Antibacterial investigation of titanium-copper alloys using luminescent Staphylococcus epidermidis in a direct contact test

Abstract

Commercially pure titanium (CP-Ti), used as oral implants, is often populated by various bacterial colonies in the oral cavity. These bacteria can cause Peri-implantitis, leading to loss of bone tissue and failure of implants. With the increased awareness of antibiotic resistance, research has been directed towards alternative solutions and recent findings have indicated titanium‑copper (Ti-Cu) alloys as a promising antibacterial material. The aim of this study was to produce homogeneous Ti-Cu alloys, with various concentrations of copper, and to characterise their antibacterial properties through direct contact tests, using luminescent bacteria, in addition to traditional materials characterisation techniques. Samples of CP-Ti and four different Ti-Cu alloys (1, 2.5, 3 and 10 wt%Cu) were produced in an arc-furnace, heated treated and rapidly quenched. X-ray diffraction revealed that Ti₂Cu, was present only in the 10 wt%Cu alloy, however, scanning electron microscopy (SEM) indicated precipitates at the grain boundaries of the 3 wt%Cu alloy, which were confirmed to be of a copper rich phase by energy dispersive x-ray spectroscopy (EDS) analysis. EDS line scans confirmed that the alloys were homogenous. After 6 h, a trend between copper content and antibacterial rate could be observed, with the 10 wt%Cu alloy having the highest rate. SEM confirmed fewer bacteria on the 3 wt%Cu and especially the 10 wt%Cu samples. Although the 10 wt%Cu alloy gave the best antibacterial results, it is desired that the Cu concentration is below ~3 wt%Cu to maintain similar mechanical and corrosive performance as CP-Ti. Therefore, it is proposed that future work focuses on the 3 wt%Cu alloy.

Keywords: Antibacterial; Copper; S. epidermidis; Ti(2)Cu; Titanium.