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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

The transmission electron microscope (a) and Z-contrast dark-field scanning transmission electron microscope (b) images of a single Ochromonas danica cell in the Ag-EN addition (92.7 µM) treatment.Arrows indicates the locations of Ag-ENs inside the cells, which was further confirmed by energy dispersive X-ray spectrum. The letter ‘P’ represents the plasma membrane of the cell, ‘V’ means vacuole and ‘C’ is chloroplast.
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pone-0015196-g005: The transmission electron microscope (a) and Z-contrast dark-field scanning transmission electron microscope (b) images of a single Ochromonas danica cell in the Ag-EN addition (92.7 µM) treatment.Arrows indicates the locations of Ag-ENs inside the cells, which was further confirmed by energy dispersive X-ray spectrum. The letter ‘P’ represents the plasma membrane of the cell, ‘V’ means vacuole and ‘C’ is chloroplast.

Mentions: In order to further find out whether there is any direct internalization of Ag-ENs into the cells, the alga in the control treatment as well as those from Ag-EN or Ag+ addition treatments were examined under the TEM and STEM. A noticeable amount of Ag-ENs was found in the vacuoles of O. danica, which was not observed in the control and Ag+ addition treatments (Fig. 5 and Fig. S3). The existence of Ag-ENs inside the vacuoles was further confirmed by the elemental composition profile obtained from an energy dispersive X-ray spectrometer shown in Fig. S4. The irregular shape of the vacuoles is possibly because of the distortion when preparing the samples for TEM analysis. There were no obvious toxic effects in all the treatments chosen for TEM analysis, excluding the possibility that it was an increase of cell membrane permeability or a break in the membrane that resulted in the passive uptake of Ag-ENs into the cells. Therefore, Ag-EN internalization into the cells was found in the present study to be an important mechanism through which algal growth was substantially reduced, especially in cells with endocytosis ability. However, it remains unclear whether Ag-ENs inside the cells can directly inhibit the algal growth or indirectly by the release of Ag+ internally.


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)

The transmission electron microscope (a) and Z-contrast dark-field scanning transmission electron microscope (b) images of a single Ochromonas danica cell in the Ag-EN addition (92.7 µM) treatment.Arrows indicates the locations of Ag-ENs inside the cells, which was further confirmed by energy dispersive X-ray spectrum. The letter ‘P’ represents the plasma membrane of the cell, ‘V’ means vacuole and ‘C’ is chloroplast.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0015196-g005: The transmission electron microscope (a) and Z-contrast dark-field scanning transmission electron microscope (b) images of a single Ochromonas danica cell in the Ag-EN addition (92.7 µM) treatment.Arrows indicates the locations of Ag-ENs inside the cells, which was further confirmed by energy dispersive X-ray spectrum. The letter ‘P’ represents the plasma membrane of the cell, ‘V’ means vacuole and ‘C’ is chloroplast.
Mentions: In order to further find out whether there is any direct internalization of Ag-ENs into the cells, the alga in the control treatment as well as those from Ag-EN or Ag+ addition treatments were examined under the TEM and STEM. A noticeable amount of Ag-ENs was found in the vacuoles of O. danica, which was not observed in the control and Ag+ addition treatments (Fig. 5 and Fig. S3). The existence of Ag-ENs inside the vacuoles was further confirmed by the elemental composition profile obtained from an energy dispersive X-ray spectrometer shown in Fig. S4. The irregular shape of the vacuoles is possibly because of the distortion when preparing the samples for TEM analysis. There were no obvious toxic effects in all the treatments chosen for TEM analysis, excluding the possibility that it was an increase of cell membrane permeability or a break in the membrane that resulted in the passive uptake of Ag-ENs into the cells. Therefore, Ag-EN internalization into the cells was found in the present study to be an important mechanism through which algal growth was substantially reduced, especially in cells with endocytosis ability. However, it remains unclear whether Ag-ENs inside the cells can directly inhibit the algal growth or indirectly by the release of Ag+ internally.

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