Acoustic Velocity Determination in Cytoplasm by V(Z) Shift

Abstract

The scanning acoustic microscope (SAM) working in the reflection mode allows to determine mechanical properties of biological samples^1,2. At GHz frequencies the resolving power of the microscope is sufficient to investigate cells on glass or plastic in culture^3,4. Previous studies revealed the possibility to measure the distribution of specific impedance and attenuation coefficients of living or fixed cells from the acoustic microscope image ⁵. Assuming a constant density of the cytoplasm we have obtained velocity distributions and the surface profile (thickness) of the cell. We have also observed that an increase of acoustic velocity in the cytoplasm depends on the amount of polymerized actin. Thus, the velocity is directly connected with the mechanical state of the cell ^S. The method presented here is also assigned for velocity determination. Comparing to the previous method another physical effect is used - the shift of V(z) curve. No preliminary assumptions for the cell parameters are required.