engleski

Induction of oxidative stress in tobacco seedlings treated with differently coated silver nanoparticles

Among various nanomaterials, silver nanoparticles (AgNPs)stand out due to their enhanced antimicrobial effects that have been exploited in many industrial sectors and daily life. Increase in AgNP consumption has led to greater potential for their release into the environment where they can be absorbed by plants and enter the food chain, posing a threat to human health. The main mechanism of AgNP toxicity lies in excessive ROS formation and subsequent oxidative stress induction, but the degree of oxidative damage depends on the intrinsic properties of AgNPs (size, shape and coating) which determine their stability against aggregation and dissolution in the environment. This study compared the effects of two differently coated AgNPs [polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB)] and ionic silver (AgNO3), applied in 100 μM concentration, on oxidative stress parameters in tobacco (Nicotiana tabacum L.) seedlings. In situ detection of ROS was performed using dihydroethidium for superoxide radical (O2-˙) and 2’, 7’-dichlorodihydrofluorescein diacetate for H2O2. Activity and changes in superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and pyrogallol peroxidase (PPX) were analysed spectrophotometrically and in gel, and their expression was determined with immunoblotting. Obtained results showed enhanced O2-˙ ̇and H2O2 production in all treated plants. Overall SOD, APX and PPX activities did not show significant changes in the treated plants ; however, isoenzyme patterns revealed differences in activity of certain isoforms upon exposure to AgNP-CTAB and AgNO3. Activity of CAT was significantly elevated in AgNP-CTAB treated seedlings, which was additionally confirmed in gel. Western blots showed higher abundance of aforementioned enzymes only in AgNO3 treated seedlings. These results show that the coating used for AgNP stabilisation plays an important role in AgNP toxicity, which cannot be ascribed only to the release of Ag+ ions.

oxidative stress ; tobacco seedlings ; antioxidant enzymes ; reactive oxygen species

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