Bone Regeneration Induced by Local Delivery of a Modified PTH-Derived Peptide from Nanohydroxyapatite/Chitosan Coated True Bone Ceramics

A novel PTH-derived peptide, PTHdP, including a repetitive aspartic acid sequence at the C-terminal and phosphorylated serine at the N-terminal has been previously designed. To evaluate its potential as a bone growth factor for bone tissue engineering, true bone ceramics incorporated with nanohydroxyapatite coating and chitosan (CH/TBC) was developed as a desired three-dimensional porous delivery carrier in this study. In vitro results showed that PTHdP could be loaded with high-efficiency and subsequently released in a controlled and sustained manner from CH/TBC. Bioactivity of released PTHdP was retained and able to exert a significant effect on promoting or inhibiting osteogenesis actions when exposed intermittently or continuously, respectively, for MC3T3-E1 cell culture. As evaluated in a critical-size rabbit radial defect model by radiographic and histological examination, the combination of CH/TBC scaffolds with PTHdP exhibited a remarkably stronger capacity to stimulate new bone formation than control and pure CH/TBC groups. These results indicated the novel PTHdP peptide achieved high affinity to bone mineral without interference in bioactivity, and local delivery of PTHdP from apatite materials could be a promising alternative for future bone tissue engineering.