Modification of the surface of stimulating electrodes by electrospinning

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Cochlear implants (CI) are used to treat deafness and profound hearing loss. As a natural reaction to implantation, connective tissue forms shortly after implant insertion, surrounding and therefore electrically insulating the entire implant. This tissue formation leads to unpredictable stimulus propagation and increased energy consumption. In the course of deafness, auditory nerve cells (spiral ganglion neurons, SGN), targeted by electrical stimulation, also die. Previous attempts, aiming at the improvement of CI electrode integration, engaged in a general application along the electrode array. According to the current state of knowledge, a local application in the area of the contacts would be more promising approach.The present project aims at the local modification of the surface by merging the aforementioned approaches with the fiber-based processing method electrospinning. Tailor-made fiber-based manipulation of the surface properties is intended to (i) reduce the adhesion of connective tissue cells without significantly affecting the electrical properties and (ii) enable substance release (anti-inflammatory, neurotrophic) from the surfaces of the contacts. In the course of the project, medical grade silicone elastomers will be processed by electrospinning and deposited on test specimens and implants. This will be followed by a characterization of the influence of the fiber structures on the electrical properties of the electrode contacts. Potential increases in impedance should not exceed a threshold of 5 kOhm. To achieve this goal, different fiber diameters and fiber mat thicknesses are generated and characterized. Additional techniques will be developed to saturate the hydrophobic silicone fiber structures with perilymph. Therefore, aiming to utilize the interstices of the fiber mats as a reservoir for the substances to be applied by the electrode. Following successful in vitro studies on release and biocompatibility using test specimens, the methods are transferred to real electrodes carriers (implants). In addition to the development of suitable manufacturing strategies, the delamination stability of the fiber mats during insertion into the cochlea will be investigated. After completion of the project, extensive knowledge and techniques will be available, which will allow (i) structuring of electrode surfaces by using fibers (ii) functionalization of single fibers as well as the fiber construct with active agents and (iii) investigation of the influence of the mentioned measures on the electrical electrode properties as well as biocompatibility.