β-TCP/PCL interpenetrating phase composites with a synergy between mechanical property and bioactivity fabricated by vacuum-assisted microporous infiltration for bone repair

Bioactive ceramics are ideal materials for bone substitutes owing to their excellent osteoconductivity, but the application in load-bearing conditions is limited by their intrinsic brittleness. Inspired by the interpenetrating organic-inorganic structure of natural bone, we developed ceramic/polymer interpenetrating phase composites (C/P-IPCs) by vacuum-assisted microporous infiltration of polycaprolactone (PCL) molten into the interconnected micropores in vat photopolymerization printed β-tricalcium phosphate (β-TCP) samples. The C/P-IPCs achieved a synergy of mechanical properties and bioactivity compared with the pure ceramic β-TCP and the conventional ceramic particle-reinforced polymer (CPR-P) from the same materials. Specifically, the composites exhibited dramatically enhanced mechanical properties over pure ceramic, with strength increases of approximately 2.1- to 2.4-fold and strain energy density improvements of 2.4- to 5.5- fold. Meanwhile, the C/P-IPCs demonstrated a moderate degradation rate and superior mechanical stability during degradation. Furthermore, their biological performance of C/P-IPCs was markedly superior to that of CPR-P, including cell proliferation, differentiation, and bone repair. These results indicate that the C/P-IPCs are a promising candidate for bone repair under load-bearing conditions.