Figure 3.

In vitro and in vivo study of PAI of MNPs. (A) The photoacoustic signal produced by PEG-MNPs at concentrations of 0.625, 1.25, 2.5, 5.0, 10, and 20 μM, and it was observed to be linearly dependent on its concentration (R² = 0.995). (B) Photoacoustic detection of PEG-MNP in living mice. Mice were injected subcutaneously (region enveloped by blue dotted line) with PEG-MNP at concentrations of 0, 5, 10 (from left to right in top row), and 20, 40, 80 (from left to right in bottom row) μM. One vertical slice in the photoacoustic image (red) was overlaid on the corresponding slice in the ultrasound image (gray). (C) The photoacoustic signal from each inclusion was calculated. The background level represents the endogenous signal measured from tissues. The linear regression is calculated on the five most concentrated inclusions (R² = 0.998). (D) The overlaying of ultrasonic (gray) and photoacoustic (red) imagings of U87MG tumor (region enveloped by yellow dotted line) before and after tail-vein injection of 250 μL of 200 μM RGD-PEG-MNP in living mice (n = 3) and their subtraction imagings. (E) Quantitative analysis of enhanced PA signal of U87MG tumor after tail-vein injection with RGD-PEG-MNP at 4 h, compared with at 0 h.