Sr-containing hydroxyapatite: morphologies of HA crystals and bioactivity on osteoblast cells |
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Authors: | Valentina Aina Loredana Bergandi Gigliola Lusvardi Gianluca Malavasi Flora E Imrie Iain R Gibson Giuseppina Cerrato Dario Ghigo |
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Affiliation: | 1. Department of Chemistry, Università degli Studi di Torino, Via P. Giuria 7, 10125 Torino, Italy;2. Centre of Excellence NIS (Nanostructured Interfaces and Surface) Università degli Studi di Torino;3. INSTM (Italian National Consortium for Materials Science and Technology), UdR Università di Torino;4. Department of Oncology, Università degli Studi di Torino, Via Santena 5/bis, 10126 Torino, Italy;5. Department of Chemical and Geological Sciences, Università di Modena and Reggio Emilia, Via Campi 183, 41125 Modena, Italy;6. School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom |
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Abstract: | A series of Sr-substituted hydroxyapatites (HA), of general formula Ca(10 ? x)Srx(PO4)6(OH)2, where x = 2 and 4, were synthesized by solid state methods and characterized extensively. The reactivity of these materials in cell culture medium was evaluated, and the behavior towards MG-63 osteoblast cells (in terms of cytotoxicity and proliferation assays) was studied. Future in vivo studies will give further insights into the behavior of the materials.A paper by Lagergren et al. (1975), concerning Sr-substituted HA prepared by a solid state method, reports that the presence of Sr in the apatite composition strongly influences the apatite diffraction patterns. Zeglinsky et al. (2012) investigated Sr-substituted HA by ab initio methods and Rietveld analyses and reported changes in the HA unit cell volume and shape due to the Sr addition.To further clarify the role played by the addition of Sr on the physico-chemical properties of these materials we prepared Sr-substituted HA compositions by a solid state method, using different reagents, thermal treatments and a multi-technique approach. Our results indicated that the introduction of Sr at the levels considered here does influence the structure of HA. There is also evidence of a decrease in the crystallinity degree of the materials upon Sr addition. The introduction of increasing amounts of Sr into the HA composition causes a decrease in the specific surface area and an enrichment of Sr-apatite phase at the surface of the samples. Bioactivity tests show that the presence of Sr causes changes in particle size and/or morphology during soaking in MEM solution; on the contrary the morphology of pure HA does not change after 14 days of reaction. The presence of Sr, as Sr-substituted HA and SrCl2, in cultures of human MG-63 osteoblasts did not produce any cytotoxic effect. In fact, Sr-substituted HA increased the proliferation of osteoblast cells and enhanced cell differentiation: Sr in HA has a positive effect on MG-63 cells. In contrast, Sr ions alone, at the concentrations released by Sr-HA (1.21–3.24 ppm), influenced neither cell proliferation nor differentiation. Thus the positive effects of Sr in Sr-HA materials are probably due to the co-action of other ions such as Ca and P. |
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