Oxidative stress and histopathological changes in several organs of mice injected with biogenic silver nanoparticles.

The widespread use of silver nanoparticles (AgNPs) requires a study of their safety. The aim of the present study was to assess the levels of oxidative stress markers and histopathological changes in the experimental model of sarcoma S-180 of outbred mice caused by biogenic AgNPs. AgNPs were synthesized using 50% ethanol extract of Ocimum araratum leaves that was standardized for rosmarinic acid content. The effects of AgNPs were tested on chemiluminescence (ChL), malonic dialdehyde (MDA) content and activity of superoxide dismutase (SOD) in healthy and experimental model of sarcoma S-180 mice. It was shown that, under the influence of AgNPs, the intensity of ChL decreased, in contrast with control groups (with the exception of the hepatocytes of animals with transplanted sarcoma). The presence of AgNPs leads to the decrease of MDA in the tissues of healthy mice and to a slight increase of MDA content in the tumour and kidney tissues. AgNPs neutralize the activity of SOD in kidney tissue samples in animals with transplanted sarcoma, and in tumour tissue, they reduce SOD activity by three times. The results of the histological analysis indicate that AgNPs not only cause the destruction of tumour tissue but also lead to structural changes in hepatocytes and nephrons, which can affect the function of these organs. AgNPs are potential agents for antitumor therapy. Future studies are needed using biocompatible non-toxic NPs that meet the requirement for these drugs.

Antibacterial effects of iron oxide (Fe3O4) nanoparticles: distinguishing concentration-dependent effects with different bacterial cells growth and membrane-associated mechanisms.

Nowadays, the influence of nanoparticles (NPs) on microorganisms attracts a great deal of attention as an alternative to antibiotics. Iron oxide (Fe3O4) NPs' effects on Gram-negative Escherichia coli BW 25113 and Gram-positive Enterococcus hirae ATCC 9790 growth and membrane-associated mechanisms have been investigated in this study. Growth specific rate of E. coli was decreased, indicating the bactericidal effect of Fe3O4 NPs. This inhibitory effect of NPs had a concentration-dependent manner. The reactive oxygen species together with superoxide radicals and singlet oxygen formed by Fe3O4 NPs could be the inhibition cause. Fe3O4 NPs showed opposite effects on E. hirae: the growth stimulation or inhibition was observed depending on NPs concentration used. Addition of NPs altered redox potential kinetics and inhibited H2 yield in E. coli; no change in intracellular pH was determined. Fe3O4 NPs decreased H+-fluxes through bacterial membrane more in E. coli than in E. hirae even in the presence of DCCD and increased ATPase activity more in E. hirae than in E. coli. Our results showed that the Fe3O4 NPs demonstrate differentiating effects on Gram-negative and Gram-positive bacteria likely due to the differences in bacterial cell wall structure and metabolic peculiarities. Fe3O4 NPs of different concentrations have no hemolytic (cytotoxic) activity against erythrocytes. Therefore, they can be proposed as antibacterial agents in biomedicine, biotechnology, and pharmaceutics.

Biphasic dose-response of antioxidants in hypericin-induced photohemolysis.

In the present paper the photodynamic effect of hypericin on superoxide dismutase activity and the possibility of reduction of hypericin phototoxicity by antioxidants were studied. It was shown an almost twice decrease in superoxide dismutase activity of red blood cells under the photosensitization by hypericin. The influence of antioxidants (ascorbic acid and quercetin) on hypericin photodynamic action has revealed that these antioxidants suppress or stimulate photohemolysis caused by hypericin. The photosensitization reaction realized by hypericin could be shifted from type II to type I or vice versa by manipulating the antioxidant concentration. Strengthening of photohemolysis by antioxidants in some concentrations indicates the switching of alternative mechanisms of hypericin photodynamic action and its complicated manner. Thus the selection of antioxidant concentrations is of extreme importance for changing the efficacy of photodynamic therapy with hypericin.