Engineering bioactivity and antibacterial properties in mesoporous borosilicate glass nanospheres through magnesium substitution

Mesoporous bioglasses (MBGs) have emerged as pivotal materials for bone tissue engineering due to their exceptional osteogenic properties and tunable morphology. In this study, the magnesium (Mg)-substituted mesoporous borosilicate glasses (MBSGs) with compositions of (50-x)SiO₂–30.8CaO-10B₂O₃–9.2P₂O₅-xMgO (x = 0, 1, 5, and 10 mol.%) have been developed using a modified alkali-catalyzed sol-gel co-template method. The effects of MgO concentration on microstructure and biological properties were systematically investigated. The resulting Mg-substituted MBSGs maintained a uniform spherical morphology of ∼80 nm diameter, while demonstrating enhanced porosity and specific surface area. These structural advantages facilitated rapid hydroxyapatite formation within 3 days in simulated body fluid, confirming superior in vitro bioactivity. Biological evaluation revealed that the 5 mol.% MgO sample optimally promoted MG-63 osteosarcoma cell proliferation. Furthermore, antibacterial activity against S. aureus showed MgO concentration-dependent enhancement, achieving 99.99 % inhibition at 0.1 mg/L. Ab initio molecular dynamics simulations attributed the improved bioactivity to reduced network connectivity upon Mg incorporation. These findings highlight the potential of Mg-substituted MBSG nanospheres as multifunctional biomaterials combining excellent bioactivity and antibacterial properties for bone regeneration and dental applications.