Sub-toxic effects of CuO nanoparticles on bacteria: kinetics, role of Cu ions and possible mechanisms of action.
The sub-toxic effects of CuO nanoparticles (nano-CuO) were evaluated using three recombinant luminescent Escherichia coli bacteria responding specifically to (i) reactive oxygen species (ROS), (ii) single-stranded DNA breaks and (iii) bioavailable Cu ions. Using these sensors we showed that nano-CuO induces the formation of superoxide anions, hydrogen peroxide and single-stranded DNA already at very low sub-toxic levels (0.1 mg Cu/L). The maximal sub-toxic response of all biosensors to nominal concentrations of nano-CuO, micro-CuO (size control) and CuSO(4) (solubility control) occurred at ~6, ~600 and ~0.6 mg Cu/L, respectively. According to the chemical analysis all the latter concentrations yielded ~0.6 mg of soluble Cu/L, indicating that dissolution of CuO particles was the key factor triggering the ROS and DNA damage responses in bacteria. Cu-ions chelation studies also showed that CuO particles were not involved in these stress responses. The solubilization results were confirmed by Pseudomonas fluorescens Cu-ion sensor.
Laboratory of Molecular Genetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia. olesja.bondarenko@kbfi.ee
Olesja
O
Bondarenko
Angela
A
Ivask
Aleksandr
A
Käkinen
Anne
A
Kahru
D015374:Biosensing Techniques; D003300:Copper / Q000737:chemistry / Q000494:pharmacology*; D004249:DNA Damage / Q000187:drug effects; D004926:Escherichia coli / Q000737:chemistry / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D007477:Ions / Q000737:chemistry / Q000494:pharmacology; D007700:Kinetics; D053758:Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects; D011551:Pseudomonas fluorescens / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
D007477:Ions; D017382:Reactive Oxygen Species; D003300:Copper; C030973:cupric oxide