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Multibiomarker assessment of cadmium-based quantum dots effects in the marine mussel Mytilus galloprovincialis

Publication . Rocha, Thiago Lopes; Bebianno, Maria João

Nanotechnology and use of engineered nanomaterials (ENMs) may improve life quality, economic growth and environmental quality, but their environmental risk in the marine environment is scarce. Properties of quantum dots (QDs), namely small size, unique optical and biofunctional properties, allow their use in nanomedicine, biology and electronics, but also confer different toxicity compared to its dissolved counterparts. Accordingly, this thesis assessed the toxicokinetics (TK), mode of action (MoA) and toxicity of CdTe QDs (10 μg Cd L-1) in the marine mussel Mytilus galloprovincialis, compared to dissolved Cd for 21 days followed by 50 days depuration. For this purpose, Cd distribution in different mussel tissues, subcellular fractions and biodeposits were analysed, TK parameters estimated (accumulation and elimination rates, bioconcentration factor and half-life time) and multibiomarkers assessed: immunotoxicity (density, viability and differential cell count of hemocytes), cytotoxicity (lysosomal membrane stability - LMS), genotoxicity (DNA damage and nuclear anomalies), oxidative stress (superoxide dismutase - SOD, catalase - CAT, glutathione peroxidase - GPx and glutatione-S-Transferase - GST), metal exposure (metallothionein - MT), oxidative damage (lipid peroxidation - LPO), tissue-level biomarkers (17 histomorphometric parameters of digestive tubules, inflammatory and histopathological conditions indices) and proteomic responses. Results showed that the digestive gland plays an important role in storage, metabolism and detoxification of QDs, while gills have similar functions for dissolved Cd and the hemolymph in transport, distribution and regulation of QDs. Tissue specific metabolism patterns and nano-specific effects were identified, wherein the MoA and toxicity of QDs in mussels is time dependent and involve oxidative stress, immune response, DNA damage and differential protein expression. Mussels were unable to completely eliminate the QDs (t1/2 > 50 days), highlighting their potential source of toxicity for human health and environment. M. galloprovincialis is a significant target of QDs ecotoxicity and represent a suitable biomonitor for assess their environment risk.

2016-07-25Doctoral thesis

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