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Stem cells still remain one of the most exciting and lucrative options for treatment of variety of nervous system disorders and diseases. Although there are neural stem cells present in adults, the ability of both the peripheral and central nervous system for self-repair is limited at best. As such, there is a great need for a tissue engineering approach to solve nervous system disorders and diseases. In this study, we have developed electrically conductive surfaces with controlled arrays of high aspect ratio nanowires for the growth and maintenance of neural stem cells. The nanowire surfaces were fabricated from polycaprolactone using a novelnanotemplating technique, and were coated with an electrically conductive polymer, polypyrrole. The polypyrrole coated nanowire surfaces were characterized using scanning electron microscopy and X-ray photoelectron spectroscopy. Additionally, the surface resistance of polypyrrole coated nanowire surfaces was measured. C17.2 neural stem cells were used to evaluate the efficacy of the polypyrrole coated nanowire surfaces to promote cell adhesion, proliferation, and differentiation. The results presented here indicate significantly higher cellular adhesion and proliferation on polypyrrole coated nanowire surfaces as compared to control surfaces. The differentiation potential of polypyrrole nanowire surfaces was also evaluated by immunostaining key neuronal markers that are expressed when NSCs differentiate into their respective neural lineages.

Peripheral nerve damage is common in the United States, with an estimated 200,000 patients treated surgically each year. Autografts, the current gold standard treatment, require that the patient trade functionality by transplanting a nerve from elsewhere in the body. For this reason, tissue-engineering scaffolds that can regenerate nervous tissue and that can direct proliferation need to be investigated. In this work we investigated the influence of micro-patterned nanowire surfaces on neuronal progenitor cell adhesion and proliferation. We created a simple micro-patterning process to create a micro-patterned scaffold with regions lacking a nano-topography approximately 60 microns in width bordered by regions with a nanowire topography approximately 400 microns in width. We hypothesized that neural progenitor cells would preferentially adhere to the regions containing the nano-topography and in turn would avoid regions lacking the nano-topography. Our results indicate that we can direct neural progenitor cell proliferation using this technique. Furthermore, the results show that after 2 days of culture, cells contacting the boundary have elongated morphology. After 5 days of culture, quantifying dimensions on the cell aggregates reveals that they grow twice as long as they do wide on micro-patterned nanowires when compared to controls. These studies suggest that neural progenitor cell growth can be directed by simply creating a scaffold with distinct linear regions of nano-topography bordered by a smooth, hard, hydrophobic surface.

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