In vitro and in vivo behaviour of zinc-doped phosphosilicate glasses

The aim of this work was to study the behaviour of zinc-doped phosphosilicate glasses based on Bioglass® 45S5. In vitro (in simulated body fluid), the reactivity was analysed by means of inductively coupled plasma spectrometry, environmental scanning electron microscopy–energy-dispersive spectroscopy (ESEM–EDS) and X-ray diffraction. In vivo (a rat implanted with glass), the reactivity and the tissue behaviour were analysed by conventional histology, histochemistry, microradiography and ESEM–EDS. The in vivo behaviour matches that in vitro perfectly; they show comparable glass degradation processes and rates, ruled by the amount of zinc in the glass. The reaction mechanism for the formation of a polymerized silica layer superimposed with a peripheral calcium phosphate layer is clearly substantiated by ESEM–EDS investigations. The crystallization of a biologically active hydroxyapatite (HA) layer is observed in both cases; the in vitro experiment shows the presence of HA after 4 days.