A new X-ray activated nanoparticle photosensitizer for cancer treatment.

Photodynamic therapy (PDT) has attracted ever-growing attention as a promising modality in the treatment of cancer. However, due to the poor tissue penetration by light, PDT has rarely been applied for treating deep-seated tumors. This problem can be solved if photosensitizers are activated by X-rays, which are able to penetrate deeply into tissues. Previous attempts using X-rays to activate photosensitizers were not very successful, since the traditional PDT photosensitizers could not efficiently be activated with X-rays. Here we exploit copper-cysteamine complex (Cu-Cy) nanoparticles as a new type of photosensitizer activated by X-ray for cancer treatment. The newly invented Cu-Cy nanoparticles can be activated directly by X-rays to produce singlet oxygen. In vitro and in vivo study on human breast cancer cells (MCF-7) have shown significant cell destruction using Cu-Cy nanoparticles under X-ray activation. The Cu-Cy nanoparticles are a novel and potent X-ray activated photosensitizer which can enable PDT for deep cancer treatment.