Effects of bioactive glass nanoparticles on the mechanical and biological behavior of composite coated scaffolds

Biphasic calcium phosphates (BCP) scaffolds are widely used for bone tissue regeneration. However, brittleness, low mechanical properties and compromised bioactivities are, at present, their major disadvantages. In this study we coated the struts of a BCP scaffold with a nanocomposite layer consisting of bioactive glass nanoparticles (nBG) and polycaprolactone (PCL) (BCP/PCL-nBG) to enhance its mechanical and biological behavior. The effect of various nBG concentrations (1-90 wt.%) on the mechanical properties and in vitro behavior of the scaffolds was comprehensively examined and compared with that for a BCP scaffold coated with PCL and hydroxyapatite nanoparticles (nHA) (BCP/PCL-nHA) and a BCP scaffold coated with only a PCL layer (BCP/PCL). Introduction of 1-90 wt.% nBG resulted in scaffolds with compressive strengths in the range 0.2-1.45 MPa and moduli in the range 19.3-49.4 MPa. This trend was also observed for BCP/PCL-nHA scaffolds, however, nBG induced even better bioactivity and a faster degradation rate. The maximum compressive strength (increased ∼14 times) and modulus (increased ∼3 times) were achieved when 30 wt.% nBG was added, compared with BCP scaffolds. Moreover, BCP/PCL-nBG scaffolds induced the differentiation of primary human bone-derived cells (HOBs), with significant up-regulation of osteogenic gene expression for Runx2, osteopontin and bone sialoprotein, compared with the other groups.