Collagen-coated Poly(lactide-co-glycolide)/hydroxyapatite Scaffold Incorporated With DGEA Peptide For Synergistic Repair Of Skull Defect

Purpose:Although the natural bone tissue has some regenerative capacity and,to a certain extent,it can be reconstructed,it is necessary to further improve the regenerative capacity in most cases.Accordingly,it is an extensive research point to repair large-area bone defects,especially in dental prosthesis,implant and other related subjects.Opportunely,tissue engineering offers a new strategy to treat the bone defects.In this thesis,a PLGA/HA/Col porous composite bone tissue engineering scaffold was prepared by coating collagen with a commerical poly(lactide/hydroxyapatite)(PLGA/HA)porous tissue engineering scaffold,DGEA is loaded on the collagen coating to improve the ability of tissue engineering scaffolds to repair bone defects.Methods:1?Fabrication and characterization of porous and bioactive scaffold:Combining surface coating and freeze-drying method,collagen(Col)was covered onto the PLGA/HA scaffolds by using glutaraldehyde as a crosslinker to form a natural polymer/synthesized polymer/ absorbable inorganic ceramic ternary composite scaffold in order to mimic the component and structure of the nature bone.Furthermore,the bioactive peptide,i.e.Asp-Gly-Glu-Ala(DGEA)was also incorporated into Col coating layer to improve the bioactivity of the modified scaffold for better bone tissue regenerative behavior.Scanning electron microscope(SEM),electronic universal testing machine and water contact angle were employed to detect the physicochemical properties of three kinds of porous scaffolds including PLGA/HA,PLGA/HA/Col,and PLGA/HA/Col/ DGEA.2? In vivo evaluation of three kinds of scaffolds,namely,PLGA/HA,PLGA/HA/Coland PLGA/HA/Col/DGEA:This study provides a simple and effective method for the surface modification of the porous scaffold for bone repair.This method presents advantages on its simplicity and low cost,and also the thickness and drug loading of the coating layer can be controlled by the concentration of Col coating solution and DGEA.This composite porous scaffold has a better effect on bone repair and potential clinical application than the virgin commercial PLGA/HA.The rat skull defect models were established to investigate the effect of three kinds of scaffolds on bone defects repair.Micro-CT scan and three-dimensional reconstruction were used to observe the status of reconstruction of skull defect after 6and 12 weeks implantation.The immunofluorescence staining of osteocalcin(OCN)and nucleus on skull defect sites was observed to semi quantitative analysis the repairement of skull defect.Additionally,real time quantitative polymerase chain reaction(RT-PCR)was employed to detect the expression of alkaline phosphatase(ALP),type I collagen(Col I),bone sialoprotein(BSP)and Runt related transcription factor 2(Runx2)to quantitatively evaluate the effect of bone repair.Results:1 ? The investigation results indicated that the Col coating layer did not change significantly the surface morphology of porous scaffolds,maintaining the good interconnective pores but slightly lower average pore size.However,the presence of the Col coating layer remarkably increases the mechanical strength and hydrophilicity compared to the original PLGA/HA porous scaffold.In addition,the in vitro degradation experiments proved that the scaffolds with Col coating presented a faster degradation performance than that of the original PLGA/HA porous scaffold.And there is no significant effect of DGEA incorporation on the surface morphology,mechanical properties,hydrophobicity,and in vitro degradation behavior between the PLGA/HA/Col and PLGA/HA/Col/DGEA porous composite scaffolds.2?The results indicated that the PLGA/HA/Col/DGEA group showed the best repair of rat skull defect,and it healed almostly after 12 weeks.Compared with the blank group,PLGA/HA group and PLGA/HA/Col group,PLGA/HA/Col/DGEA porous composite scaffold has better capacity to effectively promote the migration of bone cells to the inside of the implanted scaffold,the differentiation of osteoblasts,and the mineralization behavior of new bone tissue as well.Thus,it is demonstrated that the Col coating can improve cell affinity and osteogenic induction of the porous scaffolds.Meanwhile,DGEA loading and releasing can further enhance the ability of porous scaffolds on repairing of bone tissue defects.Conclusions:This study provides a simple and effective method for the surface modification of the porous scaffold for bone repair.This method presents advantages on its simplicity and low cost,and also the thickness and drug loading of the coating layer can be controlled by the concentration of Col coating solution and DGEA.This composite porous scaffold has a better effect on bone repair and potential clinical application than the virgin commercial PLGA/HA.