Neural prosthetics are intended to replace or substantially augment motor and sensory functions of neural pathways that have been lost or damaged due to physical trauma, disease, or genetics. However, performance of successful neural prosthetics, such as the cochlear implant (CI), has not significantly improved in recent years due to poor spatial resolution at the nerve-implant interface. Directing nerve cell processes towards target electrodes may reduce the problematic current spread and improve stimulatory specificity. Consequently, our work utilizes the spatial and temporal control inherent to photopolymerization methodology to fabricate micropatterned methacrylate polymers that direct nerve cell growth based on substrate topographic and stiffness cues. Micropatterned substrates are formed in a rapid, single-step reaction by selectively blocking light with glass-chrome photomasks which have repeating line-space features with a pitch of 10-100 �m in width. The resultant pattern is a continuous series of ridges and grooves at regular intervals that can be used for cellular contact guidance studies. Micro-feature depth is controlled and reproducibly generated from 220�40nm to 16�1.3�m by shuttering the light source at different time steps during the reaction and by modulating photo-initiator concentration. Regenerative growth of inner ear nerve cells orients to the direction of the micro-pattern and is strongly dependent on feature size and slope. Substrate stiffness is modified by varying the cross-link density of the final material by either increasing the amount of cross-linker in the prepolymer formulation or by increasing the size of the spacer unit between cross-links. Spiral ganglion neurites were observed to align more strongly as substrate rigidity increased. The ultimate goal of the research is to develop materials that predictably orient regenerative nerve cell growth and improve neural prosthetic stimulatory specificity and, thus, improve patient outcomes.

Neural pathfinding on photopolymerized micropatterns with varied elasticity

246th National Meeting (2013)

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