Fabrication and evaluation of carbonate apatite-coated calcium carbonate bone substitutes for bone tissue engineering.

Carbonate apatite-coated calcium carbonate (CO3 Ap/CaCO3 ) was fabricated through a dissolution-precipitation reaction using CaCO3 granules as a precursor to accelerate bone replacement based on superior osteoconductivity of the CO3 Ap shell, along with Ca2+ release from the CaCO3 core and quicker resorption of the CaCO3 core. In the present study, CaCO3 , 10% CO3 Ap/CaCO3 , 30% CO3 Ap/CaCO3 , and CO3 Ap granules were fabricated and examined histologically to evaluate their potential as bone substitutes. Larger contents of CaCO3 in the granules resulted in higher Ca2+ release and promoted cell proliferation of murine preosteoblasts at 6 days compared with CO3 Ap. Interestingly, in a rabbit femur defect model, 10% CO3 Ap/CaCO3 induced significantly higher new bone formation and higher material resorption compared with CO3 Ap at 8 weeks. Nevertheless, CO3 Ap showed a superior osteoconductive potential compared with 10% CO3 Ap/CaCO3 at 8 weeks. All tested granules were most likely resorbed by cell mediation including multinucleated giant cell functions. Therefore, we conclude that CO3 Ap/CaCO3 has a positive potential for bone tissue engineering based on well-controlled calcium release, bone formation, and material resorption.