© 2014 Lagopati et al. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution – Non Commercial (unported, v3.0) License. The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. Permissions beyond the scope of the License are administered by Dove Medical Press Limited. Information on how to request permission may be found at: http://www.dovepress.com/permissions.php International Journal of Nanomedicine 2014:9 3219–3230 International Journal of Nanomedicine Dovepress submit your manuscript | www.dovepress.com Dovepress 3219 OrIgINal research open access to scientific and medical research Open access Full Text article http://dx.doi.org/10.2147/IJN.S62972 effect of nanostructured TiO 2 crystal phase on photoinduced apoptosis of breast cancer epithelial cells correspondence: Paraskevi Kitsiou Institute of Biosciences and applications, National Center for Scientifc Research “Demokritos”, corner Patriarchou grigoriou and Neapoleos streets, aghia Paraskevi, attiki, athens 15310, greece Tel +30 21 0650 3615 Fax +30 21 0651 1767 email pkit@bio.demokritos.gr Nefeli lagopati 1,2 effi e-Photini Tsilibary 1, * Polycarpos Falaras 2, * Panagiota Papazafiri 3 evang elia a Pavlatou 4 el eni Kotsopoulou 1 Paraskevi Kitsiou 1, * 1 Institute of Biosciences and applications, 2 Institute of advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, National center for scientific research “Demokritos”, athens, greece; 3 Department of animal and human Physiology, Faculty of Biology, school of science, National and Kapodistrian University of athens, athens, greece; 4 laboratory of general chemistry, school of chemi cal engineering, National Technical University of athens, athens, greece *These authors contributed equally to this work Purpose: The use of nanoparticles has seen exponential growth in the area of health care, due to the unique physicochemical properties of nanomaterials that make them desirable for medical applications. The aim of this study was to examine the effects of crystal phase-nanostructured titanium dioxide particles on bioactivity/cytotoxicity in breast cancer epithelial cells. Materials and methods: Cultured Michigan Cancer Foundation (MCF)-7 and human breast adenocarcinoma (MDA-MB-468) breast cancer epithelial cells were exposed to ultraviolet A light (wavelength 350 nm) for 20 minutes in the presence of aqueous dispersions of two different nanostructured titanium dioxide (TiO 2 ) crystal phases: anatase and an anatase–rutile mixture. Detailed characterization of each titanium dispersion was performed by dynamic light scattering. A 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) colorimetric assay was employed to estimate the percentage of viable cells after each treatment. Western blot analysis of protein expression and characterization, as well as a deoxyribonucleic acid (DNA)-laddering assay, were used to detect cell apoptosis. Results: Our results documented that 100% anatase TiO 2 nanoparticles (110–130 nm) exhibited significantly higher cytotoxicity in the highly malignant MDA-MB-468 cancer cells than anatase– rutile mixtures (75%/25%) with the same size. On the contrary, MCF-7 cells (characterized by low invasive properties) were not considerably affected. Exposure of MDA-MB-468 cells to pure anatase nanoparticles or anatase–rutile mixtures for 48 hours resulted in increased proapoptotic Bax expression, caspase-mediated poly(adenosine diphosphate ribose) polymerase (PARP) cleavage, DNA fragmentation, and programmed cell death/apoptosis. Conclusion: The obtained results indicated that pure anatase TiO 2 nanoparticles exhibit superior cytotoxic effects compared to anatase–rutile mixtures of the same size. The molecular mecha- nism of TiO 2 nanoparticle cytotoxicity involved increased Bax expression and caspase-mediated PARP inactivation, thus resulting in DNA fragmentation and cell apoptosis. Keywords: nanostructured TiO 2 , anatase, rutile, photocatalysis, breast cancer epithelial cells, apoptosis Introduction Nanoparticles have unique physicochemical properties and functionalities that are dif- ferent from their bulk counterparts. 1,2 In recent years, there has been increased concern about nanotoxicology and the factors that are intertwined with it. Due to the importance of this size class of particles, there is a need for clarification and better understanding of nanoparticle physicochemical properties and their cytotoxic potential. 3–5 Titanium is widely used in biomedical applications, due to its mechanical proper- ties and biocompatibility, and of course for photocatalysis purposes. 6,7 It is now well established that photoexcited titanium dioxide (TiO 2 ) can drive various chemical International Journal of Nanomedicine downloaded from https://www.dovepress.com/ by 3.89.197.24 on 14-Dec-2021 For personal use only.