Roles of strontium and hierarchy structure on the in vitro biological response and drug release mechanism of the strontium-substituted bioactive glass microspheres.

The strontium (Sr) substituted bioactive glasses (BGs) have inimitable advantages for bone generation, but the influences of Sr substitution on bioactivity and biocompatibility are still in debate. A brand novel porous microstructure of Sr-substituted BG microspheres was prepared by an electro-spraying technique combined with phase inversion, in which in vitro biological response (bioactivity, cell viability, alkaline phosphatase (ALP) activity and extracellular matrix (ECM) mineralization) and drug release were clarified in view of physical chemistry and ionic release behavior. The electro sprayed bioactive glass (ESBG) microspheres involved three characteristic pores: <100 nm, 100-1000 nm and >1000 nm. The Sr substitution on molar basis hindered the bioactivity of the samples in some extent but the cell behavior of the MC3T3-E1 cells was not significantly discouraged. The drug release profile was also controlled by amount of Sr substitution. However, the porous structure of the microspheres conferred improvement in bioactivity and provided a distinct three-stage drug release mode. Therefore, the Sr substituted ESBG microspheres may provide an effective way to deliver a steady supply of therapeutic ions and drugs in bone implantation patients.