[The influence of physical-chemical characteristics of surface modified copper nanoparticles on E. coli cell population growth suppression and on electrostatic properties of their membranes].

The biological activity of copper nanoparticles, able to suppress growth of E. coli cells population under contact interactions, was explored. Three types of samples with oxide layers of various sizes, thickness and composition were used in experiments. It was found out, that an increase in electron density on the external membrane of E. coli correlated with copper nanoparticles suppression capability and with lower activation energy of electron transfer on bacteria. The analysis of experimental data helps to correct conditions for obtaining nanoparticles with certain properties of their surface oxide layers. The character of temperature dependence of electron density reveals the electron type of conductivity in contact area of E. coli and nanoparticles. These results help to find approach to understanding the nature of toxic influence of copper nanoparticles on E. coli cells under contact interaction.

[Mechanism of the toxic action of copper nanoparticles on Escherichia coli bacteria].

Some features of contact interaction of Escherichia coli with Cu nanoparticles 75-100 nm in diameter have been studied. The analysis of variations in the amplitude of fluorescence of the negatively charged probe 1-anilinonaphthalene-8-sulfonate (ANS) in Gouy-Chapmen coordinates indicates an increase (in the absolute value) in the electrostatic potential of E. coli external membrane during the contact with Cu nanoparticles. The increase in the electrostatic potential correlates with the bacteriostatic influence on the growth of bacterial population. The calculations of tryptophan fluorescence quenching by iodide in the presence of Cu nanoparticles with the use of the Stern-Volmer equation revealed an increase in the constant of dynamic quenching and the availability of the fluorophore to suppressor.