Metallic biomaterials have been used for biomedical applications due to excellent properties. However, although their excellent corrosion resistance these materials can be corrode when inserted into the human body and sometimes ions released can produce undesirable toxicity. Thus, titanium based alloys with nontoxic elements have been studied for these applications such as Ti-7.5Mo [1],[2],Ti-10Mo [3],[4],Ti-15Mo [5], Ti-29Nb-13Ta-4.6Zr [6] and Ti-13Nb-13Zr [7] with better bulk properties. However, the efficacy of osseointegration also is influenced by surface properties including chemical composition, wettability and topography [8],[9]. TiO2 nanotubes produced by electrochemical anodization have received considerable attention because they are mechanically and chemically stables, biocompatible and aiming the bone formation [10],[11]. Furthermore, titanium oxide nanotubes have potential application in drug delivery due to the control of the length and diameter of the nanotubes.The objective of this study was to evaluate the nanotubes growth on Ti-Mo alloys. Surfaces properties such as morphology, wettability and chemical composition were evaluated. Alloys were produced from sheets of commercially pure titanium (99.9%) and molybdenum (99.9%) according compositions evaluated: Ti-7.5Mo and Ti-15Mo. Materials were melted in arc melting furnace under an argon atmosphere. Ingots were cold worked by rotating swage into bars (10 mm of diameter) and discs with 3 mm of thickness were cut. Nanotubes were obtained by using electrochemical anodization and setup consisted as two-electrode configuration with platinum as cathode and alloy as anode was used. The electrolyte solution was glycerol aqueous solution containing 0.25%wt NH4F. Anodization was performed at applied voltage aoV and 20V for 24 hours at room temperature, the samples were rinsed in deionized water, air dried and annealed at 450°C in air for 1 hour. Surface topography and morphology of nanotubes were evaluated using field emission scanning electron microscopy and the wettability by using contact angle. The oxide layer chemical composition was evaluated by using XPS analysis. Figure 1 shows scanning electron microscope (SEM) images of the nanotubes formed on the surface of the Ti-7.5Mo . The high ordered TiO2 nanotubes arrays were formed. Ti15Mo exhibited ticker tubes wall for two conditions (Figure 2). For both alloys, a hydrophilic surface was observed after nanotubes growth.
The authors would like to thank Dr Pascale Chevallier (Université Laval, Quebec) for her help with the XPS analysis.
References:
[1] Escada A.L.A, Machado J.P.B, Schneider S.G, Alves Rezende M.C.R, Alves Claro A.P.R. Biomimetic calcium phosphate coating on Ti-7.5Mo alloy for dental application. Journal of Materials Science. Materials in Medicine 2011;22:2457-2465.
[2] Escada A.L.A, Rodrigues Jr D, Alves Claro A.P.R. Surface characterization of Ti 7.5Mo alloy modified by biomimetic method. Surface & Coatings Technology 2010;205:383-387.
[3] Alves Claro , Santana A.P.R.F.A, Rosa L.A.A, S.A. Cursino and E.N. Codaro. A study on corrosion resistance of the Ti–10Mo experimental alloy after different processing methods.Mater Sci Eng C 2004;24:693-696.
[4] Alves Rezende M.C.R, Alves Claro A.P.R, Codaro E.N, Dutra C.A.M. Effect of commercial mouthwashes on the corrosion resistance of Ti-10Mo experimental alloy. J Mater Sci Mater Med 2007;18:149-154.
[5] Niemeyer T.G, C.R. Grandini, L.M.C. Pinto, A.C.D. Angelo, S.G. Schneider. Corrosion behavior of Ti 13Nb 13Zr alloy used as a biomaterial.J Alloy Comp 2009;476:172-175.
[6] Lin, C.W., Ju, C.P., Lin, J.H.C. A comparison of the fatigue behavior of cast Ti-7.5Mo with c.p. titanium, Ti-6Al-4V and Ti-13Nb-13Zr alloys. Biomaterials 2005;26:2899-2907.
[7] Lin, D.J., Chuang, C.C., Lin J.H.C., Lee, J.W. Ju, C.P. Yin, H.S. Bone formation at the surface of low modulus Ti-7.5Mo implants in rabbit femur. Biomaterials 2007;28:2582-2589.
[8] Macák JM, Tsuchiya H, Schmuki P. High-aspect-ratio TiO2 nanotubes by anodization of titanium. Angew Chem Int Ed Engl. 2005;44: 2100–2102.
[9] Brammer KS, Oh S, Cobb CJ, Bjursten LM, van der Heyde H, Jin S. Improved bone-forming functionality on diameter-controlled TiO(2) nanotube surface. Acta Biomater. 2009;5:3215–3223.
[10] Popat KC, Eltgroth M, Latempa TJ, Grimes CA, Desai TA. Decreased Staphylococcus epidermis adhesion and increased osteoblast functionality on antibiotic-loaded titania nanotubes. Biomaterials 2007;28:4880-4888.
[11] Popat KC, Eltgroth M, LaTempa TJ, Grimes CA, Desai TA. Titania nanotubes: A novel platform for drug-eluting coatings for medical implants? Small 2007;3:1878-1881.