Acoustic microscope lens modeling and its application in determining biological cell properties from single- and multi-layered cell models

The acoustic microscopy technique provides some extraordinary advantages for determining mechanical properties of living cells. It is relatively fast, of excellent spatial resolution, and of minimal invasiveness. Sound velocity is a measure of the cell stiffness. Attenuation of cytoplasm is a measure of supramolecular interactions. These parameters are of crucial interest for studying cell motility and volume regulations and to establish the functional role of the various elements of the cytoskeleton. Using a scanning acoustic microscope, longitudinal wave speed, attenuation and thickness profile of a biological cell were measured earlier by Kundu et al. [Biophys. J. 78, 2270-2279 (2000)]. In that study it was assumed that the cell properties did not change through the cell thickness but could vary in the lateral direction. In that effort the acoustic-microscope-generated signal was modeled as a plane wave striking the cell at normal incidence. Such assumptions ignored the effect of cell inhomogenity and the surface skimming Rayleigh waves. In this paper a rigorous lens model, based on the DPSM (distributed point source method), is adopted. For the first time in the literature the cell is modeled here as a multi-layered material and the effect of some external drug stimuli on a living cell is studied.