Physico-chemical characterisation of Ti-Nb-Sn alloys surfaces and their osteogenic properties

Implanted tissue engineering devices interact with the host tissue through their surface in the first instance. Surface chemistry triggers cell activities that stimulate bone tissue-formation mechanisms for osteoblast maturation. In this work, the bioactivity of binary Ti-40Nb and Ti-10Sn and ternary Ti-10Nb-5Sn alloys, candidates for bioengineering applications, has been studied on their surface with a view to establish their osteogenic potential compared to that of c.p. Ti. Cellular population growth was used to assess proliferative and differentiative phenotypes (via protein and Alkaline Phosphatase markers), coupled with gene expression (i.e. Runx2 and OCN) to confirm maturation. The results show that Sn-containing alloys support cell bioactivity, increase metabolic activity (i.e. metabolites content) that indicate their preferred glycolytic pathway, promote cell attachment, differentiation and osteoblast maturation. Ti-40Nb, although also non-cytotoxic, retards osteoblastic differentiation and maturation. To elucidate the features that underpin this difference, their physical (i.e. wettability, electrical state near the surface) and chemical properties (i.e. oxide layer thickness and composition) were analysed independently from topology and roughness. It was concluded that composition (esp. TiO2 % content) is a more important factor than wettability and oxide layer thickness, and that although a negatively-charged surface (represented by the surface ζ potential) was preferential for cell bioactivity given its protein-adsorption readiness, its magnitude was not a defining cause.