Granzyme B activated near-infrared-II ratiometric fluorescent nanoprobe for early detection of tumor response to immunotherapy.

Non-invasive optical imaging tools for early detecting anti-tumor immune responses are crucial for precision cancer immunotherapy. However, current probes often suffer from low imaging depth, single imaging channel, and inadequate quantification, hindering their in vivo applications. Here we develop a rare-earth-based NIR-II fluorescence ratiometric nanoprobe (DCGA) for in vivo real-time, precise, and non-invasive visualization of granzyme B (GzmB) activity, a key effector in T cell-mediated antitumor immunity, for early prediction of immunotherapy efficacy. The Nd/Er co-doped DCGA nanoprobe features NIR-II dual-emission ratiometric detection with self-calibrated target response signals, addressing challenges like uneven probe distribution and nonspecific signal interference. In vivo NIR-II ratiometric imaging reveals that GzmB activity well correlates with cytotoxic T cell responses and tumor growth, and can effectively distinguish responders from non-responders in both Hepa 1-6 tumor xenograft models and patient-derived xenograft models. Our DCGA probe shows promise for dynamic, real-time, non-invasive molecular imaging of T cell activation in deep tissues, offering effective support for tumor immunotherapy studies, precision medicine, and personalized diagnostics.