Toxicological Effects of Metal Nanomaterials - Safety of Nanomaterials along Their Lifecycle - page 203

and an increased cell adhesion as signs of inflammation (Cho et al. 2009). In another
study, the group investigated PEG-coated gold nanoparticles of 4 and 100 nm size.
These were intravenously administered by single injection at a dose of 4.26 mg/kg
body weight. After 30 min, mice were sacrificed and histological and genetic effects
were analyzed. Whereas no pathological changes were found in the liver tissues,
expression of genes involved in inflammation, metabolism, and apoptosis was signifi-
cantly changed. The changes seemed to be independent of the particle size, because
both the 4 and 100 nm gold particles displayed similar effects and altered the expres-
sion of the same gene categories (Cho et al. 2009). The impact of size on toxicity was
studied in detail by Chen et al. using 3, 5, 8, 12, 17, 37, 50, and 100 nm gold nanopar-
ticles for intraperitoneal injections of 8 mg/kg body weight/week to Balb/C mice. No
evidence of toxicity was found for 3, 5, 50, and 100 nm particles. In contrast, all other
gold nanoparticles used (8, 12, 17, and 37 nm) induced severe toxic effects in the liver,
spleen, and the lungs accompanied by fatigue, weight loss, and death within 21 days
(Chen et al. 2009). These findings suggest that the toxicity of gold nanomaterials
is not solely driven by their size but also by other particle-specific properties. This
seems to become more apparent by the data obtained by Lasagna-Reeves et al., who
found no signs of toxicity for gold nanoparticles of 13 nm size after intraperitoneal
administration to mice. It is, however, difficult to compare these findings to the data
obtained for 12 nm gold nanoparticles because the doses used here (0.04, 0.2, and
0.4 mg/kg body weight for 8 days) were 3-30 times lower compared to those used by
Chen et al. (Lasagna-Reeves et al. 2010; Chen et al. 2009). In summary, from the few
studies on in vivo toxicity of gold nanoparticles conducted so far it is impossible to
correlate their physicochemical properties to their toxic effects.
9.4.2 e ffeCts of m etal n anoPartiCles on h umans
A health surveillance study conducted by Lee et al. determined silver deposition in
blood and urine of two workers from a facility manufacturing silver nanoparticles
of 20-30 nm. In one of the two workers (who worked there for 7 years), silver was
detected in the blood at a concentration of 0.034 and 0.0135 µg/dL and in the urine at
a concentration of 0.043 µg/dL, whereas in the other worker, silver was found neither
in the blood nor in the urine. Adverse health effects could not be detected and blood
chemistry and hematology data were within the normal range (Lee et al. 2012).
Moreover, silver is known to display wound healing effects which are exploited in
wound dressings, and following exposure to damaged skin, silver has been reported
to become systemically available (Johnston et al. 2010). In a clinical study, Vlachou
et al. treated 30 burn patients with nanosilver (15 nm) containing wound dressings for
28 days or less and determined the systemic availability and potential toxic effects.
They found serum levels of silver being increased during exposure to the dress-
ings and up to 6 months after cessation of the treatment indicating that silver ions
or nanoparticles become systemically available. However, no signs of toxicity on
the biochemical or hematological level could be found (Vlachou et al. 2007). Silver
deposition after treatment with wound dressings has also been reported in another
case study in which a burn patient displayed argyria (Trop et al. 2006) a gray discol-
oration of the skin presumably caused by the formation of metallic silver by UV light