Mesoporous surface topography promotes bone cell differentiation on low elastic modulus Ti-25Nb-25Zr alloys for bone implant applications

Reducing the elastic modulus of metallic bone implants can decrease the stress shielding effect between the implants and bone tissue. Ti alloys containing elements without biological side effects have shown considerable potential as alternatives of biomedical Ti-Al-V alloys in bone implant applications. Ti alloys with porous surface topography have been shown to enhance cell response. This paper developed a rapid electrochemical anodization process for the creation of a low elastic modulus Ti-25Nb-25Zr (Ti25Nb25Zr) alloy with mesoporous topography for bone implant applications. We also investigated the effects of the mesoporous surface topography on bone cell differentiation. The surface mesotopography presented a pore size of <20 nm. Compared to untreated Ti25Nb25Zr alloys, the proposed electrochemical anodization treatment increased the formation of focal adhesion complex protein (vinculin) and the subsequent integrin-mediated pathway (i.e., the expression of focal adhesion kinase). This in-turn enhanced the expression of various osteogenic markers, including the gene and protein expression of osteopontin, bone sialoprotein, and type I collagen, from human bone marrow mesenchymal stem cells. An increase in osteogenic markers is expected to promote osseointegration on Ti25Nb25Zr alloys used in bone implant applications. To the best of our knowledge, this is the first study to enhance osteogenic gene and protein expression by producing a low elastic modulus Ti25Nb25Zr alloy with a mesoporous surface structure.