DNA nanobots deliver drugs in living cockroaches

By Sarah Spickernell

Nano-sized entities made of DNA that are able to perform the same kind of logic operations as a silicon-based computer have been introduced into a living animal.

The DNA computers – known as origami robots because they work by folding and unfolding strands of DNA – travel around the insect's body and interact with each other, as well as the insect's cells. When they uncurl, they can dispense drugs carried in their folds.

"DNA nanorobots could potentially carry out complex programs that could one day be used to diagnose or treat diseases with unprecedented sophistication," says Daniel Levner, a bioengineer at the Wyss Institute at Harvard University.

Levner and his colleagues at Bar Ilan University in Ramat-Gan, Israel, made the nanobots by exploiting the binding properties of DNA. When it meets a certain kind of protein, DNA unravels into two complementary strands. By creating particular sequences, the strands can be made to unravel on contact with specific molecules – say, those on a diseased cell. When the molecule unravels, out drops the package wrapped inside.

A bug's life The team has now injected various kinds of nanobots into cockroaches. Because the nanobots are labelled with fluorescent markers, the researchers can follow them and analyse how different robot combinations affect where substances are delivered. The team says the accuracy of delivery and control of the nanobots is equivalent to a computer system.

"This is the first time that biological therapy has been able to match how a computer processor works," says co-author Ido Bachelet of the Institute of Nanotechnology and Advanced Materials at Bar Ilan University.

"Unlike electronic devices, which are suitable for our watches, our cars or phones, we can use these robots in life domains, like a living cockroach," says Ángel Goñi Moreno of the National Center for Biotechnology in Madrid, Spain. "This opens the door for environmental or health applications."

DNA has already been used for storing large amounts of information and circuits for amplifying chemical signals, but these applications are rudimentary compared with the potential benefits of the origami robots.

Commodore cockroach The number of nanobots in the study – more than in previous experiments – makes it particularly promising, says Bachelet. "The higher the number of robots present, the more complex the decisions and actions that can be achieved. If you reach a certain threshold of capability, you can perform any kind of computation. In this case, we have gone past that threshold," he says.

The team says it should be possible to scale up the computing power in the cockroach to that of an 8-bit computer, equivalent to a Commodore 64 or Atari 800 from the 1980s. Goni-Moreno agrees that this is feasible. "The mechanism seems easy to scale up so the complexity of the computations will soon become higher," he says.

An obvious benefit of this technology would be cancer treatments, because these must be cell-specific and current treatments are not well-targeted. But a treatment like this in mammals must overcome the immune response triggered when a foreign object enters the body.

Bachelet is confident that the team can enhance the robots' stability so that they can survive in mammals. "There is no reason why preliminary trials on humans can't start within five years," he says.

Journal reference: Nature Nanotechnology, DOI: 10.1038/nnano.2014.58