Vevo 2100 lazr system

To examine the accumulation efficiency of melanin in the tumor regions, photoacoustic imaging and ultrasound imaging were performed at designated time points (6, 12, 24, 36 hours) after OASI treatment using a Vevo 2100 LAZR system (VisualSonics, Inc., New York, NY, USA). The center frequency of the ultrasound imaging transducer was 40 MHz and the wavelength of the excitation laser was 685 nm. 3D scanning of the whole tumor region was carried out at a scan distance of 10 mm and a step size of 0.2 mm. The tumor regions in both intravenous and intratumoral injection groups were monitored during laser irradiation (1 W/cm²) using a Fluke-Ti25 infrared thermal camera.

Comparative PA studies of the different SiNC(1–4) dyes, IRDye800, and ICG were performed using a Vevo 2100 LAZR system (Visualsonics, FujiFilm, ON, Canada) equipped with a 21 MHz transducer (LZ250) and an Nd:YAG laser. Stock solutions (prepared in DMSO) of the different dyes were diluted in PBS at a concentration of 5 µM and loaded in polyethylene tubes (BTPE-50; Instech Laboratories Inc., Plymouth Meeting, PA, USA). Spectral PA measurements were performed in the wavelength range of 680 to 950 nm. PA signal intensity at the absorption maxima of the different dyes (mentioned elsewhere in the manuscript) was used to plot the PA signal intensity versus concentration graph post-adjustment of wavelength-dependent laser output energy. PA imaging parameters—PA gain, laser power, signal intensity, and persistence were kept constant across different measurements. The dye solutions placed inside a tube were also located at the same distance from the transducer to avoid variation in PA signal due to difference in fluence. Image analysis was performed using the built-in VevoLab 5.5.1 software.

Photoacoustic (PA) imaging and in vivo fluorescence imaging were used to observe the enrichment of nanoparticles in the tumor site after intravenous injection. For PA imaging, after being i.v. injected with Fe–GA/CaO₂@PCM NPs, the tumor regions of mice were imaged with a Visual sonics Vevo 2100 LAZR system at different time points (0, 2, 4, 8 and 24 h) with 808 nm laser excitation.

To monitor the NIR FL and PA imaging signals of P-CyPt in response to ALP, P-CyPt (10 μM) in Tris buffer (1 mL) was incubated with ALP (100 U/L) at 37 °C for 0, 5, 10, 15, 20, and 30 min. To monitor the NIR FL and PA imaging signals of Pt^IVNPs in response to GSH, P-CyPt (10 μM) in Tris buffer (1 mL) was first incubated with ALP (100 U/L) at 37 °C for 30 min and then incubated with 10 mM GSH at 37 °C for another 10, 20, 30, 40, 50, and 60 min. The NIR FL spectra of these solutions at each time point were acquired on a HORIBA Jobin Yvon Fluoromax-4 fluorescence spectrometer, with excitation at 680 nm. For PA imaging, the incubation solutions at each time point were loaded into a fine bore polythene tube (0.86 mm OD, 1.27 mm OD). The tubes were then sealed and immersed in water. The PA images at both 700 and 750 nm were acquired on the Vevo 2100 LAZR system (FUJIFILM VisualSonics).