanical properties of lipid bilayers can be accessed from the Micropipette Aspiration Technique, that was used for exemple to show how lipid peroxidation decreases the bilayer stretching modulus.

Giant vesicles as observed in optical and confocal microscopy