Effect of nitrogen on the structure evolution and biological properties of mesoporous bioactive glass nanospheres: Experiments and simulations

Mesoporous bioactive glasses (MBGs) have displayed great potential in dental restorations and bone regeneration for their controllable structure and great bioactivity. In this work, we have systematically investigated the effect of nitrogen on structure evolution, apatite-forming ability and cytotoxicity in MBG by successfully preparing the N-containing MBG nanospheres by a modified sol-gel method. It is interesting to demonstrate that all obtained samples exhibit uniform interstitial mesoporous nanospheres microstructure, with the particles size increases as the nitrogen addition increases from 5 to 15 mol.%. Notably, a large amount of blooming flower-like hydroxyapatite deposited on the surface of 15N-MBG after immersed in simulated body fluid for 7 days, exhibiting excellent apatite-forming ability. It is highlighted that the incorporation of nitrogen can stimulate cell proliferation at early incubation time. Moreover, all the MBGs have no obvious inhibitory impact on the hPDLCs growth at extracted concentration. Furthermore, via glass network connectivity analysis from molecular dynamics simulations, the decrease of network connectivity caused by the incorporation of nitrogen could provide looser glass network and higher bioactivity, which explains the experimental results well.