Nanostructure of Bioactive Sol−Gel Glasses and Organic−Inorganic Hybrids

The nanostructure of three bioactive materials, two sol−gel glasses in the SiO 2 −CaO and SiO 2 −CaO−P 2 O 5 systems and a SiO 2 −CaO−poly(dimethylsiloxane) organic−inorganic hybrid, has been studied for the first time by high-resolution transmission electron microscopy. The nanostructural characterization indicates that the addition of P 2 O 5 to the glass leads to crystallization of a silicon-doped calcium phosphate, while in the materials without any phosphorus content binary glass and hybrid calcium is located in an amorphous silica network. The different rates of positive bioactive response of both glasses (with and without phosphorus) are strongly correlated with their nanostructure since the distances between [SiO 4 4 - ] tetrahedra decrease when calcium is not present in the vitreous network and phosphorus bonds to calcium to form a silicon-doped calcium phosphate.