Synthesis of silver nanoparticles by chemical and biological methods and their antimicrobial properties

Biogenic synthesis of nanoparticles offers an attractive alternate to chemical synthesis methods. Various hazard free, eco-friendly methods of synthesis of silver nanoparticles are in operation. In chemical reduction methods, the reducing agent is a chemical solution, whereas in biological ones, the collection of enzymes, especially nitrate reductase, plays this role. The highest antibacterial activity of silver nanoparticles synthesised by chemical and biological methods was found in Staphylococcus aureus and Escherichia coli. The paper aims to discuss some fundamental issues about non-biological methods and benefits about biological methods for silver nanoparticles synthesis and their antibacterial studies.     

Synthesis of silver nanoparticles in an eco-friendly way using Phyllanthus amarus leaf extract: Antimicrobial and catalytic activity

In the present study, silver nanoparticles (AgNPs) with a flower-like structure were synthesized through an easy, rapid and eco-friendly pathway using Phyllanthus amarus leaf extract. The obtained AgNPs were characterized using ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). In addition, the antimicrobial and catalytic activities of the bio-synthesized AgNPs were carried out. Our results indicated that the concentration of the Ag precursor and the volume of the leaf extract played key roles in the formation of the flower-shaped AgNPs. Morphology study confirms the shape of the obtained bio-AgNPs as flower like structure. This study also showed the presence of clear capping layers surrounding and apparently interacting with the nanoparticles. Moreover, our studies indicated this interaction to involve bio-organic capping agents in the leaf extract. UV–Vis absorption spectra confirmed the formation of AgNPs with an optimized size. The zeta (ζ) potential of the AgNPs attests the stability of the nanoparticles. FTIR spectra provided evidence for the presence of biomolecules responsible for the reduction as well as capping of the AgNPs. Finally, the bio-synthesized AgNPs were shown to be an excellent microbial activity against the selected pathogens and enhanced catalyst of the reduction of rhodamine B.     

Green synthesis of silver nanoparticles using Nervalia zeylanica leaf extract and evaluation of their antioxidant,catalytic, and antimicrobial potentials

ABSTRACT

Here we report a simple, one-pot, inexpensive, and eco-friendly method for the synthesis of silver nanoparticles. The leaf extract of a medicinal plant Nervalia zeylanica was used as reducing and stabilizing agent for the synthesis of nanoparticles by microwave-assisted strategy. The nanoparticles show characteristic surface plasmon peak at 468?nm in UV–vis absorption spectrum. The involvement of phytochemicals in the reduction and stabilization of nanoparticles was confirmed by FTIR analysis. Using X-ray diffraction analysis, the crystalline nature of the nanoparticles was demonstrated. Transmission electron microscopic analysis shows that the nanoparticles were in spherical shape with average particle size of 34.2?nm. The antioxidant studies were performed by the 1,1-diphenyl-2-picryl hydrazyl method. The nanoparticles show excellent scavenging activities than the leaf extract. The IC₅₀ values of silver nanoparticles and the leaf extract, respectively, were 15.20 and 92.83?µg?mL^?1. The catalytic activities of synthesized nanoparticles were examined by using them in the reduction of organic dyes. The nanoparticles show excellent catalytic activities and follow pseudo-first-order kinetics. The antimicrobial activities of nanoparticles were analyzed by an agar well diffusion method against six microbial strains and found that the nanoparticles were highly toxic against all the tested microbial strains.     

Rapid biologically one-step synthesis of stable bioactive silver nanoparticles using Osage orange (Maclura pomifera) leaf extract and their antimicrobial activities

Synthesis of nanoparticles by using natural products as reducing and stabilizing agents have been widely used in various fields especially medicine, primarily because of its lower cost, simplicity, and less toxic byproducts. In the present work, silver nanoparticles (Ag NPs) were rapidly synthesized from silver nitrate in a green one-step synthesis by the aqueous extracts of Osage orange (Maclura pomifera) leaf as a reducing and stabilizing agent simultaneously. The effects of pH, extract quantity, and silver salt concentration were investigated to determine the optimum conditions of green synthesis of Ag NPs. The synthesized Ag NPs were characterized by different techniques including UV–Visible (UV–Vis) absorption spectroscopy, X-ray diffraction (XRD), Fourier transform Infrared (FT-IR) Spectroscopy, and Transmission Electron Microscopy (TEM). The Ag NPs showed surface plasmon resonance centered at 415?nm. The XRD pattern and TEM analysis revealed spherical, stable, and uniform Ag NPs with the average particle size of about 12?nm. The FT-IR spectroscopy showed that mainly hydroxyl functional groups, as both the reducing and stabilizing agent are responsible for silver nanoparticles synthesis. The antimicrobial activity of the synthesized Ag NPs showed a significant microbicidal effect on all clinical isolates especially, Gram-negative bacteria and fungi. These results suggest that such stable and uniform Ag NPs can be synthesized rapidly and simply for clinical as well as pharmaceutical applications.     

Antibacterial mechanism of biogenic silver nanoparticles of Lactobacillus acidophilus

The development of reliable, eco-friendly protocol for the synthesis of nanomaterials is a challenging issue in the current nanotechnology. In the present study, we reported an environmentally benign and rapid method for biogenesis of silver nanoparticles using Gram-positive bacterium Lactobacillus acidophilus which acts both as reducing and capping agent. It was observed that the culture filtrate reduced silver ions into silver nanoparticles within 24 hrs of reaction time under room temperature. The UV–Vis spectrum shows the absorbance maximum at 434 nm, which is a characteristic of surface plasmon resonance of silver. X-ray diffraction analysis showed that the nanoparticles were of face-centred cubic crystalline structure. The presence of stable spherical-shaped silver nanoparticles in the size range of 4–50 nm was determined using the transmission electron microscopy analysis. Further, these nanoparticles showed effective antibacterial activity towards Klebsiella pneumoniae. The mechanism of the silver nanoparticle bactericidal activity is discussed in terms of its interaction with the cell membrane of bacteria by causing cytolysis and leakage of proteins and carbohydrates.     

Green synthesis of silver nanoparticles using aqueous solution of Ficus benghalensis leaf extract and characterization of their antibacterial activity

The present study reports an environmentally friendly and rapid method for synthesis of silver nanoparticles. Although several articles have been reported for the synthesis of silver nanoparticles from plant extract, here we have developed a green synthetic method for silver nanoparticles using Ficus benghalensis leaf extract which acts as a reducing and capping agent. It was observed that use of Ficus benghalensis leaf extract makes a fast and convenient method for the synthesis of silver nanoparticles and can reduce silver ions into silver nanoparticles within 5 min of reaction time without using any harsh conditions. Silver nanoparticles so prepared were characterized by using UV-visible spectroscopy, transmission electron microscope-energy dispersive spectra (TEM-EDS) and X-ray diffraction (XRD). Further, these nanoparticles show effective antibacterial activity toward E.coli MTCC1302 due to high surface to volume ratio.     

Layer-by-layer deposition of green synthesised silver nanoparticles on polyester air filters and its antimicrobial activity

Silver nanoparticles stabilised with anionic polymeric polyelectrolytes were successfully synthesised by high-energy UV reduction. Three types of polyelectrolytes were used including poly(methacrylic acid) (PMA), poly(acrylic acid) (PAA) and poly(4-styrenesulphonic acid-co-maleic acid) (CoPSS). The formation of the prepared solutions exhibited surface plasmon resonance at the wavelength of 475, 730 and 408 nm by using PMA, PAA and CoPSS as the stabilising agents. UV–visible spectrophotometer, transmission electron microscope (TEM) and zeta potential analyser were employed to characterise the formation of the prepared solutions. The silver nanoparticles stabilised with anionic polyelectrolytes were immobilised on polyester air filters using a layer-by-layer technique. This is the sequential dipping of polyester air filters in a dilute solution of cationic poly(diallyldimethylammonium chloride) and anionic polymeric polyelectrolytes capped silver. The surface topography of the polyester air filters were measured by field emission scanning electron microscope. Results showed that silver nanoparticles had the highest surface coverage on the polyester air filters probably because it is a good bonding candidate and insures strong film growth. The multilayers polyester air filters coated silver nanoparticles were tested against the gram positive pathogen Staphylococcus aureus. The deposition of silver nanoparticles onto the polyester air filters resulted in 92.18%, 84.32% and 71.19% of bacteria removal using PMA, PAA and CoPSS as the stabilising agent.     

Eco-friendly green synthesis of silver nanoparticles and their potential applications as antioxidant and anticancer agents

Abstract

Eco-friendly green synthesis of nanoparticles using medicinal plants gained immense importance due to its potential therapeutic uses. In the current study, silver nanoparticles (AgNPs) were synthesized using water extract of Jurinea dolomiaea leaf and root at room temperature. MTT assay was used to study anticancer potential of AgNPs against cervical cancer cell line (HeLa), breast cancer cell lines (MCF-7), and mouse embryonic fibroblast (NIH-3 T3) cell line for toxicity evaluation. The antioxidant potential was evaluated using stable DPPH radicals. In addition, the apoptotic nuclear changes prompted by AgNPs in more susceptible HeLa cells were observed using fluorescence microscope through DAPI and PI staining. Physiochemical properties of biosynthesized AgNPs were characterized using various techniques. AgNPs were formed in very short time and UV–vis spectra showed characteristic absorption peak of AgNPs. SEM and TEM showed spherical shape of AgNPs and XRD revealed their crystalline nature. EDX analysis revealed high percentage of silver in green synthesized AgNPs. FTIR analysis indicated involvement of secondary metabolites in fabrication of AgNPs. In vitro cytotoxic and antioxidant study revealed that herb and biosynthesized AgNPs exhibited significant dose-dependent and time-dependent anticancer and antioxidant potential. Furthermore, study on normal cell line and microscopic analysis of apoptosis revealed that AgNPs exhibited good safety profile as compared to cisplatin and induces significant apoptosis effect. Based on the current findings, it is strongly believe that use of J. dolomiaea offers large scale production of biocompatible AgNPs that can be used as alternative anticancer agents against cancer cell lines tested.     

Atmospheric induced nanoparticles due to the urban street dust

ABSTRACT

Urban street dust (SD) represents a natural source of mineral floating particles (FP) in the atmosphere. The FP particles have usually a wide range of sizes. These particles were monitored and collected by automatic stations in Cluj-Napoca, Romania. The SD and FP samples were investigated by XRD and SEM-EDX analysis. The obtained results prove that both, SD and FP, have a similar composition, namely quartz, clay particles (e.g., muscovite, and kaolinite), calcite, and trace of lepidocrocite. Nanostructural features and fine micro-scaled particles are observed. Quartz and clay nanoparticles were found in SD samples as well as in FP samples. The AFM investigation reveals a nano-size range for quartz particles between 80–90 nm, and 40–60 nm diameter for clay particles. Similar values were obtained by TEM microscopy. The high resolution microscopy results were confirmed by the values obtained by Scherrer formula applied to the XRD patterns. Composition and dimensional similarities found for the nanoparticles in SD and FP samples prove that mineral nanofractions in atmosphere were induced by the urban environmental interactions with the SD. Results provide valuable information on the size, shape, and composition of nanoparticles induced in atmosphere by winds and by environmental interactions with the SD. This work contributes to the evaluation of the air pollution and simultaneously it offers a basis for an improved life quality for Cluj-Napoca population.     

Highly efficient in vitro biosynthesis of silver nanoparticles using Lysinibacillus sphaericus MR-1 and their characterization

Abstract

Silver nanoparticles (AgNPs) have been widely used in diverse fields due to their superior properties. Currently the biosynthesis of AgNPs is in the limelight of modern nanotechnology because of its green properties. However, relatively low yield and inefficiency diminish the prospect of applying these biosynthesized AgNPs. In this work, a rapid mass AgNP biosynthesis method using the cell-free extract of a novel bacterial strain, Lysinibacillus sphaericus MR-1, which has been isolated from a chemical fertilizer plant, is reported. In addition, the optimum synthesis conditions of AgNPs were investigated. The optimum pH, temperature, dosage, and reaction time were 12, 70 °C, 20 mM AgNO₃, and 75 min, respectively. Finally, AgNPs were characterized by optical absorption spectroscopy, zeta potential and size distribution analysis, x-ray diffraction, electron microscopy, and energy-dispersive x-ray spectroscopy. The results revealed that these biosynthesized AgNPs were bimolecular covered, stable, well-dispersed face centered cubic (fcc) spherical crystalline particles with diameters in the range 5–20 nm. The advantages of this approach are its simplicity, high efficiency, and eco-friendly and cost-effective features.     

Facile photoreductive synthesis of silver nanoparticles for antimicrobial studies

In the present work, silver nanoparticles stabilized with L-Cysteine (L-Cys) were synthesized based on the one-pot green process by UV irradiation, in which L-Cysteine acts as biological capping agent. The composition and morphological characteristics of the L-Cys capped AgNPs has been ascertained by different techniques such as UV–vis, FL, XRD, TEM, EDX, FTIR and CD analysis. The results demonstrated the formation of spherical nanoparticles of pure Ag° coated with L-Cys. The antibacterial tests on L-Cys capped AgNPs were performed, exerting effective antimicrobial activity both against E. coli and S. aureus, with a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 21.9 μg/mL and 175 μg/mL, respectively. Considering this simple and green process, the approach may facilitate new approaches to the manufacture of AgNPs-based antibacterial agent.     

Green synthesis and characterization of hexagonal shaped MgO nanoparticles using insulin plant (Costus pictus D. Don) leave extract and its antimicrobial as well as anticancer activity

Green synthesis is an ecofriendly novel technology and attractive research area for the production of metal oxide nanoparticles in bio-medical and chemical applications. The green perspective includes solvents, reductants or stabilizing agents obtained from a natural resource as they are non-toxic and ecofriendly. In this study, a sustainable green synthetic strategy to synthesize magnesium oxide nanoparticles by employing Costus pictus D. Don plant leaf extract as a reducing agent. The successful formation of magnesium oxide nanoparticles was confirmed by comprehensive characterization techniques. The presence of biomolecules and metal oxides were confirmed by Fourier transform Infrared (FT-IR) spectral data analysis. The X-ray diffraction (XRD) revealed the formation of pure cubic MgO crystalline nanoparticles. The surface morphology of MgO particles observed by Scanning electron microscope (SEM) showed the hexagonal-shaped MgO crystallites. The average size of biosynthesized MgO nanoparticles was measured to be around 50?nm by Transmission Electron Microscopy (TEM). The mechanism for the formation of MgO nanoparticles was suggested in this study. The biosynthesized magnesium oxide particles showed good antimicrobial and exhibited maximum inhibition rate for MgO nanoparticles at 200?µg showing efficient anticancer activity.     

Highly efficient in vitro biosynthesis of silver nanoparticles using Lysinibacillus sphaericus MR-1 and their characterization

Silver nanoparticles (AgNPs) have been widely used in diverse fields due to their superior properties. Currently the biosynthesis of AgNPs is in the limelight of modern nanotechnology because of its green properties. However, relatively low yield and inefficiency diminish the prospect of applying these biosynthesized AgNPs. In this work, a rapid mass AgNP biosynthesis method using the cell-free extract of a novel bacterial strain, Lysinibacillus sphaericus MR-1, which has been isolated from a chemical fertilizer plant, is reported. In addition, the optimum synthesis conditions of AgNPs were investigated. The optimum pH, temperature, dosage, and reaction time were 12, 70 °C, 20 mM AgNO₃, and 75 min, respectively. Finally, AgNPs were characterized by optical absorption spectroscopy, zeta potential and size distribution analysis, x-ray diffraction, electron microscopy, and energy-dispersive x-ray spectroscopy. The results revealed that these biosynthesized AgNPs were bimolecular covered, stable, well-dispersed face centered cubic (fcc) spherical crystalline particles with diameters in the range 5–20 nm. The advantages of this approach are its simplicity, high efficiency, and eco-friendly and cost-effective features.     

A facile synthesis of silver nanoparticle with SERS and antimicrobial activity using Bacillus subtilis exopolysaccharides

In this study, we report a facile synthesis of silver nanoparticle having SERS and antimicrobial activity using bacterial exopolysaccharide (EPS). Bacillus subtilis (MTCC 2422) was grown in nutrient broth and the extracellular EPS secreted by the organism was extracted and purified. The purified EPS was used for the synthesis of silver nanoparticles. The kinetics of silver nanoparticle synthesis was deduced by varying the exposure time and the concentration of EPS. The rate constant (k) for the synthesis of silver nanoparticle was calculated from the slope of ln(A^∞ ? A^t) versus time plot. The k value was found to be 3.49 × 10^?3, 5.81 × 10^?3 and 5.03 × 10^?3 per min for particle synthesis using 2, 5 and 10 mg/mL EPS, respectively. The nanoparticles synthesised had an average particle size of 5.18 ± 1.49 nm, 1.96 ± 0.77 nm and 2.08 ± 0.88 nm for 2, 5 and 10 mg/mL EPS, respectively. The synthesised particles were characterised using UV-Vis absorbance spectroscopy, high-resolution transmission electron microscopy (HRTEM) attached to EDS (energy dispersive spectroscopy), Fourier transform infrared spectroscopy (FTIR), surface enhanced Raman spectroscopy (SERS) and zeta potential analyser. To our knowledge, this is the first study to report SERS activity of microbial Bacillus subtilis EPS-based synthesis of silver nanoparticle. HRTEM images showed silver nanoparticle entrapped in polysaccharide nanocages. Silver nanoparticle showed higher adherence towards the bacterial surface, with good bactericidal activity against Pseudomonas aeroginosa and Staphylococcus aureus.     

Synthesis,characterisation and antimicrobial activity of manganese- and iron-doped zinc oxide nanoparticles

The present work reports study on antimicrobial activity of pure and doped ZnO nanocomposites. Polyvinyl pyrrolidone capped Mn- and Fe-doped ZnO nanocomposites were synthesised using simple chemical co-precipitation technique. The synthesised materials were characterised using transmission electron microscope (TEM), X-ray powder diffraction (XRD), energy dispersive X-ray fluorescence (EDXRF), Fourier transform infrared (FTIR) spectroscopy and ultraviolet (UV) visible spectroscopy. The XRD and TEM studies reveal that the synthesised ZnO nanocrystals have a hexagonal wurtzite structure with average crystalline size ～7–14 nm. EDXRF and FTIR study confirmed the doping and the incorporation of impurity in ZnO nanostructure. The antimicrobial activities of nanoparticles (NPs) were studied against fungi, gram-positive and gram-negative bacteria using the standard disc diffusion method. The photocatalytic activities of prepared NPs were evaluated by degradation of methylene blue dye in aqueous solution under UV light irradiation. Experimental results demonstrated that ZnO NPs doped with 10% of Mn and Fe ions showed maximum antimicrobial and photodegradation efficiency in contrast with that of the 1% loading. The enhancement in antimicrobial effect and photocatalytic degradation is attributed to the generation of reactive oxygen species due to the synergistic effects of Mn and Fe loading.     

Extracellular biosynthesis,characterisation and in-vitro antibacterial potential of silver nanoparticles using Agaricus bisporus

Microbial silver nanoparticles have been known to have bactericidal effects but the antimicrobial mechanism has not been clearly revealed. The use of microorganisms in the synthesis of nanoparticles emerges as an ecofriendly and exciting approach. Here we report on the extracellular synthesis method for the preparation of silver nanoparticles in water using the extract of Agaricus bisporus, a naturally occurring edible mushroom, as reducing and protecting agents. The silver nanoparticles were characterised by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-Ray diffraction (XRD) analysis. The synthesised silver nanoparticles showed antibacterial activity against the multi-drug resistant Gram positive and Gram negative bacterial pathogens.     

Biosynthesis of silver nanoparticles in collagen gel improves their medical use in periodontitis treatment

Silver nanoparticles (AgNP) suspensions were biosynthesized by silver ions reduction in the presence of collagen, a nontoxic, organic polymer, intending to improve their medical use in periodontitis treatment. Spectrophotometric measurements showed a time- and concentration-dependent increase of AgNP formation in each suspension variant. Transmission electron microscopy revealed spherical morphology of AgNP in collagen and their mean diameter size was around 30?nm. The particle size distribution and zeta potential values of AgNP in collagen were determined by dynamic light scattering measurements. The surface charge of AgNP in collagen was positive, while commercial AgNP stabilized in citrate had negative surface charge. In vitro cytotoxicity testing of AgNP in collagen showed that they were biocompatible with human gingival fibroblasts in a wider range of concentrations than commercial nanoparticles. The antibacterial activity of AgNP in collagen against two pathogenic strains present in the periodontal pocket was dose-dependent and higher than that of AgNP in citrate. All these results demonstrated that AgNP prepared in collagen gel had improved properties, like small diameter, positive surface charge, high biocompatibility in human gingival fibroblasts, efficiency against bacterial growth and, thus, better therapeutic potential in periodontal disease treatment.     

Green synthesis of silver nanoparticles using Cyathea nilgirensis Holttum and their cytotoxic and phytotoxic potentials

The present study aimed at synthesizing silver nanoparticles (AgNPs) from the aqueous extract of C. nilgirensis and their biopotential using cytotoxicity and phytotoxicity. On mixing the aqueous extract with 1?mM AgNO₃ solution, the color changes from pale yellow to yellowish brown color. The absorption spectra of yellowish brown nanoparticle showed a plasmon absorption band with a maximum of 3.806 and 1.028 abs in 311 and 440?nm, respectively. The Fourier transform infrared spectroscopy (FTIR) spectra confirmed that phenolic compounds have stronger ability to bind with metal, indicating that phenolics could possibly form metal nanoparticles to prevent agglomeration and thereby stabilize the medium. The size of AgNP is found to be in the 45.0–74.0?nm range. The Energy-dispersive X-ray (EDX) spectra analysis revealed the presence of a strong Ag peak. The results indicated that C. nilgirensis aqueous extract was found efficient for the synthesis of AgNPs.     

Medicinal plants mediated the green synthesis of silver nanoparticles and their biomedical applications

The alarming effect of antibiotic resistance prompted the search for alternative medicine to resolve the microbial resistance conflict. Over the last two decades, scientists have become increasingly interested in metallic nanoparticles to discover their new dimensions. Green nano synthesis is a rapidly expanding field of interest in nanotechnology due to its feasibility, low toxicity, eco‐friendly nature, and long‐term viability. Some plants have long been used in medicine because they contain a variety of bioactive compounds. Silver has long been known for its antibacterial properties. Silver nanoparticles have taken a special place among other metal nanoparticles. Silver nanotechnology has a big impact on medical applications like bio‐coating, novel antimicrobial agents, and drug delivery systems. This review aims to provide a comprehensive understanding of the pharmaceutical qualities of medicinal plants, as well as a convenient guideline for plant‐based silver nanoparticles and their antimicrobial activity.     

Syntheses and characterisation of silver nanoparticles in the acrylate copolymers

Silver nanoparticles were synthesised by polyol method using copolymer templates under microwave heating. The copolymer templates were synthesised by reacting the synthesised macromonomers with comonomer using free radical polymerisation. The copolymers were characterised by Fourier Transform InfraRed, ¹H-NMR and ¹³C-NMR. The copolymers were further characterised by gel permeation chromatography for molecular weights and thermogravimetric analysis for thermal stability. These copolymers were used as nanoreactors in the syntheses of silver nanoparticles. The nanoparticles were characterised by various instrumental methods like UV-visible, FT-IR and High-resolution transmission electron microscopy to establish the average particle size and shape. Antibacterial activities of the copolymer-stabilised silver nanoparticles were tested on various microorganisms.