Tailoring of bioactive glasses for the release of nitric oxide as an osteogenic stimulus

Abstract

The production of bioactive glasses using the sol–gel process has increased the viability of using such glass-ceramics in the field of biomaterials. The mesoporous nature of the sol–gel structure enables the incorporation of specific stimuli into the glass for subsequent delivery at the local site upon implantation. This incorporation can be achieved by chemically patterning the sol–gel matrix with organosilanes that contain specific functional groups. This paper examines the synthesis and characterisation of a novel sol–gel-derived bioactive glass that can generate nitric oxide in an aqueous environment. Its synthesis is achieved via a two-step process. The first stage involves surface modification of the ternary 58S bioactive gel–glass (60 mol% SiO₂, 36 mol% CaO, 4 mol% P₂O₅) with an organosilane (3-aminopropyltriethoxysilane). The incorporation of an amino-functional group onto the surface of the gel–glass increases the site reactivity and affinity for nitric oxide. After modification with the organosilane, the bioactive gel–glass is subsequently reacted with molecular nitric oxide resulting in the formation of a nitric oxide-releasing biomaterial. Modification of the gel–glass surface does not alter the reaction mechanisms or bioactivity of the gel–glass, maintaining in-vitro behaviour typically associated with bioactive materials that exhibit both osteoconduction and osteoproduction.