From science fiction to science fact
Published Monday January 12th, 2009
Research Tiny particles lead medicine to nanorobots fighting cancer
TORONTO - More than 40 years ago, the film Fantastic Voyage took moviegoers on a journey that was pure science fiction - a submarine and its crew were shrunk to the size of a cell and injected into the bloodstream of a dying scientist.
The mission was to navigate their way to his brain, where they would blast apart a soon-to-be-fatal blood clot and save his life.
While the premise of the movie was, well, fantastic, the notion of sending impossibly tiny fixers into the human body to cure what ails us is no longer just the stuff of imagination.
Around the world, billions of dollars are being poured into the burgeoning field of nanomedicine, the science of using molecular-scale technology to diagnose, treat and prevent disease.
At the heart of this technology is the nanoparticle, a speck of matter around which scientists are designing drug-delivery systems, quicker and more precise diagnostic tests and the building blocks for regenerating lost or damaged organs and limbs.
Technically, a nanoparticle is 100 nanometres or less, with one nanometre equal to one-billionth of a metre. To put that into perspective, think of particles so minuscule that a red blood cell that can only be seen through a microscope would dwarf them in size by at least 80 times. Or consider a human hair: its width is tens of thousands of times larger than a nanoparticle, as is the period at the end of this sentence.
Although the idea of injecting, let alone making, anything so incredibly diminutive may be difficult to wrap one's head around, scientists say we only have to look to our own bodies to grasp the concept.
Thomas Webster, an associate professor of engineering at Brown University in Providence, R.I., says that to peer at the intricacies of various tissues, such as bone or skin, through a super-powered microscope is to enter the nano world at a glance.
"What we're finding out is that nanomaterials make up our tissues," says Webster, editor-in-chief of the International Journal of Nanomedicine, who points as an example to enzymes and proteins that power the functions that give us life.
"So we are walking nano things. We are assembled from nanomaterials."
While nanomedicine is still in its infancy, its principles have already started being put into practice. Some drugs and devices have been approved for treating humans. One is a skin patch that incorporates infection-fighting silver oxide nanoparticles to promote faster wound healing. Another is a pin for mending fractures. It's made from microscopic bits of synthetic materials that mimic those found naturally in bone.
Liposomes - ultra-tiny sacs made from fats, or lipids, which transport drugs, vaccines and enzymes to targeted cells in the body - have been around for some time.
And when it comes to diagnosis, many Canadians may have been using nanotechnology without even realizing it. Some home pregnancy kits employ gold nanoparticles on their test sticks. It's the particles that change colour in response to a hormone present in the urine of pregnant women. But if nanomedicine's current applications are relatively few in number, that won't be the case for long, say scientists, who predict an explosion of advances in nano-based drug delivery, diagnostics and tissue regeneration over the next decade.
Warren Chan, a biomedical engineer at the University of Toronto, is experimenting with particles known as quantum dots, with the goal of improving cancer diagnosis. Smaller than a virus at under 100 nanometres in size, quantum dots emit light when their electrons are excited. The theory is that if a cancer-seeking protein is attached to the dots and they are injected into the body, they will accumulate in a tumour and give off different colours when exposed to light.
"So, for example, if you have breast cancer at stage zero, which is pretty healthy, you might have three blues, six greens, five reds," corresponding to various proteins in the cancer cells, explains Chan, who has successfully tested the system in lab mice.
A different colour profile from the lit-up dots - say 10 blue, one red and one green - would instantly show that the cancer has spread. "So by looking at the colour combinations, you would be able to identify the stage of the disease."
Chan's lab is also researching how quantum dots might be used to deliver chemotherapy directly to cancer cells, without harming healthy cells along the way.
Improving cancer treatment is a major goal of nanomedicine researchers around the globe, including internationally renowned biomedical engineer Robert Langer of the Massachusetts Institute of Technology.
Just how far can nanomedicine go?
Some visionaries predict that medicine will someday have a lot in common with the concept behind Fantastic Voyage. They see armies of infinitesimally minute machines moving throughout the body to repair and rejuvenate aging or damaged tissues.
As the theory goes, these medical nanorobots, kitted out with onboard computerized sensors and job-specific biomedical tools, would go about zapping tumours, cleaning up scar tissue and nibbling away at plaque-encrusted arteries to prevent heart attack and stroke.
For most mainstream researchers, the idea of nanorobots "knocking out the nasties" inside the body is still the stuff of Star Trek, suggests Neil Branda, a professor of organic materials at Simon Fraser University in B.C. and a founding director of the Nanomed Canada Research Network. "You say they're conceptual. I say they're delusional," scoffs Branda. "I'm not convinced that they're ever going to be around."
But even if such nano-devices were actually created some day, it would be their function that would matter, not their appearance. They're not going to look like a robot or an other ultra-miniaturized version of machines that exist on a macroscopic scale in our everyday world, he says.
"If you come into our lab, you're not going to see a little micron toaster popping up nano pieces of toast."
The "Tiny Matters" series continues next week.
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