Dynamic response of cells to ultrasound under the variable heights of culture medium in the well

Abstract

In vitro experiments on the ultrasonic effect of cells in culture wells often lack reproducibility and fail successful transfer to other experimental conditions for the similar ultrasonic device settings. It is suspected that the problem is caused by the standing waves formed in the well, although it is not clarified yet. A one dimensional acoustic theory states that the pressure at the bottom of the culture well where cells are attached varies from 0 to twice of the incident wave while the culture medium height varies a half wave length of the incident ultrasound. The present study looked into the dynamic response of the cells in a culture well exposed to ultrasound under the different standing wave conditions controlled by the height of the culture medium. It was observed that the extent of the morphological changes of the cells exposed to ultrasound were significantly different for the different heights of culture medium even if the ultrasonic device output setting remains unchanged. This founding suggests that the standing waves greatly modify the ultrasonic irradiation condition to the cells. The study claims that the parameter such as the culture medium height associated with standing wave effects must be monitored when in vitro ultrasonic cell experiments are performed. Further investigation including the physiological responses of cells is suggested to underpin the present observations.