Cochlear implants have evolved to become the treatment of choice for severely hearing-impaired patients.
Speech signals are picked up by a microphone, processed and then delivered to the stimulating electrodes (the current
maximum number being 22) that are placed on an electrode array implanted into the scala tympani of the cochlea. The
target cells of electrical stimulation, the spiral ganglion cells (SGCs), are located some distance away in the central axis of
the cochlea. SGCs start to degenerate after the onset of deafness. Additionally, fibrous tissue is formed around the electrode
array after implantation. If cochlear implants are to deliver sound that is closer to natural hearing, the number of independent
stimulation channels has to be increased. Optimization of the interface between the electrode array and the surrounding
tissue is, therefore, the focus of current research. Promising approaches relating to cells, micro- and nanosystems
will be reviewed.
Biomaterial, cochlear implant, drug delivery, electrode-neural interface, inner ear, neurotrophic factor, surface pattern
Department of Otolaryngology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany