Liposomal vesicles

Barenholz, Y., Amselem, S., and Lichtenberg, D. (1979). A new method for preparation of phospholipid vesicles (liposomes). French press, FEES Lett.. 99, 210-214. 

D. (1978). Effect of lipid vesicle (liposome) encapsulation of methotrexate on its chemotherapeutic efficacy in solid rodent tumors. Cancer Res., 38, 2848-2853. 

Szoka, F., and Papahadjopoulos, D. (1980). Comparative properties and methods of preparation of lipid vesicles (liposomes), Ann. 

Nagata, T., Okabe, K., Takebe, I. and Matsui, C. (1981). Delivery of tobacco mosaic virus RNA into plant protoplasts mediated by reverse-phase evaporation vesicles (liposomes). Mol. Genet. Genomics 184, 161-5. 

The most commonly used polymers are the cationic lipids and polylysine chains (Figure 14.8). Cationic lipids can aggregate in aqueous-based systems to form vesicles/liposomes, which in turn... 

The content of vaccine within the small liposomes is estimated as in the section Estimation of Vaccine Entrapment in Dehydration-Rehydration Vesicles Liposomes for both microfluidized and sucrose liposomes and expressed as percentage of DNA and/or protein in the mixture subjected to freeze drying as in the section Preparation of Vaccine-Containing Small Liposomes by the Sucrose Method in the case of sucrose small liposomes or in the original DRV preparation (obtained in the section Estimation of Vaccine Entrapment in DRV Liposomes ) for microfluidized liposomes. Vesicle size measurements are carried out by PCS as described elsewhere (6,8,17). Liposomes can also be subjected to microelectrophoresis in a Zetasizer to determine their zeta potential. This is often required to determine the net surface charge of DNA-containing cationic liposomes. 

Phospholipids, when dispersed in water, may exhibit self-assembly properties (either as micellar self-assembly aggregates or larger structures). This may lead to aggregates that are called liposomes or vesicles. Liposomes are structures that are empty cells and that are currently being used by some industries. They are microscopic vesicles or containers formed by the membrane alone, and are widely used in the pharmaceutical and cosmetic fields because it is possible to insert chemicals inside them. Liposomes may also be used solubilize (in its hydrophobic part) hydro-phobic chemicals (water-insoluble organic compounds) such as oily substances so that they can be dispersed in an aqueous medium by virtue of the hydrophilic properties of the liposomes (in the alkyl region). 

Fig. 1 a-f. Various forms of surfactant aggregations in solution a Monolayer b bilayer c liquid crystalline phase (lamellar) d vesicle (liposome) e micelle f reverse micelle. (Reproduced from [39] with permission of PL Luisi)... 

Figure 5.2 Top-diagramatic representation of a detergent molecule, (a) Single tailed (b) double tailed (c) zwitterionic (d) bolamphiphilic. Bottom - different types of surfactant aggregates in solution (A) monolayer (B) bilayer (C) liquid-crystallin phase lamellar (D) normal micelles (E) cylindrical micelles (hexagonal) (F) vesicles (liposomes) (G) reversed micelles.

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

Molecules containing an ionic group and long alkyl chain(s) compose a molecular assembly such as a micell, a bilayer membrane, or a vesicle (liposome) (Fig. 4).19a) These assemblies bind reaction components by hydrophobic interaction, give a high... 

Biodegradable drug carriers composed of biopolymers or hpid membrane vesicles (liposomes) can be used to formulate protein drugs in colloidal or suspension dosage forms. These biodegradable carriers can release incorporated protein in a controlled and sustained manner. 

Is it possible to use simple bilayer vesicles (liposomes) to test the involvement of other modes of motion than lateral diffusion of lipids (e.g., motions across the bilayer that would be important in the transmission of signals from the cell interior to the external cell surface) ... 

Multidrug resistance protein 417 Multilamellar vesicles (liposomes) 392 Multiple attack concept 606 Multisubstrate enzymes, kinetics of 464 Muramic acid (Mur) 165s Murein 170,428,429s. See also Peptidoglycan Musci 29 Muscle(s)... 

SYNTHETIC COATED VESICLES LIPOSOMES IN A BASKET" [SCHEMATIC) COATING OF LIPOSOMES BY A NON-COVALENTLY LINKED POLYMERIC NETWORK... 

Structures formed by (a) detergents and (b) phospholipids in aqueous solution. Each molecule is depicted schematically as a polar head-group ( ) attached to one or two long, nonpolar chains. Most detergents have one nonpolar chain phospholipids have two. At very low concentrations, detergents or phospholipids form monolayers at the air-water interface. At higher concentrations, when this interface is saturated, further molecules form micelles or bilayer vesicles (liposomes). 

Multilayered vesicles (liposomes) formed from sonically dispersed phosphatidylcholine in the presence of 10% diacetylphosphate and 2% potassium phosphotungstate. Each vesicle has a trilaminar structure consisting of two dark layers separated by a light layer. The dark layers contain the electron-dense phosphotungstate ion the light layer corresponds to the hydrophobic interior of the bilayer. 

Several reports in the literature have indicated that transdermal delivery may be further increased by combining chemical excipients with electroporation. These investigations included macromolecules like dextrans [58], cyclodextrins [59] and even simple salts such as calcium chloride [60]. Other workers have, however, looked at encapsulation of compounds within lipid vesicles (liposomes) as potential candidates for electroporation-mediated delivery [61,62]. A fuller treatment of this combination is described in Chapter 17. 

Another way to assess ion channel conductance is to use artificial phospholipid vesicles (liposomes) as cell models. These structures (described in more detail in the next chapter) are commonly used to transport vaccines, drugs, enzymes, or other substances to target cells or organs. The vesicles, which are several hundred nanometres in diameter, do not suffer from interference from residual natural ion channel peptides or ionophores, unlike purified natural cells. A liposome model was used to test the ion transport behaviour of the redox-active hydraphile 12.36. The compound transports Na+ and the process can also be monitored using 23Na NMR spectroscopy.26 The presence of the ferrocene-derived group in the central relay allows the ion transport to be redox-controlled - oxidation to ferrocinium completely prevents Na+ transport for electrostatic reasons. Some representative data from a planar bilayer measurement is shown for hydraphile 12.36 in Figure 12.16. 

For this purpose liposomes are used as lipid phase. Unilamellar liposomes are artificial lipid bilayer vesicles. They can be considered as real model bilayer membranes as they ideally consist of a circular bilayer membrane. The hydrophobic acyl chains are assembled in the hydrophobic core of the liposome whereas the hydrophilic head groups point to the water in the inside and outside of the vesicle. Liposomes can be produced from a variety of lipids and from mixtures of lipids. This possibility allows studying the influence of membrane constituents on the partition of solutes. Kramer et al. (1997) studied the influence of the presence of free fatty acids in membranes on the partition behaviour of propranolol. The influence on a-Tocopherol in membranes on the partition behaviour of desipramine has been reported recently (Marenchino et al. 2004) using a liposome model. 

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