Studies Of Biomimetic Nano-Hydroxyapatite/Chitosan-Gelatin Network Composites

The development of biomaterials as bone substitutes is of clinical significance for the repair of large bony defects. According to the Food and Drug Administration (FDA), at present there are not approved orthopaedic devices that incorporate tissue-derived components such as cell and /or growth factors.Form the point of view of biomimetic, in this work, nHA crystalline 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, COO- 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℃the nHA crystalline size is almost fixedness (range from 17.2 to 19.2 nm) but when the temperature arrived at 70℃it increase to 52.3 nm.Stomach carcinoma cells and marrow mesenchymal stem cells (MSCs) were seeded on the surface of nHCG and mHCG network films in order to study the different cells behaver on the two composites. Results indicated that the nHCG can inhibit the stomach carcinoma cell attachment and proliferation, and the inhibit effect become more obvious with the increasing of nano-hydroxyapatite crystalline content; In other hand, MSCs maintained higher attachment ability on the surface of nHCG network films than that on the mHCG network films and cell viability, and abilities of MSCs attachment and proliferation enhancing with the increasing nHA crystalline content, nHCG can improve osteogenic differentiation comparison to the on the surface of mHCG network films.The CG macroporous scaffolds were fabricated through freeze-dry technique, nHA crystalline formed on the surface of CG surface of CG scaffold in situ, the microstructures of scaffolds were characterized by FT-IR and SEM. The results indicated that the freeze-drying temperature had great impact on the formation of nHA on the scaffold walls, the nHCG scaffold have very high porosity and the compressive strength also greatly had been improved with enhancing nHA content; in simulated body (SBF), the nHCG network scaffold swell a little and have a small influence on the pH of a aqueous environment. Minitype pig osteoblast cells were seeded into nHCG scaffolds and results revealed that he composite scaffolds had good compatibility and it is potential biomaterials for bone tissue engineering.