Strontium-delivering glasses with enhanced bioactivity: A new biomaterial for antiosteoporotic applications?

Bioactive glasses exhibit great performances for bone tissue regeneration. In biological conditions, they spontaneously bond to bone tissues while actively stimulating bone growth. Crucial parameters for the material's bioactivity are the kinetics of formation of the interfacial calcium phosphate layer at the glass surface, as well as the release of critical concentrations of ionic dissolution products capable of stimulating cellular responses. In this paper we report the remarkable bioactivity properties of strontium-delivering sol-gel-derived glasses in the SiO2-CaO-SrO system. The glasses were tested in vitro and the interface between the glass and the biological medium was chemically mapped using highly sensitive nuclear microprobes. We prove the ability of our materials to form a phosphocalcic layer at their periphery with increased kinetics of reaction. Our key result is the demonstration that Sr-doped glasses can deliver controlled doses of strontium toward the biological medium. That is the determinant for bone tissue regeneration, as far as strontium is known to positively act on bone remodeling. Sr-delivering glasses could further represent an alternative to the constraining oral administration of strontium in treatment of osteoporosis.