Highly Bioactive 8 nm Hydrothermal TiO2 Nanotubes Elicit Enhanced Bone Cell Response

The TiO2 passivation layer on the Ti surface has positive bone‐interface qualities including bioactivity and chemical composition that aids in the integration of orthopedic implants, known as osseointegration. New research designs have focused on the topographic structure of the TiO2 oxide layer with a large surface area for optimizing osseointegration properties for improved implant performance. We have utilized a hydrothermal process to further refine the TiO2 structure to an 8 nm diameter nanotube geometry and evaluated its effect on bone cell growth. Interestingly these small diameter TiO2 nanotubes, unlike the anodized TiO2 nanotubes, exhibit mostly multiwalled nanotube configuration with about 2–6 parallel walls along the length of the elongated nanotubes. It has been found that these multiwall nanotubes significantly enhance osteoblast cell response compared to unmodified, control Ti. The nanotube structure provided significantly up‐regulated bone forming ability with ≈ 2–3 fold increased alkaline phosphatase (ALP) activity levels, and induced the formation of abundant amounts of bone matrix deposition predominantly consisting of calcium and phosphorous. Biomedical implications of such bone cell and nanotube interface behavior on bone formation and bone bonding of titanium implants are discussed. Although there is a broad scope as regard to application, Ti orthopedic implants are just one class of medical devices that could benefit from a modified, nanostructured oxide surface. We have utilized a hydrothermal process to refine the TiO2 structure to an 8nm diameter nanotube geometry and evaluated its effect on bone cell growth. Although many properties and functions of the hydrothermally processed nanotubes have been evaluated, this is the first study to our knowledge on the biological responses to such ultrafine Ti oxide nanotube surfaces.