Honeycomb Scaffolds Fabricated Using Extrusion Molding and the Sphere-Packing Theory for Bone Regeneration

Osteoconductive scaffolds can be used to treat large bone defects that arise due to accidents, tumors, congenital defects, and age-related ailments. Carbonate apatite is a promising material for the fabrication of scaffolds because its composition is analogous to that of natural bone. Here, three types of carbonate apatite honeycomb scaffolds with uniaxially penetrating precisely size-controlled channels were fabricated using extrusion molding as a base technique. The channel sizes of the scaffolds were varied, with the other parameters kept approximately identical, to correlate channel size with angiogenesis and osteogenesis. The scaffold struts were constructed by interconnecting the carbonate apatite spheres based on the theory of sphere packing; thus, micropores of predictable sizes were formed in the struts. In vivo animal experiments indicated that the size of the formed blood vessels in the scaffolds increased ∼fivefold as the channel size increased from 170 to 285 μm. Moreover, the large channels promoted the formation and maturation of bone tissue. We concluded that the channel size significantly affected angiogenesis within the scaffolds, thereby impacting bone regeneration. The results of this study may contribute to the fabrication of scaffolds for tissue regeneration techniques that involve angiogenesis as an underlying mechanism.