Giant lipid vesicles, the simplest cell-like structures, are topologically closed compartments consisting of a semi-permeable flexible shell consisting of single lipid bilayer and an aqueous core encapsulating femto- to pico-liter quantities of the aqueous phase. Although water equilibrates across vesicular walls between the encapsulated core and the surrounding phase, passive permeation of solutes is strongly hindered. As a result, gradients of solute concentration are readily established. Here, using fluorescence microscopy methods we show that giant vesicles subject to salt (or salinity) gradients become unstable in the presence of glass surfaces: lysing, rupturing, and spreading at the solid surface producing laterally fluid two-dimensional supported lipid bilayers.<br/>Monitoring the vesicle destabilization process using fluorescence microscopy in real-time, we find that the dimensional and morphological transition – from three dimensional vesicles to two-dimensional lamellar supported membranes – proceeds through an interplay of symmetric and asymmetric rupture. Asymmetric rupture involves the formation of a single pore in the GUV at the contact boundary of a deflated GUV; Subsequent expansion of which drives the dimensional and the morphological transition. This mode of rupture, evident by the appearance of heart-shaped and non-spreading membrane patches at the glass surface inverts the membrane leaflets presenting the inner leaflet at the “top” membrane-water interface and the outer leaflet of the GUV assumes a proximal position at the membrane-substrate interface. The symmetric rupture, which is also evident in our data, involves pore formation at the point of contact between essentially under-formed GUVs and the underlying substrate, by contrast preserves the leaflet order and it is accompanied by lateral spreading, which we observe. Taken together, these results provide a mechanistic explanation for conditions under which membrane patches obtained by rupture of giant vesicles retain or abandon leaflet asymmetry – a fundamental property of membranes of living cells.

Stability of giant vesicles in salinity gradients

251st National Meeting (2016)

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