Environmental Engineering Reference
In-Depth Information
5)
in vitro
. The bronchoalveolar carcinoma cell line was more sensitive to the silica
nanoparticle induced cytotoxicity than to the Min-U-Sil 5. These nanoparticles were
found to generate ROS, to induce oxidative stress (glutathione depletion) and lipid
peroxidation.
These studies suggests that the silica nanoparticles have the potential to induce
acute effects both
in vitro
and
in vivo
, but much more work is needed before risk
can be determined.
A small number of studies have also investigated the toxicity of iron oxide
nanoparticles. Such particles are being developed for a number of medical
applications including magnetic resonance contrast agents for MRI (Choi
et al.
,
2004). Since the route of entry into the body will be injection there is little doubt
about exposure to such nanoparticles. Gojova
et al.
(2007) exposed endothelial
cells
in vitro
to iron oxide (Fe
2
O
3
) or zinc oxide (ZnO) nanoparticles. Both nano-
particles were taken up by the endothelial cells. The iron oxide particles had
no effect on the endothelial cell pro-infl ammatory gene expression, while zinc oxide
particles generated a pro-infl ammatory response at concentrations greater than
10
g/ml.
A number of studies have investigated neuronal effects of iron oxide, due to
increased use in imaging the central nervous system (CNS) by magnetic resonance
imaging (MRI). In a study using the neuronal cell line PC12, Pisanic
et al.
(2007)
found iron oxide (Fe
2
O
3
) particles to induce a dose dependent cytotoxicity, as well
as decreased neurite generation. In a study by Muldoon
et al.
(2005) rats were
exposed to commercial preparations of iron oxide, which were either injected
directly into the cerebellum, or into the blood of rats with an incomplete blood-
brain barrier (BBB), or into rats with intracerebral tumour xenografts. MRI imaging
revealed that MRI signal declined over weeks to months following the intracerebral
injection, suggesting that the particles were cleared from the CNS. For the nanopar-
ticles injected into rats with a defective BBB, a CNS MRI signal could be detected
transiently for some samples (three days) and more long term for others (28 days).
These exposures were not associated with pathological changes to the CNS of
normal rats. However, in one of the three tumour models investigated, some tumour
enhancement was observed in one animal. The authors suggest that these results
demonstrate the safety of the commercially available iron oxide preparations used
for MRI. Further work is required to verify this result.
Hussain
et al.
(2005) compared the impact of a range of nanoparticles, including
iron oxide (Fe
3
O
4
), TiO
2
and silver on the rat liver derived cell line BRL 3A. As
described previously, the silver (5- 50
µ
g/ml) nanoparticles decreased mitochondrial
function (MTT assay) and cell death (LDH assay), while Fe
3
O
4
and TiO
2
at the
same concentration had no signifi cant impact on either endpoint. Concentrations
had to be increased to 100- 250
µ
g/ml before signifi cant effects of these two metal
oxides could be detected in these two assays.
µ
9.3.5
Quantum Dots
Quantum dots are semi-conducting nanoparticles often made from cadmium sel-
enide (CdSe) or cadmium telluride (CdTe). These nanoparticles generate light, the
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