Figure 2.

Raman imaging of single cells. (a-c) Schematics demonstrating the energy level diagrams in Raman imaging. (a) Spontaneous Raman scattering. The straight line (green) indicates the pump beam at ω_P, and the curved line (red) denotes the scattered light at a longer wavelength ω_S. (b) Stimulated Raman scattering (SRS). Two lasers, a pump (ω_P) and a Stokes beam (ω_S) impinge upon a sample with stimulated emission occurring when △ω (Dω = ω_P - ω_S) equals to a molecular vibration frequency. (c) Coherent anti-stokes Raman scattering (CARS). In CARS, a pump (ω_P) and a Stokes beam (ω_S) illuminate the sample and when ω_P - ω_S matches the molecular vibration frequency an anti-Stokes signal at 2ω_P - ω_{S =} ω_aS is generated. (d) Distribution of lipids (1420–1460 cm⁻¹) in a pulmonary cell obtained by spontaneous Raman imaging. (e) An SRS image showing the concentration of cytoplasmic membrane lipids in live melanoma cells. (f) CARS image of a neuronal cell. The purple color shows CH₂ bonds while the green color is the plasma membrane dye, Ap3-SFG. Panel a-c was reprinted with permission from Tipping WJ, Lee M, Serrels A, Brunton VG, Hulme AN. Chem Soc Rev. 2016;45(8):2075–89. Panel d was reprinted with permission from Tott S, Grosicki M, Glowacz J, Mohaissen T, Wojnar-Lason K, Chlopicki S, et al. Biochimica et Biophysica Acta 2021;1867(9):166180. Panel e was reprinted with permission (CC BY-NC-ND) from Oh S, Lee C, Yang W, Li A, Mukherjee A, Basan M, et al. Proc Natl Acad Sci USA. 2022;119(17):e2117938119. Panel f was reprinted with permission from Mizuguchi T, Momotake A, Hishida M, Yasui M, Yamamoto Y, Saiki T, et al. Anal Chem. 2020;92(8):5656–60. Copyright 2020 American Chemical Society.