Toxicological Effects of Metal Nanomaterials - Safety of Nanomaterials along Their Lifecycle - page 202

inflammatory responses in mice (Park et al. 2010). In a comparative study of iron
and copper nanoparticles, Pettibone et al. used 25 nm copper nanoparticles for both
subacute and acute inhalation studies. For acute exposure, the animals were exposed
to copper for 4 h/day and sacrificed within an hour after exposure. For the subacute
exposure, mice were exposed for 4 h/day for 2 weeks (5 days/week) and necropsied
within 1 h or 3 weeks post exposure. No significant signs of toxicity were found fol-
lowing acute exposure. However, immediately after the subacute exposure to copper
or iron nanoparticles, an increase in inflammatory cytokines was observed, with
copper being significantly more effective than iron nanoparticles. The authors dis-
cussed a contribution of copper ions to the observed effects, because copper was
found to partially dissolve in the solutions used, whereas dissolved iron was not
detected (Pettibone et al. 2008).
In the nanoGEM project, silver nanoparticles of different size and coatings (see
the aforementioned) were exposed to rats via intratracheal instillation. Among these,
Ag50.PVP, Ag200.PVP, and Ag50.citrate (0.6 mg/lung) elicited very strong signs of
inflammation: Differential cell counts of the broncho-alveolar lavage fluid (BALF)
revealed a significant increase in macrophage and granulocyte (PMN) counts after
3 days. After 21 days the effects on PMN were even more pronounced for Ag50.
PVP and Ag50.citrate (Table 9.2) but partially reversed for Ag200.PVP. The BALF
from Ag50.PVP- and Ag200.PVP-treated animals contained numerous large macro-
phages laden with dark silver grains, whereas Ag50.citrate-treated animals showed
agglomerates of silver particles predominantly outside the cells. The rank order of
in vivo toxicity was Ag50.PVP > Ag50.citrate > Ag200.PVP. In a second study, we
investigated the concentration dependence effects upon application of Ag50.PVP.
Significant changes in cell counts and protein concentration in BALF appeared for
0.075 mg per rat lung. This value was below what might have been expected from
the in vitro studies with AM, which had suggested effects to begin in the range of
0.3 mg/lung. * However, as the uptake of Ag nanoparticles in vitro was incomplete
(Hinderliter et al. 2010), cytotoxicity measurements underestimated the effect in
vivo , where the complete dose is delivered to the organ. This example underlines the
necessity to determine the cellular dose when AM or other cells are used to predict
effects on the whole lung.
9.4.1.1.3 Intraperitoneal/Intravenous Injections
Due to the exploitation of gold nanomaterials in therapeutic and diagnostic fields of
nanomedicine, their biodistribution following intravenous or intraperitoneal injections
of rodents has been intensively studied. A few of these studies, however, have assessed
the in vivo toxic effects of these nanomaterials. Using intravenous injection, Cho et al.
administered PEG-coated gold nanoparticles (13 nm) at single doses of 0.17, 0.85, and
4.26 mg/kg body weight to mice (Cho et al. 2009). For up to 7 days post injection, they
observed acute inflammation and apoptosis within the liver, which was the primary
site of accumulation. They found increased cytokine levels, infiltration of neutrophils,
* The mean dose per cell found at the LOAEL in vitro may be multiplied by 2 × 10 7 , which is the mean
number of alveolar macrophages per rat lung (Rehn et al. 1992), to obtain a first estimation of a critical
dose for an instillation experiment.