Fabrication and characterization of sol–gel derived 45S5 Bioglass®–ceramic scaffolds

Although Bioglass® has existed for nearly half a century its ability to trigger bone formation and tuneable degradability is vastly superior to other bioceramics, such as SiO2–CaO bioactive glasses. The sol–gel process of producing glass foams is well established for SiO2–CaO compositions, but not yet established for 45S5 composites containing Na2O. In this work the sol–gel derived 45S5 Bioglass® has for the first time been foamed into highly porous three-dimensional scaffolds using a surfactant, combined with vigorous mechanical stirring and subsequent sintering at 1000 °C for 2 h. It was found that the mechanical strength of the sintered sol–gel derived Bioglass® scaffolds was significantly improved, attributable to the small fraction of material on the pore walls. More importantly, the compressive strength of the three-dimensional scaffolds produced by this surfactant foaming method could be predicted using Gibson and Ashby’s closed cell model of porous networks. A comparative experiment revealed that ion release from the sol–gel derived Bioglass® foams was faster than that of counterparts produced by the replication technique. In vitro evaluation using osteoblast-like cells demonstrated that the sol–gel derived 45S5 Bioglass foams supported the proliferation of viable cell populations on the surface of the scaffolds, although few cells were observed to migrate into the virtually closed pores within the foams. Further work should be focused on modifications of the reaction conditions or alternative foaming techniques to improve pore interconnection.