Ecole Polytechnique de Lausanne. Switzerland: New therapies are on the horizon for individuals
paralyzed following spinal cord injury. The e-Dura implant developed by
EPFL scientists can be applied directly to the spinal cord without
causing damage and inflammation. The device is described in an article
appearing online January 8, 2015, in Science.
EPFL scientists have managed to get rats walking on
their own again using a combination of electrical and chemical
stimulation. But 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. This is
precisely what the teams of professors Stéphanie Lacour and Grégoire
Courtine have developed. Their e-Dura implant is designed specifically
for implantation 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. The risks of rejection and/or damage to the spinal cord have
been drastically reduced. An article about the implant will appear in
early January in Science Magazine.
So-called “surface
implants” have reached a roadblock; they cannot be applied long term to
the spinal cord or brain, beneath the nervous system’s protective
envelope, otherwise known as the “dura mater,” because when nerve
tissues move or stretch, they rub against these rigid devices. After a
while, this repeated friction causes inflammation, scar tissue buildup,
and rejection.
An easy-does-it implant
Flexible
and stretchy, the implant developed at EPFL is placed beneath the dura
mater, directly onto the spinal cord. Its elasticity and its potential
for deformation are almost identical to the living tissue surrounding
it. This reduces friction and inflammation to a minimum. When implanted
into rats, the e-Dura prototype caused neither damage nor rejection,
even after two months. More rigid traditional implants would have caused
significant nerve tissue damage during this period of time.
The researchers tested the device prototype by applying their rehabilitation protocol -- which combines electrical and chemical stimulation – to paralyzed rats.
Not only did the implant prove its biocompatibility, but it also did
its job perfectly, allowing the rats to regain the ability to walk on
their own again after a few weeks of training.
“Our e-Dura
implant can remain for a long period of time on the spinal cord or the
cortex, precisely because it has the same mechanical properties as the
dura mater itself. This opens up new therapeutic possibilities for
patients suffering from neurological trauma or disorders, particularly
individuals who have become paralyzed following spinal cord injury,”
explains Lacour, co-author of the paper, and holder of EPFL’s Bertarelli
Chair in Neuroprosthetic Technology.
Flexibility of tissue, efficiency of electronics
Developing
the e-Dura implant was quite a feat of engineering. As flexible and
stretchable as living tissue, it nonetheless includes electronic
elements that 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. Finally, a fluidic microchannel enables the delivery of
pharmacological substances – neurotransmitters in this case – that will
reanimate the nerve cells beneath the injured tissue.
The
implant can also be used to monitor electrical impulses from the brain
in real time. When they did this, the scientists were able to extract
with precision the animal’s motor intention before it was translated
into movement.
“It’s the first neuronal surface implant
designed from the start for long-term application. In order to build it,
we had to combine expertise from a considerable number of areas,”
explains Courtine, co-author and holder of EPFL’s IRP Chair in Spinal
Cord Repair. “These include materials science, electronics,
neuroscience, medicine, and algorithm programming. I don’t think there
are many places in the world where one finds the level of
interdisciplinary cooperation that exists in our Center for
Neuroprosthetics.”
For the time being, the e-Dura implant has
been primarily tested in cases of spinal cord injury in paralyzed rats.
But the potential for applying these surface implants is huge – for
example in epilepsy, Parkinson’s disease and pain management. The
scientists are planning to move towards clinical trials in humans, and
to develop their prototype in preparation for commercialization.