Combined Experimental and Computational Approach toward the Structural Design of Borosilicate-Based Bioactive Glasses

Transitioning beyond a trial-and-error based approach for the compositional design of next-generation borosilicate-based bioactive glasses requires a fundamental understanding of the underlying compositional and structural drivers controlling their degradation and ion release in vitro and in vivo. Accordingly, the present work combines magic-angle spinning (MAS) NMR techniques, MD simulations, and DFT calculations based on GIPAW and PAW algorithms, to build a comprehensive model describing the short-to-medium-range structure of potentially bioactive glasses in the Na2O-P2O5-B2O3-SiO2 system over a broad compositional space. P2O5 preferentially tends to attract network modifier species, thus resulting in a repolymerization of the silicate network and a restructuring of the borate component. B-11{P-31} and P-31{B-11} dipolar recoupling experiments suggest that the ability of glasses to incorporate P2O5 without phase separation is related to the formation of P-O-B(IV) linkages integrated into the borosilicate glass network. An analogous approach is used for elucidating the local environments of the Na+ network modifiers. This work, along with future studies aimed at elucidating composition-structure-solubility/bioactivity relationships, will lay the foundation for the development of quantitative structure-property relationship (QSPR) models, thus representing a leap forward in the design of functional borosilicate bioactive glasses with controlled ionic release behavior.