Figure 2.

LCI enables high-throughput and longitudinal measurements of cell mass: Four sample images of H929 multiple myeloma cells (a) from the LCI show optical thickness profiles of cells over 6 h of monitoring. Color indicates the phase shift in nm, with dark blue indicating low thickness and white/red indicating high thickness. These sample images are composites of 25 successive charge-coupled device captures taken every 7 min. The inset shows a measurement of the phase shift across a single cell. Integrated phase shift across a cell is directly proportional to cell dry mass. (b) Hundreds of individual cells (outlined in red) are identified at unique positions in each frame and (c) the mass of each individual cell is determined, enabling high-throughput, population-level mass profiling over time. (d) The mass of individual cells is tracked longitudinally over time to examine single-cell growth dynamics. Measurements are shown as open symbols with a linear least squares best fit line. The measured growth rate in this case is 6.5 (se ± 0.72) pg/h. The variation about the linear trend, taken as the standard deviation of the residual error, is 5.0 pg or 1.17% of the median cell mass. The maximum peak-to-peak residual error is 11 pg at 102 min, or 2.61% of the median mass at that time point.