Using gold-nanorod-filled mesoporous silica nanobeads for enhanced radiotherapy of oral squamous carcinoma

Radiotherapy (RT), in combination with surgery, is an essential treatment strategy for oral cancer. Although irradiation provides effective control over tumor growth, the surrounding normal tissues are almost inevitably affected. With further understanding of the molecular mechanisms involved in radiation response and recent advances in nanotechnology, using gold nanoparticles as a radiosensitizer provides the preferential sensitization of tumor cells to radiation and minimizes normal tissue damage. Herein, we developed gold nano-sesame-beads (GNSbs), a gold-nanorod-seeded mesoporous silica nanoparticle, as a novel radioenhancer to achieve radiotherapy with a higher therapeutic index. GNSbs in combination with 2 Gy irradiation effectively enhanced the cytotoxic activity CAL-27 cells. The well-designed structure of GNSbs showed preferential cellular uptake by CAL-27 cells at 24 h after incubation. Gold nanorods with high density modified on mesoporous silica nanoparticles resulted in significant reactive oxygen species (ROS) formation after irradiation exposure compared with irradiation alone. Furthermore, GNSbs and irradiation induced more prominent DNA double-strand breaks and G2/M phase arrest in CAL-27 than those in L929. In animal studies, radiotherapy using GNSbs as a radiosensitizer showed significant suppression of tumor growth in an orthotopic model of oral cancer. These results demonstrate that using GNSbs as a radiosensitizer could possess clinical potential for the treatment of oral squamous carcinoma.