Novel bioactive nanocomposite cement formulations with potential properties: incorporation of the nanoparticle form of mesoporous bioactive glass into calcium phosphate cements

Injectable calcium phosphate cements (CPCs) with strong mechanical properties and improved biological performance have the potential to be extensively used for bone regeneration. Although many additive materials have been incorporated into CPCs in order to achieve improvements in their mechanical and biological properties, somehow the results have not been fully satisfactory. Here we focus on using the nanoparticle form of mesoporous bioactive glasses (mBGn) as additive nano-components for alphatricalcium phosphate-based CPCs. The effects of mBGn incorporated up to 10 wt% into CPCs were examined in depth with respect to the setting time, morphology, injectability, wash-out properties, consistency, ionic release, pH change, and mechanical strength. The addition of mBGn significantly increased the surface area (for both the as-cemented and the hydrated compositions) and also significantly accelerated the setting reaction of CPCs. The injectability and the anti-washout property of CPCs were remarkably enhanced with the addition of mBGn. In striking contrast to the case of pure CPCs, the morphological changes observed in simulated body fluid (SBF) revealed a spherical development of apatite crystals, replicating the nanospherical morphology of the mBGn and consequently resulting in a nano-micro-roughened surface. The mechanical compressive strength substantially increased after SBF immersion and significantly higher values were recorded for mBGn/CPC as compared to pure CPCs. The ion release, including that of calcium, phosphate, and silicon, was recorded at substantial levels during the test period, and the addition of mBGn caused changes in the pH towards less acidic. The in vivo study of the mBGn/CPCs in rat subcutaneous tissue confirmed excellent tissue compatibility with little evidence of inflammatory reactions while exhibiting viable fibroblastic cells with a substantial presence of mature endothelial cells surrounding the cements. When implanted in a rat calvarium defect, a substantial degradation of the samples was noticed in the interfacial region. The proposed mBGn/CPC is a novel, promising cement formulation for the repair and regeneration of bone due to setting characteristics, physico-chemical and mechanical properties, and excellent in vivo tissue compatibility and bioactivity.