Preparation And Study Of 3D Printed PDA/PLGA/?-TCP Composite Tissue Engineering Scaffolds

The need for effective treatment of critical-sized bone defects resulted from osteoporosis,malignant tumor,trauma,and fractures is urgent.Because the clinical use of bone grafting methods may lead to complications such as infection,chronic pain,potential immunogenicity,and other limitations,which includes insufficient donor sources and excessive economic pressure to be treated.For the above reasons,bone tissue engineering as the most promising solution is considered to be the main strategy for bone defect repair.As a polymeric basis for the biocompatible and bioresorbable matrices for the reconstruction of soft and hard tissue,currently the compounds are often selected from the homologous range of aliphatic polyesters,which have poor mechanical properties for load-bearing,as well as poor osteoconductive properties,but they will obtain significantly increased strength and osteogenic potential when combined with bioceramics.The temperature advantage of the low-temperature 3D printing technology can be used to carry the drug during the preparation process of the scaffold simultaneously,so as to achieve the controlled release of the drug in the composite materials.Low-temperature 3D printing technology can not only prepare highly accurate products,but also ensure that the whole process avoids the high temperature effect,which is in favor of better biocompatibility of the bone scaffold.Design and prepare poly(lactic-co-glycolic acid)(PLGA)/p-tricalcium phosphate(?-TCP)bone tissue engineering composite scaffold which is studied by further surface-modified.Systematically evaluate the bone repair ability of the prepared scaffold in vitro and in vivo,providing new methods and ideas for clinical regenerative medicine by bone tissue engineering strategy.1.The ?-TCP/PLGA composite bone tissue engineering scaffold was prepared by extrusion-printing methods,and then the ratio of ?-TCP and PLGA was changed to explore the relation between inorganic contents and bone formation to find the most suitable percentage for osteogenesis.The result verified that as the proportion of calcium phosphate increased,the mechanical properties of the composite scaffold were enhanced with not affecting the porosity,and the hydrophilic properties of the scaffold surface are partially improved.Scanning electron microscopy(SEM)observation showed the multi-level micropore structure on the surface of the scaffold.It was proved by in vitro biological experiments that the nanoscale surface can promote cell adhesion and cell proliferation,regulating the osteogenic differentiation of cells,and the osteogenic activity of the scaffold were advanced with the increase in the proportion of calcium phosphate.The implantation of cranial defect model in mice explained that the composite scaffold of high content of inorganic components had a excellent effect on repairing bone defects.2.The obtained ?-TCP/PLGA composite scaffold with the best osteogenic activity was further studied on surface modification of polydopamine(PDA)to promote scaffold affinity to cells.PDA coating on polymer scaffolds had been extensively demonstrated to enhance stem cells specific responses by up-regulating Ang-1 and vWF proteins,thereby stimulating cell adhesive and proliferative ability,and shortening cell cycle.In vitro experiments showed that the PDA-coated?-TCP/PLGA composite scaffold played a significant role in promoting cell adhesion and proliferation.3.Having compared the ability of cell proliferation,cell differentiation and bone reparation between ?-TCP/PLGA scaffold and PDA coating scaffold and ?-TCP/PVA/dipyridamole drug-loaded scaffold,the results demonstrated the positive influence of inorganic content,surface modification of PDA and controlled drug release from drug-loaded scaffold on osteogenesis,suggesting that the high calcium phosphate content is conducive to the supply of raw materials in the formation of new bone tissue,and the micro-structure changes of the scaffold surface after PDA modification,which provided a new method for bone tissue engineering scaffolds and clinical regenerative medicine.