DNA “cloaking devices” sneak past the immune system, could deliver medicine and identify disease

DNA nanobot
CREDIT: Wyss Institute

Scientists have used viruses as inspiration for “cages” built of DNA that effectively hide their cargo (e.g. medicine) from your immune system so that they can reach their target (e.g. a tumor) without setting off your body’s naturally hair-triggered intruder alarm.

A team at Harvard’s Wyss Institute for Biologically Inspired Engineering has built the first DNA nanodevices able to survive the mammalian immune system. This milestone comes hot on the heels of news of a working DNA nanodevice being deployed in live cockroaches. The projects are connected: the Wyss Institute collaborated with Bar Ilan University in Israel on the cockroach research. When the cockroach results were reported, the mammalian immune system was identified as a major hurdle in moving the DNA devices from cockroaches toward humans. Now only about two weeks later, it appears this hurdle has been crossed.

The Wyss Institute has a good press release on the subject, and a helpful video to go with it. It shows how DNA is folded, origami style, so that it not only carries a tiny piece of cargo but envelops it in a protective layer.

To fully understand the importance of the immune system in all this—after all, isn’t it supposed to help you fight disease, not get in the way of treatments?—it helps to know a bit more about how it works.

A roving gang of thugs

My parasitology professor once describe the human immune system as a gang of thugs roaming your body and spoiling for a fight. The best (i.e. worst) examples of this reality are the autoimmune diseases, like lupus, which occur when the immune system turns on normal healthy tissues.

The battle between your immune system and unwelcome invaders like parasitic single-celled organisms (malaria), viruses (HIV), and bacteria (strep throat) all hinges on an elaborate puzzle-matching game. Your immune cells “recognize” invaders by the unique structure of their outer surfaces. Once they’re recognized, the invaders are attacked. The immune system doesn’t know anything about the intent of a foreign particle in your body: if it’s foreign it’s getting flagged for destruction.

Some viruses, however, have a useful trick to avoid ever getting noticed in the first place. They grow a fatty layer around their outer shell that mimics the membranes of the rest of your cells. The scientists at the Wyss Institute did just this, using DNA molecules to mimic the virus’s mimicry.

The potential of DNA “nanorobots”

I’ve used the word “nanodevices” and “nanorobots” in this post, and both terms can be a bit confusing (if futuristic-sounding). Let’s strip off “nano” for now, for us it just means “very very small.” What “device” and “robot” means is that the DNA structures they’re using to create a cloak can be designed to do much more. They can be designed to carry out specific tasks, or chains of tasks, essentially acting like tiny robots or, in total, acting like a distributed computer. Cages built of DNA could ferry bits of medicine safely through your body to the precise location of a tumor, for instance, minimizing side-effects and maximizing effectiveness.

Ultimately, the researchers hope that the DNA bots could one-up the immune system in situations where it’s not cutting it. Consider cancerous tumors, which often escape the immune system’s ire because they comprised of your own cells gone rogue. They’re not foreign, but they are a problem. Using the same principles of recognition that allow the immune system to work, DNA nanorobots carrying medicine could both diagnose (i.e. recognize) a cancerous cell and deliver medicine to kill it in one fell swoop.

We’re still at least years away from human trials of similar robots—but the speed with which this technology went from cockroaches to mice provides hope that this particular bit of future-medicine will be here sooner rather than later.

Kenrick Vezina is Gene-ius Editor for the Genetic Literacy Project and a freelance science writer, educator, and naturalist based in the Greater Boston area.

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