engleski

Effects of silver nanoparticles on physiological and proteomic responses of tobacco (Nicotiana tabacum) seedlings are coating-dependent

The harmful effects of silver nanoparticles (AgNPs) have been confirmed in many organisms, but the mechanism of their toxicity is not yet fully understood. In biological systems, AgNPs tend to aggregate and dissolve, so they are often stabilized by coatings that influence their physi- co-chemical properties. In this study, effects of AgNPs with different coatings [polyvinylpyrrol- idone (PVP) and cetyltrimethylammonium bromide (CTAB)] on oxidative stress appearance and proteome changes in tobacco (Nicotiana tabacum) seedlings have been examined. To discriminate between the nanoparticulate Ag form from the ionic one, the treatments with AgNO3, a source of Ag+ ions, were also included. Ag uptake and accumulation was found to be similarly effective upon exposure to all treatment types, although positively charged AgNP-CTAB showed less stability and generally stronger impact on investigated parameters in comparison with more stable and negatively charged AgNP-PVP and ionic silver (AgNO3). Both AgNP treatments induced reactive oxygen species (ROS) formation and increased expression of proteins involved in antioxidant defense, confirming oxidative stress as an important mechanism of AgNP phytotoxicity. However, mechanism of seedling responses differed depending on the type of AgNP used. The highest AgNP-CTAB concentration and CTAB coating resulted in increased H2O2 content and significant damage to lipids, proteins and DNA molecule as well as a strong activation of antioxidant en-zymes, especially CAT and APX. On the other hand, AgNP- PVP and AgNO3 treatments induced the nonenzymatic antioxidants by significantly increasing the proline and GSH content. Exposure to AgNP-CTAB also resulted with more noticeable changes in expression of proteins belonging to the Defense and stress response, Carbohydrate and energy metabolism and Storage proteins catego-ries in comparison to AgNP-PVP and AgNO3. Cysteine addition significantly reduced the effects of AgNP-PVP and AgNO3 for the majority of investigated parameters, indicating that AgNP-PVP toxicity mostly derives from released Ag+ ions. AgNP-CTAB effects, however, were not alleviated by cysteine addition, suggesting that their toxicity derives from the intrinsic properties of na- noparticles and coating itself.

silver nanoparticles ; coatings ; reactive oxygen species ; oxidative stress ; antioxidative enzymes ; nonenzymatic antioxidants ; protein expression

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