Nanoparticles (NPs) have broad applications in medicine, cosmetics, optics, catalysis, environmental purification, and other areas nowadays. With increasing annual production of NPs, the risks of their harmful influence on the environment and human health are also increasing. Currently, our knowledge about the mechanisms of the interaction between NPs and living organisms is limited. The marine species and their habitat environment are under continuous stress owing to the anthropogenic activities, which result in the release of NPs in the aquatic environment. We used a bioassay model with hemocytes of three bivalve mollusc species, namely, Crenomytilus grayanus, Modiolus modiolus, and Arca boucardi, to evaluate the toxicity of 10 different types of NPs. Specifically, we compared the cytotoxic effects and cell-membrane polarization changes in the hemocytes exposed to carbon nanotubes, carbon nanofibers, silicon nanotubes, cadmium and zinc sulfides, Au-NPs, and TiO2 NPs. Viability and the changes in hemocyte membrane polarization were measured by the flow cytometry method. The highest aquatic toxicity was registered for metal-based NPs, which caused cytotoxicity to the hemocytes of all the studied bivalve species. Our results also highlighted different sensitivities of the used tested mollusc species to specific NPs.
The marine bivalves, mussels Crenomytilus grayanus (Dunker, 1853) and scallops Swiftopecten swifti (Bernardi, 1858), were in vivo exposed to 12-14 nm multi-walled carbon nanotubes (MWNTs) for up to 48 h. Microscopic analysis in combination with the RAMAN spectrophotometry revealed the MWNT aggregates on the gills surface and inside the gut of all exposed individuals. After 48 h exposure, there were no changes in the total cell count, the average cell size and granularity in the hemolymph of mussels, while in the scallops the total hemocyte count was significantly reduced, and the average hemocyte granularity increased. Biochemical markers of oxidative stress (activity of glutathione-S-transferase and catalase, concentration of reduced glutathione, and the degree of lipid peroxidation) did not change significantly in the digestive gland of both mussels and scallops. In hemolymph, catalase activity increased as compared to control in both mussels and scallops. Moreover, concentration of reduced glutathione increased in hemolymph of scallops on the second day of exposure to MWNTs. The data obtained indicate that MWNTs may affect different bivalve mollusks more or less strongly under the same exposure conditions.
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