In vivo synthesis of nanomaterials in plants: location of silver nanoparticles and plant metabolism

Abstract

Metallic nanoparticles (MeNPs) can be formed in living plants by reduction of the metal ions absorbed as soluble salts. It is very likely that plant metabolism has an important role in MeNP biosynthesis. The in vivo formation of silver nanoparticles (AgNPs) was observed in Brassica juncea, Festuca rubra and Medicago sativa. Plants were grown in Hoagland's solution for 30 days and then exposed for 24 h to a solution of 1,000 ppm AgNO3. In the leaf extracts of control plants, the concentrations of glucose, fructose, ascorbic acid, citric acid and total polyphenols were determined. Total Ag content in plant fractions was determined by inductively coupled plasma atomic emission spectroscopy. Despite the short exposure time, the Ag uptake and translocation to plant leaves was very high, reaching 6,156 and 2,459 mg kg−1 in B. juncea and F. rubra, respectively. Ultrastructural analysis was performed by transmission electron microscopy (TEM), and AgNPs were detected by TEM X-ray microanalysis. TEM images of plant fractions showed the in vivo formation of AgNPs in the roots, stems and leaves of the plants. In the roots, AgNPs were present in the cortical parenchymal cells, on the cell wall of the xylem vessels and in regions corresponding to the pits. In leaf tissues, AgNPs of different sizes and shapes were located close to the cell wall, as well as in the cytoplasm and within chloroplasts. AgNPs were not observed in the phloem of the three plant species. This is the first report of AgNP synthesis in living plants of F. rubra. The contents of reducing sugars and antioxidant compounds, proposed as being involved in the biosynthesis of AgNPs, were quite different between the species, thus suggesting that it is unlikely that a single substance is responsible for this process.MSC 201092 Biology and other natural sciences; 92Cxx Physiological, cellular and medical topics; 92C80 Plant biology

Barriers, pathways and processes for uptake, translocation and accumulation of nanomaterials in plants – Critical review

“…From the xylem, NPs can distribute within the rest of the plant and be loaded into the phloem. Nanoparticles in the xylem have often been observed (Al-Salim et al, 2011;Corredor et al, 2009;Huang et al, 2011;Hussain et al, 2013;Marchiol et al, 2014;Wang et al, 2012b). Pits equipped with pit membranes in the tracheids mainly limit NP transport in the xylem vasculature, and primary pit fields in sieve areas are the bottlenecks of the phloem sieve cells (Fahn, 1982;Raven, 2003).…”

Biocompatibility of silver containing silica films on Bioverit® II middle ear prostheses in rabbits

“…67 This mechanism has been already described in plants after exposure to different silver nitrate doses. 68 In animals, the intracellular formation of silver nanoparticles was also confirmed after oral exposure to silver ions in rats. 69 This procedure can explain the detection of silver nanoparticles in cytosol of our mucosal samples.…”

Source and Pathway of Silver Nanoparticles to the Environment

“…The formed AgNPs were densely around chloroplasts of Brassica juncea, which areas were associated with a high content of reducing sugars, and therefore reducing sugars were implicated as the reagents responsible for this reduction [45]. However, another study on the formation of AgNPs in living Brassica juncea, Festuca rubra, and Medicago sativa showed that the contents of reducing sugars and antioxidant com-pounds were quite different among the species, which suggested that it was unlikely that a single substance was responsible for this process [46]. The biosynthesized AgNPs by Chlamydomonas reinhardtii were localized in the peripheral cytoplasm and at one side of flagella root, the site of pathway of adenosine triphosphate transport and its synthesis related enzymes, which provided an evidence for the involvement of oxidoreductive proteins in this reduction process [47].…”