Carnivorous Plants Inspire Researchers to Build Better Brain Implants
Taking inspiration from carnivorous plants, researchers in Korea have developed new technology that may increase the longevity of surgical devices implanted into the brain.
The research may lead to improvements in deep brain stimulation (DBS) — a surgical treatment for Parkinson’s disease that involves inserting a device that provides electrical stimulation into the brain — and other therapies that involve brain-machine interfaces.
The new technology “is also expected to contribute to faster commercialization by considerably extending the replacement cycle of human implantable medical devices,” the study’s co-authors Il-Joo Cho, PhD, of the Brain Science Institute, and Jung-Mok Seo, PhD, at Yonsei University, said in a press release.
Results were described in Advanced Science, in the article “A Lubricated Nonimmunogenic Neural Probe for Acute Insertion Trauma Minimization and Long-Term Signal Recording.”
In DBS and some other medical treatments, a device is implanted into the brain. However, the physical act of implanting a device can cause damage to brain tissue, resulting in inflammation as the body tries to heal. In addition, the presence of any foreign object in the body can trigger chronic inflammation as the immune system attempts to fight the perceived invader.
This inflammation can damage these medical devices, reducing their functionality and making it so they don’t last as long in the body, which means additional surgeries or treatments may become necessary. To avoid this inflammation, it would be helpful to develop devices that cause minimal damage to brain tissue when they’re inserted, and that don’t set off the immune system once they’re in the body.
To create such a device, scientists looked for inspiration from nature — specifically, to Nepenthes pitcher plants.
Pitcher plants are a type of carnivorous plant. Whereas most plants get their nutrients (especially nitrogen) from the soil, pitcher plants and certain other species, like the more well-known Venus flytrap, also get nutrients by killing and digesting insects and other small animals.
Pitcher plants catch their prey using a specialized structure that looks a bit like a water pitcher, which is how these plants get their name. The sides of the “pitcher” are covered in an extremely slippery coating, and the bottom is full of digestive juices. When an unsuspecting insect wanders too close to the pitcher, it slips on the side and falls in, where it quickly becomes the plant’s meal.
The coating on the inside of the pitcher is so slippery that it’s nearly frictionless, and that’s where researchers saw potential for opportunity. They reasoned that if they could create a similarly slippery coating around a probe that was inserted into the brain, the lack of friction would mean that the insertion causes minimal mechanical damage to brain tissue.
The researchers showed that coating a specially designed probe with such a fluid — which they called lubricated immune-stealthy probe surface, or LIPS — led to marked reductions in friction during insertion, as expected, and this was tied to notable decreases in inflammation around the probe.
In addition to its friction-reducing properties, the team showed that LIPS-coated probes had anti-biofouling properties. In other words, they could prevent cells from sticking to them. In the context of inflammation, this means that inflammatory immune cells would have a harder time latching on to the probe and damaging it.
Experiments in mice showed that LIPS-coated probes were able to detect electrical signals in the brain more strongly than bare probes. The coated probes also could record brain signals for twice as long as bare probes (16 vs. 8 weeks).
“These results suggest that the near-frictionless and anti-biofouling properties of LIPS have the capability of increasing not only the short-term signal recording performance but also the life of the device,” the researchers wrote.
“LIPS not only addresses existing challenges of commercial implantable devices such as silicon-based neural probes and deep brain stimulators (DBSs) but also offers a promising biocompatible coating for any implantable medical device,” they added.