Surface structure changes on aluminosilicate microspheres at the interface with simulated body fluid

Aluminosilicate microspheres obtained by spray drying were investigated in prospect of their potential biomedical applications. The as-prepared microspheres are amorphous. TEM and AFM were used to examine the morphology of the samples before and after immersion in simulated body fluid (SBF). The local structure changes as a function of microspheres composition and due to their immersion in SBF were investigated by 29Si and 27Al MAS–NMR. After SBF immersion, the silica network partially depolymerised by hydration/hydroxylation and the completely changed aluminium environment suggest a phylosilicate-like structure. 31P MAS–NMR analysis evidenced phosphorus ions incorporated in a new crystalline phase developed during SBF immersion.

► Aluminosilicate microspheres less than 20 μm were prepared by spray drying.
► Microspheres structure is modified after immersion in simulated body fluid (SBF).
► Silica network is partially depolymerized by hydration/hydroxylation in SBF.
► After SBF immersion the aluminum environment is completely changed.
► Apatite type nanocrystals grown on microspheres in SBF mark their bioactivity.