Biomedical Engineering Reference
In-Depth Information
nanoscaled gold particles. Another application for the catalytic properties of
nanosized gold particles is for fuel cells of hydrogen batteries.
One hundred and fifty years after one of the founders of chemistry, Michael
Faraday, first created gold nanoparticles in the 1850s and observed that these
nanoparticles absorb light, researchers in the twentieth century rediscov-
ered that a mere flash of light can cause gold particles to melt. Absorbed
light is efficiently turned into extreme heat, which is capable of killing can-
cer cells. The externally applied energy may be mechanical, radiofrequency,
laser, optical, or near-infrared light, but the resultant therapeutic action is
the same. Gold nanoparticles are also recognized by their ability to bind to
DNA, which may be exploited for the treatment of diseases, for example, as
anticancer agents or gene therapy agents; however, they may also contribute
to genotoxicity, or block transcription.
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Hamad-Schifferli et al.
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have dem-
onstrated that transmitted radiosignals influence the integrity of the DNA
strand while it is bound to nanoparticle gold molecules. This discovery
opens up the possibility of controlling more complex biological processes
of living cells, such as enzymatic activity, protein folding, and biomolecular
assembly. Furthermore, the ability of gold nanoparticles to bind to DNA is of
concern, owing to their potential cytotoxic or genotoxic consequences, which
may be exploited for anticancer drugs or gene therapy, and warrants further
investigation. In addition, the ability of gold nanoparticles to interrupt tran-
scription is of concern.
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Naomi Halas of Rice University (Houston, TX) developed gold nanoshells
in the 1990s. According to the study's lead authors, Rebekah Drezek and
Jennifer West, nanoshells have a core of silica and a metallic outer layer of
gold, or may be exchanged by copper or iron. Nanoshells will preferentially
concentrate in cancer lesion sites. In her interview with Nova, Naomi Halas
describes a nanoshell as “essentially a nanolens” that captures light and then
focuses it around itself.
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A near-infrared laser aimed at the tumor site from
outside the body (light can travel through tissue more than 10 cm) induces
the nanoshells to absorb the light and focus it on the tumor. The area around
the nanoshells heats up and the tumor “cooks” until it is ablated. Halas
points out that the nanoshells leave no “toxic trail” in the body the way con-
ventional chemotherapeutic agents do, and stated that “long-term studies
have not indicated any toxicity or effect on the immune system.”
The structure and properties of gold nanoparticles make them attractive
for a wide range of biological applications. Nanoparticle gold is considered a
low-toxicity material and is currently widely used in cosmetology.
Actually, nanostructured gold particles possess various properties that are
under investigation and need longer time to final approval. Few if any of
the fabricated nanoparticle gold-containing medications are yet approved by
the FDA. In August 2009, a report of the EU Seventh Framework Program,
“Engineered Nanoparticles: Review of Health and Environmental Safety,”
was released.
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