Atomic force microscopy can be used to mechanically stimulate osteoblasts and evaluate cellular strain distributions

In this study, atomic force microscopy (AFM) was used to mechanically stimu late primary osteoblasts. In response to mechanical force applied by the AF M, the indented cell increased its intracellular calcium concentration. The material properties of the cell could be estimated and the membrane strain s calculated. We proceeded to validate this technique experimentally and a 20% error was found between the predicted and the measured diameter of inde ntation. We also determined the strain distributions within the cell that r esult from AFM indentation using a simple finite element model. This enable d us to formulate hypotheses as to the mechanism through which cells may se nse the applied mechanical strains. Finally, we report the effect of the Po isson ratio and the cell thickness on the strain distributions. Varying the Poisson ratio did not change the order of magnitude of the strains; wherea s the cellular thickness dramatically changed the order of magnitude of the cellular strains. We conclude that AFM can be used for controlled mechanic al stimulation of osteoblasts and that cellular strain distributions can be computed with a good accuracy when the cell is indented in its highest par t. (C) 2001 Elsevier Science B.V. All rights reserved.