In a major advancement in nanomedicine, an international team of scientists has successfully programmed nanorobots for the first time in mammals, that potentially shrinks tumours by cutting off their blood supply.

Each nanorobot is made from a flat, rectangular DNA origami sheet that is 90 nanometres by 60 nanometres in size. Once bound to the tumour blood vessel surface, the nanorobot was programmed to deliver its unsuspecting drug cargo in the very heart of the tumour, exposing an enzyme called thrombin that is key to blood clotting. The nanorobots worked fast, congregating in large numbers to quickly surround the tumour just hours after injection.

"We have developed the first fully autonomous, DNA robotic system for a very precise drug design and targeted cancer therapy," said Hao Yan, Professor and Director at Arizona State University. The treatment blocked blood supply to the tumour and generated tumour tissue damage within 24 hours while having no effect on healthy tissues. After attacking tumours, most of the nanorobots were cleared and degraded from the body after 24 hours.

The median survival time is more than doubled, extending from 20.5 to 45 days. "Moreover, this technology is a strategy that can be used for many types of cancer, since all solid tumour-feeding blood vessels are essentially the same," Yan added, in a paper published in the journal Nature Biotechnology. Until now, the challenge to advancing nanomedicine has been difficult because scientists wanted to design, build and carefully control nanorobots to actively seek and destroy cancerous tumours, while not harming any healthy cells.

However, the new "nanorobots can be programmed to transport molecular payloads and cause on-site tumour blood supply blockages, which can lead to tissue death and shrink the tumour", explained Baoquan Ding, Professor at the National Centre for Nanoscience and Technology (NCNST) in China. For the study, the team used a melanoma mouse model, where the nanorobot not only affected the primary tumour but also prevented the formation of metastasis, showing promising therapeutic potential.

Importantly, the nanorobots were found safe and effective in shrinking tumours and there was no evidence of the nanorobots spreading into the brain where it could cause unwanted side-effects, such as a stroke. "The thrombin delivery DNA nanorobot constitutes a major advance in the application of DNA nanotechnology for cancer therapy," Yan said.