Studying the redox status of paramecium caudatum cells under influence of molybdenum, zinc, copper oxide nanoparticles and synthetic antioxidants

Aims. To study the effect of CuO, ZnO and MoO3 nanoparticles on the vital functions of the single cell organism Paramecium caudatum; to analyse the activity of antioxidant cellular enzymes: SOD and CAT, as well as to evaluate the possibility of cells protection against oxidative stress by endogenous antioxidants. Methods. Paramecium caudatum cells were cultured under standard conditions for this test subject [3-4]. The toxicity of metal nanoparticles, PMCO (20-60 nm), PM ZnO (40-80 nm) and PM MoO3 (5-20 nm) (Laboratory of Physical Modelling of Two-Phase Flows, United Institute of High Temperatures, Russian Academy of Sciences) was evaluated by determining the LC50 lethality index of the concentration at which 50% of Paramecium caudatum population was killed. Free-floating cells were then exposed for 48 h to sublethal concentrations of NPs metal oxides in moderately hard water with dissolved antioxidant. The efficacy of emoxipine (10 mg/ml), mexidol (50 mg/ml) ascorbic acid AA (25 mg/ml) and nicotinic acid NA (10 mg/ml) was investigated; for this purpose cell number, cell membrane condition, changes of intracellular organelle shape were recorded (Levenhuk C310 digital camera microscope, 3.1 Mpixel). Results. We found that the presence of metal oxides induced a significant decrease (p < 0.05) in the number of viable Paramecium caudatum cells, in 24 h there were 58 % deaths from CuO, 43 % deaths from ZnO and 40 % deaths from MoO3, but in 48 h 92 %, 88 % and 75 %, respectively. Copper oxide PM were the most toxic to cells, with an LC50 of 25 mg/l; for ZnO PM and MoO3 PM, the lethal concentration was equal and higher than 50 mg/l. negative pressure of metal-containing NPs led to osmotic disorganization, which was accompanied by an increase in vacuoles, abnormal bending and membrane rupture. Conclusions. Our results demonstrated that oxidative stress is one of the leading mechanisms of toxicity of PM oxides of transition metals such as copper, zinc and molybdenum. When the single-celled organism Paramecium caudatum was exposed to the studied NPs, destructive damages of membrane structures, changes in functions and morphology of organelles leading to cell death were observed. It should be noted that under such abiotic stress, the viability of Paramecium caudatum in general is the result of a complex interaction of the cells' own antioxidant system as well as the specific characteristics of NPs (size and solubility) and additional environmental factors, such as the presence of compounds with antioxidant activity in it.