Research On Preparation And Properties Of HA-based Artificial Bone Materials

Hydroxyapatite(HA)is an ideal artificial bone material,which is widely used for bone tissue repair and replacement due to its excellent biological properties.However,the mechanical properties and microstructure of pure HA are significantly different from that of human bone.In order to improve the mechanical properties of pure HA,carbon fiber(CF)was introduced to obtain CF reinforced HA composites(CF/HA).High-performance CF/HA composites were prepared by spark plasma sintering(SPS)to solve the problem of oxidation damage of CF during sintering caused by dehydroxylation and decomposition in CF/HA composites prepared by traditional methods(pressureless/hot pressing sintering).From the bionic perspective,in order to achieve a structure similar to bone tissue,NH4HCO3 was selected as the pore-making agent to prepare porous HA.The properties of CF/HA composites and porous HA were investigated.The main conclusions of this paper are listed as follows:(1)CF/HA composites were prepared by SPS,and the effects of the preparation process and fiber content on its microstructure,mechanical properties and surface roughness were investigated.The sintering principle and toughening mechanism of CF/HA composites prepared with SPS were also revealed.The results show that the matrix does not decompose in the CF/HA composites prepared by SPS,and the fiber is closely combined with the matrix,which helpful to enhance the toughening effects of the fiber.With the increase of temperature,the hardness and flexural strength of the composites increased.Meanwhile,as the fiber content increased from 0wt%to 0.8wt%,the hardness of the composites decreased from 633.3HV to 402.1HV,while the bending strength increased first and then decreased.At the sintering temperature of 830? and the CF content of 0.5wt%,the bending strength of the composites was 110.4MPa,the fracture toughness was 2.41MPa·m1/2,the brittleness index was 2.59?m·1/2,and the roughness was 0.558?m.The mechanical properties are significantly higher than those of pure HA and composites prepared by traditional sintering.The flexural strength and fracture toughness can be satisfied with human compact bone.(2)NH4HCO3 was selected as the pore-making agent to prepare porous HA,and the effects of pore forming agent content and sintering temperature on its pore structure and mechanical properties were investigated.The results show that the main component of porous HA is pure HA phase,the pore size is 20?200?m,and the distribution is uniform.With the increase of NH4HCO3 content from 0wt%to 70wt%,the number of pores increased significantly,but the integrity of pore structure gradually decreased.Meanwhile,the compression strength decreased from 127.89±9.83MPa to 4.07±0.49MPa.When the sintering temperature increased from 1100? to 1300?,the compressive strength of porous HA gradually increased.At the NH4HCO3 content of 30wt%and the sintering temperature of 1200?,the porosity(30%)and compressive strength(38.16±2.44mpa)of the porous HA can be satisfied with human cancellous bone.(3)The ability of CF/HA composites to promote cell osteogenic differentiation and biosafety were studied by in vitro cell culture.At the same time,the biomineralization ability and bone inductivity of porous HA were evaluated by in vitro via soaking in a simulated body fluid(SBF)and in vivo on tibial bone defect implantation in mice.Cell experiments showed that the MC3T3-E1 osteoblasts can adhere and proliferate well on the surface of CF/HA.MTT assay results showed the OD value of cells on CF/HA composites was significantly higher than that of the control group(pure HA prepared by pressureless).This result combined with alizarin red staining indicates that the CF/HA composites had the ability to promote osteogenic differentiation of cells and the basis of biosafety.An apatite layer was observed to form on the surface of porous HA in the SBF solution within a short period of time.The apatite layer becomes thicker with the increasing of the SBF immersion time.The vital signs of mice were within normal ranges after implantation of porous HA material in the tibia bone defect model.It has been observed that the porous HA material and bone tissue have been tightly combined by Micro-CT scanning and three-dimensional reconstructions.The CF/HA composites and porous HA with excellent mechanical and biological properties for different parts of bone replacement material application.It lays a theoretical foundation for the HA-based artificial bone materials to be used in clinical experiments.