Coating could lead to more effective implanted electrodes

Implants are used in treatments such as deep brain stimulation, a method in which a silicon chip placed under the skin emits high-frequency currents that are transferred to the brain through implanted electrodes that transmit and receive the signals.

The technology, used to treat neurological and psychological disorder, requires a seamless interaction between the brain and the hardware.

The brain attacks the electrodes, identified as foreign bodies by the immune system, and forms a barrier to the brain tissue, making it impossible for the electrodes to communicate with brain activity.

Aryeh Taub of Tel Aviv University’s (TAU’s) School of Psychological Sciences, along with Prof Matti Mintz, Roni Hogri and Ari Magal of the university’s School of Psychological Sciences and Prof Yosi Shacham-Diamand of the university’s School of Electrical Engineering, has developed a bioactive coating that not only ‘camouflages’ the electrodes in the brain tissue but actively suppresses the brain’s immune response.

By using a protein called an interleukin (IL)-1 receptor antagonist to coat the electrodes, the multi-disciplinary team of researchers has found a potential resolution to turn a method for short-term relief into a long-term solution. This development was reported in the Journal of Biomedical Materials Research.

To overcome the creation of the barrier between the tissue and the electrode, the researchers sought to develop a method for placing the electrode in the brain tissue while hiding the electrode from the brain’s immune defences.

Previous research groups have coated the electrodes with various proteins, said Taub, but the TAU team decided to take a different approach by using a protein that is active within the brain itself, thereby suppressing the immune reaction against the electrodes.

In the brain, the IL-1 receptor antagonist is crucial for maintaining physical stability by localising brain damage, Taub explained. For example, if a person is hit on the head, this protein works to create scarring in specific areas instead of allowing global brain scarring.

The team’s coating, claimed to be the first to be developed from this particular protein, integrates the electrodes into the brain tissue and allows them to contribute to normal brain functioning.

In pre-clinical studies with animal models, the researchers found that their coated electrodes perform better than both non-coated and ‘naïve protein’-coated electrodes that had previously been examined.

Measuring the number of damaged cells at the site of implantation, researchers found no apparent difference between the site of electrode implantation and healthy brain tissue elsewhere, Taub said.

In addition, evidence suggests that the coated electrodes will be able to function for long periods of time, providing a more stable and long-term treatment option.