A NIR-II absorption nanoprobe enhanced by stannous sulfide for photoacoustic imaging and photothermal-augmented chemodynamic therapy of colorectal cancer

Near-infrared II (NIR-II) photoacoustic (PA) imaging offers enhanced performance through reduced photon scattering, minimized background interference, and improved resolution at greater depths, thereby driving urgent demand for NIR-II PA nanoprobes in translational biomedicine. In this study, we developed a smart stannous sulfide@cuprous oxide (SnS@Cu 2 O) nanoprobe for colorectal cancer PA imaging within NIR-II window. Under the existence of HS − , the SnS@Cu 2 O nanoprobe exhibits a broad absorption peak within the 1000–1300 nm range, enabling concentration-dependent NIR-II PA signal amplification in colorectal cancer tissues with overexpression of endogenous H 2 S. The in vitro PA intensity was linearly correlated to HS − concentration in the range of 0–1.2 mM. Intratumoral injection of SnS@Cu 2 O nanoprobe (10 mg/kg) induced time-dependent PA signal amplification at the tumor site, exhibited rapid intensification, peaking at 4-h post-administration. Additionally, the SnS@Cu 2 O can catalyze the Cu + with H 2 O 2 in the tumor tissue yielding ·OH via Fenton-like reactions for photothermal-enhanced chemodynamic therapy, enabling NIR-II PA imaging-guided therapy against deep-tissue colorectal tumor. This paper reports on the synthesis and application of a smart SnS@Cu 2 O nanoprobe that was activated by colorectal tumor microenvironment.