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ICP-AES Assessment of Silver Distribution in Plant Material after Exposure to Capped Ag-NPs

Engineered nanoparticles gained the greatest interest in wide areas of materials production and use. Among variety of produced nanomaterials, the most widely commercially used are silver nanoparticles (Ag-NPs) that are specifically applied in agriculture as antibacterial, antifungal and antioxidants. Despite the benefits that come with their applicability, the increasing concern about their impact on the environment is reflected through numerous research studies. For instance, the interactions between Ag-NPs and plants, the differentiation between ionic and particle specific silver, the morphological and proteomic changes are topics of greatest interest [1, 2]. Plasma based spectrometry methods are the most exploited element selective techniques for the total silver levels determination in studies of Ag-NPs [3]. Inductively coupled plasma atomic emission spectrometry (ICP-AES) provides sensitive simultaneous measurement of analyte emission lines in solutions of complex matrix and it was applied in our study of Ag-NPs exposure. We used ICP-AES for quantitative determination of silver content in tobacco seedlings (Nicotiana tabacum L.), which were exposed to Ag-NPs stress. The capping agents such as citrate, branched polyethylenimine (bPEI), and polyethylene glycol (PEG) were used for stabilization of Ag-NPs in solution that consists of growth medium (Murashige and Skoog medium). The tobacco seeds were treated with capped Ag-NPs and ionic silver as AgNO3 solution. After ten days of germination, the silver content was measured in the growth medium, in the seedlings tissue, and in the residual precipitate. Digestion of crude samples was performed by microwave assisted acid digestion (HNO3/H2O2). The accuracy of analytical procedure was tested by reference material CRM NIST-1573a. The most sensitive silver emission line of 328.068 nm was used for measurements. Detection limit (1.5 ng g-1) was determined using method blank that consisted of growth medium matrix. Concentrations of Ag in plant seedlings, growth medium, and residual precipitate were successfully determined in the concentration range of Ag 2.5 – 27 µg g-1. Rising of silver level in tissue was established in all experiments with Ag- NPs. The treatment with ionic silver showed drop of measured concentration after certain level. The variations between citrate Ag-NP, bPEI-Ag-NP, and PEG-Ag-NP were noticed as different silver level in tissue after treatment with differently capped NPs. The comparison of measured results showed that the distribution of silver in plant tissue relates to initially applied silver species.

Ag-NPs ; capped nanoparticles ; ICP-AES ; tobacco seedlings

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