title: The effect of polypyrrole with incorporated neurotrophin-3 on the promotion of neurite outgrowth from auditory neurons.
abstract: This research aims to improve the nerve-electrode interface of the cochlear implant using polymer technology to encourage neuron survival, elongation and adhesion to the electrodes. Polypyrrole (Ppy) doped with p-toluene sulphonate (pTS) is an electroactive polymer into which neurotrophin-3 (NT3) can be incorporated. Ppy/pTS+/-NT3 was synthesised over gold electrodes and used as a surface for auditory neuron explant culture. Neurite outgrowth from explants grown on Ppy/pTS was equivalent to tissue culture plastic but improved with the incorporation of NT3 (Ppy/pTS/NT3). Electrical stimulation of Ppy/pTS/NT3 with a biphasic current pulse, as used in cochlear implants, significantly improved neurite outgrowth from explants. Using (125)I-NT3, it was shown that low levels of NT3 passively diffused from Ppy/pTS/NT3 during normal incubation and that electrical stimulation enhanced the release of biologically active NT3 in quantities adequate for neuron survival. Furthermore, Ppy/pTS/NT3 and its constituents were not toxic to auditory neurons and the Ppy/pTS/NT3 coating on gold electrodes did not alter impedance. If applied to the cochlear implant, Ppy/pTS/NT3 will provide a biocompatible, low-impedance substrate for storage and release of NT3 to help protect auditory neurons from degradation after sensorineural hearing loss and encourage neurite outgrowth towards the electrodes.
authors.affiliation: The Bionic Ear Institute, 384 Albert Street, East Melbourne, Vic. 3002, Australia. rrichardson@bionicear.org
authors.forename: Rachael T
authors.initials: RT
authors.lastname: Richardson
authors.forename: Brianna
authors.initials: B
authors.lastname: Thompson
authors.forename: Simon
authors.initials: S
authors.lastname: Moulton
authors.forename: Carrie
authors.initials: C
authors.lastname: Newbold
authors.forename: May Ghee
authors.initials: MG
authors.lastname: Lum
authors.forename: Adrian
authors.initials: A
authors.lastname: Cameron
authors.forename: Gordon
authors.initials: G
authors.lastname: Wallace
authors.forename: Robert
authors.initials: R
authors.lastname: Kapsa
authors.forename: Graeme
authors.initials: G
authors.lastname: Clark
authors.forename: Stephen
authors.initials: S
authors.lastname: O'Leary
mesh_terms: D000818:Animals; D001557:Benzenesulfonates / Q000737:chemistry; D001672:Biocompatible Materials / Q000737:chemistry*; D017097:Electric Impedance; D004566:Electrodes; D005260:Female; D008297:Male; D009416:Nerve Regeneration; D016501:Neurites / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009475:Neurons, Afferent / Q000378:metabolism*; D020933:Neurotrophin 3 / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D001557:Benzenesulfonates; D001672:Biocompatible Materials; D020933:Neurotrophin 3; D011108:Polymers; D011758:Pyrroles; C067635:polypyrrole; C029501:4-toluenesulfonic acid