Immobilization of cobalt-loaded laponite/carboxymethyl chitosan on polycaprolactone nanofiber for improving osteogenesis and angiogenesis activities

Designing scaffolds with therapeutic potential to stimulate angiogenesis and osteogenesis is considered a promising strategy in the regeneration of large skeletal defects. In this study, the cobalt ions (Co2+) were incorporated in laponite (LAP) nanodiscs (0.65, 1.3, and 2.6 g/L) and, in combination with carboxymethyl chitosan (CMC), were immobilized on the electrospun polycaprolactone (PCL) nanofiber to fabricate scaffolds for simultaneous enhancing osteogenesis and angiogenesis inductions to human bone marrow mesenchymal stem cells. The Fourier transform infrared, energy dispersive X-ray, and inductively coupled plasma atomic emission spectrometries confirmed the Co2+-loading on the LAP nanodiscs and the chemical immobilization on the surface of PCL nanofibers. The result of MTT assay, scanning electron microscopy, and fluorescence staining displayed that Co2+-loaded scaffolds were biocompatible. Furthermore, the incorporation of Co2+ ions into LAP nanodiscs had significant effects on the calcium deposition and expression of osteogenic markers, alkaline phosphatase and osteonectin, as well as, the expression of angiogenic markers, hypoxia-inducible factor-1 alpha and vascular endothelial growth factor of the cells seeded on the scaffolds (p <= 0.05). These results suggested that the combination of Co2+ ions with CMC/LAP could result in a synergetic effect on the osteogenesis and angiogenesis stimulations.