Abstract
In order to investigate the effects of metallic nanoparticles (NPs) on the performance of in vitro bioassay, zinc oxide NP (ZnO NP), aluminum oxide NP (Al2O3 NP), bare silver NP (Ag NP), and Ag NP capped with citrate (Agcit NP) were evaluated with yeast (Saccharomyces cerevisiae Y190) two-hybrid system (YES assay), carrying Japanese medaka estrogen receptors (mERs) in the presence of 17β-estradiol (E2, 10−6 M), a reference chemical for estrogenic activity. The distribution of NPs in the yeast was also examined by field-emission transmission electron microscopy (FE-TEM). The results show that TEM analysis revealed that NPs were present inside the yeast and accumulated deep inside the cell organelles, suggesting that cell death was caused by NPs. However, despite no significant change of mortality, the E2 estrogenic activities in yeast exposed to ZnO NP and Al2O3 NP were dose-dependently reduced. For Ag NP and Agcit NP, such phenomenon observed in the exposure of ZnO NP and Al2O3 NP did not occur. From the observations, we found that ZnO NP and Al2O3 NP in the environmental media could result in underestimated estrogenicity of endocrine-disrupting compounds when evaluated by YES assay.
Highlights
In environmental monitoring, instrumental analyses using the chromatography technique is the best choice, but it is a laborious, expensive, and time-consuming method
We investigated the effects of metallic NPs on the performance of YES assay with a Japanese medaka estrogen receptor
Transmission Electron Microscopy (TEM) analysis revealed that zinc oxide NP (ZnO NP) were present inside the yeast cells as single or small aggregates of particles (Figure 3b) and accumulated deep inside the nucleus or protoplasm
Summary
Instrumental analyses using the chromatography technique is the best choice, but it is a laborious, expensive, and time-consuming method. In vitro bioassay is currently considered as screening tool in a tiered approach, but there is still uncertainty about the reliability in environmental monitoring, because the results of in vitro bioassay may be affected by unidentified factors in the field samples [1]. The cellular toxicity of metal-based NPs has attracted the attention of many researchers around the world. Several studies have reported that metal-based NPs’ treatment of non-lethal levels induce the adverse effects, such as mitochondrial dysfunction, membrane damage, intracellular oxidative stress, and abnormal cell morphologies [5,6,7,8,9,10,11,12], which alter specific functions of the cell
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