Membrane permeability and stability of liposomes made from highly fluorinated double-chain phosphocholines derived from diaminopropanol, serine or ethanolamine

The release of encapsulated carboxyfluorescein (CF) from liposomes made from various fluorinated amido-connected double-chain phosphocholines and their membrane permeability have been investigated at 37 degrees C in buffer and in human serum. These fluorinated membranes and liposomes display lower permeability coefficients and are able to retain more efficiently encapsulated CF than any of their respective: conventional counterparts. Several of these liposomes are as effective as the first generation of liposomes based on fluorinated phosphatidylcholines, indicating that the chemical junction (ester/amide) and nature of the unit (glycerol, diaminopropanol, serine, ethanolamine) connecting the hydrophobic chains to the phosphocholine polar head have no significant effect on permeability and CF release. Our results show further that a fluorinated intramembrane layer reduces significantly the permeability of membranes in a liquid-crystalline stale, protects the liposomes from the destabilizing effects of serum, and even increases their stability (in terms of dye retention) in serum when the membranes are in the gel state. (C) 1997 Elsevier Science B.V.