Label-free Raman spectroscopy monitoring of cytotoxic response induced by a telomerase inhibitor

We proposed a new approach to directly and quantitatively inspect cytotoxicity response at the unicellular scale based on Raman micro-spectroscopy. Variations of intracellular multicomponent caused by the telomerase inhibitor could be revealed by high-throughput Raman spectral screening simultaneously. The changes and modifications of the biochemical compositions including proteins and nucleic acids responded to the telomerase inhibitor were observed through Raman fingerprint assignment analysis of nucleic acids (570, 785, 1093, 1337 and 1484 cm−1) and proteins (570, 1001, 1231, 1337, 1484, 1662 and 2873 cm−1). HeLa cells stressed by different doses of telomerase inhibitor could be distinguished by unsupervised clustering analysis based on their Raman spectroscopy. Four Raman band ratios—I1093/1001, I1093/1032, I1093/1055, and I1093/1066—which were significantly correlated with the inhibitory rate of HeLa cells were identified, and nonlinear quantitative model for cell cytotoxicity was then established based on these Raman ratios. Furthermore, spatial distribution of intracellular important bio-chemical components was showed by Raman chemical imaging with these characteristics Raman ratios, indicating that the granules representing the corresponding substances first exhibited a significant degree of agglomeration (0.4 and 0.8 μM groups), which subsequently declined, becoming smaller and more divergent (1.6 and 4 μM groups) as cytotoxicity increased. This study provides a rapid and quantitative assessment for cytotoxicity induced by chemicals at the single-cell level. The ability to directly monitor chemically-induced cell cytotoxicity in situ promotes understanding of molecular level changes and improves knowledge of the molecular mechanisms involved, which has great application potential in pharmacological mechanism exploration and drug development.