Antibacterial Ti-Cu and Ta-Cu Coatings for Endoprostheses Applied by Magnetron Sputtering onto Ti6Al4V Alloy

Abstract

The paper presents new results of manufacturing coatings by magnetron sputtering to improve the functional properties of joint endoprostheses. The antibacterial properties of Ti-Cu and Ta-Cu coatings deposited by DC multi-magnetron sputtering on Ti6Al4V alloy substrates subjected of gas-abrasive treatment have been investigated. The roughness of the substrate was measured by optical profilometry. The coating hardness and elastic modulus were estimated by nanoindentation methods; the adhesion characteristics were assessed by Rockwell test. Scanning electron microscopy with energy-dispersive X-ray analysis verified the application of coatings with 25 at.% Cu, at thicknesses of 2 μm and 10 μm to roughened Ti6Al4V alloy. All coatings demonstrated sufficient adhesion, whereas Ta-Cu coatings generally revealed higher hardness, while the elastic modulus decreased with increasing coating thickness. Staphylococcus aureus strains were used for in vitro study of the antibacterial properties of Ti-Cu and Ta-Cu coatings. The largest zones of inhibition of bacteria S. aureus 23 mm were observed for 10 µm Ta-Cu coating thickness. The release dynamics of Cu ions from Ta-Cu and Ti-Cu coatings into physiological solution analyzed over seven days via inductively coupled plasma mass spectrometry, matched the inhibition zone growth. The Ti-Cu and Ta-Cu coatings of 2 µm thickness provided weaker antibacterial effect. The optimal parameters of magnetron sputtering of antibacterial Ti-Cu and Ta-Cu coatings on Ti6Al4 alloy substrates were selected. These findings support the potential of these coatings in developing endoprosthesis implants with enhanced antimicrobial and wear-resistant properties