Nerve-on-a-chip
Swiss researchers from the Federal Polytechnic School of Lausanne, working under the guidance of Professor Stephanie Lacour, have developed a miniature electronic platform (chip) to stimulate peripheral nerve fibers and register the electrical impulses emitted by them. Providing fast modulation and registration of nerve activity with a high signal-to-noise ratio, the platform opens up new prospects for the use of microchips to improve the results of neuroprosthetics.
Neuroprostheses – implants equipped with multi–contact electrodes - can take over certain functions of damaged nerves. Experts hope that over time their use will allow to restore the sense of touch in patients with amputated limbs, to return to paralyzed patients the ability to walk by stimulating the spinal cord, as well as to suppress excessive nerve activity in people suffering from chronic pain syndrome. Stimulation of nerves in the right place and at the right time is both a guarantee of the effectiveness of therapy and an extremely difficult task due to the inability of implants to accurately register nerve activity. According to the authors, the human brain emits and receives millions of nerve impulses, whereas the patient is usually implanted with only about a dozen electrodes, which are not enough to reproduce complex patterns of information exchange in the nervous system.
The authors have developed a "nerve-on-a-chip" platform that allows to stimulate the explanted nerve fibers and register the impulses emitted by them in the way that a neuroprosthesis can do. To do this, electrodes and explanted nerve fibers are placed inside microchannels that accurately reproduce the architecture, maturity and functioning of living tissue.
The functionality of the platform was tested on nerve fibers explanted from the spinal cord of rats, to which different strategies of stimulation and inhibition of nervous activity were applied. Usually laboratory experiments are carried out on cultures of neurons that do not allow reproducing the diversity of nerve cells in living tissue and, accordingly, its properties. Moreover, traditionally used extracellular complexes of microelectrodes do not allow recording the activity of individual nerve cells in culture.
The "nerve-on-a-chip" platform created by the authors is manufactured in a "clean room" for two days and allows recording hundreds of nerve impulses with a high signal-to-noise ratio. However, its most important property is its ability to register the activity of individual nerve cells.
The researchers used their platform to test the effectiveness of the photothermal method of inhibiting the activity of neurons. (Suppression of neuronal activity can be used as therapy for chronic pain syndromes, for example, neuropathic pain and so-called phantom pain in amputated limbs.)
To do this, a layer of photothermal semiconductor polymer P3HT was applied to certain electrodes of the chip:PCBM, warming up under the influence of light. The sensitivity of the electrodes made it possible to measure the difference between the activity levels of different explanted nerve fibers. It was found that heating predominantly blocks the activity of the thinnest nerve fibers formed by sensitive neurons or nociceptors – pain receptors that cause pain. At the next stage of the work, the authors plan to study the described inhibitory effect in animal experiments, for this purpose an implant containing a heating polymer will be placed around the nerve fiber.
In addition, the new platform was used to improve the geometry and placement of recording electrodes for the subsequent development of an implant that promotes regeneration of peripheral nerves. Processing information about recorded nerve impulses using a special algorithm will allow calculating the speed and direction of propagation of nerve impulses and thus determine which nerve they are emitted by: sensitive or motor. This will allow engineers to develop double-acting implants to improve control over prosthetic limbs.
Article by Sandra Gribi et al. A microfabricated nerve-on-a-chip platform for rapid assessment of neural conduction in explained peripheral nerve fibers is published in the journal Nature Communications.
Evgenia Ryabtseva, portal "Eternal Youth" http://vechnayamolodost.ru based on the materials of École polytechnique fédérale de Lausanne: Nerve-on-a-chip platform makes neuroprosthetics more effective.