Modulation of nano-hydroxyapatite size via formation on chitosan–gelatin network film in situ

Natural bone is actually an inorganic/organic composite mainly make up of nano-hydroxyapatite (Ca10(PO4)6(OH)2, nHA) and collagen fibers. It is most important to form nHA/polymer composites in order to provide good biocompatibility and integration with bone tissue. In this work, nHA was formed in-situ on the surface of chitosan–gelatin (CG) network films in tris-buffer solution containing Ca(NO3)2-Na3PO4. The interaction between CG network film and nHA crystalline were studided using the diffuse reflectance FT-IR (ATR-FTIR), thermal analysis (TGA) and X-ray diffraction analysis (XRD), and the influence the nHA size factors, e.g. the ratio of chitosan (CS) and gelatin (Gel), concentration of calcium ions and reaction temperature, were elucidated by XRD and transmission electron microscope (TEM). Results suggested that carboxyl groups, CO and amino groups play crucial roles for HA formatting on the surface of CG network films and the average size of nHA crystalline decreasing with enhancing Gel content and increase with the increasing calcium and phosphate concentration, and when the reaction temperature below 50 °C the nHA crystalline size is almost fixedness (range from 17.2 to 19.2 nm) but when the temperature arrived at 70 °C it increase to 52.3 nm.