3D Printing SA/CS/Gel Hydrogel-based β-TCP Composite Scaffold For The Repair Of Large Bone Defect

The problem of bone loss caused by severe trauma and infectious diseases is a significant problem affecting people’s health.According to the different sizes of bone loss,it can be divided into minor bone loss problems and large bone loss problems.Compared with the problem of small-size bone loss,the self-healing ability of large bone loss is poor,and the current traditional coping strategies are challenging to meet the huge clinical needs.With the continuous development of material science and technology,the concept of the artificial bone scaffold has been proposed to deal with the problem of multiple large bone loss.Among the many artificial bone scaffold materials,hydrogel materials with excellent biological properties and biomimetic structural properties formed by cross-linking of natural polymers have been the focus of research in recent years.There are various processing methods for hydrogel-based artificial bone scaffolds,but they all have some limitations.The emergence of 3D printing technology provides another idea for preparing artificial bone scaffolds.However,the low printing accuracy of 3D printing hydrogel-based scaffolds and the poor performance and degradation stability of the scaffolds caused by the material itself limit the development of 3D printing hydrogel materials in bone tissue repair.In this study,taking the limitation of sodium alginate composite hydrogel as a breakthrough,to improve the poor cell adhesion and unstable degradation rate of sodium alginate,sodium alginate was mixed with chitosan(CS)and gelatin(Gel)in a particular proportion.At the same time,to enhance the scaffold’s structural stability and mechanical properties of the scaffold so that the scaffold can be used to repair large bone defects,30,40,50%bioceramic β-tricalcium phosphate(β-TCP)was added to the hydrogel to prepare bio-ink.The composite hydrogel was prepared by adopting the double cross-linking strategy of acid-calcium ion cross-linking and glutaraldehyde cross-linking.The composite hydrogels’ gel properties,micro-morphology,infrared spectrum,hydrophilicity,and swelling properties were detected and analyzed.Then use 3D printing technology combined with a pre-cross-linking strategy to print stents with a specific internal and external structure.Firstly,the surface morphology of the scaffold was observed,the scaffold’s shrinkage,mechanical properties,and porosity before and after freeze-drying were analyzed,and the degradation and mineralization ability of the scaffold in vitro was evaluated.The drug loading was carried out by using the swelling characteristics of the hydrogel in the scaffold.The cytological evaluation of each scaffold component was carried out,including cell adhesion,cytotoxicity,and cell proliferation of the scaffolds—detection and evaluation of alkaline phosphatase activity and osteogenesis-related gene expression.(1)The choice of cross-linking strategy makes the biological ink have excellent gel properties.The results of infrared spectrum analysis show that after cross-linking the posttreatment process,the composition and structure of the material are stable,and there is no formation of new substances.The prepared hydrogel-based composite biological ink material has excellent hydrophilicity,and the addition of β-tricalcium phosphate significantly regulates the swelling behavior of the scaffold.(2)The choice of pre-crosslinking strategy makes the scaffold have excellent forming ability.The 3D-printed scaffold has 75% porosity and the highest compression modulus of52.225 MPa,which meets the requirements of cancellous bone.At the same time,the scaffold shows excellent mineralization ability and degradation characteristics in vitro,and it is found that the addition of β-tricalcium phosphate significantly improves the mechanical properties of the scaffold.Moreover,effectively maintain the scaffold’s morphological and mechanical stability in the degradation process.(3)The biological evaluation results of the scaffolds showed that all the components were non-toxic and had excellent cell adhesion and cell proliferation,among which the components with β-tricalcium phosphate showed better performance.The scaffold containing EGCG was loaded by the swelling property of hydrogel,the experimental results show that the drug-loaded scaffold can effectively promote cell proliferation and promote the activity of alkaline phosphatase and the expression of related genes.