Pulsing Magnetic Fields Focus Nano-Particles to Target

A new technique to magnetically deliver drug-carrying ferromagnetic rods to hard-to-reach targets could transform the way deep-tissue tumors and other diseases are treated.

Researchers at the University of Maryland (UMD; College Park, USA) and Weinberg Medical Physics (WMP; Bethesda, MD, USA) have joined forces to exploit fast pulsed magnetic fields to reverse the usual behavior of magnetic nanoparticles in a process they termed dynamic inversion. Instead of a magnet attracting the particles, an initial magnetic pulse is used to orient the rod-shaped particles, without pulling them. A subsequent pulse then “pushes” the particles before they can reorient. By repeating the pulses in sequence, the particles can be focused to locations deep between the electromagnets.


Until now, such magnetic nanoparticles could only be attracted to the magnet, and therefore could not be concentrated at any other point than the magnet face. As a result, electromagnets that were held outside of the body had only been able to concentrate drug-delivering particles to targets at or just below the skin surface. The new method could potentially allow clinicians to use these external electromagnets to focus therapy to the precise locations of a disease within a patient using ferromagnetic rods to deliver therapy.

“The Holy Grail of magnetic drug targeting is the dream of using magnets outside the body to minimally invasively direct drug therapy to anywhere inside the body, for example, to inoperable deep tumors or to sections of the brain that have been damaged by trauma, vascular, or degenerative diseases,” said Irving Weinberg, MD, President of WMP. “We have shown that fast pulsing of external electromagnetic fields may be able to achieve this goal.”

One of the factors that make focusing of therapy to central targets between magnets challenging is Samuel Earnshaw’s theorem, which implies that external static magnets cannot create a stable potential energy well between them. The purpose of the fast magnetic pulses is thus equivalent to reversing the sign of the potential energy in the mathematical formulations, enabling a quasi-static stable trap between the magnets.

Related Links:
University of Maryland
Weinberg Medical Physics 
Video: Concentrating Ferromagnetic Cobalt Rods