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The neglected nano-specific toxicity of ZnO nanoparticles in the yeast Saccharomyces cerevisiae.

Zhang W, Bao S, Fang T - Sci Rep (2016)

Bottom Line: The toxic effects in the yeast were slightly attributable to dissolved zinc ions from the ZnO (nano or bulk) particles.Oxidative damage and mechanical damage contributed to the toxic effect of the ZnO particles.The mechanism of mechanical damage is proposed to be an inherent characteristic underlying the nano-specific toxicity in the mutants.

View Article: PubMed Central - PubMed

Affiliation: Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.

ABSTRACT
Nanoparticles (NPs) with unique physicochemical properties induce nano-specific (excess) toxicity in organisms compared with their bulk counterparts. Evaluation and consideration of nano-specific toxicity are meaningful for the safe design and environmental risk assessment of NPs. However, ZnO NPs have been reported to lack excess toxicity for diverse organisms. In the present study, the nano-specific toxicity of ZnO NPs was evaluated in the yeast Saccharomyces cerevisiae. Nano-specific toxicity of ZnO NPs was not observed in the wild type yeast. However, the ZnO NPs induced very similar nano-specific toxicities in the three mutants with comparable log Te ((particle)) values (0.64 vs 0.65 vs 0.62), suggesting that the mutants were more sensitive and specific for the NPs' nano-specific toxicity. The toxic effects in the yeast were slightly attributable to dissolved zinc ions from the ZnO (nano or bulk) particles. Oxidative damage and mechanical damage contributed to the toxic effect of the ZnO particles. The mechanism of mechanical damage is proposed to be an inherent characteristic underlying the nano-specific toxicity in the mutants. The log Te ((particle)) was a useful parameter for evaluation of NPs nano-specific toxicity, whereas log Te ((ion)) efficiently determined the NPs toxicity associated with released ions.

No MeSH data available.


Related in: MedlinePlus

Cell membrane permeability caused by the 1, 5 and 10 mg/L concentrations of nano ZnO and bulk ZnO. H2O2 served as the positive control.(A) BY4741; (B) yap1Δ; (C) 4Δ; (D) 5Δ. Asterisks (* and **) denote significant and extremely significant differences compared to the control group (p < 0.05 and p < 0.01), respectively. The data were presented as the mean ± SD from six replications (n = 6).
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f4: Cell membrane permeability caused by the 1, 5 and 10 mg/L concentrations of nano ZnO and bulk ZnO. H2O2 served as the positive control.(A) BY4741; (B) yap1Δ; (C) 4Δ; (D) 5Δ. Asterisks (* and **) denote significant and extremely significant differences compared to the control group (p < 0.05 and p < 0.01), respectively. The data were presented as the mean ± SD from six replications (n = 6).

Mentions: Undoubtedly, the mechanical damages caused by particles binding to the cell surface are majorly governed by electrostatic forces, and hence the zeta potentials of the particles and yeast strains were measured (see Table S1). All yeast strains showed the expected negative charge, and all of their negative charges were slightly decreased at the 6 h time point. Interestingly, the ZnO NPs possessed a positive charge that was absolutely different from the negative charge of the bulk ZnO. The yeast strains preferred to bind to the ZnO NPs but not to the bulk ZnO. Theoretically, more serious cell wall and/or membrane damage would emerge under ZnO NPs exposure compared to bulk ZnO. Indeed, this finding was confirmed by the PI dye experiment shown in Fig. 4, in which ZnO NPs at concentrations of 5 and 10 mg/L induced stronger cell permeability in yap1Δ, 4Δ and 5Δ compared to bulk ZnO (p < 0.5). Interestingly, no significant difference in cell permeability was detected between the nano and bulk ZnO in the wild type strain (p > 0.5, see Fig. 4A). One possible explanation was that the mechanical disturbance under the shaking condition (200 rpm) overcame the electrostatic forces and contacts that existed between the bulk ZnO and the cell wall.


The neglected nano-specific toxicity of ZnO nanoparticles in the yeast Saccharomyces cerevisiae.

Zhang W, Bao S, Fang T - Sci Rep (2016)

Cell membrane permeability caused by the 1, 5 and 10 mg/L concentrations of nano ZnO and bulk ZnO. H2O2 served as the positive control.(A) BY4741; (B) yap1Δ; (C) 4Δ; (D) 5Δ. Asterisks (* and **) denote significant and extremely significant differences compared to the control group (p < 0.05 and p < 0.01), respectively. The data were presented as the mean ± SD from six replications (n = 6).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837412&req=5

f4: Cell membrane permeability caused by the 1, 5 and 10 mg/L concentrations of nano ZnO and bulk ZnO. H2O2 served as the positive control.(A) BY4741; (B) yap1Δ; (C) 4Δ; (D) 5Δ. Asterisks (* and **) denote significant and extremely significant differences compared to the control group (p < 0.05 and p < 0.01), respectively. The data were presented as the mean ± SD from six replications (n = 6).
Mentions: Undoubtedly, the mechanical damages caused by particles binding to the cell surface are majorly governed by electrostatic forces, and hence the zeta potentials of the particles and yeast strains were measured (see Table S1). All yeast strains showed the expected negative charge, and all of their negative charges were slightly decreased at the 6 h time point. Interestingly, the ZnO NPs possessed a positive charge that was absolutely different from the negative charge of the bulk ZnO. The yeast strains preferred to bind to the ZnO NPs but not to the bulk ZnO. Theoretically, more serious cell wall and/or membrane damage would emerge under ZnO NPs exposure compared to bulk ZnO. Indeed, this finding was confirmed by the PI dye experiment shown in Fig. 4, in which ZnO NPs at concentrations of 5 and 10 mg/L induced stronger cell permeability in yap1Δ, 4Δ and 5Δ compared to bulk ZnO (p < 0.5). Interestingly, no significant difference in cell permeability was detected between the nano and bulk ZnO in the wild type strain (p > 0.5, see Fig. 4A). One possible explanation was that the mechanical disturbance under the shaking condition (200 rpm) overcame the electrostatic forces and contacts that existed between the bulk ZnO and the cell wall.

Bottom Line: The toxic effects in the yeast were slightly attributable to dissolved zinc ions from the ZnO (nano or bulk) particles.Oxidative damage and mechanical damage contributed to the toxic effect of the ZnO particles.The mechanism of mechanical damage is proposed to be an inherent characteristic underlying the nano-specific toxicity in the mutants.

View Article: PubMed Central - PubMed

Affiliation: Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.

ABSTRACT
Nanoparticles (NPs) with unique physicochemical properties induce nano-specific (excess) toxicity in organisms compared with their bulk counterparts. Evaluation and consideration of nano-specific toxicity are meaningful for the safe design and environmental risk assessment of NPs. However, ZnO NPs have been reported to lack excess toxicity for diverse organisms. In the present study, the nano-specific toxicity of ZnO NPs was evaluated in the yeast Saccharomyces cerevisiae. Nano-specific toxicity of ZnO NPs was not observed in the wild type yeast. However, the ZnO NPs induced very similar nano-specific toxicities in the three mutants with comparable log Te ((particle)) values (0.64 vs 0.65 vs 0.62), suggesting that the mutants were more sensitive and specific for the NPs' nano-specific toxicity. The toxic effects in the yeast were slightly attributable to dissolved zinc ions from the ZnO (nano or bulk) particles. Oxidative damage and mechanical damage contributed to the toxic effect of the ZnO particles. The mechanism of mechanical damage is proposed to be an inherent characteristic underlying the nano-specific toxicity in the mutants. The log Te ((particle)) was a useful parameter for evaluation of NPs nano-specific toxicity, whereas log Te ((ion)) efficiently determined the NPs toxicity associated with released ions.

No MeSH data available.


Related in: MedlinePlus