Deep brain stimulation has emerged as an exciting and promising field for treating both neurological and psychological disorders ranging from Parkinson's disease to depression. But the long-term viability of implants designed for DBS remains uncertain as current electrodes tend to induce an immune response in the patient's body that reduces the treatment's efficacy over time. Looking to overcome this challenge, researchers at Tel Aviv University (TAU) have developed a bioactive coating for electrodes that suppresses the brain's immune response, thereby increasing the longevity and efficacy of the implant.

For optimal results, the brain-computer interface must function seamlessly, according to the researchers. Once implanted under the skin, the medical device emits high-frequency currents that are then transferred to the brain via electrodes. However, the electrodes are often identified by the body as foreign bodies. Consequently, the body attacks the electrodes and forms a barrier to the brain tissue receiving treatment. In turn, the efficacy of the DBS treatment decreases because the signals are not properly communicated to the brain.

Addressing this barrier for DBS implants, the Tel Aviv University researchers have applied a protein-based bioactive coating to the electrodes that serves to camouflage them while also suppressing the brain's immune response. Although other researchers have explored the use of protein-based coatings for such applications, the TAU team sought to employ a protein that is actually active within the brain itself to suppress the immune response to the electrodes. Dubbed interleukin (IL)-1 receptor antagonist, the protein, in its natural setting, serves to maintain physical stability by localizing brain damage, essentially preventing the immune system from overreacting to trauma, according to the researchers.

Touted by the team as the first bioactive coating made from this particular protein, it safely and effectively integrates the electrodes into the desired brain tissue without interrupting normal brain function. In fact, the researchers report that their coated electrodes outperformed both noncoated and other protein-based coatings in preclinical studies conducted with animal models. As a result, the coating could lead to a more-stable, long-term DBS implant design, the researchers note.

Looking to the future, TAU's Aryeh Taub anticipates that the electrode coating could someday even contribute to the development of an interface capable of restoring lost behavioral or motor function resulting from tissue damage. "We duplicate the function of brain tissue onto a silicon chip and transfer it back to the brain," Taub says, explaining that the electrodes will pick up brain waves and transfer them directly to the chip. "The chip then does the computation that would have been done in the damaged tissue and feeds the information back into the brain, prompting functions that would have otherwise gotten lost."