Injectable scaffolds for bone regeneration.

Clinical treatments of significant bone defects involve invasive procedures such as the application of auto- and allografts. These procedures present many limitations including the potential for infection and rejection. There is therefore a need to develop novel therapeutic strategies able to exploit the natural regenerative potential of bone and that can be delivered in a less invasive manner. Among the materials studied for the development of novel scaffolds, stimuli-responsive gels containing hydroxyapatite and carbon nanotubes as nanofillers have generated great interest. In the present work, chitosan gels containing chitosan grafted CNTs and chitosan-hydroxyapatite complex have been formed by cross-linking with glycerol phosphate. The addition of the nanofillers afforded hydrogels with a faster sol/gel transition at 37 °C and enhanced mechanical properties. The thermosensitive composite gels also showed a good bioactivity profile associated with potential for the prolonged delivery of protein drugs. The inclusion of chemically cross-linked CNTs and HA in thermosensitive gels afforded injectable composite materials with enhanced properties, including reduction of gelation time, improved mechanical properties, good bioactivity, and prolonged drug release.