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Neuroscience applications of organic electronic devices| old_uid | 13704 |
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| title | Neuroscience applications of organic electronic devices |
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| start_date | 2014/03/27 |
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| schedule | 11h30 |
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| online | no |
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| location_info | salle des conférences |
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| details | Séminaire CRNL-WAKING |
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| summary | Electrophysiological recordings and imaging techniques brought considerable information about brain function and dysfunction in neurological disorders such as epilepsy. Improving recording devices would further our understanding at the basic science level and would ultimately be beneficial to patients. Major limitations of current electrodes that are in direct contact with brain tissue include their invasiveness, their poor biocompatibility, their rigidity and a suboptimal signal-to-noise ratio. In addition, it would be desirable to measure simultaneously molecular signals, in particular actors of metabolism (such as glucose), which are measured with imaging modalities. Altered metabolism is commonly found in neurological disorders, including epilepsy. The coupling between the electrical activity of neurons and metabolism is still poorly understood in vivo. The goal of this work was to provide technological solutions to such challenges in the context of epilepsy. We present the development, characterization and in vivo validations of different types of electrodes based on organic electronics.
We used parylene-c as a FDA-approved biocompatible substrate. This allowed us to generate 4 ºm thick, totally flexible but resilient grids, thus solving the challenge of invasiveness, rigidity and biocompatibility. In order to improve the signal-to-noise ratio, recording sites were made of the highly conductive polymer PEDOT:PSS. The grid was tested on the surface of the cortex of rats in vivo. The quality of the signals recorded by PEDOT:PSS sites was better than that obtained with conventional gold contacts.
Going a step further, we made the recording site as an organic electrochemical transistor, which enables local amplification of signals. The grid was tested in vivo in a genetic model of epilepsy. The signal-to-noise ratio was increased by a factor of 10.
These grids are designed to be laid on the surface of the cortex. Many neuroscience applications require recordings neurons and field potentials in situ with penetrating electrodes. Current systems are invasive and non-biocompatible, triggering an inflammatory response that limits their use. Penetrating electrodes (4 and 40 ºm thick) made of parylene did not induce a strong inflammatory response after one month implantation in rats.
Finally, we functionalized PEDOT:PSS sites with glucose oxidase to measure glucose. The enzyme was grafted on nanobrushes, which themselves were grafted on PEDOT:PSS ensuring optimal concentration. Compared to conventional devices, the glucose sensor showed unsurpassed stability and sensitivity in vitro. The device remains to be tested in vivo. The next step will be to engineer electrodes able to record both electrophysiological and molecular signals.
In conclusion, organic electronics appears to be a promising technological solution to the limitations of current systems designed to record the electrical and molecular activity of the brain. They are easy to build and cheap. They should replace actual systems not only for patient s care but also in research laboratories. |
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| responsibles | Béranger, Rossetti |
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