This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.107.111641v1 93/10/3703    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Massiera, G. Articles by Crocker, J. C. Search for Related Content PubMed PubMed Citation Articles by Massiera, G. Articles by Crocker, J. C.

Mechanics of Single Cells: Rheology, Time Dependence, and Fluctuations

Gladys Massiera ^*, Kathleen M. Van Citters ^*, Paul L. Biancaniello  and John C. Crocker ^* 

^* Department of Chemical and Biomolecular Engineering, Department of Physics and Astronomy, and Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104

Correspondence: Address reprint requests to John C. Crocker, Dept. of Chemical and Biomolecular Engineering, University of Pennsylvania, 220 S. 33rd St., Philadelphia, PA 19104. Tel.: 215-898-9188; Fax: 215-573-2093; E-mail: jcrocker{at}seas.upenn.edu.

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 either in response to an oscillatory magnetic torque (MTC) or due to random Brownian or ATP-dependent forces (LTM). This approach is well suited for 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.