Influence of the EPD route and surface preparation of titanium substrates on the microstructure, surface topography and usage properties of chitosan coatings incorporated in Tea Tree Oil and Terpinen-4-ol

The electrophoretic deposition (EPD) of Tea Tree Oil (TTO)/chitosan and Terpinen-4-ol/chitosan coatings on titanium substrates with different surface preparations was examined. The deposition was performed with vertical and horizontal configurations of electrodes, called horizontal and vertical EPD, respectively, following the direction of the electric field. The data obtained showed the influence of both the electrode configuration and substrate surface preparation on the EPD process as well as coating properties, such as adhesion, morphology, microstructure, roughness, surface topography and wettability. The most promising coatings were obtained for vertical EPD and ground titanium substrates. They were relatively homogeneous and consisted of droplets of TTO or Terpinen-4-ol embedded in chitosan. The formation of hydrogen bonds between chitosan chains and Terpinen4-ol was detected and the responsible mechanism was indicated. The coatings exhibited high adhesion strength, relatively low wettability as well as medium roughness. Both coatings improved the corrosion resistance of the titanium in Hanks' solution. This work showed that natural chitosan-based coatings incorporated in TTO and Terpinen-4-ol are promising for the antimicrobial protection of titanium. Terpinen-4-ol/chitosan surfaces has shown favorable antibacterial properties, but it is interesting that it can be combined with chitosan to further increase this potential, besides, they had the highest biocompatibility.