A novel porous bioceramic scaffold by accumulating hydroxyapatite spheres for large bone tissue engineering. III: Characterization of porous structure.

Physical characteristics of bone tissue engineering scaffolds, including interconnectivity, microporosity, macroporosity, and pore geometry are known to play a crucial role in bone regeneration. In the present study, three-dimensional (3D) interconnected scaffolds were prepared by accumulating hydroxyapatite (HA) spheres in a titanium mesh tube (ф 1.5 × 3 cm). Three types of porous scaffolds were constructed using HA spheres with diameters of 1651-1981 μm, 830-1180 μm and a mixture of 1651-1981 μm and 830-1180 μm at a volumetric ratio of 1:1, respectively. The total porosity of the three scaffolds was 64.72%, 64.85% and 65.04%, while the macroporosity of the scaffolds was 37.56%, 38.86% and 38.01% by using images analysis of cross sections at various positions of the scaffolds. The variation curve of the macroporosity of the scaffolds along the axis perpendicular to the ground showed similarities to sinusoidal function curve. The macropore size was ranged from 0.73R to 2R (R means spheres radius). The average proportions of triangle macropores, quadrilateral macropores, as well as polygon macropores including pentagon, hexagon and irregular polygon macropores in the total macropore areas of each scaffold were 3.73 ± 0.96%, 10.03 ± 1.75% and 86.23 ± 2.71%, respectively. In addition, the macropore size, microporosity and total porosity could be controlled by modifying the diameter and microstructure of HA spheres when the macroporosity was the same. The study and analysis of macropore structure of the spheres accumulated scaffolds can not only guide the design and fabrication of 3D scaffolds for bone tissue engineering, but also benefit to further understand the impact of macropore structure in 3D scaffolds on osteogenesis.