Fig. 1. Preparation and exposure principle of AgBr@PLGA nanoparticles. (a) Photosensitive principle of AgBr@PLGA nanoparticles; (b) schematic of photoacoustic imaging technology of AgBr@PLGA nanocrystals; (c) time sequence diagram of photoacoustic intensity amplitude

Fig. 2. Characterization of AgBr@PLGA nanocrystals. (a) Transmission electron microscopy (TEM) image of AgBr; (b) hydrodynamic diameters of AgBr and AgBr@PLGA nanocrystals, where the insets are TEM images of AgBr@PLGA nanocrystals; (c) absorption spectra of AgBr@PLGA nanocrystals without sensitizer before and after exposure; (d) absorption spectra of AgBr@PLGA nanocrystals with sensitizers before and after exposure; (e) scanning electron microscopy (SEM) image of AgBr@PLGA nanocrystals before exposure; (f) SEM image of AgBr@PLGA nanocrystals after exposure

Fig. 3. Optical writing and photoacoustic readout physics technology of AgBr@PLGA nanocrystal

Fig. 4. In vivo photoacoustic (PA) imaging of mice. (a) Photograph of mice injected with nanoparticles; (b) photoacoustic signal of subcutaneous tissue of mice injected with AgBr@PLGA＋GSH nanocrystals; (c) two-dimensional photoacoustic images of subcutaneous tissue of mice injected with AgBr@PLGA＋GSH nanocrystals; (d) three-dimensional in vivo photoacoustic images of mice

Fig. 5. In vivo photoacoustic imaging of tumor-bearing mice. (a) Overlay of tumor photoacoustic and ultrasound imaging at different exposure time; (b) statistics of photoacoustic signal amplitude at different exposure time