Analysis of intracellular transport dynamics using quantitative phase imaging and FRET-based calcium sensors

Understanding cellular responses to mechanical environmental stimuli is an essential goal of cellular mechanotransduction studies and remains a target for microscopy technique development. While fluorescence microscopy has been advanced for this purpose - its molecular sensitivity, the ability of quantitative phase imaging to visualize subcellular structure has yet to be widely applied, perhaps due to its limited specificity. Here we seek to combine Quantitative Phase Imaging (QPI) with a molecularly sensitive Förster resonance energy transfer (FRET) construct for cell mechanotransduction studies. The multimodal imaging instrument is applied to examine cellular response to hypo-osmotic stimulus by observing the influx of calcium ions using a FRET based sensor coupled with mapping of the redistribution of intracellular mass using QPI. The combined imaging modality enables discrimination of cell response by localized region and reveals distinct behavior for each. The analysis shows cell flattening and oscillatory mass transport in response to the stimulus. With the broad array of FRET sensors under development, the combination with QPI offers new avenues for studying cell response to environmental stimuli.