The treatment blocked blood supply to the tumour and generated tumour tissue damage within 24 hours while having no effect on healthy tissues. That sheet was then loaded with an enzyme called thrombin - a chemical that can clot blood - and the sheet was then rolled into a tube, with the thrombin kept protected inside.
Researchers at the Arizona State University and the National Center for Nanoscience and Technology of the Chinese Academy of Sciences, led by Molecular Sciences Professor Hao Yan, published the biotech journal Nature Biotechnology.
To test their nanorobots, the researchers injected them into mice infected with human breast cancer cells and human ovarian cancer cells as well as mouse models of human melanoma and lung cancer. Using targeted drugs is also not as exact as simply cutting off blood supply and killing the cancer on the spot. Then, they used DNA fasteners to join the long edges of the rectangle, resulting in a tubular nanorobot with thrombin on the inside. The researchers attached parts of DNA found in tumor cells to the nanorobots, and once they come into contact with tumor cells, they attach and release their payload. Further analyses showed that nanorobot administration led to blood vessel occlusion in the tumors within just 24 hours; by 48 hours there was advanced thrombosis, and by 72 hours dense thrombi were evident in all the tumor vessels. Once the tumor was growing, the nanorobots - which are a thousand times smaller than a strand of human hair - were deployed.
The team also carried out extensive safety studies in two different mammals, including the Bama miniature pig, which is physiologically and anatomically very similar to humans. The sheets of DNA used, which are 90 nanometres by 60 nanometres, deliver an enzyme direct to the blood vessels at the heart of the tumour. The nanorobot therapy was particularly effective in a melanoma mouse model, in which three of eight treated mice showed complete tumor regression and more than double median survival time.
Nanomedicine is a new branch of medicine that seeks to combine the promise of nanotechnology to open up entirely new avenues for treatments, such as making minuscule, molecule-sized nanoparticles to diagnose and treat hard diseases, especially cancer.
"The thrombin delivery DNA nanorobot constitutes a major advance in the application of DNA nanotechnology for cancer therapy", said Yan.
Starved of their blood supply, tumours began to shrink and the cancer's ability to spread and grow in new sites also appeared to be reduced, doubling the life expectancy or removing tumours entirely in some mouse cancers. But the results of this new study are promising - Yan and the research team are now hoping to pursue clinical testing.