Measurement and correlation of acoustic cavitation with cellular bioeffects.

Using broadband noise as a measure of cavitation activity, this study determined the kinetics of cavitation during sonication of Optison contrast agent and tested whether cellular bioeffects can be predicted by cavitation dose. Cell suspensions were exposed to ultrasound at varying acoustic frequency, pressure, exposure time, Optison concentration and cell type to obtain a broad range of bioeffects, i.e., intracellular uptake and loss of viability, as quantified by flow cytometry. We found that cavitation activity measured by broadband noise increased and peaked within 20 ms and then decayed with a half-life of tens to hundreds of milliseconds. Intracellular uptake and loss of viability correlated well with the cavitation dose determined by the time integral of broadband noise magnitude. These results demonstrate that broadband noise correlates with bioeffects over a broad range of experimental conditions, which suggests a noninvasive feedback method to control ultrasound's bioeffects in real time.

Ultrasonically targeted delivery into endothelial and smooth muscle cells in ex vivo arteries.

This study tested the hypothesis that ultrasound can target intracellular uptake of drugs into vascular endothelial cells (ECs) at low to intermediate energy and into smooth muscle cells (SMCs) at high energy. Ultrasound-enhanced delivery has been shown to enhance and target intracellular drug and gene delivery in the vasculature to treat cardiovascular disease, but quantitative studies of the delivery process are lacking. Viable ex vivo porcine carotid arteries were placed in a solution containing a model drug, TO-PRO(R)-1, and Optison microbubbles. Arteries were exposed to ultrasound at 1.1 MHz and acoustic energies of 5.0, 66, or 630 J/cm(2). Using confocal microscopy and fluorescent labeling of cells, the artery endothelium and media were imaged to determine the localization and to quantify intracellular uptake and cell death. At low to intermediate ultrasound energy, ultrasound was shown to target intracellular delivery into viable cells that represented 9-24% of exposed ECs. These conditions also typically caused 7-25% EC death. At high energy, intracellular delivery was targeted to SMCs, which was associated with denuding or death of proximal ECs. This work represents the first known in-depth study to evaluate intracellular uptake into cells in tissue. We conclude that significant intracellular uptake of molecules can be targeted into ECs and SMCs by ultrasound-enhanced delivery suggesting possible applications for treatment of cardiovascular diseases and dysfunctions.