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. 2023 Sep 13;17(18):17931–17945. doi: 10.1021/acsnano.3c04161

Figure 5.

Figure 5

Characterization of the in vivo activity of the AuPD nanosensor. (a) Representative laser Doppler perfusion images (LDPI) from the hindlimb ischemia mouse model and control animals (scale bar = 5 mm). The color map shows blood flow (laser Doppler perfusion index, arbitrary units, with warm colors indicating greater perfusion). The yellow arrow indicates the site of ligation of the femoral artery and vein. The red arrows indicate the site of stem cell injections. The nonischemic mouse clearly shows blood flow in the intact femoral artery in the hindlimb region, whereas minimal blood flow is visible in the surgical ischemia model. (b) The orientation of the mouse during US/PA imaging. Yellow box: imaging window where the transducer was placed. (c) Representative US/PA images (single slices) of control (Matrigel injection only; left column), nonischemic (middle column), and surgical ischemia (right column) limbs at days 0 to 7 imaged at 800 nm. No PA signal is visible in the Matrigel-only control, where the yellow dashed lines indicate the Matrigel injection location. PA signal is evident in the no ischemia and surgical ischemia models, both of which were injected with AuPD-labeled hADMSCs. We observe gradual PA signal increase in the no ischemia model due to mild apoptosis vs significant PA signal increase in the surgical ischemia model, consistent with severe apoptosis. The US images are shown in a grayscale map (a.u.), and the PA images are shown in a color map (a.u.). Scale bar is 5 mm. (d, e) PA amplitude spectrograms from AuPD-labeled hADMSCs injected intramuscularly, measured at 700–900 nm longitudinally (days: D0, D3, D5, and D7) for the (d) nonischemic model and (e) surgical ischemia model (n = 6 animals/group). (f) Quantitative PA amplitude from Matrigel-only (control) and AuPD-labeled hADMSCs injected intramuscularly, measured at 800 nm longitudinally (days: D0, D3, D5, and D7) for the nonischemic and the surgical ischemia models (n = 3 animals/control group and n = 6 animals/experimental group). (g) Spectroscopic PA amplitude measured in animals injected with Matrigel only (control) and AuPD-labeled hADMSCs, measured at 700–950 nm longitudinally (days: D0, D7, and D14) for the nonischemic and the surgical ischemia models (n = 3 animals/control and n = 6 animals/experimental group). Panels (f) and (g) show the ability to detect different rates of stem cell apoptosis in ischemic vs nonischemic models by using US/PA imaging of AuPD-labeled stem cells. In panels (d), (e), and (g), solid lines are means and shaded regions show standard deviations.