The effects of engineered nanoparticles on the cellular structure and growth of Saccharomyces cerevisiae

Abstract

In order to study the effects of nanoparticles (NPs) with different physicochemical properties on cellular viability and structure, Saccharomyces cerevisiae were exposed to different concentrations of TiO₂-NPs (1–3 nm), ZnO-NPs (<100 nm), CuO-NPs (<50 nm), their bulk forms, Ag-NPs (10 nm) and single-walled carbon nanotubes (SWCNTs). The GreenScreen assay was used to measure cyto- and genotoxicity, and transmission electron microscopy (TEM) used to assess ultrastructure. CuO-NPs were highly cytotoxic, reducing the cell density by 80% at 9 cm²/ml, and inducing lipid droplet formation. Cells exposed to Ag-NPs (19 cm²/ml) and TiO₂-NPs (147 cm²/ml) contained dark deposits in intracellular vacuoles, the cell wall and vesicles, and reduced cell density (40 and 30%, respectively). ZnO-NPs (8 cm²/ml) caused an increase in the size of intracellular vacuoles, despite not being cytotoxic. SWCNTs did not cause cytotoxicity or significant alterations in ultrastructure, despite high oxidative potential. Two genotoxicity assays, GreenScreen and the comet assay, produced different results and the authors discuss the reasons for this discrepancy. Classical assays of toxicity may not be the most suitable for studying the effects of NPs in cellular systems, and the simultaneous assessment of other measures of the state of cells, such as TEM are highly recommended.

Keywords::

• nanoparticles
• genotoxicity
• cytotoxicity
• cellular structure
• transmission electron microscopy
• lipid droplets
• vacuoles

Acknowledgements

The authors would like to thank Dr. Viviana Lopes for her critical input, Dr. Bertrand Faure (Department of Materials and Environmental Chemistry, Stockholm University, Sweden) for assistance with the Zetasizer and Catherine McGuinnes, ELEGI, QMRI, for the cell-free dichlorofluorescein assay protocol. Funding information: This work was supported by grants from the Swedish Research Council, Carl Trygger Foundation, VINNOVA, Magnus Bergvalls Foundation, Oscar and Lilli Lamms Minne Foundation, Längmanska kulturfonden, Lars Hiertas Minne foundation, IKERBASQUE, Basque Foundation for science, CBR-SSF and Ångpanneförening Research foundation.