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

Abstract

The killing effect of nitrogen-doped titanium dioxide (N-TiO2) nanoparticles on human cervical carcinoma (HeLa) cells by visible light photodynamic therapy (PDT) was higher than that of TiO2 nanoparticles. To study the mechanism of the killing effect, the reactive oxygen species produced by the visible-light-activated N-TiO2 and pure-TiO2 were evaluated and compared. The changes of the cellular parameters, such as the mitochondrial membrane potential (MMP), intracellular Ca2+, and nitrogen monoxide (NO) concentrations after PDT were measured and compared for N-TiO2- and TiO2-treated HeLa cells. The N-TiO2 resulted in more loss of MMP and higher increase of Ca2+ and NO in HeLa cells than pure TiO2. The cell morphology changes with time were also examined by a confocal microscope. The cells incubated with N-TiO2 exhibited serious distortion and membrane breakage at 60 min after the PDT.

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

“…There was a significant change in ROS production between ambient and blue light treatments after exposure to the highest dosage (200 μg/mL) of N-TiO 2 NPs. Although there are relatively few investigations which report on ROS production of N-TiO 2 NPs in mammalian cell models, our ROS results match those described in Li et al's report, 48 which compared the cytotoxicity of undoped and N-doped TiO 2 NPs in HeLa cells. In the aforementioned studies, irradiation with blue light (400-440 nm) for up to 5 minutes resulted in substantial increases in total ROS as well as superoxide and hydroxyl radical formation at similar concentrations to those used in our study.…”

“…Some reports agree with our finding that superoxide radicals are produced, 30,48 while others indicate that carbon-centered radicals are produced. 19 Nonetheless, the presence of free radicals indicates that cells may be exposed to conditions that promote oxidative stress, which could result in adverse cellular responses including cell death.…”

Nanoparticles and Bacteria

“…Preliminary tests in the laboratory demonstrated that the procedure is efficient and several improvements have already been suggested [11]. Nevertheless, such an approach can be used solely for few cancers, where the activation by visible of UV light is possible.…”

“…The production of ROS by semiconducting/conducting nanoparticle (such as TiO 2 ) and light in cell cultures (human cervical carcinoma cells HeLa) has been confirmed [11]. A study aiming directly at TiO 2 exposed to H 2 O 2 in ambient light and dark demonstrated that free oxygen containing radicals (ROS) could be generated in the absence of light if H 2 O 2 is present.…”

“…An alternative path to decrease the energy gap implies the doping of the semiconductor. For example, the doping of TiO 2 by nitrogen reduced the energy gap and additionally allowed for the photoproduction of *NO [11]. By increasing the temperature towards room temperature, the electrons from the valence band may receive sufficient energy to be promoted into the conduction band.…”