Radioprotectant-loaded visualizable cationic radioactive microspheres: Reduced hepatic tissue damage and intra/postoperative imaging during TARE

Embolization is an effective treatment modality for intermediate- and advanced-stage Hepatocellular carcinoma (HCC). Transarterial radioembolization (TARE), which combines radiotherapy with embolization, not only induces tumor necrosis by occluding blood flow with embolic agents but also exerts local radiotherapeutic effects to damage tumor cells, thereby significantly enhancing the therapeutic efficacy of embolization. Current radiolabeled microspheres used for internal irradiation therapy in HCC have limitations, such as suboptimal embolization efficacy, a tendency for non-target embolization, an inability to track embolic agents during and after surgery, and the generation of reactive oxygen species (ROS) during radiotherapy, which can damage normal tissues. To address these issues, visualizable cationic quaternary ammonium salt-based drug-eluting microspheres capable of loading ¹³¹I and the radioprotective agent amifostine were developed. The microspheres exhibit good embolic properties and can be visualized over an extended period using CT and DSA. The microspheres, carrying a positive charge, are capable of loading amifostine via ion exchange. After loading amifostine, these microspheres can not only provide local radiotherapy within the tumor but also continuously release amifostine locally to neutralize ROS in normal liver tissue. This approach not only enhances the utilization of amifostine in vivo but also protects the liver without compromising the efficacy of TARE thereby further improving the precision of radiotherapy.