| Microelectrodes for stimulating and/or recording signals have made possible direct electrical connections with living neural tissue. Silicon electrode arrays are excellent tools for communication with living neurons however they have limited chronic recording abilities. The inability to maintain long-term electrode-neuron communication is attributed to an increase in impedance of implanted electrodes and neuronal loss around the implant that is associated with an inflammatory reaction within CNS. To improve the long-term integration and performance of these implanted devices, efforts have been dedicated to understanding the factors influencing the functionality of the inserted electrodes and to the development of novel coating technologies that can be used to modify the electrode surface.; Our approach takes advantage of recent developments in the synthesis, processing, and characterization of novel polymeric materials and the use of relevant biologic elements and in vitro cell models. In this thesis, we present studies concentrated on modification of both the metal microelectrode sites of neural electrodes using conducting polymers and the shanks of neural electrodes using alginate hydrogels. This entails the use of polymers for: (1) creation of soft, electrically conductive, bioactive coatings (5-500 mum) that can be deposited onto the electrode shaft providing a biocompatible, mechanical buffer at the interface between the neurons and the electrodes, (2) modification of the neural electrode sites by high surface area morphology conducting polymers grown through the hydrogel layers to reduce impedance as low as 7 kO and improve communication with neurons, (3) incorporation of neurotrophic proteins into conducting polymers to encourage growth of neurities from neurons near the electrodes, (4) the development of nanoparticle-release vehicles to deliver anti-inflammatory drugs to attenuate the host inflammatory response at the site of implantation. The effects of these biomaterials on signal transduction and cell/electrode interaction in vitro and in vivo were also studied.; In summary, we present a novel polymer-based coating technology for neural electrodes. Our in vitro and in vivo data suggest these bioactive, electrically conductive coatings can be used to overcome the current limitations of chronically implanted neural electrodes and represent a useful means for local administration of therapeutic agents for neural electrodes. |
