engleski

Acute exposure to silver nanoparticles and ionic silver triggers oxidative stress in tobacco plants

Antimicrobial properties of silver and enhanced reactivity when applied in nanoparticle form (AgNPs) leads to their increased utilisation in consumer products. However, their increasing release into water or soil represents a potential environmental hazard. AgNPs can give rise to detrimental effects in plants, mainly through excess generation of reactive oxygen species (ROS), leading to induction of oxidative stress. In this work, detached roots of in vitro grown tobacco (Nicotiana tabacum) plants were exposed to AgNPs stabilised with cetyltrimethylammonium bromide (CTAB) or polyvinylpyrrolidone (PVP) coating, or to ionic silver (AgNO3), applied in the same concentration (100 μmol/L) in ultrapure water for 24 h. The aim was to investigate in situ early physiological responses that are the first signs of stressful conditions. Generation of ROS in root cells was monitored by confocal laser scanning microscopy, using highly sensitive and specific fluorescent probes: dihydroethidium (DHE) to detect O2- and 2’, 7’-dichlorofluorescein- diacetate (H2DCF-DA) to detect H2O2. Propidium iodide was used to verify cell viability. Increased amount of H2O2 and O2- was observed in roots exposed to either AgNPs or AgNO3 comparing to non-exposed roots, which was correlated to an increased percentage of dead cells, while the changes were most prominent after AgNP-CTAB treatment. Additionally, AgNPs were visualised in root cells and their uptake and accumulation could be linked to excess generation of ROS. Results show that AgNPs not only compromised cellular redox-homeostasis but possibly caused cell necrosis, while different level of impact was observed depending on the form of applied silver and possibly on the intrinsic properties of the AgNP coatings.

confocal microscopy ; fluorescent probes ; nanosilver coatings ; phytotoxicity ; reactive oxygen species

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