Antibacterial Activity Of Silver Nanoparticles Research Articles

Enhancement of the Antibacterial Activity of Silver Nanoparticles against Phytopathogenic BacteriumRalstonia solanacearumby Stabilization

In this paper, the enhanced antibacterial activity of silver nanoparticles (AgNPs) against the phytopathogenic bacteriumRalstonia solanacearumafter stabilization using selected surfactants (SDS, SDBS, TX-100, and Tween 80) was examined, in comparison with silver ion. Tween 80 was found to be the most preferable stabilizer of AgNPs due to the beneficial synergistic effects of the AgNPs and surfactant. However, all the surfactants nearly had no effects on the antibacterial activity of Ag+.In vitro, Tween 80-stabilized AgNPs showed the highest bactericidal activity againstR. solanacearum. Further measurements using TEM, fluorescence microscopy, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that though Ag+and Tween 80-Ag+induced high toxicity, Tween 80-stabilized AgNPs displayed most severe damage when in direct contact with cells, causing mechanistic injury to the cell membrane and strongly modifying and destructing the cellular proteins. Meanwhile,in vivo, the pot experiments data indicated that the control efficiency of Tween 80-stabilized AgNPs on tobacco bacterial wilt was 96.71%, 90.11%, and 84.21%, at 7 days, 14 days, and 21 days, respectively. Based on the results evidencing their advantageous low dosage requirements and strong antimicrobial activity, Tween 80-stabilized AgNPs are a promising antibacterial agent for use in alternative crop disease control approaches.

Shape effect on the antibacterial activity of silver nanoparticles synthesized via a microwave-assisted method.

Silver nanoparticles (AgNPs) are used as sustained-release bactericidal agents for water treatment. Among the physicochemical characteristics of AgNPs, shape is an important parameter relevant to the antibacterial activity. Three typically shaped AgNPs, nanocubes, nanospheres, and nanowires, were prepared via a microwave-assisted method and characterized by TEM, UV-vis, and XRD. The antibacterial activity of AgNPs was determined by OD growth curves tests, MIC tests, and cell viability assay against Escherichia coli. The interaction between AgNPs and bacterial cells was observed by TEM. The results showed that the three differently shaped AgNPs were nanoscale, 55 ± 10 nm in edge length for nanocubes, 60 ± 15 nm in diameter for nanospheres, 60 ± 10 nm in diameter and 2-4 μm in length for nanowires. At the bacterial concentration of 10(4) CFU/mL, the MIC of nanocubes, nanospheres, and nanowires were 37.5, 75, and 100 μg/mL, respectively. Due to the worst contact with bacteria, silver nanowires exhibited the weakest antibacterial activity compared with silver nanocubes and silver nanospheres. Besides, silver nanocubes mainly covered by {100} facets showed stronger antibacterial activity than silver nanospheres covered by {111} facets. It suggests that the shape effect on the antibacterial activity of AgNPs is attributed to the specific surface areas and facets reactivity; AgNPs with larger effective contact areas and higher reactive facets exhibit stronger antibacterial activity.

Evaluation of the of antibacterial efficacy of polyvinylpyrrolidone (PVP) and tri-sodium citrate (TSC) silver nanoparticles

We present silver nanoparticles as the new age broad spectrum antibiotic. Siver nanoparticles exhibit unique physical and chemical properties that make them suitable for understanding their biological potential as antimicrobials. In this study, we explored the antibacterial activity of silver nanoparticles (TSC-AgNPs) and silver nanoparticles doped with polyvinylpyrrolidone (PVP-AgNPs) against Gram-negative and Gram-positive bacteria, Escherichia coli (DH5α) and Staphylococcus aureus, (ATCC 13709). Nucleation and growth kinetics during the synthesis process of AgNPs were precisely controlled using citrate (TSC) and further doped with polyvinylpyrrolidone (PVP). This resulted in the formation of two different sized nanoparticles 34 and 54 nm with PDI of 0.426 and 0.643. The physical characterization was done by nanoparticle tracking analysis and scanning electron microscopy, the results of which are in unison with the digital light scattering data. We found the bactericidal effect for both TSC-AgNPs and PVP-AgNPs to be dose-dependent as determined by the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against E. coli and S. aureus. Interestingly, we also observed that AgNPs showed enhanced antimicrobial activity with a MIC of 26.75 and 13.48 µg/ml for E. coli and S. aureus, respectively, while MBC for AgNPs are 53.23 and 26.75 µg/ml for E. coli and S. aureus, respectively. Moreover, AgNPs showed increased DNA degradation as observed confirming its higher efficacy as antibacterial agent than the PVP doped AgNPs.

Green synthesis of silver nanoparticles using Coffea arabica seed extract and its antibacterial activity.

A novel green source was opted to synthesize silver nanoparticles using dried roasted Coffea arabica seed extract. Bio-reduction of silver was complete when the mixture (AgNO3+extract) changed its color from light to dark brown. UV-vis spectroscopy result showed maximum adsorption at 459 nm, which represents the characteristic surface plasmon resonance of nanosilver. X-ray crystal analysis showed that the silver nanoparticles are highly crystalline and exhibit a cubic, face centered lattice with characteristic (111), (200), (220) and (311) orientations. Particles exhibit spherical and ellipsoidal shaped structures as observed from TEM. Composition analysis obtained from SEM-EDXA confirmed the presence of elemental signature of silver. FTIR results recorded a downward shift of absorption bands between 800-1500 cm(-1) indicting the formation of silver nanoparticles. The mean particle size investigated using DLS was found to be in between 20-30 nm respectively. Anti-bacterial activity of silver nanoparticles on E. coli and S. aureus demonstrated diminished bacterial growth with the development of well-defined inhibition zones.

Prevalence, molecular characterization of Staphylococcus aureus isolated from cheese and in vitro antibacterial activity of silver nanoparticles against such strains.

Aim:The aim was to investigate cheese samples for the prevalence of Staphylococcus aureus, evaluate multiplex polymerase chain reaction (PCR) methods for S. aureus identification, as well as to determine the antibacterial activity of silver nanoparticles against such strains.Materials and Methods:Total of 100 random locally manufactured cheese samples were collected from Qena dairy markets, Egypt, and examined conventionally for the prevalence of S. aureus then, confirmation of these isolates were done using multiplex PCR. The antibacterial activity of silver nanoparticles against such isolates was also checked.Results:Lower prevalence of S. aureus in Damietta cheese (54%) than in Kareish cheese (62%) was recorded. As well lower frequency distribution for both S. aureus (36%) and CNS (8%) was also reported for Damietta cheese. Using of multiplex PCR method for S. aureus identification have been confirmed all 58 S. aureus stains that were identified conventionally by detection of two PCR products on agarose gel: The 791 bp and the 638 bp. The correlation coefficient between conventional and multiplex PCR method was 0.91 and was significant at p≤0.001. Regarding antibacterial activity of silver nanoparticles using disk diffusion method on Baird Parker agar it was found that inhibition zone of silver nanoparticles against S. aureus, was 19.2±0.91 mm and it was higher than that produced by gentamicin (400 units/ml) 15.2±0.89 mm.Conclusions:The present study illustrated the higher prevalence of S. aureus in cheese samples that may constitute a public health hazard to consumers. According to the results, it can be concluded that silver nanoparticles can be used as an effective antibacterial against S. aureus. Thereby, there is a need for an appropriate study for using silver nanoparticles in cleaning and disinfection of equipment and in food packaging.

Exploitation of endophytic fungus, Guignardia mangiferae for extracellular synthesis of silver nanoparticles and their in vitro biological activities

The aim of this study was to synthesize highly biocompatible and functionalized silver nanoparticles using endophytic fungi isolated from the leaves of medicinal plants. Among 13 fungi tested, the isolate, Guignardia mangiferae (Bios PTK 4) extracellularly synthesized well-dispersed and extremely stable silver nanoparticles under optimized reaction conditions within 12h. These nanoparticles were characterized by HR-TEM, SAED, XRD and EDX analyses. G. mangiferae synthesized 5–30nm sized, spherical shaped silver nanoparticles. Effect of pH on the antibacterial activity of silver nanoparticles was studied using well diffusion assay; on the basis of particle stability and antibacterial activity, pH 7 was found to be optimum. The leakage of intracellular components has clearly demonstrated that silver nanoparticles damage the bacterial cells by formation of pores, which affect the membrane permeability and finally leads to cell death. In addition, silver nanoparticles exhibited excellent antifungal activity against plant pathogenic fungi. Cytotoxic effects of silver nanoparticles showed IC50 values of 63.37, 27.54 and 23.84μg/mL against normal African monkey kidney (Vero), HeLa (cervical) and MCF-7 (breast) cells, respectively, at 24h incubation period. Thus, the obtained results convincingly suggest that silver nanoparticles synthesized from G. mangiferae are highly biocompatible and have wider applicability and they could be explored as promising candidates for a variety of biomedical/pharmaceutical and agricultural applications.

Analysis of Anti-Bacterial Activity of Silver Nanoparticles from Pomegranate (Punicagranatum) Seed and Peel Extracts

Analysis of Anti-Bacterial Activity of Silver Nanoparticles from Pomegranate (Punicagranatum) Seed and Peel Extracts

Chitosan/silver nanocomposites: Synergistic antibacterial action of silver nanoparticles and silver ions

In the present work chitosan–silver (CS/Ag) nanocomposites, either in the form of nanoparticles (AgNP) or as ionic dendritic structures (Ag+), are synthesized by a simple and environmentally friendly in situ chemical reduction process. The antibacterial activity of the resulting nanocomposites in the form of films is studied against two bacteria, Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. The relationship between electrical, structural and antibacterial properties of CS/AgNP and CS/Ag+ nanocomposites are studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction, and UV–Vis, impedance, infrared and X-ray photoelectron spectroscopies. The results demonstrate that in contrast to CS/Ag+ ion films, the CS/AgNP composites films (average particle size less than 10nm) showed a significantly higher antibacterial potency. The collective action of AgNP and Ag+ ions facilitate the enhancement and synergetic antibacterial activity below certain critical concentration. The bactericide activity of both CS/AgNP and CS/Ag+ ion composite films increases by increasing the concentration of Ag. The composites containing 1wt.% of silver nanoparticles and about of 2wt.% of silver ions exhibit a maximum antibacterial activity, which is close to their electrical percolation threshold. The concentration of AgNP and Ag+ ions above the threshold level greatly diminish the antibacterial potential.

Impact of protecting ligands on surface structure and antibacterial activity of silver nanoparticles.

Silver nanoparticles (Ag NPs) have attracted much attention in the past decade because of their unique physicochemical properties and notable antibacterial activities. In particular, thiol-protected Ag NPs have come to the forefront of metal nanoparticle studies, as they have been shown to possess high stability and interesting structure-property relationships. However, a clear correlation between thiol-protecting ligands, the resulting Ag NP surface structure, and their antibacterial properties has yet to be determined. Here, a multielement (Ag and S), multi-edge (Ag K-edge, Ag L3-edge, S K-edge) X-ray absorption spectroscopy (XAS) methodology was used to identify the structure and composition of Ag NPs protected with cysteine. XAS characterization was carried out on similar-sized Ag NPs protected with poly(vinylpyrrolidone) (PVP), in order to provide a valid comparison of the ligand effect on surface structure. The PVP-Ag NPs showed a metallic Ag surface and composition, consistent with metal NPs protected by weak protecting ligands. On the other hand, the Cys-Ag NPs exhibited a distinct surface shell of silver sulfide, which is remarkably different than previously studied Cys-Ag NPs. The minimum inhibitory concentration (MIC) of both types of Ag NPs against Gram-positive (+) and Gram-negative (-) bacteria were tested, including Staphylococcus aureus (+), Escherichia coli (-), and Pseudomonas aeruginosa (-). It was found that the MICs of the Cys-Ag NPs were significantly lower than the PVP-Ag NPs for each bacteria, implicating the influence of the sulfidized surface structure. Overall, this work shows the effect of ligand on the surface structure of Ag NPs, as well as the importance of surface structure in controlling antibacterial activity.

A facile biomimetic preparation of highly stabilized silver nanoparticles derived from seed extract of Vigna radiata and evaluation of their antibacterial activity

The significant antibacterial activity of silver nanoparticles draws the major attention toward the present nanobiotechnology. Also, the use of plant material for the synthesis of metal nanoparticles is considered as a green technology. In this context, a non-toxic, eco-friendly, and cost-effective method has been developed for the synthesis of silver nanoparticles using seed extract of mung beans (Vigna radiata). The synthesized nanoparticles have been characterized by UV–visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), atomic absorption spectroscopy (AAS), and X-ray diffraction (XRD). The UV–visible spectrum showed an absorption peak at around 440 nm. The different types of phytochemicals present in the seed extract synergistically reduce the Ag metal ions, as each phytochemical is unique in terms of its structure and antioxidant function. The colloidal silver nanoparticles were observed to be highly stable, even after 5 months. XRD analysis showed that the silver nanoparticles are crystalline in nature with face-centered cubic geometry and the TEM micrographs showed spherical particles with an average size of 18 nm. Further, the antibacterial activity of silver nanoparticles was evaluated by well-diffusion method and it was observed that the biogenic silver nanoparticles have an effective antibacterial activity against Escherichia coli and Staphylococcus aureus. The outcome of this study could be useful for nanotechnology-based biomedical applications.

Plant mediated green synthesis and antibacterial activity of silver nanoparticles using Emblica officinalis fruit extract

A green straight forward method of synthesizing silver nanoparticles (AgNPs) in an aqueous medium was designed using Emblica officinalis (EO) fruit extract as stabilizer and reducer. The formation of AgNPs depends on the effect of extract concentration and pH were studied. The AgNPs was synthesized using E.officinalis (fruit extract) and nanoparticles were characterized using UV–Vis spectrophotometer, the presence of biomolecules of E.officinalis capped in AgNPs was found by FT-IR analysis, shape and size were examined by SEM and XRD. The XRD analysis respects the Bragg’s law and confirmed the crystalline nature of silver nanoparticles. From XRD the average size of AgNPs was found to be around 15nm. AFM has proved to be very helpful in the determination and verification of various morphological features and parameters. EO fruit extract mediated AgNPs was synthesized and confirmed through kinetic behavior of nanoparticles. The shape of the bio-synthesized AgNPs was spherical. Potent biomolecules of E.officinalis such as polyphenols, glucose, and fructose was capped with AgNPs which reduces the toxicity. The synthesized AgNPs were tested for its antibacterial activity against the isolates by disc diffusion method. The obtained results confirmed that the E.officinalis fruit extract is a very good bioreductant for the synthesis of AgNPs. It was investigated that the synthesized AgNPs showed inhibition and had significant antibacterial against both gram-positive and gram-negative bacterial strains.

Antibacterial Activity of Silver Nanoparticles Produced by Plantago Ovata Seed Extract Against Antibiotic Resistant Staphylococcus aureus

Results: The silver nanoparticles revealed Gaussian distributions with the average diameter of 13 nm with some deviations, and results showed that the highest and the lowest MIC of P. ovata seed extract were 100 and 12.5 mg/mL, respectively. Conclusions: The current study results showed that silver nanoparticles produced by Plantago ovata seed extract had an antibacterial effect on Staphylococcus aureus which was resistant against cefixime, trimethoprim-sulfamethoxazole and penicillin.

Antibacterial activity of silver nanoparticles synthesized from serine.

Silver nanoparticles (Ag NPs) were synthesized by a simple microwave irradiation method using polyvinyl pyrrolidone (PVP) as a capping agent and serine as a reducing agent. UV-Visible spectra were used to confirm the formation of Ag NPs by observing the surface plasmon resonance (SPR) band at 443nm. The emission spectrum of Ag NPs showed an emission band at 484nm. In the presence of microwave radiation, serine acts as a reducing agent, which was confirmed by Fourier transformed infrared (FT-IR) spectrum. High-resolution transmission electron microscopy (HR-TEM) and high-resolution scanning electron microscopy (HR-SEM) were used to investigate the morphology of the synthesized sample. These images showed the sphere-like morphology. The elemental composition of the sample was determined by the energy dispersive X-ray analysis (EDX). Selected area electron diffraction (SAED) was used to find the crystalline nature of the Ag NPs. The electrochemical behavior of the synthesized Ag NPs was analyzed by the cyclic voltammetry (CV). Antibacterial experiments showed that the prepared Ag NPs showed relatively similar antibacterial activities, when compared with AgNO3 against Gram-positive and Gram-negative bacteria.

Use of bioreporters and deletion mutants reveals ionic silver and ROS to be equally important in silver nanotoxicity

The mechanism of antibacterial action of silver nanoparticles (AgNp) was investigated by employing a combination of microbiology and geochemical approaches to contribute to the realistic assessment of nanotoxicity. Our studies showed that suspending AgNp in media with different levels of chloride relevant to environmental conditions produced low levels of ionic silver thereby suggesting that dissolution of silver ions from nanoparticulate surface could not be the sole mechanism of toxicity. An Escherichia coli based bioreporter strain responsive to silver ions together with mutant strains of E. coli lacking specific protective systems were tested against AgNp. Deletion mutants lacking silver ion efflux systems and resistance mechanisms against oxidative stress showed an increased sensitivity to AgNp. However, the bioreporter did not respond to silver nanoparticles. Our results suggest that oxidative stress is a major toxicity mechanism and that this is at least partially associated with ionic silver, but that bulk dissolution of silver into the medium is not sufficient to account for the observed effects. Chloride ions do not appear to offer significant protection, indicating that chloride in receiving waters will not necessarily protect environmental bacteria from the toxic effects of nanoparticles in effluents.

Characterization and antibacterial activity of silver nanoparticles prepared with a fungal exopolysaccharide in water

This work demonstrates a simple and feasible approach for the synthesis of silver nanoparticles (AgNPs) in water with a high molecular weight (MW) exopolysaccharide fraction, EPS1 produced by a medicinal fungus Cs-HK1. The formation and properties of AgNPs were evaluated at various temperatures, time periods, and silver nitrate/EPS1 concentrations in water. At suitable conditions (100 °C, 60 min and 10 mM AgNO3 with 1.0 mg/mL EPS1), AgNPs were formed with an average diameter of 50 nm and a narrow size distribution, remaining as a stable dispersion for at least 2 months. EPS1 may be acting as a reducing and stabilizing agent for the formation of AgNPs, which were attached to the hydroxyl groups of EPS1. The AgNPs formed in EPS1 solution exhibited a concentration-dependent inhibition of both Gram-negative and -positive bacteria but a very low cytotoxicity on the RAW264.7 murine macrophage cells. The results demonstrated the feasibility for green synthesis of AgNPs as potential antibacterial agents using natural polysaccharides dissolved in water.

Biochemical Evaluation and Green Synthesis of Nano Silver Using Peroxidase fromEuphorbia(Euphorbia amygdaloides) and Its Antibacterial Activity

Silver nanoparticles are used an increased attention for various biomedical and medical applications. In this study, green synthesis of silver nanoparticles was made with simple method by using peroxidase enzyme partially purified fromEuphorbia(Euphorbia amygdaloides) plant. Optimum pH, temperature and time period were determined to obtain silver nanoparticles using the peroxidase enzyme. The result shows that higher silver nanoparticle was synthesized for 4 hours and at 20°C and pH 8. Also, optimal concentration of metal ions was found as 0.5 mM. The synthesized silver nanoparticles were characterized by UV spectrum, scanning electron microscope (SEM) and X-ray diffraction. Antibacterial activity of silver nanoparticles was measured against some microorganisms such asSerratia marcescens, Yersinia pseudotuberculosis, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Pseudomonas aeruginosa, Salmonella typhimurium, Listeria monocytogenes, and Escherichia coli. Synthesized silver nanoparticles have wide spectrum antibacterial activity in low concentration and may be a good alternative therapeutic approach in medicine and pharmaceutical fields in future.

Enhanced catalytic and antibacterial activities of silver nanoparticles immobilized on poly(N-vinyl pyrrolidone)-grafted graphene oxide

PNVP grafted on GO regulates the size of Ag nanoparticles and enhances the catalytic and antibacterial properties along with increase in the dispersibility of GO.

Comparative Evaluation of Antibacterial Activity of Silver Nanoparticles Biosynthesized Using Fruit Juices

Synthesis of nanosized particles with antimicrobial property is of significance in therapeutic applications of nanotechnology. The present study reports an environmental friendly and rapid method for biosynthesis of silver nanoparticles and their antibacterial activity. This green synthetic method used various fruit juices like sweet lime, lime and orange as a reducing and capping agent for silver nitrate. Different thermal reduction methods-microwave oven and hot plate were used for synthesizing silver nanoparticles. The silver ions were reduced into silver nanoparticles within few minutes of reaction. Silver nanoparticles so prepared were characterized using UV–visible spectrophotometer and scanning electron microscope. An effort was also been made to predict the size of the silver nanoparticles using UV-visible spectra by Mie Scattering protocol. Scanning electron micrograph (SEM) revealed useful information about the morphology of silver nanoparticles. The synthesized silver nanoparticles showed antibacterial property against pathogenic bacteria Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae and Staphylococcus aureus. Agar well diffusion method was adopted to assay the nanoparticles for bactericidal activity against test organisms on nutrient agar plates. Silver nanoparticles biosynthesized from orange fruit juice were more effective as antibacterial agent. The maximum zones of inhibition of 8.0 mm, 6.0 mm, 8.0 mm and 5.0 mm were observed against Escherichia coli, Salmonella typhi, Klebsiella pneumoniae and Staphylococcus aureus respectively. The study shows that gram negative bacteria are more susceptible to antibacterial action of silver nanoparticles. Such studies are crucial in the demonstration of therapeutic importance of silver nanoparticles.

Green Synthesis, Catalytic and Antibacterial Activity of Silver Nanoparticles Synthesized from Olax acuminata

Green Synthesis, Catalytic and Antibacterial Activity of Silver Nanoparticles Synthesized from Olax acuminata

Templating effect of 1,5-disubstituted 1,2,3-triazole-linked disaccharides on size, shape and antibacterial activity of silver nanoparticles

1,5-Disubstituted 1,2,3-triazole (1,5-DT) linked disaccharides were used in the modified Tollens method for the synthesis and stabilization of silver nanoparticles (AgNPs) for the first time. The templating effect of the triazole ring is evident from the spectral data. Unlike the naturally occurring disaccharides these disaccharides are stable and the formation of the corresponding dicarboxylate was established. AgNPs obtained from one of the disaccharides showed promising antimicrobial activity. The formation, shapes and antimicrobial activity of the AgNPs strongly depend on the molecular structure of the 1,5-DTs used.