Abstract
Understanding the time when molecular delivery occurs during sonoporation is important to improve the efficiency of successful sonoporation and fraction of viable cells. Here, we report how ultrasound conditions affect the time for sonoporation. We employed real-time observations of propidium iodide (PI) delivery to 3T3-Swiss albino cells under 5 seconds 1 MHz continuous ultrasound waves treatment with fluorescence (PI) and microbubbles SONAZOID^[○!R]. Sonoporation timing was evaluated by analyzing the time courses of the altering fluorescence intensity of the cells. Three ultrasound intensity conditions, 0.15, 0.20 and 0.30 W/cm^2, were examined. Fluorescence intensity increased for 0.20 and .30 W/cm^2-sonication, indicating PI delivery into the cells, while no apparent increase was observed for 0.15 W/cm^2-sonication. Fluorescence intensity clearly started to increase earlier for 0.30 W/cm^2 than for 0.20 W/cm^2-sonication. Sonoporation timing ranged from 2 to 6 seconds for 0.30 W/cm^2-sonication. The most delayed timing was obtained for cells that had the largest adhesion area. As a conclusion, different microbubble responses stimulated by various ultrasound conditions may cause different sonoporation timing.
