Cellular toxicity and bioaccumulationof silver nanoparticles in the marine polychaete, Nereis diversicolor

In this study, the toxicities of commercial silver nanoparticles (Ag NPs, 20 and 80 nm) were compared with the toxicities of Ag+ ions in the marine sediment-dwelling polychaete, Nereis diversicolor, after 10 d of sediment exposure, using lysosomal membrane stability (neutral red assay), DNA damage (comet assay) and bioaccumulation as endpoints. Prior to the toxicity experiment, the physical-chemical properties of Ag NPs were fully characterized. The nominal concentrations used in all exposure scenarios were 0, 5, 10, 25, 50 and 100 µg Ag/g dry weight (dw) sediment. Lysosomal membrane stability of Nereis coelomocytes, which was measured by neutral red retention time (NRRT), decreased in a concentration-dependent manner in all Ag treatments, indicating increased permeability of lysosomal membranes. Comet assay results showed that Ag was able to cause DNA damage in Nereis coelomocytes regardless of the form added, and that this effect was also concentration-related. Ag NPs had marginally higher cytotoxicity and genotoxicity than Ag+ ions, but there was no significant difference between the two Ag NP treatments. N. diversicolor did accumulate sediment-associated Ag from all Ag treatments. The highest Ag body burdens were 6.79±6.47, 16.94±22.36 and 7.78±13.73 µg/g dw for worms in ionic, 20 nm and 80 nm Ag-treatments, respectively, but there was no significant difference in Ag bioaccumulation among the three treatments. The size of worms (expressed as dry weight) had a significant effect on bioaccumulation, indicating possibly different uptake or excretion abilities of different sizes of worms; smaller worms accumulated more Ag than larger ones.