Can the Ames test provide an insight into nano-object mutagenicity? Investigating the interaction between nano-objects and bacteria

Abstract

The aim of this study was to assess the interaction of a series of well characterised nano-objects with the Gram negative bacterium Salmonella typhimurium, and how such an interaction may relate to the potential mutagenicity of nano-objects. Transmission electron microscopy showed that nano-objects (Au-PMA-ATTO NPs, CeO₂ NPs, SWCNTs and MWCNTs), as well as CAFs entered S. typhimurium. Only DEPs did not penetrate/enter the bacteria, however, were the only particle stimulus to induce any significant mutagenicity through the Ames test. Comparison with a sophisticated 3D in vitro cell model showed CAFs, DEPs, SWCNTs and MWCNTs to cause a significant increase in mammalian cell proliferation, whilst both the Au-PMA-ATTO NPs and CeO₂ NPs had not significant adverse effects. In conclusion, these results indicate that various of different nano-objects are able to penetrate the double-lipid bilayer of Gram negative bacteria, although the Ames test may not be a good indicator for nano-object mutagenicity.

Keywords::

• nano-object(s)
• nano-bacterial interactions
• mutagenicity
• Ames test
• mammalian cells

Acknowledgements

The authors thank Prof. Dr. T. Seebeck (Institute for Cell Biology, University of Bern) for the use of his bacterial culture facilities, as well as Prof. Dr. W. Stark (ETH, Zurich) for his kind donation of the CeO₂ NPs. The Dr. Alfred Bretscher fund and the Microscopy Imaging Center (University of Bern) are also acknowledged for the use of the Tecnai F20 TEM. The authors acknowledge M. Ouanella and A. Stokes for their valuable technical assistance in all TEM sample preparation. In addition, the authors also acknowledge financial support from the European Respiratory Society (Fellowship LTRF-MC1572-2010 to Dr. MJD CLIFT), the Swiss National Science Foundation (320030_ 138365), the German Research Foundation (DFG SPP 1313) and the Adolphe Merkle Foundation.