Beckman Institute researcher Gabriel Popescu and his collaborators recently reported on using small changes in the optical properties of living single cells to measure their growth. “Determining the growth patterns of single cells,” they wrote, “offers answers to some of the most elusive questions in contemporary cell biology: how cell growth is regulated and how cell size distributions are maintained.” Mustafa Mir and Zhuo Wang of Popescu’s research group are first and second authors of the paper, Optical measurement of cycle-dependent cell growth, which appeared in the Proceedings of the National Academy of Sciences.

Popescu, a faculty member in the Department of Electrical and Computer Engineering, directs the Quantitative Light Imaging Laboratory which has a focus on developing novel optical methods to quantify both the structure and the dynamics of cells and tissues. This most recent paper described a method that was able to measure something that has previously been elusive: the growth rate of individual adherent cells of different sizes. They were able to demonstrate a newly-developed optical interferometric technique, known as spatial light interference microscopy (SLIM) that can, the researchers wrote, “measure the cell dry mass of many individual adherent cells in various conditions, over spatial scales from micrometers to millimeters, temporal scales ranging from seconds to days, and cell types ranging from bacteria to mammalian cells.”

Mir said that SLIM is capable of measuring mass with a sensitivity of one femtogram, or one thousandth of the mass of a cubic micron of water.

“By using a fluorescence reporter in conjunction with this novel optical technique, (we) were also able to differentiate how the cells regulate their growth in different stages of their lifecycle,” he said. “Aside from the basic science interest, this technology could have broader implications in understanding the effects of cancer treatments and other forms of therapy on the fundamental process of cell growth.”