Construction And Characterization Of Porous Hydroxyapatite Scaffold With Surface Micro-Nanostructure

Scaffolds, cells and growth factors are three elements of Tissue Engineering. Scaffolds play the role of matrix in bone tissue engineering, provide a suitable place for the normal physiological activity of cells, the growth of tissue and the metabolism of nutrients. As a main inorganic component of bone, hydroxyapatite has good biocompatibility and osteoinductivity, which is often used for the repair of hard tissue. The physical and chemical properties of scaffolds have a major impact on the adhesion, proliferation and differentiation of cells, including the material composition, surface microstructure, porosity etc. Studies suggest that the special surface microstructures can increase the absorption of protein and promote cell growth. Thus, the regulation of microstructure on the hydroxyapatite scaffold surface is very important.This paper was based on the porous hydroxyapatite scaffolds. The dip-coating and hydrothermal methods were used to build special macrostructures on scaffolds surface. During the process, an organic molecular H6L and metal ion Cu+were used to regulatory the growth of microstructures. We studied the formation mechanism and effect on cells growth of the surface microstructures. The main contents and results are as follows:Firstly, a calcium phosphate layer was made on the porous HA scaffold surface by dip-coating method. Treat samples with hydrothermal at 150℃,3h. After that, we got a rod-like structure which was about 3-5μm diameter and 20μm length on the surface of scaffolds. Compared with the blank scaffold, the dip-coating scaffold with a calcium phosphate layer can promote the formation of microstructures.The scaffolds surface microstructures will be changed while different concentrations of H6L were added in hydrothermal solutions as a surfactant. By the increase of concentrations from OmM to 10mM, the surface microstructures changed from rod-like to spheres. The results showed that H6L can regulate the surface microstructures of HA scaffold.It was reported that some metal ions could influence the growth of HA crystals. Cu2+has some features such as promoting vascularization, anti-bacterial, etc. In this paper, we studied the effect of Cu2+ on HA scaffolds’surface microstructures. We doped different concentrations of Cu(NO3)2 in hydrothermal solutions. When the concentration was 4%, we got a spherical-rod structure; when the concentration was 10%, the structure was flower-like.During the mechanical property test, we chose the scaffolds with a depth-diameter aspect ratio of 3:2. The results showed that surface microstructures had less obviously effects on the scaffolds porosity and compressive strength.We studied the adsorption properties to BSA and Ca2+ release properties of different scaffolds. The results showed that HA scaffolds with special surface microstructures would increase the adsorption of BSA and the release of Ca2+, which may be resulted in its larger surface area.The extraction assay for cytotoxicity test showed that the scaffolds with different microstructures displayed non-cytotoxicity to BMSCs. Scaffolds were co-culture with BMSCs for cell experiments. The proliferation of BMSCs on scaffolds with surface microstructures don’t have any obviously differences. While the ALP test showed that some differences, in those samples the flower-rod-like structures showed the highest expression of ALP, indicating that the surface microstructures of scaffolds can effect the performance of BMSCs differentiation.