École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
Spinal cord injuries may no longer mean a lifetime of paralysis, say researchers at EPFL. They have developed a new neural stimulation implant that, they say, can be applied directly to the spinal cord without causing damage and inflammation.
In experiments, the researchers were able to get rats with spinal injuries walking on their own again using a combination of electrical and chemical stimulation. But, they caution that applying this method to humans would require multifunctional implants that could be installed for long periods of time on the spinal cord without causing any tissue damage.
These prototype implants, called e- Dura, are designed specifically to be implanted on the surface of the brain or spinal cord. The small device closely imitates the mechanical properties of living tissue, and can simultaneously deliver electric impulses and pharmacological substances. This reduces the risks of rejection and/or damage to the spinal cord. (See Figure 1) The devices were developed through a combination of materials science, electronics, neuroscience, medicine, and algorithm programming.
How It Works
Current “surface implants” can’t be applied to the spinal cord or brain long term, beneath the nervous system’s covering called the dura mater, because as nerve tissues move or stretch, they rub against the rigid devices creating friction, and, subsequently, inflammation, scar tissue, and rejection.
The e-Dura implant is flexible and stretchy, and can be placed beneath the dura mater, directly onto the spinal cord. Its elasticity is nearly identical to the living tissue surrounding it, which keeps friction and inflammation to a minimum. When implanted into rats, the prototype did not cause damage nor rejection, even after two months of use. After applying it to paralyzed rats, the rats regained the ability to walk on their own again after a few weeks of training. More rigid traditional implants would have caused significant nerve tissue damage during this period of time.
The device prototype combines electrical and chemical stimulation. Its electronic elements stimulate the spinal cord at the point of injury. The silicon substrate is covered with cracked gold electric conducting tracks that can be pulled and stretched. The electrodes are made of an innovative composite of silicon and platinum microbeads. They can be deformed in any direction, while still ensuring optimal electrical conductivity. And, a fluidic microchannel can enable the delivery of pharmacological substances, such as neurotransmitters, that can reanimate the nerve cells beneath the injured tissue.
In addition, the implant can monitor real-time electrical impulses from the brain. The scientists say that they were able to extract the animal’s motor intention before it was translated into movement.
The implants have only been tested in rats so far, but the researchers conjecture that they have great potential for use in patients with epilepsy, Parkinson’s disease, and for pain management. They plan to move towards clinical trials in humans, and to develop their prototype in preparation for commercialization.