Bridging the electrode–neuron gap: finite element modeling of in vitro neurotrophin gradients to optimize neuroelectronic interfaces in the inner ear

Current advances in biomaterials for inner ear cell regeneration

“…As SGN degeneration occurs inevitably after HC damage (Kanzaki et al, 2002), an "electrode-neuron gap, " which exists between CI electrodes and the membranes at the terminal of SGNs neurites (Frick et al, 2017), and is usually produced after CI operation and considered to be the most remarkable obstacle in improving CI performance (Nella et al, 2022). The application of biomaterials can eliminate such "electrode-neuron gap" to a certain extent.…”

“…For example, a resist pattern on the surface of nanocrystalline diamond has been designed to arrange specific neural interfaces, thereby creating independent electrical stimulation signals for individual neuron on the CI electrode array (Cai et al, 2016). Another research group managed to eliminate the "electrodes-neuron gap" by establishing a "neuro-regenerative nexus, " a concept that was first proposed in 2022 by Kevin et al The "neuro-regenerative nexus" refers to the biological interface provided by transplanted hPSC-derived ONPs, the two neurites of which are expected to connect to native SGNs and CI electrodes, respectively (Nella et al, 2022). To provide more precise connections between the SGNs and the electrodes, researchers used PODS ® crystals for continuous delivery of growth factors and hydrogel to provide a stem cell niche for ONPs after transplantation into the inner ear , and a device with microgrooves to control the gradient of growth factors (Nella et al, 2022).…”

“…Currently, stem/progenitor cell-based inner ear cell regeneration including inner ear organoids in vitro (Pouraghaei et al, 2020;Hocevar et al, 2021), elimination of the electrode-neuron gap after CI (Mattotti et al, 2015;Cai et al, 2016;Nella et al, 2022), and attempts at inner ear regeneration in vivo (Zhong et al, 2016; are some of the primary directions for inner ear regeneration research. Among these studies, the application of biomaterials and developments in bioengineering have also provided strategies to overcome the obstacles in inner ear cell regeneration (Brant et al, 2021).…”