"Dual-Lock-Dual-Key" Controlled Second Near-Infrared Molecular Probe for Specific Discrimination of Orthotopic Colon Cancer and Imaging-Guided Tumor Excision

Fluorescence imaging in the second infrared window (1000-1700 nm) has emerged as a promising approach to tumor diagnosis. However, the currently available second near-infrared (NIR-II) imaging agents are based on the "always on" modality or single biomarker activation, which are subject to limited imaging contrast, nonspecific response, and even false-positive diagnosis. Here, we developed a H2S/H+ dual-stimuli responsive NIR-II fluorescent probe, WH-N-3, for precise tumor delimitation and intraoperative fluorescence-guided surgical resection. WH-N-3 itself is nonfluorescent, and it can only light up through synergistic activation by H2S and in the tumor acidic environment (TEM). Such a "dual-lock-dual-key" strategy-based activatable probe exhibited significantly higher tumor-to-normal tissue (T/N) ratios than the "always on" agent (ICG) and single parameter responsive counterpart probes in the imaging of colon tumors, which overexpresses H2S. WH-N-3 was also able to visualize the tumor-derived endogenous H2S fluctuation and accurately differentiate tumor types based on H2S content discrepancy. More excitingly, under the guidance of the probe's highly specific NIR-II fluorescence, a tiny orthotopic colon tumor with diameter down to 0.8 mm was facilely resected. We expect our dual-stimuli responsive strategy will contribute more reliable tools for specific discrimination and imaging-guided excision of tumor.