Preparation of submicron unilamellar liposomes by freeze-drying double emulsions |
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Authors: | Ting Wang Yehui Geng Zibin Gao Jianping Zou Zhixuan Wang |
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Affiliation: | Department of Pharmaceutical Sciences, Shenyang Pharmaceutical University, P.O. Box 52, No. 103 Wenhua Road, Shenyang City, Liaoning Province 110016, PR China |
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Abstract: | A novel method is described for the preparation of sterile submicron unilamellar liposomes. The method is based on the lyophilization of double emulsions containing disaccharides as lyoprotectants in both the inner and outer aqueous phase. Using various phospholipids or mixtures of lipids as emulsifiers, the double emulsions can be prepared by a two-step emulsification, including hydrophilic agents in the inner aqueous phase or lipophilic agents in the oil phase. Then, the double emulsions are lyophilized after sterilization by passing them through a 0.22-μm pore filter. Rehydration of the lyophilized products results in liposomes with a relatively high encapsulation efficiency (for calcein, 87%; 5-fluorouracil, 19%; flurbiprofen, 93%) and a size below 200 nm measured by the dynamic light scattering technique (DLS) and the atomic force microscopy (AFM). The liposomes were found to be unilamellar from freeze-fracture electron micrographs and X-ray diffraction patterns. In addition, the liposomes can be reconstituted just before use by rehydration of the lyophilized products which are relatively stable. Thus, this reproducible and simple technique can be used to prepare sterilized, submicron unilamellar liposomes with a relatively high encapsulation efficiency, and excellent stability during long-term storage. |
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Keywords: | Liposome Preparation Freeze-drying Double emulsion Encapsulation efficiency Particle size |
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