Synthesis and characterization of cerium-doped glasses and in vitro evaluation of bioactivity

The results of preparation, characterization and in vitro bioactivity evaluation of phosphosilicate glasses based on Bioglass(R) 45S5 (SiO2 45; Na2O 24.5; CaO 24.5; P2O5 6 wt%) doped during melting with (1.5-13.5 wt%) cerium dioxide (CeO2), has been reported. The choice of cerium was related to its low toxicity associated with bacteriostatic properties; cerium-doped bioactive glasses could be useful when implantation concerns local infected areas. The maximum value that permitted forming a homogeneous glass was 13.5 wt% and enabled us to get a better insight into CeO2 effect on the chemical behaviour of glasses. The as-quenched glasses were characterized by means of magnetic and spectroscopic measurements that revealed the prevailing presence of cerium (III). The bioactivity of the glasses was tested by soaking them in a simulated body fluid at 37 degreesC, under continuous stirring. ICP measurements were carried out for ion concentration determinations and the solution/glass interface was investigated by scanning electron microscopy equipped with energy dispersive analyzer (SEM/EDS technique) to check morphological modifications; the solids were investigated by means of X-ray powder diffraction and IR techniques. The results indicated that at low cerium content the glass degradation and repolymerization gave rise to an internal silicon-based layer and an external calcium-phosphate-based layer formed on the glass surface; high cerium content retards the glass degradation and gave rise to ceriumphosphate layer instead of calcium one. The cerium was never found in solution. For the reacted glasses, in the external layer, at 10% and 13.5% CeO2 contents the molar ratio Ca/P were approximate to1 and 0.8 respectively and the molar ratio Ce/P was approximate to0.3 in both cases. On the surface of the glasses with the highest cerium content it could distinguish new regular aggregates mainly formed by cerium and phosphate (Ce/Papproximate to3.5, Ca/Papproximate to0.6). In the cerium-free glass and with low cerium content (1.5 wt%) the calculated Ca/P ratio was 1.67, as calculated for pure hydroxyapatite. At low cerium content (BG-1.5 Cc) the glass behaviour was strictly similar to that of Bioglass(R) 45S5. (C) 2003 Elsevier Science B.V. All rights reserved.