Preparation and Characterization of Phosphorylated Collagen and Hydroxyapatite Composite as a Potential Bone Substitute

On the basis of the hypothesis that phosphate groups introduced on collagen can induce the mineralization in natural hard tissue, first, type I collagen (extracted from bovine tendon) was phosphorylated with sodium trimetaphosphate (STMP). The subsequent growth of hydroxyapatite (HAP) on the phosphorylated collagen nanofibers was achieved through a precipitation reaction. The FTIR results indicated that the phosphate groups were incorporated onto the collagen surface through treatment with STMP. During the mineralization process, the rod-like crystals converged into layers of a flaky structure formed on the surface of the phosphorylated collagen, while plate-like minerals were obtained on the pure collagen, as indicated by the SEM and XRD findings. The bending strength of composites isopressed at 180 MPa also displayed a significant increase. The test results demonstrated that phosphate groups had indeed been introduced into the collagen molecules and gave rise to the superior mechanical behavior of the composite materials.