(318e) Mechanistic Insights into cell-sized giant liposome assembly

Giant unilamellar vesicles (GUVs) are single-walled phospholipid bilayer membranes that resemble minimal biological cells. GUVs are useful as model biophysical systems, as chassis for bottom-up synthetic biology, and in biomedical applications. However, a general understanding of the mechanism of GUV assembly from lamellar lipid films on surfaces is lacking. Our group has developed a quantitative framework using sedimentation, confocal microscopy, and image analysis to reproducibly measure the “molar yield” and distribution of sizes of GUVs. The molar yield provides a quantitative metric to understand the effects of physical variables on the process of assembly. Using the quantitative data, we propose a thermodynamically-motivated budding and merging (BNM) model. The model explains the evolution of yields as a function of i) the substrate geometry, ii) increasing surface concentration of lipid, iii) increasing ionic strength of the solution, and iv) time. On inclusion of lipids with charged headgroups or biomedically-relevant PEGylated modified lipids, a distinctly different mechanism of assembly that involves the formation of a bulk lamellar mesophase that breaks apart into GUVs occurs. The mechanistic insights allow the scalable assembly of GUVs for applications as minimal tissue and cell mimics.