![]() ![]() Every sample was placed into a glass Petri dish, then inoculated with bacteria. coli K12) bacterium was obtained from the Deutsche Sammlung von Mikro-organismen und Zellkulturen GmbH (DSMZ), Braunschweig, Germany. The different deposition times varied between 25 and 60 min to obtain films with different thicknesses (0.85–2.2 µm).Įscherichia coli ( E. All of the films were deposited with a constant flow rate of argon of 100 sccm and with a varying oxygen rate injected inside the chamber between 2 and 10 sccm. After initial optimization, the thin films were deposited under a mixed atmosphere of Ar and O 2. The used bias voltage, Cu discharge current, Ar flow rate and sputtering chamber pressure were kept constant at 200 W, 1 A, 100 sccm and 0.37 Pa, respectively. The substrates and Cu-target were cleaned for 15 min using Ar ions to remove the surface contaminants. Before deposition, the stainless-steel samples were cleaned by ultrasound path with acetone during 10 min, and then with ethanol for 8 min to remove all of the dirtiness caused by the handling. The distance between the copper target and the sample was fixed at 14 cm. The chamber was evacuated to reach a pressure of 8 × 10 −4 Pa. Ī pure Cu circular target (99.99% purity, 200 mm × 6 mm) was used. Moreover, once copper ions enter a cell, they can generate reactive oxygen species (ROS), produce phosphate hydrolysis and/or intercalate between base pairs, leading them to break off the hydrogen bonds responsible for DNA double-stranded conformation. The functions of many enzymes inside bacterial cells are therefore inhibited by the ability of Cu ions to substitute essential ions such as Na, K, Zn, and Mg. Cuprous atoms strongly bind to thiol groups (–SH) mainly made of cysteine-forming steady S\Cu bonds with thiol-containing compounds with a high stability constant, reaching 10 10 M −1. The antibacterial activity of copper oxides was reported to happen through (i) photo-generated reactive oxygen species (ROS) at the interface of the Cu semiconductors under appropriate light irradiation and (ii) ion diffusion to the intracellular compartment, leading to a metabolic disorder and cell death. Copper oxide with concentrations in the ppm/ppb ranges was reported to induce the pathogens’ cytotoxicity, leading to their death. The atomic structure of copper consists of filled electronic orbitals hopping around the positively charged nucleus. Copper oxides have been used for decades as antimicrobial agents. Cu ions are well known for their widespread antibacterial activities. Recently, during the SARS-CoV-19 pandemic, many scientists stressed the antimicrobial uses of copper and copper oxides for hospital setting disinfection. The use of genetically modified bacteria (without porins) allowed the rationalization of the predominant effect of the extracellular bacterial inactivation compared to that of intracellular bacterial inactivation through ion release and diffusion. ![]() The crystallographic structure of the sputtered thin films was investigated using X-ray diffraction (XRD), showing the cubic Cu peaks and characteristic peaks of Cu 2O. The oxygen content of the sputtered films varied from 7.8 to 25%, justifying the semi-conductor behavior of the thin films under indoor light. The chemical composition of the deposited Cu thin films was carried out by Energy Dispersive X-ray Spectroscopy (EDX) and showed a uniform distribution of copper and oxygen, revealing the formation of copper oxides (Cu xO). Scanning electron microscopy (SEM) showed homogeneous coating growths of copper with a columnar texture. Stereomicroscopy imaging showed live/dead bacterial cells on the coated substrates. Bacterial inactivation was monitored under indoor light. We showed that the surface roughness profile influenced bacterial adhesion in the dark. The thin copper films’ composition and antibacterial activities were first optimized by being deposited on an Si wafer. ![]() The pretreated substrates were coated with thin copper films using magnetron sputtering. Sandblasting, mirror polishing and Surface Mechanical Attrition Treatment (SMAT) at high or low energies have been employed to modify the substrate’s (316L stainless steel) roughness. In this manuscript, we studied the effect of additive manufacturing pretreatment on bacterial adhesion and inactivation on copper-based interfaces. ![]()
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