Label-free tracking of intracellular molecular crowding with cell-cycle progression using Raman microscopy

[Display omitted] •Raman imaging allows quantitative evaluation of intracellular molecular crowding.•In the nucleus, the crowding environment changes with the cell cycle progression.•The environment in the cytoplasm was robust and maintained.•Change in the environment in the nucleus alters the stability and regulation of biomolecules. Intracellular environments are highly crowded with biomolecules, called molecular crowding, and the structures and functions of biomolecules in cells are influenced by molecular crowding. In this study, we tracked the changes in intracellular crowding environments during cell cycle progression using Raman imaging. The intensity ratio between the C–H and O–H stretching bands allows us to quantitatively monitor the crowding environments. The results show that the nucleus is more crowded in the M phase than in other phases; however, the cytoplasm is maintained. The changes in molecular crowding in the nucleus can affect the stability and regulation of biomolecules.