Continuous morphology and growth monitoring of different cell types in a single culture using quantitative phase microscopy

The minimally-invasive quantitative observation of different cell types in a single culture is of particular interest for the analysis of the impact of pharmaceuticals, pathogens or toxins on different cellular phenotypes under identical measurement conditions and to analyze interactions between different cellular specimens. Quantitative phase microscopy (QPM), provides high resolution detection of optical path length changes that is suitable for quantitative tomographic imaging and stain-free minimally-invasive live cell analysis. Due to low light intensities for object illumination, QPM minimizes the interaction with the sample and thus is in particular suitable for long term time-lapse investigations on cells in which for example morphology alterations due to toxins, drugs or genetic modifications are studied. We analyzed the feasibility of QPM, for the analysis of mixed cell cultures and explored if quantitative phase images provide sufficient information to distinguish between different cell types and to extract cell specific parameters. For the experiments quantitative phase imaging with digital holographic microscopy (DHM) was utilized. Mixed cell cultures with different cell types were continuously observed with quantitative DHM phase contrast up to 35 h. The obtained series of quantitative phase images were evaluated by adapted image segmentation algorithms. From the segmented quantitative phase images the area covered by the cells, the cellular dry mass as well as the mean cell thickness and volume were determined and used as parameters to quantify the reliability of data acquisition. The obtained results demonstrate that it is possible to characterize the growth of cell types with different morphology features separately in a single cell culture. This prospects new application fields of quantitative phase imaging in drug and toxicity testing in vitro.