Toxicity of TiO₂, ZrO₂, Fe⁰, Fe₂O₃, and Mn₂O₃ nanoparticles to the yeast, Saccharomyces cerevisiae.

The growing application of engineered nanomaterials is leading to an increased occurrence of nanoparticles (NPs) in the environment. Thus, there is a need to better understand their potential impact on the environment. This study evaluated the toxicity of nanosized TiO₂, ZrO₂, Fe(0), Fe₂O₃, and Mn₂O₃ towards the yeast Saccharomyces cerevisiae based on O₂ consumption and cell membrane integrity. In addition, the state of dispersion of the nanoparticles in the bioassay medium was characterized. All the nanomaterials showed high tendency to aggregate in the bioassay medium. A non-toxic polyacrylate dispersant was used to improve the NP dispersion stability and test the influence of the aggregation state in their toxicity. Mn₂O₃ NPs showed the highest inhibition of O₂ consumption (50% at 170 mg L(-1)) and cell membrane damage (approximately 30% of cells with compromised membrane at 1000 mg L(-1)), while the other NPs caused low (Fe(0)) or no toxicity (TiO₂, ZrO₂, and Fe₂O₃) to the yeast. Dispersant supplementation decreased the inhibition caused by Mn₂O₃ NPs at low concentrations, which could indicate that dispersant association with the particles may have an impact on the interaction between the NPs and the cells.