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Intracellular uptake: a possible mechanism for silver engineered nanoparticle toxicity to a freshwater alga Ochromonas danica.

Miao AJ, Luo Z, Chen CS, Chin WC, Santschi PH, Quigg A - PLoS ONE (2010)

Bottom Line: Despite their good dispersability, the Ag-ENs were found to continuously aggregate and dissolve rapidly.Such inhibitive effects were mitigated when more glutathione was added, but could never be completely eliminated.Most importantly, we demonstrate, for the first time, that Ag-ENs can be taken in and accumulated inside the algal cells, where they exerted their toxic effects.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing, Jiangsu Province, People's Republic of China. miaoaj@nju.edu.cn

ABSTRACT
The behavior and toxicity of silver engineered nanoparticles (Ag-ENs) to the mixotrophic freshwater alga Ochromonas danica were examined in the present study to determine whether any other mechanisms are involved in their algal toxicity besides Ag(+) liberation outside the cells. Despite their good dispersability, the Ag-ENs were found to continuously aggregate and dissolve rapidly. When the initial nanoparticle concentration was lower than 10 µM, the total dissolved Ag(+) concentration ([Ag(+)](T)) in the suspending media reached its maximum after 1 d and then decreased suggesting that Ag(+) release might be limited by the nanoparticle surface area under these conditions. Furthermore, Ag-EN dissolution extent remarkably increased in the presence of glutathione. In the Ag-EN toxicity experiment, glutathione was also used to eliminate the indirect effects of Ag(+) that was released. However, remarkable toxicity was still observed although the free Ag(+) concentration in the media was orders of magnitude lower than the non-observed effect concentration of Ag(+) itself. Such inhibitive effects were mitigated when more glutathione was added, but could never be completely eliminated. Most importantly, we demonstrate, for the first time, that Ag-ENs can be taken in and accumulated inside the algal cells, where they exerted their toxic effects. Therefore, nanoparticle internalization may be an alternative pathway through which algal growth can be influenced.

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Related in: MedlinePlus

Normalized size distribution (to the initial Ag-EN concentration) of 1.85, 9.27, 27.8, and 92.7 µM Ag-ENs in different size fractions (> 200 nm, 35–200 nm, 1–35 nm, <1 nm) during a 7 d period in the modified DY-V medium.Data are mean ± standard deviation (n = 3).
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pone-0015196-g002: Normalized size distribution (to the initial Ag-EN concentration) of 1.85, 9.27, 27.8, and 92.7 µM Ag-ENs in different size fractions (> 200 nm, 35–200 nm, 1–35 nm, <1 nm) during a 7 d period in the modified DY-V medium.Data are mean ± standard deviation (n = 3).

Mentions: Similar to the 20 d experiment, the normalized Ag-EN distribution in the >200 nm fraction increased while less Ag-ENs were left in the 1–35 nm fraction with time for the different nanoparticle concentration treatments (Fig. 2). However, the Ag-EN distribution in the 35–200 nm fraction was kept constant during the 7 d period as compared with that in the 20 d experiment suggesting that a considerable change in nanoparticle distribution into this fraction may only be observed after 7 d. Ag distribution in 35 nm–200 nm fraction was obtained by subtracting the Ag concentration in the <35 nm fraction from that in the <200 nm filtrate. Therefore, the negative amount of Ag observed in the 35–200 nm fraction doesn't really mean there are negative amounts of Ag in these fractions but indicates the amount of Ag distributed in these fractions could be neglected, as they are within the error of the determination [19]. Although the Ag-EN distribution in the <1 nm (10 kD) fraction remained unchanged with time in the two highest nanoparticle concentration treatments (27.8 and 92.7 µM), [Ag+]T increased from 0.25 and 0.77 µM at the beginning to 0.37 and 0.92 µM on day 1 and then decreased continuously to 0.21 and 0.43 µM at the end of the experiment when the initial Ag-EN concentration was 1.85 and 9.27 µM, respectively.


Intracellular uptake: a possible mechanism for silver engineered nanoparticle toxicity to a freshwater alga Ochromonas danica.

Miao AJ, Luo Z, Chen CS, Chin WC, Santschi PH, Quigg A - PLoS ONE (2010)

Normalized size distribution (to the initial Ag-EN concentration) of 1.85, 9.27, 27.8, and 92.7 µM Ag-ENs in different size fractions (> 200 nm, 35–200 nm, 1–35 nm, <1 nm) during a 7 d period in the modified DY-V medium.Data are mean ± standard deviation (n = 3).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3008680&req=5

pone-0015196-g002: Normalized size distribution (to the initial Ag-EN concentration) of 1.85, 9.27, 27.8, and 92.7 µM Ag-ENs in different size fractions (> 200 nm, 35–200 nm, 1–35 nm, <1 nm) during a 7 d period in the modified DY-V medium.Data are mean ± standard deviation (n = 3).
Mentions: Similar to the 20 d experiment, the normalized Ag-EN distribution in the >200 nm fraction increased while less Ag-ENs were left in the 1–35 nm fraction with time for the different nanoparticle concentration treatments (Fig. 2). However, the Ag-EN distribution in the 35–200 nm fraction was kept constant during the 7 d period as compared with that in the 20 d experiment suggesting that a considerable change in nanoparticle distribution into this fraction may only be observed after 7 d. Ag distribution in 35 nm–200 nm fraction was obtained by subtracting the Ag concentration in the <35 nm fraction from that in the <200 nm filtrate. Therefore, the negative amount of Ag observed in the 35–200 nm fraction doesn't really mean there are negative amounts of Ag in these fractions but indicates the amount of Ag distributed in these fractions could be neglected, as they are within the error of the determination [19]. Although the Ag-EN distribution in the <1 nm (10 kD) fraction remained unchanged with time in the two highest nanoparticle concentration treatments (27.8 and 92.7 µM), [Ag+]T increased from 0.25 and 0.77 µM at the beginning to 0.37 and 0.92 µM on day 1 and then decreased continuously to 0.21 and 0.43 µM at the end of the experiment when the initial Ag-EN concentration was 1.85 and 9.27 µM, respectively.

Bottom Line: Despite their good dispersability, the Ag-ENs were found to continuously aggregate and dissolve rapidly.Such inhibitive effects were mitigated when more glutathione was added, but could never be completely eliminated.Most importantly, we demonstrate, for the first time, that Ag-ENs can be taken in and accumulated inside the algal cells, where they exerted their toxic effects.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing, Jiangsu Province, People's Republic of China. miaoaj@nju.edu.cn

ABSTRACT
The behavior and toxicity of silver engineered nanoparticles (Ag-ENs) to the mixotrophic freshwater alga Ochromonas danica were examined in the present study to determine whether any other mechanisms are involved in their algal toxicity besides Ag(+) liberation outside the cells. Despite their good dispersability, the Ag-ENs were found to continuously aggregate and dissolve rapidly. When the initial nanoparticle concentration was lower than 10 µM, the total dissolved Ag(+) concentration ([Ag(+)](T)) in the suspending media reached its maximum after 1 d and then decreased suggesting that Ag(+) release might be limited by the nanoparticle surface area under these conditions. Furthermore, Ag-EN dissolution extent remarkably increased in the presence of glutathione. In the Ag-EN toxicity experiment, glutathione was also used to eliminate the indirect effects of Ag(+) that was released. However, remarkable toxicity was still observed although the free Ag(+) concentration in the media was orders of magnitude lower than the non-observed effect concentration of Ag(+) itself. Such inhibitive effects were mitigated when more glutathione was added, but could never be completely eliminated. Most importantly, we demonstrate, for the first time, that Ag-ENs can be taken in and accumulated inside the algal cells, where they exerted their toxic effects. Therefore, nanoparticle internalization may be an alternative pathway through which algal growth can be influenced.

Show MeSH
Related in: MedlinePlus