New Evidence for Ag-Sputtered Materials Inactivating Bacteria by Surface Contact without the Release of Ag Ions: End of a Long Controversy?

Abstract

The study provides new evidence for Ag-coated polyester (PES) mediating Escherichia coli inactivation by way of genetically engineered E. coli (without porins, from now denoted porinless bacteria). This allows the quantification of the bactericidal kinetics induced by the Ag surface without the intervention of Ag ions. Bacterial inactivation mediated by Ag-PES was seen to be completed within 60 min. The samples were prepared by high-power impulse magnetron sputtering (HiPIMS) at different sputter powers. In anaerobic media, this process required 120 min. The amounts of ions (Ar + , Ag + , and Ag 2+ ) generated during the deposition by direct current magnetron sputtering (DCMS) and HiPIMS were determined by mass spectrometry. The thickness of the Ag films sputtered on PES by DCMS (0.28 A) during 100 s was found to be 340 nm. Thicknesses of 250, 230, and 200 nm were found when sputtering with HiPIMS was tuned at 8, 17, and 30 A, respectively. By scanning transmission electron microscopy (STEM-HAADF), the atomic distribution of Ag and oxygen was detected. By X-ray photoelectron spectroscopy (XPS), a shift in the Ag oxidation state was observed within the bacterial inactivation period. This reveals redox catalysis within the time required for the total bacterial inactivation due to the interaction between the bacterial suspension and Ag-PES. Surface properties of the Ag-coated PES samples were additionally investigated by X-ray diffraction (XRD). The formation of Ag plasmon was detected by diffuse reflectance spectroscopy (DRS) and was a function of the applied sputtering energy. The indoor sunlight irradiation dose required to induce an accelerated bacterial inactivation was found to be 5−10 mW/cm 2 .

Triple-Function Au–Ag-Stuffed Nanopancakes for SERS Detection, Discrimination, and Inactivation of Multiple Bacteria

“…A number of bacterial colonies showed un-conspicuous reduction when bacteria were treated by K 3 [Fe­(CN) 6 ] with different concentrations (1.0–1.6 mM) (Figure S7), indicating good biocompatibility and weak antibacterial activity of the etchant. Considering the broad-spectrum antibacterial activity of Ag + , we studied if there was any difference in antibacterial activity of AAS-NPs produced by addition of different etchant concentrations. When [Fe­(CN) 6 ] 3– concentration was higher than 1.4 mM, the produced AAS-NPs killed >99.99% of all three bacteria, including S.…”

Characterization and Antibacterial Properties of Polyetherketoneketone Coated with a Silver Nanoparticle-in-Epoxy Lining

“…The antibacterial mechanism of AgNPs has been widely studied [ 35 , 36 , 37 ]. According to the deconvoluted Ag 3d spectrum results, the synthesized AgNPs were primarily present in a metallic state ( Figure 2 D).…”

“…Ag + ions, which are converted from AgNPs in the physiological environment, deform cell membranes and interact with some proteins [ 1 ]. Rtimi et al [ 37 ] proposed a new perspective. They concluded that the interaction between Ag-sputtered materials and bacteria, through direct surface contact-induced redox reaction, resulted in an increase in the permeability of the bacterial cell envelope and the modification of the interfacial bacterial potential.…”

Update on Interfacial Charge Transfer (IFTC) Processes on Films Inactivating Viruses/Bacteria under Visible Light: Mechanistic Considerations and Critical Issues

“…Ag reacts almost instantaneously with air (O 2 ) and atmospheric water vapor, leading to AgOH. Only 2-3 atomic layers of AgOH (0.4-0.6 nm thick) are found on NPs' surfaces [31] The Langmuir-Hinshelwood (L-H) kinetic model is frequently employed to describe bacterial inactivation kinetics [6,7]. This model is applied to process the data obtained during virus inactivation mediated by TiO 2 and metal-TiO 2 photocatalysts [5][6][7][8].…”

“…Ag reacts almost instantaneously with air (O 2 ) and atmospheric water vapor, leading to AgOH. Only 2-3 atomic layers of AgOH (0.4-0.6 nm thick) are found on NPs' surfaces[31]. AgOH decomposes spontaneously to Ag 2 O.…”