Giant unilamellar vesicles or GUVs are single-walled closed phospholipid bilayer membranes that resemble minimal biological cells. This resemblance has made GUVs instrumental in advancing the understanding of, among others, membrane organization, cytoskeletal mechanics, reproduction, division, transport, and electrical signaling. Recent innovations in bottom-up synthetic biology, engineering of artificial tissues, and delivery of drugs opens new avenues for the use of GUVs in biomimetic applications. Despite their importance, a general understanding of the mechanism of GUV assembly from lamellar films on surfaces is lacking. In this talk, I will present a quantitative framework, using sedimentation and confocal microscopy, to measure the “molar yield” and distribution of sizes of GUVs. The molar yield provides a consistent metric to understand the effects of assorted physical parameters on the process of assembly. We show that the assembly of GUVs composed of zwitterionic lipids is consistent with the formation and merging of spherical nanobuds. On substrates with hydrophilic nanoscale cylindrical fibers, such as nanocellulose paper, the process is energetically favorable, and results in the highest yield and highest fraction of GUVs of large diameters among extant surface-assisted assembly techniques. For membranes composed of charged lipids, an alternate mechanism, shear-induced fragmentation of an expanded lamellar phase, also contributes to the formation of GUVs. We characterize the effect of the ionic strength of the solution on the process of assembly and develop a straightforward approach to obtain high yields of GUVs in physiological salt solutions. I will close by comparing the scalability and costs of the assorted techniques for assembly which is important for applications beyond the lab.

Quantitative measurements of yield illuminate the mechanism of formation of giant unilamellar vesicles on nanocellulose paper

ACS Spring Meeting 2021

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