Combined Effects of Titanium Dioxide Nanoparticles (TiO2NPs) and Benzo(a)pyrene (B(a)P) on Hemocyte Cells and NADPH Cytochrome C Reductase Activity in Blue Mussels (Mytilus edulis)
MetadataShow full item record
- Institutt for biologi 
Nanotechnology is currently one of the fastest growing industries. Titanium dioxide nanoparticles (TiO2NPs) are estimated to be one of the main produced engineered nanoparticles (ENPs) in the world today, and production is expected to increase. This might lead to enhanced emissions of ENPs to the environment. ENPs can be toxic to organisms. In addition, ENPs are seen to interact with pollutants and are thus assumed to alter the uptake of pollutants into organisms. Soil and sediments are suggested to be the main sink for ENPs together with other pollutants like polycyclic aromatic hydrocarbons (PAHs). As a consequence, benthic organisms are vulnerable to toxic effects of ENPs and for increased uptake of other pollutants by facilitated transportation of ENPs into the organisms. In the present study, blue mussels (Mytilus edulis) were exposed to titanium dioxide nanoparticles (TiO2NPs) (0.2 mg/L and 2.0 mg/L) and benzo(a)pyrene (B(a)P) (20 µg/L) singly and in combination with each other, for 96 hours. Cell damage on hemocytes and effects on the NADPH cytochrome c reductase activity in the digestive gland were examined with micronucleus assay, and by investigating the NADPH cytochrome c reductase activity with a spectrophotometric method. Protein concentrations in the mussels were determined by the Bradford method for normalizing the NADPH cytochrome c reductase activity. In this study, both B(a)P and TiO2NP increased the micronucleus (MN) frequency in hemocyte cells, both alone and in combination. A slight increase in MN frequency were detected from B(a)P exposed mussels to TiO2NP exposed mussels, and B(a)P+TiO2NP showed to have highest genotoxic effect in hemocyte cells. This suggests that both compounds have damaged the cell nucleus. No effects were detected for NADPH cytochrome c reductase activity normalized with the protein concentrations. However, protein concentrations increased from B(a)P exposed mussels to B(a)P+TiO2NP exposed mussels and the same was found for NADPH cytochrome c reductase activity without normalization for protein concentration. The findings of this study showed that TiO2NPs have genotoxic effects on mussel hemocytes, and that the toxic effect of a combined exposure of B(a)P and TiO2NP was higher than the effects of the single components. TiO2NP did not have toxic effects on the NADPH cytochrome c reductase activity. However, in combination with B(a)P, TiO2NP might adsorb B(a)P and transport the contaminant into mussels, and released B(a)P, which can have increased the NADPH cytochrome c reductase activity in the digestive gland of mussels. Further research is needed for a better understanding of TiO2NP toxicity on aquatic organisms, especially to elucidate interactions between ENPs and pollutants.