| BACKGROUNDRepairing craniomaxillofacial bone defects is an urgent need to improve the quality of life of patients.High density polyethylene(HDPE)has good biocompatibility and non-degradability,which has been widely used for long-term implantation of cranialomaxillofacial bone defects.However,its molding mode and surface activity still need further improvement.OBJECTIVEHDPE scaffolds were 3D printed,using surface modification method of polydopamine combined with hydroxyapatite and vascular endothelial growth factor to optimize the HDPE matrix materials and explore the bioactivity and bone organization integration capability of the post-optimized scaffolds.METHODS1.HDPE scaffolds are prepared by extrusion 3D printing technology.Nanoparticles loaded with VEGF were prepared by solvent removal method.The HDPE scaffolds were immersed in dopamine solution,simulated body fluid and VEGF nanoparticle suspension in turn,and PDA,HA and VEGF were modified on the surface of the scaffolds,which were HDPE/PDA scaffolds,HDPE/PDA/HA scaffolds and HDPE/PDA/HA/VEGF scaffolds respectively.The prepared VEGF nanoparticles and scaffolds were characterized and detected.2.MC3T3-E1 cells and HUVEC cells were used to evaluate the osteogenic activity of the surface modified scaffold in vitro.The effects of surface modification on the adhesion and proliferation of MC3T3-E1 cells and HUVEC cells were evaluated by Live/Dead staining and Alamar Blue staining.The effect of surface modification on early osteogenic differentiation ability of MC3T3-E1 cells was evaluated by Alkaline phosphatase(ALP)and alizarine red staining.3.A New Zealand rabbit skull defect model was used to further evaluate the in vivo osteogenic effect of the surface-modified scaffolds.A New Zealand rabbit skull defect model was established and scaffolds-free group,HDPE scaffolds group,HDPE/PDA/HA scaffolds group and HDPE/PDA/HA/VEGF scaffolds group were randomly implanted.Skull specimens at 8 weeks and 12 weeks were collected,and the osteogenic ability of the surface modified scaffolds was evaluated by micro-CT,and the osteointegration ability of the surface modified scaffolds was evaluated by histological staining.RESULTS1.The HDPE scaffolds with the same structure as the model is prepared by extrusion 3D printing technology.After modification,the surface color of the scaffolds changed,the micro-structure did not change significantly,and the roughness of the microstructure increased significantly.After modification,the surface water contact Angle of the support decreases obviously,and the compression modulus of the support does not change significantly before and after modification.2.In vitro cell test results showed that no obvious dead cells were found on the surface of the 4 groups of scaffolds,and the adhesion amount of MC3T3-E1 cells and HUVEC cells increased on the surface of the scaffolds after modification.At 1 d,3 d and 5 d,the number of MC3T3-E1 cells and HUVEC cells on the surface of the modified scaffolds increased significantly.After modification,alkaline phosphatase activity of MC3T3-E1 cells on the surface of scaffolds increased significantly,Alizarin red staining deepens color and increases area.3.Micro-CT data reconstruction and quantitative analysis showed that compared with HDPE scaffolds,more new bone was formed at the defect implantation site after modification,and bone volume fraction and bone density were significantly increased,but the defect was still not completely repaired at 12 weeks.Histological staining results showed that compared with the HDPE scaffolds,more new bone tissue was formed at the implantation site of the modified scaffolds defect,and the distance between the modified scaffolds and the host bone tissue was significantly shortened.CONCLUSIONThe porous HDPE scaffolds with the same structure as designed was prepared by extrusion 3D printing technology,and the HDPE matrix material was successfully optimized by using PDA combined with HA and VEGF surface modification methods.After optimization,the scaffolds promoted the adhesion and proliferation of MC3T3-E1 cells and HUVEC cells in vitro,and the osteogenic differentiation of MC3T3-E1 cells.It promotes the formation of new bone in vivo and the ability of scaffolds to integrate with host bone tissue. |
