Picosecond opto-acoustics for the remote ultrasonography of single cells

Abstract

Picosecond ultrasonics (PU) is a technique that offers the possibility to generate and detect acoustic waves remotely with an unequalled frequency bandwidth. After decades of developments and applications for researches in solid-state physics, a vast application field was recently demonstrated for PU in biology and medicine. The technique allows imaging single cells with a lateral resolution limited by optics and with the mechanical properties as the contrast mechanism. The opto-acoustic images can reveal the structure of the cell nucleus, the fine details of the actin network and of the adhesion pattern. In addition to imaging capabilities, quantitative analysis of the interaction of the GHz acoustic waves with the complex cell medium provides information on the cell nanostructure. For instances, the standard deviation of impedance data we measured for single nuclei revealed differences between different cell types arising from the multiplicity of local chromatin conformations within the nucleus. Moreover, the distribution of the cell-substrate interface stiffness we identified allowed us to separate the contribution of passive and active adhesion processes. The technique allows thus gaining new insights into cell mechano transduction.