"Fuzzy Polymers" Improve Brain Implant Performance

Originally Published MDDI July 2002

R&D DIGEST

The use of electronic brain implants is being explored as a potential treatment for a range of conditions, including vision impairment and paralysis. But the functionality of these implants will be determined partly by the effectiveness of the electrodes used to provide an interface between the implants and the living tissue.

Now, researchers at the University of Michigan (Ann Arbor, MI) have developed a polymerization process that could improve such interfaces. According to David C. Martin, director of the university's Macromolecular Science and Engineering Center, the polymers are processed into a "fuzzy" form that can enhance the compatibility of electronic implants with brain tissue.

The electrodes used to pick up electrical signals transmitted by nerve cells are coated with growth factors that encourage ingrowth of brain tissue to enable each probe to make contact with a series of neurons. The probes could receive transmitted signals that would be interpreted and used to control an external device. Patients could use such systems to control artificial limbs or devices by thinking about a given task.

Initial experiments with guinea pigs showed that conventional electrodes do not make effective contact with the brain. "The implanted electrodes are solid, hard and smooth," Martin says, "whereas the brain is soft, wet, and alive." The differences can cause the electrodes to lose contact with the brain and block the signal.

By using the rough-surfaced, fuzzy polymers, the probes mesh better with neurons. "The scheme is to have these electrodes make a connection with the neurons quickly, before the other cells get in and wall them off," says Martin.

Biological molecules were also incorporated into the polymer coating to selectively attract target neurons. In addition to improving contact with brain tissue, it was found that the fuzzy polymers could be used to fine-tune the electrode's ability to conduct electrical signals.

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