In vivo bone biocompatibility and degradation of porous fumarate-based polymer/alumoxane nanocomposites for bone tissue engineering.

The objective of this study was to determine how the incorporation of surface-modified alumoxane nanoparticles into a biodegradable fumarate-based polymer affects in vivo bone biocompatibility (characterized by direct bone contact and bone ingrowth) and in vivo degradability. Porous scaffolds were fabricated from four materials: poly(propylene fumarate)/propylene fumarate-diacrylate (PPF/PF-DA) polymer alone; a macrocomposite consisting of PPF/PF-DA polymer with boehmite microparticles; a nanocomposite composed of PPF/PF-DA polymer and mechanically reinforcing surface-modified alumoxane nanoparticles; and a low-molecular weight PPF polymer alone (tested as a degradation control). Scaffolds were implanted in the lateral femoral condyle of adult goats for 12 weeks and evaluated by micro-computed tomography and histological analysis. For all material groups, small amounts of bone, some soft tissue, and a few inflammatory elements were observed within the pores of scaffolds, though many pores remained empty or filled with fluid only. Direct contact between scaffolds and surrounding bone tissue was also observed in all scaffold types, though less commonly. Minimal in vivo degradation occurred during the 12 weeks of implantation in all materials except the degradation control. These results demonstrate that the incorporation of alumoxane nanoparticles into porous PPF/PF-DA scaffolds does not significantly alter in vivo bone biocompatibility or degradation.