Brain-computer interfaces are at the forefront of treating neurological and psychological disorders, in cluding Parkinson’s, epilepsy, and depression. Among the most promising technologies is deep brain stimulation (DBS) — a method in which an implanted silicon chip ejects high frequency currents under the skin that are transferred to the brain through implanted electrodes that send and receive signals. Approximately 30,000 people worldwide are currently using DBS. But to ensure that the signals are properly sent and received requires a smooth interaction between the brain and the hardware.

Fig. 1 — Implantable electrodes with a protein-based bioactive coating suppress the brain’s immune response, increasing the electrode’s performance.

The long-term viability of implants designed for DBS remains uncertain since electrodes have a tendency to produce an undesirable immune response in the patient’s body that reduces the treatment’s efficacy. The body identifies the electrodes as foreign bodies and attacks them forming a barrier to the brain tissue receiving treatment. In turn, the efficacy of the treatment decreases because the signals are not being properly communicated to the brain.

In trying to overcome this challenge, a multi-disciplinary team of researchers at Tel Aviv University (TAU) Tel Aviv, Israel, have developed a a protein-based bioactive coating for electrodes that suppresses this immune response, thereby increasing the longevity and efficacy of the implant.

How It Works

The coating, in effect, camouflages the electrodes while suppressing the brain's immune response. (See Figure 1) While other researchers have explored using protein-based coatings for such applications, the TAU team is using a protein that is actually active within the brain itself to suppress the immune reaction to the electrodes. Called interleukin (IL)-1 receptor antagonist, the protein, in its natural setting, maintains physical stability by localizing brain damage, in essence preventing the immune system from overreacting to trauma, say the researchers. This development was reported in the Journal of Biomedical Materials Research.

Claimed as the first bioactive coating made from this particular protein, it safely and effectively iantegrates the electrodes into the desired brain tissue without interrupting normal brain function, claim the researchers. In the brain, the IL-1 receptor antagonist is crucial for maintaining physical stability by localizing brain damage, Taub explains.

Fig. 2 — Computer tomography of human brain, from base of the skull to top, taken with intravenous contrast medium.

The coating, the first to be developed from this particular protein, not only integrates the electrodes into the brain tissue, but allows them to contribute to normal brain functioning. In fact, they report that their coated electrodes outperformed both non-coated and other protein-based coatings in preclinical studies conducted with animal models. As a result, the coating may lead to a more-stable, long-term DBS implant design.

Taub says that in the future, he anticipates that the electrode coating could someday aid in 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. He explains 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.”