Giant unilamellar vesicles, preparation

Nishimura K, Suzuki H, Toyota T, Yomo T (2012) Size control of giant unilamellar vesicles prepared from inverted emulsion droplets. J Colloid Interface Sci 376(1) 119-125... 

Fig. 5 Membrane models for NMR structure analysis, (a) An isotropic detergent micelle (left) is compared to the dimensions of lipid bilayers (right), (b) Macroscopically oriented membrane samples can be prepared on solid support, as nanodiscs, or as magnetically oriented bicelles. (c) Nomenclature and variability of liposomes small (SUV, 20-40 nm), intermediate (IUV, 40-60 nm), large (LUV, 100-400 nm), and giant unilamellar vesicles (GUV, 1 pm) multi-lamellar (MLV), oligo-lamellar (OLV) and highly heterogeneous multi-oligo-lamellar vesicles (MOLV)...

Liposomes occur in nature, but can also be easily synthesized in the laboratory. Depending on the preparation method used, whioh influenoes their size — in relation to the number of bilayer shells — and physical properties, liposomes are olassified as small unilamellar vesicles (SUVs, 25-50 nm), large unilamellar vesioles (LUVs, 100 nm to 1 pm), giant unilamellar vesicles (GUVs, 1.0-200 pm) multilamellar vesioles (MLVs, 0.1-15 pm), and multi-vesicular vesicles (MWs, 1.6-10.5 pm) the last consists of several small vesicles. Bicelles, which contain surfactant molecules in the lipid bilayer, constitute a special type of liposome. 

The electroformation method is used in a number of laboratories for studies involving individual GUVs. In comparison with earlier methods for the preparation of giant vesicles, electroformation has advantages, leading to the formation of giant unilamellar vesicles from a variety of lipids. 

In a successful preparation, giant unilamellar vesicles (diameter > 20 pm) were present at several hundreds per 50 pi aliquot of vesicle suspension (0.12 mg lipid... 

One aim in preparing giant unilamellar vesicles is their use as microreactors [8], For this application several requirements have to be fulfilled ... 

FIGURE 6.14 A fluorescence microscope image of giant unilamellar vesicles (GUVs) in water. These vesicles were prepared from the lipid DOPC (l,2-dioleoyl-sn-glycero-3-phosphocholine) and visualized by including a small proportion of fluorescent lipid in the bilayer (<0.05 mol%). 

FIGURE 6.15 A schematic demonstrating the electroformation method for giant unilamellar vesicle (GUV) preparation. Dry lipid films are rehydrated in the presence of an alternating electric field. ITO, indium tin oxide. 

Moscho A, Orwar O, Chiu DT, Modi BP, Zare RN (1996) Rapid preparation of giant unilamellar vesicles. Proc Natl Acad Sci 93(21) 11443-11447... 

The highly complex and variable composition of natural cell membranes makes them a difficult subject for experimental studies. Artificial lipid membranes have consequently been prepared and studied for many years as models of cell membranes [1,3-7], A diverse array of geometries has been developed, including small and large unilamellar vesicles, giant lipid vesicles, lipid membranes supported on solid and polymer-coated substrates, and BLMs. These have been used to study the physical and chemical properties of lipids and lipid mixtures as well as membrane-associated proteins, including reconstituted transmembrane receptors. 

Cell-sized unilamellar vesicles (about 5-50 pm in diameter) have attracted much attention as they serve as a simple model of biological cells and membranes. However, the preparation of such giant vesicles, has always been a problem. To solve it, some other methods (not based on the process of swelling of lipid films on solid surfaces) have been used [3,5]. However, these methods bring their own disadvantages, such as formation in non-aqueous solutions. 

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