Honey, I Shrunk the HMO!

GO TO: 2081 NANOMEDICINE In his 1986 nanofuturism bible, Engines of Creation, K. Eric Drexler describes a world in which invisible machines replace factories and assemble everything – from minivans to microchips – atom by atom and molecule by molecule. In later musings, he tells of tiny nanobots – always connected, watching our every move, […]

GO TO: 2081 NANOMEDICINE

In his 1986 nanofuturism bible, Engines of Creation, K. Eric Drexler describes a world in which invisible machines replace factories and assemble everything - from minivans to microchips - atom by atom and molecule by molecule. In later musings, he tells of tiny nanobots - always connected, watching our every move, continuously chatting with a planetary meganetwork, freely roaming our global meatspace.

Drexler's nanoscape also includes swarms of microscopic nanomedical devices that fix living cells and deliver medicine, cruising our collective bloodstream in search of rogue viruses and killer cancers. It's here that some of Drexler's radical technologies are beginning to materialize.

In September, biological engineers Carlo Montemagno and George Bachand devised the first self-propelled nanobot. The Cornell University scientists genetically tweaked an F1-ATPase protein (part of an enzyme that produces energy in all living cells by transforming adenosine diphosphate into its triphosphate form), then attached one end of their mutant micromachine to a metallic substrate and affixed the chemical equivalent of a propeller to the other. As the ATP began to break down, the bio-motor - 100,000 times smaller than a grain of sand - started to move, and ran for 40 minutes before it was shut off.

Once the engine is outfitted with a compartment for storing antibiotics, the device could be a "pharmacy in a cell," says Montemagno. "The motor can then be used as a pump to deliver the drug dosages to targeted areas."

Of course, setting loose such creatures in a human body to kill off menacing biobugs is still years away. Yet this work brings us a lot closer to Drexler's autonomous, atomic-scale bots. And in the past year, similar biomedical nanomachines have begun showing up in several R&D labs.

Nanomat, a startup in Dublin, Ireland, has figured out how to bind nanocrystals of various drugs with a substance that can seek out human tissue in specific organs. Instead of flooding the bloodstream, such discriminating microtools could target the precise part of the body that's ailing, thus avoiding dangerous side effects of less focused drug-delivery systems.

"It's the biomolecular equivalent of love at first sight," says Donald Fitzmaurice, a chemistry professor at University College Dublin who launched Nanomat in 1997. Taking a cue from Mother Nature, Nanomat's smart drugs are fashioned to act much like our bodies' antigens, which bond with complementary proteins to stimulate chemical reactions.

Fitzmaurice says it may soon be possible to coat penicillin nanocrystals in biotin, an antigen that binds with proteins that regulate cell growth in the bacteria streptavidin, to attack disease at the molecular level. Likewise, nanoparticles could be designed to cling to lung tissue. Inject them into a patient's chest and you get dazzling high-res X rays to detect very-early-stage lung cancer.

In Richardson, Texas, a company called Zyvex is trying to build the first nanotech assembler, a machine capable of building any material - gold, diamonds, even wood - by stacking atoms in just the right formations.

Zyvex is the first to admit that its alchemy endgame is a long way off. So far, the company has been able to pick up individual atoms and move them using a scanning tunneling microscope, a relative of the atomic-force microscope. Getting the atoms to actually stick together will be the next big feat.

Eventually, though, Zyvex's assembler will have an onboard computer and nanomanipulators; once the first molecule is built by hand, the assembler will be able to mimic the process. This will let engineers fashion miniature assembly lines for mass-producing some of the first bots made out of the nanotech building block, the carbon nanotube.

One ten-thousandth the diameter of a human hair, carbon nanotubes are one-sixth the mass and 100 times the strength of steel, and capable of carrying electrical current. NASA scientists have already mixed carbon nanotubes with polymer-based plastics to build superlightweight space-shuttle components. And last year, Cees Dekker, a Dutch scientist at the Delft University of Technology, created the first carbon-nanotube transistor - a giant leap forward in the evolution of single-molecule electronics.

In January 1999, Lawrence Berkeley National Laboratory stunned nanogroupies everywhere when a team led by physicist Alex Zettl proclaimed it had built a working diode on the molecular scale. Zettl quickly pulled back, stating nanotube conductors (and his diode, by association) suffer from "large noise," which foils electrical transmissions. But as it turns out, Zettl says, the noise is most disruptive at low frequencies, which means it won't impede the high-speed transmissions used by many digital devices.

Tiny sheets of hexagonal carbon atoms will provide the foundation for a range of molecular-scale biomedical sensors, says Ralph Merkle, who recently left his research post at Xerox PARC to join Zyvex as a principal fellow. "We know that carbon nanotubes are enormously strong, and we know that we can compress gases such as oxygen," he says. "So we could build tiny, spherical, synthetic red blood cells programmed to selectively release oxygen and collect CO2 from the bloodstream." Synthetic cells let loose in the body during a heart attack would give the sufferer more time to get to the emergency room. "Or," Merkle says, "it would mean you could hold your breath for a very long time."

Currently, Merkle - who is also an executive editor at the Journal of Nanotechnology and winner of a 1998 Feynman Prize in nanotech - is exploring ways not only to build nanomachines but to get those devices to produce other nanomachines that would become part of a system for inexpensively fabricating just about anything. Synthetic cells would be one of the more straightforward apps. Someday your yearly checkup will show up in the mail as a syringe filled with smart serum. Inject it and suddenly thousands of nanodoctors will stream through your muscles and organs, acting like intelligent engine-cleaner - eating cancers, removing gallstones, and carrying out minor internal surgeries.

"One imagines tiny machines that can detect AIDS or tuberculosis and can alert colleagues capable of destroying these illnesses,"says Deepak Srivastava, a senior research scientist in the computational-nanotechnology group at NASA Ames Research Center, who studies molecular electronic devices, including nanotransistors, nanoswitches, nanogears, and nanomotors. Adds Srivastava, "It will be the birth of true preventive medicine."

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