Scientists have developed nanorobots that can shrink tumors by cutting off their blood supply.
Researchers from Arizona State University and the Chinese Academy of Sciences’ National Center for Nanoscience and Technology tested the nanorobots in mice. The animals had been injected with human cells that prompt cancer tumors to grow quickly.
The nanorobots are made from tiny, flexible sheets of DNA, called DNA origami sheets. These are treated with thrombin, an enzyme that triggers blood to clot in the body. Scientists then fold the flat sheet in on itself, creating a tube that has the thrombin on the inside.
A specific molecule that naturally binds to nucleolin, a protein that is only found on the surface of the cells that make up a cancer tumor, is then attached to the outside of the tube.
Once inside the body, the nanorobot travels through the blood stream, and when the molecule on the outside of it finds nucleolin, the whole structure binds to it. Once attached to the tumor, the tube unfurls, releasing the thrombin. This makes the blood in the blood vessels leading into the tumor clot. The result is a thrombosis, or blockage, that stops blood feeding into the tumor. Deprived of nutrients, the tumor suffers damage.
The team tested the method in breast cancer, melanoma, ovarian cancer and lung cancer mouse models.
The nanorobots collected in large numbers, surrounding the tumors in hours. They blocked the blood supply and caused damage to the tumor within 24 hours but had no effect on the body’s healthy cells. Within 24 hours of attacking the tumor, the nanorobots were cleared from the body.
By day two, researchers found evidence of advanced thrombosis and by day three, they found blood clots in all of blood vessels feeding the tumors.
In three of the eight mice with melanoma, the tumors were completely killed, and the average survival time more than doubled, from 20.5 to 45 days.
In a mouse with lung cancer, the team was able to shrink the tumor tissue in two weeks.
There was no evidence that the nanorobots spread into the brain, where they could cause a stroke (a blood clot in the brain).
The results of this first-of-its-kind study have implications for the treatment of cancers across the spectrum.
The team, which has been working on the technology for five years, said it could lead to the ultimate goal of cancer research – the eradication of tumors.
“We have developed the first fully autonomous, DNA robotic system for a very precise drug design and targeted cancer therapy,” said Hao Yan, director of the ASU Biodesign Institute’s Center for Molecular Design and Biomimetics and the Milton Glick Professor in the School of Molecular Sciences.
“Moreover, this technology is a strategy that can be used for many types of cancer, since all solid tumor-feeding blood vessels are essentially the same.”
He went on to say that the study represented the “end of the beginning” for nanomedicine and that the industry was much closer to real, practical medical applications for the technology.
He said: “The… nanorobot constitutes a major advance in the application of DNA nanotechnology for cancer therapy.
“In a melanoma mouse model, the nanorobot not only affected the primary tumor but also prevented the formation of metastasis (secondary cancers), showing promising therapeutic potential.”
What’s more, the method could also be developed to deliver treatments for other diseases, by modifying how the nanorobots are built, the substances they carry and what they target.
Arizona State University (2018). Cancer-fighting nanorobots programmed to seek and destroy tumors. (2018, February 12). Available from: https://biodesign.asu.edu/news/cancer-fighting-nanorobots-programmed-seek-and-destroy-tumors (accessed February 2018).