Adhesion and inactivation of Gram-negative and Gram-positive bacteria on photoreactive TiO2/polymer and Ag–TiO2/polymer nanohybrid films

Abstract

The aim of this study was to develop photoreactive surface coatings, possessing antibacterial proper ties and can be activated under visible light illumination (%max=405nm) using LED-light source. The photocatalytically active titanium dioxide (TiO2) was functionalized with silver nanoparticles (Ag NPs) and immobilized in polyacrylate based nanohybrid thin film in order to facilitate visible light activity (-^Ag/TiO2,maX = 500 nm). First, the photocatalytic activity was modelled by following ethanol vapor degra dation. The plasmonic functionalization resulted in 15% enhancement of the activity compared to pure TiO2. The photoreactive antimicrobial (5log reduction of cfu in 2h) surface coatings are able to inac tivate clinically relevant pathogen strains (methicillin resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa) within short time (60-120 min) due to the formed and quantified reactive oxy gen species (ROS). The existence of electrostatic interactions between the negatively charged bacteria (from-0.89 to-3.19 ^eq/109 cfu) and positively charged photocatalyst particles (in the range of +0.38 and +12.3meq/100g) was also proven by charge titration measurements. The surface inactivation of the bacteria and the photocatalytic degradation of the cell wall component were also confirmed by fluo rescence and transmission electron microscopic observations, respectively. According to the results an effective sterilizing system and prevention strategy can be developed and carried out against dangerous microorganisms in health care.

Influencia de las nanopartículas de Ag sobre las propiedades mecánicas y tribológicas y en el efecto citotóxico y bactericida de los recubrimientos de TaN(Ag)

“…Un ejemplo de ello es el estudio de la implantación de iones de plata en aceros inoxidables y matrices cerámicas, para la reducción de la adherencia bacteriana y posterior formación de biofilm de cepas como E. coli y S. aureos en dispositivos biomédicos y de P. aeruginosa en instrumentación quirúrgica (Echeverrigaray et al, 2016;Tallósy et al, 2016). Para garantizar un elevado efecto bactericida y una apropiada biocompatibilidad en el material compuesto, debe mantenerse el equilibrio entre la cantidad, distribución y forma de nanopartículas de Ag presentes en la matriz del recubrimiento y la liberación de iones de Ag + al medio circundante, de tal forma que se induzca a la muerte de las bacterias o se inhiba su adherencia, sin afectar la viabilidad celular, es decir, sin ser citotóxico (Tianlu et al, 2014).…”

Synergistic Effect of Atmospheric-pressure Plasma and TiO2 Photocatalysis on Inactivation of Escherichia coli Cells in Aqueous Media

“…The presence of TiO 2 provides an additional mechanism for bacterial inactivation, whereby pathogens located on TiO 2 surface are subject to direct electron/hole exchange with the surface, affecting the cell membrane, which renders them more susceptible to oxidative damage by generated ROS. Once inside the cell, ROS can induce significant damage to intracellular components of the organism, including carbohydrates, lipids, proteins and nucleic acids, affecting cellular metabolism, and, at sufficiently high concentration, leading to cell death1419. Importantly, our results show that the photocatalytic activity of TiO 2 can be maintained over time, suggesting the proposed system may be used over relatively long periods of time without substantial loss in decontamination efficiency.…”

“…1, the surface of TiO 2 (particles or films) can be excited with light of wavelength shorter than 385 nm. The generated holes (h + ) and electrons (e − ) can react with H 2 O molecules to produce numerous reactive species (O 2 · − , OH), which can be efficiently used for microorganism inactivation1314, water treatment151617, air purification18, and cancer cell treatment19. As the generation of species is restricted by the broad band gap (> 3 eV) and low quantum efficiency of anatase TiO 2 , significant research efforts have been made to enhance the efficiency of the TiO 2 catalyst by means of doping with various metals, e.g.…”

FeOx magnetization enhancing E. coli inactivation by orders of magnitude on Ag-TiO2 nanotubes under sunlight

“…Several studies on the activity of Ag-TiO 2 enhancing the photocatalytic transformations of chemicals compared to TiO 2 have been reported [31][32][33][34][35][36]. Moreover some recent work describes the enhanced microbial inactivation of Ag-TiO 2 composites [37,38]. But the bacterial inactivation of Ag-TiO 2 compared to TiO 2 is strongly dependent on many variables that are difficult to control.…”