Photo-induced treatment of breast epithelial cancer cells using nanostructured titanium dioxide solution

The photo-induced bioactivity of titanium dioxide was investigated in terms of determining the conditions for photocatalytic treatment of cancer cells and also exploring the molecular mechanisms involved in this process. Cultured MCF-7 and MDA-MB-468 breast cancer epithelial cells were irradiated, using UV-A light (wavelength 350 nm) for 20 min, in the presence of nanostructured titania aqueous dispersions prepared using the sol–gel technique. Detailed characterization of the titania sols confirmed the presence of the photocatalyst in the form of anatase nanoparticles. Two different techniques were employed to examine the effects on cell cycle and the viability of the treated culture: propidium iodide (PI) flow cytometric (FACScan) assays permitted the identification of treatment effects on the cell cycle and cell viability analysis (MTT assays) allowed the definition of the precise percentage of cells that are still alive and functionable, after the treatment. A selective action of both TiO2 nanoparticles and photocatalytically activated titania was observed on the highly malignant MDA-MB-468 cells. Upon irradiation, these cells were induced to undergo apoptotic cell death, compared to the MCF-7 cells which were still unimpaired. This was profoundly revealed via Western blot analysis. The molecular mechanism of apoptosis is associated at least in part with increase of caspase-3-mediated poly(ADP-ribose) polymerase (PARP) cleavage.