| dc.description.abstract |
<p>Engineered nanoparticles (ENPs) are a part of everyday life. They are incorporated
into a wide array of products including sunscreens, clothing, electronics, paints,
and automobiles. One particular type of ENP, quantum dots (QDs), are fluorescent
semi–conducting nanocrystals, and are touted as the next generation of medical
tracers and energy–efficient light bulbs. The continued development and expansion
of commercial applications for QDs ensure that they will enter the aquatic environment
following manufacture, use, and disposal. Unfortunately, very little information
exists on the bioavailability and sub–lethal toxicological effects of QDs in
aquatic organisms. The studies described in this dissertation focused on determining
the toxicological effects of Lecithin–encapsulated CdSe/ZnS quantum dots in
larval and adult <italic>Fundulus heteroclitus</italic> (the mummichog). </p>
<p>Quantum dot dispersion is greatly influenced by environmental parameters such as
pH, natural organic matter concentration, and ionic strength. Lecithin–encapsulated
core–shell QDs aggregated and precipitated from suspension in 20 ppt seawater.
QD aggregates adhered to the exterior chorion of <italic>Fundulus</italic> embryos
in aqueous embryo exposures, but did not traverse the chorion and deposit into the
body of the fry. Incidences of developmental abnormalities increased and hatching
rates declined in embryos exposed to the highest concentration tested (100 μg/ml).
</p>
<p>Dietary assessments showed that QDs were bioavailable to adult <italic>Fundulus</italic>.
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, QDs did impact fecundity presumably by feminizing
male fish. Vitellogenin transcription was elevated and relative gonad size reduced
in male <italic>Fundulus</italic> 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 <italic>Fundulus</italic> 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.</p>
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