title: A simple robust method for synthesis of metallic copper nanoparticles of high antibacterial potency against E. coli.
abstract: A method for preparation of copper nanoparticles (Cu-NPs) was developed by simple reduction of CuCl2 in the presence of gelatin as a stabilizer and without applying stringent conditions like purging with nitrogen. The NPs were characterized by spectrophotometry, dynamic light scattering, x-ray diffraction, transmission electron microscopy, atomic force microscopy and x-ray photoelectron spectroscopy. The particles were about 50-60 nm in size and highly stable. The antibacterial activity of this Cu-NP on Gram-negative Escherichia coli was demonstrated by the methods of agar plating, flow cytometry and phase contrast microscopy. The minimum inhibitory concentration (3.0 µg ml(-1)), minimum bactericidal concentration (7.5 µg ml(-1)) and susceptibility constant (0.92) showed that this Cu-NP is highly effective against E. coli at a much lower concentration than that reported previously. Treatment with Cu-NPs made E. coli cells filamentous. The higher the concentration of Cu-NPs, the greater the population of filamentous cells; average filament size varied from 7 to 20 µm compared to the normal cell size of ∼2.5 µm. Both filamentation and killing of cells by Cu-NPs (7.5 µg ml(-1)) also occurred in an E. coli strain resistant to multiple antibiotics. Moreover, an antibacterial effect of Cu-NPs was also observed in Gram-positive Bacillus subtilis and Staphylococcus aureus, for which the values of minimum inhibitory concentration and minimum bactericidal concentration were close to that for E. coli.
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: Raj Kumar
authors.initials: RK
authors.lastname: Sarkar
authors.forename: Asoke Prasun
authors.initials: AP
authors.lastname: Chattopadhyay
authors.forename: Pulakesh
authors.initials: P
authors.lastname: Aich
authors.forename: Ruchira
authors.initials: R
authors.lastname: Chakraborty
authors.forename: Tarakdas
authors.initials: T
authors.lastname: Basu