Mechanical and biological evaluation of a hydroxyapatite-reinforced scaffold for bone regeneration.

With over 500,000 bone grafting procedures performed annually in the United States, the advancement of bone regeneration technology is at the forefront of medical research. Many tissue-engineered approaches have been explored to develop a viable synthetic bone graft substitute, but a major challenge is achieving a load-bearing graft that appropriately mimics the mechanical properties of native bone. In this study, sintered hydroxyapatite (HAp) was used to structurally reinforce a scaffold and yield mechanical properties comparable to native bone. HAp was packed into a cylindrical framework and processed under varying conditions to maximize its mechanical properties. The resulting HAp columns were further tested in a 6-week degradation study to determine their physical and mechanical response. The cellular response of sintered HAp was determined using a murine preosteoblast cell line, MC3T3-E1. Cell viability and morphology were studied over a one-week period and MC3T3-E1 differentiation was determined by measuring the alkaline phosphatase levels. Finite element analysis was used to determine the columns' geometric configuration and arrangement within our previously developed composite bone scaffold. It was determined that incorporating four cylindrical HAp columns, fabricated under 44 MPa of pressure and sintered at 1200°C for 5 hr, led to load-bearing properties that match the yield strength of native whole bone. These preliminary results indicate that the incorporation of a mechanically enhanced HAp structural support system is a promising step toward developing one of the first load-bearing bone scaffolds that can also support cell proliferation and osteogenic differentiation.