12 April 2014, 19:46

US, Israeli researchers test DNA nano robots on insects

US, Israeli researchers test DNA nano robots on insects

DNA nano robots could one day carry out complex computer programs in the human body, according to a paper in Nature Nanotechnology.In their new study, Israeli and American researchers successfully deployed DNA nano robots in living cockroaches and used those nanobots to release an antibody that recognizes the insect's hemocytes, which are analogous to human white blood cells.

The tiny robots, also known as origami robots due to their ability to fold and unfold their DNA strands to release medicinal molecules held within, can be programmed to release their packages upon contact with certain other molecules – such as those of a diseased cell.

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

The scientists have marked the tiny robots with fluorescent material, enabling them to track their movements and actions inside the cockroaches’ bodies.

They observations have shown that DNA nanorobots could potentially carry out complex programs that could one day be used to diagnose or treat diseases with unprecedented sophistication,” study co-author Daniel Levner of Harvard University told New Scientist this week.

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. When the molecule unravels, out drops the package wrapped inside.

The robots are made of biological material – custom-made DNA, which is ideal for such purposes as it can store large amounts of information. Different DNA sequences dictate different actions and reactions in the nanorobots.

By designing a DNA sequence just right, scientists can get the resulting floppy strand to stick to itself and bend into just about any shape they desire.

"The original application that motivated this work is cancer therapy," says Daniel Levner, an expert in bioengineering at the Wyss Institute at Harvard University. "The problem with many current cancer therapy drugs is that they are not very targeted. Some kill any cell trying to divide, and since cancer cells divide more frequently, they are affected the most. But other cells divide too, like the ones in hair follicles, which is why hair falls out during chemotherapy. Scientists would like to develop therapies that recognize and kill only cancer cells."

The logic might be hard to decipher, but the importance is not: "We can get these nano robots to perform all kinds of complex tasks that simple drugs can't—we can potentially get them to carry out complex programs," Levner said.

"This is a huge step forward," says molecular technologist George Church of Harvard University, who did not take part in this research. "This is the first time DNA-based computing was used in a living animal. This is also a great step forward to complex DNA-based computing systems."

Still, there are problems standing in the way of using DNA nanobots in humans. One reason Levner's team did these tests with cockroaches is because their bodily fluids are low in nucleases, enzymes that break apart DNA. "Cockroaches make for a good system for the initial testing of DNA-origami-based technologies in living animals," Levner says. By contrast, the bodily fluids of mice, humans, and other mammals are much higher in nucleases, which helps fight infections, but poses a problem in using DNA robots in therapies.

However, a number of potential solutions exist to protect DNA robots in the human body. For instance, scientists might encapsulate the DNA robots in structures that protect them, attach chemicals that make the DNA more difficult to cleave, or even replace the DNA with molecules known as LNA that are similar to DNA but more resistant to attack, Levner says.

"There is more to be done before DNA nano robots could be used to treat human disease," Levner says. "However, seeing the nano robots perform a complex task within a living animal is a very important step in that direction, a result which we hope will motivate additional work towards this goal."

And as for fears that DNA nanobots will become self-aware and malevolent, Levner says not to worry.

"A concern for some readers may be an association with the evil nano robots of sci-fi, which go on to take over the world," Levner says. "The DNA origami robots that we developed are not at all able to replicate themselves and could never pose the sci-fi threat. The DNA in our nano robots is a powerful building block, but otherwise it is no different than any other synthesized drug molecule."

It's a computer – inside a cockroach. 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 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.

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.

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