H₂O₂‑Activated NIR-II Fluorescent Probe with a Large Stokes Shift for High-Contrast Imaging in Drug-Induced Liver Injury Mice

Drug-induced liver injury (DILI) is the most common clinical adverse drug reaction, which is closely associated with the oxidative stress caused by overproduced reactive oxygen species. Hepatic H₂O₂, as an important biomarker of DILI, plays a crucial role in the progression of DILI. However, there remains a challenge to develop H₂O₂-activatable second near-infrared (NIR-II, 1000–1700 nm) small molecular probes with both a large Stokes shift and a long emission wavelength beyond 950 nm. Herein, we developed an activatable NIR-II fluorescent probe (<b>IR-990</b>) with an acceptor-π-acceptor (A-π-A) skeleton for real-time detection of H₂O₂ in vivo. In the presence of H₂O₂, nonfluorescent probe <b>IR-990</b> was successfully unlocked by generating a donor-π-acceptor (D-π-A) structure and switched on intense NIR-II fluorescence, exhibiting a peak emission wavelength at 990 nm and a large Stokes shift of 200 nm. Moreover, it was able to detect H₂O₂ with high sensitivity and selectivity in vitro (LOD = 0.59 μM) and monitor the behavior of endogenous H₂O₂ in the HepG2 cell model of DILI for the first time. Notably, probe <b>IR-990</b> was successfully applied in real-time imaging of endogenous H₂O₂ generation in the DILI mouse model, showing a high signal-to-background ratio of 11.3/1. We envision that <b>IR-990</b> holds great potential as a powerful diagnosis tool for real-time visualization of H₂O₂ in vivo and revealing the mechanism of DILI in the future.