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Proceedings Paper

3-dimensional forces and molecular dynamics of live cells
Author(s): Sung Sik Hur; Yi-Shuan Li; Joon Seok Park; Ying-Li Hu; Shu Chien
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Paper Abstract

The forces exerted by an adherent cell on a substrate were studied previously only in the two-dimensions (2D) tangential to the substrate surface. We used a novel technique to measure the three-dimensional (3D) stresses exerted by live bovine aortic endothelial cells (BAECs) on polyacrylamide deformable substrate, with particular emphasis on the 3D forces of focal adhesions. On 3D images acquired by confocal microscopy, displacements were determined with imageprocessing programs, and stresses in tangential (XY) and normal (Z) directions were computed by finite element method (FEM). BAECs generated stress in normal direction (Tz) with an order of magnitude comparable to that in tangential direction (Txy). Tz is upward at the cell edge and downward under the nucleus, changing continuously with a sign reversal between cell edge and nucleus edge. With the use of green fluorescent protein (GFP) labeled paxillin, the dynamics of this intracellular molecule were studied concurrently with the measurement of 3D forces. In the dynamic region, including the new lamellapodium forming region in the front and the retracting region in the rear, the tangential forces (Fxy) are correlated with the size of the focal adhesions (FAs) much more strongly than those in the stable region under the nucleus. In the dynamic region, normal force (Fz) was upward and positively correlated with FA size, while Fz in the stable region was downward and negatively correlated with FA size. These findings show the influence of the size of FAs on the 3D forces they exert on the substrate. This technique can be applied to study any adherent type of live cells to assess their biomechanical dynamics in conjunction with biochemical and functional activities, thus elucidating cellular functions in health and disease.

Paper Details

Date Published: 24 August 2010
PDF: 6 pages
Proc. SPIE 7759, Biosensing III, 77590S (24 August 2010); doi: 10.1117/12.861581
Show Author Affiliations
Sung Sik Hur, Univ. of California, San Diego (United States)
Yi-Shuan Li, Univ. of California, San Diego (United States)
Joon Seok Park, Univ. of California, San Diego (United States)
Ying-Li Hu, Univ. of California, San Diego (United States)
Shu Chien, Univ. of California, San Diego (United States)


Published in SPIE Proceedings Vol. 7759:
Biosensing III
Hooman Mohseni; Manijeh Razeghi, Editor(s)

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