Microstructural, spectroscopic, and antibacterial properties of silver-based hybrid nanostructures biosynthesized using extracts of coriander leaves and seeds

Coriander leaves and seeds have been highly appreciated since ancient times, not only due to their pleasant flavors but also due to their inhibitory activity on food degradation and their beneficial properties for health, both ascribed to their strong antioxidant activity. Recently, it has been shown that coriander leaf extracts can mediate the synthesis of metallic nanoparticles through oxidation/reduction reactions. In the present study, extracts of coriander leaves and seeds have been used as reaction media for the wet chemical synthesis of ultrafine silver nanoparticles and nanoparticle clusters, with urchin- and tree-like shapes, coated by biomolecules (mainly, proteins and polyphenols). In this greener route of nanostructure preparation, the active biocompounds of coriander simultaneously play the roles of reducing and stabilizing agents. The morphological and microstructural studies of the resulting biosynthesized silver nanostructures revealed that the nanostructures prepared with a small concentration of the precursor Ag salt (AgNO3 =5 mM) exhibit an ultrafine size and a narrow size distribution, whereas particles synthesized with high concentrations of the precursor Ag salt (AgNO3 =0.5 M) are polydisperse and formation of supramolecular structures occurs. Fourier transform infrared and Raman spectroscopy studies indicated that the bioreduction of the Ag- ions takes place through their interactions with free amines, carboxylate ions, and hydroxyl groups. As a consequence of such interactions, residues of proteins and polyphenols cap the biosynthesized Ag nanoparticles providing them a hybrid core/shell structure. In addition, these biosynthesized Ag nanomaterials exhibited size-dependent plasmon extinction bands and enhanced bactericidal activities against both Gram-positive and Gram-negative bacteria, displaying minimal inhibitory Ag concentrations lower than typical values reported in the literature for Ag nanoparticles, probably due to the synergy of the bactericidal activities of the Ag nanoparticle cores and their capping ligandsSEP CB12-17948

Pseudo-monocrystalline properties of cylindrical nanowires confinedly grown by electrodeposition in nanoporous alumina templates

Four different cylindrical nanowire systems (nickel, cobalt, Co23Cu77, and multisegmented Co58Ni42/Co83Ni17 nanowires) with single-crystal-like properties were characterized by transmission electron microscopy and selected-area electron diffraction (SAED) under different tilting angles. Although these nanowires have different chemical compositions, crystalline structures and/or diameters, they exhibit similar behaviors, which are unexpected for ideal single-crystals. All the samples presented SAED patterns that did not experience changes from one zone axis to another when the nanowire was tilted in a wide range of angles, exhibiting related apparent interplanar distances that are dependent on the nanowire inclination, yielding deformed patterns that can be unrecognizable. Moreover, face-centered cubic nanowires presented classically forbidden reflections. These behaviors were explained by considering the characteristics of the measurement technique and the confined template-assisted growth, which force the atoms to be accommodated in a cylindrical volume with nanoscale dimensions, yielding the frustrated formation of stable facets and right angles in the nanowire radial directions, together with the formation of stacking faults

In vivo antimicrobial activity of silver nanoparticles produced via a green chemistry synthesis using Acacia rigidula as a reducing and capping agent

Introduction: One of the main issues in the medical field and clinical practice is the development of novel and effective treatments against infections caused by antibiotic-resistant bacteria. One avenue that has been approached to develop effective antimicrobials is the use of silver nanoparticles (Ag-NPs), since they have been found to exhibit an efficient and wide spectrum of antimicrobial properties. Among the main drawbacks of using Ag-NPs are their potential cytotoxicity against eukaryotic cells and the latent environmental toxicity of their synthesis methods. Therefore, diverse green synthesis methods, which involve the use of environmentally friendly plant extracts as reductive and capping agents, have become attractive to synthesize Ag-NPs that exhibit antimicrobial effects against resistant bacteria at concentrations below toxicity thresholds for eukaryotic cells. Purpose: In this study, we report a green one-pot synthesis method that uses Acacia rigidula extract as a reducing and capping agent, to produce Ag-NPs with applications as therapeutic agents to treat infections in vivo. Materials and methods: The Ag-NPs were characterized using transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction, energy-dispersive spectroscopy, ultraviolet–visible, and Fourier transform infrared. Results: We show that Ag-NPs are spherical with a narrow size distribution. The Ag-NPs show antimicrobial activities in vitro against Gram-negative (Escherichia coli, Pseudomonas aeruginosa, and a clinical multidrug-resistant strain of P. aeruginosa) and Gram-positive (Bacillus subtilis) bacteria. Moreover, antimicrobial effects of the Ag-NPs, against a resistant P. aeruginosa clinical strain, were tested in a murine skin infection model. The results demonstrate that the Ag-NPs reported in this work are capable of eradicating pathogenic resistant bacteria in an infection in vivo. In addition, skin, liver, and kidney damage profiles were monitored in the murine infection model, and the results demonstrate that Ag-NPs can be used safely as therapeutic agents in animal models. Conclusion: Together, these results suggest the potential use of Ag-NPs, synthesized by green chemistry methods, as therapeutic agents against infections caused by resistant and nonresistant strains. Keywords: silver nanoparticles, green synthesis, in vitro antibacterial activity, in vivo antibacterial activity, skin infection, toxicological stud

Síntesis y caracterización de nanoalambres con composiciones y propiedades microestructurales y magnéticas diseñadas.

Tesis (Doctor en Ciencias en Ingeniería Física Industrial) UANL, 2014.UANLhttp://www.uanl.mx

Synthesis and magnetic properties of iron nanoellipsoids bioinspired by magnetotactic bacteria

Ferromagnetic iron nanoellipsoids were prepared by the hydrogen reduction of ellipsoidal hematite nanoarchitectures. These magnetic nanoscale particles displayed a microstructure that showed clear similarities to the magnetosome chains of the magnetotactic bacteria. Specifically, such nanoellipsoids are formed by single-domain nanocrystals assembled into double chains sharing the same crystallographic orientation. In the present contribution, the magnetic properties of the Fe nanoellipsoids were explained considering the chain of spheres model of Jacobs and Bean, and thermal effects

Synthesis of copper oxides-graphene composites for glucose sensing

A multi-gram preparation of graphene nanoplatelets decorated with CuO leaf-like structures and Cu2O nanocubes can be accomplished with ease from graphite using an environmentally friendly method. The composites' synthesis is conveniently achieved within an hour through a high shear mixing pre-treatment of the graphite in water, followed by the addition of copper salts to the resulting slurry and their subsequent conversion to cupric or cuprous oxide-few layer graphite composites of varying weight ratios. The materials, characterized by XRD, Raman, SEM, TEM, and TGA exhibit good electrochemical glucose oxidation sensing capacity. Cyclic voltammetry of modified glassy carbon electrodes prepared with a 1:0.2 weight ratio of graphene nanoplatelets to CuO or Cu2O composites shows low detection limits of 0.25 μM (S/N = 3) for glucose and high sensitivities of 845 and 1,108 μA cm–2 mM–1, respectively. The sensors also show exceptionally low current response to the commonly found interferents such as uric acid, dopamine, and ascorbic acid. The materials' ease of manufacturing and good sensing capabilities suggests their potential use in determining glucose contents in biological samples and industrial applications

Antimicrobial and antibiofilm activity of biopolymer-Ni, Zn nanoparticle biocomposites synthesized using R. mucilaginosa UANL-001L exopolysaccharide as a capping agent

Introduction: Global increase in the consumption of antibiotics has induced selective stress on wild-type microorganisms, pushing them to adapt to conditions of higher antibiotic concentrations, and thus an increased variety of resistant bacterial strains have emerged. Metal nanoparticles synthesized by green methods have been studied and proposed as potential antimicrobial agents against both wild-type and antibiotic-resistant strains; in addition, exopolysaccharides have been used as capping agent of metal nanoparticles due to their biocompatibility, reducing biological risks in a wide variety of applications.Purpose: In this work, we use an exopolysaccharide, from Rhodotorula mucilaginosa UANL-001L, an autochthonous strain from the Mexican northeast, as a capping agent in the synthesis of Zn, and Ni, nanoparticle biopolymer biocomposites.Materials and methods: To physically and chemically characterize the synthesized biocomposites, FT-IR, UV-Vs, TEM, SAED and EDS analysis were carried out. Antimicrobial and antibiofilm biological activity were tested for the biocomposites against two resistant clinical strains, a Gram-positive Staphylococcus aureus, and a Gram-negative Pseudomonas aeruginosa. Antimicrobial activity was determined using a microdilution assay whereas antibiofilm activity was analyzed through crystal violet staining.Results: Biocomposites composed of exopolysaccharide capped Zn and Ni metal nanoparticles were synthesized through a green synthesis methodology. The average size of the Zn and Ni nanoparticles ranged between 8 and 26 nm, respectively. The Ni-EPS biocomposites showed antimicrobial and antibiofilm activity against resistant strains of Staphylococcus aureus and Pseudomonas aeruginosa at 3 and 2 mg/mL, respectively. Moreover, Zn-EPS biocomposites showed antimicrobial activity against resistant Staphylococcus aureus at 1 mg/mL. Both biocomposites showed no toxicity, as renal function showed no differences between treatments and control in the in vivo assays with male rats tests in this study at a concentration of 24 mg/kg of body weight. Conclusion: The exopolysaccharide produced by Rhodotorula mucilaginosa UANL-001L is an excellent candidate as a capping agent in the synthesis of biopolymer-metal nanoparticle biocomposites. Both Ni and Zn-EPS biocomposites demonstrate to be potential contenders as novel antimicrobial agents against both Gram-negative and Gram-positive clinically relevant resistant bacterial strains. Moreover, Ni-EPS biocomposites also showed antibiofilm activity, which makes them an interesting material to be used in different applications to counterattack global health problems due to the emergence of resistant microorganisms

Synthesis of Copper Nanoparticles Stabilized with Organic Ligands and Their Antimicrobial Properties

In this work, we report the synthesis of copper nanoparticles (Cu NPs), employing the chemical reduction method in an aqueous medium. We used copper sulfate pentahydrate (CuSO4·5H2O) as a metallic precursor; polyethylenimine (PEI), allylamine (AAM), and 4-aminobutyric acid (AABT) as stabilizing agents; and hydrated hydrazine as a reducing agent. The characterization of the obtained nanoparticles consisted of X-ray, TEM, FTIR, and TGA analyses. Through these techniques, it was possible to detect the presence of the used stabilizing agents on the surface of the NPs. Finally, a zeta potential analysis was performed to differentiate the stability of the nanoparticles with a different type of stabilizing agent, from which it was determined that the most stable nanoparticles were the Cu NPs synthesized in the presence of the PEI/AAM mixture. The antimicrobial activity of Cu/PEI/AABT toward P. aeruginosa and S. aureus bacteria was high, inhibiting both bacteria with low contact times and copper concentrations of 50–200 ppm. The synthesis method allowed us to obtain Cu NPs free of oxides, stable to oxidation, and with high yields. The newly functionalized Cu NPs are potential candidates for antimicrobial applications

Electroplating and magnetostructural characterization of multisegmented Co54

Highly hexagonally ordered hard anodic aluminum oxide membranes, which have been modified by a thin cover layer of SiO2 deposited by atomic layer deposition method, were used as templates for the synthesis of electrodeposited magnetic Co-Ni nanowire arrays having diameters of around 180 to 200 nm and made of tens of segments with alternating compositions of Co54Ni46 and Co85Ni15. Each Co-Ni single segment has a mean length of around 290 nm for the Co54Ni46 alloy, whereas the length of the Co85Ni15 segments was around 430 nm. The composition and crystalline structure of each Co-Ni nanowire segment were determined by transmission electron microscopy and selected area electron diffraction techniques. The employed single-bath electrochemical nanowire growth method allows for tuning both the composition and crystalline structure of each individual Co-Ni segment. The room temperature magnetic behavior of the multisegmented Co-Ni nanowire arrays is also studied and correlated with their structural and morphological properties