TiO<sub>2</sub> Nanoparticle Exposure and Illumination
during Zebrafish Development: Mortality at Parts per Billion Concentrations
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Abstract
Photoactivation of
titanium dioxide nanoparticles (TiO<sub>2</sub>NPs) can produce reactive
oxygen species (ROS). Over time, this has
the potential to produce cumulative cellular damage. To test this,
we exposed zebrafish (<i>Danio rerio</i>) to two commercial
TiO<sub>2</sub>NP preparations at concentrations ranging from 0.01
to 10 000 ng/mL over a 23 day period spanning embryogenesis,
larval development, and juvenile metamorphosis. Fish were illuminated
with a lamp that mimics solar irradiation. TiO<sub>2</sub>NP exposure
produced significant mortality at 1 ng/mL. Toxicity included stunted
growth, delayed metamorphosis, malformations, organ pathology, and
DNA damage. TiO<sub>2</sub>NPs were found in the gills and gut and
elsewhere. The two preparations differed in nominal particle diameter
(12.1 ± 3.7 and 23.3 ± 9.8 nm) but produced aggregates in
the 1 μm range. Both were taken up in a dose-dependent manner.
Illuminated particles produced a time- and dose-dependent increase
in 8-hydroxy-2′-deoxyguanosine DNA adducts consistent with
cumulative ROS damage. Zebrafish take up TiO<sub>2</sub>NPs from the
aqueous environment even at low ng/mL concentrations, and these particles
when illuminated in the violet-near UV range produce cumulative toxicity