Biomaterialien bei Cochlea-Implantaten

Abstract

Cochlear implants (CI) represent the "gold standard" for the treatment of congenitally deaf children and postlingually deafened adults. Thus, cochlear implantation is a success story of new bionic prosthesis development. Owing to routine application of cochlear implants in adults but also in very young children (below the age of one), high demands are placed on the implants. This is especially true for biocompatibility aspects of surface materials of implant parts which are in contact with the human body. In addition, there are various mechanical requirements which certain components of the implants must fulfil, such as flexibility of the electrode array and mechanical resistance of the implant housing. Due to the close contact of the implant to the middle ear mucosa and because the electrode array is positioned in the perilymphatic space via cochleostomy, there is a potential risk of bacterial transferral along the electrode array into the cochlea. Various requirements that have to be fulfilled by cochlear implants, such as biocompatibility, electrode micromechanics, and although a very high level of technical standards has been carried out there is still demand for the improvement of implants as well as of the materials used for manufacturing, ultimately leading to increased implant performance. General considerations of material aspects related to cochlear implants as well as potential future perspectives of implant development will be discussed.

Nanomedizin in der HNO-Heilkunde – ein Ausblick

“…Des Weiteren wird auch die Beschichtung mit anti-infl ammatorischen Nanopartikeln, insb. Silber-Nanopartikeln, als vielversprechend eingeschätzt [ 17 ] . Eine verbesserte Akzeptanz und erhöhte Lebensdauer eines so behandelten Implantats konnte bereits für Hüftendoprothesen gezeigt werden [ 18 ] .…”

Development of Neuronal Guidance Fibers for Stimulating Electrodes: Basic Construction and Delivery of a Growth Factor

“…The insertion of a cochlear implant (CI) is a well-established method of rehabilitating severe to profound hearing loss by electrical stimulation of the remaining auditory neurons, the spiral ganglion neurons (SGNs), in this way bypassing damaged or lost hair cells ( Lenarz, 1998 ). Since SGNs are the target cells that are activated by the CI electrode, their progressive degeneration after deafening due to lack of stimulation and/or the general pathological situation leads only to limited benefit ( Duan et al, 2002 ; Swan et al, 2008 ; Stöver and Lenarz, 2009 ; Shibata et al, 2011 ). The provision of drugs and neurotrophic substances may increase the survival and function of the SGNs and help in reestablishing a healthy cochlear milieu ( Pfingst et al, 2015 ; Rask-Andersen and Liu, 2015 ; Schilder et al, 2019 ).…”

“…Due to this gap, electrical signals with stronger intensity have to be used and spatial spreading of the stimulation signal occurs ( Wilson, 2017 ). This leads to an overlap in the addressed SGNs and reduces focused neuronal stimulation which in turn leads to discriminated frequency resolution ( Stöver and Lenarz, 2009 ; Shibata et al, 2011 ; Li H. et al, 2017 ; Yilmaz-Bayraktar et al, 2020 ). In a more favourable situation, the neurites resprouting from the SGNs would overcome this gap to get into close contact with the electrode in order to achieve a much more specific electrical stimulation.…”

“…Different growth factors like the brain-derived neurotrophic factor (BDNF), the glial cell line-derived neurotrophic factor (GDNF) or the fibroblast growth factors (FGFs) were shown to be involved in the maintenance and development of SGNs in the cochlea ( Duan et al, 2002 ; Swan et al, 2008 ; Stöver and Lenarz, 2009 ; Shibata et al, 2011 ; Nacher-Soler et al, 2019 ). From rodent experiments it is known that a lack of BNDF signaling leads to progressive hearing loss ( Singer et al, 2014 ) and that reduced levels of BDNF in the cochleae are observed in mice with presbyacusis ( Rüttiger et al, 2007 ).…”

Exploiting Routine Clinical Measures to Inform Strategies for Better Hearing Performance in Cochlear Implant Users

“…Although fibrosis can foul the implant and impair its function, it is also beneficial in mechanically fixing the array within the cochlea. This helps create a seal to prevent both loss of perilymph and infiltration of bacteria from the middle ear (Stöver and Lenarz, 2009). A healthy inflammatory response to an injury comprises successive waves of pro- and anti-inflammatory chemokines and cytokines, controlled cellular migration to the wound site, with eventual resolution of inflammation and controlled apoptosis of recruited cells accompanied by wound repair and remodeling.…”