Comparative Studies of Carbon Nanotubes: Implications for Alkaline Phosphatase Activity and Mineralized Matrix in Osteoblasts Cultures

Carbon nanotubes (CNT) are cylindrical nanostructures that could be used to mimic collagen fibers in titanium (Ti) coatings in order to improve the osteointegration of implants in bone tissue. The literature documents that differences in the shape of carbon nanotubes can influence osteoblasts viability, alkaline phosphatase activity (ALP), and bone nodule formation. We developed four sets of CNT samples using chemical vapor deposition on NaCI as substrate to enable CNT growth, followed by HCI purification to avoid oxygen functional groups formation or wall damage. The results were multi walled CNT with different diameter distributions and shapes. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and thermogravimetric (TG) analysis were used to characterization of the samples. Cell viability, ALP activity and matrix mineralization were determined in osteoblasts cultures stimulated with CNT dispersed on plastic or on Ti (Ti-CNT). Ti-CNT improved cell viability, but this effect varied with nanotube shape and on the osteoblast growth phase. CNT addition at day 14 of osteoblast culture produced a better cellular response compared to the other days. Highly disordered multi-walled CNT and coiled CNT resulted in higher cell viability and ALP.