Bio-derived nanocarbon-based functional materials for next generation electroceutical devices – BIONAFE

Bioelectronics, is an emerging technology stemming from the bioelectroactivity of living organisms, in which a real-time monitoring of the human body can be combined with the possibility to affect its functions by electrical stimulation. The devices that treat ailments with electrical impulses, known as electroceuticals, need to be based on the state-of-the-art conducting materials with excellent electrical characteristics, able to interface with biological systems without triggering an inflammatory response. The development of electroceutical devices, particularly biomedical electrodes, must consider their surface chemistry, shape, topography, mechanical properties, and tissue response, all affecting their sensing/stimulating performance. Although conventional metal electrodes are known from their high conductivity, their applicability is limited by a foreign body reaction resulting from the chemical, biological and mechanical mismatch between an implantable device and a living tissue. This mismatch needs to be addressed by the design of a compatibilizing neural interface between the nervous system and the electrode.
The BIONAFE project aims to provide a bio-derived nanocarbon-based alternative to conventional metal electrodes, by developing a non-metallic, flexible electrode material from carbon nanotube (CNT) self-supporting films (buckypapers, BPs) modified with a biologically active conducting hydrogel layer (Figure 1) “hindering” the electrode from the immune system. Due to their unique fabrication strategy and beneficial electrical properties, self-supported, mechanically stable films made entirely of CNT BPs aggregates are promising candidates as bioelectrode materials. The fact that their porosity may be modulated during the fabrication step allows for the development of an electroactive material that can be partially penetrated by cells, which is expected to increase the tissue/electrode integrity and facilitate a charge transfer process. To further improve the biocompatibility of CNT BPs, their surface will be covered with a bioactive layer made of bio-derived molecules and macromolecules: carbohydrate derivatives, polysaccharides, as well as protein-based biopolymers, which will be modified prior to the deposition process to assure good integration with both CNT support and tissues by creating a microenvironment able to mimic the structure of tissue. Although the goal of the BIONAFE project is to develop a bio-derived nanocarbon-based electrode material suitable for a wide range of target tissues, as a proof-of-concept we have selected bioelectrodes used for neuromodulation. Therefore, biological properties of as-developed functional materials will be evaluated in vitro with human-derived cell lines (SH-SY5Y, U87), as well as ex vivo with mice embryonic co-culture derived from midbrain, in terms of cytotoxicity, ability to promote cell integration, and to stimulate neural activity. Biocompatibility of selected coatings will be evaluated under in vivo conditions, and will include the analysis of hemocompatibility, intradermal reactivity, effects of local implantation, as well as chronic and subchronic cytotoxicity.
We expect that the developed non-metallic, bioactive, highly conducting and flexible electrodes will serve as advantageous materials for the next generation electroceutical devices, which will be able to overcome the limitations of currently used conventional metal electrodes through improved tissue/electrode integration and minimized foreign body reaction. By the use of as-developed electrode materials, electro-therapies are expected to become more efficient. Based on the extend of preliminary experiments and expertise of the project team, we expect to bring the technology readiness level from stage 2 to stage 4.