White blood cells patrol your city's streets for viral threats? Actually, those are Israeli street artists.

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What's a DNA robot, and how could it change medicine?

Make no mistake: The human body is a war zone. What's more, it's a modern one, fought not on some away-game battlefield but right inside the war-torn city we call the human body.

Sure, our body's defensive forces do their part to keep the bulk of invaders out, but the enemy breached our gates a long time ago. So the struggle for health wages on inside us, amid delicate systems and crucial organs. The soldiers of our immune system fight viral spies, cancerous saboteurs, bacterial terrorists and parasitic war machines.

Modern science allows for a good bit of outside interference. Like a Cold War superpower propping up an embattled regime, we ship in our pharmaceutical weapons, high-tech surveillance equipment and the occasional blast of radioactive power.

Yet these superweapons are often far from clinical in their application.

Drop a bomb on a city block and you might wipe out enemy insurgents, but you'll also kill innocent civilians and decimate important infrastructure. You damage the very thing you aim to protect.

In the body, the situation is often the same. For example, we want to save the body from the ravages of cancer, but chemotherapy and radiation treatments damage the healthy cells, as well as the cancerous ones. What we need is something capable of making deadly accurate strikes at a cellular level -- a military drone to patrol our inner space.

Behold, the DNA robot. The purple fragments represent the antibody payload.

Image courtesy Campbell Strong, Shawn Douglas, and Gaël McGill

Hunting Cancer With DNA Robots

So what will hunt out the cancerous cells in our body and terminate them with minimal collateral damage? We'll need a robot -- one made out of DNA (deoxyribonucleic acid).

As you can tell from the illustration, the DNA robot doesn't look all that much like a typical bucket-of-bolts automaton. He has neither the charm of a WALL-E nor the deadly symmetry of a U.S. Air Force Predator Drone, but there's a very good reason. In order to build a robot at such a small scale, you have to build it out of small things. The material of choice in this machine is DNA itself.

DNA, of course, is the blueprint for most forms of organic life. The way you look, the way you think -- all of it's contained in a code of chemical bases. But DNA is more than just information. Since complementary sequences of DNA can bind together, individual molecules can self-assemble into complex shapes and structures. Develop a machine out of this stuff and you benefit from a building material that's both readily available and self-assembling. You'll save lives, and you'll also save research and development money.

Using a method called DNA origami, researchers at Harvard's Wyss Institute for Biologically Inspired Engineering folded strands of synthetic DNA into a barrel-shaped cage roughly 35 nanometers in diameter [source: Katsnelson]. By contrast, a strand of human hair is only 20,000 nanometers wide [source: EPA].

This cage holds up to 12 payload molecules inside it, such as cell-destroying antibodies [source: Katsnelson]. On the outside, two aptamers keep the cage from flying open and releasing the deadly payload. Aptamers are short DNA strands with special sequences for recognizing specific molecules. Think of them as locks holding the basket closed.

When the DNA robot comes in contact with targeted cancer cell, the locks spring open, the cage flies open and the antibody destroys the target cell. In 2012, the Wyss Institute research team reported "almost zero collateral damage" after releasing its bots on a mixture of target cells and bystander cells [source: Bachlet].

The technology promises to revolutionize health care with smart, targeted drugs and even more complex nanomachines to police our insides. Scientists have a number of hurdles to overcome as they fine-tune their DNA robot designs, however.

For starters, it currently takes weeks to fold together complex DNA structures. And if these nano-size hot pockets of destruction are to get any work done, it will help if we don't pee them out an hour later. Researchers are working on modifications to prevent the bot from hitting the kidneys or liver before it carries out its attack on targeted cells.

Still, the fact remains: We're building tiny robotic weapons to aid the endless war between the denizens of your body and the endless hordes that strive to conquer it. The technology, like the future, is here.

Senior Staff Writer Robert Lamb

HowStuffWorks 2009

Author's Note

I had to lash one hand behind my back to avoid making the obvious "Fantastic Voyage" or "Innerspace" references in this article. In a way, however, the films do the public understanding of nanotechnology -- especially medical nanotechnology -- a disservice. Visions of miniaturized submarines in the bloodstream display a top-down view of nanotechnology. In reality, we're looking at a bottom-up system, in which small machines are built of tiny materials to perform their work on an ever-so-minute scale. You don't build a sub the size of DNA; you build it OUT of DNA.

I couldn't help but think of the DNA robot concept in terms of a gift-wrapped package containing a small bomb. Imagine this package on the parlor of an Agatha Christie-style murder mystery. It will only open in the hands of a killer.

Sources

  • Danigelis, Alyssa. "DNA Robots Deliver Deadly Punch to Bad Cells." Discovery News. Feb. 16, 2012. (May 24, 2012) http://news.discovery.com/tech/dna-robot-nanotechnology-cancer-cells-120216.html
  • Katsnelson, Alla. "DNA robot could kill cancer cells." Nature. Feb 16, 2012. (May 24, 2012) http://www.nature.com/news/dna-robot-could-kill-cancer-cells-1.10047
  • Sanderson, Katherine. "Bioengineering: What to make with DNA origami." Nature. March 10, 2010. (May 24, 2012) http://www.nature.com/news/2010/100310/full/464158a.html
  • United States Environmental Protection Agency (EPA). "Nanotechnology 101." March 3, 2011. (May 24, 2012) http://www.epa.gov/nanoscience/basicinfo.htm