Sandwich UHMWPE-Collagen-HAp Cartilage-Bone Patch: Fabrication and Characterization

A layered hybrid implant was designed and fabricated for the surgical replacement of worn cartilage to meet the complex requirements of biocompatibility and mechanics. The natural hierarchical structure was purposefully mimicked to improve the implant performance and integration. The hybrid was fabricated using three components: processed collagen gel, hydroxyapatite (HAp) powder and ultra-high molecular weight polyethylene (UHMWPE) in bulk and sponge form. The fabrication included hot molding, sacrificial templating, infusion, and freeze-casting stages. The hybrid had a porous transition layer made of porous UHMWPE impregnated with collagen by means of infusion. SEM and FTIR analyses confirmed successful collagen impregnation of porous UHMWPE. The morphology of transition layer was selected and produced to provide the UHMWPE pore size distribution in a range similar to 50-150 mu m that is favorable for the osseointegration by osteoblast proliferation. Biocompatibility tests were carried out in vitro. The index of red blood cells hemolysis showed 0.6 % after 4 h of co-incubation that proved excellent biocompatibility of the fabricated UHMWPE-Collagen-HAp hybrid.