Giant Unilamellar Vesicles Formed by Hybrid Films of Agarose and Lipids Display Altered Mechanical Properties

Abstract

Giant unilamellar vesicles (GUVs) are presumably the current most popular biomimetic membrane model. Preparation of GUVs in physiological conditions using the classical electroformation method is challenging. To circumvent these difficulties, a new method was recently reported, by which GUVs spontaneously swell from hybrid films of agarose and lipids. However, agarose is left encapsulated in the vesicles in different amounts. In this work, we thoroughly characterize the mechanical properties of these agarose-GUVs in response to electric pulses, which induce vesicle deformation and can lead to membrane poration. We show that the relaxation dynamics of deformed vesicles, both in the presence and absence of poration, is significantly slowed down for agarose-GUVs when compared to agarose-free GUVs. In the presence of poration, agarose polymers prevent complete pore closure and lead to high membrane permeability. A fraction of the vesicles were found to encapsulate agarose in the form of a gel-like meshwork. These vesicles rupture and open up after electroporation and the meshwork is expelled through a macropore. When the agarose-GUVs are heated above the melting temperature of agarose for 2 h before use, vesicle response is (partially) recovered due to substantial release of encapsulated agarose during temperature treatment. Our findings reveal potential artifactual behavior of agarose-GUVs in processes involving morphological changes in the membrane as well as poration.

Hydrogel-assisted functional reconstitution of human P-glycoprotein (ABCB1) in giant liposomes

“…1B. Formation of liposomes from a film of ultra-low melting agarose hence led to giant liposomes with comparable, low-permeability-characteristics than liposomes prepared by other methods [55,58]. …”

“…It remains to be seen if similar problems of leakiness will appear with reconstituted proteins other than P-gp or if this problem was protein-specific. Recently Lira et al reported that liposomes, which were also formed from films of agarose and were initially tight, became permeable to solutes upon transient pore formation by electroporation [58]. The authors explained this effect by trapping of agarose molecules in the membrane pores and a resulting attenuation of spontaneous pore closure.…”

Essential oil-mediated glycerosomes increase transdermal paeoniflorin delivery: optimization, characterization, and evaluation in vitro and in vivo

“…This effect might be due to the improvement in the concentration of hydrophilic drugs in the inner water phase by the reversephase evaporation method, leading to the formation of large unilamellar vesicles. 35,36 In the uniform design, the EE was improved by increasing the phospholipid concentration in experimental formulations. Similar findings were previously reported by Shen et al and Fang et al 17,37 Glycerosomes are a kind of closed vesicles with a lipid bilayer structure similar to the biomembrane.…”

Optical Microscopy of Giant Vesicles as a Tool to Reveal the Mechanism of Action of Antimicrobial Peptides and the Specific Case of Gomesin

“…Hydration of a lipid film on a polymer cushion (of agarose [75] and of polyvinyl alcohol, PVA [76]) allows production of GUVs of virtually all membrane compositions in all kinds of aqueous solution. However, difficulties in detaching the formed GUVs from PVA films were reported [76], and GUVs grown on agarose films were shown to have a significant amount of encapsulated agarose that interfere with the vesicle mechanical properties [77].…”