Multilayered Polyurethane-Hydroxyapatite Composite for Meniscus Replacements

Inspired by the anisotropic structure of natural menisci, porous and densified layers of glycerol phosphate (gp)-conjugated polyurethane (PU) and hydroxyapatite (HA), abbreviated PUH, are alternately stacked to fabricate a biomimetic multilayered scaffold. Densification is used to better match the mechanical properties of the composites to those of natural menisci for load-bearing applications. The porosity is easily controlled (30%, 10%, and 7%) during the densification process by adjusting the applied heat and pressure. The strength and elastic modulus of the densified PUH are significantly higher than those of the porous PUH because HA is trapped as fillers inside the densified PU matrix. Multi-layered PUH is successfully fabricated after stacking the densified and porous layers alternately. And each layer is highly attached, resulting in good interfacial stability. In addition, the scaffold is stiff along the x- and y-directions and more flexible along the z-axis (the stacking direction), as designed.