Effect of boron incorporation on the bioactivity, structure, and mechanical properties of ordered mesoporous bioactive glasses

B 2 O 3 doped (0.5-15 mol%) ordered mesoporous bioactive glasses (MBG) with the composition 80% SiO 2 -15% CaO-5% P 2 O 5 were synthesized via a sol-gel based evaporation-induced self-assembly process using the block-copolymer P123 as a structure directing agent and characterized by biokinetic, mechanical and structural investigations. Nitrogen physisorption isotherms and electron microscopy indicate no detrimental effect of B 2 O 3 on the ordered hexagonal pore structure. Boron incorporation increases both the bulk modulus and hardness of the glasses. In vitro bioactivity tests reveal a rapid initial release of Ca 2+ and PO 4 3− ions, followed by formation of hydroxyapatite carbonate within a few hours. Contrary to the tight incorporation of Al in Al-doped MBGs, the rapid release of borate species into simulated-body-fluid suggests loosely bound species localized at the internal surfaces of the mesopores. 29 Si, 11 B, 31 P, and 1 H solid state NMR spectroscopy reveal that the majority of the borate is present as anionic BO 4/2 − species. The need for charge compensation leads to an increase in the average degree of polymerization of the phosphate species for high boron contents. 11 B{ 31 P} rotational echo double resonance NMR results reveal the absence of B-O-P linkages. This structural model explains the rapid release of borate and the enhanced dissolution kinetics of the Ca 2+ and phosphate species. B 2 O 3 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.