Melt-derived bioactive glass fibers with rapid apatite-forming ability: spinnability, network structure, and in vitro performance

Bioactive glass fibers have been recognized as important reinforcing phases in biodegradable composites. In this study, two new bioactive glass compositions, 49S5 and 51S5, together with the classical 13–93 bioactive glass, were designed, prepared and further processed into continuous bioactive glass fibers. The fiber-forming ability, structure-property relationships, ion-release behavior, in vitro mineralization and cytocompatibility of the prepared fibers were evaluated. All three bioactive glass compositions could be drawn into smooth amorphous glass fibers by high-temperature melt drawing. The tensile strengths of the obtained 49S5 and 51S5 fibers reached 684 ± 215 MPa and 636 ± 200 MPa, respectively, showing only limited decreases compared with that of the 13–93 fiber. In addition, the simulated body fluid (SBF) immersion results showed that detectable hydroxyapatite-related features appeared in 49S5 and 51S5 fibers 6 and 4 days earlier than in 13–93, respectively, indicating that the in vitro mineralization abilities of the two newly designed fibers were enhanced. The ion-release and phosphate-consumption profiles supported the earlier apatite formation of these two fibers relative to 13–93. Structural analysis further showed that the newly designed bioactive glasses had lower degrees of network polymerization, which was consistent with the enhanced in vitro mineralization ability of the fibers. Extracts from all three bioactive glass fibers maintained L929 cell viability above 85%, indicating good cytocompatibility.