| In recent years,bioscaffolds fabricated by various technologies have become a new strategy for bone defect repair,gradually replacing autologous bone,allogeneic bone and metal materials.These scaffolds promote bone repair by creating three-dimensional space for cells to survive.Among them,3D printing technology can precisely manufacture complex shapes,pores,and microstructures,which is widely used in the manufacture of bone tissue engineering scaffolds.However,due to the existence of macropores,the simple scaffold structure often has defects such as insufficient mechanical properties and poor communication between pores,which hinder the differentiation and effective migration of osteoblast-related cells,as well as affecting the quality of bone repair.In this study,microspheres are covalently integrated into3 D printed frameworks to form multi-module 3D printed composite scaffolds in order to solve these problems.The physicochemical properties,cytological properties and in vivo bone repair properties of the composite system were evaluated.The details are as follows:(1)Preparation of multi-module 3D printed composite scaffolds and characterizations of the physicochemical and in vitro biological properties: In this study,methacrylated gelatin(Gel MA)was prepared and characterized,and then combined with the nano-hydroxyapatite(n HAP)to prepare different bioinks.The bioinks were screened and frame works(G10-F,G12-F)were fabricated using an extrusion 3D bioprinter.The chondroitin sulfate A(CSA)loaded microspheres(Mc)were prepared by a microfluidic device and covalently cross-linked into the macroporous structure of the frameworks to form different multi-module 3D printed composite scaffolds(G@M).In the results of in vitro experiments,the composite scaffold had a porosity of 60%-70%,reached swelling equilibrium within 12 hours,maintained slow degradation within 70 days,and was able to slowly release CSA.In addition,the G@M composite scaffolds exhibited excellent mechanical properties and anti-cyclic compression properties,as well as a compressive modulus(2.0 MPa-3.0 MPa)suitable for osteogenic differentiation.In cell experiments,G@M scaffolds enhanced cell adhesion,proliferation,and osteogenic differentiation of mouse embryo osteoblast precursor cells(MC3T3-E1).These results suggest that the G@M composite scaffolds have the potential to be a good implant for bone tissue engineering.(2)Application of G@M composite scaffolds loaded and unloaded with MC3T3-E1 in the bone repair in mouse: The composite scaffold(G10-F@Mc)composed of low-concentration inks had the most outstanding comprehensive performance in the in vitro physicochemical properties and biological performance experiments,and was included in the follow-up in vivo study.The G10-F@Mc scaffold was implanted into the calvarial defect site of C57BL/6 mouse.The results of new bone regeneration,blood biochemical markers,histological staining,and vascularization were assessed.In order to investigate whether the composite scaffold can be used as a cell carrier to play a positive role in the repair of bone defects,MC3T3-E1-loaded G10-F@Mc scaffold(G10-F@Mc@Cell)was further transplantation into the calvarial defects in mouse.The results showed that the G10-F@Mc composite scaffold could effectively repair skull defects and angiogenesis.Meanwhile,the composite scaffold has been shown to be a promoter of MC3T3-E1 osteogenic differentiation.The G10-F@Mc@Cell scaffolds grafted into bone defects also showed good bone repair and angiogenesis effects.In conclusion,several G@M composite scaffolds were designed,and their excellent physicochemical properties were demonstrated in this study.These composite scaffolds showed good biocompatibility and could effectively promote the osteogenic differentiation of MC3T3-E1.The in vivo experimental results showed that G10-F@Mc not only significantly promoted the repair of bone and vascular tissue when implanted alone,but also acted as a cell carrier to promote the repair of bone defect sites.These results indicate that the multi-module 3D printed composite scaffolds have good application prospects in the field of bone repair. |
