Influence of the nature of the sterol on the behavior of palmitic acid/sterol mixtures and their derived liposomes.
The phase behavior of mixtures formed with palmitic acid (PA) and one of the following sterols (dihydrocholesterol, ergosterol, 7-dehydrocholesterol, stigmasterol and stigmastanol), in a PA/sterol molar ratio of 3/7, has been characterized by IR and (2)H NMR spectroscopy at different pH. Our study shows that it is possible to form liquid-ordered (lo) lamellar phases with these binary non-phospholipid mixtures. The characterization of alkyl chain dynamics of PA in these systems revealed the large ordering effect of the sterols. It was possible to extrude these systems, using standard extrusion techniques, to form large unilamellar vesicles (LUVs), except in the case of ergosterol-containing mixture. The resulting LUVs displayed a very limited passive permeability consistent with the high sterol concentration. In addition, the stability of these PA/sterol self-assembled bilayers was also found to be pH-sensitive, therefore, potentially useful as nanovectors. By examining different sterols, we could establish some correlations between the structure of these bilayers and their permeability properties. The structure of the side chain at C17 of the sterol appears to play a prime role in the mixing properties with fatty acid.
Department of Chemistry, Université de Montréal, Centre Ville, Montréal, Québec, Canada H3C 3J7.
Zhong-Kai
ZK
Cui
Guillaume
G
Bastiat
Chester
C
Jin
Amir
A
Keyvanloo
Michel
M
Lafleur
D008081:Liposomes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D019308:Palmitic Acid / Q000737:chemistry*; D013261:Sterols / Q000737:chemistry*
D008081:Liposomes; D013261:Sterols; D019308:Palmitic Acid