Last year, researchers at the Ecole polytechnique federale de Lausanne, Switzerland, successfully demonstrated a system that. Using a system of electrical and chemical stimulation, the rats -- whose spinal cords had been completely severed -- were able to once again move their hind limbs.
The technology is now one step closer to clinical human trials, with a flexible implant specifically designed to integrate with the patient's spine, minimising the risk of rejection and further damage.
The implant, called e-Dura, is designed to be implanted directly onto the brain or spinal cord, underneath the dura mater, the membrane that encloses the brain and spinal cord. Its mechanical properties -- flexible and stretchy -- are almost identical to those of the living tissue enclosing it, vastly reducing the risk of inflammation, friction and abrasion.
This is in direct contrast to "surface" implants. These are rigid, which causes frictional inflammation on the surrounding tissues when implanted long-term.
The team at EPFL has tested the implant in rats and has found that, even after two months, there was no tissue damage or rejection -- in addition, of course, to allowing the rats to walk. This has demonstrated that the implant is both capable of performing its function and compatible with long-term implantation.
"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," said study co-author and EPFL Bertarelli Chair in Neuroprosthetic Technology Stéphanie Lacour. "This opens up new therapeutic possibilities for patients suffering from neurological trauma or disorders, particularly individuals who have become paralysed following spinal cord injury."
The flexible silicon implant is covered in cracked gold conduction tracks that stretch with the silicon, while the electrodes, a new composite made of silicon and platinum microbeads, can be pulled in any direction. These conduction tracks and electrodes convey electrical current to the spinal cord, much as the brain does. Meanwhile, a fluidic microchannel in the implant delivers neurotransmitting drugs to reanimate the nerve cells beneath the injured tissue.
While this operates in concert to circumvent the injured site on the spine, allowing the patient -- theoretically -- to use their limbs, it can also be used to monitor electrical impulses from the brain in real-time, allowing the researchers to accurately gauge the patient's intention to move before the signal is translated into motion.
The human trials may start as early as June of this year, at a special facility called the called the Gait Platform, housed in the University Hospital of Lausanne, Switzerland.
The full study, "Electronic dura mater for long-term multimodal neural interfaces", can be found online in the journal Science.