Scientists at the Indian Institute of Science, Bangalore have found a novel way to kill cancerous cells by using iron-based compounds “decorated” with organic groups. Red light acts as a switch that turns these compounds on and off. Like a Trojan horse, the organic molecule directs the compound into the mitochondria of the cancerous cells, and the light-sensitive iron-based compound (inorganic iron (III) catecholates) generates reactive oxygen species when exposed to red light. The reactive oxygen species so generated destroy the mitochondria thus killing the cancerous cells. The results, based on in vitro studies, were published recently in the European Journal of Inorganic Chemistry.
“Red light is used because the longer wavelength enables it to penetrate the skin deeper,” said Prof. Akhil Chakravarty from the Department of Inorganic and Physical Chemistry. “Normal cells don’t allow the compound to get in but cancerous cells do and we have taken advantage of this.”
The reason for targeting mitochondria is because unlike nuclear DNA that repairs itself when damaged by drugs, mitochondria have no repair mechanism. So cells die once the mitochondria are damaged. According to the paper, mitochondrial dysfunction is implicated in tumorigenesis and thereby makes it a popular target for the development of various cytotoxins.
“We saw very good activity. Almost all cancerous cells were destroyed when red light was used. We have to next undertake studies in animals,” he said. Cancerous cells from the cervix, lung and skin were tested. Since the procedure relies on the ability of the red light to penetrate the skin, only certain cancers can be targeted. “We are mainly bothered about oral cancer and skin cancer. Using endoscopy and colonoscopy we can take red light inside the body and achieve similar results,” he said sounding very optimistic.
“Photodynamic therapy (PDT) is a relatively new mode of cancer treatment, which depends on the retention of the photosensitizers in the tumour cells followed by their selective activation under red light in the presence of molecular oxygen. Photosensitizers are light-sensitive compounds that cause localized oxidative damage within the target cells upon irradiation,” notes the paper.