Characterisation of lipid distribution across membrane leaflets in asymmetric lipid vesicles

Extracellular vesicles (EVs) are key mediators in the fundamental processes of communication and transfer of material between cells. These lipid membrane-bound nanoparticles are produced by cells, and are innately biocompatible, with huge potential in therapeutics and diagnostics. Like cells, they are postulated to possess lipid asymmetry across the membrane bilayer, i.e. the inner and outer membrane leaflets have chemically distinct compositions.
We are developing vesicles with asymmetric distributions of lipids across the membrane, which mimic the lipid compositions found in EVs and can be applied as model systems to study the role of lipid composition in EV structure and function. In this beamtime we will study these asymmetric vesicles, formulated to include leaflet-localised deuterated lipids, which will allow the extent of asymmetry to be established via contrast variation. We will also characterise sub-populations within samples by offline separation via AF4. The results will allow us to quantify lipid distribution and dynamic lipid rearrangement processes in EV-mimicking asymmetric vesicles, at conditions mimicking intercellular environment. Knowlege of this nature is crucial in the study of the effect of lipid membrane asymmetry on uptake of such vesicles by cells. Being able to characterise heterogeneity within populations is also a critical step forward in studying the physiological roles of EVs, which contain mixtures of different vesicle populations.