Use of a piezoelectric actuator to study the mechanical oscillatory behavior of living cells

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (leaves 33-34).Mechanical forces are known to directly influence the structure and function of living cells in a frequency-specific manner, however, the mechanism behind this frequency sensitivity remains unknown. The effects of high frequency mechanical perturbations were investigated in cultured capillary endothelial cells using a piezoelectric actuator. The actuator was used to displace fibronectin-coated coverslip on which the cells were cultured the associated displacement of sub-cellular regions was examined using surface-bound microbeads in conjunction with real-time light microscopy and image analysis. The role of different cytoskeletal microtubules and microfilaments in the cellular response to stress was examined using specific chemical disruptors (nocodazole and cytochalasin D, respectively); the level of prestress (preexisting tension) in the cell was altered by addition of the constrictor agent, thrombin. The results showed that the experimental method is effeqtive for determining the effects of chemical disruptors on the mechanical oscillatory behavior of cells. Specifically, in the presence of nocodazole, absolute displacement of beads on cells peaked at 1100 Hz whereas it peaked at approximately 200 Hz in the presence of cytochalasin-D. Finally, error inherent in the original system was reduced by refocusing the cells and beads on the microscope and optimizing image exposure time, which both yielded more definitive results. This optimized technique may be useful for future studies analyzing changes in cell structure and cellular biochemistry in response to different frequencies of mechanical stimulation.by Jack Yu.S.B