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@Cu2O) nanoprobe for colorectal cancer PA imaging within NIR-II window. Under the existence of HS-, the SnS@Cu2O 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 H2S. The in vitro PA intensity was linearly correlated to HS- concentration in the range of 0-1.2 mM. Intratumoral injection of SnS@Cu2O 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@Cu2O can catalyze the Cu+ with H2O2 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@Cu2O nanoprobe that was activated by colorectal tumor microenvironment.