Cancer cells can be targeted and destroyed using a metal from the asteroid that killed the dinosaurs without harming healthy tissue, according to new research.
An international team of researchers from the University of Warwick and Sun Yat-Sen University in China has shown that iridium – the second most dense metal on Earth – can be used to kill cancer cells by filling them up with a poisonous version of oxygen.
The scientists created a compound of iridium and other organic materials that could be directly targeted towards cancerous cells. When the compound reaches the cells it turns the oxygen inside them into a high-energy form of the element called singlet oxygen, which is toxic to the cancer cells.
This process is triggered by shining a visible laser light, which can penetrate through the skin, onto the cancerous area. The light reacts with the iridium compound, activating the metal and causing the singlet oxygen to form.
In the study, published in the journal Angewandte Chemie, the team used a model tumour of lung cancer cells that was grown in the lab. Using the technique, they found that the iridium compound had penetrated into every layer of the tumour, demonstrating the treatment's effectiveness. When they conducted the same experiment on healthy cells, they found it had no effect.
"The precious metal platinum is already used in more than 50% of cancer chemotherapies," said Peter Sadler from the University of Warwick. "The potential of other precious metals such as iridium to provide new targeted drugs which attack cancer cells in completely new ways and combat resistance, and which can be used safely with the minimum of side-effects, is now being explored."
"International collaborations can greatly hasten progress. It's certainly now time to try to make good medical use of the iridium delivered to us by an asteroid 66 million years ago!"
Using light to target cancer – a technique known as photochemotherapy – is fast becoming a viable, effective and non-invasive treatment. Many patients are becoming increasingly resistant to traditional cancer therapies, so alternative treatment methods such as this could have an important role to play in the immediate future.
Iridium is a hard, yellow, brittle metal that was first discovered in 1803 and is in the same family as platinum. It is the most corrosion resistant metal in the world and has a melting point of more than 2400° Celsius.
Iridium is very rare on Earth but is abundant in meteoroids. Large quantities have been found in the Earth's crust from around 66 million years ago, leading scientists to suggest that Iridium came to this planet on the asteroid that caused the extinction of the dinosaurs.