Submitted on February 25, 2008
Revised on May 21, 2008
Accepted on June 10, 2008
Optical Imaging of Cell Mass and Growth Dynamics
Gabriel Popescu, YoungKeun Park, Niyom Lue, Catherine Best-Popescu, Lauren Deflores, Ramachandra R. Dasari, Michael S. Feld1, and Kamran Badizadegan1*
1 Massachusetts Institute of Technology
* To whom correspondence should be addressed. E-mail: kamran{at}mit.edu.
Using novel interferometric quantitative phase microscopy methods, we demonstrate that the surface integral of the optical phase associated with live cells is invariant to cell water content. Thus, we provide an entirely non-invasive method to measure the non-aqueous content or "dry mass" of living cells. Given the extremely high stability of the interferometric microscope and the femtogram sensitivity of the method to changes in cellular dry mass, this new technique is not only ideal for quantifying cell growth, but also reveals spatially-resolved cellular and subcellular dynamics of living cells over many decades in temporal scale. Specifically, we present quantitative histograms of individual cell mass characterizing the hypertrophic effect of high-glucose in a mesangial cell model. In addition, we show that in an epithelial cell model observed for long periods of time, the mean squared displacements (MSD) data reveal specific information about cellular and subcellular dynamics at various characteristic length and time scales. Overall, these studies show that interferometeric quantitative phase microscopy represents a non-invasive optical assay for monitoring cell growth, characterizing cellular motility, and investigating the subcellular motions of living cells.
