Low Dose Soft X‐Ray Remotely Triggered Lanthanide Nanovaccine for Deep Tissue CO Gas Release and Activation of Systemic Anti‐Tumor Immunoresponse

Abstract Gas‐based therapy has emerged as a new green therapy strategy for anti‐tumor treatment. However, the therapeutic efficacy is still restricted by the deep tissue controlled release, poor lymphocytic infiltration, and inherent immunosuppressive tumor microenvironment (TME). Herein, a new type of nanovaccine is designed by integrating low dose soft X‐ray‐triggered CO releasing lanthanide scintillator nanoparticles (ScNPs: NaLuF₄:Gd,Tb@NaLuF₄) with photo‐responsive CO releasing moiety (PhotoCORM) for synergistic CO gas/immuno‐therapy of tumors. The designed nanovaccine presents significantly boosted radioluminescence and enables deep tissue CO generation at unprecedented tissue depths of 5 cm under soft X‐ray irradiation. Intriguingly, CO as a superior immunogenic cell death (ICD) inducer further reverses the deep tissue immunosuppressive TME and concurrently activates adaptive anti‐tumor immunity through efficient reactive oxygen species (ROS) generation. More importantly, the designed nanovaccine presents efficient growth inhibition of both local and distant tumors via a soft X‐ray activated systemic anti‐tumor immunoresponse. This work provides a new strategy of designing anti‐tumor nanovaccines for synergistic deep tissue gas‐therapy and remote soft X‐ray photoactivation of the immune response.