LUVs — large unilamellar

LUVs Large unilamellar vesicles 100-1000 nm, large trapped volume ... 

Suv, small unilamellare vesicles luv, large unilamellare vesicles mlv, multilamellare vesicles mvv, multivesiculare vesicles (Fig. 4 from [1.34]). 

SUV = small unilamellar liposomes, LUV = large unilamellar liposomes. 

Fig. 5. Types of liposomes SUV, small unilamellar vesicle LUV, large unilamellar vesicle MLV, multilamellar vesicle MW, multivesicular vesicle...

FIGURE 39.1 Approximate size ranges for the commonly used colloidal dmg delivery systems. SUV = small unilamellar vesicle LUV = large unilamellar vesicle MLV = large multilamellar vesicle MW = multivesicular vesicle. 

Abbreviations SUV, Unilamellar vesicles LUV, Large unilamellar vesicles MLV, Multilamellar vesicles. 

Fig. 21 Phase-contrast photographs of a fusion of LUVs (large unilamellar vesicles) prepared form a 1 1 mixture of a butadiene lipid with a cationic dimethylammonium bromide headgroup and cholesterol. Vesicle diameter 37 and 45 pm respectively ...

Figure 2. Left Schematic drawing of a unilamellar bilayer vesicle. Right Sketches of vesicles and liposomes of different size. The following abbreviations are commonly used MLV multilamellar vesicles, LUV large unilamellar vesicles, lUV intermediate unilamellar vesicles, SUV small unilamellar vesicles.

Liposomes are formed due to the amphiphilic character of lipids which assemble into bilayers by the force of hydrophobic interaction. Similar assemblies of lipids form microspheres when neutral lipids, such as triglycerides, are dispersed with phospholipids. Liposomes are conventionally classified into three groups by their morphology, i.e., multilamellar vesicle (MLV), small unilamellar vesicle (SUV), and large unilamellar vesicle (LUV). This classification of liposomes is useful when liposomes are used as models for biomembranes. However, when liposomes are used as capsules for drugs, size and homogeneity of the liposomes are more important than the number of lamellars in a liposome. Therefore, "sized" liposomes are preferred. These are prepared by extrusion through a polycarbonate... 

In model systems for bilayers, one typically considers systems which are composed of one type of phospholipid. In these systems, vesicles very often are observed. The size of vesicles may depend on their preparation history, and can vary from approximately 50 nm (small unilamellar vesicles or SUVs) up to many pm (large unilamellar or LUV). Also one may find multilamellar vesicular structures with more, and often many more than, one bilayer separating the inside from the outside. Indeed, usually it is necessary to follow special recipes to obtain unilamellar vesicles. A systematic way to produce such vesicles is to expose the systems to a series of freeze-thaw cycles [20]. In this process, the vesicles are repeatedly broken into fragments when they are deeply frozen to liquid nitrogen temperatures, but reseal to closed vesicles upon thawing. This procedure helps the equilibration process and, because well-defined vesicles form, it is now believed that such vesicles represent (close to) equilibrium structures. If this is the case then we need to understand the physics of thermodynamically stable vesicles. 

DSPC/Chol (55 45) LUVs (diameter = 100 nm) are prepared as described in section Preparation of Sphingomyelin/Cholesterol (55 45) Large Unilamellar Vesicle by Extrusion [(Lipid) = 20 mM, volume = 5mL], using 350 mM citrate pH 4.0 as the hydration buffer, and 20 mM HEPES 1.50 mM NaCl pH 7.5 (HEPES-buffered saline) as the external buffer. In this case, the pH gradient is formed during the final dialysis step. It would also be possible to omit the final dialysis step and form the pH gradient by one of two common column methods. This could be desirable if the LUV... 

Figure 2 (A) Effect of incubation temperature on uptake of doxorubicin into 200 nm EPC/cholesterol (55 45 mol/mol) large unilamellar vesicles (LUVs) exhibiting a transmembrane pH gradient (pH 4 inside, 7.8 outside). Doxorubicin was added to LUVs (D/L = 0.3 wt wt) equilibrated at 21°C, 37°C, and 60°C. (B) Effect of cholesterol on the uptake of doxorubicin at 20 into lOOnm LUVs exhibiting a transmembrane pH gradient (pH 4.6 inside, 7.5 outside). Lipid compositions were EPC and EPC/cholesterol (1 1 mol/mol). The initial drug-to-lipid ratio was 100 nmol/pmol. Source Prom Refs. 12 (A), 21 (B).

Encapsulation efficiencies are listed as a function of ethanol concentration for distearoyl-phosphatidyl-choline/choles-terol/l,2-dioleoyl-3-dimethylammoniumpropane large unilamellar vesicle (LUVs). The initial oligonucleotide-to-lipid ratio was 0.034 mol/mol (0.3mg/mg). The LUVs used for these experiments were 99 22 nm in size. The encapsulation values are given as mean SD. 

Liposomes consist of many phospholipid bilayers of only few, or just one bilayer (Fig. 5). Therefore multilamellar vesicles (MLV), oligolamellar vesicles (OLV), small unilamellar (SUV), and large unilamellar vesicles (LUV) have to be distinguished. Furthermore, multivesicular liposomes (MVL) may be formed. 

Figure 9.21 Various types of vesicles/liposomes, the so-called small unilamellar vesicles, SUV the large unilamellar vesicles, LUV the multilamellar vesicles, MLV...

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