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Multilayered composite coatings of titanium dioxide nanotubes decorated with zinc oxide and hydroxyapatite nanoparticles: controlled release of Zn and antimicrobial properties against Staphylococcus aureus

Authors Gunputh UF, Le H, Besinis A, Tredwin C, Handy RD

Received 22 December 2018

Accepted for publication 21 March 2019

Published 16 May 2019 Volume 2019:14 Pages 3583—3600


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 5

Editor who approved publication: Prof. Dr. Thomas J. Webster

Urvashi F Gunputh,1,2 Huirong Le,1 Alexandros Besinis,2 Christopher Tredwin,3 Richard D Handy4

1School 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, UK

Purpose: 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

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