Figure 1. . Schematic illustration of x-ray-activated photodynamic therapy with copper-cysteamine nanoparticles.

Compared with visible light, x-rays can penetrate through the epidermis and dermis to the hypodermis. Upon the irradiation of x-rays, ROS produced by Cu-Cy NPs and ionizing irradiation are generated in the whole tumor. The photodynamic effect and radiotherapy exert the antitumor effect at the same space and time to override tumor cell repairs and lead to the deep tumor vascular effect.

Cu-Cy NP: Copper-cysteamine nanoparticle; C-PDT: Conventional photodynamic therapy; PS: Photosensitizer; ROS: Reactive oxygen species; X-PDT: X-ray-activated photodynamic therapy.