Osteoinduction by Functionally Graded Apatites of Bovine Origin Loaded with Bone Morphogenetic Protein‐2

Bioresorbable and functionally graded apatites (fg‐HAp) ceramics, which are characterized by gradations in crystallinity and the grain size of hydroxyapatite (HAp:Ca 10 (PO 4 ) 6 (OH) 2 ), were designed using bovine bone by the calcination and partial dissolution–precipitation method. The fg‐HAp ceramics had macropores of 100–600 μm originated from spongy bone, and micropores of 10–160 nm. Fg‐HAp ceramics loaded with recombinant human bone morphogenetic protein‐2 (rhBMP‐2/fg‐HAp) were implanted into the subcutaneous tissue of rats. Eight weeks after the implantation, the surface and bulk degradations of the fg‐HAp‐containing body fluid occured, and small pieces of fg‐HAp were incorporated into the induced bone and fatty marrow, suggesting that osteoinduction occurred in conjunction with bone remodeling. The rhBMP‐2/fg‐HAp ceramics developed could become a resorbable biomimetic material with fast bioresorption and osteoinduction characteristics.