Biomedical Engineering Reference
In-Depth Information
Rat inhalation studies with stainless-steel welding fumes showed that manganese accumulates
in the blood and liver (Donaldson et al. 2005). Rat inhalation studies with 4-10 nm silver nanopar-
ticles show that the nanoparticles enter the circulatory system within 30 min, and can be found in
the liver, kidney, and heart after a day until being subsequently cleared from these organs after a
week (Takenaka et al. 2001). Clearances from the liver can occur via biliary secretion into the small
intestine (Cooper et al. 1979).
A case study shows that wearing dental bridges leads to the accumulation of nanoparticles in the
liver and kidneys. The most probable absorption pathway was assumed to be via intestinal absorp-
tion (Ballestri et  al. 2001). Scanning electron microscopy and energy-dispersive microanalytical
techniques identified the chemical compositions of particles in liver and kidney biopsies as well in
the stool as the same as porcelain from dental prostheses. The maximum size of particles found in
the liver (20 μm) was larger than in the kidneys (below 6 μm), suggesting that particles are absorbed
by the intestinal mucosa and translocate to the liver before reaching the circulatory system and kid-
neys. After the removal of dental bridges, particles in stool are no longer observed.
14.1.3 a dverse h ealth e ffects of l Iver aNd k IdNey u ptake
Up to now, there is little knowledge on the effect of nanoparticles on organs such as the liver,
kidneys, and spleen. However, one can speculate that as long as there is the translocation to and
accumulation of nanoparticles in these organs, potentially adverse reactions and cytotoxicity may
lead to disease.
Diseases with unknown origins have been correlated with the presence of micro- and nanopar-
ticles in the kidneys and liver. For comparison, the liver and kidneys of healthy subjects did not
show any debris. Particle debris has been found also in the liver of patients with worn orthopedic
prosthesis (Gatti and Rivasi 2002).
Dental prosthesis debris internalized by intestinal absorption can lead to severe health conditions,
including fever, enlarged spleen and liver, suppression of bile flow, and acute renal failure. These symp-
toms appeared about a year after the application of dental porcelain bridges. After the removal of dental
bridges and subsequent treatment with steroids, the clinical symptoms declined (Ballestri et al. 2001).
14.2
TOXICITY OF NANOMATERIALS ON THE LIVER
14.2.1 l Iver M orphology
The liver engages in numerous metabolic, immunological, and endocrine functions. It receives blood
from the gut and the heart via the portal vein and hepatic artery, respectively (Figure 14.1a). Blood
circulates through a permeable, discontinuous capillary network (the sinusoids) to reach the central
and hepatic veins (Figure 14.1b). The sinusoids are 5-10 μm-wide blood vessels with a fenestrated
epithelium without any basal membrane (Figure 14.1c). The size of the fenestrations (100-150 nm
depending on the animal species) allows the almost unrestricted passage of plasma components to
the perisinusoidal space, where the cords of parenchymal cells (hepatocytes) are situated (Wisse
et al. 2008; Jacob et al. 2010). Inside the sinusoid capillaries, Kupffer cells are responsible for the
phagocytic activity of the liver. These nonparenchymal cells belong to the mononuclear phagocyte
system and represent 80-90% of the body's total macrophage population. This defense system was
formerly known as the reticuloendothelial system, but the name became obsolete when it was under-
stood that endothelial cells are not macrophages responsible for the clearance of pathogens.
14.2.2 p hagocytosIs IN k upffer c ells
Phagocytosis occurs after the multivalent contacts of the colloid with macrophages and spread-
ing of the cell membrane around the particle for engulftion. After ingestion, phagocytic vesicles
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