title: Preparation of submicron liposomes exhibiting efficient entrapment of drugs by freeze-drying water-in-oil emulsions.
abstract: A novel liposome preparation method is described as freeze-drying of water-in-oil emulsions containing sucrose in the aqueous phase (W) and phospholipids and poly(ethylene glycol)(1500) (PEG) in the oil phase (O). The water-in-oil emulsions were prepared by sonication and then lyophilized to obtain dry products. Upon rehydration, the dry products formed liposomes with a size smaller than 200 nm and an encapsulation efficiency (EE) higher than 60% for model drugs. The presence of lyoprotectant and PEG was found to be a prerequisite for the formation of liposomes with desirable properties, such as a small particle size and high EE. The lyophilates were stable and could be rehydrated to form liposomes without any change in size or EE even after a storage period of 6 months. Also, the lipophilic drug-containing FWE liposomes were stable and could be stored for at least 6 months although the liposomes containing hydrophilic drugs showed significant leakage. Based on the vesicle size and EEs of the model drugs, as well as the scanning electron micrograph (SEM) and small angle X-ray scattering (SAXS) pattern of the lyophilates, a possible mechanism for the liposome formation is proposed.
authors.affiliation: Department of Pharmacy, Jining Medical College, Sunshine City, Shandong Province, China. twangcn@yahoo.com
authors.forename: Ting
authors.initials: T
authors.lastname: Wang
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.forename: Tongyan
authors.initials: T
authors.lastname: Wang
authors.forename: Weiran
authors.initials: W
authors.lastname: Sun
authors.forename: Tiefu
authors.initials: T
authors.lastname: Li
mesh_terms: D004356:Drug Storage; D004655:Emulsions; D005612:Freeze Drying; D057927:Hydrophobic and Hydrophilic Interactions; D008081:Liposomes / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D009821:Oils / Q000737:chemistry*; D010316:Particle Size; D010743:Phospholipids / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D015203:Reproducibility of Results; D053838:Scattering, Small Angle; D012997:Solvents / Q000737:chemistry; D013395:Sucrose / Q000737:chemistry; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D004655:Emulsions; D008081:Liposomes; D009821:Oils; D010743:Phospholipids; D012997:Solvents; D014867:Water; D011092:Polyethylene Glycols; D013395:Sucrose