Silk Fibroin Protein Coating – An Option for Electrode Gapless Interface to Auditory Neurons

Introduction:

Cochlear implants (CI) could restore functional hearing in patients with severe or profound hearing loss. Despite continuous development, anatomical gap between auditory neurons and electrodes lead to low frequency resolution and high energy consumption. Therefore, clinical experiment put great interest to modify the carrier material of the electrodes to close this anatomical gap, and hope to guide the growth of neuron dendrites closer to CI electrodes through targeted slow release of neurotrophins. Silk fibroin protein-based microspheres provide new options for drug delivery and have the capacity for uptake and release of neurotrophins.

Methods and Results:

Silk fibroin protein microspheres with hydrogel were coated onto CI electrodes and loaded with BDNF (brain derived neurotrophic factor). Characterization of microsphere and coatings using Scanning Electron Microscopy (SEM) and Transmission Electron Microscope (TEM). In-vitro release profiles of BDNF were investigated by an enzyme-linked immunosorbent assay (ELISA). Neonatal C57 rats (P0 – 2) were used for spiral ganglion neuro (SGN) dissection. Using coted electrode co-culture with SGNs. SEM observations also revealed neural extensions anchoring the coated electrode surface. A time-lapse video recording of 24h showed the neurites move toward the thicker coated CI electrode.

Conclusion:

Neurotrophin delivery through silk fibroin protein microspheres coating is a possible way to close anatomical gap between auditory neurons and electrodes. The gapless interface between auditory neurons and cochlear implant electrode arrays led to lower stimulation thresholds, by overcoming this gap, selective neural activation and the fine hearing for CI users become possible.

Publication History

Publication Date:
23 April 2019 (online)