Research On 3D Printing Of Composite Hydrogel And Repair Of Cartilage Injury

In recent years,articular cartilage injury is a common orthopedic disease.Cartilage is an anisotropic gradient tissue.Due to its lack of blood vessels,lymph and nerves,it cannot provide nutrients for cartilage repair,so once the injury of articular cartilage is difficult to heal itself Although biological scaffolds can repair articular cartilage injury to some extent,because of the anisotropy of cartilage tissue,the scaffolds need to exhibit gradient changes in their composition and physicochemical properties.Therefore,it is particularly important to optimize the different structural parameters of the composite hydrogel single phase scaffolds.In this study,Ansys analysis was used to simulate the mechanical properties of osteochondral scaffold.The structure parameters of the best mechanical properties are determined by adjusting the pore structure of the bracket and the spacing of the wire harness.The composite scaffolds with different HAP concentrations were integrated into the multi-layer scaffolds by low-temperature chemical two step crosslinking method,and the natural gradient structure of bone cartilage was simulated.The mechanical properties test showed that the mechanical properties of the integrated scaffold could reach MPa level,so as to meet the requirements of bone cartilage repair.And toxicity tests and cell adhesion tests of gradient composite hydrogel single phase scaffolds were carried out.The main contents of this study are as follows:(1)According to the characteristics of cartilage scaffold,the scaffold structure was designed.The material of bio ink and the related layer parameters of scaffold printing were selected.The mechanical simulation of the designed scaffold structure was carried out by using ANSYS software,and the analysis shows that the compression deformation of the scaffold is the smallest when the distance between the scaffold wiring harness is 1 mm and the pore shape is 45°/135° rhombus;(2)Gelatin/alginate hydrogels were prepared by gradient heating method.The hydroxyapatite solution was added to gelatin/alginate hydrogel by ultrasonic dispersion of hydroxyapatite solution,and the composite bio ink containing different concentrations of hydroxyapatite was prepared.(3)The characterizations of the composite hydrogel scaffolds with different concentration gradient were detected and analyzed.In order to simulate the natural structure of the cartilage,the hydroxyapatite composite hydrogel single phase scaffold was printed by using biological 3D printing technology.The multi-layer scaffolds were integrated by low-temperature chemical two step cross-linking method,and the mechanical properties of the multi-layer support are tested,and the results show that the mechanical properties meet the requirements of cartilage repair;(4)Chondrocytes and BMSCs were extracted from SD rats to evaluate the viability of the scaffolds.Toxicity tests of composite hydrogel scaffolds with different concentration gradient showed that the composites did not significantly inhibit cells growth or kill cells.Cell viability/death staining of scaffolds inoculated with chondrocytes showed that cell viability of hydroxyapatite composite hydrogel scaffolds was relatively high.