Lipid vesicle adsorption versus formation of planar bilayers on solid surfaces

Abstract

The absorption and spreading behavior of lipid vesicles composed of either palmitoyloleoylphosphatidylcholine (POPC) or Escherichia coli lipid upon contact with a glass surface was examined by fluorescence measurements. Fluorescently labeled lipids were used to determine 1) the amount of lipid adsorbed at the surface, 2) the extent of fusion of the vesicles upon contact with the surface, 3) the ability of the adsorbed lipids to undergo lateral diffusion, and 4) the accessibility of the adsorbed lipids by external water soluble molecules. The results of these measurements indicate that POPC vesicles spread on the surface and form a supported planar bilayer, whereas E. coli lipid vesicles adsorb to the surface and form a supported vesicle layer. Supported planar bilayers were found to be permeable for small molecules, whereas supported vesicles were impermeable and thus represented immobilized, topologically separate compartments.

Mechanics of surface area regulation in cells examined with confined lipid membranes

“…In the initial state of an unstrained substrate (Fig. 1A), as a consequence of the preparation procedure, the bilayer contains a number of randomly distributed, adhered vesicles (14). Upon expansion, which significantly exceeds the critical rupture strain, we observe that the bilayer preserves its integrity (indicated by the homogeneous fluorescence) but the number of the vesicles decreases (Fig.…”

“…1A). A fluorescently labeled supported bilayer, composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) is prepared on a deformable polydimethylsiloxane (PDMS) substrate (14,15). For details of the preparation procedures, see Materials and Methods.…”

Single-particle kinetics of influenza virus membrane fusion

“…S1]. In these experiments, the measured diffusion coefficient for the lipid was between 0.5 and 2 m 2 /s, indicating unhindered diffusion that is indistinguishable from fluid bilayers supported on glass (21,23,24). We have thus generated a fully fluid, planar bilayer with an aqueous reservoir in the dextran, into which the contents of a fusing virion or vesicle can be released.…”

“…Supported lipid bilayers were formed on the dextran cushion from lipid vesicles, which adsorb to the hydrophilic surface and fuse among themselves until they reach critical size and rupture into a planar bilayer (22,23). In the experiments described here, liposomes containing 80% phosphatidylcholine and 20% cholesterol were made by extrusion through filters with pores of 100 nm.…”

“…Liposomes were extruded through a polycarbonate membrane filter with a pore size of 100 nm. Planar supported bilayers were formed over hydrated dextran surfaces by the vesicle-spreading method (23).…”