Browsing by Author "Clark, Graeme"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Biocompatibility of Immobilized Aligned Carbon Nanotubes
    (Wiley, 2011) Nayagam, David; Williams, Richard; Chen, Jun; Magee, Kylie; Irwin, Jennifer; Tan, Justin; Innis, Peter; Leung, Ronald; Finch, Sue; Williams, Chris; Clark, Graeme; Wallace, Gordon
    In vivo host responses to an electrode-like array of aligned carbon nanotubes (ACNTs) embedded within a biopolymer sheet are reported. This biocompatibility study assesses the suitability of immobilized carbon nanotubes for bionic devices. Inflammatory responses and foreign-body histiocytic reactions are not substantially elevated when compared to negative controls following 12 weeks implantation. A fibrous capsule isolates the implanted ACNTs from the surrounding muscle tissue. Filamentous nanotube fragments are engulfed by macrophages, and globular debris is incorporated into the fibrous capsule with no further reaction. Scattered leukocytes are observed, adherent to the ACNT surface. These data indicate that there is a minimal local foreign-body response to immobilized ACNTs, that detached fragments are phagocytosed into an inert material, and that ACNTs do not attract high levels of surface fouling. Collectively, these results suggest that immobilized nanotube structures should be considered for further investigation as bionic components.
  • Thumbnail Image
    Item
    Promoting neurite outgrowth from spiral ganglion neuron explants using polypyrrole/BDNF-coated electrodes
    (Wiley Periodicals, 2009-10) Evans, Alison; Thompson, Brianna; Wallace, Gordon; Millard, Rodney; O'Leary, Stephen; Clark, Graeme; Shepherd, Robert; Richardson, Rachael
    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.