Healthcare (Commonwealth Union) – MIT researchers have developed novel magnetic nanodiscs that could offer a significantly less invasive method of stimulating specific areas of the brain, potentially enabling stimulation therapies without the need for implants or genetic modifications.
These tiny nanodiscs, measuring about 250 nanometers in diameter (roughly 1/500th the width of a human hair), could be injected directly into targeted brain regions. Once in place, they could be activated remotely by applying a magnetic field externally. This breakthrough could have immediate applications in biomedical research and, after thorough testing, might be used clinically in the future.
The research behind these nanoparticles was published in Nature Nanotechnology by Polina Anikeeva, a professor in MIT’s Materials Science and Engineering and Brain and Cognitive Sciences departments, along with graduate student Ye Ji Kim and 17 collaborators from MIT and Germany.
Currently, deep brain stimulation (DBS) is widely used to treat neurological and psychiatric disorders like Parkinson’s disease and obsessive-compulsive disorder by implanting electrodes into specific brain regions. While effective, DBS is limited by the complexity of the surgery and associated risks. These new nanodiscs could offer a far less invasive alternative, achieving similar outcomes without surgery.
Although other non-invasive brain stimulation techniques have been explored over the past decade, many were limited in their ability to target specific or deep brain regions. Anikeeva’s Bioelectronics group, along with others in the field, has worked for years on using magnetic nanomaterials to remotely stimulate the brain. However, earlier methods required genetic modifications, making them unsuitable for human use. The new nanodiscs could be a safer, more viable solution.
All nerve cells are responsive to electrical signals, so Kim, a graduate student in Anikeeva’s lab, proposed that a magnetoelectric nanomaterial capable of efficiently converting magnetism into electrical potential could provide a method for remote magnetic stimulation of the brain. However, designing a nanoscale magnetoelectric material presented a significant challenge.
Kim developed new magnetoelectric nanodiscs and worked with Noah Kent, a postdoctoral researcher in Anikeeva’s lab with a physics background and the study’s second author, to analyze the properties of these particles.
The nanodiscs are composed of a two-layer magnetic core surrounded by a piezoelectric shell. The core is magnetostrictive, meaning it changes shape when magnetized, and this deformation generates stress in the piezoelectric shell, which then creates fluctuating electrical polarization. The combination of these effects allows the particles to deliver electrical pulses to neurons when exposed to magnetic fields.
A crucial factor in the discs’ success is their shape. Earlier efforts used spherical magnetic nanoparticles, but the magnetoelectric effect was minimal, explains Kim. The disc shape enhances magnetostriction by more than 1,000 times, according to Kent.
The team tested their nanodiscs on cultured neurons and successfully activated the cells using brief magnetic pulses, without the need for any genetic modification.
Next, they injected small droplets of a solution containing magnetoelectric nanodiscs into targeted areas of the mice’s brains. By activating a relatively weak electromagnet nearby, the particles were able to release a small electrical charge in those specific brain regions. The stimulation could be remotely controlled, turning on and off in sync with the switching of the electromagnet. That electrical stimulation “had an impact on neuron activity and on behavior,” said Kim.
The researchers discovered that the magnetoelectric nanodiscs were able to stimulate a deep brain region known as the ventral tegmental area, which is linked to the sensation of reward.
The researchers stimulated another brain area as well, the subthalamic nucleus, that was linked to the motor control. “This is the region where electrodes typically get implanted to manage Parkinson’s disease,” said Kim.
The role of stimulating neurons has always been a key component of neurology with activation and deactivation being a focus as well. The findings may provide valuable insights into neurology.
