Tuning biodegradability and biocompatibility of mesoporous silica nanoparticles by doping strontium

Mesoporous silica nanoparticle (MSN), one of the most widely used nanomaterials, is of poor biodegradability in vivo due to its highly stable Si–O–Si structure. Here, the structural stability of Si–O–Si was regulated by doping strontium ion. Sr-doped MSNs (Sr-MSNs) were synthesized by a cetyltrimethylammonium-bromide-mediated template method and their phase, morphology, structure, physicochemical properties, in vitro degradability and cytocompatibility were investigated. Results indicated that Sr2+ was successfully incorporated into MSN with the collapse of the ordered mesoporous structure. Sr-doping significantly improved the specific surface area, in vitro degradability and cytocompatibility of MSN in a Sr-content-dependent manner. Particularly, excessive Sr-doping gave rise to generating impure strontium silicate which converted into disordered amorphous silica during degradation and hindered the biodegradable behaviors of MSN. Hence, the synthetic Sr-MSNs with excellent surface nature, biodegradability and biocompatibility were supposed to be applied as potential carriers for the controllable release of drugs and ions in numerous clinical applications.