Deformation of nucleated cells driven by ultrasonic standing waves

The deformation of nucleated cells driven by ultrasonic standing waves in fluid environment is investigated by theoretical analysis and numerical simulation. The nucleated cells are considered to consist of cell membrane, cytoplasm and nucleus The cell membrane is assumed to have in-plane deformation and bending resistances, in which the in-plane deformation is modeled by the generalized Hooke's law, and the bending resistance is modeled by the Helfrich bending energy formula. Due to the acoustic mismatch between the media inside and outside the cell, the generated acoustic radiation stress on the cell membrane causes the nucleated cell to deform. Considering the acoustic scattering of the nucleus, the acoustic radiation stress is formulated by applying the acoustic radiation stress tensor theory. Based on the proposed theoretical model, a finite element model is established to solve the coupling problem of ultrasonic propagation and cell deformation. The analytical solution for the acoustic induced deformation of nucleated cells in the limits of long wavelength and small deformation is given and successfully verifies the finite element model. The results show that the deformation of nucleated cells is much larger than that of enucleated cells due to the effect of the nucleus on wave propagation. The deformation of nucleated cells is significantly affected by nuclear size and nuclear density. This study is helpful to accurately extract the mechanical properties of nucleated cells and further promote the detection of cell-related diseases by acoustic deformation technology.