Cell volume regulation monitored with combined epifluorescence and digital holographic microscopy

Quantitative phase imaging emerged recently as a valuable tool for cell observation, by enabling label-free imaging through the intrinsic phase-contrast provided by transparent living cells, thus greatly simplifying observation protocols. The quantitative phase signal, unlike the one provided by the widely used phase-contrast microscope, can be related to relevant biological indicators including dry mass, cell volume regulation or transmembrane water movements. Here, we present quantitative phase imaging coupled with live fluorescence, making it possible to follow the phase signal in time to monitor the cell volume regulation, an early indicator of cell viability, along with specific information such as intracellular Ca2+ imaging with Fura-2 ratiometric fluorescence.