Nanotube Size Alters Corrosion Behavior, Mechanical Properties, and Biological Interactions of Anodized Ti6Al7Nb

The fabrication of oxide-based nanotubes on implant surfaces has garnered significant attention in orthopedics due to their enhanced surface area and nanostructured roughness, which promote integration with bone tissue. However, studies investigating the effects of varying pore diameters while maintaining constant oxide layer thickness remain limited, despite the potential of pore size to influence mechanical performance, cellular responses, and the long-term success of implants. In this study, we fabricated nanotube structures with fixed lengthsshort (∼1 μm, S) and long (∼4 μm, L)but with varying pore sizes, to gain a deeper understanding of how nanotube dimensions and nanostructured topography influence corrosion behavior, mechanical properties, and in vitro cellular interactions. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses confirmed that a uniform nanostructure with a roughened surface was successfully achieved through anodization. Corrosion experiments revealed that the short nanotubes formed at 10 V (NT10-S) exhibited reduced corrosion, approximately 40% and 49% lower than that of the long nanotubes formed at 10 V (NT10-L) and nonanodized (NA) control, respectively. Moreover, the NT10-S samples exhibited the highest critical load, measured as 0.16 ± 0.02 N in the microscratch test. Notably, osteoblast proliferation was enhanced by 47% on NT10-S samples after 5 days of culture compared to NA surfaces. This study provides valuable insights into how nanotube length, pore diameter, and surface nanostructured topography anodized surfaces influence both chemical and biological responses, offering critical guidance for the design of next-generation orthopedic implants.