Research On Composite Of Nano-hydroxyapatite/Polyamide 66 For Bone Replacement

Hydroxyapatite (HA) is widely used in field of biomaterials because of its excellent biocompatibility and osteoconductivity, but the brittleness and high modulus of HA limit its load-bearing application. In order to maintain the biological activity of hydroxyapatite and improve its mechanical properties, a series of hydroxyapatite/polymer composites were synthesized to meet the requirements of hard tissue repair.This work developed a new process for preparing HA/polyamide66 (PA66) nanocomposite. The HA nanorods were coated by Gelatin first, and then dissolved them in the solvent mixed glycerol and N, N-dimethylacetamide. A stable sol of n-HA was consequently prepared, then reacted with PA66 to prepare n-HA/PA66 nanocomposite. Our mainly accomplishments are as follows:1,Gelatin played a significant role in coating on the particles surface. Because the Gelatin coated on the surface of n-HA contains amide groups to be the same as PA66, they had good compatibility in the mixture of HA sol and PA66 solution, thus formed a chemical bond at organic–inorganic interface. n-HA particles combined with PA66 matrix closely and no crack or pore in the cross section. What's more, n-HA sol was beneficial to the well distribution of nano-hydroxyapatite in the PA66 matrix. The HA particles in the nanocomposite had a length of 50~100nm, and a diameter of 25~30nm, with a Ca/P ratio of 1.65, which is close to the stoichiometric ratio of HA (1.67).2,With the increasing of HA content, the bending strength of nanocomposite increased, while the tensile strength decreased. And 5 % n-HA/PA66 nanocomposite was suitable for bone substitute material.3,After soaking in a simulated body fluid(SBF), the results showed that spherical apatite with weak crystallinity formed on their surface. With immersion time prolonged, their size and crystallinity increased. Combined the Fourier Transform Infrared Spectroscopy (FTIR) result, it was found that the HA crystals were partially substituted with carbonate, namely bone-like apatite, which played a very important role in the regeneration of bone.4,No cytotoxicity was observed while osteoblasts were cultured on PA66 and n-HA/PA66 nanocomposite.Whereas the morphology and density of cells near n-HA/PA66 nanocomposite were better than those near the PA66, and the cells grew and stretched very well around the nanocomposite. There was a different influence on osteoblasts between the n-HA/PA66 and PA66 samples.