title: Engineered ZnO and TiO(2) nanoparticles induce oxidative stress and DNA damage leading to reduced viability of Escherichia coli.
abstract: Extensive use of engineered nanoparticle (ENP)-based consumer products and their release into the environment have raised a global concern pertaining to their adverse effects on human and environmental health. The safe production and use of ENPs requires improvement in our understanding of environmental impact and possible ecotoxicity. This study explores the toxicity mechanism of ZnO and TiO(2) ENPs in a gram-negative bacterium, Escherichia coli. Internalization and uniform distribution of characterized bare ENPs in the nano range without agglomeration was observed in E. coli by electron microscopy and flow cytometry. Our data showed a statistically significant concentration-dependent decrease in E. coli cell viability by both conventional plate count method and flow cytometric live-dead discrimination assay. Significant (p<0.05) DNA damage in E. coli cells was also observed after ENP treatment. Glutathione depletion with a concomitant increase in hydroperoxide ions, malondialdehyde levels, reactive oxygen species, and lactate dehydrogenase activity demonstrates that ZnO and TiO(2) ENPs induce oxidative stress leading to genotoxicity and cytotoxicity in E. coli. Our study substantiates the need for reassessment of the safety/toxicity of metal oxide ENPs.
authors.affiliation: Nanomaterial Toxicology Group, Indian Institute of Toxicology Research, Council of Scientific and Industrial Research, Lucknow 226001, Uttar Pradesh, India.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Kumar
authors.forename: Alok K
authors.initials: AK
authors.lastname: Pandey
authors.forename: Shashi S
authors.initials: SS
authors.lastname: Singh
authors.forename: Rishi
authors.initials: R
authors.lastname: Shanker
authors.forename: Alok
authors.initials: A
authors.lastname: Dhawan
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage / Q000187:drug effects; D004269:DNA, Bacterial / Q000378:metabolism*; D054750:Ecotoxicology; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure; D005434:Flow Cytometry; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D053768:Metal Nanoparticles / Q000008:administration & dosage / Q000009:adverse effects* / Q000737:chemistry / Q000648:ultrastructure; D008854:Microscopy, Electron; D018384:Oxidative Stress / Q000187:drug effects; D014025:Titanium / Q000009:adverse effects* / Q000737:chemistry / Q000378:metabolism; D015034:Zinc Oxide / Q000009:adverse effects* / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C009495:titanium dioxide; D014025:Titanium; D007770:L-Lactate Dehydrogenase; D015034:Zinc Oxide