The algal toxicity of silver engineered nanoparticles and detoxification by exopolymeric substances
2009
Miao, Ai-Jun | Schwehr, Kathy A. | Xu, Chen | Zhang, Sai-Jin | Luo, Zhiping | Quigg, Antonietta | Santschi, Peter H.
In this study, we report that silver ions (Ag+) from the oxidative dissolution of silver engineered nanoparticles (Ag-ENs) determined the EN toxicity to the marine diatom Thalassiosira weissflogii. Most of the Ag-ENs formed non-toxic aggregates (>0.22 μm) in seawater. When the free Ag+ concentration ([Ag+]F) was greatly reduced by diafiltration or thiol complexation, no toxicity was observed, even though the Ag-ENs were better dispersed in the presence of thiols with up to 1.08 x 10⁻⁵ M Ag-ENs found in the <0.22 μm fraction, which are orders of magnitude higher than predicted for the natural aquatic environment. The secretion of polysaccharide-rich algal exopolymeric substances (EPS) significantly increased at increasing [Ag+]F. Both dissolved and particulate polysaccharide concentrations were higher for nutrient-limited cells, coinciding with their higher Ag+ tolerance, suggesting that EPS may be involved in Ag+ detoxification. Ag-ENs were found to only have indirect toxic effects on marine phytoplankton as a result of their rapid Ag+ release.
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