Low-Frequency Ultrasound in vitro: Changes of Cell Morphology

For decades, ultrasound technology has been widely used for diagnostic imaging in various clinical fields as well as in therapeutic applications. In recent years there has been considerable research devoted to sonoporation, a phenomenon where ultrasound increases cell membrane permeability. To study the biological effects of ultrasound in an in vitro setting, we have built a custom low-frequency ultrasound experimental system based on an ultrasound transducer submerged in a waterbath. In this study we follow ultrasound-induced changes of cell morphology. B16F1 cells in suspension were exposed for 300 seconds to the continuous-wave low-frequency ultrasound (29.6 kHz; 21.1 W/cm2). Phase contrast and fluorescence microscopy showed various effects of ultrasound within a single cell sample. In the cell population, cells with no visible morphological changes were present, cells that exhibited smaller or larger blebs on the cell membrane as well as cell debris.