  In situ measurement of cellular metabolites is still a challenge in biology.
Conventional methods, such as mass spectrometry or fluorescence microscopy,
would either destruct the sample or introduce strong perturbations to the
functions of target molecules. Here, we present multiplex stimulated Raman
scattering (SRS) imaging cytometry as a label-free single-cell analysis
platform with chemical specifity, and high-throughput capabilities. Cellular
compartments such as lipid droplets, endoplasmic reticulum, and nuclei are
seperated from the cytoplasm. Based on these chemical segmentations, 260
features from both morphology and molecular composition were generated and
analyzed for each cell. Using SRS imaging cytometry, we studied the metabolic
responses of human pancreatic cancer cells under stress by starvation and
chemotherapy drug treatments. We unveiled lipid-facilitated protrusion as a
metabolic marker for stress-resistant cancer cells through statistical analysis
of thousands of cells. Our findings also demonstrate the potential of targeting
lipid metabolism for selective treatment of starvation-resistant and
chemotherapy-resistant cancers. These results highlight our SRS imaging
cytometry as a powerful label-free tool for biological discoveries with a
high-throughput, high-content capacity.
