Nano-hydroxyapatite/poly(L-lactic acid) nanofibrous composite scaffolds prepared by in-situ precipitation combined with frozen extraction

Abstract

A series of nano-hydroxyapatite/polyl-lactic acid (n-HA/PLLA) three-dimensional nanofibrous composite scaffolds were synthesized by a new in-situ precipitation method combined with the frozen extraction using Ca(NO3)2·4H2O and (NH4)2HPO4 as the hydroxyapatite precursor. Combining SEM and XRD results showed that the HA nanoparticles were generated on the surface of the scaffolds and uniformly distributed throughout the material. The effects of the aging temperature and the amount of calcium phosphate solution on the morphology of resulting nanofiber composite scaffolds and fiber diameters were investigated. The results showed that uniform nanofibers were formed at low aging temperatures (−10 °C or less), while the fibers tended to flake and the support structure was more compact at high aging temperatures (5 °C or higher). The amount of added (NH4)2HPO4 had a similar effect on the nanofiber structure. The volume of the (NH4)2HPO4 solution and aging temperature used to prepare the composites also influenced the porosity, crystallinity, and mechanical properties of the final materials. In vitro bioactivity assays using simulated body fluid (SBF) showed that large amounts of low crystallinity carbonate hydroxyapatite (CHA) formed on the scaffolds after 14 days, indicating that the n-HA/PLLA nanofiber composite scaffolds have good bioactivity. This study shows that nHA effectively improved the biological activity of composite scaffolds.