title: Consequences of ions and pH on the supramolecular organization of sphingomyelin and sphingomyelin/cholesterol bilayers.
abstract: For drug delivery purpose the anticancer drug S12363 was loaded into ESM/Chol-liposomes using either a pH or an ammonium gradient. Association between the drug and the liposome depends markedly on the liposome membrane structure. Thus, ESM and ESM/Chol bilayer organization had been characterized by coupled DSC and XRDT as a function of both cholesterol concentration and aqueous medium composition. ESM bilayers exhibited a ripple lamellar gel phase P(beta') below the melting temperature and adopted a L(beta)-like gel phase upon Chol insertion. Supramolecular organization of ESM and ESM/Chol bilayers was not modified by citrate buffer or ammonium sulfate solution whatever the pH (3< or = pH < or =7). Nevertheless, in ESM bilayer, ammonium sulfate salt induced a peculiar organization of head groups, leading to irregular d-spacing and weakly correlated bilayers. Moreover, in the presence of salts, a weakening of van der Waals attraction forces was seen and led to a swelling of the water layer.
authors.affiliation: Université Paris Sud, UMR CNRS 8612, Châtenay-Malabry, France. caroline.chemin@fr.netgrs.com
authors.forename: Caroline
authors.initials: C
authors.lastname: Chemin
authors.forename: Claudie
authors.initials: C
authors.lastname: Bourgaux
authors.forename: Jean-Manuel
authors.initials: JM
authors.lastname: Péan
authors.forename: Georg
authors.initials: G
authors.lastname: Pabst
authors.forename: Patrick
authors.initials: P
authors.lastname: Wüthrich
authors.forename: Patrick
authors.initials: P
authors.lastname: Couvreur
authors.forename: Michel
authors.initials: M
authors.lastname: Ollivon
mesh_terms: D000645:Ammonium Sulfate / Q000494:pharmacology*; D002152:Calorimetry, Differential Scanning; D002784:Cholesterol / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D008968:Molecular Conformation; D053838:Scattering, Small Angle; D013109:Sphingomyelins / Q000737:chemistry*; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D013109:Sphingomyelins; D002784:Cholesterol; D000645:Ammonium Sulfate