Precious Metals vs Cancer: Platinum, Gold, and Silver

Platinum was the first precious metal to achieve recognition as an effective cancer therapy:

The first platinum based chemotherapy drug discovered by researchers was cisplatin, which forty years later continues to have applications in certain types of cancer. In that time, scientists have searched for ways to improve the anti-tumor efficacy of platinum based drugs, reducing the toxicity profile, and strengthening them against resistance by expanding the class to include several new analogues of cisplatin and putting them through clinical trials to broaden the different types of cancers against which they can be safely used. _Source

Gold has more recently been recognised to have utility in fighting cancer. Gold is being used to help locate tumours and cancer cells for radiation treatment, and is also being used in drug complexes, for its cytotoxic properties.

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. _AzoNano

Even more recently, silver is being seen as a potentially effective anti-cancer material.

Previous studies have hinted that silver compounds could also kill cancer cells. So Charlotte Willans from the University of Leeds, UK, and colleagues subjected silver to the same treatment as platinum to see if they could make an effective cancer drug.

The team attached different types of carbene ligands to the silver atoms before incubating varying concentrations of the compound with breast and colon cancer cells for six days.

The silver complexes proved to be as effective as cisplatin in attacking both types of cancer cells. Complexes containing a ligand which had two bonds were more effective than those with a single bond, probably because they are more stable - meaning the compound breaks down more slowly and is active for longer (Dalton Transactions, DOI: 10.1039/C2DT12399A).

Crucially, silver is less toxic to normal cells than platinum. Willans says it is an important step in the quest for effective, non-toxic cancer treatments. _NewScientist

More on the use of silver to treat cancer

The use of precious metals to treat cancer is one more reason to value them for their intrinsic worth. In developed societies, cancer is responsible for more lost years of life than virtually any other disease.