Phase behavior of fluorocarbon di- O-alkyl-glycerophosphocholines and glycerophosphoethanolamines and long-term shelf stability of fluorinated liposomes

• Published in: Biochimica et biophysica acta 1997-02, Vol.1324 (1), p.1-17
• Main Authors: Ravily, Véronique, Santaella, Catherine, Vierling, Pierre, Gulik, Annette
• Format: Article
• Language: English
• Subjects: Calorimetry, Differential Scanning; Fluorinated liposome; Fluorocarbons - chemistry; Freeze Fracturing; Glycerylphosphorylcholine - chemistry; Liposomes - chemistry; Membrane; Microscopy, Electron - methods; Perfluoroalkylated phospholipid; Phosphatidylethanolamines - chemistry; Polymorphism; Shelf-stability; Thermodynamics; Vesicle; X-Ray Diffraction
• ISSN: 0005-2736; 0006-3002; 1879-2642
• DOI: 10.1016/S0005-2736(96)00203-9

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, ΔH, ΔS) 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.