Single Cell Metabolic Profiling Using Coherent Raman Microspectroscopy

Metabolic profiling of cancer cells has elucidated novel mechanisms of chemotherapeutic resistance, dedifferentiation, and metastasis in recent years. Current methods used to characterize metabolites at the single cell level are limited due to their destructive nature. Coherent Raman spectroscopy (CRS) can be applied as a label-free, non-destructive imaging technique. Through probing chemical bond resonances, CRS provides a potential live-cell quantification of a vast array of macromolecules at diffraction-limited resolution (300nm), allowing the visualization of subcellular structures. This spatial resolution enables the microspectroscopic chemical characterization of lipid droplets (LDs), the primary storage organelle of fatty acids (FAs), which play a key role in cancer metabolism and chemoresistance. Within the C-H region of the Raman spectrum, one can calculate the saturated FA and unsaturated FA changes in response to different perturbations. Additionally, spectral unmixing of the C-H region reveals the average FA chain length. Combining these measurements enable the evaluation of changes in lipid metabolism that occur in cancer cells in response to chemotherapeutic in real time. Using SRS, continuous measurement of lipid content during drug treatment, we characterize the acute survival response to chemotherapies. This method can be further applied to study the metabolic heterogeneity inherent in a clonal population to identify which cells display a more advantageous metabolic phenotype prior to drug treatment. Overall, CRS provides a platform for continuous label-free non-destructive microspectroscopy to study dynamic changes in cancer metabolism to better understand adaptation mechanisms in response to a chemotherapeutic.