Synthesis and characterization of novel mesoporous strontium-modified bioactive glass nanospheres for bone tissue engineering applications

Mesoporous bioactive glass nanoparticles (MBNs) have recently gained increasing attention as nanocarriers for co-delivery of therapeutic ions and molecules for treatment of hard tissue injuries. In the current study, novel Sr-substituted silica-based MBNs were synthesized through a template assisted sol-gel process. The results showed that the prepared nanoparticles are amorphous with a spherical morphology and an average size between 86 and 115 nm, and their microstructure is not considerably changed by Sr incorporation. The produced nanoparticles have a disordered mesoporous structure and notably better dispersion, as well as higher textural properties including specific surface area (408–480 m2/g) and pore volume (0.54–0.62 cm3/g), compared to most Sr-modified mesoporous bioactive glasses synthesized to date. In-vitro mineralization experiments revealed that the synthesized nanospheres exhibit an excellent bioactivity within 3 days immersion in simulated body fluid (SBF) solution, irrespective of the Sr content. Moreover, the prepared nanospheres are ideal platforms for a sustained release of ibuprofen in SBF up to 7 days. In-vitro cell viability results proved that the ionic extracts of the Sr-loaded MBNs can markedly increase the proliferation of adipose tissue-derived stem cells (ADSCs), and Wharton's jelly-derived stem cells (WJSCs) compared to the performance of unloaded MBNs, at certain concentrations. Due to the spherical shape, excellent dispersion and promising physiochemical/biological properties, the newly synthesized Sr-loaded MBNs are encouraging filler materials for fabrication of nanocomposite scaffolds for treatment of bone defects.