Characterization of the Interaction of Primary Cells from the Rat Inner Ear with Polymer Films As Coatings for Cochlear Implant Electrode Surface

Gudrun Brandes1, Christoph Hadler2, Athanasia Warnecke3, Jasmin Bohlmann3, Wiebke Dempwolf2, Henning Menzel2, Thomas Lenarz3, Kirsten Wissel3
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The spiral ganglion (SG) cells prepared from the inner ear of postnatal rats represent one of the key cell culture models in hearing research. Numerous projects in hearing research aim at improving nerve-electrode-interactions by inhibiting the formation of connective tissue following cochlear implant insertion, i.e., by coating the carrier material with ultrathin polymer films for selective cell attachment. Here, we established scanning electron microscopy (SEM) and immunocytochemical (ICC) staining to enable the characterization of the interactions of fibroblasts, glial cells, and spiral ganglion neurons (SGN) growing on polymers, i.e., poly(N,N-dimethylacrylamide) (PDMAA), poly(2-ethyloxazoline) (PEtOx), and poly([2-methacryloyloxy)ethyl]trimethylammoniumchloride) (PMTA). For this purpose the primary cells dissociated from the SG of postnatal rats were cultivated for 48 h on the polymer films. ICC was used to demonstrate the preferences of cell adhesion on the polymer coatings. It could be shown that glial cells and SGN mainly adhered on PMTA monolayers forming long processes, but not on PDMAA and PEtOx films. Also, SEM imaging showed that only PMTA enabled SG neuron survival and neurite outgrowth. In conclusion, the ability of the SGN to survive and to form neurites was associated with glial cell adhesion on different coatings.