Ultrasound-mediated perfluorocarbon microbubbles bursting for gene transfection

Ultrasound contrast agents (microbubbles) have been extensively applied as acoustic cavitation nuclei for drug and gene delivery. During microbubble bursting, several physical impacts such as shock waves can transiently disrupt cell membranes, and thereby facilitating the cellular uptake of genetic materials. Instead of using commercial microbubble (e.g., Optison or Definity), perfluorocarbon microbubbles with phase-shifting capability were harnessed in this study to examine their efficacy for gene delivery. Using ultrasonic homogenization technique, nonechogenic liquid perfluoropentane (C ₅F₁₂) microdroplets were stabilized by human serum albumin in the cell culture medium. Because the boiling point of perfluoropentane is 29°C, the liquid emulsions shifted to echogenic microbubbles at 37°C and served as cavitation nuclei. NIH 3T3 fibroblasts were exposed to ultrasound in the presence of perfluoropentane microbubbles and luciferase-encoded plasmid DNA. Our results showed that under 5-min mega-hertz ultrasonic exposure in the presence of perfluoropentane microbubbles, the level of luciferase gene expression increased up to 2-fold, in comparison with the one without adding microbubbles.