title: Mechanism of antibacterial activity of copper nanoparticles.
abstract: In a previous communication, we reported a new method of synthesis of stable metallic copper nanoparticles (Cu-NPs), which had high potency for bacterial cell filamentation and cell killing. The present study deals with the mechanism of filament formation and antibacterial roles of Cu-NPs in E. coli cells. Our results demonstrate that NP-mediated dissipation of cell membrane potential was the probable reason for the formation of cell filaments. On the other hand, Cu-NPs were found to cause multiple toxic effects such as generation of reactive oxygen species, lipid peroxidation, protein oxidation and DNA degradation in E. coli cells. In vitro interaction between plasmid pUC19 DNA and Cu-NPs showed that the degradation of DNA was highly inhibited in the presence of the divalent metal ion chelator EDTA, which indicated a positive role of Cu(2+) ions in the degradation process. Moreover, the fast destabilization, i.e. the reduction in size, of NPs in the presence of EDTA led us to propose that the nascent Cu ions liberated from the NP surface were responsible for higher reactivity of the Cu-NPs than the equivalent amount of its precursor CuCl2; the nascent ions were generated from the oxidation of metallic NPs when they were in the vicinity of agents, namely cells, biomolecules or medium components, to be reduced simultaneously.
authors.affiliation: Department of Biochemistry and Biophysics, University of Kalyani, Kalyani-741 235, West Bengal, India.
authors.forename: Arijit Kumar
authors.initials: AK
authors.lastname: Chatterjee
authors.forename: Ruchira
authors.initials: R
authors.lastname: Chakraborty
authors.forename: Tarakdas
authors.initials: T
authors.lastname: Basu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism; D003300:Copper / Q000494:pharmacology*; D004249:DNA Damage; D004269:DNA, Bacterial / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D004587:Electrophoresis, Agar Gel; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects*; D005434:Flow Cytometry; D015227:Lipid Peroxidation / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D053768:Metal Nanoparticles / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D010084:Oxidation-Reduction / Q000187:drug effects; D010316:Particle Size; D017382:Reactive Oxygen Species / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D017382:Reactive Oxygen Species; D003300:Copper; D004492:Edetic Acid