Toxicological Impact Studies Based on Escherichia coli Bacteria in Ultrafine ZnO Nanoparticles Colloidal Medium

Abstract

We report here preliminary studies of biocidal effects and cellular internalization of ZnO nanoparticles on Escherichia coli bacteria. ZnO nanoparticles were synthesized in di(ethylene glycol) (DEG) medium by forced hydrolysis of ionic Zn2+ salts. Particle size and shape were controlled by addition of small molecules and macromolecules such as tri-n-octylphosphine oxide, sodium dodecyl sulfate, polyoxyethylene stearyl ether, and bovine serum albumin. Transmission electron microscopy (TEM) and X-ray diffraction analyses were used to characterize particle structure, size, and morphology. Bactericidal tests were performed in Luria-Bertani medium on solid agar plates and in liquid systems with different concentrations of small and macromolecules and also with ZnO nanoparticles. TEM analyses of bacteria thin sections were used to study biocidal action of ZnO materials. The results confirmed that E. coli cells after contact with DEG and ZnO were damaged showing a Gram-negative triple membrane disorganization. This behavior causes the increase of membrane permeability leading to accumulation of ZnO nanoparticles in the bacterial membrane and also cellular internalization of these nanoparticles.

Antibacterial properties of F-doped ZnO visible light photocatalyst

“…Furthermore it was noted that among various ZnO powders used in the experiment, powder ZnO:TFA 1:1 was the most effective against E. coli and S. aureus when the visible light was available (log red 2.88 and 4.62, respectively). Based on the studies performed by others [27][28][29][30][31], it is believed that when the light is not available, the primary toxic effect of ZnO on microorganisms can be associated with the release of zinc ions causing disruption of the cell membrane activity and the formation of intercellular reactive oxygen species, mostly H 2 O 2 [32][33][34][35][36][37]. Photocatalysts such as TiO 2 or ZnO activated by UV or/and visible light (Fig.…”

Antibacterial Composite Layers on Ti: Role of ZnO Nanoparticles

“…It cannot be too large because otherwise the nanoparticles may be transformed into solid multilayer of a reduced solubility. Moreover, which is especially important for Zn 2+ ions, it should not be too small because bacteria may metabolize zinc as an oligoelement [15]. In this work the antibacterial properties of composite coatings on Ti consisting of TiO 2 nanotubes loaded with ZnO nanoparticles were evaluated.…”

Antibacterial Composite Layers on Ti: Role of ZnO Nanoparticles

“…It cannot be too large because otherwise the nanoparticles may be transformed into solid multilayer of a reduced solubility. Moreover, which is especially important for Zn 2+ ions, it should not be too small because bacteria may metabolize zinc as an oligoelement [15].…”