Figure 3.

The sole presence of oil molecules increases the critical bilayer strain. (A) Left, illustration of the formation of triolein GUVs (To-GUVs) using a water-in-oil inverted emulsion method. The triolein was tagged with 0.05% (w/w) of triolein-NBD. Right, fluorescence confocal imaging of the resulting triolein GUVs. Significant triolein-NBD signal colocalizes with the bilayer reported by Cy5-PE. Scale bars, 5 μm. (B) Top shows three different model systems: a bilayer with no neutral lipids (GUV), a bilayer supplemented with triolein molecules (To-GUVs), and a bilayer supplemented with triolein molecules provide by a triolein droplet (To-DEVs). Bottom: to assess the concentration of triolein in the bilayer of the three model systems, we compute the “triolein in bilayer” by taking the fluorescence ratio between triolein-NBD signal/Cy5-PE signal; microscope settings were kept constant. (C) Quantification of the triolein in bilayer for GUVs (n = 6), triolein GUVs (n = 13), and triolein DEVs (n = 49) made with PC phospholipids is given. Mean ± SD. t-test shows no significant difference of triolein in bilayer between triolein GUVs and triolein DEVs. (D) Quantification of the critical bilayer strain $\left({\epsilon }_{\max }\right)$ of PC GUVs (n = 28), triolein GUVs (n = 41), and triolein DEVs (n = 29), showing higher stretching for DEVs and GUVs containing oil. Mean ± SD. (E) Plot of the critical bilayer strain $\left({\epsilon }_{\max }\right)$ for PC-PA GUVs (n = 9), triolein GUVs (n = 15), and triolein DEVs (n = 6) showing higher stretching for DEVs and GUVs containing oil. Mean ± SD. (F) Quantification of the critical bilayer strain $\left({\epsilon }_{\max }\right)$ of PC GUVs (n = 28), squalene GUVs (Sq-GUV) (n = 7), and squalene DEVs (Sq-DEVs) (n = 21), showing higher stretching for DEVs and GUVs containing oil. Mean ± SD. ***p < 0.001; **p < 0.01; *p < 0.05. To see this figure in color, go online.