A groundbreaking innovation in brain stimulation has emerged from MIT, showcasing novel magnetic nanodiscs as a significantly less invasive technique to stimulate brain regions. These tiny, disc-shaped nanoparticles, measuring approximately 250 nanometers in diameter (about 1/500 the width of a human hair), could revolutionize stimulation therapies by eliminating the need for implants or genetic modifications.
Researchers envision that these nanodiscs can be directly injected into targeted brain areas and activated remotely by applying a magnetic field. This promising development not only opens avenues in biomedical research but holds potential for future clinical applications following thorough testing.
The details of this innovative research are published in the journal Nature Nanotechnology, led by Polina Anikeeva, a professor at MIT in both the Materials Science and Engineering and Brain and Cognitive Sciences departments, alongside graduate student Ye Ji Kim and a team of 17 additional collaborators from MIT and Germany.
Currently, deep brain stimulation (DBS) is a standard procedure involving implanted electrodes to alleviate symptoms associated with neurological and psychiatric disorders, such as Parkinson’s disease and obsessive-compulsive disorder. While effective, the invasive nature of DBS and the associated surgical complications can limit its application. The introduction of these magnetic nanodiscs presents a much more benign solution to achieve similar therapeutic outcomes.
In the past decade, various non-invasive methods have emerged for brain stimulation, but many were hampered by their inability to precisely target deep brain structures. Anikeeva’s Bioelectronics group, along with other researchers, has explored magnetic nanomaterials for the remote transmission of magnetic signals to stimulate the brain. However, most of these methods relied on genetic modifications, preventing their use in human subjects.
Motivated by the universality of nerve cell responsiveness to electrical signals, graduate student Ye Ji Kim theorized that a magnetoelectric nanomaterial—capable of converting magnetization into electrical potential—could facilitate remote magnetic brain stimulation. Nevertheless, synthesizing such a nanoscale material posed a significant challenge.
Kim successfully created the innovative magnetoelectric nanodiscs and partnered with Noah Kent, a postdoctoral researcher in Anikeeva’s lab with physics expertise, to analyze the properties of these particles. The superconductive design features a dual-layer magnetic core encased within a piezoelectric shell. The magnetostrictive core alters its shape when magnetized, consequently generating strain in the piezoelectric shell. This process produces variable electrical polarization, enabling the particles to deliver electrical impulses to neurons when exposed to magnetic fields.
A crucial aspect of the nanodiscs’ effectiveness lies in their disc shape, differing from earlier attempts using spherical magnetic nanoparticles, which exhibited minimal magnetoelectric effects. Kim noted that the anisotropic design amplifies the magnetostrictive properties by over a thousand times, contributing to their improved functionality.
The researchers demonstrated the efficacy of their nanodiscs by integrating them into cultured neurons, allowing precise activation via brief magnetic pulses—without necessitating genetic alterations. Subsequently, the team injected a solution of the nanodiscs into selected brain regions of mice, where activation was triggered by a relatively low-power electromagnet. This remote control enabled the researchers to influence neuron activity and behavior.
The team successfully targeted the ventral tegmental area, a brain region related to reward sensations, as well as the subthalamic nucleus, responsible for motor control. “This area is typically where electrodes are inserted to treat Parkinson’s disease,” Kim explained. The researchers successfully demonstrated that injecting nanodiscs into only one hemisphere induced rotational movements in healthy mice when a magnetic field was applied.
Overall, the electrical stimulation achieved with the nanodiscs mirrored the effects of conventional implanted electrodes delivering mild stimulation, while significantly reducing foreign body responses compared to traditional methods. This advancement suggests a potential pathway toward safer deep brain stimulation.
While the researchers have successfully enhanced magnetostrictive capabilities, further work is essential to improve the conversion efficiency of magnetic effects into electrical impulses. Despite achieving a thousand-fold increase in magnetostrictive properties, the resulting electrical output was only four times greater than that of conventional spherical particles.
“Our progress indicates a promising direction, but there’s more to be done to fully harness the enhancement potential,” Kim noted. “We need to ensure that the exceptional amplification in magnetostriction translates effectively into enhanced magnetoelectric coupling.”
The unexpected influence of particle shape on magnetostriction was an intriguing discovery for the team. Anikeeva remarked, “While we’ve created a record-setting particle, its full potential has yet to be realized.” Although the nanodiscs are already suitable for preliminary research in animal models, transitioning to clinical use in humans will necessitate additional steps, including extensive safety evaluations. “This is where academic researchers may need to collaborate for rigorous studies,” Anikeeva stated.
The research team comprised experts from MIT’s departments of Materials Science and Engineering, Electrical Engineering and Computer Science, Chemistry, and Brain and Cognitive Sciences, alongside entities like the Research Laboratory of Electronics, the McGovern Institute for Brain Research, and the Koch Institute for Integrative Cancer Research, as well as colleagues from Friedrich-Alexander University in Germany. Funding for the study was partially provided by the National Institutes of Health, among other institutions.
Photo credit & article inspired by: Massachusetts Institute of Technology
