Research of toxic behavior of copper nanoparticles: effect on electrosurface and biochemical parameters of bacterial cells

This research is aimed at the investigation the electrosurface and biochemical parameters of bacterial cells B. cereus B4368, L. plantarum, E. coli K-A, P. fluorescens B5040 under the influence of copper in ionic form and as nanoparticles in order to determine the nature and level of their toxic effect on bacteria. Copper nanoparticles synthesized in aqueous solution with NaBH4 and stabilized with dextran were used. Changes in membrane transport parameters were assessed by the value of ATPase activity; changes in transmembrane potential were assessed by the method of penetrating tetraphenylphosphonium cations (TPP+); and bacterial integrity was assessed by UV spectroscopy of cellular metabolites. A concentration-dependent inhibition of the membrane ATPase reaction and dissipation of the transmembrane potential under the action of both forms of copper was found, and the inhibitory effect in the case of the nanoparticles was on average 20 % higher than in the ionic form. As a result of heterocoagulation of dextran-stabilized copper nanoparticles and bacteria, a decrease in the negative ξ - potential of bacteria was observed, which was 40 % more effective under the action of copper nanoparticles compared to Cu2+ ions. The most significant changes in membrane parameters were observed in the range 10–60 μM of copper concentrations. With B. cereus B4368 cells taken as an example, we found a violation of the barrier function of their cell membrane under the influence of both copper preparations. In the case of copper nanoparticles, nucleic acid leakage from the bacterial cytoplasm was detected, which was confirmed by the absorption band at 260 nm. The results obtained indicate a high level of sensitivity of the studied electrosurface and biochemical parameters of bacterial cells to the effects of ionic and nanoparticle copper, which allows them to be used as indicators of the toxicity of metal nanoparticles in the development of metal-containing probiotic preparations.