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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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Relative changes of the cell-specific growth rate (µ) in the treatments with different free Ag+ concentrations ([Ag+]F, M) to that in the control in the experiment (a) where different concentrations of Ag-ENs (27.8, 92.7, 139.1, 185.4, and 278.1 µM; triangle symbol) and Ag+ (55.4, 74.2, 81.9, 83.4, and 92.7 µM; circle symbol) were added and (b) where different concentrations of GSH (triangle - 83.3 µM, circle - 249.8 µM, diamond - 416.3 µM) were applied for the four different Ag-EN concentration treatments (0, 139.1, 185.4, and 278.1 µM), respectively.Data are mean ± standard deviation (n = 3).
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pone-0015196-g004: Relative changes of the cell-specific growth rate (µ) in the treatments with different free Ag+ concentrations ([Ag+]F, M) to that in the control in the experiment (a) where different concentrations of Ag-ENs (27.8, 92.7, 139.1, 185.4, and 278.1 µM; triangle symbol) and Ag+ (55.4, 74.2, 81.9, 83.4, and 92.7 µM; circle symbol) were added and (b) where different concentrations of GSH (triangle - 83.3 µM, circle - 249.8 µM, diamond - 416.3 µM) were applied for the four different Ag-EN concentration treatments (0, 139.1, 185.4, and 278.1 µM), respectively.Data are mean ± standard deviation (n = 3).

Mentions: In the experiment, where the toxicity of Ag-ENs and Ag+ was compared, [Ag+]T in the <1 nm fraction of each treatment was quantified and [Ag+]F was then calculated. The free Ag+ concentrations were 0.088, 0.57, 1.34, 1.89, 1.31 pM for the five Ag-EN addition treatments (with nanoparticle concentrations from low to high), and 1.13 pM, 6.87 pM, 10.8 nM, 50.1 nM, 93.7 nM for the five Ag+ addition treatments. In order to see whether the potential toxicity of Ag-ENs could be well explained by the Ag+ they released, the toxicity results were presented as the change of [Ag+]F (Fig. 4a). If similar inhibitive effects were observed at the same [Ag+]F for both the Ag-EN and Ag+ addition treatments, then it can be concluded that the toxicity of Ag-ENs was caused by the Ag+ released. Significant toxicity (p<0.05) to the freshwater alga O. danica was observed in the higher Ag-EN concentration treatments. Cell growth was inhibited by 18.8%, 40.3%, and 100% when Ag-EN concentration was 139.1, 185.4, and 278.1 µM, respectively, while their [Ag+]F was kept relatively constant (1.31–1.89 pM). In contrast, no significant toxicity (p>0.05) was observed in the Ag+ addition treatments until [Ag+]F was higher than 10.8 nM. The cell growth was inhibited by 51.1% and 100% when [Ag+]F was 50.1 and 93.7 nM, respectively. Therefore, the Ag-EN addition treatments appears to be more toxic than that of the Ag+ addition treatments based on their [Ag+]F. Accordingly, the calculated [Ag+]F based EC50 was much lower for the Ag-EN addition treatments than that for the Ag+ addition treatments (1.27 pM vs. 49.1 nM). The Ag+ toxicity to freshwater algae has been examined in several studies, with the EC50 observed ranging from 12 to 930 nM, which are consistent with what was obtained in the present study [30], [31].


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)

Relative changes of the cell-specific growth rate (µ) in the treatments with different free Ag+ concentrations ([Ag+]F, M) to that in the control in the experiment (a) where different concentrations of Ag-ENs (27.8, 92.7, 139.1, 185.4, and 278.1 µM; triangle symbol) and Ag+ (55.4, 74.2, 81.9, 83.4, and 92.7 µM; circle symbol) were added and (b) where different concentrations of GSH (triangle - 83.3 µM, circle - 249.8 µM, diamond - 416.3 µM) were applied for the four different Ag-EN concentration treatments (0, 139.1, 185.4, and 278.1 µM), respectively.Data are mean ± standard deviation (n = 3).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0015196-g004: Relative changes of the cell-specific growth rate (µ) in the treatments with different free Ag+ concentrations ([Ag+]F, M) to that in the control in the experiment (a) where different concentrations of Ag-ENs (27.8, 92.7, 139.1, 185.4, and 278.1 µM; triangle symbol) and Ag+ (55.4, 74.2, 81.9, 83.4, and 92.7 µM; circle symbol) were added and (b) where different concentrations of GSH (triangle - 83.3 µM, circle - 249.8 µM, diamond - 416.3 µM) were applied for the four different Ag-EN concentration treatments (0, 139.1, 185.4, and 278.1 µM), respectively.Data are mean ± standard deviation (n = 3).
Mentions: In the experiment, where the toxicity of Ag-ENs and Ag+ was compared, [Ag+]T in the <1 nm fraction of each treatment was quantified and [Ag+]F was then calculated. The free Ag+ concentrations were 0.088, 0.57, 1.34, 1.89, 1.31 pM for the five Ag-EN addition treatments (with nanoparticle concentrations from low to high), and 1.13 pM, 6.87 pM, 10.8 nM, 50.1 nM, 93.7 nM for the five Ag+ addition treatments. In order to see whether the potential toxicity of Ag-ENs could be well explained by the Ag+ they released, the toxicity results were presented as the change of [Ag+]F (Fig. 4a). If similar inhibitive effects were observed at the same [Ag+]F for both the Ag-EN and Ag+ addition treatments, then it can be concluded that the toxicity of Ag-ENs was caused by the Ag+ released. Significant toxicity (p<0.05) to the freshwater alga O. danica was observed in the higher Ag-EN concentration treatments. Cell growth was inhibited by 18.8%, 40.3%, and 100% when Ag-EN concentration was 139.1, 185.4, and 278.1 µM, respectively, while their [Ag+]F was kept relatively constant (1.31–1.89 pM). In contrast, no significant toxicity (p>0.05) was observed in the Ag+ addition treatments until [Ag+]F was higher than 10.8 nM. The cell growth was inhibited by 51.1% and 100% when [Ag+]F was 50.1 and 93.7 nM, respectively. Therefore, the Ag-EN addition treatments appears to be more toxic than that of the Ag+ addition treatments based on their [Ag+]F. Accordingly, the calculated [Ag+]F based EC50 was much lower for the Ag-EN addition treatments than that for the Ag+ addition treatments (1.27 pM vs. 49.1 nM). The Ag+ toxicity to freshwater algae has been examined in several studies, with the EC50 observed ranging from 12 to 930 nM, which are consistent with what was obtained in the present study [30], [31].

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