Many behaviors that we might think of as simple switch, such as introvertedness vs extrovertedness, are actually controlled by complex neural networks in the brain. In many scientific fields, understanding how something works requires meddling with the system, to see how things change. However, understanding these complex neural networks requires tools that can manipulate neural activities and can target very specific neurons so that nothing else is affected. Although conventional implanted electrodes could effectively manipulate neuron activities, they cannot distinguish different neuron types. One tool that has demonstrated cell-type specificity is pharmacological modulation, which requires an invasive procedure of implanting a tube to inject drugs directly into the brain. Recently, scientists from MIT have developed a minimally-invasive and precise drug delivery system that is controlled by an external magnetic field.
This new delivery system wraps magnetic nanoparticles, along with the drugs, in tiny lipid spheres. When the spheres are placed in a high-frequency alternating magnetic field, the nanoparticles heat up by ~ 5 degrees Celsius, causing the lipid spheres to become porous enough to release the drugs without releasing the magnetic nanoparticles (and without causing heat damage to surrounding tissues). By comparison, the Earth’s magnetic field is static and does not have the same effect. As the magnetic field turns off, the lipid spheres seals, stopping drug delivery.
To manipulate neuron activities, researchers injected drugs into the brain region that controls social behaviors in mice. After exposure to an alternating magnetic field, these mice were observed for 5 min and they showed an increased preference to close interaction with other mice. The ability of the lipid spheres to release multiple doses has enabled a repeated control of sociability, although the significance of the effect started to reduce on the third day of exposure. Four weeks after injection, the brain tissue was examined and no significant inflammation was observed.
This work has introduced a minimally-invasive magnetic field-controlled delivery system that is broadly applicable to all kinds of drugs. In the future, researchers are planning to deliver drugs not only in the brain for treating neurological disorders, such as depression and epilepsy, but also throughout the rest of the body for treating other diseases, such as cancer.
Managing Correspondent: Anqi Zhang
Original journal article: Remotely controlled chemomagnetic modulation of targeted neural circuits. Nature Nanotechnology.
Image Credit: Anikeeva Group, MIT