Odudimu, A. T. | bioRxiv Science

bioRxiv2026

Domain Dissolution in Supported Lipid Bilayers Triggered by Unsaturated Phospholipid Addition

Significant cellular processes, including protein sorting, signal transduction, and pathogen entry, amongst others, are associated with membrane microdomains, also known as lipid rafts. Lipid rafts, due to their unique biophysical properties compared to their surrounding environment, which stem from their distinct lipid and protein profiles, have garnered interest in methods and techniques that tune their coexisting liquid-ordered/liquid-disordered state, aiming to disrupt or destabilize them. Since cholesterol stabilizes the membrane domain, cholesterol-depleting compounds like cyclodextrin can be used to destabilize and disrupt the membrane rafts. Overall, given the membrane rafts importance in biological processes, it is crucial to understand the biophysical factors that influence its stability. In this study, we present a new method for disrupting and dissolving lipid rafts in a model system of phase-separated supported lipid bilayer (SLB) patches composed of DOPC, DPPC, and cholesterol. Using fluorescence microscopy to monitor the liquid ordered (Lo) and liquid disordered (Ld) phases of the SLB patches, we observed that adding DOPC liposomes causes a transformation of the co-existing Ld and Lo phases into a single-phase bilayer. On the other hand, adding liposomes that match the lipid content of the phase-separated SLB patch increase the areas of the existing Ld and Lo phases. This work also offers a new method for redistributing raft-localized molecules, confirmed by tracking the redistribution of cholera toxin bound to GM1 after domain dissolution with DOPC liposomes. The work describes an alternative method for dynamically altering membrane composition and dissolving domains via liposome addition, rather than lipid depletion or exchange.

biophysics↗

bioRxiv2024

Chaotropic Agent-assisted Supported Lipid Bilayer Formation

Supported lipid bilayers (SLBs) are useful structures for mimicking cellular membranes, and they can be integrated with a variety of sensors. While there are a variety of methods for forming SLBs, many of these methods come with limitations in terms of the lipid compositions that can be employed and the substrates upon which the SLBs can be deposited. Here we demonstrate the use of an all-aqueous chaotropic agent exchange process that can be used to form SLBs on two different substrate materials: SiO2, which is compatible with traditional SLB formation by vesicle fusion and Al2O3, which is not compatible with vesicle fusion. When examined with quartz crystal microbalance with dissipation monitoring, the SLBs generated by chaotropic agent exchange (CASLBs) have similar frequency and dissipation shifts to SLBs formed by the vesicle fusion technique. The CASLBs block nonspecific protein adsorption on the substrate and can be used to sense protein-lipid interactions. Fluorescence microscopy was used to examine the CASLBs, and we observed long-range lateral diffusion of fluorescent probes, which confirmed the CASLBs were composed of a continuous, planar lipid bilayer. Our CASLB method provides another option for forming planar lipid bilayers on a variety of surfaces, including those that are not amenable to the widely used vesicle fusion method.

biophysics↗