Dipalmitoyl phosphatidylcholine liposomes

Cantrell et al. (2003) studied the quenching of 02 by several dietary carotenoids in dipalmitoyl phosphatidylcholine (DPPC) unilamellar liposomes. These workers used water soluble and lipid soluble 02 sensitizers so that a comparison of the efficiencies of quenching 02 generated within and outside the membrane model could be made. Perhaps surprisingly there was little difference in the efficiency of quenching in either situation. Typical results are presented in Table 14.3 (taken from Cantrell et al. (2003 and 2006)). 

Liposomes were first proposed for drug topical administration to the skin more than 25 years ago by Mezei and Gulusekharam [1,2]. The basic components of liposomes are phospholipids (phosphatidylcholine, phophatidylethanolamine, phophatidylserine, dipalmitoyl phosphatidylcholine, and others), cholesterol, and water. Liposomes may vary significantly in terms of size (from tens of nm to microns) and structure. In liposomes, one or more concentric bilayers surround an aqueous core generating small or large unilamellar vesicles (SUV, LUV) or multilamellar vesicles (MLV), respectively [3]. 

Muramatsu, K., et al. 1994. Effect of soybean-derived sterol and its glucoside mixtures on the stability of dipalmitoyl-phosphatidylcholine and dipalmitoylphosphatidylcholine/cholesterol liposomes. Int J Pharm 107 1. 

Liposomes made of pure phospholipids will not form at temperatures below T of the phospholipid. This temperature requirement is reduced to some extent, but not eliminated, by the addition of cholesterol (17). In some cases, it is recommended that liposome preparation be carried out at temperatures well above T of the vesicles. For instance, in the case of vesicles con-taining dipalmitoyl phosphatidylcholine (DPPC, T = 41°C), it has been suggested that the liposome preparation procedure be carried out at 10°C higher than the T at 51°C (18, 19). This is in order to make sure that all the phospholipids are dissolved in the suspension medium homogenously and have sufficient flexibility to align themselves in the structure of lipid vesicles. Following termination of the preparation procedure, usually nanoliposomes are allowed to anneal and stabilize for certain periods of time (e.g. 30-60 min), at a temperature above T, before storage. 

Synonyms L-a-1,2-Dipalmitoyl phosphatidylcholine DPPC Uses Emulsifier, solubilizer for dermatology and cosmetics for mfg. of liposomes and mixed micelles Manuf./Distrib. Genzyme http //www.genzyme. com Trade Name Synonyms Phospholipon PC t[Am. Lecithin... 

The use of lipid transfer proteins as tools for manipulating the composition of membranes is very promising. This has been done by incubating dipalmitoyl phosphatidylcholine or dioleoylphosphatidyl-choline with mitochondria (Guerbette et al., unpublished). The fatty acid composition of mitochondria was modified after incubation since palmitic or oleic acid became more abundant. This is due to an exchange of mitochondrial phosphatidylcholine with the liposomal one. It will be of interest to study the effects of the replacement of lipids on the functions of mitochondrial membranes. 

Materials. Egg phosphatidylcholine (PC), bovine brain phosphatidylserine (PS) were obtained from Avanti Polar Lipids Inc. (Birmingham, AL) and cholesterol was from Sigma (St. Louis, MO). Ganglioside GMj, bovine, was obtained from Calbiochem (San Diego, CA). Diethylenetriamine pentaacetic acid distearylamide complex (DPTA-SA) was synthesized according to ref. 17 and nlIn-DTPA-SA was prepared as described (7). This lipophilic radiolabel is not transferred to the serum components from liposomes (unpublished data), nor is it rapidly metabolized in vivo (7). The synthesis of N-(glutaryl)phosphatidylethanolamine(NGPE) has been described (18). Dipalmitoyl deoxyfluorouridine(dpFUdR) was synthesized as described (24). 

Figure 3 Design of a diepitope liposomal construct. Small unilamellar liposomes (PC/PG/Chol 55/25/50 molar ratio diameter 100nm) containing 10mol% of bromo-acetyl l,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine and 10mol% of the thiol-reactive lipopeptide adjuvant anchor Pam3CysAlaGly-Mal were reacted, at 25°C successively at pH 6.5, with the T-helper epitope QYI, derivatized with a C-linker at its N-terminus, followed at pH 9.0 by the B-epitope TPE derivatized with a CG linker at its N-terminus. Abbreviations PC, phosphatidylcholine PE, phosphatidylethanolamine SUV, small unilamellar vesicles. Source From Refs. 11, 20, 21.

Abbreviations DMPC, DPPC, DSPC, dimyristoyl-, dipalmitoyl-,distearoyl-phosphatidylcholine DPPA, dipalmitoylphosphatidic acid PE, phosphatidylethanolamine PS, phosphatidylserine (U) and (M), unilamellar and multilamellar liposomes temperature of crystal liquid-crystal transition Diff. spectr., difference spectroscopy. 

---