Biocompatibility of Carbon Nanotubes for Cartilage Tissue Engineering

Carbon nanotubes (CNT) have the potential to become an important component of scaffolding in tissue engineering, due to their unique physical properties. However, one major limitation of CNTs that must be overcome is their inherent cytotoxicity. In this study, we assessed the long-term biocompatibility of CNTs for chondrocyte growth. The effect of CNTs on chondrocyte viability and biochemical deposition has been examined in two dimensional (2D) cultures, and in three dimensional (3D) composite materials consisting of hydrogels and CNTs. The exposure of chondrocytes to CNTs was carried out up to 14 days in 2D culture and 21 days in 3D agarose composites. Our results suggest that functionalized CNTs alter the viability and metabolic response of cells over the 2 to 3 week duration. Interestingly, the results of this study also suggest the dose dependent effect of CNTs on cellular responses vary between 2D and 3D cultures, suggesting that chondrocytes tolerate the presence of CNTs at greater concentrations in 3D more than in 2D cultures. In addition, CNTs appear to have a stimulatory metabolic effect on chondrocytes in 3D cultures, reflected by enhanced production of glycosaminoglycans (GAGs) and collagen deposition. These findings support the notion that optimization of the use of nanotubes in cell-based therapies should be performed in 3D systems directly, and that CNTs appear to promote cellular growth and metabolic activity of chondrocytes.