Fig. 2

Fig. 2 Pulsed-SBS imaging of cultured cells.

a, Three-dimensional sections of Brillouin shift images of a NIH/3T3 fibroblast cell under 20 mW pump and 7 mW probe with a z-step of 1 µm. The coregistered brightfield image and fluorescence image (15 h after Brillouin imaging) of the cell stained with PI dye are shown below. b, Three-dimensional Brillouin shift images of two fibroblast cells under 20 mW pump power and 7 mW probe power with a z-step of 1 µm. The brightfield and fluorescence images (42 min after Brillouin imaging) are shown below the Brillouin images. c, Three-dimensional Brillouin shift images of the same two cells under 240 mW pump power and 7 mW probe power after b with a z-step of 1 µm. Scale bars in a–c are 10 µm. Note that the PI dye, a viability marker that indicates damaged membranes, is staining the nucleus. d, Brightfield image of a NIH/3T3 fibroblast cell. e,g,h, The Brillouin shift (Ω_B) (e), Brillouin gain (G_B) (g) and Brillouin linewidth (Γ_B) (h) images of the x–y plane. f,i, The Brillouin shift (f) and Brillouin linewidth (i) images of the x–z plane along the dashed yellow line in d. The dashed green line in f marks the substrate (that is, PAA-based gel) boundary. Scale bars in d–i are 5 µm. j, Relative frequency up-shift of CW SBS with respect to pulsed SBS of three regions (nucleolus, nucleoplasm and cytoplasm) for (n = 4) cells between 27 mW power and 250 mW power. The average up-shifts in the nucleolus, nucleoplasm and cytoplasm regions are 47.5 MHz, 35.5 MHz and 44.0 MHz, respectively. All image pixel steps and pixel time are 0.25 µm × 0.25 µm and 20 ms, respectively.

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