Magnetite nanoparticles coated with citric acid are not phytotoxic and stimulate soybean and alfalfa growth.

In this work, the internalization and distribution of citric acid-coated magnetite nanoparticles (here, Fe3O4-NPs) in soybean and alfalfa tissues and their effects on plant growth were studied. Both legumes were germinated in pots containing an inert growing matrix (vermiculite) to which Hoagland solution without (control, C), with Fe3O4-NPs (50 and 100 mgironL-1, NP50 and NP100), or with the same amount of soluble iron supplied as Fe-EDTA (Fe50, Fe100) was added once before sowing. Then, plants were watered with the standard nutrient solution. The observation of superparamagnetic signals in root tissues at harvest (26 days after emergence) indicated Fe3O4-NPs uptake by both legumes. A weak superparamagnetic signal was also present in the stems and leaves of alfalfa plants. These findings suggest that Fe3O4-NPs are readily absorbed but not translocated (soybean) or scarcely translocated (alfalfa) from the roots to the shoots. The addition of both iron sources resulted in increased root weight; however, only the addition of Fe3O4-NPs resulted in significantly higher root surface; shoot weight also increased significantly. As a general trend, chlorophyll content enhanced in plants grown in vermiculite supplemented with extra iron at pre-sowing; the greatest increase was observed with NP50. The only antioxidant enzyme significantly affected by our treatments was catalase, whose activity increased in the roots and shoots of both species exposed to Fe3O4-NPs. However, no symptoms of oxidative stress, such as increased lipid peroxidation or reactive oxygen species accumulation, were evidenced in any of these legumes. Besides, no evidence of cell membrane damage or cell death was found. Our results suggest that citric acid-coated Fe3O4-NPs are not toxic to soybean and alfalfa; instead, they behave as plant growth stimulators.

Selective contrast agents with potential to the earlier detection of tumors: Insights on synthetic pathways, physicochemical properties and performance in MRI assays.

Magnetic iron oxide nanoparticles (MNPs) have been prepared and stabilized with three organic acids (tartaric, malic and ascorbic) in order to obtain biocompatible and water dispersible MNPs with potential to bind specifically to tumoral cancer cells. An in deep characterization was performed aiming to verify the presence and effect of the coating and stabilizer on MNPs surface. Besides the mechanisms followed by the different acids to bind MNPs were elucidated and used to justify the differences in the physicochemical properties of each formulation. Data related to characterization revealed that MNPs coated with ascorbic acid (MNPs-AA) resulted the most suitable in terms of their size, surface charge and stability along the time. Besides, ascorbic acid may be recognized by GLUTs receptors that are overexpressed in several kinds of tumoral cells. Therefore, MNPs-AA was selected to explore its performance in both MRI and in vitro assays using human colon cancer cells HCT 116. MRI experiments were performed in clinical equipment using a series of aqueous dispersions of MNPs-AA that were evaluated as T2 contrast agent. The T2- weighted images obtained as well as the calculated r2, indicated that MNPs-AA could act as efficient T2 contrast agent for MRI. Regarding in vitro assays, MNPs-AA did not alter the cellular function neither exert cytotoxicity using the three explored doses. The internalization of the nanoparticles on the cellular structure was confirmed quanti and qualitatively using atomic absorption spectroscopy and Prussian blue techniques respectively. From these results, it emerges that ascorbic acid coated-magnetite nanoparticles may be used as alternative contrast agent to avoid or minimize some toxicological issues related to the widely used gadolinium.