Biophysical monitoring of cell cultures for quality assessment utilizing digital holographic microscopy

Quality and reproducibility of cell-based assays strongly depend on the quality of the underlying cell culture which is influenced by various parameters like nutrient and growth factor availability, buffer conditions, subculture routines and optimal cell concentrations. Thus, methods for accurate assessment of objective cell parameters that characterize a specific cell line and detect global changes in cell culture are highly desirable. During the past years, quantitative phase imaging has been recognized as a promising tool for quantitative label-free live cell analysis. We demonstrate the utilization of quantitative phase imaging with digital holographic microscopy (DHM) to quantify the impact of cell culture conditions on single cells using a pancreatic tumor cell model. Label-free quantitative phase imaging of detached cells in suspension is performed by Michelson interferometer-based self-interference DHM. The quantitative phase images of the cells are analyzed for refractive index, volume and dry mass. We show that the evaluation of quantitative DHM phase images allows to extract absolute biophysical cellular parameters that are related to cell layer confluence states. In summary, the results of our study demonstrate that DHM is capable for label-free imaging cytometry with novel biophysical data sets that are acquired with minimum sample preparation for sophisticated monitoring of cell morphology alterations that are related to changes of cell culture conditions.