The development of coatings for enhancing the recording and stimulation capabilities of electrodes used in neural prostheses and electrical stimulation based therapies is proposed. The coatings are based on conducting polymers that we have recently found support charge- injection levels at least six times greater than is possible with the highest charge-injection capacity materials presently available. Specific innovations in terms of polymer adhesion to metal electrodes and the development of polymers functionalized with biologically active species for enhancing and stabilizing the electrode-nerve interface are proposed. The principal Phase I objectives are 1) to develop methods for the robust attachment of the polymer coatings to the surface of metal microelectrodes and 2) to evaluate, in a short chronic study, the passive and functional biocompatibility of polymer-coated electrodes. In vitro studies of the adhesion, charge-injection capabilities and impedance of polymers deposited on metal electrodes using several adhesion promoting strategies will be undertaken. Adherent polymer coatings will be used with penetrating microelectrodes for histologic and functional biocompatibility assessments in a 70 day in vivo study. The recording capabilities of the electrodes will be monitored weekly. Polymer-coated electrodes will be subjected to a charge-injection challenge at four times the maximum possible with present materials. In vivo electrical characteristics during current pulsing and quantitative histologic evaluation of non-pyknotic neuron densities and the extent of gliotic encapsulation will be used as measures of stability and biocompatibility. Commercial: EIC Laboratories will commercialize the technology by offering electrode coating services, the development of turn-key electrodeposition systems, and through licensing. Relevance: Applications of the conducting polymer coatings include cortical control prostheses (brain-machine interfaces) for the spinal cord injured, retinal prostheses for patients with retinitis pigmentosa or age-related macular degeneration, intracortical visual and auditory prostheses for blind and deaf patients, peripheral nerve prostheses for the spinal cord injured, and electrodes for stimulation-based therapies such as deep-brain-stimulation (DBS) and cardiac pacing. Neural prostheses are being developed for rehabilitation in spinal cord injury, stroke, and disease-related sensory deficits. Electrical-stimulation based therapies are being developed for the treatment of neuro- degenerative diseases such as essential tremor and Parkinson's, and the treatment of epilepsy, depression and eating disorders. Many of these applications involve a direct interface to the nervous system and require small-area electrodes with recording and stimulation capabilities beyond those available with noble metals. This proposal addresses the development of electro-polymerized films of conductive polymers as electrode coatings for the recording and stimulation needs of electrodes used in these prostheses and therapies. The potential advantages of the conductive polymers over competing electrode coatings are an exceptionally high charge-injection capacity and the possibility of developing coatings that contain biologically active molecules to promote the formation of a stable and functionally enhanced nerve-electrode interface. ? ? ?
