The project involves magnetized nanoparticles that are coated with carbon and studded with antibodies specific to the molecules the researchers want to purge from the blood: inflammatory proteins such as interleukins, or harmful metals like lead, for example. By adding the nanomagnets to blood, then running the blood through a dialysis machine or similar device, the researchers can filter out the unwanted compounds.
"The nanomagnets capture the target substances, and right before the nanoparticles would be recirculated, the magnetic separator accumulates the toxin-loaded nanomagnets in a reservoir and keeps them separated from the recirculating blood," explains Inge Herrmann, a chemical engineer at the University of Zurich who is leading the work.
According a study published in the journal Nephrology Dialysis and Transplantation in February 2011, the researchers were able to remove 75 percent of digoxin, a heart drug that can prove fatal if given in too high a dose, in a single pass through a blood-filtration device. After an hour and a half of cleansing, the nanomagnets had removed 90 percent of the digoxin.
One big caveat is that the researchers must demonstrate that the particles aren't toxic to the body and won't interfere with the blood's ability to clot. But early results are promising. In a 2011 paper in Nanomedicine, Herrmann's group showed that the nanomagnets did not damage cells or promote clotting—two critical safety milestones.
At the annual meeting of the American Society of Anesthesiologists in October, Herrmann presented data showing that the nanomagnets are partially taken up by monocytes and macrophages, two forms of immune cells. That's an important proof of principle for any future application of the technology in fighting serious infections.
Herrmann and her colleagues are now conducting a study of the technology in rats with sepsis—a severe bloodstream infection marked by the massive buildup of damaging immune molecules. Severe sepsis affects approximately a million people in the United States each year.
Jon Dobson, a biomedical engineer at the University of Florida, says detoxification is "a really interesting application" of nanotechnology. His own group has been using magnetic nanoparticles as remote controls to manipulate cellular activity, such as the differentiation of stem cells. "With chemicals, once the process starts, it can be difficult to switch it off. With magnetic technology, you can switch it on and off at will," Dobson says.
The potential uses of the Swiss group's method might extend beyond sepsis to other diseases, including blood cancers, Dobson says. For example, it might be possible to design nanomagnets that pair up with circulating leukemia cells and usher them out of the body, thus reducing the risk of metastasis.
O. Thompson Mefford, a nanotechnology expert at Clemson University, says the approach has appeal. He notes that the human body is a highly oxidative environment, and oxidation of iron weakens the magnetic properties of the material. By coating their magnets in carbon, the Swiss group may have come up with a way to prevent this corrosion.
Still, he says, the viability of the technique remains to be seen: "Having high circulation times, no immune response, and having the magnets not cluster with each other, that's a real challenge."
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