Characterization of human breast epithelial cells by confocal Raman microspectroscopy

Background The past decade has seen an explosion of interest in utilizing Raman spectroscopy in cancer diagnosis, due to its capability to probe changes in the biochemical composition of tissue that accompany disease progression. However, most of the existing methods used multivariate statistical analysis/chemometrics to differentiate normal and diseased tissues, which did not identify the compositional and chemical changes associated with the tumorigenic transition explicitly; also the sub-cellular level spatial resolution achievable through Confocal Raman microscopy was not fully utilized. Methods Confocal Raman microspectroscopy was used to characterize normal and transformed human breast epithelial cell lines. Key molecular components (DNA, RNA, and proteins) were extracted from cell nuclei and their Raman spectra were measured and used as a basis set to fit the spectra of cell nuclei. Contributions of each component and their relative contents were evaluated based on the fitting coefficients. Results Spectrum-fitting revealed that DNA duplication activities in tumorigenic cell nuclei are significantly higher than in normal cells. The fitting coefficients could serve as good spectral markers for disease state identification. Conclusions A spectroscopic approach that yields compositional information of cell nuclei could be a powerful tool for rapid cell characterization and assessment of cellular activities at the sub-cellular level.