Photocured Biodegradable Polymer Substrates of Varying Stiffness and Microgroove Dimensions for Promoting Nerve Cell Guidance and Differentiation

Photocross-linkable and biodegradable polymers have great promise in fabricating nerve conduits for guiding axonal growth in peripheral nerve regeneration. Here, we photocross-linked two poly(epsilon-caprolactone) triacrylates (PCLTAs) with number-average molecular weights of similar to 7000 and similar to 10000 g mol(-1) into substrates with parallel microgrooves. Cross-linked PCLTA7k was amorphous and soft, while cross-linked PCLTA10k was semicrystalline with a stiffer surface. We employed different dimensions of interests for the parallel microgrooves, that is, groove widths of 5, 15, 45, and 90 mu m and groove depths of 0.4, 1, 5, and 12 mu m. The behaviors of rat Schwann cell precursor line (SpL201) cells with the glial nature and pheochromocytoma (PC12) cells with the neuronal nature were studied on these microgrooved substrates, showing distinct preference to the substrates with different mechanical properties. We found different threshold sensitivities of the two nerve cell types to topographical features when their cytoskeleton and nuclei were altered by varying the groove depth and width. Almost all of the cells were aligned in the narrowest and deepest microgrooves or around the edge of microgrooves. Oriented SpL201 cell movement had a higher motility as compared to unaligned ones. After forskolin treatment, SpL201 cells demonstrated significantly upregulated S-100 and O4 on stiffer substrates or narrower microgrooves, suggesting more differentiation toward early Schwann cells (SCs). PC12 neurites were oriented with enhanced extension in narrower microgrooves. The present results not only improve our fundamental understanding on nerve cellsubstrate interactions, but also offer useful conduit materials and appropriate feature dimensions to foster guidance for axonal growth in peripheral nerve regeneration.