Enhanced melanoma cell-killing by combined phototherapy/radiotherapy using a mesoporous platinum nanostructure

Background: Metal nanomaterials have a significant potential as photosensitizer and radiosensitizer. The purpose of this study was to evaluate the cytotoxicity of a platinum mesoporous nanostructure (Pt MN) toward a melanoma cancer cell line upon combined laser radiation (808 nm, 1 and 1.5 W cm(-2)) and X-ray irradiation (6 MV, 2, 4, and 6 Gy). Methods: Pt MN was synthesized by a simple procedure and characterized by field emission scanning and transmission electron microscopy. A mouse malignant melanoma cell line C540 (B16/F10) was treated with Pt MN, laser light and/or X-ray. Results: Pt MN had a mesoporous structure with a sponge-resemble shape comprised of ensembles of very small adhered particles of < 11 nm and about 5-nm pores. While Pt MN represented a low toxicity toward and considerable uptake into the cell line in a concentration range of 10-100 mu g mL(-1), laser light radiation alone was also not toxic, and X-ray irradiation alone induced a limited toxicity, Pt MN was toxic against the cells in a dose dependent manner upon laser light radiation, X-ray irradiation, or their combined exposure. The killing efficacy of Pt MN upon X-ray irradiation was more obvious at 72 h post-treatment. The combined exposure (laser radiation followed by X-ray irradiation) led to a deep cell killing and a very low melanoma cell viability (similar to 1%). Significant melanoma cancer cell killing of Pt MN was due to reactive oxygen species (ROS) production upon combined exposure of laser and X-ray, while cell killing upon laser light radiation was due to heat generation. Conclusion: Pt MN was introduced as a supreme laser/X-ray sensitizer for treatment of cancer with a high ability to produce ROS and a potent impact on decreasing cell viability.