J. Clin. Biochem. Nutr. | May 2012May 2012 | vol. 50 | no. 3 | 211–216doi: 10.3164/jcbn.11-70
JCBN Journal of Clinical Biochemistry and Nutrition0912-00091880-5086 the Society for Free Radical Research Japan Kyoto, Japanjcbn11-7010.3164/jcbn.11-70Original Article
Metal nanoparticle-induced micronuclei
and oxidative DNA damage in mice
Ming-Fen Song, Yun-Shan Li, Hiroshi Kasai and Kazuaki Kawai*
Department of Environmental Oncology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health,
1-1, Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan
*To whom correspondence should be addressed.
(Received 17 May, 2011; Accepted 18 July, 2011)
Copyright © 200? JCBN200? This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unre-stricted use, distribution, and reproduction in any medium, pro-vided the original work is properly cited.
Several mechanisms regarding the adverse health effects of nano-
materials have been proposed. Among them, oxidative stress is
considered to be one of the most important. Many in vitro studies
have shown that nanoparticles generate reactive oxygen species,
deplete endogenous antioxidants, alter mitochondrial function and
produce oxidative damage in DNA. 8-Hydroxy-2'-deoxyguanosine
is a major type of oxidative DNA damage, and is often analyzed
as a marker of oxidative stress in human and animal studies. In
this study, we focused on the in vivo toxicity of metal oxide and
silver nanoparticles. In particular, we analyzed the induction of
micronucleated reticulocyte formation and oxidative stress in
mice treated with nanoparticles (CuO, Fe3O4, Fe2O3, TiO2, Ag). For
the micronucleus assay, peripheral blood was collected from the
tail at 0, 24, 48 and 72 h after an i.p. injection of nanoparticles.
Following the administration of nanoparticles by i.p. injection to
mice, the urinary 8-hydroxy-2'-deoxyguanosine levels were
analyzed by the HPLC-ECD method, to monitor the oxidative stress.
The levels of 8-hydroxy-2'-deoxyguanosine in liver DNA were also
measured. The results showed increases in the reticulocyte micro-
nuclei formation in all nanoparticle-treated groups and in the
urinary 8-hydroxy-2'-deoxyguanosine levels. The 8-hydroxy-2'-
deoxyguanosine levels in the liver DNA of the CuO-treated group
increased in a dose-dependent manner. In conclusion, the metal
nanoparticles caused genotoxicity, and oxidative stress may be
responsible for the toxicity of these metal nanoparticles.
Key Words:nanoparticles, metal oxide, silver, oxidative stress,
greatly impacted industrial technology. With the increasing
utilization of nanoparticles, people have a greater opportunity to
be exposed to nanoparticles through the occupational environment
and consumer products in daily life. At the same time, there has
been increasing concern about the adverse effects of nanoparticles
on human health. In this study, we especially focused on the
induction of reticulocyte micronuclei and oxidative DNA damage
in vivo caused by metal oxides (CuO, Fe2O3, Fe3O4, TiO2) and
CuO nanoparticles have many commercial applications, as
components in catalysts,(1) pigments, and antimicrobial textiles.(2)
However, there are only a few reports describing the toxicity of
CuO nanoparticles in bacteria(3,4) or human lung epithelial cells.(5)
Recently, it was reported that CuO nanoparticles were highly
toxic, as compared to other metal oxide nanoparticles in vitro.(6,7)
However, the amount of in vivo data is still insufficient.
Iron oxide nanoparticles have attracted much attention, not only
due to their superparamagnetic properties but also because they
hold great potential in many biomedical applications, such as drug
delivery, magnetic resonance imaging (MRI) contrast enhance-
ment,(8–10) and the targeted destruction of tumor tissue through
Significant advances in nanotechnology in recent years have
hyperthermia.(11) However iron oxide caused a significant increase
in DNA damage in A549 cells.(7)
Nanosized TiO2 is one of the most widely used nanomaterials.
TiO2 is a poorly soluble, biologically inert particulate, which is
broadly used as a white pigment, ultraviolet light blocker, or
catalyst in a number of products, such as paints, plastics, paper,
cosmetics, medicines, foods, and welding rods.(12,13) At the same
time, The International Agency for Research on Cancer classified
TiO2 as possibly carcinogenic to humans (class 2B), based on
sufficient evidence in experimental animals. The genotoxicity of
TiO2 was also reported in several previous studies.(14–16) In general,
nanosized TiO2 particles produce reactive oxygen species,
damage DNA, and induce oxidative DNA damage in vitro.(17,18)
On the other hand, negative genotoxicity results have also been
reported.(19,20) Therefore, additional information on the genotoxicity
of nanosized TiO2 is needed.
Silver nanoparticles are used most commonly in numerous
consumer products, including textiles, cosmetics, and health care
products, due to their strong antimicrobial activity. However,
despite their widespread use, there is a serious lack of information
concerning the toxicity of silver nanoparticles to humans.(21,22)
One of the most discussed mechanisms behind the health effects
induced by metal oxide and silver nanoparticles is their ability to
cause oxidative stress.(23–27) This mechanism is believed to be
important in the toxicity of manufactured nanoparticles. Further-
more, since oxidative stress is directly linked to DNA damage,
mutations, and cancer,(28–30) nanoparticles may affect on cancer
development. Although some in vitro studies have focused on
investigating and comparing metal oxide and silver nanoparticles,
regarding DNA damage and markers for oxidative stress, the
amount of in vivo research is still insufficient. We were parti-
cularly interested in the in vivo toxicities of these types of
Nanoparticles are generally considered to be problematic in a
toxicity assessment for several reasons.(23,24–27) The small size and
the relatively large surface area have been suggested to result in
increased toxicity, as compared to micrometer-sized particles.
However, it is not clear whether the increased toxicity is a
common feature of all kinds of nanoparticles with different
chemical compositions. In particular, metal nanoparticles easily
form micrometer sized aggregates. In this study, however,
commercially available nanoparticles were tested as-is, because
the toxicities of nanoparticles should be assessed using their
commercially available forms. With regards to human exposure,
it is therefore likely that under most circumstances, the nano-
materials will exist in the form of aggregates, rather than indi-
vidual units. The aggregated form of the material may be more
representative of workplace or consumer exposure scenarios.
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