Stimuli-responsive copper-iodide nanoparticles for low-dose X-ray-induced photodynamic therapy and enhanced cuproptosis.

High-dose radiotherapy is known to enhance cuproptosis, and when combined with copper-coordinated delivery to tumors, it shows promise as a synergistic treatment mechanism. In this study, we present a simple method for synthesizing stimuli-responsive copper-iodide nanoparticles using a commercial, insoluble copper-iodide powder that emitted a strong radioluminescence matching the absorbance of the clinical dye indocyanine green. The copper-iodide nanoparticles efficiently absorbed and transferred radiation energy to ICG activating an X-ray-induced photodynamic therapy (X-PDT) mechanism. After accumulating in tumors, the low-dose X-PDT process first generated reactive oxygen species to induce cell death. The tumor microenvironment then caused the copper-iodide nanoparticles to decompose and release copper and iodide ions, which promoted cuproptosis. X-PDT followed by ion-induced cell death achieved 87.7% tumor regression in CT26 tumor-bearing mice without systemic toxicity. This work establishes a therapeutic paradigm that exploits metal metabolism dysregulation to potentiate radiation-based therapies. STATEMENT OF SIGNIFICANCE: Stimuli-responsive copper-iodide nanoparticles were synthesized and induced by X-ray-induced photodynamic therapy to decompose, releasing copper and iodide ions that caused tumor cell death. (1) Commercial copper-iodide powder exhibited strong radioluminescent properties and formed stable nanoparticles with the clinical dye indocyanine green, which realized X-ray-induced photodynamic therapy under X-ray irradiation. (2) After accumulating in tumors and following X-ray-induced photodynamic therapy, the decomposition of copper-iodide nanoparticles in the tumor tissue induced cell death.