Carbon Nanotubes Induce Bone Calcification by Bidirectional Interaction with Osteoblasts

Multi-walled carbon nanotubes (MWCNTs) promote calcification during hydroxyapatite (HA) formation by osteoblasts. Primary cultured osteoblasts are incubated with MWCNTs or carbon black. After culture for 3 weeks, the degree of calcification is very high in the 50 μg mL⁻¹ MWCNT group. Transmission electron microscopy shows needle-like crystals around the MWCNTs, and diffraction patterns reveal that the peak of the crystals almost coincides with the known peak of HA.