An Activatable Dye‐Sensitized Lanthanide Nanoprobes With Enhanced NIR‐II Luminescence for In Vivo Inflammation Imaging

Accurate detection of neutrophil activity is critical for assessing the severity of bacterial inflammation. Herein, we report an activatable dye-sensitized lanthanide nanoprobe (LnNP@ZW800-SC@PEG) with enhanced second near-infrared fluorescence for the real-time imaging of neutrophil-secreted hypochlorite in vivo. By screening of four cyanine derivatives, LnNP@ZW800-SC is identified with the brightest fluorescence at 1523 nm and the high absolute quantum yield (0.85%) compared to other derivatives. Mechanistic studies reveal that the high conjugation efficiency and enhanced absorption of the ZW800-SC dyes facilitate efficient energy transfer to Yb³⁺ and Er³⁺, leading to boosted NIR-IIb emission. Leveraging the bright emission, LnNP@ZW800-SC enables high-resolution, sensitive, and specific imaging of hypochlorite, both in vitro and in a murine model of LPS-induced lymphatic inflammation. This work provides a rational design strategy for coordinating dye moieties to enhance dye sensitization, thereby boosting the second near-infrared fluorescence of lanthanides and optimizing their imaging performance for biological applications.