Cationic Metal‐Organic Layer Delivers siRNAs to Overcome Radioresistance and Potentiate Cancer Radiotherapy

Abstract Radiotherapy plays an important role in modern oncology, but its treatment efficacy is limited by the radioresistance of tumor cells. As a member of the inhibitor of apoptosis protein family, survivin plays a key role in developing radioresistance by mediating apoptosis evasion, promoting epithelial‐mesenchymal transition, and modulating cell cycle dynamics. Efficient downregulation of survivin expression presents a promising strategy to enhance the antitumor effects of radiotherapy. Herein, we report the design of a hafnium‐porphyrin‐based cationic metal‐organic layer (CMOL) with quaternary ammonium capping groups to deliver small interfering RNAs (siRNAs) for enhanced radiotherapy. The CMOL@siRNA nanoplatform not only increased energy deposition from X‐rays and reactive oxygen species generation via a unique radiotherapy‐radiodynamic therapy process, but also effectively delivered siRNAs to downregulate survivin expression and ameliorate radioresistance of cancer cells. Consequently, CMOL@siRNA in combination with low‐dose X‐ray irradiation demonstrated remarkable antitumor efficacy with 96.9 % and 91.4 % tumor growth inhibition in murine colorectal carcinoma and triple‐negative breast cancer models, respectively.