**5. Conclusions**

The results of our works proved that amorphous titania nanotube coatings, used to modify the surface of medical devices made of titanium alloys, requires the removing of water remains on/inside nanotubular surface before autoclaving procedure—if we want, of course, the nanotube architecture remains on the surface. Additional drying affects the TiO2 tubes surface stabilization, making them resistant to the effects of hot water vapors under higher pressure, which are present during the sterilization process made by autoclaving. Otherwise, nanotubular coatings containing traces of water on the surface or inside the nanotubes during autoclaving can be subjected to the destruction of their tubular architecture and to promoting of amorphous TiO2 tubes phase transformation into polymorphic nanocrystals or crystalline powders. Such coatings revealed different mechanical and biointegration properties compared to nanotubular ones.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2077-0383/8/2/272/s1, Figure S1: IR DRIFT spectra of TNH20-TNH60; Figure S2: The values of contact angles for water (a) and diiodomethane (b), and surface free energy (c) of Ti6Al4V/TNT20-60 and Ti6Al4V/TNH20-60 samples; Table S1: Diameters and wall thickness of titania nanotubes produced on the surface of Ti6Al4V substrates in the potential range of 5–60V; Table S2: Contact angles values for Ti6Al4V/TNT20-60 and Ti6Al4V/TNH20-60, measured for water and diiodomethane, and surface free energy values obtained according to Owens-Wendt method; Table S3: Surface roughness parameters (Sa) of Ti6Al4V, Ti6Al4V/TNT20-60 and Ti6Al4V/TNH20-60 systems, as determined based on the AFM image analysis.

**Author Contributions:** Conceptualization, A.R.; methodology, A.R.; formal analysis, A.R., T.J., M.B; investigation, A.R., M.E., T.J., M.B.; writing—original draft preparation, A.R.; writing—review and editing, A.R.; visualization, A.R.; supervision, A.R.

**Funding:** This research was funded by the Regional Operational Programme of the Kuyavian-Pomeranian Voivodeship (1.3.1. Support for research and development processes in academic enterprises), within the gran<sup>t</sup> obtained by Nano-implant Ltd. The APC was funded by Nano-implant Ltd.

**Acknowledgments:** A.R. and M.B. would like to thank Piotr Piszczek and Andrzej Zieli ´nski for valuable conversations enriching the discussion presented in the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.
