We have synthesized silver nanoparticles from silver nitrate solutions using extracts of Rumex hymenosepalus, a plant widely found in a large region in North America, as reducing agent. This plant is known to be rich in antioxidant molecules which we use as reducing agents. Silver nanoparticles grow in a single-step method, at room temperature, and with no addition of external energy. The nanoparticles have been characterized by ultraviolet-visible spectroscopy and transmission electron microscopy, as a function of the ratio of silver ions to reducing agent molecules. The nanoparticle diameters are in the range of 2 to 40 nm. High-resolution transmission electron microscopy and fast Fourier transform analysis show that two kinds of crystal structures are obtained: face-centered cubic and hexagonal.

Synthesis of gold nanoparticles (AuNPs) with plant extracts has gained great interest in the field of biomedicine due to its wide variety of health applications. In the present work, AuNPs were synthesized with Mimosa tenuiflora (Mt) bark extract at different metallic precursor concentrations. Mt extract was obtained by mixing the tree bark in ethanol-water. The antioxidant capacity of extract was evaluated using 2,2-diphenyl-1-picrylhydrazyl and total polyphenol assay. AuNPs were characterized by transmission electron microscopy, X-ray diffraction, UV-Vis and Fourier transform infrared spectroscopy, and X-ray photoelectron spectrometry for functional group determination onto their surface. AuMt (colloids formed by AuNPs and molecules of Mt) exhibit multiple shapes with sizes between 20 and 200 nm. AuMt were tested on methylene blue degradation in homogeneous catalysis adding sodium borohydride. The smallest NPs (AuMt1) have a degradation coefficient of 0.008/s and reach 50% degradation in 190s. Cell viability and cytotoxicity were evaluated in human umbilical vein endothelial cells (HUVEC), and a moderate cytotoxic effect at 24 and 48 h was found. However, toxicity does not behave in a dose-dependent manner. Cellular internalization of AuMt on HUVEC cells was analyzed by confocal laser scanning microscopy. For AuMt1, it can be observed that the material is dispersed into the cytoplasm, while in AuMt2, the material is concentrated in the nuclear periphery.

In this work we use Mimosa tenuiflora (MtE) extracts as reducing agents to synthesize silver nanoparticles (AgMt NPs) which were characterized by DPPH and Total Polyphenols Assays, UV–visible, X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Thermogravimetric analysis (TGA). AgMt NPs possess average sizes of 21 nm and fcc crystalline structure, it was also confirmed that the MtE is present in the AgMt NPs even after the cleaning protocol applied. Subsequently, carbopol hydrogels were made and the MtE and the synthesized AgMt NPs were dispersed in different gels (MtE-G and AgMt NPs-G, respectively) at 100 µg/g concentration. The gels were characterized by UV–Vis, IR, and rheology. Antimicrobial tests were performed using Staphylococcus aureus and Escherichia coli. Burn wound healing was evaluated in a second-degree burn injury on a Wistar rats model for 14 days and additional skin biopsies were examined with histopathological analysis. Gel with commercial silver nanoparticles (Ag NPs) was prepared and employed as a control on the biological assays. Hydrogel system containing silver nanoparticles synthesized with Mimosa tenuiflora (AgMt NPs-G) is a promising therapeutic strategy for burn wound healing, this due to bactericidal and anti-inflammatory effects, which promotes a more effective recovery (in percentage terms) by damaged area.

In this work, we used a sequential method of synthesis for gold–silver bimetallic nanoparticles with core@shell structure (Au@AgNPs). Rumex hymenosepalus root extract (Rh), which presents high content in catechins and stilbenes, was used as reductor agent in nanoparticles synthesis. Size distribution obtained by Transmission Electron Microscopy (TEM) gives a mean diameter of 36 ± 11 nm for Au@AgNPs, 24 ± 4 nm for gold nanoparticles (AuNPs), and 13 ± 3 nm for silver nanoparticles (AgNPs). The geometrical shapes of NPs were principally quasi-spherical. The thickness of the silver shell over AuNPs is around 6 nm and covered by active biomolecules onto the surface. Nanoparticles characterization included high angle annular dark field images (HAADF) recorded with a scanning transmission electron microscope (STEM), Energy-Dispersive X-ray Spectroscopy (EDS), X-Ray Diffraction (XRD), UV–Vis Spectroscopy, Zeta Potential, and Dynamic Light Scattering (DLS). Fourier Transform Infrared Spectrometer (FTIR), and X-ray Photoelectron Spectroscopy (XPS) show that nanoparticles are stabilized by extract molecules. A growth kinetics study was performed using the Gompertz model for microorganisms exposed to nanomaterials. The results indicate that AgNPs and Au@AgNPs affect the lag phase and growth rate of Escherichia coli and Candida albicans in a dose-dependent manner, with a better response for Au@AgNPs

We synthesized silver nanoparticles using Rumex hymenosepalus root extract (Rh). Nanoparticles were subjected to a purification process and final product is a composite of Rh and silver nanoparticles (AgNPsC). Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to perform a microstructure study. Additionally, two fractions (RhA and RhB) were obtained from the original extract by filtration with tetrahydrofuran (THF); both fractions were analyzed using UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and 2,2-diphenyl-1-picrylhydrazyl (DPPH); total polyphenol content was also determined. Separate inhibition tests for AgNPsC and RhA and RhB were applied to Gram-positive bacteria, Gram-negative bacteria, and yeast (Candida albicans) using the well diffusion method. Extract fractions were found to have inhibitory effects only over Gram-positive bacteria, and silver nanoparticles showed inhibitory effects over all the evaluated microorganisms. Cytotoxicity was evaluated using the tetrazolium dye (MTT) assay in mononuclear peripheral blood cells. In addition, we assessment AgNPsC in THP-1 monocyte cell line, using the cell viability estimation by trypan blue dye exclusion test (TB) and Live/Dead (LD) cell viability assays by confocal microscopy.

Early Mortality Syndrome (EMS) or Acute Hepatopancreatic Necrosis Syndrome (AHPNS) is a disease produced by gram-negative bacteria Vibrio parahaemolyticus (V. parahaemolyticus), which has caused declines in worldwide production of a white shrimp Litopenaeus vannamei (L. vannamei). In this work, we propose the implementation of silver nanoparticles (AgNPs) synthesized with Rumex hymenosepalus (Rh) extract as an alternative on V. parahaemolyticus control. AgNPs were characterized by UV-Vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). AgNP mean sizes by DLS were 80.82±1.16 nm and sizes between 2 and 10 nm by TEM, with a zeta potential of −47.72±1.05 mV. This study evaluated AgNPs and Rh antimicrobial capacity on V. parahaemolyticus at different concentrations; the minimum inhibitory concentration (MIC) found was 25 μg/mL for AgNPs and 220 μg/mL for Rh. Additionally, were carried out time-kill curves and reactive oxygen species (ROS) generation for 1 and 4 MIC. Both concentrations (MIC) were tested for toxicity on Artemia nauplii from Artemia franciscana (A. franciscana), because nauplii were used as biocarriers for AgNPs and Rh extract on L. vannamei. Once the shrimp were treated, they were challenged with Vibrio infection and it was found that those who were treated with both agents showed greater survival than the control. V. parahaemolyticus and postlarval samples were taken from the bioassay and fixed and prepared for TEM and SEM in order to search NPs in internal structure of bacteria and the hepatopancreatic area of shrimps; AgNPs were detected in both cases. AgNPs and Rh extract show antibacterial properties on the infected shrimp with V. parahaemolyticus. The action mechanisms are interaction with the bacterial membrane and ROS generation; these effects are produced by both agents.

We have synthesized silver nanoparticles in the non-polar phase of non-aqueous microemulsions. The nanocrystals have been grown by reducing silver ions in the microemulsion cylindrical micelles formed by the reducing agent (ethylene glycol). By a careful deposit of the microemulsion phase on a substrate, the micelles align in a hexagonal geometry, thus forming a 2D array of parallel strings of individual silver nanoparticles on the substrate. The microemulsions are the ternary system of anionic surfactant, non-polar solvent (isooctane), and solvent polar (ethylene glycol); the size of synthesized nanoparticles is about 7 nm and they are monodisperse. The study of the microstructure was realized by transmission electron microscopy, high-resolution technique transmission electron microscopy (HR-TEM), and Fourier processing using the software Digital Micrograph for the determination of the crystalline structure of the HR-TEM images of the nanocrystals; chemical composition was determined using the energy-dispersive X-ray spectroscopy. Addition technique polarizing light microscopy allowed the observation of the hexagonal phase of the system. This method of synthesis and self-alignment could be useful for the preparation of patterned materials at the nanometer scale.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-0804-8) contains supplementary material, which is available to authorized users.

A green method for synthesizing gold nanoparticles is proposed using hydroethanolic extract of Vitex mollis fruit (Vm extract) as a reducer and stabilizer. The formation of gold nanoparticles synthesized with Vm extract (AuVmNPs) was monitored by measuring the ultraviolet–visible spectra. The morphology and crystalline phase were determined using scanning electron microscopy, X-ray diffraction, and high-resolution transmission electron microscopy. Synthesized nanoparticles were generally spherical, and the size distribution obtained by transmission electron microscopy shows two populations with mean sizes of 12.5 and 22.5 nm. Cell viability assay using MTT and cellular apoptosis studies using annexin V on human umbilical vein endothelial cells (HUVECs) and the human mammary epithelial cell line (MCF10A) indicate that AuVmNPs have low toxicity. Cell migration tests indicate that AuVmNPs significantly inhibit HUVEC cell migration in a dose-dependent manner. The evaluation of the localization of AuVmNPs in HUVECs using confocal laser scanning microscopy indicates that nanoparticles penetrate cells and are found in the cytosol without preferential distribution and without entering the nucleus. The inhibitory effect on cellular migration and low toxicity suggest AuVmNPs as appropriate candidates in future studies of antiangiogenic activity.