International Journal of Nanomedicine (May 2019)
Multilayered composite coatings of titanium dioxide nanotubes decorated with zinc oxide and hydroxyapatite nanoparticles: controlled release of Zn and antimicrobial properties against Staphylococcus aureus
Abstract
Urvashi F Gunputh,1,2 Huirong Le,1 Alexandros Besinis,2 Christopher Tredwin,3 Richard D Handy41School of Mechanical Engineering and Built Environment, University of Derby, Derby DE22 3AW, UK; 2School of Engineering, Plymouth University, Plymouth PL4 8AA, UK; 3Peninsula Schools of Medicine and Dentistry, Plymouth University, Plymouth, Devon PL6 8BU, UK; 4School of Biological & Marine Sciences, Plymouth University, Plymouth PL4 8AA, UKPurpose: This study aimed to decorate the surface of TiO2 nanotubes (TiO2 NTs) grown on medical grade Ti-6Al-4V alloy with an antimicrobial layer of nano zinc oxide particles (nZnO) and then determine if the antimicrobial properties were maintained with a final layer of nano-hydroxyapatite (HA) on the composite.Methods: The additions of nZnO were attempted at three different annealing temperatures: 350, 450 and 550 °C. Of these temperatures, 350°C provided the most uniform and nanoporous coating and was selected for antimicrobial testing.Results: The LIVE/DEAD assay showed that ZnCl2 and nZnO alone were >90% biocidal to the attached bacteria, and nZnO as a coating on the nanotubes resulted in around 70% biocidal activity. The lactate production assay agreed with the LIVE/DEAD assay. The concentrations of lactate produced by the attached bacteria on the surface of nZnO-coated TiO2 NTs and ZnO/HA-coated TiO2 NTs were 0.13±0.03 mM and 0.37±0.1 mM, respectively, which was significantly lower than that produced by the bacteria on TiO2 NTs alone, 1.09±0.30 mM (Kruskal–Wallis, P<0.05, n=6). These biochemical measurements were correlated with electron micrographs of cell morphology and cell coverage on the coatings.Conclusion: nZnO on TiO2 NTs was a stable and antimicrobial coating, and most of the biocidal properties remained in the presence of nano-HA on the coating.Keywords: zinc oxide nanoparticles, TiO2 nanotubes, hydroxyapatite, antimicrobial, Staphylococcus aureus
