Monitoring correlates of SARS-CoV-2 infection in cell culture using two-photon microscopy and a novel fluorescent calcium-sensitive dye

The organism-wide effects of viral infection SARS-CoV-2 are well studied, but little is known about the dynamics of how the infection spreads in time among or within cells due to the scarcity of suitable high-resolution experimental systems. Two-photon (2P) imaging combined with a proper subcellular staining technique has been an effective tool for studying mechanisms at such resolutions and organelle levels. Herein, we report the development of a novel calcium sensor molecule along with a 2P-technique for identifying imaging patterns associated with cellular correlates of infection damage within the cells. The method works as a cell viability assay and also provides valuable information on how the calcium level and intracellular distribution are perturbed by the virus. Moreover, it allows the quantitative analysis of infection dynamics. This novel approach facilitates the study of the infection progression and the quantification of the effects caused by viral variants and viral load. ### Competing Interest Statement BR and GK are founders of Femtonics and members of its scientific advisory board. GF is now an AstraZeneca employee, but the work was conducted with no connection to AZ. The other authors declare that no conflict of interest exists.