Carbon-Doped TiO2 Activated by X-Ray Irradiation for the Generation of Reactive Oxygen Species to Enhance Photodynamic Therapy in Tumor Treatment

Abstract

Traditional photodynamic therapy (PDT) is limited by the penetration depth of visible light. Although the light source has been changed to near infrared, infrared light is unable to overcome the penetration barrier and it is only effective at the surface of the tumors. In this study, we used X-ray as a light source for deep-seated tumor treatment. A particle with a narrow band gap when exposed to soft X-rays would produce reactive oxygen species (ROS) to kill tumor cell, with less damage to the normal tissues. Anatase TiO2 has been studied as a photosensitizer in PDT. In the experiment, C was doped into the anatase lattice at an optimum atomic ratio to make the band gap narrower, which would be activated by X-ray to produce more ROS and kill tumor cells under stress. The results showed that the synthesized TiO2:C particles were identified as crystal structures of anatase. The synthesized particles could be activated effectively by soft X-rays to produce ROS, to degrade methylene blue by up to 30.4%. Once TiO2:C was activated by X-ray irradiation, the death rate of A549 cells in in vitro testing was as high as 16.57%, on day 2. In the animal study, the tumor size gradually decreased after treatment with TiO2:C and exposure to X-rays on day 0 and day 8. On day 14, the tumor declined to nearly half of its initial volume, while the tumor in the control group was twice its initial volume. After the animal was sacrificed, blood, and major organs were harvested for further analysis and examination, with data fully supporting the safety of the treatment. Based on the results of the study, we believe that TiO2:C when exposed to X-rays could overcome the limitation of penetration depth and could improve PDT effects by inhibiting tumor growth effectively and safely, in vivo.

Chrysin induces autophagy through the inactivation of the ROS‑mediated Akt/mTOR signaling pathway in endometrial cancer

“…At low concentrations, ROS act as signaling molecules involved in promoting cell survival and proliferation, whereas at high concentrations, they induce programmed cell apoptosis and necrosis (35,36). Previously published studies noted that the excessive accumulation of high levels of ROS may trigger cancer cell apoptosis and death and may inhibit cancer progression during enhanced oxidative stress injury (37)(38)(39). Thus, it was concluded that, in the process of cancer progression, the analysis of ROS level fluctuation may be of importance for cancer prevention and treatment.…”

Nanocomposites for X-Ray Photodynamic Therapy

“…TiO 2 :C. Chun-Chen Young and his co-authors [36] investigated nanoparticles with a narrow bandgap and ROS generation under the influence of soft X-ray radiation to destroy tumor cells with less damage to healthy tissues. In this experiment, anatase lattice was doped with C, and then it was activated by X-rays to produce more reactive oxygen species and destroy tumor cells.…”

Photodynamic Therapy of Inorganic Complexes for the Treatment of Cancer†

“…In addition, the in vivo study also confirmed a low A459 cancer cells viability by ROS generation. Overall, TiO 2 :C inhibited cancer growth efficiently and improved PDT effects (49).…”