| It’s well known that β-tricalcium phosphate(β-TCP)ceramic which has excellent biological properties is chemically similar to the inorganic composition of human bone tissue.β-TCP ceramic has wide application in bone defect repair and is currently an important biomedical ceramic material.As a bone repair material,the properties of compact structure,lack of mesopores and insufficient three-dimensional interconnectivity of the pores in β-TCP ceramic will lead to some disadvantages,such as slow degradation rate,poor angiogenesis and osteogenesis,which limit the application of β-TCP ceramic in bone repair.In this study,polymer microspheres with different volume fractions and different particle sizes were added to create mesopores(10-100 μm),and then β-TCP ceramics with different pore structures were constructed.The bone repair effect was improved by improving physical and chemical properties and biological properties of β-TCP ceramics.β-TCP powder which was obtained by chemical precipitation method and calcination treatment,was mixed with different volume fractions of polymer microspheres with a particle size of 70 μm,and after dry pressing and sintering,β-TCP ceramics with different porosities were obtained.With the increase in the amount of polymer microspheres,the porosity of β-TCP ceramics increased,on the contrary,the compressive strength decreased.The mesopores on β-TCP ceramic surface exposed more micropores(<10 μm)which were formed by sintering the ceramic matrix without fully densification,so the surface area and surface roughness increased and leading to the improvement of protein adsorption performance.Mouse bone marrow mesenchymal stem cells(m BMSCs)had good adhesion and spreading morphology in the mesopores on β-TCP ceramics,and the cytoskeleton and filopodia were obvious.The mesopores can promote cell proliferation and maintain good cell viability.β-TCP ceramic with20 vol.% addition of polymer microspheres had better ALP activity and higher expression of osteogenic differentiation-related genes(Col-I,OCN and OPN).Polymer microspheres(20 vol.%)with particle sizes of 10,20,40 and 70 μm were mixed with β-TCP powder to prepare β-TCP ceramics with different mesopore sizes in the range of10-100 μm by dry pressing and sintering.Due to the same addition amount,there were no significant difference in the porosity of β-TCP ceramics.However,as the mesopore size increased,the compressive strength decreased,while the surface roughness increased.As for the protein adsorption performance,the protein adsorption capacity of β-TCP ceramics with high surface area were higher in the first 24 hours,while β-TCP ceramics with small mesopores were higher in the last 24 hours.The results of m BMSCs cultured on β-TCP ceramics showed that mesopores were beneficial to cell adhesion and spreading,cytoskeleton and filopodia can be clearly seen in the mesopores near 40 and 70 μm;and cells showed good viability and proliferation on β-TCP ceramics.Compared with other mesopores,the ceramic with mesopores near 40 μm had better ALP activity and higher expression of osteogenic differentiation-related genes(ALP,Col-I,OCN,OPN,BSP and Runx-2).β-TCP ceramic scaffolds with three-dimensionally interconnected hierarchical pores were prepared by combining the methods of adding pore former and 3D printing.In addition to a large number of micropores(<10 μm)which were formed by sintering the ceramic matrix without fully densification,there were lots of evenly distributed mesopores with uniform pore size(～40 μm),as well as lateral and axial macropores(>100 μm)in β-TCP scaffolds.The existence of mesopores and the increasing size of macropores increased the porosity of β-TCP scaffolds,while the compressive strength decreased.Cells showed good adhesion,proliferation and viability when cultured on β-TCP scaffolds.β-TCP scaffolds with macropores of 500 μm upregulated the expression of osteogenic differentiation-related genes(Col-I and Runx-2),and the mesopores in the scaffolds with macropores of 300 μm could improve the expression of osteogenic differentiation-related genes(Col-I and Runx-2).After β-TCP scaffolds were implanted into canine muscles,the biodegradation of scaffolds with mesopores was more obvious at 4 weeks;while at 8 weeks,the biodegradation rate of scaffolds with macropores of500 μm was faster than that of scaffolds with macropores of 300 μm.For the performance of angiogenesis and ectopic osteogenesis,at 4 weeks,the number of new blood vessels of scaffolds with macropores of 500 μm was more than that of the scaffolds with macropores of 300 μm,but there was no trabecular bone formation in all scaffolds;at 8 weeks,mature bone tissue grown into all the scaffolds.Among them,the scaffold with mesopores near 40 μm and macropores of 500 μm had the highest amount of new bone,therefore,the scaffold had the best angiogenesis and ectopic osteogenesis performance.This experiment illustrates that β-TCP ceramic scaffolds with three-dimensionally interconnected hierarchical pore structure has good application prospect in the field of bone defect repair. |
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