In situ X-ray and neutron diffraction study of lipid membrane swelling
European Synchrotron Radiation Facility (ESRF), BP. 220, 13043 Grenoble, France
2 MediGene AG, Lochhamer Str. 11, 82152 Martinsried, Germany
3 Institute Laue-Langevin (ILL), BP. 156, 38042 Grenoble, France
4 Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
Liposome suspensions comprising the synthetic cationic lipid DOTAP, the zwitterionic DPPC and the anti-cancer agent Paclitaxel were deposited on solid substrates and investigated by X-ray and neutron reflectivity measurements at ESRF and ILL. Well ordered multilamellar drug/lipid membranes were obtained, such as indicated by the several orders of Bragg reflections in the diffraction pattern. With an excess of Paclitaxel, additional Bragg peaks from the drug crystalline phase could be observed. Changes of the molecular organization in the drug-lipid system were investigated as a function of relative humidity using a custom-built controlled humidity chamber. For DOTAP multilayers the effects of bilayer swelling were much more pronounced than for DPPC under similar conditions, while the crystalline peaks of the drug were not affected. The pronounced swelling of DOTAP multilayers might be related to the electrostatic repulsion between the charged lipid headgroups.
© EDP Sciences, Springer-Verlag, 2007