Innovative nanoparticle purification system uses magnetic fields.

A new system that uses magnetism to purify hybrid magnetic nanoparticles may significantly broaden their potential medical uses, say Penn State inventors Mary Beth Williams and Raymond Schaak.

Hybrid magnetic nanoparticles are infinitesimal structures made up of two or more materials—one of which is iron or another magnetic element—that show promise for drug delivery and medical imaging, among many other applications inside and outside the human body. Until now, though, there has been no good way to clean them.

“Although molecules are synthesized and purified using well-known methods, there have not been analogous methods for purifying nanoparticles,” says Schaak, professor of chemistry. Hybrid particles “are especially challenging,” he adds, “because the methods used to make them often leave impurities that are not easily detected or removed.” Impurities can change the properties of a particle, and even render it toxic. “We had to find a way to separate impurities from the target nanoparticles, even when these particles are similar in size and shape,” Schaak says. The team’s new system does just that.

“Our method uses magnetic fields to slow the flow of particles through tiny glass tubes called capillaries,” explains Williams, associate professor of chemistry. “We use a magnet to pull magnetic particles against the wall of the tube and, when the magnetic field is reduced, the particles flow out of the capillary. Magnetism increases as particle volume increases, so small and gradual changes in the magnetic field let us slowly separate and distinguish between nanoparticles based on even minute magnetic and structural differences.”

The new method has many potential applications, especially within the fields of medicine and diagnostics, Williams says. For example, purified nanoparticles could be used in lieu of contrast dye when patients undergo MRI imaging studies, to track where a drug is traveling in the human body. “Some patients are allergic to traditional contrast dyes, so nanoparticles offer a promising alternative,” she says.

In the future, such particles might even be used to improve cancer-fighting drugs.

“Unfortunately, chemotherapy drugs don’t discriminate: They attack healthy tissue, as well as cancerous tissue,” Williams explains. “If we could use nanoparticle technology to manipulate exactly where the drugs are going, which tissue they attack, and which they leave alone, we could greatly reduce some of the bad side effects of chemotherapy, such as hair loss and nausea. But to do this we need to be able to separate out nanoparticle impurities to make them safe for medical use.

“That’s where this new technology comes in.”

Raymond Schaak, Ph.D., is professor of chemistry in the Eberly College of Science, Mary Beth Williams, Ph.D., is associate professor of chemistry in the Eberly College of Science,

Last Updated October 26, 2011