Iridium, the second most dense metal in the world, can kill cancer cells, filling them with a deadly version of oxygen, leaving healthy tissues intact. Discovered for the first time in 1803, the metal received its name from the Latin “rainbow”. Heavy, brittle and yellow metal comes from the same family as platinum, and is the most corrosion-resistant metal in the world.
Iridium is rare on Earth, but abounds in meteoroids. In the earth’s crust, a large amount of iridium was found that was 66 million years old, which led to the theory that it appeared on the planet together with an asteroid that led to the disappearance of dinosaurs.
Scientists have created a combination of iridium and organic material, which they target directly to cancer cells. The compound transfers energy to cells, converting the oxygen inside them into singlet oxygen, which is toxic and kills the cell, leaving healthy tissues unscathed.
“This project is a leap forward in understanding how these new iridium-based cancer-fighting compounds attack cancer cells, it presents various mechanisms of action that circumvent the problem of resistance and fight cancer from a different angle,” says co-author Kukson Chiu, Ph.D. in chemistry at the University of Warwick.
Laser illumination of the skin on the cancerous area triggers the process – it reaches the light-active coating on the joint and activates the metal, which begins to fill the cancer cells with singlet oxygen.
Photochemotherapy – the use of laser light to treat cancer – is rapidly developing as a viable, effective and non-invasive treatment. Patients are becoming more resistant to traditional methods of treatment, so it is very important to establish new ways such as to fight the disease.
The researchers found that after the attack by red laser light (which can penetrate deep under the skin) onto a simulated lung tumor that was grown in the laboratory, the activated organic-iridium component penetrated all layers of the tumor, killing it. This demonstrated how effective and far-reaching the treatment was.
Scientists have also proven that this method is safe for healthy cells by treating non-cancer tissue and discovering that it has remained unscathed.
“Our innovative approach to cancer control, including targeting important cell proteins, can lead to the emergence of new drugs with new mechanisms of action. This is extremely necessary, “says Pinyu Zhang, a chemist at the University of Warwick.
Scientists have used advanced mass spectrometry techniques to obtain an unprecedented appearance of individual proteins within cancer cells – and this enabled them to pinpoint which proteins were attacked by the organic-iridium compound.
After analyzing large amounts of data – thousands of proteins from simulated cancer cells – they came to the conclusion that the iridium compound damaged the key cancer molecules in proteins.
“Precious metal platinum is already used in more than 50% of cancer chemotherapy. The potential of other precious metals such as iridium is being explored to create new targeted drugs that will attack cancer cells otherwise and with minimal side effects, “says Peter Sadler, whose laboratory is at the Department of Chemistry at the University of Warwick. “It’s high time to find a medical application of iridium, which was delivered to us with an asteroid 66 million years ago.”