Design of a Novel Intracohlear Electrode Array Surface

Stella Ostrovsky, Chemistry, Bar-Ilan University, Ramat-Gan, Israel
Pavel Mistrik, R&D Engineer/Electrode Development, MED-EL Medical Electronics, Innsbruck, Austria
Roland Hessler ,R&D Engineer/Electrode Development, MED-EL Medical Electronics, Innsbruck, Austria
Jean-Pol Lellouche, Chemistry, Bar-Ilan University, Ramat-Gan, Israel

One of the major technological barriers in developing neural prostheses devices is the fabrication of a high-density microelectrode array (MEA) 1, which permanently eliminates the gap between the electrode array and the auditory nerve fibres, especially in the cochlea. A gapless interface is the prerequisite for a more effective and precisely targeted solution for a long-lasting restoration of the hearing function by means of a bidirectional cochlear implant.

For structuring the electrode array surface, we extended our proprietary innovative concept of "growth from the surface of oxidized ox-MWCNTs" consisting of grafting "nucleophilized" thiolated/disulphide polythiophene-decorated carbon nanotubes (CNTs) in order to produce novel conductive polyCOOH MWCNT-based polyThiophene (polyTh) matrices onto a Pt microelectrode array. For the development of corresponding conductive hybrid MWCNT-based polyTh coatings, we have fabricated an optimal conductive functional polyTh polymeric (conductive polyTh phase) matrix using variable molar ratios of both 3,4-ethylenedioxythiophene (EDOT)-EDOT-COOH (polyCOOH shell for neurotrophic factor and cysteamine attachment) Th-based monomers [EDOT/EDOT-COOH oxidative co-polymerization: 3/1 molar ratio for COOH groups modification)]. The corresponding conductive co-polymer disclosed relatively low electrical impedance with potential effective electrical interfacing with neurons, - the polycarboxylic acid functional shell will be used to covalently bind any requested biological molecule for neuron growth/activity promotion. Second, the oxidation of multi-walled carbon nanotubes (MWCNTs) from various producers has been optimized using statistically significant Design Of Experiment methods (DOE). Therefore and in the corresponding next integration step, oxidized ox-MWCNTs have been incorporated into the PolyTh conductive polymer matrix insuring effective ox-MWCNTs entrapment to produce hybrid MWCNT-CP system composites (NC). Therefore, Pt microelectrode arrays were covalently attached with the corresponding conductive NC by chemical derivatization of 50% existing COOH groups using a cysteamine moiety [NH2-(CH2)2-SH]. The corresponding thiol/disulphide-mediated multivalent grafting of such a polythiolated NC produced the requested microelectrode decoration via multivalent Pt-S quasi-covalent bonding/multiphase anchoring.

References
[1] E. Alsberg, K.W. Anderson, A. Albeiruti, J.A. Rowley, D.J. Mooney, Proc. Natl.
Acad. Sci. U. S. A. 99 (2002) 12025;