In vitro and in vivo characterization of multi-walled carbon nanotubes/polycaprolactone composite scaffolds for bone tissue engineering applications

For bone regeneration, scaffolds are typically made of degradable and biocompatible materials that provide mechanical support and promote bone formation during the repair and regeneration of damaged bone. Herein, we fabricated multi-walled carbon nanotubes (MWNTs)/polycaprolactone (PCL) composite scaffolds using the solution evaporation technique and characterized their properties in vitro as well as in vivo. The results showed that the added MWNTs were homogeneously distributed throughout the MWNTs/PCL scaffolds. The thermogravimetric analysis (TGA) and in vitro degradation experiments indicated the addition of MWNTs (0.25-2.0 wt%) improved the mechanical and thermal properties of the composite scaffolds, while the PCL grafts still preserved advanced biodegradability. The biomimetic mineralization of the hydroxyapatite (HA) formed on the surface of specimens suggesting that the MWNTs/PCL composite scaffolds had good in vivo bone bioactivity. The scanning electron microscopy images and 3-(4,5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide (MTT) assay results showed that the MWNTs/PCL scaffolds improved the adhesion and proliferation of rat bone-marrow-derived stromal cells (BMSCs) and the scaffolds were supposed to promote osteogenesis. In addition, the in vivo study indicated the MWNTs/PCL scaffolds with 0.5 wt% MWNTs promoted new bone formation with greater bone density and bone regeneration efficacy. Therefore, the MWNTs/PCL scaffolds, with advanced mechanical, biodegradable and biological properties, are suitable candidates for bone tissue engineering applications.