Magnetic Nanoparticles Could Feed Drugs Straight Into Your Brain

Nanotechnology is busting the blood-brain barrier.

Jordan Pearson

Jordan Pearson

​Image: Flickr/​David Foltz

​Therapeutic drugs might soon be able to zoom around inside our bodies, guided by remote control. But when they reach the brain, they're likely to hit a literal barrier meant to protect our precious noggins from harmful toxins—the blood-brain barrier, to be precise.

Now, scientists have discovered a new way to use bypass this barrier using magnetic nanoparticles.

The blood-brain barrier (BBB) is a tightly-connected series of cells that separate the blood circulating in the body from the brain's internal fluid. The barrier is extremely selective in what it lets though—according to one study, 98 percent of small particles don't make past the BBB. That's a problem when you're trying to send drugs into the brain. While some solutions have been floated, like disguising medical drugs with molecules known to pass through the barrier, the size of the molecules used is a drawback.

To overcome this issue, researchers from École Polytechnique de Montréal and the University of Montreal in—you guessed it—Montreal, Canada, turned to nanotechnology. In a paper to be published in an upcoming issue of the Journal of Controlled Release—available online—the researchers describe how they injected nanoparticles made of magnetic elements into anaesthetized mice and used a low radiofrequency signal to heat them up, the result of a phenomenon known as Néel relaxation.

According to the researchers, "each time the magnetic moments of the [magnetic nanoparticles] align with the alternating direction of the [radiofrequency] field, they release this energy once they relax back to their original direction." The heat emitted by the magnetic nanoparticles made the BBB more permeable for a brief period—long enough to let some dye bonded to the nanoparticles slip through.

A schematic of the experimental setup. "MNPs" stands for magnetic nanoparticles. Image: Tabatabaei, et. al. 

That's pretty amazing, you might be thinking, but what about the guided drugs? To you I say: fair. It's true that the scientists merely injected their magnetic nanoparticles in this experiment. But, in combination with other techniques, the researchers wrote, this approach could be used to guide nanoparticle-bonded drugs from wherever they're injected to the BBB and into the brain.

"Our team has previously shown propulsion of the same [magnetic nanoparticles] in the vasculature towards a target site using a modified clinical MRI," the authors wrote. "We believe that the combination of the transient BBB opening and the MRI-based targeting technique can have a high impact on localized drug delivery to the brain."

Impressed yet? Okay, let me explain how this works: MRI machines use powerful electromagnetic fields to scan the human body (including the brain) in great detail. By rigging one of these to emit the right frequencies in a previous experiment, the scientists were able to steer particles throughout the body.

Imagine: instead of undergoing invasive brain surgery, someone suffering from a brain tumor could have a potentially life-saving drug bound to a magnetic nanoparticle injected into a vein in her arm, lie in an MRI machine, and have it go up and through her brain-blood barrier to where it's needed.

"Glioblastoma multiforme is the most common and invasive malignant primary brain tumor in children," the authors wrote. "With magnetic heating of magnetic nanoparticles that are attached to the BBB, we can evaluate the efficacy of orally administered chemotherapeutic drugs such as temozolomide on this tumor."

As with any new medical discovery, it's worth noting that a fair amount of research and testing must be done before these two approaches can be made to work together—forget about it being used in humans in the near future. But with these advances, we're on our way to getting smart drugs sent straight to the dome.