Phase behavior of fluorocarbon di-O-alkyl-glycerophosphocholines and glycerophosphoethanolamines and long-term shelf stability of fluorinated liposomes.
This paper is devoted to the morphological characterization, by freeze-fracture electron microscopy, and to the thermotropic phase behavior, by differential scanning calorimetry and X-ray diffraction of the aqueous dispersions of various fluorocarbon/fluorocarbon or mixed fluorocarbon/hydrocarbon 1,2- or 1,3-di-O-alkyl-glycerophosphocholines (PC) and 1,2-di-O-alkyl-glycerophosphoethanolamines (PE). The fluorinated PCs form classical lamellar phases and liposomes while an interdigitated lamellar phase has been evidenced for a hydrocarbon 1,3-analog. The fluorinated PEs display a lamellar to hexagonal phase transition which occurs almost simultaneously with the gel-to-fluid lamellar phase transition. The impact of each of the structural features [ether vs ester chemical junction connecting the hydrophobic chains on glycerol, their position (1,2- vs 1,3 isomers), number and length of the perfluoroalkylated chains, length of the fluorinated tail and hydrocarbon spacer, PC vs PE polar head] of the fluorinated phospholipids on the phase transition thermodynamic parameters (Tc, delta H, delta S) is discussed. Most of the liposomes formed from the fluorinated ether-PCs display a remarkable long-term shelf stability: they can be thermally sterilized and stored at room temperature for several months without any significant modification of their size and size distribution.
Ravily
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V
Laboratoire de Chimie Moléculaire, URA CNRS 426, Faculté des Sciences, Université de Nice-Sophia Antipolis, Nice, France.
Santaella
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C
Vierling
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P
Gulik
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A
D002152:Calorimetry, Differential Scanning; D005466:Fluorocarbons / Q000737:chemistry*; D005614:Freeze Fracturing; D005997:Glycerylphosphorylcholine / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D008854:Microscopy, Electron / Q000379:methods; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D013816:Thermodynamics; D014961:X-Ray Diffraction
D005466:Fluorocarbons; D008081:Liposomes; D010714:Phosphatidylethanolamines; C002449:glycerophosphoethanolamine; D005997:Glycerylphosphorylcholine