Development of a specially tailored local drug delivery system for the prevention of fibrosis after insertion of cochlear implants into the inner ear

A cochlear implant (CI)-associated local drug delivery system based on dexamethasone (DMS) was developed with the purpose to inhibit the growth of fibrotic tissue which influences the signal transmission from the CI to the neurons of the inner ear. For the realization of a targeted DMS delivery the following concepts were combined: modification of the silicone-based electrode carrier by incorporation of DMS and a DMS-containing polymeric coating chemically attached on the surface of the electrode carrier. It was demonstrated that the coated CI showed a high coating stability in a simulated implantation procedure. The in vitro drug release studies in a quasi-stationary model revealed a faster DMS release in the initial phase originating from the DMS-containing coatings and then a lower and sustained DMS release originating from the DMS-loaded silicone carrier. The performed in vitro biocompatibility study confirmed that the released DMS was non-toxic for cultured spiral ganglion cells.