Implant improvement

Engineers at the University of Michigan have developed a nanotech coating for brain implants that helps the devices operate longer and could improve treatment for deafness, paralysis, blindness, epilepsy and Parkinson's disease.

Currently, brain implants operate in one of two ways. Either they stimulate neurons with electrical impulses to override the brain's own signals, or they record what working neurons are transmitting to non-working parts of the brain and reroute that signal.

Presently used on scalp and brain surface, electrodes are giving way to brain-penetrating microelectrodes that can communicate with individual neurons, offering hope for more precise control of signals.

In recent years, researchers at other institutions have demonstrated that these implanted microelectrodes can let a paralysed person use thought to control a computer mouse and move a wheelchair. Michigan researchers' say their coating can improve this type of microelectrode.

Mohammad Reza Abidian, a post-doctoral researcher in the Department of Biomedical Engineering who is among the developers of the new coating, said that the reliability of today's brain-penetrating microelectrodes often begins to decline after they are in place for only a few months.

The new coating Abidian and his colleagues developed is made of three components that together allow electrodes to interface more smoothly with the brain. The coating is made of a special electrically conductive nanoscale polymer called PEDOT, a natural, gel-like buffer called alginate hydrogel, and biodegradable nanofibres loaded with a controlled-release anti-inflammatory drug.

The PEDOT in the coating enables the electrodes to operate with less electrical resistance than current models, which means they can communicate more clearly with individual neurons.

The alginate hydrogel, partially derived from algae, gives the electrodes mechanical properties more similar to actual brain tissue than the current technology. That means that coated neural electrodes would cause less tissue damage.

The biodegradable, drug-loaded nanofibres fight the 'encapsulation' that occurs when the immune system tells the body to envelop foreign materials.

Encapsulation is another reason that electrodes can stop functioning. The nanofibres fight this response well because they work with the alginate hydrogel to release the anti-inflammatory drugs in a controlled, sustained fashion as the nanofibres themselves break down.