Ultrasound-mediated gene delivery: kinetics of plasmid internalization and gene expression

Sonoporation is an approach that can be used to transfer DNA or drugs into cells. However, very little is known about the mechanism of ultrasound-mediated membrane permeabilization. In this investigation, DNA transport post-sonoporation and the subsequent plasmid internalization and protein expression kinetics have been studied. Using a plasmid encoding for the green fluorescent protein (GFP), labelled or not with an intercalating agent (YOYO-1), it was found that, as compared to lipofection that requires endocytosis, sonoporation allowed a rapid and direct transfer of naked DNA into the cell cytoplasm probably via ultrasound-induced pores in the membrane. The kinetics of protein expression were significantly faster for sonoporation than for lipofection, the mechanism of which requires endocytosis. However, unprotected DNA in the cytoplasm could be degraded by resident cytosolic DNases, thereby decreasing ultrasound-mediated gene delivery efficiency.