Convertible ROS Nanocatalyst/Eliminator for Enhancing Tumor Radio‐Immunotherapy and Relieving Radiation Enteritis

Abstract Radiation‐induced damage to normal tissue seriously disrupts the execution of radiotherapy (RT) and therefore attenuates its efficacy. Exploring new strategies to enhance the efficacy and reduce toxicity of RT has great clinical importance. Here, a PD‐L1 affibody (Z _PD‐L1 ) grafted Janus Ag/Ag ₂ S nanoarchitectures is developed as “reactive oxygen species lever” to enhance radiocatalysis and relieve radiation enteritis. The nanoplatform can achieve abundant energy deposition in the form of high‐energy electrons within tumors upon X‐ray exposure. Subsequently, the transfer of electrons from Ag ₂ S to Ag moiety enables effective electron–hole pair separation, which greatly improves the radiocatalysis efficiency in generating highly toxic hydroxyl radical (•OH). Due to the specific binding to tumor PD‐L1, Z _PD‐L1 endows this nanoplatform with efficient tumor targeting and meanwhile reduces immune suppression of T cells by achieving PD‐1/PD‐L1 blockade, intensifying RT‐induced immunologic cell death. Notably, the presence of the Ag moiety allows the nanoplatform to act as an H ₂ O ₂ scavenger in intestinal tissues during metabolism, effectively relieving radiation enteritis. Moreover, systemic administration of the nanoplatform coupled with Mn‐DOTA can guide RT timing selection by magnetic resonance imaging. Overall, this nanoplatform can substantially improve RT effectiveness with reduced radiation enteritis, demonstrating considerable potential in tumor RT.