A new technique to magnetically deliver drug-carrying nanorods to deep targets in the body using fast-pulsed magnetic fields could transform the way deep-tissue tumors and other diseases are treated, say researchers at the University of Maryland (UMD) and Bethesda-based Weinberg Medical Physics LLC (WMP).

Instead of surgery or systemically administered treatments (such as chemotherapy), the use of magnetic nanoparticles as drug carriers could potentially allow clinicians to use external magnets to focus therapy to the precise locations of a disease within a patient, such as inoperable deep tumors or sections of the brain that have been damaged by trauma, vascular, or degenerative diseases.

So for years, researchers have worked with magnetic nanoparticles loaded with drugs or genes to develop noninvasive techniques to direct therapies and diagnostics to targets in the body.

However, due to the physics of magnetic forces, particles otherwise unaided could only be attracted to a magnet, not concentrated into points distant from the magnet face. So in clinical trials, magnets held outside the body have only been able to concentrate treatment to targets at or just below the skin surface, the researchers say.

“What we have shown experimentally is that by exploiting the physics of nanorods we can use fast-pulsed magnetic fields to focus the particles to a deep target between the magnets,” said UMD Institute for Systems Research Professor Benjamin Shapiro.

Pulsed magnetic fields 

These pulsed magnetic fields allowed the team to reverse the usual behavior of magnetic nanoparticles. Instead of a magnet attracting the particles, they showed that an initial magnetic pulse can orient the rod-shaped particles without pulling them, and then a subsequent pulse can push the particles before the particles can reorient. By repeating the pulses in sequence, the particles were focused to locations between the electromagnets.

The study, published last week in Nano Letters, shows that using this method, ferromagnetic nanorods carrying drugs or molecules could be concentrated to arbitrary deep locations between magnets.

IronFocus Medical | Concentrating Ferromagnetic Rods. Focusing of ferromagnetic rods to a central target. Four snapshots of concentrating cobalt rods to the center of the sample area using dynamic magnetic inversion. The rods began optically undetectable and dispersed throughout the region. After 09:06 min, the rods were concentrated at the center of the sample area.

“This technology could enable a new therapeutic modality that combines the spatial precision of traditional image-guided radiation with the biochemical specificity of molecular medicine,” said Dr. John R. Adler, Vice President and Chief of New Clinical Applications for Varian Medical Systems.

The researchers are now working to demonstrate this method in vivo to prove its therapeutic potential and have launched IronFocus Medical, Inc., a startup company established to commercialize their invention.

The fast magnetic fields were developed with funding from Small Business Innovation Research grants awarded by the National Cancer Institute; National Heart, Lung and Blood Institute; and the National Institute for Neurological Disorders and Stroke. Funding to develop the correct sequence of magnetic pulses was provided by the National Science Foundation.