Biomedical Engineering Reference
In-Depth Information
TABLE 3.6
Studies on Toxicity Due to Particle Shape and Aspect Ratio
Type of Nanoparticle
Toxicity/Organ Affected
Mechanism Involved/Results
Reference
ZnO nanorods and
nanospheres
Cytotoxicity
The nanorods and nanospheres had similar
cytotoxicities after exposure for 12 h;
after 24 h, however, the nanorod ZnO
nanoparticles were more toxic than the
nanosphere ZnO nanoparticles with values
of EC50 for ZnO-R8 and ZnO-S6 of 8.5
and 12.1 μg mL
−1
, respectively.
Hsiao and
Huang (2011)
Denritic TiO
2
nanoparticles
Cytotoxicity/Mouse
macrophage cell line
Dendritic TiO
2
nanoparticles induce the
highest degree of cytotoxicity toward the
mouse macrophage cell line (J774A.1),
followed by spindle- and sphere-shaped
nanoparticles.
Yamamoto
et al. (2004)
Nanotubes
Multifocal granulomas lesions
New mechanism of
pulmonary toxicity
On a dose per mass basis the nanotubes
were more toxic than quartz particles
although the mass dose was very high and
mechanical blockage of some airways was
noted.
Warheit et al.
(2004)
Single-walled CNTs
(fiber shaped)
Carcinogenic effects/Lung
granulomas after intrathecal
administration
Nanotubes which may be of a few
nanometers in diameter but with a length
that could be several micrometers.
Lam et al.
(2004)
3.5.1.3 Surface Chemistry and Charge
Surface chemistry is a critical parameter in determining the toxicity of nanoparticles and is espe-
cially relevant to molecular cell chemistry and oxidative stress. Based on their chemistry and charge
(zeta potential), nanoparticles can show different cellular uptakes, subcellular localizations, and the
ability to catalyze the production of ROS (Xia et al. 2006). These toxicity effects are described in
Table 3.8.
3.5.2 d
ose
-d
epeNdeNt
t
oxIcIty
A dose is defined as the
amount
or
quantity
of substance that will reach a biological system. The
dose is directly related to exposure, or the concentration of the substance in the relevant medium
(air, food, water), multiplied by the duration of contact. Various toxicity effects, well studied by sci-
entists and based on doses, are discussed in Table 3.9 with organ specificities and the mechanisms
by which it is caused.
3.5.3 c
oNceNtratIoN
aNd
d
rug
-l
oadINg
-d
epeNdeNt
t
oxIcIty
The resultant effects of different concentrations on nanoparticle toxicities are very contradictory.
Research shows that certain concentrations of materials are not as toxic as were observed by other
researchers. This may be due to differences in the aggregation properties of nanoparticles in air
and water, resulting in inherent discrepancies between inhalation studies and instillation or
in vitro
experiments. The aggregation may depend on the zeta potential, material type, size, and many oth-
ers factors.
The aggregation of nanoparticles is one of the most important and essential parameters in deter-
mining its toxicity, because large, aggregated particles more effectively cleared by macrophages as
compared to smaller particles, leading to the reduced toxicity of nanoparticle aggregates larger than
