Raman and Infrared Microspectral Imaging of Mitotic Cells

We report the first ever Raman and infrared microspectroscopic images of human cells at different stages of mitosis. These spectroscopic methods monitor the distribution of condensed nuclear chromatin, and other biochemical components, utilizing inherent protein and DNA spectral markers, and, therefore, do not require the use of any stains. In conjunction with previously reported data from the G1, S, and G2 phases of the cell cycle, the complete cell division cycle has now been mapped by spectroscopic methods. Although the results reported here do not offer new insights into the distribution of biochemical components during mitosis, the recognition of cell division without the use of stains, and the possibility of doing so on living cells, may be useful for an automatic, spectroscopic determination of the proliferation rates of cells and tissues. Spectral images were constructed by plotting spectral intensities of DNA or protein versus the coordinates from which spectra were recorded. We found that both Raman and infrared intensities depend on the overall chromatin density variation among the individual subphases of mitosis.