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.　©　2025