Development of a focused-ultrasound spectroscopic-imaging system combined with optical imaging for applying mechanical stimulation on living cells and the possibility of selective stimulation for the nucleus

Abstract

Various techniques have been used for the mechanical stimulation of cells, but most of them require direct contact with cells and can damage them. Here, we propose a focused ultrasound technique for non-invasive localized mechanical stimulation in a culture environment. First, we develop the focused ultrasound system for establishing the spectroscopic images and for applying mechanical stimulation combined with optical observation. Second, we construct the acoustic-absorption spectroscopic images of human mesenchymal stem cells, leading to the finding of the ultrasound absorption band of the nucleus around 130 MHz caused by its resonance. Finally, we find that the nucleus less absorbs ultrasound before the cell division, supporting our view that the acoustic absorption band is related to the resonance of the nucleus. Our results show the potential for realizing selective and effective mechanical stimulation for nuclei non-invasively, which is critically important for a deeper understanding of mechanobiology.