Yeast-derived biosynthesis of silver/silver chloride nanoparticles and their antiproliferative activity against bacteria

Here, we provide the first evidence of yeast strains assisted Ag/AgCl-NPs production in vitro. The formed nanoparticles were characterized by spectroscopic and electron microscopy approaches. UV-vis supported the biosynthesis. TEM analysis evidenced that the nanoparticles mainly presented a circular shape and their diameters varied mostly being in the range 2 to 10 nm. XRD analysis showed a crystalline structure, with diffraction peaks corresponding to metallic silver and silver chloride nanoparticles, and when analyzed by high-resolution transmission electron microscopy (HRTEM), instead of being round, (111) (octahedral) and (200) (cubic) symmetry facets appeared systematically in one side of the nanoparticles. Analysis of ultra-thin sections by TEM indicated that the domain of the synthesis of Ag/AgCl-NPs was mainly between the cell wall and the plasma membrane. By using 3D reconstruction obtained from focused ion beam scanning electron microscopy (FIB/SEM) the spatial distribution of the domains of nanoparticle synthesis was mapped and nanoaggregates of Ag/AgCl-NPs up 35 nm in diameter were observed. Extracellular synthesis also occurred; in accordance with the fact that conditioned media from yeast isolates were as efficient at producing Ag/AgCl-NPs as live-cell cultures. Exposure of Gram-positive Staphylococcus aureus and Gram-negative Klebsiella pneumoniae cultures to Ag/AgCl-NPs led to a strong growth inhibition as shown by optical density measurements. The Ag/AgCl-NPs described here have characteristics compatible with a strong potential for use in the biotechnology industry, particularly for biomedical applications

Enhanced antibacterial activity of streptomycin against some human pathogens using green synthesized silver nanoparticles

AbstractThe development of eco-friendly technologies in nanoparticle synthesis is of utmost importance in order to expand their biological horizons. In the present study, bioreduction of AgNO3 into AgNPs using various leaf extracts of Ficus virens is explained. The resulting AgNPs were characterized by UV–vis spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Synthesis of AgNPs was confirmed by color change from transparent to brown with maximum absorption at 420 nm due to surface plasmon resonance of AgNPs. X-ray diffraction studies showed that the biosynthesized AgNPs were crystalline in nature, and TEM analysis showed spherical shape of the nanoparticles with size ranging from 4.98 to 29 nm. FTIR study indicates that mainly –C = O, -OH and N-H groups in leaf extracts are involved in the reduction of Ag+ ions to Ag atoms, and proteins are responsible for stabilizing the silver nanoparticles. The synthesized AgNPs showed significant antibacterial activity against Gram positive and gram negative human bacterial pathogens. The results showed that AgNPs also synergistically enhance (2.02–57.98%) the antibacterial activity of streptomycin, a common antibiotic. With this approach, AgNPs can be used as a new generation of antimicrobial agents for successful development of drug delivery

Antimicrobial activity of cream incorporated with silver nanoparticles biosynthesized from Withania somnifera

We report on the antimicrobial activity of a cream formulation of silver nanoparticles (AgNPs), biosynthesized using Withania somnifera extract. Aqueous extracts of leaves promoted efficient green synthesis of AgNPs compared to fruits and root extracts of W. somnifera. Biosynthesized AgNPs were characterized for their size and shape by physical-chemical techniques such as UV-visible spectroscopy, laser Doppler anemometry, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, and X-ray energy dispersive spectroscopy. After confirming the antimicrobial potential of AgNPs, they were incorporated into a cream. Cream formulations of AgNPs and AgNO3 were prepared and compared for their antimicrobial activity against human pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Proteus vulgaris, Escherichia coli, and Candida albicans) and a plant pathogen (Agrobacterium tumefaciens). Our results show that AgNP creams possess significantly higher antimicrobial activity against the tested organisms.This work was supported by Fundacao para a Ciencia e Tecnologia (FCT), projects (PTDC/AGR-ALI/105169/2008 and PTDC/AGR-GPL/119211/2010). Gregory Marslin is supported by a FCT PhD fellowship (SFRH/BD/72809/2010).info:eu-repo/semantics/publishedVersio

Enhanced antibacterial activity of streptomycin against some human pathogens using green synthesized silver nanoparticles

The development of eco-friendly technologies in nanoparticle synthesis is of utmost importance in order to expand their biological horizons. In the present study, bioreduction of AgNO3 into AgNPs using various leaf extracts of Ficus virens is explained. The resulting AgNPs were characterized by UV-vis spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Synthesis of AgNPs was confirmed by color change from transparent to brown with maximum absorption at 420 nm due to surface plasmon resonance of AgNPs. X-ray diffraction studies showed that the biosynthesized AgNPs were crystalline in nature, and TEM analysis showed spherical shape of the nanoparticles with size ranging from 4.98 to 29 nm. FTIR study indicates that mainly -C = O, -OH and N-H groups in leaf extracts are involved in the reduction of Ag+ ions to Ag atoms, and proteins are responsible for stabilizing the silver nanoparticles. The synthesized AgNPs showed significant antibacterial activity against Gram positive and gram negative human bacterial pathogens. The results showed that AgNPs also synergistically enhance (2.02-57.98%) the antibacterial activity of streptomycin, a common antibiotic. With this approach, AgNPs can be used as a new generation of antimicrobial agents for successful development of drug delivery

Green synthesis of silver nanoparticles using Capsicum frutescence and its intensified activity against E. coli

The purpose of this study was to expand a trouble free biological method for the synthesis of silver nanoparticles using the fruit extract of Capsicum frutescence (Sweet pepper) to act as reducing and stabilizing agent. Water soluble organics played a vital role for the reduction silver ions into silver nanoparticles. The fruit extract was exposed to silver ions and the resultant biosynthesized silver nanoparticles characterized by UV-Vis spectrophotometry indicated the surface plasmon resonance band at 385- 435 nm. X-ray diffraction spectrum showed crystalline structure while scanning electron microscope analyses exposed the monodispersed distribution and particle size of 20-25 nm. The elemental analysis displayed strong signal at 3 keV that agrees to silver ions and confirms the presence of metallic silver. The antibacterial activity of silver nanoparticles was determined by agar well diffusion method against gram positive and gram negative bacteria. Maximum and minimum zones of inhibition were renowned against Escherichia coli (11.5 mm) and Bacillus subtilis (10.5 mm), respectively. This study exposed that silver nanoparticles retained good bactericidal activity at 80 μg/ml concentration

Biosynthesis and Characterization of Silver Nanoparticles by Aspergillus Species

Currently, researchers turn to natural processes such as using biological microorganisms in order to develop reliable and ecofriendly methods for the synthesis of metallic nanoparticles. In this study, we have investigated extracellular biosynthesis of silver nanoparticles using four Aspergillus species including A. fumigatus, A. clavatus, A. niger, and A. flavus. We have also analyzed nitrate reductase activity in the studied species in order to determine the probable role of this enzyme in the biosynthesis of silver nanoparticles. The formation of silver nanoparticles in the cell filtrates was confirmed by the passage of laser light, change in the color of cell filtrates, absorption peak at 430 nm in UV-Vis spectra, and atomic force microscopy (AFM). There was a logical relationship between the efficiencies of studied Aspergillus species in the production of silver nanoparticles and their nitrate reductase activity. A. fumigatus as the most efficient species showed the highest nitrate reductase activity among the studied species while A. flavus exhibited the lowest capacity in the biosynthesis of silver nanoparticles which was in accord with its low nitrate reductase activity. The present study showed that Aspergillus species had potential for the biosynthesis of silver nanoparticles depending on their nitrate reductase activity

Nanotoxicity for E. Coli and Characterization of Silver Quantum Dots Produced by Biosynthesis with Eichhornia crassipes

Nanomaterials are widely used in health and biomedical applications, however, only a few studies investigate their toxic effects. The present report signifies a contribution to the study of the toxic effects of silver nanoparticles on E. coli cells, which is a model organism of anthropogenic pollution. The toxicity of nanoparticles depends on their chemical and surface properties, shape and size. Nanoparticles that have the same chemical composition but different shapes or sizes might have different effects on cells. In this work, Ag nanoparticles were biosynthesized with an Eichhornia crassipes biomass, and it was demonstrated for the first time, that the amounts of hydrolysable tannins in this plant, are directly related to the size, shape, structure and composition of the Ag nanoparticles ; furthermore, the toxic effect was studied using E. coli cell culture. The EC was divided in three sections, i.e. roots, stems and leaves. Particle aggregation seems to be influenced by the amount of tannins present in the biomass. For each plant part, the amounts of hydrolysable tannins were determined, the highest amounts of these chemicals were present in the leaves, and hence these Ag nanoparticles dissolutions were used for the nanotoxicity experiments. . The cytotoxicity of Ag nanoparticles in a suspension was tested using the Ag nanoparticles synthesized with leaves, against Escherichia Coli ATCC 25992 where the concentration that inhibited 100% of bacterial growth, was 5 mg/L in contrast with a commercial solution which needed 10mg/L of Ag. For the most part, the Ag nanoparticles seemed to be of a nearly spherical shape, although on closer examination were determined to be mainly polyhedral. Leaves biomass, produced mainly quantum dot nanoparticles with sizes below 10 nm and the Ag nanoparticles were mostly AgO. The cytotoxicity of Ag NPs in a suspension tested using the Ag nanoparticles on E. coli was highly effective towards inhibition of bacterial growth

Green synthesis of silver nanoparticles using vitis vinifera natural extract and evaluation of their antibacterial activity

Antibiotic resistance represents a risk to human health. AgNPs have been shown to have antibacterial, antiviral and antifungal properties. Using plant extracts to synthesize AgNPs is considered an environmentally friendly, scalable and low-cost route that represents an advance over chemical and physical methods. In this study, AgNPs were synthesized and characterized using Vitis vinifera leaf extract. Furthermore, the effect of pH on the reaction rate, size and morphology of the AgNPs was evaluated. The change of color of the solution from light yellow to dark brown indicated the formation of AgNPs. Depending on the pH of the solution, the AgNPs exhibited a characteristic absorbance peak at 407, 409, 442, and 451 nm. The FT-IR analysis demonstrated the presence of polyphenolic compounds, flavonoids and amino groups that act as reducing and stabilizing agents in the formation of AgNPs. XPS analysis confirmed the presence of Ag0. The TEM images showed that the nanoparticles were spherical, with an average size of 20.42, 14.52, and 5.24 nm depending on the synthesis pH. The AgNPs exhibited strong antibacterial activity against S. aureus and E. coli, with a greater effect on S. aureus (27 mm zone of inhibition). This variation in antimicrobial activity is probably because a greater amount of Ag+ binds to the cell wall of S. aureus so that it will have a greater biocidal effect on this bacteria. This study demonstrates that AgNPs synthesized from Vitis vinifera leaf extract have great antimicrobial potential against multidrug-resistant bacteria.La resistencia a los antibióticos representa un riesgo para la salud humana. Se ha demostrado que AgNPs tienen propiedades antibacterianas, antivirales y antifúngicas. El uso de extractos de plantas para sintetizar AgNP se considera una ruta ecológica, escalable y de bajo precio que representa un avance sobre los métodos químicos y físicos. En este estudio, se sintetizaron y caracterizaron AgNPs utilizando el extracto de hojas de Vitis vinífera. Además, se evaluó el efecto del pH sobre la velocidad de reacción, el tamaño y la morfología de las AgNP. El cambio de color de la solución de amarillo claro a marrón obscuro indicó la formación de AgNPs. Dependiendo del pH de la solución, las AgNPs exhibieron un pico de absorbancia característico a 407, 409, 442 y 451 nm. El análisis FT-IR demostró la presencia de compuestos polifenólicos, flavonoides y grupos amino que actúan como agentes reductores y estabilizantes en la formación de las AgNPs. El análisis XPS confirmó la presencia de Ag0. Las imágenes TEM mostraron que las nanopartículas son esféricas, con un tamaño promedio de 20.42, 14.52 y 5.24 nm según el pH de síntesis. Las AgNP exhibieron una fuerte actividad antibacteriana contra S. aureus y E. coli, con un mayor efecto en S. aureus (zona de inhibición = 27 mm). Esta variación en la actividad antimicrobiana probablemente se deba a que una mayor cantidad de Ag+ se unen a la pared celular de S. aureus, por lo que tendrá un mayor efecto biocida sobre esta bacteria. Este estudio demuestra que las AgNP sintetizadas a partir del extracto de hojas de Vitis vinífera tienen un gran potencial antimicrobiano contra bacterias multirresistentes.Ingeniero/a Biomédico/