Oxidative damage to Pseudomonas aeruginosa ATCC 27833 and Staphylococcus aureus ATCC 24213 induced by CuO-NPs

Abstract

The cytotoxicity of nanoparticles (NPs) and their properties are important issues in nanotechnology research. Particularly, NPs affect the metabolism of microorganisms due to NP interactions with some biomolecules. In order to assess the mechanisms underlying NPs toxicity, we studied the damage caused by copper oxide nanoparticles (CuO-NPs) on Staphylococcus aureus ATCC 24213 and Pseudomonas aeruginosa ATCC 27833. Spherical CuO-NPs characterized by their diameter (13 ± 3 nm) were synthesized with a maximum of 254 nm. These NPs reduced cell viability, with a minimum inhibitory concentration (MIC) of 500 and 700 ppm for Staphylococcus aureus and Pseudomonas aeruginosa, respectively. Surfactant was added to reduce the NP agglomeration, but it did not present any effect. The mechanism of CuO-NPs as antimicrobial agent was assessed by analyzing solubilized Cu, quantifying DNA release in the culture media, and measuring intracellular reactive oxygen species (ROS). CuO-NPs induced severe damage on cells as revealed by confocal optical microscopy and scanning electron microscopy (SEM). Our results indicated that CuO-NPs interacted with bacteria, triggering an intracellular signaling network which produced oxidative stress, leading to ROS generation. Finally, we concluded that CuO-NPs exhibited higher antibacterial activity on Gram-negative bacteria than on Gram-positive ones.

Fabrication of monodispersed copper oxide nanoparticles with potential application as antimicrobial agents

“…The UV-Vis absorption spectra revealed an absorbance as portrayed in Fig. 1a (black line) from ~ 300 to ~ 350 nm suggesting formation of copper oxide nanoparticles 40,41 . Albeit copper nanoparticles exhibit intense localized surface plasmon resonance in the visible region, the nanoparticles in the current study didn't show any peak in the visible region, while distinct broad band was observed at ~ 320 for surfactant stabilized copper oxide nanoparticles.…”

“…To elucidate the other proposed mechanism of toxicity of the Cu 2 O NPs species, an assay measuring cellular ROS generation have been employed on both B. subtilis CN2 and P. aeruginosa CB1 strains. Induction of cellular oxidative stress due to ROS formation has been attributed to be one of the principal bactericidal mechanisms of action of metal nanoparticles 10 , 41 , 52 , 53 . To examine if the toxicity observed in the Cu 2 O NPs studied is related to the ROS induced oxidative stress, the level of cellular oxidative stress triggered by Cu 2 O NPs at increasing dosages (0, 31.25, 62.5, 125 µg/mL) was measured by flow cytometer (FACS) using H 2 DCFDA staining method, which fluoresces in response to ROS inside the cells to fluorescent DCF 54 .…”

“…Although the mechanisms of antibacterial action of nanoparticles have not yet been fully elucidated, metallic nanoparticles and their related ions induced reactive oxygen species (ROS) generation, causing cell damage due to oxidative stress; adhesion and dissolution of metallic nanoparticles on bacterial membrane with subsequent permeability, disruption of membrane functionality and dissipation of the protein motive force have been reported as the main mechanisms 41,58 . The observed cellular toxicity and inhibitory effect of the Cu 2 O NPs may be attributed to the ions released into the media or particle related effect of the nanoparticles 17 .…”

Nano-Strategies to Fight Multidrug Resistant Bacteria—“A Battle of the Titans”

“…This effect was higher with AuNPs-laser, causing a rapid loss of bacterial cell membrane integrity due to the fact that laser light enhances at least one fold antimicrobial activity of AuNPs. Several other studies have addressed the role of metal NPs to induce MDR bacteria death via oxidative stress (Table 1 ) (Foster et al, 2011 ; Li et al, 2012b ; Rai et al, 2012 ; Zhang et al, 2013 ; Reddy L. S. et al, 2014 ; Singh R. et al, 2014 ; Pan et al, 2016 ; Courtney et al, 2017 ; Ulloa-Ogaz et al, 2017 ; Zaidi et al, 2017 ). Indeed, titanium dioxide NPs were shown to adhere to the surface of the bacterial cell and trigger the production of ROS, which in turns lead to damage of the structure of cellular components and consequent cell death (Foster et al, 2011 ).…”

“…Graphene oxide–iron oxide NPs have also demonstrated maximum antibacterial activity due to the generation of hydroxyl radicals and diffusion into bacterial cells (Pan et al, 2016 ). More recently, Ulloa-Ogaz and collaborators demonstrated that copper oxide NPs interact with bacteria, generating an intracellular signaling cascade that trigger oxidative stress and, thus, an antibacterial effect (Ulloa-Ogaz et al, 2017 ).…”