The effect of pore size and porosity of Ti6Al4V scaffolds on MC3T3-E1 cells and tissue in rabbits

Electron beam melting (EBM) allows the fabrication of specific porous titanium implants, whereas their in vitro and in vivo biological performance should be further investigated. In this study, we examined the porous Ti6Al4V scaffolds (low, 334.1 μm pore size with 55.4% porosity; middle, 383.2 μm pore size with 65.2% porosity; and high, 401.6 μm pore size with 78.1% porosity) fabricated through EBM. The structural characterization and mechanical properties of porous Ti6Al4V scaffolds were measured through micro-computed tomography (micro-CT), scanning electron microscopy, and a material testing system. MC3T3-E1 cells were used to assess the proliferation and differentiation of the cells on different scaffolds at day 7 and day 14 based on the expression levels of genes, including alkaline phosphatase, bone morphogenetic protein-2, osteopontin and runtrelated transcription factor-2. Rabbits with distal femoral defects were utilized to evaluate bone ingrowth in the porous titanium. All of the samples were subjected to micro-CT and histological analysis after 12 weeks. Results showed that compressive Young’s modulus of 0.3–1.1 GPa was similar to the trabecular bone. The three types of porous Ti6Al4V scaffolds were inclined to promote cell proliferation, whereas cell differentiation and bone ingrowth into the porous scaffolds were biased to the porous titanium with relatively large pores and porosity (middle and high). This study implied that the present porous implant design, which had the combined advantages of different pore sizes and porosity, might be meaningful and promising for trabecular bone defect restoration.