| Bone defect and bone tumor are two common bone tissue diseases in clinical orthopedics.When the size of bone defect exceeds the critical value,it will be difficult to heal itself.Bone repair scaffolds are the most promising therapeutic means to solve the problem of bone defects,which can achieve complete regeneration of bone tissue.The interconnected porous structure and surface micro-nano structure of bone repair scaffolds are important factors that mediate cell behavior and new bone formation,and have important scientific significance and clinical value for advancing the osteogenesis process.Calcium silicate(CSi)has excellent osteoconductivity,osteoinductivity and degradability,and has broad application prospects in the field of bone repair.However,the degradation rate of CSi ceramics is too fast,which leads to the rapid decay of the mechanical properties of the scaffold,and at the same time,it is easy to release excess ions into the body fluid environment,which affects cell activity and osteogenesis.Therefore,in this study,3D printing technology and surface modification technology were combined to prepare interconnected porous structure bone repair scaffolds with micro-nano-structured surfaces,and the effects of surface modification on scaffold degradation performance,in vitro cell behavior and in vivo bone regeneration were investigated.It can provide an important scientific basis for the preparation and surface structure construction of customized bioactive ceramic scaffolds.Calcium silicate scaffolds with interconnected porous structures and calcium silicate scaffolds assisted by water-soluble sintering aids were prepared by 3D printing.The effects of printing and sintering process parameters on the accuracy of the shape and internal microstructure of the scaffold were studied,and the customized design and printing of various tissue models were realized.A water-soluble sintering aid-assisted sintering process method suitable for the 3D printing process was established,and the assisted sintering mechanism of the water-soluble sintering aid was studied.The addition of 1% sodium carbonate can obtain bone repair scaffolds with significantly improved mechanical properties.At the same time,the scaffolds have excellent in vitro hydroxyapatite(HA)mineralization ability and long-term mechanical properties maintenance ability.The degradation performance and biological properties of CSi scaffolds were regulated by surface coating and surface micro-nano structure modification,respectively.The surface components of CSi scaffolds were modified by immersion in polycaprolactone(PCL)solution.The PCL-coated scaffolds effectively controlled the degradation rate of the scaffolds,controlled the ion concentration and p H value in the medium,and promoted cell proliferation and growth.Bone differentiation capacity.The HA micro-nanostructured layer was constructed on the surface of the CSi scaffold by the hydrothermal method.By adjusting the composition of the hydrothermal phosphate solution,the CSi scaffold with nanosheets,micro-nano hybrids,nanospheres,and microsphere-like HA surfaces was obtained.The HA surface layer helps to improve the degradation performance of the scaffold and regulate the cell behavior.The cells exhibit the best adhesion,spreading,proliferation and osteogenic differentiation properties on the scaffold with nanosheet HA surface,which is expected to be applied to the treatment of bone defects.regeneration repair.For the self-developed hydrothermal system,the growth mechanism of HA crystals under the control of polyphosphate was studied.Polyphosphates have strong calcium ion complexing ability and thermal stability,and can form stable watersoluble complexes with calcium ions.When hydrothermally,polyphosphates have a slow decomposition process,gradually release phosphate ions,combine with calcium ions to form nuclei and gradually grow.The complexation ability and thermal stability of different polyphosphates affect the growth process of HA crystals.Cell co-culture studies were performed on HA with different structures,and it was found that the size and microstructure of HA significantly affected the adhesion and spreading of cells,and HA with suitable size and microstructure significantly promoted the endocytosis of cells and could significantly upregulate the mesenchyme Osteogenic-related gene expression of stem cells mediates osteogenic differentiation of stem cells.The CSi scaffold with double surface layer structure was constructed and its in vivo bone repair performance was studied.Using the 3D printed CSi scaffold as the base material,the CSi/HA scaffold was prepared by a hydrothermal method.Graphene oxide(GO)surface layer structure was constructed on the surface of CSi/HA scaffold by chemical grafting method,and CSi/HA/GO double surface layer scaffold was successfully prepared.Through in vitro cell co-culture experiments,it was found that the double surface layer effectively improved the protein adsorption capacity,cell activity,cell adhesion and osteogenic gene expression of the scaffold.In vivo bone defect repair experiments in animals found that there was no inflammatory response and fibrous connective tissue encapsulation problems after stent implantation,and the double surface layer effectively promoted the formation of new bone and the increase of bone mass in vivo.In this paper,the preparation and modification of CSi scaffolds were systematically studied by 3D printing and surface modification technology,and the3 D printing of CSi scaffolds assisted by water-soluble sintering additives and the construction of surface micro-nano structures of CSi scaffolds controlled by phosphate solution were proposed.Innovative ideas such as the construction of double surface layers of CSi scaffolds by chemical grafting of graphene oxide,provide a solid theoretical and experimental basis for the preparation and modification of bioceramic material scaffolds,and are of great significance for promoting the clinical application of bone tissue engineering. |
