Detailing their findings in a study published on 12 February in the journal Nature Biotechnology, an international group of researchers had introduced a DNA nanorobot capable of traveling in the bloodstream and delivering a deathly payload to malignant tumours.
“It’s a combination of diagnosing the bio-markers on the surface of the cancer itself and also, upon recognising that, delivering the specific drug to be able to treat it,” said Suresh Neethirajan of the University of Guelph in Ontario, Canada who was not involved in the study.
Targeting cancer cells with microscopic robot-like machinery has been the holy grail of oncological research for decades, and this is one of the first demonstrations of how such an approach could work in a living organism.
First, the researchers, led by Hao Yan of Arizona State University, developed a self-assembling, rectangular sheet of origami DNA which they infused with a blood-clotting enzyme called thrombin.
Next, the research team engineered a set of DNA fasteners to dissociate upon contact with nucleolin – a protein specific to the surface of tumour blood-vessel cells – and used them to seal the long edges of the rectangle design, resulting in a tubular nanorobot with thrombin on the inside.
As part of a test, the researchers then injected the manufactured nanorobots intravenously into nude mice with human breast cancer tumours. Within 48 hours, the ‘bots successfully discharged the thrombin payload onto the target vessels, causing them to clot, and eventually leading to necrosis of the relevant tissue.
Further experiments also demonstrated the efficacy of the tiny robots in targeting a mouse model of melanoma, and increasing the survival rate of mice with xenografts of human ovarian cancer cells.
The researchers had even shown their invention to be completely benign to the major tissues of miniature pigs, thereby jumping the first hoop towards the clinical approval of the technique in human subjects.
The next step for the research team will be to determine how much thrombin is actually delivered during treatment, and make sure no previously undetected damage is caused to the host organism.
While the step from a mouse model to humans is a major one, even in the event of failure, the medical research community is likely to find other uses for the platform worked out by Yan and his colleagues.