CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 39 (2013) 2003–2011 In vitro bioactivity and biocompatibility of a Co–Cr–Mo alloy after heat treatment in contact with different bioactive systems R. Martı´nez a , J.C. Escobedo a , D.A. Corte´s a , G.G. Alves b,c , A.B.R. Linhares c , J.M. Granjeiro b,c,d , M. Prado e , J.C. Ortiz a , J.M. Almanza a , E.M. Mu´zquiz-Ramos a,f,n a CINVESTAV-Unidad Saltillo, Carretera Saltillo-Monterrey Km 13, Apartado Postal 663, C.P. 25000 Saltillo, Coahuila, Me´xico b Department of Cell and Molecular Biology, Fluminense Federal University, Niteroi, Rio de Janeiro, Brazil c Clinical Research Unit, Antonio Pedro Hospital, Fluminense Federal University, Niteroi, Rio de Janeiro, Brazil d National Institute for Metrology, Quality and Technology, INMETRO, Duque de Caxias, Rio de Janeiro, Brazil e Military Institute of Engineering (IME), Prac - a General Tibu´rcio 80, CEP 22453-900, Urca, Rio de Janeiro, Brazil f Facultad de Ciencias Quı´micas, Universidad Auto´noma de Coahuila, Boulevard Venustiano Carranza y Jose´ Ca´rdenas, C.P. 25280, Saltillo, Coahuila, Me´xico Received 31 July 2012; accepted 17 August 2012 Available online 31 August 2012 Abstract As-cast samples of a cobalt base alloy (ASTM F-75) were heat treated in contact with different bioactive materials: (a) powder mixtures of b-tricalcium phosphate (TCP)–bioactive glass (BG) in different proportions (TCP–BG: 60–40, 70–30 and 80–20 wt%) and (b) mineral and synthetic wollastonite. Samples were packed with each bioactive material and heat treated for 1 h at 1220 1C. To characterize the in vitro bioactivity, heat treated samples were immersed in a simulated body fluid. After immersion, a ceramic layer containing Ca and P was formed on all samples. The thicker and more homogeneous layers, identified as apatite, were formed more rapidly on the heat treated samples in contact with 80TCP–20BG and synthetic wollastonite. The more bioactive coatings were selected for MC3T3 cell adhesion, proliferation and differentiation assays. Cell proliferation and alkaline phosphatase activity were not affected by the different coatings. Additionally, samples packed with 80TCP–20BG presented a higher cell adhesion than those packed with synthetic wollastonite. On the samples previously packed with synthetic wollastonite, a denser homogeneous Ca- and P-rich layer was formed 21 days after cell seeding and incubation in differentiative conditions. & 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Bioactivity; Cobalt base alloys; Cell culture; Bioactive ceramics 1. Introduction The Co–Cr–Mo alloy (ASTM F-75) [1] is one of the most widely employed alloys in the manufacture of hip replacement prostheses due to its high corrosion resistance as well as its relatively simple and the low cost processing method. One of the main disadvantages of this alloy is that it presents very low levels of osseointegration and, therefore, it is classified as a bioinert material [2] . To overcome this disadvantage, bioactive ceramic coatings are widely used [3] . As stated in the literature [4], a bone-like apatite layer is formed on the surface of bioactive materials such as hydroxyapatite (HA), tricalcium phosphate (TCP), wollas- tonite, bioactive glasses and glass-ceramics when these materials are in contact with real or simulated body fluids [5–9]. In previous works, it has been demonstrated the feasibility of trapping bioactive materials on the ASTM F75 alloy during casting or the required heat treatment for this alloy [10]. The alloy was also described as presenting a high in vitro bioactivity after immersion on simulated body fluid (SBF) [11]. Also, it was demonstrated that the www.elsevier.com/locate/ceramint 0272-8842/$ - see front matter & 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. http://dx.doi.org/10.1016/j.ceramint.2012.08.052 n Corresponding author at: CINVESTAV IPN-Unidad Saltillo, Carre- tera Saltillo-Monterrey, Km 13, Apartado Postal 663, C.P. 25000 Saltillo, Coahuila, Me´xico. Tel.: þ 52 844 4389600 x 9683; fax: þ 52 844 4389610. E-mail addresses: dora.cortes@cinvestav.edu.mx (D.A. Corte´s), emuzquiz@uadec.edu.mx (E.M. Mu´zquiz-Ramos).