Environmental Engineering Reference
In-Depth Information
Worldwide concern is currently shared by experts about the effects of
nanoparticles, be they engineered or be they the result of undesirable side effects
of other technologies [
1
,
2
].
The concern is mostly due to the fact that, because of their very small size, they
can interact directly with proteins, enzymes, the DNA, and other substances present
in all organisms, and that “nano-bio-interaction” can induce toxic effects at cell
level about which we know very little. And even less is known about the long-term
effects that these products can have on human and animal life and on the environ-
ment. As to the fate of nanoparticles at the end of their life cycle as products or
product components, we know nearly nothing.
As mentioned above, nanoparticles started to be used also in Medicine. Their
capability of crossing the blood-brain barrier offers great possibilities to drugs
aimed at the brain and brain pathologies. At present the molecules of the neuro-
logical drugs are recognized as not-self and rejected by the blood-brain barrier. The
concept is rather simple: the drug is embedded/absorbed by the nanoparticles that
once injected can cross the physiological barrier and when the target has been
reached they start to biodegrade and release the active principle. They act as a
“Trojan-horse.” The evident problem is the biocompatibility of the particles.
Concept that is unknown to the nanotechnologists, namely that the human body
has a defense system able to recognize molecules and chemical compounds, but can
be invaded by nanoparticles since they represent non-specific stimulus, but once
they interact with cell compounds or organelles some reaction of “non-acceptabil-
ity” can be triggered, since they are “foreign bodies.”
Another use that has been attempted, actually with very dubious results, so that
almost all products have been phased out, was the injection of iron-oxide
nanoparticles with substances that show a particular affinity for tumor cells, inter-
nalized. Once the patient is introduced into a strong magnetic field, the magnetic
particulate matter is driven to the cancerous tissue while sparing the healthy cells
and for their higher X-ray density than the surrounding tissue they help to define
with high sensitivity the borders of cancer. These images help the surgeon to better
define the contours of the area to be excised. There is the possibility to treat directly
the cancer. An external microwave field can be generated inducing a heating of the
iron-oxide particles. The heating occurs at a temperature high enough to kill
the cells, that the cancer is somehow eliminated. In this case after the treatment
the iron-oxide nanoparticles remain in the dead tissue.
Once again, the problem is there of the non-biocompatibility of particles whose
removal is something of which no solid evidence exists. Probably the long-term
permanence and the non-biodegradability of these types of nanoparticles can induce
other bad side-effects.
If the ones just briefly described are just experimental attempts, the oral intake of
colloidal Silver is a widespread practice of self-medication. Apart from the many
uses of Silver, be they or be they not backed by demonstrations of their true
usefulness, those particles, much smaller than 1
m as they are, are not biodegrad-
able and there is no reason why they should behave in a different way from any other
non-biodegradable particles. There is no evidence that their chronic use is the cause
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