Cadmium sulfide quantum dots induce oxidative stress and behavioral impairments in the marine clam Scrobicularia plana

Abstract

Cadmium sulfide (CdS) quantum dots have a number of current applications in electronics and solar cells and significant future potential in medicine. The aim of the present study was to examine the toxic effects of CdS quantum dots on the marine clam Scrobicularia plana exposed for 14 d to these nanomaterials (10 µg Cd L(-1) ) in natural seawater and to compare them with soluble Cd. Measurement of labile Cd released from CdS quantum dots showed that 52% of CdS quantum dots remained in the nanoparticulate form. Clams accumulated the same levels of Cd regardless of the form in which it was delivered (soluble Cd vs CdS quantum dots). However, significant changes in biochemical responses were observed in clams exposed to CdS quantum dots compared with soluble Cd. Increased activities of catalase and glutathione-S-transferase were significantly higher in clams exposed in seawater to Cd as the nanoparticulate versus the soluble form, suggesting a specific nano effect. The behavior of S. plana in sediment showed impairments of foot movements only in the case of exposure to CdS quantum dots. The results show that oxidative stress and behavior biomarkers are sensitive predictors of CdS quantum dots toxicity in S. plana. Such responses, appearing well before changes might occur at the population level, demonstrate the usefulness of this model species and type of biomarker in the assessment of nanoparticle contamination in estuarine ecosystems.

Tissue specific responses to cadmium-based quantum dots in the marine mussel Mytilus galloprovincialis

“…The observed results agree with previous studies about the oxidative stress in bivalve species induced by Cd-based QDs (i.e. CdS and CdTe QDs) (Gagné et al, 2008a;Buffet et al, 2015), showing that CdTe QD exposure causes impairment or overcoming of the antioxidant defences in M. galloprovincialis, whereby oxidative stress is promoted. It may be related to genotoxic, immunotoxic and cytogenotoxic effects (Rocha et al, 2014;2015a).…”

“…in several studies using in vitro and in vivo exposure (Gagné et al, 2008a;Peyrot et al, 2009;Katsumiti et al, 2014;Rocha et al, 2014;2015a;Buffet et al, 2015). However, the mechanisms of QD-mediated toxicity are not well established and depend on size, chemical composition, surface coating and exposure conditions.…”

“…On the other hand, other studies indicate that the generation of free radicals or reactive oxygen species (ROS) associated with oxidative damage are the major mode of action (MoA) of Cd-based QDs (Gagné et al, 2008a;Buffet et al, 2015).…”

“…From the context of aquatic nanotoxicology, bivalve species have the higher capacity to concentrate Cd-based QDs from water than other animals, which can induce severe tissue and cellular damage (Gagné et al, 2008a;Peyrot et al, 2009;Rocha et al, 2014;2015a;Buffet et al, 2015). In vitro toxicity of CdS QDs (5 nm; 10 -4 -10 2 mgCd.L -1 ; 24 h) in Mytilus galloprovincialis hemocytes and gill cells was associated with extraand intracellular release of Cd 2+ ions and consequent oxidative damage (Katsumiti et al, 2014).…”

“…Therefore, Cd levels in mussel tissues are Cd form and tissue dependent and the dissolved Cd is the most bioavailable form (Hull et al, 2013;Rocha et al, 2015a). On the other hand, these results disagree with previous studies that showed similar Cd accumulation in the whole soft tissue of the marine clam S. plana exposed to CdS QDs (5-6 nm; 10 µgCd.L -1 ; 14 d) (Buffet et al, 2015) and in the gills and digestive gland of the freshwater mussel E. complanata exposed to CdTe QDs (1.6 -8 mg.L -1 ; 24 h) (Peyrot et al, 2009). In this study, tissue-specific Cd accumulation in M.…”