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

Li Z, Mi L, Wang PN, Chen JY - Nanoscale Res Lett (2011)

Bottom Line: 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 reactive oxygen species was found to play an important role on the photokilling effect for cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China. lanmi@fudan.edu.cn.

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.

No MeSH data available.


Related in: MedlinePlus

Micrographs of the distributions of nuclei and TiO2 nanoparticles in HeLa cells. (a) the distribution of nuclei (blue), (b) the distribution of TiO2 nanoparticles (red), (c) DIC micrograph, and (d) the merged image of (a), (b), and (c), in which the violet color denotes the co-localization of TiO2 nanoparticles with nuclei. The images displayed at the bottom and right side of (d) were the X-Z and Y-Z profiles measured along the lines marked in the main image, showing the 3D distributions of TiO2 nanoparticles and nuclei.
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Figure 5: Micrographs of the distributions of nuclei and TiO2 nanoparticles in HeLa cells. (a) the distribution of nuclei (blue), (b) the distribution of TiO2 nanoparticles (red), (c) DIC micrograph, and (d) the merged image of (a), (b), and (c), in which the violet color denotes the co-localization of TiO2 nanoparticles with nuclei. The images displayed at the bottom and right side of (d) were the X-Z and Y-Z profiles measured along the lines marked in the main image, showing the 3D distributions of TiO2 nanoparticles and nuclei.

Mentions: As is well-known, light-excited TiO2 generates the electron-hole (e-/h+) pairs. The photogenerated carriers migrate to the particle surface and participate in various redox reactions there. Hence, the direct damage induced by photokilling effect would only occur at the sites of TiO2 particles. Therefore, it is of importance to know if the TiO2 nanoparticles were internalized into cells and how their intracellular distributions were. To find out the subcellular distribution of TiO2 nanoparticles, the TiO2-treated HeLa cells were stained with fluorescence indicators for Golgi complex and nucleus, respectively. Surprisingly, some TiO2 nanoparticles were found inside the nuclei as shown in Figure 5, where the HeLa cells were treated with (N-550-2, 50 μg/mL) and stained with nuclear indicator. When these N-TiO2-treated cells were irradiated by light from the Xe lamp with a 400-nm longpass filter (12 mW/cm2) for 4 h, some micronuclei were observed as shown in Figure 6. Since the TiO2 nanoparticles had entered into the nuclei of cells, the photoactivation effect could occur directly inside the nuclei, which might cause chromosomal damage or nucleus aberration. Micronuclei are usually formed from a chromosome or a fragment of a chromosome not incorporated into one of the daughter nuclei during cell division. This is an evidence of the direct damage to the nucleus resulted from the photoexcited N-TiO2 nanoparticles.


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

Li Z, Mi L, Wang PN, Chen JY - Nanoscale Res Lett (2011)

Micrographs of the distributions of nuclei and TiO2 nanoparticles in HeLa cells. (a) the distribution of nuclei (blue), (b) the distribution of TiO2 nanoparticles (red), (c) DIC micrograph, and (d) the merged image of (a), (b), and (c), in which the violet color denotes the co-localization of TiO2 nanoparticles with nuclei. The images displayed at the bottom and right side of (d) were the X-Z and Y-Z profiles measured along the lines marked in the main image, showing the 3D distributions of TiO2 nanoparticles and nuclei.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211446&req=5

Figure 5: Micrographs of the distributions of nuclei and TiO2 nanoparticles in HeLa cells. (a) the distribution of nuclei (blue), (b) the distribution of TiO2 nanoparticles (red), (c) DIC micrograph, and (d) the merged image of (a), (b), and (c), in which the violet color denotes the co-localization of TiO2 nanoparticles with nuclei. The images displayed at the bottom and right side of (d) were the X-Z and Y-Z profiles measured along the lines marked in the main image, showing the 3D distributions of TiO2 nanoparticles and nuclei.
Mentions: As is well-known, light-excited TiO2 generates the electron-hole (e-/h+) pairs. The photogenerated carriers migrate to the particle surface and participate in various redox reactions there. Hence, the direct damage induced by photokilling effect would only occur at the sites of TiO2 particles. Therefore, it is of importance to know if the TiO2 nanoparticles were internalized into cells and how their intracellular distributions were. To find out the subcellular distribution of TiO2 nanoparticles, the TiO2-treated HeLa cells were stained with fluorescence indicators for Golgi complex and nucleus, respectively. Surprisingly, some TiO2 nanoparticles were found inside the nuclei as shown in Figure 5, where the HeLa cells were treated with (N-550-2, 50 μg/mL) and stained with nuclear indicator. When these N-TiO2-treated cells were irradiated by light from the Xe lamp with a 400-nm longpass filter (12 mW/cm2) for 4 h, some micronuclei were observed as shown in Figure 6. Since the TiO2 nanoparticles had entered into the nuclei of cells, the photoactivation effect could occur directly inside the nuclei, which might cause chromosomal damage or nucleus aberration. Micronuclei are usually formed from a chromosome or a fragment of a chromosome not incorporated into one of the daughter nuclei during cell division. This is an evidence of the direct damage to the nucleus resulted from the photoexcited N-TiO2 nanoparticles.

Bottom Line: 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 reactive oxygen species was found to play an important role on the photokilling effect for cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China. lanmi@fudan.edu.cn.

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.

No MeSH data available.


Related in: MedlinePlus