Redox-Programmed Activation of a Dual-Modal Probe for High-Fidelity Tumor Delineation and Image-Guided Surgery

The nonspecific activation of activatable probes presents significant challenges in their applications for accurate cancer detection, leading to false signals in normal tissues and the potential oversight of microlesions. To address this issue, we developed a glutathione (GSH)-activatable magnetic resonance imaging (MRI) and near-infrared II (NIR-II) fluorescent probe (GAP9) using a redox capacity engineering strategy. By systematically adjusting the reaction pH during probe synthesis, we could precisely modulate its oxidation capacity to ensure that the activation window of the probe precisely matched tumor GSH concentrations. This strategy ensures that GAP9 remains in the "OFF" state within normal tissues through dual MRI/NIR-II quenching mechanisms, minimizing false-positive signals and background noise. Upon reaching tumor sites, GAP9 undergoes GSH-triggered disassembly, rapidly activating T1-weighted MRI for preoperative tumor mapping and unlocking NIR-II fluorescence for real-time intraoperative tumor delineation. This tumor-adaptable strategy enables the specific localization of microtumor lesions, intraoperative margin monitoring, and complete excision of ultrasmall residual foci ≤1 mm, achieving a 96% detection rate in a mouse model of peritoneal metastasis. This study presents a novel paradigm in molecular probe design, emphasizing the potential of integrating programmable redox chemistry with tumor-specific characteristics to enhance detection accuracy, ultimately improving surgical outcomes and patient prognoses.