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A mimetic implant for low perturbation, stable stimulation and recording of neural units inside the brain.

Periodic Reporting for period 3 - BRAIN MICRO SNOOPER (A mimetic implant for low perturbation, stable stimulation and recording of neural units inside the brain.)

Reporting period: 2018-08-01 to 2020-01-31

To deal with the problematic of Central Nervous System dysfunction and associated pathologies that can be traumatic (eg, accidents, vascular lesions), psychological (eg, autism, depression, anorexia, bipolar disorder), neurodegenerative (eg Parkinson's, Alzheimer's, Huntington's) or tumor-related (eg glioblastoma, medulloblastoma neuromas), the development of brain implants is crucial to better decipher neuronal information and intervene very thinly on neural networks using microstimulation. This project aims to address two major challenges: to achieve the realization of a highly mechanically stable implant, allowing long term connection between neurons and microelectrodes and to provide neural implants with a high temporal and spatial resolution. To do so, the present project will develop implants with structural and mechanical properties that resemble those of the natural brain environment. According to the literature, using electrodes and electric leads with a size of a few microns allows for a better neural tissue reconstruction around the implant. Also, the mechanical mismatch between the usually stiff implant material and the soft brain tissue affects the adhesion between tissue cells and electrodes. With the objective to implant a highly flexible free-floating microelectrode array in the brain tissue, we will develop a new method using micro-nanotechnology steps as well as a combination of polymers. Moreover, the literature and preliminary studies indicate that some surface chemistries and nanotopographies can promote neurite outgrowth while limiting glial cell proliferation. Implants will be nanostructured so as to help the neural tissue growth and to be provided with a highly adhesive property, which will ensure its stable contact with the brain neural tissue over time. Implants with different microelectrode configurations and number will be tested in vitro and in vivo for their biocompatibility and their ability to record and stimulate neurons with high stability. This project will produce high-performance generic implants that can be used for various fundamental studies and applications, including neural prostheses and brain machine interfaces
The five-person team working on the project have finalized main aspects about the implant fabrication, assembling with electronics, in vitro biocompatibility studies and surgical method for the implant insertion. This last step was risky, given the tiny dimensions of the soft leads of the implant. We are now able to encapsulate them within a biodegradable material that facilitate their implantation and then gradually resorb. We can also use a stiff shuttle to which the implant is stuck using PEG and as this PEG dissolves in tissues, we can remove the shuttle and let the implant into the cortical layers. We are now moving on to the pre-clinical studies. In parallel, we are trying to incorporate the materials that currently offer the best performance and so obtain micro-nanostructured electrodes made with platinum or doped diamond, for example.
Thanks to the flexible and extremely fine wires and the micro-nanostructured electrodes, we hope that the implant will be better tolerated, which will minimize the formation of scar tissue. In addition, the electrodes will have a greater surface of exchange, which should improve their ability to record neuronal signals in comparison with those currently available which have zero or low surface roughness.
This leads us to think that these electrodes could open up new perspectives. The currently existing devices enable quadriplegic individuals, after a lot of practice, to move an articulated arm that mimics the movements they are thinking about. With better performing implants and electrodes, we could conceive of capturing and carrying out more complex brain commands. It could also allow a more precise pattern of neural stimulation which is necessary to improve some brain pathology treatments.