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P Huie, MC Peterman, T Leng, CJ Lee, MF Marmor, DM Bloom, MS Blumenkranz, HA Fishman; Tissue-engineered Neurite Conduits to Connect Retinal Ganglion Cells to an Electronic Retinal Prosthesis . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4475.
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Purpose: Current retinal prostheses use an array of electrodes to stimulate retinal nerve cells at an indeterminate distance. More precise stimulation would be achieved if individual nerve processes could be guided directly to a retinal prosthesis. The goal of this work was to build a three dimensional array of micro-conduits to link nerve cells to an electronic retinal stimulation source. Methods: Using a novel photolithographic technique at the Stanford Nanofabrication Facility, a high aspect ratio mold was made with SU-8, a polymeric photoresist. This mold was used to fabricate a biocompatible membrane consisting of an array of shallow cups with narrow channels (conduits) that extend through the material. Cultured rat retinal ganglion cells (RGC) and PC-12 cells were grown on the array. The microfabricated structures were analyzed using a combination of light, fluorescence and electron microscopy. Results: We successfully microfabricated membranes with a dense array (300/mm2) of 10 um diameter channels going through the thickness of the membrane. Each channel widened at the end to 15 um diameter cups to hold nerve soma. Cultured RGCs grew effectively on this substrate and self assembled into the cups, from which neurites can move down into the channels. Conclusion: We have demonstrated that neuronal cells can be induced to precisely distribute over a membrane surface and that nerve cell processes can be directed to grow in a pre-defined pattern. In this manner, excitable cells could be organized on an electronic retinal prosthesis to minimize stimulation current thresholds and optimize spatio-temporal selectivity.
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