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Posted: Aug 03, 2011
NSF award to develop neural implants using graphene
(Nanowerk News) Neural implants have the potential to treat disorders and diseases that typically require long-term treatment, such as blindness, deafness, epilepsy, spinal cord injury, and Alzheimer's and Parkinson's. However, implantable devices have been problematic in clinical applications because of bodily reactions that limit device functioning time.
Mark Ming-Cheng Cheng, Ph.D., assistant professor of electrical and computer engineering at Wayne State University, is out to change that. He recently received a five-year, $475,000 Faculty Early Career Development (CAREER) grant from the National Science Foundation to study the potential of graphene, a novel carbon material, in the development of a reliable, high-performance, long-term implantable electrode system to improve quality of life using nanotechnology. Cheng is collaborating with colleagues in the School of Medicine, in biomedical engineering, and in WSU's Smart Sensors and Integrated Microsystems and Nano Incubator programs.
Neural disorders and diseases result when parts of the brain don't interact properly or stop interacting altogether. Cheng said that over the past 50 years, electrodes used to stimulate connections between those parts typically stop working after a few weeks because scar tissue forms around the electrode, and the materials that comprise the electrode can't carry enough charge through the scar tissue.
Cheng hypothesizes that graphene, a flexible material recently discovered by Russian scientists, might be better suited to long-term treatment than platinum and iridium oxide, two of the most popular materials now used to make implantable electrodes. Making platinum and iridium oxide electrodes small enough to be implanted reduces the amount of charge they can carry and therefore limits their ability to stimulate neural connections. Additionally, Cheng said, signals from these electrodes to machines that record neural activity often contain a lot "noise" because of the impedance levels of the materials.
Graphene, he said, enables a larger electrical charge and can be made smaller than previous electrodes, yet still big enough to do the job. The smaller size and higher conductivity also decreases impedance, enabling clearer readings of neural activity, Cheng said.
Using graphene electrodes poses a challenge, however, because its flexibility makes it difficult to insert into tissue. In order to overcome that issue, Cheng plans to use a porous silicone "backbone" that slowly and safely biodegrades into brain tissue while releasing anti-inflammatory medication, thus limiting the formation of scar tissue.
Though it's too early to tell how long a graphene electrode will hold up after implantation, Cheng said a five-year lifespan would yield a "huge" number of potential applications in areas like neuroscience, drug delivery, bioelectronics, biosensors and security.
"Real-time sensing and treatment by neural implants can be used to treat a variety of neurological maladies," Cheng said, adding that more than 200,000 patients with full or partial paralysis may benefit from the technology in the United States alone. The cost of care for those patients is well over $200 billion annually, he said.
"This research will help advance fundamental knowledge of the interaction between the neural system and biomaterials of different electrochemical, mechanical and material properties," Cheng said. "Understanding the fundamental mechanism is important in the development of neural prostheses to aid people with disabilities."