Rhamnolipids as Green Stabilizers of nZVI and Application in the Removal of Nitrate From Simulated Groundwater.

Environmental contamination caused by inorganic compounds is a major problem affecting soils and surface water. Most remediation techniques are costly and generally lead to incomplete removal and production of secondary waste. Nanotechnology, in this scenario with the zero-valent iron nanoparticle, represents a new generation of environmental remediation technologies. It is non-toxic, abundant, cheap, easy to produce, and its production process is simple. However, in order to decrease the aggregation tendency, the zero-iron nanoparticle is frequently coated with chemical surfactants synthesized from petrochemical sources, which are persistent or partially biodegradable. Biosurfactants (rhamnolipids), extracellular compounds produced by microorganisms from hydrophilic and hydrophobic substrates can replace synthetic surfactants. This study investigated the efficiency of a rhamnolipid biosurfactant on the aggregation of nanoscale zer-valent iron (nZVI) and its efficiency in reducing nitrate in simulated groundwater at pH 4.0. Two methods were tested: 1) adding the rhamnolipid during chemical synthesis and 2) adding the rhamnolipid after chemical synthesis of nZVI. Scanning electron microscopy field emission, X-ray diffractometry, Fourier transform infrared spectroscopy, thermogravimetric analysis, Dynamic Light Scattering, and zeta potential measurements were used to characterize bare nZVI and rhamnolipid-coated nZVI. The effects of the type of nZVI and initial NO3 concentration were examined. Nanoscale zer-valent iron with the addition of the rhamnolipid after synthesis achieved the best removal rate of nitrate (about 78%), with an initial nitrate concentration of 25 mg L-1. The results suggest that nZVI functionalized with rhamnolipids is a promising strategy for the in situ remediations of groundwater contaminated by NO3, heavy metal, and inorganic carbon.

Evaluation of antiplasmodial activity and cytotoxicity assays of amino acids functionalized magnetite nanoparticles: Hyperthermia and flow cytometry applications.

We report the synthesis of magnetite nanoparticles (MNP) and their functionalization with glycine (MNPGly), ß-alanine (MNPAla), L-phenylalanine (MNPPhAla), D-(-)-α-phenylglycine (MNPPhGly) amino acids. The functionalized nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), electron paramagnetic resonance (EPR), vibrating sample magnetometry (VSM), Mössbauer spectroscopy (MS), magnetic hyperthermia (MH), dynamic light scattering and zeta potential. The functionalized nanoparticles had isoelectric points (IEP) at pH ≃ 4.4, 5.8, 5.9 and 6.8 for samples MNPGly, MNPAla, MNPPhGly and MNPPhAla, respectively, while pure magnetite had an IEP at pH 5.6. In the MH experiments, the samples showed specific absorption rate (SAR) of 64, 71, 74, 81 and 66 W/g for MNP, MNPGly, MNPAla, MNPPhGly, and MNPPhAla, respectively. We used a flow cytometric technique to determine the cellular magnetic nanoparticles plus amino acids content. Magnetic fractionation and characterization of Resovist® magnetic nanoparticles were performed for applications in magnetic particle imaging (MPI). We have also studied the antiproliferative and antiparasitic effects of functionalized MNPs. Overall, the data showed that the functionalized nanoparticles have great potential for using as environmental, antitumor, antiparasitic agents and clinical applications.

Synthesis and colloidal characterization of folic acid-modified PEG-b-PCL Micelles for methotrexate delivery.

Hydrophobic drugs, such as methotrexate, are not easily delivered into the human body. Therefore, the use of amphiphilic nanoplatforms to the transport of these drugs through the bloodstream is a challenge. While the hydrophobic region interacts with the drug, the hydrophilic outer layer enhances its bioavailability and circulation time. Poly (ethylene glycol)-block-poly(ε-caprolactone) PEG-b-PCL micelles are biodegradable and biocompatible, allowing its use as a nanocarrier for drug delivery systems. The stealth property of PEG that composes the outer layer of nanoplatforms, makes the micelle unperceivable to phagocytic cells, increasing the circulation time in the human body. In addition, folic acid functionalization enables micelle selectively targeting to cancer cells, improving treatment efficiency and reducing side effects. In this work, PEG-b-PCL copolymer was synthesized by ring opening polymerization (ROP) of the ε-caprolactone with Poly(ethylene glycol) as a macroinitiator and tin(II) 2-ethyl hexanoate as a catalyst. Functionalization of such micelles with folic acid occurred through the modification of the PEG terminal group. The surface modification of the copolymer micelles resulted in higher critical micellar concentration (CMC), increasing approximately 100 times. The synthesis of the copolymers resulted in molecular weight around 3000 g mol-1 with low polydispersity. The polymer micelles have a hydrodynamic diameter in the range of 100-200 nm and the functionalized sample doesn't show aggregation in the considered pH range. High incorporation efficiency was obtained with a minimum percentage of 85%. The drug release profile and linearization from the Peppas model confirmed the interaction of methotrexate with the hydrophobic segment of the copolymer and its release mechanism by relaxation and/or degradation of the chains, making PEG-b-PCL micelles suitable candidates for hydrophobic drug delivery systems.

Magnetic nanoparticles as a support for a copper (II) complex with nuclease activity.

Magnetic nanoparticles have been extensively explored for the development of platforms for drug delivery and imaging probes. In this work, we have used a modular capping strategy to produce magnetic gold-coated Fe3O4 (Fe3O4@Au) nanoparticles, which have been decorated with a copper (II) complex containing a thioether derivative of clip-phen (Fe3O4@Au@Cu), where the complex [Cu(2CP-Bz-SMe)]2+ has affinity to bind DNA and proven nuclease activity (2CP-Bz-SMe=1,3-bis((1,10-phenanthrolin-2-yl)oxy)-N-(4-(methylthio)benzylidene)propan-2-imine). The functionalization of Fe3O4@Au with the copper complex occurs through the sulfur atom of the thioether moiety, as indicated by Raman scattering on surface. The magnetic measurements showed the nanomaterial Fe3O4@Au@Cu is still magnetic although the gold shell and the functionalization with the copper complex have diminished the magnetization due to the dilution of the magnetic core. The nuclease assays performed with Fe3O4@Au@Cu indicate that the nuclease activity of the nanomaterial toward the plasmid DNA involves an oxidative pathway in which H2O2 species is involved as intermediate in a Fenton-like reaction. Based on the electron paramagnetic resonance spectra (aN = 15.07 G, aH = 14.99 G), such nuclease activity is assigned, essentially, to the HO species indicating that the radical production property of [Cu(2CP-Bz-SMe)]2+ is successfully transferred to the core-shell gold-coated Fe3O4 magnetic nanoparticles. To the best of our knowledge, this is the first study reporting nuclease activity due to the reactive oxygen species generated by a copper complex immobilized on a gold-coated magnetic nanoparticle.

A simple electrochemical method to monitor an azo dye reaction with a liver protein.

Disperse Orange 37 (DO37) is an efficient azo dye for dyeing synthetic textile materials owing to its resistance to degradation that may also be harmful to humans as DO37 is not entirely eliminated in wastewater treatment. In this paper, we demonstrate that DO37 is bleached by reduced glutathione (GSH) in a reaction catalyzed by glutathione-s-transferase (GST), a phase II detoxification enzyme. The reaction included a nucleophilic attack involving sulfhydryl groups, confirmed using density functional theory (DFT) calculations. DO37 also induced quenching in the fluorescence of GST through static suppression. The reaction was determined using differential pulse voltammetry (DPV) by monitoring the oxidation peak at 0.65 V of GSH sulfhydryl group. Quantitative estimation of the product reaction could be made by measuring an additional oxidation peak at 0.91 V which increased linearly with DO37 concentration. These electrochemical determinations were made possible by preconcentrating the reaction product on a graphite-epoxy electrode with immobilization of GST onto magnetite nanoparticles. Straightforward biological implications from the results are associated with the known toxicity of azo dyes such as DO37, which has been proven here to interact strongly with both GSH and the liver enzyme GST, and may induce hepatocarcinogenesis or other types of cancer.

Magnetic nanohydrogel obtained by miniemulsion polymerization of poly(acrylic acid) grafted onto derivatized dextran.

This study describes the synthesis of magnetic nanohydrogels by miniemulsion polymerization technique. Dextran was derivatized by the glycidyl methacrylate to anchor vinyl groups on polysaccharides backbone, allowing its use as a macromonomer for miniemulsion polymerization, as confirmed by proton nuclear magnetic resonance spectroscopy (13C NMR). Magnetite nanoparticles were synthesized by coprecipitation, followed by air oxidation to maghemite. The results of X-ray diffractometry (XRD), Raman and transmission electron microscopy (TEM) analysis showed that maghemite nanoparticles were obtained with a diameter of 5.27nm. The entrapment of iron oxide nanoparticles in a dextran nanohydrogel matrix was confirmed by thermogravimetric analysis (TGA), scanning transmission electron microscopy (STEM) and Zeta potential data. The magnetic nanohydrogels presented superparamagnetic behavior and were colloidal stable in physiological during 30days. Our findings suggest that the synthesized magnetic nanohydrogel are potential candidates for use in drug delivery systems due to its physicochemical and magnetic properties.

pH-responsive poly(aspartic acid) hydrogel-coated magnetite nanoparticles for biomedical applications.

A novel multifunctional nanosystem formed by magnetite nanoparticles coated with pH-responsive poly(aspartic acid) hydrogel was developed. Magnetite nanoparticles (Fe3O4) have been intensively investigated for biomedical applications due to their magnetic properties and dimensions similar to the biostructures. Poly(aspartic acid) is a water-soluble, biodegradable and biocompatible polymer, which features makes it a potential candidate for biomedical applications. The nanoparticles surface modification was carried out by crosslinking polysuccinimide on the magnetite nanoparticles surface and hydrolyzing the succinimide units in mild alkaline medium to obtain the magnetic poly(aspartic acid) hydrogel. The surface modification in each step was confirmed by DRIFTS, TEM and zeta potential measurements. The hydrodynamic diameter of the nanosystems decreases as the pH value decreases. The nanosystems showed high colloidal stability in water and no cytotoxicity was detected, which make these nanosystems suitable for biomedical applications.

Rhamnolipid emulsifying activity and emulsion stability: pH rules.

Rhamnolipids have excellent emulsifying power with a variety of hydrocarbons, aromatic compounds and vegetable oils. This paper evaluates the effect of pH ranging from 3 to 9 on the emulsifying activity and stability of rhamnolipids and hydrophobic substrates (benzene, soybean oil and kerosene). Sodium dodecyl sulfate was used as a reference to compare the level of chemical and biological surfactant activity after 24 h (E(24)). The results indicate that pH exerts an influence over emulsion formation and stability. For rhamnolipids, peak emulsifying activity occurred under base conditions for all substrates, with the highest value achieved with kerosene at pH 8. The results of the present study demonstrate that rhamnolipids could replace chemical surfactants, such as SDS, in different industrial fields.

Self-assembled FePt nanocrystals with large coercivity: reduction of the fcc-to-L1(0) ordering temperature.

Herein we report the synthesis and properties of Fe(55)Pt(45) nanoparticles, both monodisperse and self-assembled into hexagonal close-packed and cubic arrays of 4.0 +/- 0.2 nm size in an L1(0) structure, obtained by a modified polyol process. The new synthetic route improved the control over the particle composition, thereby reducing the temperature required to convert from face-centered cubic (fcc) to face-centered tetragonal (fct) phase by some 30-50 degrees C without additives. Annealing at 550 degrees C for 30 min converts the self-assembled nanoparticles into ferromagnetic nanocrystals with large coercivity, H(C) = 11.1 kOe. Reducing the fcc-to-fct (L1(0)) ordering temperature avoided particle coalescence and decreased the loss in particle positional order without compromising the magnetic properties, as is generally observed when additives are used.

Effects of organic and inorganic additives on flotation recovery of washed cells of Saccharomyces cerevisiae resuspended in water.

Separation of microbial cells by flotation recovery is usually carried out in industrial reactors or wastewater treatment systems, which contain a complex mixture of microbial nutrients and excretion products. In the present study, the separation of yeast cells by flotation recovery was carried out using a simple flotation recovery systems containing washed yeast cells resuspended in water in order to elucidate the effects of additives (defined amounts of organic and inorganic acids, ethanol, surfactants and sodium chloride) on the cellular interactions at interfaces (cell/aqueous phase and cell/air bubble). When sodium chloride, organic acids (notably propionic, succinic and acetic acids) and organic surfactants (sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromide (CTAB) and Nonidet P40) were added to the flotation recovery system, significant increases in the cell recovery of yeast hydrophobic cells (Saccharomyces cerevisiae, strain FLT-01) were observed. The association of ethanol to acetic acid solution (a minor by-product of alcoholic fermentation) in the flotation recovery system, containing washed cells of strain FLT-01 resuspended in water, leading to an increased flotation recovery at pH 5.5. Thus, the association among products of the cellular metabolism (e.g., ethanol and acetic acid) can improve yeast cell recovery by flotation recovery.