Analysis of In-vitro Neurite Extension for Neurotrophic Electrode Design

Stimulation of nervous tissue using implantable electrode systems has been suggested for a wide range of clinical problems including depression, migraine headaches, systemic pain, deafness, blindness, bladder function etc. Several of these problems would require the long-term implantation of multi-channel electrode systems in close proximity to the appropriate neural tissue within the central nervous system. In this work, we continue our attempt to apply and quantify neurotrophic tissue engineering techniques in an in-vitro test system that can guide the future functional improvement of implanted electrodes for clinical use. Our model system consists of cultured PC-12 cells and polyimide microtubes. The microtubes act as conduits to capture neurite extension. This is a model for the demonstrated neurite extension that occurs in known neurotrophic electrode systems such as the cone electrode developed by Kennedy et al. The tubes also can act as vessels for the transport of neurotrophic agents that could attract candidate neurons close to the electrode site. In this study, we quantify neurite extension induced via nerve growth factor (NGF). We show that NGFadsorbed gelatin sponges can be used to create an effective NGF gradient to induce directional neurite growth in this system