Surgically implanted neurostimulators are presently used for many diseases, ranging from movement disorders, like Parkinson’s, to chronic pain. But as current research efforts suggest, their use will potentially expand to mood disorders, such as depression, and memory enhancement for Alzheimer’s. Contemporary neurostimulator technology relies on platinum in its material design, given the element’s excellent conductivity and biocompatibility. It is abundant in the electronics for deep brain stimulators, surface electrodes, and microelectrode arrays.
Despite the biocompatibility of platinum, the element undergoes irreversible electrochemical dissolution and degrades over time when implanted in the brain. The byproducts of this reaction can be neurotoxic and create scarring between the neurostimulator and brain tissue, leading to decreased efficacy over time. Given this concern for long-term efficacy, there has been an unmet need to improve the electrochemical interface between neurostimulator electrode and brain.
Researchers at Purdue University have developed a novel method of protection against degradation that neurostimulator implants typically experience throughout their device lifecycle. In a recent paper published in the journal 2D Materials, the authors Hyowon Lee and colleagues present their methods for protecting platinum neurostimulators with a monolayer of graphene.
In the study, they fabricated circular and fractal shaped microelectrodes and transferred a monolayer graphene sheet (prepared separately), before creating the final pattern using photolithography and reactive ion etching.
The authors then compared the platinum dissolution rates of both circular and fractal shaped electrodes with or without graphene coating, and found that the graphene coating significantly reduced the platinum dissolution rate. The authors, therefore, conclude that the graphene monolayer can effectively prevent dissolution as a diffusion barrier on neurostimulator electrodes.
While clearly,these results need to be verified in brain tissue models and in further in vivo experiments, the initial conclusions are promising. These results suggest that it is possible to easily improve neurostimulator device longevity at a time when the indications for neurostimulator implantation are expanding.
Senior author Hyowon Lee said. “We think neurosurgeons, neurologists, and other scientists in neuroengineering field will be able to use this electrode technology to better help patients with implantable devices for restoring eyesight, movement, and other lost functionalities.”
