Biomedical Engineering Reference
In-Depth Information
CNTs and polymers, allow for a better control of conductivity and are attractive for a wide range of
applications, such as supercapacitors, sensors, and solar cells (Baibarac and Gomez-Romero 2006).
1.4.4.8 Paint
NPs impart improved, required, mechanical properties to composites, such as scratch-resistant
paint, based on the encapsulation of NPs (Borup and Leuchtenberger 2002). The wear resistance of
such coatings is estimated to be 10 times larger than that of conventional acrylic paints.
1.4.4.9 Cutting Tools
Cutting tools consisting of nanocrystalline materials, such as tungsten carbide, are much harder
than conventional forms because of the enhanced microhardness property of nanosized composites
as compared to that of microsized composites (Yao et al. 2002).
1.4.4.10 Lubricants
Nanospheres made up of inorganic materials may be used as lubricants, acting as nanosized ball
bearings (Fleischer et al. 2003).
1.5 NANOTOXICITY
The term “nanotoxicology,” coined in 2004, refers to the evaluation of the detrimental outcomes
of nanostructure interactions with biological and ecological systems. It includes physicochemical
determinants, routes of exposure, biodistributions, molecular determinants, genotoxicities, and
regulatory aspects. Nanotoxicology has emerged as a subdiscipline of nanotechnology to address
the potential environmental, health, and safety risks that come with the applications of NMs (Arora
et al. 2012, Donaldson et al. 2004, Fischer and Chan 2007).
The anticipation of the toxicological hazards of nanostructure materials, due to their unique
properties (e.g., chemical, electrical, and magnetic) and the potential for systemic availabil-
ity and environmental occurrence, has raised concerns among many scientists, regulators, and
nongovernmental agencies since the beginning of the 2000s (Colvin 2003, Santamaria 2012).
During this time, multidisciplinary research programs were initiated by the National Center
for Environmental Research of the United States Environmental Protection Agency, National
Toxicology Program, National Institute of Environmental Health, and National Institutes of
Health to initiate and promote research on the impact of NMs on human health and the environ-
ment (Santamaria 2012).
In the early 1980s, several toxicological and epidemiological studies were conducted to evaluate
the respiratory toxicity and pulmonary effects of ambient, ultrafine particles present in the atmo-
sphere as result of natural and anthropogenic activities. Enhanced inflammatory responses in the
lungs of rats were found with exposure to TiO
2
and aluminum oxide (Al
2
O
3
) NPs as compared to
larger particles of the same mass and chemical compositions (Ferin et al. 1990, Oberdorster et al.
1990). In the 1990s, sunscreen products came under evaluation for the potential dermal penetration
of TiO
2
and ZnO NPs, as they were being used in dermally applied products. With a simultane-
ous interest in the research of NPs as drug delivery systems, potential outcomes were observed in
the evaluation of the inhalation risk of engineered NMs, such as CNTs, in rodent toxicity studies
(Shvedova et al. 2005, Warheit et al. 2004). This created an immense interest among toxicology com-
munities in 2004. The significant acute inflammatory pulmonary effects were more pronounced in
mice (Lam et al. 2004, Shvedova et al. 2005) as compared to rats (Warheit et al. 2004) in the intra-
tracheal dosing of single- or multi-walled carbon nanotubes. The field of ecotoxicology was high-
lighted with a study that evaluated the effects of carbon fullerenes on largemouth bass and reported
lipid peroxidation in the brain and gills (Oberdorster et al. 1990). Since 2000, research has also been
focused on the evaluation of the toxicokinetics and toxicodynamics of NMs; the ingestion of NMs
from food; and the use of NMs in medical devices, diagnostics, and therapeutics (Santamaria 2012).
