title: DSC and EPR investigations on effects of cholesterol component on molecular interactions between paclitaxel and phospholipid within lipid bilayer membrane.
abstract: Differential scanning calorimetry (DSC) and electron paramagnetic resonance spectroscopy (EPR) were applied to investigate effects of cholesterol component on molecular interactions between paclitaxel, which is one of the best antineoplastic agents found from nature, and dipalmitoylphosphatidylcholine (DPPC) within lipid bilayer vesicles (liposomes), which could also be used as a model cell membrane. DSC analysis showed that incorporation of paclitaxel into the DPPC bilayer causes a reduction in the cooperativity of bilayer phase transition, leading to a looser and more flexible bilayer structure. Including cholesterol component in the DPPC/paclitaxel mixed bilayer can facilitate the molecular interaction between paclitaxel and lipid and make the tertiary system more stable. EPR analysis demonstrated that both of paclitaxel and cholesterol have fluidization effect on the DPPC bilayer membranes although cholesterol has more significant effect than paclitaxel does. The reduction kinetics of nitroxides by ascorbic acid showed that paclitaxel can inhibit the reaction by blocking the diffusion of either the ascorbic acid or nitroxide molecules since the reaction is tested to be a first order one. Cholesterol can remarkably increase the reduction reaction speed. This research may provide useful information for optimizing liposomal formulation of the drug as well as for understanding the pharmacology of paclitaxel.
authors.affiliation: Department of Chemical & Biomolecular Engineering, Faculty of Engineering, National University of Singapore, Block E5, 02-11, 4 Engineering Drive 4, Singapore 117576, Singapore.
authors.forename: Lingyun
authors.initials: L
authors.lastname: Zhao
authors.forename: Si-Shen
authors.initials: SS
authors.lastname: Feng
authors.forename: Nikolai
authors.initials: N
authors.lastname: Kocherginsky
authors.forename: Iouri
authors.initials: I
authors.lastname: Kostetski
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry*; D001205:Ascorbic Acid / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D002626:Chemistry, Pharmaceutical; D002784:Cholesterol / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes; D017239:Paclitaxel / Q000008:administration & dosage / Q000737:chemistry*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D008051:Lipid Bilayers; D008081:Liposomes; D015060:1,2-Dipalmitoylphosphatidylcholine; D002784:Cholesterol; D017239:Paclitaxel; D001205:Ascorbic Acid