Mechanically Drawn Hydrogels Uniaxially Orient Hydroxyapatite Crystals and Cell Extension

Freeze-thawed poly(vinyl alcohol) hydrogels were structurally oriented by uniaxial mechanical drawing up to 1-5 times their original length, and the orientation was fixed by successive chemical cross-linking using glutaraldehyde (20 mol %). Hydroxyapatite (HAp) crystals were successfully mineralized onto the oriented hydrogels by repeated alternate immersion into the solutions of phosphate ion and calcium ion. X-ray diffraction images confirmed that the c-axis of the HAp crystal cell was oriented perpendicularly to the surface of the hydrogel. In addition, polarized infrared spectroscopy confirmed the orientation of the phosphate ion. We investigated the effects of these structurally oriented HAp-PVA hydrogel hybrids on the anisotropy of cell extension. Scanning electron microscopy confirmed that mouse fibroblasts (L929) extended onto the oriented HAp-hydrogel hybrid along the drawing direction. These results may lead to the development of a tissue engineering scaffold for yielding oriented bony tissues.