Plasmid DNA introduced into cultured cells with diagnostic ultrasound

The usefulness of diagnostic ultrasound in gene transfer was investigated. The hepatocellular carcinoma cell lines PRL/PRF/5 and Hep3B, and the pancreatic carcinoma Panc-1 cells were transfected with lipofectin or irradiated with a linear probe with a frequency of 8 MHz at a mechanical index of 0.4 through the bottom of the plates for 5 min using diagnostic ultrasound (US) with pEGFP-N1 [green fluorescent protein (GFP) expression plasmid], and observed under fluorescence microscopy 48 h later. The cell lines were transfected or irradiated with US with pGL3 control (luciferase reporter plasmid), and a luciferase assay (48 h later) or an MTS assay (72 h later) were performed. Although signals of GFP were observed in cells with US, the transfection efficiencies of US were lower than those of transfection. Luciferase activities of cells with US were higher than those of non-irradiated or transfected cells, but lower than those of transfection. Cell viability with US did not change.