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Ultrasound enhances gene expression of liposomal transfection
E C Unger1, T P McCreery, R H Sweitzer
1ImaRx Pharmaceutical Corporation, Tucson, Arizona 85719, USA.
Rationale And Objectives:
Cationic 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.
Methods:
Cationic 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.
Results:
Cells survived 30 seconds or less at a power level of 0.5 watts/cm2 but 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.
Conclusions:
Relatively 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.