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.
In this study, we report a green one-pot synthesis method that uses
extract as a reducing and capping agent, to produce Ag-NPs with applications as therapeutic agents to treat infections in vivo.
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.
We show that Ag-NPs are spherical with a narrow size distribution. The Ag-NPs show antimicrobial activities in vitro against Gram-negative (
,
, and a clinical multidrug-resistant strain of
) and Gram-positive (
) bacteria. Moreover, antimicrobial effects of the Ag-NPs, against a resistant
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.
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.
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.
In this work, we use an exopolysaccharide, from
UANL-001L, an autochthonous strain from the Mexican northeast, as a capping agent in the synthesis of Zn, and Ni, nanoparticle biopolymer biocomposites.
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
, and a Gram-negative
. Antimicrobial activity was determined using a microdilution assay whereas antibiofilm activity was analyzed through crystal violet staining.
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
and
at 3 and 2 mg/mL, respectively. Moreover, Zn-EPS biocomposites showed antimicrobial activity against resistant
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.
The exopolysaccharide produced by
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.
In this study, UiO-67 (Zr)/g-C3N4 composites (U67N) were synthesized at wt.% ratios of 05:95, 15:85, and 30:70 using the solvothermal method at 80 °C for 24 h followed by calcination at 350 °C. The ...composites were characterized using UV–Vis diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray spectroscopy, transmission electron microscopy, and nitrogen physisorption analysis. In addition, thermal stability analysis of UiO-67 was conducted using thermogravimetric analysis.
The photocatalytic performance of the composites was assessed during the degradation and mineralization of a mixture of methylparaben (MeP) and propylparaben (PrP) under simulated sunlight. The adsorption process of U67N 15:85 was characterized through kinetic studies and adsorption capacity experiments, which were modeled using pseudo-first-order and pseudo-second-order kinetics and Langmuir and Freundlich isotherms, respectively.
The influence of pH levels 3, 5, and 7 on the photocatalytic degradation of the mixture was investigated, revealing enhanced degradation and mineralization at pH 3. The U67N composite exhibited dual capability in removing contaminants through adsorption and photocatalytic processes. Among the prepared composites, U67N 15:85 demonstrated the highest photocatalytic activity, achieving removal efficiencies of 96.8% for MeP, 92.5% for PrP, and 45.7% for total organic carbon in 300 kJ/m2 accumulated energy (3 h of reaction time). The detoxification of the effluent was confirmed through acute toxicity evaluation using the Vibrio fischeri method.
The oxidation mechanism of the heterojunction formed between UiO-67 (Zr) and g-C3N4 was proposed based on PL analysis, photoelectrochemistry studies (including photocurrent response, Nyquist, and Mott–Schottky analyses), and scavenger assays.
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•UiO-67(Zr)/g-C3N4 showed dual capacity to remove parabens by adsorption and photocatalysis decreasing effluent toxicity.•U67N 15:85 reached the highest photocatalytic response in the degradation and mineralization of the MeP and PrP at pH 3.•Coupling UiO-67(Zr) into g-C3N4 improved activity by delaying recombination and promoting charge separation and migration.•The proposed band scheme suggests that O2•- radicals are primarily involved in parabens oxidation.
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 (AgNO
=5 mM) exhibit an ultrafine size and a narrow size distribution, whereas particles synthesized with high concentrations of the precursor Ag salt (AgNO
=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 ligands.
•GO thermal behavior is analyzed in real time by microscopy techniques.•In-situ heating experiments are performed in the transmission electron microscope by using a MEMS-Chip system and a heating ...holder.•Conversion of selected area electron diffraction (SAED) patterns into linear profiles as a different manner to interpret SAED results.•SAED linear profiles are significantly similar to an X-ray diffractogram.
Reduced graphene oxide (rGO) can be obtained by thermal treatment of graphene oxide (GO), whereby most of the oxygen-containing groups are removed, partially re-generating the original structure of graphene. Experimental observation of in-situ reduction heating of GO was carried out using a Transmission Electron Microscope (TEM) equipped with a heating-chip. This investigation contributes to the understanding of the thermal behavior of GO as the reduction proceeds upon heating the material. By acquiring Selected Area Electron Diffraction patterns (SAED) at different temperatures, two diffuse rings (R2 and R3) were observed at 25 °C with an interplanar distance (d) of 2.0977 and 1.201, respectively. A third ring (R1), with a d = 3.8189 Å, appears at 120 °C reaching a d = 3.3939 Å at 1200 °C, indicating the crystalline reordering of the material. The SAED patterns were interpreted by calculating the linear profiles, revealing information about the reduction of GO that is difficult to observe through SAED. The method reliability was proved by comparing the results as a function of the reciprocal space (1/nm) and 2θ. High resolution images revealed the reordering of the graphitic hexagonal structure that took place upon in-situ heating of GO to 1200 °C, temperature at which the d = 3.3961 Å was achieved.
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Uniform magnetic nanoneedles have been prepared by hydrogen reduction of elongated nanoarchitectures. These precursors are as-prepared or cobalt-coated aggregates of highly oriented haematite ...nanocrystals (∼5 nm). The final materials are flattened nanoneedles formed by chains of assembled Fe or FeCo single-domain nanocrystals. The microstructural properties of such nanoneedles were tailored using renewed and improved synthetic strategies. In this fashion, the needle elongation and composition, the crystallite size (from 15 up to 30 nm), the nanocrystal orientation (with the 〈110〉 or 〈001〉 directions roughly along the long axis of the nanoneedle) and their type of arrangement (single chains, frustrated double chains and double chains) were controlled by modifying the reduction time, the axial ratio of the precursor haematite and the presence of additional coatings of aluminum or yttrium compounds. The values of the coercivity HC found for these nanoneedles are compared with the values predicted by the chain of spheres model assuming a symmetric fanning mechanism for magnetization reversal.
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.
Las nanopartículas de hidroxiapatita (nHAp) tienen el potencial de estimular el crecimiento de plantas y actuar como nanofertilizante. El objetivo de este bioensayo fue evaluar el efecto de la nHAp ...sobre la germinaci.n de semillas y algunos aspectos fisiol.gicos de plantulas de pepino (Cucumis sativus L). Los tratamientos consistieron en dosis crecientes de nHAp (0, 25, 50, 100, 200, 500, 1000 y 2000 mg L−1. La utilizacion de la nHAp causo efectos significativos para las variables longitud de pl.mula y biomasa seca. La longitud de rad.cula, germinaci´óny vigor fue favorecida con la concentracion de 25 mg L−1; mientras que con 200 mg L−1 se detect. una inhibici.n. La diferencias detectadas se atribuyen a la atracci.n electrost.tica entre nanopart.culas, al observarse que concentraciones superiores a 200 mg L−1 se aglomeraron formando micropart.culas, lo que limita su absorci.n por la planta por las barreras de las paredes y membranas celulares.
Nanoparticles of hydroxyapatite (nHAp) have the poten-tial to stimulate plant growth and act as a nanofertilizer. The objective ofthis bioassay was to evaluate the effect of nHAp on seed germination ...andsome physiological aspects of cucumber (Cucumis sativusL) seedlings.The treatments consisted of increasing doses of nHAp (0, 25, 50, 100, 100,200, 500, 1000 and 2000 mg L−1). The use of nHAp caused significanteffects on plumule length and dry biomass. Radicle length, germination,and vigor were favored at 25 mg L−1, while at 200 mg L−1, an inhibitionwas detected. The inhibitory effect is attributed to the electrostatic attractionbetween nanoparticles, since at concentrations higher than 200 mg L−1they agglomerated to form microparticles, which limits their absorption bythe plant through the barriers of the cell walls and membranes.
Las nanopartículas de hidroxiapatita (nHAp) tienen el potencialde estimular el crecimiento de plantas y actuar como nanofertilizante.El objetivo de este bioensayo fue evaluar el efecto de la nHAp sobrela germinación de semillas y algunos aspectos fisiológicos de plantulasde pepino (Cucumis sativusL). Los tratamientos consistieron en dosiscrecientes de nHAp (0, 25, 50, 100, 200, 500, 1000 y 2000 mg L−1.La utilizacion de la nHAp causo efectos significativos para las variableslongitud de plúmula y biomasa seca. La longitud de radícula, germinacióny vigor fue favorecida con la concentracion de 25 mg L−1; mientras quecon 200 mg L−1se detectó una inhibición. La diferencias detectadas seatribuyen a la atracción electrostática entre nanopartículas, al observarseque concentraciones superiores a 200 mg L−1se aglomeraron formandomicropartículas, lo que limita su absorción por la planta por las barreras delas paredes y membranas celulares.
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