Hydrogel brain implant may excel where others fall short
Among other things, brain implants are capable of stimulating specific neurons, and of delivering medication to specific regions. An experimental new implant could overcome a common limitation of others, by transforming from rigid to soft states.
Existing implants incorporate devices such as electrodes, which are typically fairly stiff. The brain tissue that those electrodes are inserted into, on the other hand, is very soft.
As a result, the body's immune system tends to identify implants as foreign objects, forming a layer of scar tissue around them. Over time, that layer becomes thick enough that it prevents the implants from properly functioning. And while encasing the electrodes in a soft elastic material may help, such materials are usually still considerably stiffer than brain tissue, ultimately still triggering an immune response.
Seeking an alternative, scientists at the Korea Advanced Institute of Science and Technology (KAIST) developed an implant consisting of a bundle of ultra-thin multi-functional polymer fibers, embedded in and surrounded by a polyacrylamide-alginate hydrogel. The fiber bundle consists of an optical waveguide for stimulating neurons via light exposure, three microelectrodes for monitoring neuronal activity, and three microfluidic channels for targeted delivery of liquid medication.
Because the hydrogel is rigid in its initial dry state, it can be relatively easily inserted into brain tissue without the use of any supportive guiding devices. Once implanted, however, it absorbs body fluids and becomes very soft and pliable – much like the tissue that surrounds it. This means it's less likely to be perceived as a foreign object.
When tested on lab mice, the implant was able to detect neural signals for up to six months, which is reportedly "far beyond what had been previously recorded." The researchers additionally noted a significant reduction in foreign body responses, as compared to conventional implants.
"With our discovery, we look forward to advancements in research on neurological disorders like Alzheimer’s or Parkinson’s disease that require long-term observation," says the lead scientist, Prof. Seongjun Park.
A paper on the research was recently published in the journal Nature Communications.
And this isn't the first time we've heard about hydrogel being used for brain-friendlier implants. Last year, scientists from MIT and China developed implantable electrodes made of a hydrogel incorporating an electrically conductive polymer known as PEDOT:PS.