Influence of porogens on architecture and osteogenesis of porous carbonate apatite artificial bones

Abstract

Carbonate apatite (CO₃Ap), a mineral component of bone, is an attractive component of artificial bone. In addition to composition, architecture plays an important role in bone regeneration. In this study, three types of porous CO₃Ap scaffolds were fabricated using polyurethane foam and spherical phenol resin as porogens. CO₃Ap-F was fabricated using polyurethane foam as porogen and had large interconnected pores (20–100 μm). CO₃Ap-R was fabricated using spherical phenol resin as porogen and had smaller interconnected pores (2–20 μm). CO₃Ap-FR was fabricated using both porogens and it had a wide range of interconnected pores (2–100 μm). The CO₃Ap-FR scaffolds, which exhibited the most diverse pore size distribution and highest porosity (65 %), demonstrated the weakest mechanical strength among the three scaffolds, but it is comparable to that of the trabecular bone. CO₃Ap-FR significantly enhanced new bone formation and material resorption compared to CO₃Ap-F and CO₃Ap-R, 4 weeks after implantation in femoral bone defects in rabbits. Therefore, CO₃Ap-FR promoted cell and tissue infiltration into the scaffold through large interconnected pores templated from polyurethane foam, and facilitating strut resorption through smaller interconnected pores templated from spherical phenol resin within the struts, respectively, in vivo. Thus, we succeeded in the fabrication of porous CO₃Ap artificial bones with large interconnected pores, high porosity, and sufficient mechanical strength using a combination of two distinct porogens, polyurethane foam and spherical phenol resin. These findings suggest that CO₃Ap-FR artificial bone offers an effective strategy for bone regeneration by presenting a promising solution for addressing severe bone atrophy owing to its wide pore size distribution.