title: Thermotropic phase behavior of hydrogenated soybean phosphatidylcholine-cholesterol binary liposome membrane.
abstract: By combination of differential scanning calorimetry (DSC) and fluorescence spectroscopy of 6-propionyl-2-(dimethylamino)naphthalene (Prodan), we elucidated the thermotropic phase behavior of hydrogenated soybean phosphatidylcholine (HSPC)-cholesterol binary liposome membrane which has similar lipid composition to Doxil®, the widely used liposome product in treatment of various tumors. We found that the characteristic points at cholesterol mole fraction (Xch)=0.023 and 0.077 correspond to the hexagonal lattice, in which cholesterol molecules are considered to be regularly distributed in all regions of HSPC lipid bilayer with 1 : 42 and 1 : 12 units, respectively, as static averaged structures. Apparent endothermic peak disappeared at Xch=0.40 in the DSC thermograms, indicating the existence of single liquid ordered phase at Xch>0.40. In addition, fluorescence measurements of Prodan and its lauroyl derivative in poly(ethylene glycol) (PEG)-modified liposomes indicated that PEG modification has a negligible effect on the phase behavior of HSPC-cholesterol binary liposome membrane. These results may provide useful information in developing novel liposome products whose stability and encapsulated drug release are controlled.
authors.affiliation: Institute of Health Biosciences and Graduate School of Pharmaceutical Sciences, The University of Tokushima.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kitayama
authors.forename: Yuki
authors.initials: Y
authors.lastname: Takechi
authors.forename: Nobutake
authors.initials: N
authors.lastname: Tamai
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Matsuki
authors.forename: Chikako
authors.initials: C
authors.lastname: Yomota
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Saito
mesh_terms: D002784:Cholesterol / Q000737:chemistry*; D005453:Fluorescence; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D008566:Membranes / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*; D013025:Glycine max / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D002784:Cholesterol