RATIONALE AND OBJECTIVESCationic liposomes are under development as delivery agents for gene therapy. The authors studied the effect of ultrasound on gene expression in cell cultures during liposomal transfection experiments.METHODSCationic liposomes of dipalmitoylethylphosphocholine and dioleoylphosphatidylethanolamine were used to transfect cultured HeLa, NIH/3T3, and C127I cells with the chloramphenicol acetyl transferase (CAT) gene. A cell viability assay was performed on cultured HeLa cells that were exposed to varying durations (5 seconds or 30 seconds) and intensities of 1 MHz continuous-wave therapeutic ultrasound after transfection, and gene expression was measured 48 hours later.RESULTSCells survived 30 seconds or less at a power level of 0.5 watts/cm2but died when exposed for 60 seconds or longer. Exposures of 5 seconds and 30 seconds of ultrasound resulted in significant increases in gene expression in all three cell types tested in this experiment.CONCLUSIONSRelatively low levels of ultrasound energy can be used to enhance gene expression from liposomal transfection. Additional experiments are needed to optimize this process and clarify the mechanisms involved.
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