Photocatalytic and phototoxic properties of TiO₂-based nanofilaments: ESR and AFM assays

Abstract

There is uncertainty in understanding of the relationship between physico-chemical parameters of nanosized titanium dioxide (nano-TiO₂) and its toxicity when brought into contact with living cells. This study provides a multidisciplinary experimental insight into the toxicity and phototoxicity of the custom-made TiO₂-based nanowires (TiO₂-NWs). We employed electron spin resonance (ESR) to detect reactive oxygen species (ROS) generated in aqueous suspensions of TiO₂-NWs and combined these results with atomic force microscopy (AFM) to trace the onset of toxic effects towards human melanoma cells. The cells were treated with low concentrations (∼2.5 μg/ml) of TiO₂-NWs and Degussa P25. High-resolution AFM surface topography and cell elasticity measurements revealed toxic effects both in cells incubated with TiO₂-NWs in the dark and exposed to the photo-oxidative stress under UVA radiation. In contrast to ROS generation efficacy in the absence of cells in vitro, no direct correlation was found between the physical parameters of nano-TiO₂ and cell toxicity.

Keywords::

• Electron spin resonance
• atomic force microscopy
• oxidative stress
• reactive oxygen species
• cell protein staining
• nanotoxicity
• nano-engineered materials, titanium dioxide (TiO₂)

Acknowledgements

The authors are grateful to Prof. Piotr Laidler for providing cell cultures and to Dr. Mireille Crittin for technical advices in performing DLS measurements. The study was partially supported by SNSF project nos. 205320-112164 and IZ73Z0_128068/1 (SCOPES).