Mechanics of single cells: rheology, time dependence and fluctuations
Gladys Massiera 1, Kathleen M. Van Citters 2, Paul L. Biancaniello 2 and John C. Crocker 2*
1 Université Montpellier 2
2 University of Pennsylvania
* To whom correspondence should be addressed. E-mail: jcrocker{at}seas.upenn.edu.
Submitted on April 26, 2007
Revised on May 31, 2007
Accepted on 24 July 2007
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Abstract |
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The results of mechanical measurements on single cultured epithelial cells using both Magnetic Twisting Cytometry (MTC) and Laser Tracking Microrheology (LTM) are described. Our unique approach uses laser deflection for high performance tracking of cell-adhered magnetic beads, in response to either an oscillatory magnetic torque (MTC) or due to random Brownian or ATP-dependent forces (LTM). This approach is well suited to accurately determining the rheology of single cells, the study of temporal and cell to cell variations in the MTC signal amplitude, and assessing the statistical character of the tracers' random motion in detail. The temporal variation of the MTC rocking amplitude is surprisingly large, and manifests as a frequency-independent multiplicative factor having a 1/f spectrum in living cells, which disappears upon ATP depletion. In the epithelial cells we study, random bead position fluctuations are Gaussian to the limits of detection both in the Brownian and ATP-dependent cases, unlike earlier studies on other cell types.
Key Words:
cell mechanics, cytoskeleton, laser tracking, magnetic twisting cytometry, microrheology, viscoelastic modulus
