An Ultra‐Stable, Oxygen‐Supply Nanoprobe Emitting in Near‐Infrared‐II Window to Guide and Enhance Radiotherapy by Promoting Anti‐Tumor Immunity

Abstract Currently, radiotherapy (RT) is the main method for cancer treatment. However, the hypoxic environment of solid tumors is likely to cause resistance or failure of RT. Moreover, high‐dose radiation may cause side effects to surrounding normal tissues. In this study, a new type of nanozyme is developed by doping Mn (II) ions into Ag₂Se quantum dots (QDs) emitting in the second near‐infrared window (NIR‐II, 1000–1700 nm). Through the catalysis of Mn (II) ions, the nanozymes can trigger the rapid decomposition of H₂O₂ and produce O₂. Conjugated with tumor‐targeting arginine‐glycine‐aspartate (RGD) tripeptides and polyethylene glycol (PEG) molecules, the nanozymes are then constructed into in vivo nanoprobes for NIR‐II imaging‐guided RT of tumors. Owing to the radiosensitive activity of the element Ag, the nanoprobes can promote radiation energy deposition. The specific tumor‐targeting and NIR‐II emitting abilities of the nanoprobes facilitate the precise tumor localization, which enables precise RT with low side effects. Moreover, their ultra‐stability in the living body ensures that the nanoprobes continuously produce oxygen and relieve the hypoxia of tumors to enhance RT efficacy. Guided by real‐time and high‐clarity imaging, the nanoprobe‐mediated RT promotes anti‐tumor immunity, which significantly inhibits the growth of tumors or even cures them completely.