Merging nano-genotoxicology with eco-genotoxicology: An integrated approach to determine interactive genotoxic and sub-lethal toxic effects of C60 fullerenes and fluoranthene in marine mussels, Mytilus sp.

Abstract

Whilst there is growing concern over the potential detrimental impact of engineered nanoparticles (ENPs) on the natural environment, little is known about their interactions with other contaminants. In the present study, marine mussels (Mytilus sp.) were exposed for 3 days to C60 fullerenes (C60; 0.10–1mgl−1) and a model polycyclic aromatic hydrocarbon (PAH), fluoranthene (32–100μgl−1), either alone or in combination. The first two experiments were conducted by exposing the organisms to different concentrations of C60 and fluoranthene alone, in order to determine the effects on total glutathione levels (as a measure of generic oxidative stress), genotoxicity (DNA strand breaks using Comet assay in haemocytes), DNA adduct analyses (using 32P-postlabelling method) in different organs, histopathological changes in different tissues (i.e. adductor muscle, digestive gland and gills) and physiological effects (feeding or clearance rate). Subsequently, in the third experiment, a combined exposure of C60 plus fluoranthene (0.10mgl−1 and 32μgl−1, respectively) was carried out to evaluate all endpoints mentioned above. Both fluoranthene and C60 on their own caused concentration-dependent increases in DNA strand breaks as determined by the Comet assay. Formation of DNA adducts however could not be detected for any exposure conditions. Combined exposure to C60 and fluoranthene additively enhanced the levels of DNA strand breaks along with a 2-fold increase in the total glutathione content. In addition, significant accumulation of C60 was observed in all organs, with highest levels in digestive gland (24.90±4.91μgC60g−1ww). Interestingly, clear signs of abnormalities in adductor muscle, digestive gland and gills were observed by histopathology. Clearance rates indicated significant differences compared to the control with exposure to C60, and C60/fluoranthene combined treatments, but not after fluoranthene exposure alone. This study demonstrated that at the selected concentrations, both C60 and fluoranthene evoke toxic responses and genetic damage. The combined exposure produced enhanced damage with additive rather than synergistic effects.