The effect of partial dissolution-precipitation treatment on calcium phosphate ceramics in the release of BMP-2 and osteoinduction

Biomimetic calcium phosphate ceramics with excellent bio-absorption and osteoinduction were designed by the partial dissolution-precipitation (PDP) treatment. Beta-tricalcium phosphate (β-TCP) ceramics with single phase were transformed into monetite, hydroxyapatite (HAp) and β-TCP phases by the PDP treatment. The PDP-β-TCP ceramics had a specific surface area of 22.5 m²/g and porosities of 60-80%. Changes in microstructure of the ceramics before and after PDP treatment influenced body fluid permeation, release characteristics of bone morphogenetic protein-2 (BMP-2) and osteoinduction. ¹²⁵I-labeled BMP-2 was loaded on the four different ceramics, such as spongy-derived bulk of HAp (b-HAp), functionally graded HAp (fg- HAp), β-TCP, and PDP-β-TCP The four kinds of ceramics were implanted into the back region of subcutaneous tissue in rats and the analyses of the release of BMP-2 and BMP-2 dose-response of bone formation were investigated. In the fg-HAp/BMP-2 and PDP-β-TCP/BMP-2 ceramics, the release time corresponding to the half amount (t 1/2) of BMP-2 were prolonged about 14 and 7 times respectively compared to the ceramics before PDP treatment. BMP-2 dose-response of bone formation study showed the areas of bone tissues were significant higher in the fg-HAp/BMP-2 (5.0ug) and PDP-β-TCP/BMP-2 (0.5ug) ceramics compared to the ceramics before PDP treatment. These results indicated the PDP treatment enhanced BMP-2 release and osteoinduction.