Synthetic liposomes

The most important application recently developed for synthetic liposomes is as potential drug carriers for controlled release, especially for cancer chemotherapy (7). In general, the success of liposomes as vehicles for the transport of specific drugs will largely depend on their stability under physiological conditions. Unlike the naturally occurring membranes, the synthetic vesicles have very limited stability, and this is a... 

In the discussion above it has been shown that the lipid can been polymerized through UV irradiation of its aqueous suspension. The polymerization of the system improves the stability of the synthetic liposomes. Since there is an acetal linkage introduced between the polymer chain and the amphiphilic structure, this linkage can be slowly hydrolyzed in aqueous systems to separate the polymer chain from the lipid. 

In this paper two new polymerized vesicle systems have been presented. The first lipid can be polymerized in vesicle through UV irradiation. Because the second lipid contains a flexible spacer group it can be prepolymerized in benzene and then converted to vesicles by ultrasonication in water. The polymerization improves the stabilities of the synthetic liposomes. Since there is a acetal linkage between the... 

Thus, the hydrophilic head group and hydrophobic tail of lipids ensure assembly into the oriented bilayer array of cell membranes. The amphiphilic sheet, bilayer, and vesicle are now familiar mofits in biomimetic materials and structures. Synthetic liposomes are employed as biocompatible, biodegradable drug-delivery vehicles. Amphiphile assemblies may serve as templates mono-disperse nanoparticles are synthesized inside reverse micelles, and inorganic structures and materials such as ceramic tubules or mesoporous silica are formed around tubular micelles, rather as inorganics are patterned by vesicles in the formation of the exoskeletons of radiolarians and diatoms. 

Hovijitra NT, Wuu JJ, Peaker B, Swartz JR (2009) Cell-free synthesis of functional aquaporin Z in synthetic liposomes. Biotechnol Bioeng 104 40-49... 

Futai, E., Hamamoto, S., Orci, L., and Schekman, R. (2004). GTP/GDP exchange by Secl2 enables COPII vesicle bud formation on synthetic liposomes. EMBO J. 23, 4146-4155. 

Zhu, Y., Drake, M. T., and Kornfeld, S. (1999). ADP-ribosylation factor 1 dependent clathrin-coat assembly on synthetic liposomes. Proc. Natl Acad. Scl USA 96, 5013-5018. 

Molecular probes are used extensively to investigate the microenvironment polarity of lipid membranes. Synthetic liposomes and vesicles that mimic the... 

The application of modified electrodes for the assay of antibodies in senun preparations using redox indicators encapsuled into antigene marked liposomes attached to an electrode surface was suggested First model studies towards this goal make use of ferricyanide ions entrapped in synthetic vesicles. 

The presence of impurities like free fatty acids in egg or soybean phosphatidylcholine, or in the (semi)synthetic phosphatidylcholines (e.g., DMPC, DPPC, DSPC) can be detected by monitoring the electrophoretic behavior of liposome dispersions of these phospholipids in aqueous media with low ionic strength a negative charge will be found on these liposomes when free fatty acids are present in the bilayers. 

Stability of liposomes on storage, in Targeting of Drugs with Synthetic Systems (G. Gregoriadis, J. Senior, and G. 

Artificial membrane systems can be prepared by appropriate techniques. These systems generally consist of mixtures of one or more phospholipids of natural or synthetic origin that can be treated (eg, by using mild sonication) to form spherical vesicles in which the lipids form a bilayer. Such vesicles, surrounded by a lipid bilayer, are termed liposomes. 

Liposomes — These are synthetic lipid vesicles consisting of one or more phospholipid bilayers they resemble cell membranes and can incorporate various active molecules. Liposomes are spherical, range in size from 0.1 to 500 pm, and are thermodynamically unstable. They are built from hydrated thin lipid films that become fluid and form spontaneously multilameUar vesicles (MLVs). Using soni-cation, freeze-thaw cycles, or mechanical energy (extrusion), MLVs are converted to small unilamellar vesicles (SUVs) with diameters in the range of 15 to 50 nm. ... 

Phospholipids or similar water-insoluble amphiphilic natural substances aggregate in water to form bilayer liquid crystals which rearrange when exposed to ultrasonic waves to give spherical vesicles. Natural product vesicles are also called liposomes. Liposomes, as well as synthetic bilayer vesicles, can entrap substances in the inner aqueous phase, retain them for extended periods, and release them by physical process. 

In the 1980s, polymerization was introduced to overcome the limited stability of synthetic vesicles (2-4). It was found that the stability of the polymerized vesicles was improved dramatically compared to the unpolymerized vesicle and that entrapped substances are released to a much smaller extent from polymerized liposomes than from monomeric ones. 

G. Lopez-Berestein, R. L. Juliano, K. Mehta, R. Mehta, T. McQueen, and R. L. Hopfer, Liposomes in antimicrobial therapy, in Targeting of Drugs with Synthetic Systems (NATO ASI- Series. Series A, Life Sciences V. 113) (G. Gregoriadis, J. Senior, and G. Poste, eds.), Plenum Press, New York, 1985, p. 193. 

Amongst the synthetic magnesium(II) complexes, a comparison of bis(pyridine)magnesium(II)-tetrabenzoporphyrin (26) with bis(pyridine)magnesium(II)-octamethyltetrabenzoporphyrin (10) in vitro (HeLa cells), and in vivo using liposomal delivery, showed that while (26) was more effective than (10) in cell kill, (10) had the greater tumor selectivity ([tumor]/[muscle] = 36.0 after 24 h). Zinc(II) tetrabenzoporphyrin also showed promising activity nickel(II) tetrabenzoporphyrin derivatives were inactive.117... 

Budker V, Gurevich V, Hagstrom JE, Bortzov F, Wolff JA (1996) pH-sensitive, cationic liposomes a new synthetic virus-like vector. Nat Biotechnol 14 760-764... 

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