The blood-brain barrier is a highly selective semipermeable barrier running inside almost all vessels in the brain that lets through water, some gases and a few other select molecules, while preventing potentially toxic elements in the blood from entering the brain. Researchers from the University of Montreal, Polytechnique Montréal, and CHU Sainte-Justine say that currently 98 percent of therapeutic molecules are also blocked by the barrier, but they have developed a technique using magnetic nanoparticles that opens the door for such molecules, thereby also opening the door to new treatments for brain diseases.
"At the present time, surgery is the only way to treat patients with brain disorders," says Anne-Sophie Carret, study senior author. "Moreover, while surgeons are able to operate to remove certain kinds of tumors, some disorders are located in the brain stem, amongst nerves, making surgery impossible."
Opening the blood-brain barrier to therapeutic molecules, the researchers say, would provide an alternative to surgery for treating various brain diseases. The technique involves sending magnetic nanoparticles to the surface of the blood-brain barrier at the desired location in the brain. The researchers say this could be done using magnetic resonance imaging (MRI) technology, although a different method was used for their study.
Once directed to the desired location, the nanoparticles were exposed to a radio-frequency field that caused them to dissipate heat. The resulting small elevation in temperature places mechanical stress on the barrier that causes a localized opening, which allows therapeutic molecules to pass through. The opening is only temporary, remaining open for around two hours.
"While other techniques have been developed for delivering drugs to the blood-brain barrier, they either open it too wide, exposing the brain to great risks, or they are not precise enough, leading to scattering of the drugs and possible unwanted side effect," says principal investigator Sylvain Martel.
Although the technique was developed using murine (rats and mice) models and is yet to be tested on humans, the researchers are optimistic that it will one day be used in people.
"Although our current results are only proof of concept, we are on the way to achieving our goal of developing a local drug delivery mechanism that will be able to treat oncologic, psychiatric, neurological and neurodegenerative disorders, amongst others," says Carret.
The team's study will be published in an upcoming edition of the Journal of Controlled Release.
Source: University of Montreal
