Boosting the Radiosensitizing and Photothermal Performance of Cu 2-x Se Nanocrystals for Synergetic Radiophotothermal Therapy of Orthotopic Breast Cancer.

The small difference between tumor and normal tissues in their responses to ionizing radiation has been a significant issue for radiotherapy of tumors. Herein, we report that dumbbell-shaped heterogeneous copper selenide-gold nanocrystals can serve as an efficient radiosensitizer for enhanced radiotherapy. The mean lethal dose of X-rays to 4T1 tumor cells can be drastically decreased about 40%, i.e., decreasing from 1.81 Gy to 1.10 Gy after culture with heterostructures. Due to the synergetic effect of heterostructures, the dose of X-rays is also much lower than those obtained from mixture of Cu2-x Se + Au nanoparticles (1.78 Gy), Cu2-x Se nanoparticles (1.72 Gy) and Au nanoparticles (1.50 Gy), respectively. We demonstrate that the sensitivity enhancement ratio of Cu2-x Se nanoparticles was significantly improved 45% (i.e., from 1.1 to 1.6) after the formation of heterostructures with gold. We also show that the hetero-nanocrystals exhibit an enhanced photothermal conversion efficiency, due to the synergetic interactions of localized surface plasmon resonance. These properties highly feature them as a multimodal imaging contrast agent (particular for photoacoustic imaging, computed tomography imaging, and single photon emission computed tomography after labeled with radioisotopes) and as a radiosensitizer for imaging guided synergetic radiophotothermal treatment of cancer. The research provides insights for engineering low-Z nanomaterials with high Z elements to form hetero-nanostructures with enhanced synergetic performance for tumor theranostics.