Reactive polyurethane carbon nanotube foams and their interactions with osteoblasts.

The remarkable intrinsic properties of carbon nanotubes, including their high mechanical strength, electrical conductivity, and nanoscale 3D architecture, create promising opportunities for the use of nanotube composites in a number of fields, particularly for composites in which conventional fillers cannot be accommodated. In the current study, 3D polyurethane (PU) nanocomposite foams were developed, and their potential biomedical applications were investigated. Multiwalled carbon nanotubes (CNTs) were synthesized by chemical vapor deposition and, following suitable chemical modification, uniformly distributed within the walls of PU foams produced by direct reaction. Although the loading fraction was too low to observe significant mechanical effects, CNT incorporation improved the wettability of the nanocomposite surfaces in a concentration-dependent manner, supporting the claim that the nanotubes are active at the pore surface. Studies of bone cell interactions with the nanocomposite foams revealed that increasing CNT loading fraction did not cause osteoblast cytotoxicity nor have any detrimental effects on osteoblast differentiation or mineralization. The application of "fixed" or embedded CNTs in nondegradable scaffolds is likely advantageous over "loose" or unattached CNTs from a toxicological point of view.