Neuroprosthetics for paralysis:Biocompatible, flexible implant slips into thespinal cord8 January 2015

Credit: Ecole Polytechnique Federale de Lausanne

New therapies are on the horizon for individualsparalyzed following spinal cord injury. The e-Duraimplant developed by EPFL scientists can beapplied directly to the spinal cord without causingdamage and inflammation. The device is describedin an article appearing online Jan. 8, 2015, in Science magazine.

EPFL scientists have managed to get rats walkingon their own again using a combination of electricaland chemical stimulation. But applying this methodto humans would require multifunctional implantsthat could be installed for long periods of time onthe spinal cord without causing any tissue damage.This is precisely what the teams of professorsStéphanie Lacour and Grégoire Courtine havedeveloped. Their e-Dura implant is designedspecifically for implantation on the surface of thebrain or spinal cord. The small device closelyimitates the mechanical properties of living tissue,and can simultaneously deliver electric impulsesand pharmacological substances. The risks ofrejection and/or damage to the spinal cord havebeen drastically reduced. An article about theimplant will appear in early January in Sciencemagazine.

So-called "surface implants" have reached aroadblock; they cannot be applied long term to the

spinal cord or brain, beneath the nervous system'sprotective envelope, otherwise known as the "duramater," because when nerve tissues move orstretch, they rub against these rigid devices. After awhile, this repeated friction causes inflammation,scar tissue buildup, and rejection.

An easy-does-it implant

Flexible and stretchy, the implant developed atEPFL is placed beneath the dura mater, directlyonto the spinal cord. Its elasticity and its potentialfor deformation are almost identical to the livingtissue surrounding it. This reduces friction andinflammation to a minimum. When implanted intorats, the e-Dura prototype caused neither damagenor rejection, even after two months. More rigidtraditional implants would have caused significantnerve tissue damage during this period of time.

Credit: Ecole Polytechnique Federale de Lausanne

The researchers tested the device prototype byapplying their rehabilitation protocol—whichcombines electrical and chemical stimulation - toparalyzed rats. Not only did the implant prove itsbiocompatibility, but it also did its job perfectly,

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allowing the rats to regain the ability to walk on theirown again after a few weeks of training.

"Our e-Dura implant can remain for a long period oftime on the spinal cord or the cortex, preciselybecause it has the same mechanical properties asthe dura mater itself. This opens up newtherapeutic possibilities for patients suffering fromneurological trauma or disorders, particularlyindividuals who have become paralyzed followingspinal cord injury," explains Lacour, co-author ofthe paper, and holder of EPFL's Bertarelli Chair inNeuroprosthetic Technology.

Flexibility of tissue, efficiency of electronics

Developing the e-Dura implant was quite a feat ofengineering. As flexible and stretchable as livingtissue, it nonetheless includes electronic elementsthat stimulate the spinal cord at the point of injury.The silicon substrate is covered with cracked goldelectric conducting tracks that can be pulled andstretched. The electrodes are made of aninnovative composite of silicon and platinummicrobeads. They can be deformed in anydirection, while still ensuring optimal electricalconductivity. Finally, a fluidic microchannel enablesthe delivery of pharmacological substances -neurotransmitters in this case - that will reanimatethe nerve cells beneath the injured tissue.

The implant can also be used to monitor electricalimpulses from the brain in real time. When they didthis, the scientists were able to extract withprecision the animal's motor intention before it wastranslated into movement.

"It's the first neuronal surface implant designedfrom the start for long-term application. In order tobuild it, we had to combine expertise from aconsiderable number of areas," explains Courtine,co-author and holder of EPFL's IRP Chair in SpinalCord Repair. "These include materials science,electronics, neuroscience, medicine, and algorithmprogramming. I don't think there are many places inthe world where one finds the level ofinterdisciplinary cooperation that exists in ourCenter for Neuroprosthetics."

For the time being, the e-Dura implant has beenprimarily tested in cases of spinal cord injury inparalyzed rats. But the potential for applying thesesurface implants is huge - for example in epilepsy,Parkinson's disease and pain management. Thescientists are planning to move towards clinicaltrials in humans, and to develop their prototype inpreparation for commercialization.

More information: "Electronic dura mater for long-term multimodal neural interfaces," www.sciencemag.org/lookup/doi/…1126/science.1260318

Provided by Ecole Polytechnique Federale deLausanne

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APA citation: Neuroprosthetics for paralysis: Biocompatible, flexible implant slips into the spinal cord (2015,January 8) retrieved 24 February 2015 from http://medicalxpress.com/news/2015-01-neuroprosthetics-paralysis-biocompatible-flexible-implant.html

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