Research On 3D Printing Tricalcium Phosphate Bone Tissue Engineering Scaffolds

Tricalcium phosphate(TCP)is similar to the chemical constituents of the bone inorganic phase.It is widely used because of its excellent biological activity and osteoconductivity.It is considered to be a promising bone defect repair material.How to prepare TCP bone scaffold with excellent mechanical properties is the focus of many researches.The mechanical properties of scaffolds are related to the characteristics of the material itself,the preparation method and the sintering process.In this study,the TCP scaffolds with interconnected pores were prepared based on 3D printing technology.The influence of sintering process and pore size on the mechanical properties of TCP scaffold was studied.The effect of adding Zinc oxide(ZnO)on TCP scaffold was further explored.Firstly,the TCP slurry which can be stably printed and the printing parameters are determined.TCP scaffolds were prepared by 3D printing and the sintering process of the prepared TCP scaffold was studied in detail.The pre-sintering temperature was obtained by thermogravimetric analysis of TCP scaffold.The morphology,mass and volume shrinkage,porosity,mechanical properties and degradation property of the scaffold was studied.The results showed that the scaffold sintered at 1150 ? had the maximum volume shrinkage,the minimum porosity and optimal mechanical strength,with the compressive strength of 6.52±0.84 MPa.In addition,the 1150 ? sintered scaffold degraded most slowly in the acidic environment compared to the scaffold sintered at the other temperatures,demonstrating its optimal mechanical stability over long-term implantation.Secondly,the TCP scaffolds with different pore sizes were prepared by changing the distance of fibers.The effects of different pore size structure on the porosity,mechanical properties and cell viability of scaffolds were investigated.The results showed that scaffolds with pore size 200 ?m had the minimum porosity,the best mechanical strength,and the compressive strength reached 6.02 ± 0.77 MPa,which could meet the requirements of human cancellous bone.The bone marrow mesenchymal stem cells(BMSCs)grew and adhered best on the 200 ?m scaffold compared with other pore size scaffold.The cells spread all over the surface of the scaffold,connected in a sheet,arranged closely,stacked in multiple layers,and the rate of proliferation was the fastest.Finally,the mechanical properties of different content of ZnO/TCP scaffolds showed that 2% ZnO can increase their compressive strength and compressive modulus respectively by 57.1% and 59.1% compared with the pure TCP scaffolds.The biocompatibility of the scaffold was evaluated by performing in vitro BMSCs coculture experiments with different ZnO/TCP scaffolds.The results showed that the biocompatibility of TCP scaffold was firstly increased then decreased with ZnO content,and little cells existed on 4% ZnO/TCP scaffolds.Therefore,2% ZnO was best both for the mechanical property and the cytoviability.In summary,the mechanical properties of 3D printed TCP scaffolds were enhanced by optimizing the sintering process,the pore size and the addition of ZnO.The study can give a theoretical foundation for further clinical application of the 3D printing TCP scaffold.