A new purification technique is developed for obtaining distribution of giant unilamellar vesicles (GUVs) within a specific range of sizes using dual filtration. The GUVs were prepared using well known natural swelling method. For filtration, different combinations of polycarbonate membranes were implemented in filter holders. In our experiment, the combinations of membranes were selected with corresponding pore sizes–(i) 12 and 10 μm, (ii) 12 and 8 μm, and (iii) 10 and 8 μm. By these filtration arrangements, obtained GUVs size distribution were in the ranges of 6−26 μm, 5–38 μm and 5–30 μm, respectively. In comparison, the size distribution range was much higher for single filtration technique, for example, 6−59 μm GUVs found for a membrane with 12 μm pores. Using this technique, the water-soluble fluorescent probe, calcein, can be removed from the suspension of GUVs successfully. The size distributions were analyzed with lognormal distribution. The skewness became smaller (narrow size distribution) when a dual filtration was used instead of single filtration. The mode of the size distribution obtained in dual filtration was also smaller to that of single filtration. By continuing this process of purification for a second time, the GUVs size distribution became even narrower. After using an extra filtration with dual filtration, two different size distributions of GUVs were obtained at a time. This experimental observation suggests that different size specific distributions of GUVs can be obtained easily, even if GUVs are prepared by different other methods.

Sugar plays a vital role in the structural and functional characteristics of cells. Hence, the interaction of NPs with cell membranes in the presence of sugar concentrations is important for medicinal and pharmacological innovations. This study integrated three tools: giant unilamellar vesicles (GUVs), anionic magnetite nanoparticles (NPs), and sugar concentrations, to understand a simplified mechanism for interactions between the vesicle membranes and NPs under various sugar concentrations. We focused on changing the sugar concentration in aqueous solution; more precisely, sucrose inside the GUVs and glucose outside with equal osmolarity. 1,2-dioleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (sodium salt) (DOPG) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were used to prepare the charged membranes of 40mole%DOPG/60mole%DOPC-GUVs, whereas only DOPC was used to prepare the neutral membranes. Phase contrast fluorescence microscopy shows that the adherence of 18 nm magnetite NPs with anionic charge depends on the sugar concentration. The alterations of GUVs induced by the NPs are characterized in terms of i) vesicle compactness, ii) deformation, and iii) membrane poration. The presence of sugar provides additional structural stability to the GUVs and reduces the effects of the NPs with respect to these parameters; more precisely, the higher the sugar concentration, the smaller the alteration induced by the NPs. The differences in NPs effects are explained by the change in the type of interaction between sugar molecules and lipid membranes, namely enthalpy and entropy-driven interaction, respectively. In addition, such alterations are influenced by the surface charge density of the lipid bilayer. The surface pressure of membranes due to the adsorption of NPs is responsible for inducing the poration in membranes. The differences in deformation and poration in charged and neutral GUVs under various sugar concentrations are discussed based on the structure of the head of lipid molecules.

Cholesterol inhibits the anionic magnetite nanoparticles-induced deformation of charged and neutral giant lipid vesicles and lipid membrane poration of these vesicles.