No bioavailability of 17α-ethinylestradiol when associated with nC60 aggregates during dietary exposure in adult male zebrafish (Danio rerio)

The C60 fullerene is a manufactured carbon nanoparticle (CNP) that could pose a risk to humans and other organisms after release into the environment. In surface waters, C60 is likely to be present as aggregates of nC60 and these aggregates can associate with other substances that are toxic. Our goal was to evaluate the association of a model contaminant [17α-ethinylestradiol (EE2)] with nC60 and determine bioavailability of EE2 after accumulation by a filter feeding organism [Brine shrimp (BS) Artemia sp.] and subsequent dietary exposure in zebrafish. Aqueous suspensions of nC60 were prepared (600 mg C60/900 mL, 6-month water stirred method) with/without EE2 (1 μg/L) and BS were exposed to these preparations. Accumulation of nC60 in gut of BS was assessed by light microscopy, and C60 were extracted from BS and concentration analyzed by HPLC. Adult male zebrafish were fed (5 d) live BS according to the following treatments: BS (control); BS containing nC60; BS containing nC60 + EE2; or BS containing EE2. Liver was excised from exposed fish and total RNA was extracted for assessment of vitellogenin gene (vtg1A/B) expression. The vtg1A/B was highly up-regulated in fish exposed to BS containing EE2, but expression of vtg1A/B did not differ from controls in other treatments. The EE2 associated with nC60 did not become bioavailable in zebrafish during passage through the intestinal tract of zebrafish. Results have implications on the effect of nC60 on the bioavailability of co-contaminants in organisms during dietary exposure.