Effect of CNT on collagen fiber structure, stiffness assembly kinetics and stem cell differentiation.

Collagen is a native one-dimensional nanomaterial. Carbon nanotube (CNT) was found to interface with biological materials and show promising applications in creating reinforced scaffolds for tissue engineering and regenerative medicine. In this study, we examined the unique role of CNT in collagen fiber structure, mechanical strength and assembly kinetics. The results imply that CNT interacts with collagen at the molecular level. It relaxes the helical coil of collagen fibrils and has the effect of flattening the fibers leading to the elongation of D-period, the characteristic banding feature of collagen fibers. The surface charge of oxidized CNT leads to enhanced local ionic strength during collagen fibrillogenesis, accounting for the slower kinetics of collagen-CNT (COL-CNT) fiber assembly and the formation of thicker fibers. Due to the rigidity of CNT, the addition of CNT increases the fiber stiffness significantly. When applied as a matrix for human decidua parietalis placental stem cells (hdpPSCs) differentiation, COL-CNT was found to support fast and efficient neural differentiation ascribed to the elongated D-period. These results highlight the superiority of CNT to modulate collagen fiber assembly at the molecular level. The study also exemplifies the use of CNT to enhance the functionality of collagen for biological and biomedical applications.