Antibacterial effect of chronic exposure of low concentration ZnO nanoparticles onE. coli

Abstract

The toxicity effect due to chronic exposure of ZnO nanoparticles (NPs) was systematically studied by repeatedly treating different lower concentrations of ZnO nanoparticles with culture media of E. coli strain. The chronic exposure of ZnO NPs of concentrations below minimum inhibitory concentration (MIC) exhibited higher toxicity than the single exposure of higher concentrations. Most striking result was 57% inhibition of growth corresponding to chronic exposure of 0.06 mg/mL of ZnO NPs which was two folds more than that exhibited by single exposure of 0.30 mg/mL ZnO NPs. The toxicity of ZnO NPs in E. coli was studied in the light of formation of reactive oxygen species (ROS), measured as malondialdehyde (MDA) equivalent by thiobarbituric acid-ROS (TBARS) assay, and effect of Zn dissolution from ZnO NPs. Higher inhibition of growth for the chronic exposure batches were correlated with higher ROS generation, which subsequently contributed to cause membrane lipid peroxidation, confirmed from observation of cell wall deformation by scanning electron microscopy study and energy dispersive X-ray analysis showed adherence of ZnO NPs on cell wall. The possibility of membrane lipid peroxidation was addressed by revealing in vitro oxidation of oleic acid, which is a monounsaturated fatty acid. Further in this study we have shown that the dissolution of ZnO NPs at pH 7.4 was not significant to cause Zn-induced toxicity.

Oxidative stress-mediated genotoxic effect of zinc oxide nanoparticles on Deinococcus radiodurans

“…Cytotoxic and genotoxic effects of ZnO NPs towards many bacterial (E. coli, C. jejuni) (Xie et al 2011;Dutta et al 2013) and mammalian cells (Gong et al 2017) have been extensively investigated by several research groups. Zinc is considered as an important element for the growth and survival of bacterial cells, however, their concentration beyond critical limits can severely inhibit the activity of functional enzymes of bacteria such as NADH dehydrogenase, glutathione reductase, and peroxidase.…”

The Advancing of Zinc Oxide Nanoparticles for Biomedical Applications

“…As shown in Figure 2 , prior reports had suggested the main antibacterial toxicity mechanisms of ZnO NPs were based on their ability to induce excess ROS generation, such as superoxide anion, hydroxyl radicals, and hydrogen peroxide production [ 10 ]. The antibacterial activity may involve the accumulation of ZnO NPs in the outer membrane or cytoplasm of bacterial cells and trigger Zn 2+ release, which would cause bacterial cell membrane disintegration, membrane protein damage, and genomic instability, resulting in the death of bacterial cells [ 75 – 77 ].…”

“…Presently, Gram-negative Escherichia coli ( E. coli ) and Gram-positive Staphylococcus aureus ( S. aureus ) are mainly chosen as model bacteria to evaluate the antibacterial activity of ZnO NPs [ 77 , 78 ]. Some other Gram-negative bacteria such as Pseudomonas aeruginosa ( P. aeruginosa ) [ 24 , 79 ], Proteus vulgaris ( P. vulgaris ) [ 80 ], Vibrio cholerae ( V. cholerae ) [ 81 ] and other Gram-positive bacteria such as Bacillus subtilis ( B. subtilis ) [ 82 ] and Enterococcus faecalis ( E. faecalis ) [ 83 ] are also investigated.…”

In Vitro Analysis: The Antimicrobial and Antioxidant Activity of Zinc Oxide Nanoparticles From Curcuma Longa

“…ZnO NP antibacterial activity may associate with the accretion in bacterial cells cytoplasm and promote the release of Zn 2+ . It leads to the fragmentation of bacterial cell membrane, damage in membrane protein and genomic weakness resulting in the death of bacteria [27][28][29]. Fig.…”