Abstract
Fundamental understanding of vesicle adhesion in the size range ≤ 200 nm is of major importance when addressing biologically relevant processes involving the presence of small vesicles like exosomes or endosomes. Using quartz crystal microbalance with dissipation monitoring, we investigate the correlation between vesicle deformation and eventual membrane rupture on surfaces with different adhesion levels, as well as their respective thermotropic phase transitions. In particular, phase transitions of solid-supported membranes on Au resemble the cooperative behaviour of lipid membrane transitions in bulk. In contrast, solid-supported membranes on SiO2 exhibit broadened ‘double-peak’ transitions, rendering a ‘decoupling’ effect during melting due to stronger interactions with SiO2. This paper provides a comprehensive view of the correlation between size, geometry and phase transitions observed in the layer of adsorbed lipid vesicles/membranes. It paves the way to explore structural changes on more complex biointerfaces by acoustic-based sensors.
Highlights
Lipid vesicles are self-assembled structures customarily used as model systems for cell membrane basic studies [1,2], as nanocontainers for bio-reactions [3] and in biotechnology applications such as drug delivery or biosensors [4,5]
For Large unilamellar vesicles (LUVs) on Au at T < Tm, an overshoot behaviour was observed in the dissipation signal but not on the frequency signal
In order to better visualize the adhesion strength W behind the results presented in Fig. 5, we have calculated W = wκ/Rs2 for κ ~ 10 · 10−19 J at room temperature and for two values of Rs: 70 nm (LUVs) and 30 nm (SUVs), relevant to this work
Summary
Lipid vesicles are self-assembled structures customarily used as model systems for cell membrane basic studies [1,2], as nanocontainers for bio-reactions [3] and in biotechnology applications such as drug delivery or biosensors [4,5]. When supported on solid-surfaces, they might form intact supported vesicle layers (SVLs) or eventually rupture into planar supported lipid bilayers (SLBs). The geometry of SVLs captures the volume to area ratio of the vesicles, strength of adhesion, membrane bending properties and osmotic stress within the supported layer making SVLs useful biomimetic platforms to probe membrane deformation. The latter plays an important role in biological processes such as adhesion, budding, lipid membrane exchange, fission and fusion [6,7,8]. Let us recall the free energy F expression of an adsorbed vesicle in terms of a simple model taking into account the adhesion energy, the local bending energy term and the geometrical constraints [6,11]: F
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