In Vitro and in Vivo Study of Selective Laser Melted Porous Ti-Ta-Nb-Zr Scaffolds for Repairing Bone Defects

Porous titanium-tantalum-niobium-zirconium (Ti-Ta-Nb-Zr) scaffolds are novel low-modulus metal scaffolds resembling cancellous bone, currently available for orthopedic applications. However, these scaffolds manufactured using traditional methods present disadvantages such as irregular pore size, unsuitable mechanical features, and poor connectivity between pores. Metal-based porous structures scaffolds for bone-defect repair can be fabricated using advanced additive manufacturing techniques. Here, we used selective laser melting (SLM) technology to manufacture porous Ti-Ta-Nb-Zr scaffolds with controlled pore size of 300~400 μm. We evaluated the SLM-manufactured scaffold mechanical properties and osteogenesis in vitro and osteointegration in vivo. Porous Ti-Ta-Nb-Zr scaffolds yielded superior cell-proliferation and cell-adhesion results with human bone mesenchymal stem cells (hBMSCs) as compared with porous Ti6Al4V scaffolds. The ALP-activity measurement and semiquantitative alizarin red staining demonstrated enhanced osteogenic differentiation of hBMSCs in the Ti-Ta-Nb-Zr group than in Ti6Al4V group. Moreover, after the porous Ti-Ta-Nb-Zr or control scaffold was implanted into a cylindric bone defect in the rabbit lateral femoral condyle, the radiography of new bone regeneration showed that the bone-volume/total-volume ratio was higher in Ti-Ta-Nb-Zr scaffolds than in Ti6Al4V scaffolds. Histological analysis further indicated that the Ti-Ta-Nb-Zr scaffolds promoted bone regeneration and osseointegration more effectively than Ti6Al4V scaffolds. Thus, the SLM-manufactured porous Ti-Ta-Nb-Zr scaffolds not only exhibited regular pore shape and excellent connectivity, but also featured a controllable elastic modulus and compressive strength, and the scaffolds yielded superior osteogenesis and osseointegration results in vitro and in vivo than porous Ti6Al4V. Our findings demonstrate that the SLM-manufactured porous Ti-Ta-Nb-Zr scaffold holds considerable potential for orthopedic clinical application.