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Nanostructured and biofunctionalized coatings for microscale electrodes: bringing cutting edge materials science to microsystems engineered implants

Christian Boehler1, 2, 3, Carolin Kleber2, 3, Stefanie Heizmann2, 3, Patrick Ruther2, 3, Ulrich Hofmann2, 4, Ulrich Egert2, 3, 5, Juergen Ruehe3, Thomas Stieglitz2, 3 and Maria Asplund1, 2, 3
  • 1 Albert-Ludwigs University, Freiburg Institute for Advanced Studies (FRIAS), Germany
  • 2 Albert-Ludwigs University, BrainLinks-BrainTools Cluster of Excellence, Germany
  • 3 Albert-Ludwigs University, Department of Microsystems Engineering (IMTEK), Germany
  • 4 Unversity Medical Center, Department of Neurosurgery, Germany
  • 5 Albert-Ludwigs University, Bernstein Center Freiburg, Germany

Innovative electrode materials can make neural interfaces do more than recording neural signals. The ideal electrode would work efficiently for stimulation and recording but in addition have the power to support new modes of interactions with tissue in parallel to the purely electrical measurements. The porous matrix of a PEDOT electrode coating acts as a close to ideal signal transducer for ionic to electronic signals, but furthermore offers a convenient route for biofunctionalization. Features such as controlled delivery can be added without the cost of complex components adding to weight and overall dimensions of the implant.

We here show results on how such delivery functionality can be implemented on flexible shaft electrodes for simultaneous intracortical recordings and delivery of anti-inflammatory drugs. Furthermore, we show how similar techniques can be used to implement recording microelectrodes with inbuilt neuronal labelling functionality. By anchoring these layers on iridium oxide it is possible to stabilize the systems and enable delivery with high control at multiple occasions and over time frames up to months in vivo. By forming hybrid materials, composites and layered films, it is possible to further increase the loading capacity and make the delivery functionality more generally applicable to drugs of various size and charge. Over limited time periods a thick porous electrode can even support direct current stimulation in the form of ionic current and without producing electrochemical by-products.

A new and interesting class of PEDOT based conducting hydrogels have the potential to bring biofunctionalized electrodes to the next level. By combining PEDOT with the hydrogel P(DMAA-co-pss-co-BP) we present a conducting composite which extends the possibilities to form increasingly complex coatings, and yet matches the fairly strict boundary conditions set by the microelectronic neural interface. Firstly, the hydrogel can be photolitographically patterned and thereby confined to the microelectrode site. Secondly, it can be covalently linked to the substrate electrode surface thereby ensuring a stable interface. Last, but not least, electropolymerization though the charged layer forms a truly interpenetrating conducting network with the electrochemical characteristics of a PEDOT hydrogel hybrid. We suggest that such hybrids will be an important building block for equipping future microelectrodes with the additional functionality to chemically manipulate or sense their microenvironment in vivo.

This work was partly supported by BrainLinks-BrainTools, Cluster of Excellence funded by the German Research Foundation (DFG, grant number EXC 1086).

Keywords: Hydrogel, biomaterial, polymer, Biofunction

Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016.

Presentation Type: New Frontier Oral

Topic: Nano-structured materials for unique functions

Citation: Boehler C, Kleber C, Heizmann S, Ruther P, Hofmann U, Egert U, Ruehe J, Stieglitz T and Asplund M (2016). Nanostructured and biofunctionalized coatings for microscale electrodes: bringing cutting edge materials science to microsystems engineered implants. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.00595

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Received: 27 Mar 2016; Published Online: 30 Mar 2016.