Substrate-led cholesterol extraction from supported lipid membranes

Abstract

The lipid membrane is a principal building block in biology, technology and industry, where it often occurs supported by other hydrophilic structures. Interactions with the support can affect the physical behavior of the membrane from the local organization and diffusion of lipids and proteins, to phase transitions, and the local mechanical properties. In this study we show that supporting substrates textured with nanoscale hydrophilic and hydrophobic domains can modify the membrane's chemical composition by selectively extracting cholesterol molecules without affecting the remaining phospholipids. Using polydimethylsiloxane (PDMS) substrates with various degrees of plasma oxidation, we are able to trigger dramatic changes in the membrane morphology and biophysical properties, and relate them to the amount of extracted cholesterol. We also show that it is possible to control the cholesterol extraction through mechanical extension of the flexible PDMS support. Given the ubiquity of bio-substrates with textured surface properties and the wide use of PDMS we expect that our results will have implications not only in biological and chemical sciences but also in nanotechnologies such as organ on a chip technologies, biosensors, and stretchable bio-electronics.

A Study of the Effects of Plasma Surface Treatment on Lipid Bilayers Self-Spreading on a Polydimethylsiloxane Substrate under Different Treatment Times

“…Treatment times longer than 15 s resulted in the PDMS surface being completely wetted with a contact angle of <0°. These results agreed well with previous studies 27,29 and confirmed the modification of the surface chemistry. Owen and Smith 30 and Gomathi et al 34 have reported that surface oxygen content increases and carbon content decrease as plasma treatment time increases by X-ray photoelectron spectroscopy (XPS) measurement.…”

“…Plasma treatment time has been reported to strongly affect the lipid vesicle rupture dynamics 28 and the interaction between lipid bilayers and the PDMS surface. 16,29 However, few studies have focused on the effect of the surface hydrophilicity on bilayer self-spreading. In addition, plasmatreated PDMS can form a complex topography, 30 which affects the formation dynamics of self-spreading bilayers.…”

“…Plasma exposure replaces the methyl groups (−CH 3 ) on the PDMS surface with polar silanol groups (−OH), forming a hydrophilic silica-like layer, the hydrophilicity of which depends on the treatment time and plasma power. Plasma treatment time has been reported to strongly affect the lipid vesicle rupture dynamics and the interaction between lipid bilayers and the PDMS surface. , However, few studies have focused on the effect of the surface hydrophilicity on bilayer self-spreading. In addition, plasma-treated PDMS can form a complex topography, which affects the formation dynamics of self-spreading bilayers.…”

Self-assembly of small molecules at hydrophobic interfaces using group effect

“…Molecular self-assembly in biological systems often rely on such relatively weak interactions in order to create soft or fluid structures that can evolve in response to changes in the environment. 12,13 Yet, biological self-assembly usually occurs at fast rates and with high precision, making it particularly interesting although still poorly understood. 14,15 To date, the self-assembly of small molecules has primarily been studied in extreme cases where systems are under confinement 16 or at low temperatures 17 so as to force the molecules to remain long enough near the solid's surface for supramolecular structures to form.…”

Lipid exchange enhances geometric pinning in multicomponent membranes on patterned substrates

“…19 While GUVs can change shape during the phase separation process, SLBs and SLVs are scaffolded. Therefore, they can mimic the supporting property of the actin cytoskeleton in cells and allow for the fabrication of stable bilayers for atomic force microscopy (AFM) studies, [20][21][22][23][24] for applications in biosensing, 25 in cell biology, 26 and in drug delivery. 27 Experiments with GUVs have shown that there is a correlation between positioning of soft domains and bilayer curvature.…”