By Alla Katsnelson of Nature magazine
DNA origami, a technique for making structures from DNA, may be more than just a cool design concept. It can also be used to build devices that can seek out and destroy living cells. [View a "DNA Origami" Slide Show.]
The nanorobots, as the researchers call them, use a similar system to cells in the immune system to engage with receptors on the outside of cells.
"We call it a nanorobot because it is capable of some robotic tasks," says Ido Bachelet, a postdoctoral fellow at Harvard Medical School in Boston, Massachusetts, and one of the authors of the study, which is published in the February 17 issue of Science. Once the device recognizes a cell, he explains, it automatically changes its shape and delivers its cargo.
The researchers designed the structure of the nanorobots using open-source software, called Cadnano, developed by one of the authors--Shawn Douglas, a biophysicist at Harvard's Wyss Institute for Biologically Inspired Engineering. They then built the bots using DNA origami. The barrel-shaped devices, each about 35 nanometers in diameter, contain 12 sites on the inside for attaching payload molecules and two positions on the outside for attaching aptamers, short nucleotide strands with special sequences for recognizing molecules on the target cell. The aptamers act as clasps: once both have found their target, they spring open the device to release the payload.
"You can think about it as a sort of combination lock," says Bachelet. "Only when both markers are in place, can the entire robot open."
The researchers tested six combinations of aptamer locks, each of which were designed to target different types of cancer cells in culture. Those designed to hit a leukemia cell could pick that cell out of a mixture of cell types then release their payload--in this case, an antibody--to stop the cells from growing. They also tested payloads that could activate the immune system.
The work "takes us one more step along the path from the smartest drugs of today to the kind of medical nanobots we might imagine," says Paul Rothemund, a computational bioengineer at the California Institute of Technology in Pasadena, and inventor of DNA origami.
Right on target
Because the nanorobots can be programmed to release their payload only when the target cell is in the correct disease state, they achieve a specificity that other drug-delivery methods lack, says Hao Yan, a chemist and nanotechnologist at Arizona State University in Tempe. "This really takes advantage of the programmability of DNA nanotechnology."
Whether or not these structures will work in a living organism remains to be seen. For one thing, they are designed to communicate with molecules on a cell's surface. "If your therapeutic target is inside the cell, it's going to be tricky," says Bachelet.
What's more, the nanorobots are quickly cleared by the liver or destroyed by nucleases, enzymes chew up stray bits of DNA. It might be possible to coat them with a substance such as polyethylene glycol, widely used to boost the length of time a drug can remain in the body, says Douglas, or "maybe to borrow inspiration from other biomolecules or cells"--such as red blood cells--"that can circulate in the blood for a long time". He and his colleagues are just beginning to think about testing the nanobots in mice, he says.
"If these sorts of problems can be solved, then the nanorobots have a chance at becoming real therapeutics," Rothemund says.
This article is reproduced with permission from the magazine Nature. The article was first published on February 16, 2012.
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Reply | Report Abuse | Link to thisSingularity here we come! I do like the idea of a DNA or viral based delivery system over a pure nanobot solution personally.
"We call it a nanorobot because it is capable of some robotic tasks." In that light, all DNA should be considered what - megananorobots?
Reply | Report Abuse | Link to thisIn situ effectiveness is crucial for any real usefulness and may be very difficult to achieve. Perhaps integrating the programmed DNA snippets into host cellular DNA might be necessary for persistence...
If one can design nanobots to kill cancer cells, presumably one can also design nanobots to kill normal cells. Thus one could design potent poisons. One can envision poisons which are species-specific, poisons which target broader categories of living things, and poisons which target specific types of normal cells, e.g., neurotoxins, cardiac toxins, skeletal muscles toxins, liver toxins, etc. It would seem that the potential destructive uses of this technology are at least as great as the therapeutic uses.
Reply | Report Abuse | Link to this@jtdwyer - the article says 35 nanometers in Dia, And it sounds like what is discussed is a delivery system and does not include what would be considered the software/logic unit or brains of the "bot". So it sounds to me the description that fits this delivery system best is: "Genetically Engineered Nano Virus". Since viruses can contain DNA to the extent that - "Viruses use tRNA or mRNA or DNA as a tool for infecting host cells, but they they do not use either for their own internal bio-mechanics"
Reply | Report Abuse | Link to thisso I guess I lean towards the definition of a "nano-robot" as being entirely of synthetic, futuristically speaking like a smart phone scaled down to the nano level.
@bigbopper - right off the bat it does seem to me too that these nano-viruses could be more dangerous than nano-bots since they can be made very easily with out a "kill switch" which all nanobots would presumably respond to (at worst case by a very large induced E&M field that would fry nano-bot circuitry). However, I don't see the nano-viral cell docking station/delivery technology discussed above as being very pheasible in the middle term future with out having a non-bot for the CPU - which means even these DNA based nano's for many years to come will very likely respond to short circuiting via a large induced field. Though yes in the short term a one/few keyed nano-viral, that delivered parhaps only one "chemical" to a particular cell opening could be of worry in the short term, is a problem I feel we can over come pretty quickly since afterall it is directed treatment that is the middle and long term goals here. IMO.
The possibilities are endless. IT would be great to see this applied to HIV/AIDS infected cells. Maybe reprogram them?
Reply | Report Abuse | Link to thisHopefully this is the magic that we have been hoping for in our search to cure cancer!
Reply | Report Abuse | Link to thisThe government has no intention of allowing a cure for cancer
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