Topics Covered
Introduction
Using Gold in Anticancer
Treatment
Introduction
It is not widely known but radiactive gold was used in the
treatment of cancer many years ago. Now a number of research groups around the
world are using the unique properties of gold to develop new
anticancer treatments.
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Using Gold in Anticancer Treatment
Gold is used in the
treatment of prostate cancer. Using small gains of gold (about the size of a
grain of rice), doctors can accurately identify the position of the patient's
prostate during treatment. The improved accuracy allows for a more precise
radiation dose and a more targeted area for the treatment of the tumour. Gold is the material of
choice for the positioning grains because it is dense and opaque to X-rays.
In terms of drugs used for treating cancer, the use of platinum, in the form
of the drug Cisplatin, is well documented. Now a new generation of technologies,
potentially without the harsh side effects caused by chemotherapy drugs like
Cisplatin, are under development.
In the last few decades the properties of gold compounds have been
of interest as potential cancer treatments. Researchers at the National
University of Singapore have patented novel gold complexes for use in
pharmaceuticals for the treatment of cancer.
Associate Professor Leung Pak Hing and his team have discovered that
phosphine supported gold complexes have
excellent anti-tumour activity and clinical trials are likely to begin in the
near future.
In some cases, new technologies rely on the ability of tiny gold nanoparticles to
specifically collect in a cancerous tumour by passing through the inherently
leaky blood vessels attached to a tumour. So, when injected into a patient,
there is a means by which a potent anti-cancer compound attached to a gold nanoparticle, can be
directly and accurately delivered to a tumour whilst avoiding healthy body
tissue. Such an effective drug delivery mechanism with reduced toxicity is
considered to be a major step-forward. Why use gold as the delivery
mechanism? Well gold
has a major advantage in being a very biocompatible metal. For example,
colloidal gold has
been safely used for over 70 years to treat rheumatoid arthritis, and many
hundreds of years as a dental restoration.
Rice University chemists have used this principle to load dozens of molecules
of the anti-cancer drug paclitaxel onto gold nanoparticles.
Paclitaxel, which is sold under the brand name Taxol, prevents cancer cells
from dividing. One problem with using paclitaxel is that it works on all cells,
including healthy cells. This is why patients undergoing chemotherapy sometimes
suffer side effects like hair loss and suppressed immune function. The aim is to
deliver more of the drug directly to the cancer cells and reduce the side
effects of chemotherapy. The new delivery system is based on gold nanoparticles. The
research is published in the Journal of the American Chemical Society (J. Am.
Chem. Soc. 2007, vol. 129, pgs.11653-11661)
In 2000, a US-based company CytImmune discovered that gold nanoparticles could
bind anti-cancer compounds onto their surface and carry these drugs safely
through the blood stream, delivering them to tumours. The first first-in-man
Phase I clinical trial of CytImmune's gold-based drug began in
2006. This on-going trial will evaluate the safety of the drug and its tumour
shrinking response.
An alternative approach is being pursued by another US company Nanospectra
who are focused on the development of AuroLase Therapy to selectively destroy
solid tumours. Nanospectra use gold nanoshells (tiny
particles of gold wrapped around silica) rather than sold gold nanoparticles, but
like the CytImmune approach these are injected into the body. After the
particles accumulate in a tumour, the area is illuminated with a near-infrared
laser at wavelengths chosen to allow the maximum penetration of light through
tissue. Unlike solid gold nanoparticles,
AuroShell particles are designed to specifically absorb this wavelength,
converting the laser light into heat. This results in the rapid destruction of
the tumour along its irregular boundaries. Preclinical studies have shown that
the therapy is highly effective and the company are currently intending to seek
FDA approval to ommence a human trial for the treatment of head and neck
cancers.
Early detection of tumors is another key objective of cancer research because
it would greatly improve cancer therapy and prognosis. At the University of
Florida, Weihong Tan and colleagues are using gold nanoparticles linked
to aptamers (short, synthetic molecules of DNA) for cancer detetection. Their
work published in the journal Analytical Chemistry entitled "Gold
nanoparticle-based colorimetric assay for the direct detection of cancerous
cells", shows how the combination of these aptamers with gold nanoparticles
produces a diagnostic optical signal when they cover targeted cancer cells. This
could form the basis of a future cancer detection test.
Source World
Gold Council
For more information on this source please visit World
Gold Council