The world’s second densest metal can be used to kill cancer cells by filling them with a deadly version of oxygen, without harming healthy tissue, according to a new paper.

The metal, iridium, was in the asteroid with the strongest link to the extinction of dinosaurs. When combined with organic material, the researchers showed it can be directly targeted towards cancerous cells, transferring energy to the cells to turn the oxygen (O2) inside them into singlet oxygen, which is poisonous and kills the cell - without harming any healthy tissue.

The process is triggered by shining visible laser light through the skin onto the cancerous area.  This reaches the light-reactive coating of the compound, and activates the metal to start filling the cancer with singlet oxygen. The researchers found that after attacking a model tumor of lung cancer cells, grown by the researchers in the laboratory to form a tumor-like sphere, with red laser light (which can penetrate deeply through the skin), the activated organic-iridium compound had penetrated and infused into every layer of the tumor to kill it.

Credit: University of Warwick/Mark Garlick

Their preliminary work also showed the method is safe to healthy cells by conducting the treatment on non-cancerous tissue and finding it had no effect.

The researchers concluded that the iridium compound damaged the proteins for heat shock stress, and glucose metabolism, both known as key molecules in cancer.

Citation: Dr. Pingyu Zhang, Cookson K. C. Chiu, Dr. Huaiyi Huang, Yuko P. Y. Lam, Dr. Abraha Habtemariam, Thomas Malcomson, Prof. Martin J. Paterson, Dr. Guy J. Clarkson, Prof. Peter B. O'Connor, Prof. Hui Chao, Prof. Peter J., ‘Organo-iridium photosensitizers can induce specific oxidative attack on proteins in cancer cells’ , Angewandte Chemie