BioEPIC project

BioEPIC

Abstract: BioEPIC stands for BioElectroactive Polymers for Interfacing the Cortex. In BioEPIC we explored electrode materials, such as the conducting polymer poly(3,4- ethylene dioxythiophene) (PEDOT), to address challenges of intracortical neural implants. PEDOT coatings allows features, such as controlled delivery, to be integrated on implants without complex components adding to cost and weight of the system. In addition, PEDOT electronic properties can be merged with those of a hydrogel, tuning mechanical and biochemical properties further. In BioEPIC we have demonstrated that excellent recording and stimulation capability can be combined with biological functionality and stability, even under chronic conditions.

A main goal in BioEPIC was to mere PEDOT electrodes with a charged drug, the corticosteroid Dexamethasone (Dex). The charged version of Dex, Dex-P, can be included as counter ion in PEDOT. When a current is driven over the coated microelectrode, an exact amount of Dex is released into surrounding tissue. This way PEDOT films can be used as an on-demand drug release system, enabling biochemical control of the implant microenvironment.

• C. Boehler, F. Oberueber and M. Asplund, "Tuning drug delivery from conducting polymer films for accurately controlled release of charged molecules." Journal of Controlled Release , 304, 2019: 173–180, doi:10.1016/j.jconrel.2019.05.017 >LINK<
   
• C. Kleber, K. Lienkamp, J. Ruhe and M. Asplund. "Electrochemically Controlled Drug Release from a Conducting Polymer Hydrogel (PDMAAp/PEDOT) for Local Therapy and Bioelectronics. " Adv Healthc Mater, 8, 2019:e1801488, doi:10.1002/adhm.201801488 >LINK<
   
• C. Boehler, C. Kleber, N. Martini, Y. Xie, I. Dryg, T. Stieglitz, U.G. Hofmann, M. Asplund, "Actively controlled release of Dexamethasone from neural microelectrodes in a chronic in vivo study", Biomaterials, 129, 2017: 176–187, doi:10.1016/j.biomaterials.2017.03.019. >LINK<
   
• C. Boehler, M. Asplund, "A detailed insight into drug delivery from PEDOT based on analyticalmethods: Effects and side effects." Journal of Biomedical Materials Research Part A, 103, 2015: 1200–1207,doi:10.1002/jbm.a.35252.  >LINK<
   
• C. Boehler, F. Güder, U. M. Kücükbayrak, M. Zacharias, and M. Asplund, "A Simple Approach for Molecular Controlled Release based on Atomic Layer Deposition Hybridized Organic-Inorganic Layers," Scientific Reports, 6,2016: 619574, doi:10.1038/srep19574. >LINK<
   
• M. Asplund, C. Boehler, T. Stieglitz, "Anti-inflammatory polymer electrodes for glial scar treatment." Frontiers in Neuroengineering, 7, 2014: doi:10.3389/fneng.2014.00009.>LINK<
   

To make PEDOT-electrodes stable over long usage times it is crucial to have a solution for binding the PEDOT-film to the metallic substrate. We developed a method that solves this by adding a layer of sputtered iridium oxide (SIROF) in-between the platinum base and the added PEDOT film. The two materials form an extremely stable complex.

• C. Boehler, F. Oberüber, S. Schlabach, T. Stieglitz, M. Asplund, "Long-term stable adhesion for conducting polymers in biomedical applications: IrOx and nanostructured platinum solve the chronic challenge", ACS Applied Materials & Interfaces, 9, 2017: 189–197, doi:10.1021/acsami.6b13468 >LINK<
   

• C. Boehler, F. Oberueber, T. Stieglitz, and M. Asplund, „Iridium Oxide (IrOx) serves as adhesion promoter for conducting polymers on neural microelectrodes”,  Proc. of the 7th International IEEE/EMBS Conference on Neural Engineering (NER), 2015, Montpellier: 410–413, doi:10.1109/NER.2015.7146646. > LINK<
   

Acknowledgement: We gratefully acknowledge the funding of BioEPIC by the Cluster of Excellence BrainLinks-BrainTools, funded by the German Research Foundation (DFG, grant number EXC 1086).