Phospholipid liposomes

Schott H, Schwendener RA. Synthesis and structure-activity studies in vivo of liposomal phospholipid-N -palmitoyl- and N" -hexadecyl-l-P-D-arabinofurano-sylcytosine conjugates. Anti-Cancer Drug Design 1996 11 451. 

Schott H, Schwendener RA. Synthesis of liposomal phospholipid-(N" -palmitoyl-l-P-D-arabinofuranosylcytosine)-conjugates and evaluation of their cytostatic activity against L1210 murine leukemia. Liebigs Annalen Chemie 1996 365. 

Insertion of PEG-lipid into conventional liposome phospholipid bilayer had substantially increased their circulation half-life. Pharmacokinetic of PEGylated liposome is clearly modified by the presence of the PEG-lipid extended circulation time was reported as reviewed (4). 

Hydrolysis and oxidation are the two primary degradation routes to which liposomal phospholipids are susceptible. Hydrolytic attack at the fatty acyl carbonyl will produce free fatty acids and lysophosphatides [e.g., lyso-phosphatidyl choline (LPC)]. Hydrolysis generally follows Lrst-order... 

Liposomes—Phospholipid Vesicles for Topical Administration of Drugs.255... 

LIPOSOMES—PHOSPHOLIPID VESICLES FOR TOPICAL ADMINISTRATION OF DRUGS... 

Liposomes Phospholipids and polymers Many methods used,... 

Compared with lAM, which uses a monolayer of phospholipid, the liposomal phospholipid bilayers in ILC have the advantage of closely resembling biologic membrane bilayers and constitute a 2-D fluid in which lipid molecules and other components are free to diffuse (10). With this technique, the phospholipid composition can be changed to mimic the membrane of interest. Membrane lipids extracted from human cells also can be used the technique then is called immobilized biomembrane chromatography (IBC) (11). 

Among the several drug delivery systems, liposomes - phospholipid nanosized vesicles with a bilayered membrane structure - have drawn a lot of interest as advanced and versatile pharmaceutical carriers for both low and high molecular weight pharmaceuticals. At present, liposomal formulations span multiple areas, from clinical application of the liposomal drugs to the development of various multifunctional liposomal systems to be used in therapy and diagnostics. This chapter provides a brief overview of various liposomal products currently under development at experimental and preclinical level. 

Moog R, Brandi M, Schubert R, Unger C, Massing U (2000) Effect ofnucleoside analogs and oligonucleotides on hydrolysis of liposomal phospholipids. Int J Pharm 206( 1-2) 43-53... 

SUVs have a diameter of 20 to -lOOnm while MLVs, LUVs and MVVs range in size from a few hundred nanometres to several micrometers. An average membrane of a liposome (phospholipid bilayer) measures about 7 nm. 

Phillips, N. C. and Dahman, J. (1995) Immunogenicity of immunoliposomes reactivity against species-specific IgG and liposomal phospholipids. Immunology Letters 45,149-152. 

For antibody conjugation, the liposomal phospholipid concentration needs to be determined using Bartlett assays (94) (see Subheading 3.3). Both antibodies of the matched set should be conjugated to liposomes to determine which serves as the better detection antibody. Liposomes should be mixed with antibodies with the latter at 0.05 mol% of the total lipid input. Then, just before use, dilute EDC to a concentration of lOOmg/mL with 0.1 M MES buffer, pH 4.65 then add five molar equivalents (based on total W-glutaryl DPPE lipid input) to the liposome/ antibody mixture. Note that EDC is very hydroscopic - use care... 

Liposomes Phospholipids spontaneously form bilayers called liposomes when dispersed in water. Meat and biological membranes are examples of liposomes. Hydrophilic antioxidants and prooxidants would be oriented at the polar end of the phospholipid bilayers, while the lipophilic antioxidants and prooxidants would be located between the long chain of the lecithin and the water phase. Multiphase food systems will be discussed further in Chapter 10. 

The use of the reverse phase evaporation method permits inclusion of 50 and more percent of the substance to be encapsulated from the water phase into the liposomes. Besides, a variety of methods have been developed to obtain lyophilized liposomal preparations possessing good storage stability. The in vitro release rate of different compounds from liposomes, including proteins of moderate molecular weight, is usually under 1% per hour, assuming that the incubation temperature sufficiently differs from the phase transition temperature of a given phospholipid, since the maximal permeability of liposomes is usually observed at temperatures close to the phase transition temperature of the liposomal phospholipid. In vivo, this parameter can vary within wide limits from minutes to hours and depends on the liposome membrane composition, cholesterol content, and disposition within the body. 

Aripov, T. F., Salakhutdinov, B. A., Salkihova, Z. T., Sadykov, A. S. and Tashmukhamedov, B. A., 1984, Structural changes of liposome phospholipid packing induced by cytotoxin of the central asia cobra venom, Gen. Physl. Biophys., 3 489. 

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