Robots one-thousandth the width of a human hair are now able to fight cancer by destroying tumours in the body.
Scientists have built nano-robots from DNA sheets shaped into tubes and injected into the bloodstream.
The tubes carry a blood-clotting enzyme, thrombin, and are painted with proteins which home in on a separate protein found only in tumour cells.
When the robots reach their target and bind to its surface they spring open and deliver the enzyme which clots the blood supply to the tumour and causes it to have a mini heart attack and die. The nanorobots work fast, congregating in large numbers to surround a tumour just hours after injection.
They were found to be safe in tests on mice and pigs, with no evidence of spreading to the brain where they could cause a stroke. The treatment blocked tumour blood supply and generated tumour tissue damage within 24 hours, while having no effect on healthy tissue.