Abstract
Previous studies have shown that some series of liposomes, usually containing cationic lipids, are useful tools for gene introduction into cells. To investigate the effect of ultrasound (US) on liposome-mediated transfection, three types of liposomes (designated L1, L2 and L3, in the order of increasing transfection effciency) containing O,O'-ditetradecanoy1-N-(α-trimethylammonioacety1)diethanolamine chloride, dioleoylphosphatidylethanolamine, and/or cholesterol at varying ratios, were used in this study. HeLa cells were treated with liposome-DNA complexes containing luciferase genes for 2 h before sonication. Optimal US condition for the enhancement was determined to be 0.5 W/cm^2, 1 MHz continuous wave for 1 min. Luciferase expressions 24 h after the treatments were significantly increased by sonication to 2.4 fold with L1, and 1.7 fold with L2. However, with L3, which showed the highest level of expr7ession among the liposomes, luciferase expression was decreased under the same condition. Although the enhancement was not enough to directly apply the combination for the clinic, it might be possible to extend the improvement of the efficiency through elucidating the mechanism for the enhancement.
