Abstract
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.
Highlights
Advances in materials science and physical metallurgy as well as technical progress in manufacturing technologies (e.g. 3D printing) are enabling the development of new Titanium (Ti) alloys for bioengineering applications
Pre-osteoblasts (MC3T3-E1) incubated on the binary Ti-e40Nb strongly preferred to attach in regions depleted of Nb
The cells incubated on the binary Ti-e10Sn were less discerning towards chemical composition, and no preference was found on the ternary alloy
Summary
Advances in materials science and physical metallurgy as well as technical progress in manufacturing technologies (e.g. 3D printing) are enabling the development of new Titanium (Ti) alloys for bioengineering applications. The aim is to minimise stress-shielding, decreasing the risk of loosening, osteopenia, implant rejection and infection/inflammation, and to foster good integration of the tissue onto the substrate This has been pursued by the addition of β-stabilising elements, such as Niobium (Nb), to Ti since the β-Ti alloys present lower values of stiffness as defined by the alloy bulk properties [1,2,3,4,5]. Judicious mixtures of β-stabilisers with other elements such as Tin (Sn), can create duplex-phase alloys (β + α′′) which have been shown to further decrease stiffness and possess high strength [5,6,7] This is an ideal combination for bioengineering applications that surpasses the properties of c.p. Ti when aiming to achieve those of bone tissue
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