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The scientists on the front lines are skeptical.
"An assembler will require some molecular scale intelligence," says Shuming Nie, an adjunct professor of molecular biology at Emory. "I'm not betting my career on that type of thing."
Mostafa El-Sayed, who studies the properties of nanoparticles at Georgia Tech, smiles.
"The surface of these small particles is so unstable. How do we stabilize them? We have to develop the theoretical tools. There is a lot of science. Nothing is impossible. The question is, how can I live in this small world and work with it?"
Gang Bao's work represents both the potential and the problems with nanotechnology. A mathematician by training, Bao is a soft-spoken academic who for eight years taught at Johns Hopkins University and worked on Department of Defense contracts, helping to design stronger materials for fighter plane engines.
But several years ago, after four of his post-doctorate advisers were diagnosed with cancer, Bao made a career change. He took a year's sabbatical and learned molecular biology, which is to say he read textbooks that could double as doorstops.
"The DOD work is important for defense, but you don't really see the end product," says Bao, who came to Georgia Tech in 1999 as an associate professor of biomedical engineering. "But in biomedical research, you know that if what you develop, if that works, you can really save lives."
In one sense, Bao's visions are almost Drexlerian. He works with molecular beacons, specially engineered to release a fluorescent signal when they encounter tumor markers within cancer cells. He imagines the beacons zooming through the bloodstream toward the cancer cells. Once it shows up at the cancer cell's door, the beacon not only signals that it's found a target, but it takes out the target. It would work like a smart bomb, killing only the cancer cell and leaving the healthy ones untouched. Chemotherapy would be obsolete. Even cancer itself could be nothing more than an annoyance that's quickly taken care of.
The question, of course, is when. Bao is making tremendous, essential strides, but he's a bit like the Wright Brothers tinkering with the first plane; space travel is decades down the road.
The real test of Bao's work will come during clinical studies, which could be years away. In the meantime, the molecular beacons he's working with must do four things in the lab first -- deliver the beacons to the cell, target the cancer cells, signal that the target has been spotted, and, finally, destroy the cancer cell.
So far, Bao's team has found ways in the lab to target the cancer cells and release the fluorescence. But even that needs refining. Bao must ensure the beacons don't glow when they encounter a healthy cell. And right now, Bao and his team inject the beacons directly into the cells in the lab; human applications would likely require the nanoprobes seek out and enter only those cells that are cancerous. Finally, researchers have to figure out a way to deliver the beacons deep into human tissue, and also propel them through the bloodstream.
"Let's say you make a nanomachine," Bao says. "There's a lot of moving parts. How do you drive that? Now, I don't think you can use batteries. A battery would be huge compared to a nanodevice. In my view, in order to drive those devices, we need to use bio-motors."
Bao believes the beacons could be propelled by absorbing energy from the body's own enzymes. But that, too, is research that lies ahead.
Working in concert with Bao is Nie, the Emory professor who also last September was named by Gov. Roy Barnes as one of the Georgia Cancer Coalition's first distinguished cancer scientists. Nie has injected nanoparticles into mice, just to see how the animals react.
"They take these things very efficiently," Nie says of the mice. "For example, we inject some of these in a tail of a rat and we find these particles [end up] in the spinal cord of the rat, and the brain. So they move around. They move around very efficiently within the body. We also injected high dosages into the animal, a very high concentration, about 100 or 1,000 times more than what you would normally use. We thought it would kill the animal. So far, the animal is very healthy. Everything's fine."
In a few weeks, Nie says, the animal will be sacrificed so researchers can determine where in the body the nanoparticles accumulated.
Nie also is working on ways to use nanoparticles to identify different protein and nucleic acid sequences in the body. In that way, you could have your blood tested to determine what drugs -- and in what amounts -- would work best for different ailments. Prescriptions would be tailor-made, taking the guesswork out of dispensing medicine.
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