Promoting neurite outgrowth from spiral ganglion neuron explants using polypyrrole/BDNF-coated electrodes
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Date
2009-10
Journal Title
Journal ISSN
Volume Title
Publisher
Wiley Periodicals
Abstract
Release of neurotrophin-3 (NT3) and brain-derived neurotrophic factor (BDNF) from hair cells in the cochlea is essential for the survival of spiral ganglion neurons (SGNs). Loss of hair cells associated with a sensorineural hearing loss therefore results in degeneration of SGNs, potentially reducing the performance of a cochlear implant. Exogenous replacement of either or both neurotrophins protects SGNs from degeneration after deafness. We previously incorporated NT3 into the conducting polymer polypyrrole (Ppy) synthesized with para-toluene sulfonate (pTS) to investigate whether Ppy/pTS/NT3-coated cochlear implant electrodes could provide both neurotrophic support and electrical stimulation for SGNs. Enhanced and controlled release of NT3 was achieved when Ppy/pTS/NT3-coated electrodes were subjected to electrical stimulation. Here we describe the release dynamics and biological properties of Ppy/pTS with incorporated BDNF. Release studies demonstrated slow passive diffusion of BDNF from Ppy/pTS/BDNF, with electrical stimulation significantly enhancing BDNF release over seven days. A three-day SGN explant assay found neurite outgrowth from explants was 12.3-fold greater when polymers contained BDNF (p<0.001), although electrical stimulation did not increase neurite outgrowth further. The versatility of Ppy to store and release neurotrophins, conduct electrical charge and act as a substrate for nerve-electrode interactions is discussed for specialized applications such as cochlear implants.
Description
Keywords
Brain Derived Neurotrophic Factor, Polypyrrole, Cochlear Implant, Electrical Stimulation, Sensorineural Hearing Loss, Spiral Ganglion Neuron
Citation
Evans AJ, Thompson BC, Wallace GG, Millard R, O’Leary SJ, Clark GM, Shepherd RK & Richardson RT (2008). Promoting neurite outgrowth from spiral ganglion neuron explants using polypyrrole/BDNF-coated electrodes. Journal of Biomedical Materials Research Part A 91 (1):241-50.