The brain is an incredibly soft organ — so soft that it can be likened to pudding. Most implants that could help doctors monitor or treat disordered brain activity in their patients are simply too rigid to be left in the brain long term.
When brain tissue moves in the course of normal daily activities, a rigid implant can cut into it. That in turn triggers inflammation and scarring called a foreign body response, and that makes the device less effective over time.
Researchers from the Montreal Neurological Institute-Hospital and McGill University’s Department of Biomedical Engineering are working on an implant that closely matches the brain’s pudding-like softness with the help of a confection-inspired solution. Their study was published in Advanced Materials Technologies.
The new device is made of a thin piece of silicone, and at a ~0.2 mm thickness, it’s similar to a piece of sewing thread. That allows the device to match the mechanical properties of brain tissue.
But at a pudding-like softness, getting the delicate implant into the right position in the brain still requires a hard tool for insertion. That’s why the authors developed a hardened sugar shuttle to surround the implant.
The fabrication of the sugar shuttle borrows from the kitchen: melting, caramelizing, and moulding the material into the desired shape. The results is a non-toxic microneedle that dissolves within seconds after being introduced into the brain, leaving the soft implant behind.
“The implants we created are so soft that the body doesn’t see it as a big threat, allowing them to interact with the brain with less interference,” said first author Edward Zhang in a press release.
“I am excited about the future of brain implant technology and believe our work helps pave the path for a new generation of soft implants that could make brain implants a more viable medical treatment.”
The researchers implanted their threadlike silicone device into rat brains and compared them to traditional implants made of silicon and polydimethylsiloxane, both of which are much more rigid. Several weeks after implantation, the tissue surrounding the soft implant had significantly lower signs of foreign body response than the rigid ones, suggesting it could function more reliably in the long term.
This opens up opportunities to continuously monitor neurological conditions, and even treat them by sending electrical stimulation that could reset normal brain activity. Conditions like Parkinson’s disease, epilepsy, or even dementia could benefit from a device like this.
By matching the soft properties of the brain, the combination of a short-term microneedle and a long-term flexible implant may one day deliver a solution that lasts much longer than the rigid devices available today.