Introduction: CaO-MgO-SiO2 system bioceramics show superior mechanical properties compared to other typical bioceramics such as calcium phosphates [1]. Studies have shown the excellent bioactivity (hydroxyapatite (HA) formation) of some Ca and Mg content silicate ceramics, such as wollastonite, diopside and akermanite. These materials can promote cell adhesion, proliferation, spreading, and differentiation, exhibiting various advantages for bone regeneration. Studies of the CaO-MgO-SiO2 system for biomedical application are an emerging area of biomaterial technology [2]. In this work CaO-MgO-SiO2 glass-ceramic powder was synthesized by a novel method: Ca and Mg were precipitated on SiO2 gel obtained from Na2SiO3. The glass-ceramic sintered at 1300 οC presented Wollastonite and akermanite bioactive phases. No toxicity was found in the cytotoxicity test with CHO (Chinese hamster ovary) cells. XRD, SEM (Scanning electron microscopy) and FTIR (Fourier Transform Infrared) investigations were conducted for bioactivity test by soaking the material in Simulated Body Fluid (SBF).
Materials and Methods: CaO-MgO-SiO2 glass ceramic was prepared by a new proposed method. In vitro cytotoxicity was performed with CHO-k1 as recommended by ISO 10993 [3]. In order to estimate the in-vitro bioactivity of the samples the SBF proposed by Kokubo et al. [4] was used for 7, 14 and 21 days. The experimental procedure is showed in Fig. 1.
Results and Discussion: Peaks of bioactive silicate ceramics; wollastonite, akermanite and dicalcium silicate were detected by XRD, in the ceramic of CaO-MgO-SiO2. FTIR spectra of the ceramic surface, after bioactivity test performed by soaking the samples in SBF for 7, 14 and 21 days showed phosphate characteristic absorption band at about 1034 cm-1, indicating the formation of HA. Fig.2 shows SEM micrographs of the glass-ceramic before (a) and after 14 days soaking in SBF (b). In Fig. 2(a) a continuously connected crystalline grains with open pores microstructure of sintered body is observed. In Fig. 2(b), particles with microspheres morphology [4] uniformly deposited on the surface are seen, confirm the presence of HA. According to ISO 10993-5, the cytotoxicity test revealed that the glass-ceramic did not show cytotoxicity.
Conclusion: A new method sol gel technique combined to precipitation, for preparing CaO-MgO-SiO2 powder was presented. A glass-ceramic with bioactive crystalline phases: wollastonite, akermanite and dicalcium silicate were obtained. According to ISO 10993-5, the material can be considered non cytotoxic. The bioactivity test of glass-ceramic reveled that, after 7 days soaking of the sample in SBF, HA was detected on the surface.
FAPESP- SÃO PAULO RESEARCH FUNDATION
References:
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