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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

Dissolution curve of Zn2+ from different concentrations of nano ZnO (A) and bulk ZnO (B) in deionized water as a function of time.The data were presented as the mean ± SD from three replications (n = 3).
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f1: Dissolution curve of Zn2+ from different concentrations of nano ZnO (A) and bulk ZnO (B) in deionized water as a function of time.The data were presented as the mean ± SD from three replications (n = 3).

Mentions: As shown in Fig. 1, the Zn2+ release curves for nano and bulk ZnO were very close at the 1 and 10 mg/L concentrations, although more Zn2+ was released from nano ZnO than bulk ZnO at the highest concentration (100 mg/L). At the 1 mg/L concentration, nano ZnO dissolved rapidly and completely. This finding was confirmed by the Noyes-Whitney equation24. In contrast, less than 10% of the nano and bulk ZnO were dissolved at the primary concentrations of 10 and 100 mg/L, which was consistent with previous reports910. Both nano and bulk ZnO illustrated stronger toxic effects in the set of yeasts than the zinc salt (ZnSO4·7 H2O) (see Fig. S2 or Table 1). Thus, the Zn2+ released from either the ZnO NPs or bulk ZnO was not sufficient to elicit serious toxicity. Even when a high concentration of Zn2+ was employed (101,290.00 mg/L), a less than 10% decrease in cell viability was detected in the quadruple mutant (4Δ). The more than two log unit higher toxicity of the nano and bulk ZnO strongly indicated that the mechanism underlying the toxicity in yeast was essentially dependent on the particles themselves and not on the released zinc ions. However, we evaluated the extent to which the toxic effect was attributable to the dissolved zinc ions using previously described methods14. As shown in Fig. S3, the calculated concentrations of nano and bulk ZnO led to an almost 50% decrease in cell viability, with EC50 ranges from 44.16 to 57.35%. This result indicated that the cell viability testing was valid. Moreover, Zn2+ released from either nano ZnO or bulk ZnO yielded less than 9% cell death (range 3.16 to 8.25%, see Fig. S3). Correspondingly, the contributions of Zn2+ to the overall toxic effect accounted for less than 8% (range 2.93 to 7.44%; see Table 2). Zn2+ sometimes did not induce toxic effects in the yeast or mutants, resulting in the larger error bars in Fig. S3. Moreover, the investigation of intercellular ROS demonstrated that dissolved Zn2+ did not induce significant oxidative stress in the yeast (p > 0.05) compared to the ZnO particles (see Fig. 2). Because the solubilities of metals and metal oxides vary and most metal ions induce diverse toxic effects in organisms, the concentrations of metal ions released from NPs should be routinely measured and provided in the ecotoxicological and environmental assessments.


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

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

Dissolution curve of Zn2+ from different concentrations of nano ZnO (A) and bulk ZnO (B) in deionized water as a function of time.The data were presented as the mean ± SD from three replications (n = 3).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Dissolution curve of Zn2+ from different concentrations of nano ZnO (A) and bulk ZnO (B) in deionized water as a function of time.The data were presented as the mean ± SD from three replications (n = 3).
Mentions: As shown in Fig. 1, the Zn2+ release curves for nano and bulk ZnO were very close at the 1 and 10 mg/L concentrations, although more Zn2+ was released from nano ZnO than bulk ZnO at the highest concentration (100 mg/L). At the 1 mg/L concentration, nano ZnO dissolved rapidly and completely. This finding was confirmed by the Noyes-Whitney equation24. In contrast, less than 10% of the nano and bulk ZnO were dissolved at the primary concentrations of 10 and 100 mg/L, which was consistent with previous reports910. Both nano and bulk ZnO illustrated stronger toxic effects in the set of yeasts than the zinc salt (ZnSO4·7 H2O) (see Fig. S2 or Table 1). Thus, the Zn2+ released from either the ZnO NPs or bulk ZnO was not sufficient to elicit serious toxicity. Even when a high concentration of Zn2+ was employed (101,290.00 mg/L), a less than 10% decrease in cell viability was detected in the quadruple mutant (4Δ). The more than two log unit higher toxicity of the nano and bulk ZnO strongly indicated that the mechanism underlying the toxicity in yeast was essentially dependent on the particles themselves and not on the released zinc ions. However, we evaluated the extent to which the toxic effect was attributable to the dissolved zinc ions using previously described methods14. As shown in Fig. S3, the calculated concentrations of nano and bulk ZnO led to an almost 50% decrease in cell viability, with EC50 ranges from 44.16 to 57.35%. This result indicated that the cell viability testing was valid. Moreover, Zn2+ released from either nano ZnO or bulk ZnO yielded less than 9% cell death (range 3.16 to 8.25%, see Fig. S3). Correspondingly, the contributions of Zn2+ to the overall toxic effect accounted for less than 8% (range 2.93 to 7.44%; see Table 2). Zn2+ sometimes did not induce toxic effects in the yeast or mutants, resulting in the larger error bars in Fig. S3. Moreover, the investigation of intercellular ROS demonstrated that dissolved Zn2+ did not induce significant oxidative stress in the yeast (p > 0.05) compared to the ZnO particles (see Fig. 2). Because the solubilities of metals and metal oxides vary and most metal ions induce diverse toxic effects in organisms, the concentrations of metal ions released from NPs should be routinely measured and provided in the ecotoxicological and environmental assessments.

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