ELECTRONIC DURA MATER (E-DURA)

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1 ELECTRONIC DURA MATER (E-DURA) JESSE P. CARON UNIVERSITY OF RHODE ISLAND BME 281

2 BACKGROUND There are currently about 5.6 million people living with some form of paralysis in the United States. Of that number, approximately 1.27 million are the result of a spinal chord injury. The stiffness of standard circuitry hinders the potential use and long-term performance of implantable neuro-prostheses. Electronic dura mater (e-dura) is a soft, stretchable implant designed to mimic the viscoelastic properties and withstand the dynamic motion of neural tissue and the central nervous system.

3 HISTORY 1905-John Newport Langley coins the phrase parasympathetic nervous system Rita Levi-Montalcini and Stanley Cohen isolate nerve growth factor Arvid Carlsson, Paul Greengard and Eric Kandel earn Nobel prize for discoveries involving signal transduction in the nervous system Research conducted on viscoelastic properties of glial cells and neurons in the central nervous system chemical injection treatment restores voluntary locomotion after paralyzing spinal injury.

4 APPLICATION E-dura is a soft neuro-spinal implant designed to apply drug delivery and electrical stimulation directly to the spinal tissue. A small incision is made and the device is implanted beneath the dura mater. The connector is secured by a vertebral orthosis. The devices were implanted in healthy adult rats, then subsequently those which had received a paralysis inducing contusion. Therapy continued for six weeks following implantation. Electrode impedance was measured over 5 weeks, remaining consistent for the duration. Daily drug injections were conducted and testing of the microfluidic channels following explantation showed that the chemotrodes maintained functionality throughout the experiment.

E-dura easily conformed to the surface of the spinal tissue and produced little to no inhibition to range of motion.

5 RESULTS Bipedal locomotion therapy was conducted with robotic support after 3 weeks of rehabilitation Shown here are test results both with and without electrochemical stimulation. E-dura easily conformed to the surface of the spinal tissue and produced little to no inhibition to range of motion. By method of contrast a stiffer implant was designed (25 μm polyimide film) and tested, those with the stiffer implant displayed marked inhibition to motor function which emerged 1 to 2 weeks after implantation.

6 LIMITATIONS To demonstrate robustness the soft implant was stretched to 20% strain over 1 million cycles. The device maintained complete functionality, showing minimal reduction in impedance over time. This suggests that e-dura could potentially survive mechanically for up to 10 years in a patient. Simulations indicate that conformity between implant and spinal tissue is critical to maintaining long-term biocompatibility.

7 FUTURE Additional technological developments will be required for the integration of soft implants with greater electrode density, implantable pumps for drug delivery and embedded electronics for real-time analysis and subsequent modulation. E-dura displays great potential for prolonged therapy. In addition its flexibility and size make it convenient for installation through minimal area of surgical operation.

8 REFERENCE Garcia, N. (2012, April 3). Spinal cord stimulation. Retrieved October 15, 2016, from International Neuromodulation Society, Lu, Y.-B., Franze, K., Seifert, G., Steinhäuser, C., Kirchhoff, F., Wolburg, H., jkaes (2006). Viscoelastic properties of individual glial cells and neurons in the CNS. Proceedings of the National Academy of Sciences, 103(47), doi: /pnas Minev, I. R., Musienko, P., Hirsch, A., Barraud, Q., Wenger, N., Moraud, E. M., P. (2015). Electronic dura mater for longterm multimodal neural interfaces. Report, 347(6218), doi: /science Paralysis statistics. (2016). Retrieved October 15, 2016, from Christopher & Dana Reeve Foundation, van den Brand, R., Heutschi, J., Barraud, Q., DiGiovanna, J., Bartholdi, K., Huerlimann, M., Zurich, (2012). Restoring voluntary control of Locomotion after paralyzing spinal cord injury. Report, 336(6085), doi: /science Vanfleteren, J., Chtioui, I., Plovie, B., Yang, Y., Bossuyt, F., Vervust, T., Vandecasteele, B. (2014). Arbitrarily shaped 2.5D circuits using Stretchable interconnections and Embedding in thermoplastic polymers.procedia Technology, 15, doi: /j.protcy

Electronic dura mater for long-term multimodal neural interfaces

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