Bacterial adhesion and inactivation on Ag decorated TiO2-nanotubes under visible light: Effect of the nanotubes geometry on the photocatalytic activity

Abstract

This study investigates the effect of the diameter of TiO nanotubes and silver decorated nanotubes on optical properties and photocatalytic inactivation of Escherichia coli under visible light. The TiO nanotubes (TiO-NTs) were prepared using the electrochemical method varying the anodization potential starting from 20 V until 70 V. The Ag nanoparticles were carried out using the photoreduction process under the same experimental conditions. The diameter size was determined using the scanning electronic microscopy (SEM). TiO-NTs diameter reached ∼100 nm at 70 V. Transmission electronic microscopy (TEM) imaging confirmed the TiO-NTs surface decoration by silver nanoparticles. The Ag-NPs average size was found to be equal to 8 nm. The X-Ray diffraction (XRD) analysis confirm that all TiO-NTs crystallize in the anatase phases regardless the used anodization potential. The decrease of the photoluminescence (PL) intensity of Ag NPs decorated TiO-NTs indicates the decrease of the specific area when the nanotubes diameter increases. The UV-vis absorbance show that the absorption edges was bleu shifted with the increasing of nanotubes diameter, which can be explained by the increase of the crystallites average size. The bacterial adhesion and inactivation tests were carried in the dark and under light. Bacteria were seen to adhere on TiO-NTs in the dark; however, under light the bacteria were killed before they establish a strong contact with the TiO-NTs and Ag/TiO-NTs surfaces. Bacterial inactivation kinetics were faster when the anodizing potential of the NTs-preparation increases. A total bacterial inactivation was obtained on ∼100 nm nanotubes diameter within 90 min. This result was attributed to the enhancement of the TNTs crystallinity leading to reduced surface defects. Redox catalysis was seen to occur under light on the TiO-NTs and Ag/TiO-NTs. the photo-induced antibacterial activity on the AgO/AgO decorated TiO-NTs was attributed to the interfacial charge transfer mechanism (IFCT).

Electrophoretic Deposition and Characteristics of Chitosan–Nanosilver Composite Coatings on a Nanotubular TiO2 Layer

“…Bacterial inactivation may occur via two different actions: at the direct contact of bacteria with nanosilver at the interface or by the interaction of bacteria and the silver ions that appear during the dissolution of nanosilver [57][58][59]. The present results did not support either hypothesis, but the direct contact of silver ions and bacteria in solution seems more probable, as the antibacterial efficiency followed the silver release.…”

“…Moreover, the reference dose for allowable oral exposure of Ag, as defined by the US EPA (United States Environmental Protection Agency) is 0.005 mg of Ag/kg of body mass per day and, considering the maximum Ag release rate determined here, the maximum daily allowable consumption of Ag will not be exceeded in an average adult [56]. Bacterial inactivation may occur via two different actions: at the direct contact of bacteria with nanosilver at the interface or by the interaction of bacteria and the silver ions that appear during the dissolution of nanosilver [57][58][59]. The present results did not support either hypothesis, but the direct contact of silver ions and bacteria in solution seems more probable, as the antibacterial efficiency followed the silver release.…”

Improved Cell Adhesion and Osseointegration on Anodic Oxidation Modified Titanium Implant Surface

“…In biomedical field, anodic oxidation method was employed to produce TiO 2 nanotube coatings on metallic implants 7,12) . Although several researchers reported the work of anodic oxidation induced nanopatterns on Ti surface, however their research objectives were either the improvement of photocatalytic effect, or the development of drug delivery system 13,14) . The direct influence of the nanotube-structured surface induced by anodic oxidation on biological properties, especially its effect on cell adhesion of Ti based implants is not well described.…”

Visible-Light Active Titanium Dioxide Nanomaterials with Bactericidal Properties

“…Rtimi and coworkers prepared TNTs of different diameters by varying applied voltages from 20 V-70 V during anodizing process. The anodized TNTs were air-dried, annealed for 3 h at 400 • C, and then immersed in a 0.1 M AgNO 3 ; Ag + ions were reduced to AgNPs on TNTs using the photoreduction method [260]. A low voltage of 20 V was not favorable for the formation of TNTs.…”

“…(b) Bacterial inactivation mechanism of Ag/TNTs, as described by Reaction(1)(2)(3)(4)(5)(6). Reproduced with permission from[260]. Copyright Elsevier, 2018.…”