Abstract
► Nanotubes on TiZr alloy with various sized nanotubes produced by two step anodization. ► The TiO2 nanotubes on TiZr have diameters between 20 and 70nm. ► Inhibition of the growth of E. coli bacteria was evaluated. ► Highest antibacterial behavior is observed for nanotubes with diameters of 20–30nm. ► The highest bacteria growth inhibition is for nanotubes with largest active surface.
A two-step anodization of a Ti50Zr alloy results in a various sized nanotube oxide structures, which show an improved antibacterial activity. The nanotubes were formed in glycol with 15vol.% H2O and 0.2M NH4F by two-step anodization. The oxide layer grown during 2h was removed by sonication in deionized water and anodized again for 1h at the same conditions as in the first step. The removed layer acts as a nano-prepatterned surface, where higher ordered and open nanotubes can be achieved. The surface morphologies were analyzed by SEM and AFM, the surface wettability by contact angle measurements. The diameter and the length of the grown nanotubes are potential dependent between 20 and 100nm in diameter and 2.3 and 5.7μm in length, respectively. The antibacterial properties were evaluated in vitro on the formed nanotubes on the TiZr alloy against gram negative Escherichia coli bacteria. The E. coli (ATCC 8738) were cultured in a tube containing Luria Bertani medium at 37°C. The optical density was determined after 18h of incubation. In comparison, the smallest nanotubes exhibited the most efficient antibacterial behavior against E. coli bacterium. This suggests the use of small diameter nanotubes on TiZr for antimicrobial surface applications, which are susceptible for biofilms and microbial cultures.