Plasma sprayed alumina–nanosilver antibacterial coatings

Abstract

Alumina coatings have wide-ranging applications by virtue of their inherent wear and corrosion resistance and attractive dielectric and diffusion barrier properties. In many cases, they do not meet the antibacterial demand to eliminate microbiologically-induced corrosion and diseases. The aim of this work is to prepare plasma sprayed alumina–nanosilver (Al₂O₃/Ag) coatings and investigate their antibacterial properties with various compositions. Moreover, Al₂O₃/Ag coatings are optimized to use minimum amounts of silver nanoparticles (AgNPs) and exhibit excellent antibacterial properties. Al₂O₃ coatings with five different amounts of AgNPs were deposited on titanium alloys substrates by plasma spray. The Al₂O₃/Ag coatings, which were denoted as A1, A2, A3, A4 and A5, were prepared by using α-Al₂O₃ powders containing 1 ppm, 10 ppm, 100 ppm, 1000 ppm and 10 000 ppm AgNPs, respectively. The composition and morphology of Al₂O₃/Ag coatings were investigated by X-ray diffraction and scanning electron microscopy. The antibacterial activity of Al₂O₃/Ag coatings was tested using Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as model strains of Gram negative and Gram positive bacteria, respectively. The bacterial adhesion was also examined by employing both of the bacteria to observe bacterial adhesion status and evaluate antibacterial property of as-prepared coatings. The results showed the Al₂O₃/Ag coatings with more than 10 ppm AgNPs exhibited strong antibacterial property against E. coli and S. aureus. Bacterial adhesion assays showed that A2–A5 had anti-adhesive property of E. coli and S. aureus, which was in accordance with the antibacterial results. Moreover, the main factors influencing the antibacterial properties of Al₂O₃/Ag coatings were discussed with silver nanoparticles and hydrophobicity of the coatings.