Lubricated coating could keep brain implants working longer
While brain-implanted electrodes do show promise for applications such as restoring capabilities to the disabled, they tend to lose their functionality over time. A new coating, however, could allow them to work much longer once implanted.
The main problem with neural implants lies in the fact that they're usually a lot harder than the soft brain tissue into which they're inserted.
This causes the body's immune system to see them as foreign objects, initially resulting in inflammation at the implantation site, and ultimately leading to the formation of a layer of scar tissue around them. That scar tissue greatly compromises their ability to stimulate adjacent neurons, or to monitor neural activity.
In an effort to address this problem, scientists at the Korea Institute of Science and Technology (KIST) and Korea's Yonsei University have developed a new low-friction coating for implanted electrodes, known as Lubricated Immune-stealthy Probe Surface (LIPS). It was inspired by Harvard University's SLIPS (Slippery Liquid-Infused Porous Surfaces) technology, which was in turn inspired by the slippery leaves of the carnivorous pitcher plant.
Designed to be applied to existing neural implants, LIPS consists of a silicon base which is infused with a biocompatible perfluoropolyether lubricant. Although the coating doesn't make the underlying electrode any softer, it does allow it to be slid into the brain with very little deformation or stress to the surrounding brain tissue. Additionally, LIPS' slipperiness keeps immune cells from adhering to it, minimizing the formation of scar tissue.
The scientists tested the coating by applying it to neural probes made up of 32 electrodes, which were implanted into rats' brains. It was found that immediately after implantation, neural activity was detected by over 90 percent of the electrodes – this was twice the amount recorded for a control group of rats that received uncoated probes, which produced much more inflammation.
Additionally, whereas the uncoated probes were able to detect brain signals for only about a month before getting encased in scar tissue, the LIPS-coated probes were able to do so for four months.
It is hoped that once developed further, the coating could also be used to extend the useful lifespan of other types of medical implants. A paper on the research – which was led by KIST's Dr. Il-Joo Cho and Yonsei University's Dr. Jung-Mok Seo – was recently published in the journal Advanced Science.