Carbon nanotube-enhanced polyurethane scaffolds fabricated by thermally induced phase separation

Nanocomposite foams are an attractive prospect in a number of fields including biomedical science, catalysis and filtration. In biomedical engineering, porous nanocomposite scaffolds can potentially mimic aspects of the nanoscale architecture of the extra-cellular matrix, as well as enhance the mechanical properties required for successful weight-bearing implants. Thermoplastic polyurethane - multi-walled carbon nanotubes (CNTs) foams were manufactured by thermally induced phase separation ( TIPS). TIPS proved to be a successful manufacturing route to three-dimensional, highly porous polymers containing well-dispersed CNTs. Some CNTs are trapped perpendicular to the pore surface creating a rough, nanotextured surface. The surface character of the nanocomposites became more acidic with increasing loading fraction of oxidised CNTs. However, due to the heterogeneity of the nanocomposite surface, its wetting behaviour was not affected. CNT incorporation significantly improved the compression strength and stiffness of the nanocomposite scaffold. The biological properties of these scaffolds were studied in vitro and revealed that increasing MWNT loading fraction did not cause osteoblast cytotoxicity or detrimental effects on osteoblast differentiation or mineralisation. However, osteoblast production of the potent angiogenic factor VEGF ( vascular endothelial growth factor) increased in proportion to CNT loading ( after 3 days in culture), revealing the potential of the nanocomposite scaffolds to influence cellular behaviour.