Titanium dioxide nanoparticles induced intracellular calcium homeostasis modification in primary human keratinocytes. Towards an in vitro explanation of titanium dioxide nanoparticles toxicity

Abstract

Deciphering the molecular basis of toxicology mechanism induced by nanoparticles (NPs) remains an essential challenge. Ion Beam Analysis (IBA) was applied in combination with Transmission Electron Microscopy and Confocal Microscopy to analyze human keratinocytes exposed to TiO₂-NPs. Investigating chemical elemental distributions using IBA gives rise to a fine quantification of the TiO₂-NPs uptake within a cell and to the determination of the intracellular chemical modifications after TiO₂-NPs internalization. In addition, fluorescent dye-modified TiO₂-NPs have been synthesized to allow their detection, precise quantification and tracking in vitro. The internalization of these TiO₂-NPs altered the calcium homeostasis and induced a decrease in cell proliferation associated with an early keratinocyte differentiation, without any indication of cell death. Additionally, the relation between the surface chemistry of the TiO₂-NPs and their in vitro toxicity is clearly established and emphasizes the importance of the calcium homeostasis alteration in response to the presence of TiO₂-NPs.

Keywords::

• Titanium dioxide
• nanoparticles
• cytotoxicity
• calcium homeostasis
• cellular imaging

Acknowledgements

The authors acknowledge P. Legros and C. Poujol, from PICIN, for their helpful and friendly assistance in fluorescence microscopy techniques. Authors wish to acknowledge E. Gontier at the Pôle Microscopie Electronique/Bordeaux 2, for his assistance in TEM techniques. We also wish to thank the technical staff members of the AIFIRA facility. The AIFIRA facility and the technical development of the microbeam line have been financially supported by the Région Aquitaine. Special thanks to R. Ortega, A. Carmona and G. Devès (CNAB) for their technical support, assistance and scientific discussion. The authors acknowledge the Evonik (Degussa) Company (Düsseldorf, Germany) for their generous gift (P25 TiO₂-NPs). This work and M.S. were supported by Institut de Recherche Pierre Fabre (Vigoulet-Auzil, Castanet-Tolosan).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.