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 Na 2 O−P 2 O 5 −B 2 O 3 −SiO 2 system over a broad compositional space. P 2 O 5 preferentially tends to attract network modifier species, thus resulting in a repolymerization of the silicate network and a restructuring of the borate component. 11 B{ 31 P} and 31 P{ 11 B} dipolar recoupling experiments suggest that the ability of glasses to incorporate P 2 O 5 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.

The beneficial effect of magnesium oxide upon the performance of crack-resistant oxide glasses has been explored in a series of aluminoborosilicate glasses with the compositions 60SiO2–(20 – x)­Al2O3–xB2O3–20Na2O and 60SiO2–(20 – x)­Al2O3–xB2O3–10Na2O–10MgO. The simultaneous presence of both boron and aluminum oxides in these glasses produces a synergetic effect upon crack resistance (CR), whose structural origins are being explored by detailed 11B, 23Na, 27Al, and 29Si single and double resonance solid-state NMR studies. Aluminum is exclusively four-coordinated, whereas boron is found in both three- and four-coordination. Substitution of B2O3 with Al2O3 and Na2O with MgO leads to a dramatic reduction of N 4, the fraction of four-coordinate boron, accompanied by an increase in CR. 11B/27Al double resonance NMR studies show only weak interactions between the boron oxide and aluminum oxide components, giving no evidence of the formation of new structural units not already realized in the ternary aluminosilicate and borosilicate glass systems. Rather, the effect of magnesium can be related to a dramatic reduction of the fraction of four-coordinate boron species compared to the analogous sodium-based system. This reduction results from a preference of the sodium ions to charge-compensate anionic AlO4/2 – species, combined with an unfavorable interaction of four-coordinate boron with Mg2+. Overall, the results give important insights into the Mg-driven structural network changes in this four-component glass system, providing a structural rationale for the dramatic effect of magnesium upon the mechanical properties of these glasses.

The local structure of the model glasses (NaPO 3 ) 1−x -(AlF 3 ) x (0 ≤ x ≤ 0.4), prepared by standard melt-cooling, was extensively investigated by high-resolution solidstate nuclear magnetic resonance (NMR) including advanced double-resonance techniques. This glass system offers the opportunity of studying five different heteronuclear distance correlations (Na−F, Na−P, P−F, Al−F, and P−Al) by 10 distinct double-resonance experiments, involving all of the constituent elements present. 27 Al MAS-NMR data indicate that aluminum is predominantly six-coordinated. According to 27 Al{ 31 P} and 27 Al{ 19 F} rotational-echo double-resonance (REDOR) spectroscopic results, two to three Al−F and three to four Al−O−P linkages occur in these glasses, independent of composition x. 19 F MAS-NMR spectra show the presence of terminal P-bound and Al-bound fluorine species. A small amount of fluorine bridging to two aluminum octahedra, which could be assigned based on 19 F{ 27 Al} and 19 F{ 31 P} REDOR experiments, was also detected. 19 F{ 23 Na} REDOR experiments indicate that the Al-bound terminal F atoms interact significantly more strongly with sodium ions than the P-bonded terminal F atoms, which is consistent with local charge considerations. On the basis of the detailed quantitative dipole−dipole coupling information obtained, a comprehensive structural model for these glasses is presented.

B2O3 doped (0.5–15 mol%) ordered mesoporous bioactive glasses were synthesized via sol–gel based evaporation-induced self-assembly using P123 as a structure directing agent and characterized by biokinetic, mechanical and structural investigations.