Preparation of hydroxyapatite-gelatin nanocomposite

A nanocomposite of gelatin[GEL]-hydroxyapatite[HAp] was prepared using the biomimetic process. The hydroxyapatite nanocrystals were precipitated in aqueous solution of gelatin at pH 8 and 38°C. The chemical bonding between calcium ions of HAp and carboxyl ions of GEL molecules induced a red-shift of the 1339cm^-1 band of GEL in FT-IR analysis. TEM images and electron diffraction patterns for the nanocomposite strongly indicate the self-organization of HAp nanocrystals along the GEL fibrils. Electron diffraction for the nanocomposites showed a strong preferred orientation of the (002) plane in HAp nanocrystals. The development of HAp nanocrystals in an aqueous GEL solution was highly influenced by the concentration ratio of GEL to HAp. A higher concentration of GEL induced the formation of tiny crystallites (4nm×9nm size), while a lower concentration of GEL contributed to the development of bigger crystallites (30nm×70nm size). From DT/TGA data, the HAp-GEL nanocomposite showed typically three exothermic temperatures. The increase in decomposition temperatures indicates the formation of a primary chemical bond between HAp and GEL. The higher concentration of GEL supplies abundant reaction sites containing groups such as carboxyl, which can bind with calcium ions. The abundant supply of reaction sites leads to a very large number of HAp nuclei. However, the formation of a large number of nuclei depletes the concentration of calcium ions that available for growth to the extent that the nuclei cannot grow very large. This in turn will lead to the creation of a large number of tiny nanocrystals at this higher GEL concentration.