Lyophilization of cationic lipid-protamine-DNA (LPD) complexes

Cationic lipid-based gene delivery systems have shown promise in transfecti ng cells both in vitro and in vivo. However, these systems tend to form agg regates in liquid formulation during storage, which has limited their clini cal applications. As a result, lyophilization of these systems has recently become a subject of increasing interest. In this paper, lyophilization of LPD, a novel cationic lipid-based gene delivery system, was studied. Both p article size and transfection efficiency could be preserved in the presence of sufficient amount of appropriate lyoprotectant. A series of monosacchar ides and disaccharides, including dextrose, galactose, mannose, lactose, ma ltose, sucrose and trehalose, were evaluated for their lyoprotective effect and disaccharides showed more superior protection to monosaccharides. The effect of different freezing protocols for lyophilization was also evaluate d and no significant difference was found. However, for freeze-thawing, fas t freezing caused less aggregation. Finally, nonlyophilized LPD and LPD lyo philized with 10% sucrose were stored at different temperatures and their s tability was followed for eight weeks. Lyophilized LPD could be stored at r oom temperature without significant change in particle size or loss of tran sfection efficiency. (C) 2000 Wiley-Liss, Inc. and the American Pharmaceuti cal Association J Pharm Sci 89: 355-364, 2000.