Ultrahigh yields of giant vesicles obtained through mesophase evolution and breakup

Abstract

Self-assembly odry amphiphilic lipid films on surfaces upon hydration is a crucial step in the formation of cell-like giant unilamellar vesicles (GUVs). GUVs are useful as model biophysical systems, as chassis for synthetic biology, and in biomedical applications. Here via combined quantitative measurements of the molar yield and distributions of sizes and high-resolution imaging of the evolution of lipid films on surfaces, we report the discovery of a previously unknown pathway for the assembly of GUVs which can lead to ultrahigh yields of > 50 %. This yield is about 60 % higher than any GUV yield reported to date. The "shear-induced fragmentation" pathway occurs in membranes containing 3 mol % of the poly(ethylene glycol) modified lipid PEG2000-DSPE (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000]), when a lipid-dense foam-like mesophase forms upon hydration. The membranes in the mesophase fragment and close to form GUVs upon application of fluid shear. Experiments with varying mol % of PEG2000-DSPE and with lipids with partial molecular similarity to PEG2000-DSPE show that ultrahigh yields are only achievable under conditions where the lipid-dense mesophase forms. The increased yield of GUVs compared to mixtures without PEG2000-DSPE was general to other flat supporting surfaces such as stainless steel sheets and to various lipid mixtures. Since FDA-approved liposomal and lipid nanoparticle formulations use PEG2000-DSPE, these results provide a useful route to obtaining ultrahigh yields of GUVs that are suitable for biomedical applications.