Flexible electronics for spinal implants

An implant made of silicone and gold wires is as stretchy as human tissue. Credit: EPFL

Researchers know more and more about the way the nervous system communicate and are capable of flanking it, and replace some faulty connections, with the help of a computer to modulate electrical impulses.

However, our body is soft and tissues continuously move, stretch, compress. Inserting a rigid implant, such as one made of wires to bring the signals to the right spot, works only for a limited amount of time and often may cause a damage to the target and surrounding tissues.

Here comes the result from the Ecole Polytechnique Federal de Lausanne: a bendable implant with the same degree of softness of the "durra madre", the tissue covering our brain.

Gregoire Courtine, one of the lead researchers, was able to insert an implant in the damaged spinal cord of a rat restoring its walking (that was stopped by an interruption to the nerves in the spine) but after a while the implant failed because its rigidity was not capable of withstanding the movement of the surrounding tissues.

By teaming up with Stephanie Lacoure, and electrical engineer, they were able to create a soft silicon based implant, called e-dura, containing stretchable gold wires, rubbery electrodes flecked with platinum and microtubes to dispense drugs.

They tested the new implant on rats with damaged spine and after two months they saw a very good acceptance of the implant by tissue. 

Clearly the ultimate goal of this research is to restore a damaged spine in humans, but there is still a long way to go.

Electrical stimulation made possible by the implant, as shown by the rats, can send signals to interrupted nerves but these are not specific signals. The electrical stimulation affects many nerve fibres at a time and you don't get a proper message across. Your legs wold move but not in the coordinated way that is required to walk. To do that much more work is needed and technologies like protonic chips are needed. These allows communication using ions, not electrons, and ions can be directed to specific cells without impacting surrounding ones.

In spite of the huge difficulties I am confident that it is just a matter of time, that possibly in the next decade we will be able to repair spinal injuries as we are repairing a broken femur today.

Author - Roberto Saracco

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