TOXICOLOGICAL EFFECTS OF DIETARY QUANTUM DOT EXPOSURE IN TELEOSTS
Twyla Michelle Blickley, Cole W. Matson, Wyatt N. Vreeland, Dan Rittschof, Richard T. Di Giulio, and Patricia D. McClellan-Green
Quantum dots (QDs) are semi-conducting nanocrystals that emit tunable fluorescence. While QDs are already commercially available in products for the medicinal, manufacturing, telecommunications, and life science research fields, little is known about the effects of these engineered nanoparticles in estuarine organisms. Initial observations of QD behavior in natural estuarine waters showed considerable aggregation and precipitation to the sediments, thus our investigations focused on the effects of lecithin-encapsulated CdSe/ZnS QDs in adult Fundulus heteroclitus, the mummichog, following dietary exposure to 1 µg or 10 µg of QD /fish/day for a period of 3 months. Measurement of tissue cadmium concentrations showed that QDs were bioavailable to adult Fundulus. While QDs or their degradation products traversed the intestinal epithelial and were deposited to the liver, less than 0.01 % of the cadmium from the QDs was retained in the liver and intestinal tissues. QD uptake did not cause significant changes in hepatic total glutathione or lipid peroxidation levels, nor did it statistically alter the expression of genes involved in metal metabolism and oxidative stress— metallothionein, glutathione-s-transferase, glutathione peroxidase, and superoxide dismutases. There was, however, a clear gender-specific trend in the level of Cu/Zn-superoxide dismutase transcription. In addition, vitellogenin transcription was elevated and relative gonad size reduced in male Fundulus consuming 10 µg QD per day. Lastly, QDs or their degradation products were maternally transferred to the eggs following six to eight weeks of parental exposure, thus posing a risk to Fundulus progeny. Based on the results of these studies, it is apparent that chronic exposure to QDs could result in adverse affects in teleosts and other organisms inhabiting estuarine environments.