Research On Use of Gold in Anticancer Treatments
It is not widely known but radiactive gold was used in the treatment of cancer many years ago (see here for more details).Now a number of research groups around the world are using the unique properties of gold to develop new anticancer treatments.
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.