The formation of nanoscale structures in soluble phosphosilicate glasses for biomedical applications: MD simulations

The occurrence of chain-like fragments and rings in phosphosilicate glasses of known bioactivity was examined using classical molecular dynamics simulations, in order to reveal the possible effect of such nanostructures on the bioactive behaviour. Highly bioactive compositions display a large fraction of non-crosslinked, nonlinear chains of tetrahedra, which are not present in bio-inactive compositions. The low(er) energetic cost associated with the direct release of these silicate fragments into solution can assist the fast partial dissolution observed for bioactive glass compositions. Loss of bioactivity when the silicate content increases is accompanied by the transformation of these chains into small closed rings (3- to 8-membered), which appear to protect the silicate network from fast dissolution.