Prepare Joint Osteochondral Composite Tissue Engineering Bionic Scaffold With Boundary Layer Structure

Although articular cartilage tissue engineering scaffold materials were extensively studied, the boundary layer structure of the joint was often ignored. The clinical treatment shows that the actual joint osteochondral tissue structure has three layer structures, that is transparent cartilage, boundary layer structure and subchondral bone. Therefore, a new idea of bionic integration scaffold was put forward in this thesis, and the joint osteochondral tissue engineering scaffolds with “boundary layer structure” were prepared according to the idea and their performance were studied, so as to provide suitable scaffolds for cell culture in the further study of articular cartilage tissue engineering.In this thesis, two different hydrothermal synthesis methods of nano-hydroxyapatite(HAP)were adopted, and polyethylene glycol(PEG) and stearic acid(SA) were respectively used to modify HAP, and the dispersion of HAP modified before and after in polylactic acid(PLLA) were analyzed. The CPP/PLLA composite tissue engineering porous scaffolds not containing “boundary layer structure” were prepared by solvent casting/particulate leaching, and their physical,mechanical and degradation properties were studied, in which the PLLA was chosen as matrix and the self-made poly-calcium phosphate(CPP) fiber was chosen as reinforcing material. The bionic integration scaffolds with “boundary layer structure” were prepared by compression molding/solvent casting/particulate leaching technique and their physical, mechanical and degradation properties were studied. The experimental conclusions were shown as following.(1) The six prismatic HAP can be easily and effectively prepared when the ratio of Ca/P is 1.67,and the aging temperature is 150℃, and the time is 5h in the system of CaCO3 and CaHPO4·2H2O.Under the same conditions, with the increase of aging time, aging temperature, diffraction peak becomes more obvious, and the crystal shape of HAP becomes more integrity. The dispersion of SA-HAP is better than PEG-HAP and that of SA-HAP in PLLA is also better.(2) The porosity and density of scaffolds exist differences between actual measured values and designed values. The compression modulus and density of scaffolds decrease with the increasing of porosity. The degradation rate changes quickly within 0-6 weeks, and changes slow after 6 weeks,and the degradation liquid presents obviously acid in the late.(3) The upper layer and the lower layer in the bionic scaffold still have three dimensional,connecting, microporous structure, which can guarantees the proliferation and growth of cells and tissues, and the middle dense layer can bear the load.(4) The density of integration porous scaffolds is 0.09 g/cm3, and the porosity is 40%, and the compression modulus is 434.249 MPa, which meets the requirements of joint osteochondral tissue engineering scaffold for physical and mechanical properties.(5) The degradation rate changes quickly within 0-6 weeks, and changes slow after 6 weeks,and the degradation liquid presents obviously acid in the late, which can be overcome according to add suitable amount of HAP.