A living electrode construct for incorporation of cells into bionic devices

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Biomaterials for 3D Cell Biology Research Letter

A living electrode construct for incorporation of cells into bionic devices Josef Goding, Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia; Department of Bioengineering, Imperial College London, London, UK Aaron Gilmour, Ulises Aregueta Robles, Laura Poole-Warren, Nigel Lovell, and Penny Martens, Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia Rylie Green, Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia; Department of Bioengineering, Imperial College London, London, UK Address all correspondence to Rylie Green at [email protected] (Received 31 March 2017; accepted 9 June 2017)

Abstract A living electrode construct that enables integration of cells within bionic devices has been developed. The layered construct uses a combination of non-degradable conductive hydrogel and degradable biosynthetic hydrogel to support cell encapsulation at device surfaces. In this study, the material system is designed and analyzed to understand the impact of the cell carrying component on electrode characteristics. The cell carrying layer is shown to provide a soft interface that supports extracellular matrix development within the electrode while not significantly reducing the charge transfer characteristics. The living layer was shown to degrade over 21 days with minimal swelling upon implantation.

Introduction To date, commercial neuroprosthetic implants use metallic electrodes to directly inject electrical charge and stimulate neural tissue.[1] This process involves moving from electron flow in the device to ion flow in the tissue. It is the ions in the biologic environment which enable depolarization and generation of action potentials in the neural tissue. As a result, the target tissue, which is often injured or diseased, is subjected to electrical fields that raise the extracellular voltage.[2] This process has significant impacts on the local biologic environment, including cell electroporation, generation of undesirable chemical species, localized pH changes, and subsequent inflammatory reactions, as well as electrode degradation.[1,2] The consequences of this mode of operation is that chronic frustration of the wound-healing process produces a scar tissue reaction, which encapsulates the implant and electrically isolates it from the target tissue.[3,4] As a result, the amount of charge required to activate the target tissue often increases over time and the implant loses efficacy.[5,6] Rather than relying on unwieldy metal electrodes and direct charge injection, tissue-engineered bioelectronics will use cells embedded within devices to provide a natural mode of physiologic tissue activation.[7] This “living electrode” concept, shown in Fig. 1, is designed to seamlessly integrate living neural cells with electrodes through modification of electrode coating technologies. This approach to creating living bioelectronics draws upon the knowledge from imp