Study on the visible-light-induced photokilling effect of nitrogen-doped TiO2 nanoparticles on cancer cells

Abstract

Nitrogen-doped TiO2 (N-TiO2) nanoparticles were prepared by calcining the anatase TiO2 nanoparticles under ammonia atmosphere. The N-TiO2 showed higher absorbance in the visible region than the pure TiO2. The cytotoxicity and visible-light-induced phototoxicity of the pure- and N-TiO2 were examined for three types of cancer cell lines. No significant cytotoxicity was detected. However, the visible-light-induced photokilling effects on cells were observed. The survival fraction of the cells decreased with the increased incubation concentration of the nanoparticles. The cancer cells incubated with N-TiO2 were killed more effectively than that with the pure TiO2. The reactive oxygen species was found to play an important role on the photokilling effect for cells. Furthermore, the intracellular distributions of N-TiO2 nanoparticles were examined by laser scanning confocal microscopy. The co-localization of N-TiO2 nanoparticles with nuclei or Golgi complexes was observed. The aberrant nuclear morphologies such as micronuclei were detected after the N-TiO2-treated cells were irradiated by the visible light.

Biocompatibility and antibacterial activity of nitrogen-doped titanium dioxide nanoparticles for use in dental resin formulations

“…Furthermore, in a previous study, the same group demonstrated that N-TiO 2 NPs are capable of inducing cytotoxicity and micronuclei formation in three cancer cell lines. 53 There are several notable differences between our study and the studies of Li. One such difference is the intensity and duration of light used among the studies.…”

Controlling silica coating thickness on TiO2 nanoparticles for effective photodynamic therapy

“…Stefanous et al also indicated that photoexcited TiO 2 nanoparticles efficiently inhibited the aggregation of platelets, which led to discontinuation of haematogenous metastasis [8]. The photo-killing effect of nitrogen-doped TiO 2 nanoparticles in the visible region also has been reported [9].…”

Comparison of the killing effects between nitrogen-doped and pure TiO2 on HeLa cells with visible light irradiation

“…The electrons in the valence band of TiO 2 can be excited to the conduction band by ultraviolet (UV) radiation with the wavelength shorter than 387 nm (corresponding to 3.2 eV as the band gap energy of anatase TiO 2 ), thus resulting in the photoinduced hole-electron pairs. These photoinduced electrons and holes can interact with surrounding H 2 O or O 2 molecules and generate various reactive oxygen species (ROS, such as superoxide anion radical O 2  ·− [5], hydroxyl radical OH · [6], singlet oxygen 1 O 2 [7], and hydrogen peroxide H 2 O 2 [8]), which can react with biological molecules, such as lipids, proteins, and DNA, cause their damages, and eventually kill cancer cells [1,9,10]. …”

“…Fortunately, recent studies have reported that the optical absorption of TiO 2 in the visible region could be improved by doping [12-14] or dye-adsorbed methods [15,16], which will facilitate the application of TiO 2 as a photosensitizer for PDT. In our previous study [10], we enhanced the visible light absorption of TiO 2 by nitrogen doping and found that the nitrogen-doped TiO 2 (N-TiO 2 ) showed much higher visible-light-induced photokilling effects on cancer cells than the pure TiO 2 .…”