DNA uptake, intracellular trafficking and gene transfection after ultrasound exposure

Ultrasound has been studied as a promising tool for intracellular gene delivery. In this work, we studied gene transfection of a human prostate cancer cell line exposed tomegahertz pulsed ultrasound in the presence of contrast agent and assessed the efficiency of fluorescently labelled DNA delivery into cell nuclei, which is necessary for gene transfection. At the sonication conditions studied, similar to 30% of cells showed DNA uptake 30 min after sonication, but that fraction decreased over time to similar to 10% of cells after 24 h. Most cells containing DNA had DNA in their nuclei, but the amount varied significantly. Transfection efficiency peaked at similar to 10% at 8 h post sonication. Among those cells containing DNA, similar to 30% of DNA was localized in the cell nuclei, similar to 30% was in autophagosomes/autophagolysosomes and the remainder was free in the cytoplasm 30 min after sonication. At later times up to 24 h, similar to 30% of DNA continued to be found in the nuclei and most or all of the rest of the DNA was in autophagosomes/autophagolysosomes. These results demonstrate that ultrasound can deliver DNA into cell nuclei shortly after sonication and that the rest of the DNA can be cleared by autophagosomes/autophagolysosomes. (C) 2016 Elsevier B.V. All rights reserved.