Biosynthesis of silver nanoparticles using Bacillus subtilis EWP-46 cell-free extract and evaluation of its antibacterial activity

This study highlights the ability of nitrate-reducing Bacillus subtilis EWP-46 cell-free extract used for preparation of silver nanoparticles (AgNPs) by reduction of silver ions into nano silver. The production of AgNPs was optimized with several parameters such as hydrogen ion concentration, temperature, silver ion (Ag⁺ ion) and time. The maximum AgNPs production was achieved at pH 10.0, temperature 60 °C, 1.0 mM Ag⁺ ion and 720 min. The UV–Vis spectrum showed surface plasmon resonance peak at 420 nm, energy-dispersive X-ray spectroscopy (SEM–EDX) spectra showed the presence of element silver in pure form. Atomic force microscopy (AFM) and transmission electron microscopy images illustrated the nanoparticle size, shape, and average particle size ranging from 10 to 20 nm. Fourier transform infrared spectroscopy provided the evidence for the presence of biomolecules responsible for the reduction of silver ion, and X-ray diffraction analysis confirmed that the obtained nanoparticles were in crystalline form. SDS-PAGE was performed to identify the proteins and its molecular mass in the purified nitrate reductase from the cell-free extract. In addition, the minimum inhibitory concentration and minimum bactericidal concentration of AgNPs were investigated against gram-negative (Pseudomonas fluorescens) and gram-positive (Staphylococcus aureus) bacteria.     

Biosynthesis of silver nanoparticles by natural precursor from clove and their antimicrobial activity

Silver nanoparticles (AgNPs) have attracted the attention of researchers because of their unique properties and applications in various fields, such as medicine, catalysis, textile engineering, and pollution treatment. The green synthesis of AgNPs has many advantages, such as less time requirement, highly stable AgNPs, better control over crystal growth, morphology, ease for scale up, and economic viability. Syzygium aromaticum (clove) was used for the extracellular biosynthesis of AgNPs. Eugenols are the active biomolecules present in clove, responsible for the bioreduction of AgNO₃ (Ag⁺) leading to the formation and capping of AgNPs (Ag⁰). One molecule of eugenol releases two electrons and these two electrons will be taken by 2 Ag⁺ ions and these will get reduced to 2 Ag⁰. The synthesis of AgNPs was confirmed by the appearance of brown colour. The synthesized AgNPs were characterised by various techniques, such as UV-VIS spectroscopy, transmission electron microscopy, X-ray diffraction and Fourier transformed infrared spectroscopy. The synthesised AgNPs have λ _max of 440 nm. It was evaluated that the AgNPs were biphasic in nature (cubic + hexagonal) with an average size of 50.0 nm. The synthesized AgNPs showed significant antimicrobial activity against Bacillus cereus NCDC 240 as they are nano-sized and have high surface area to volume ratio. AgNPs inhibit the growth of bacteria by various ways, such as by disrupting the cell membrane of bacteria, uncoupling the oxidative phosphorylation, inhibiting the DNA replication, forming free radicals and affecting the cellular signalling of bacteria leading to cell death.     

Experimental evolution of Pseudomonas putida under silver ion versus nanoparticle stress

Whether the antibacterial properties of silver nanoparticles (AgNPs) are simply due to the release of silver ions (Ag⁺) or, additionally, nanoparticle-specific effects, is not clear. We used experimental evolution of the model environmental bacterium Pseudomonas putida to ask whether bacteria respond differently to Ag⁺ or AgNP treatment. We pre-evolved five cultures of strain KT2440 for 70 days without Ag to reduce confounding adaptations before dividing the fittest pre-evolved culture into five cultures each, evolving in the presence of low concentrations of Ag⁺, well-defined AgNPs or Ag-free controls for a further 75 days. The mutations in the Ag⁺ or AgNP evolved populations displayed different patterns that were statistically significant. The non-synonymous mutations in AgNP-treated populations were mostly associated with cell surface proteins, including cytoskeletal membrane protein (FtsZ), membrane sensor and regulator (EnvZ and GacS) and periplasmic protein (PP_2758). In contrast, Ag⁺ treatment was selected for mutations linked to cytoplasmic proteins, including metal ion transporter (TauB) and those with metal-binding domains (ThiL and PP_2397). These results suggest the existence of AgNP-specific effects, either caused by sustained delivery of Ag⁺ from AgNP dissolution, more proximate delivery from cell-surface bound AgNPs, or by direct AgNP action on the cell's outer membrane.     

The effects of silver ions and silver nanoparticles on cell division and expression of <Emphasis Type="Italic">cdc2</Emphasis> gene in <Emphasis Type="Italic">Allium cepa</Emphasis> root tips

The effects of silver nanoparticles (AgNPs), silver ions (Ag⁺), and polyvinylpyrrolidone (PVP) on mitosis and expression of a gene encoding cyclin-dependent kinase 2 (cdc2) in onion roots were compared. Three concentrations (5, 10, and 15 mg dm^-3) were employed in combination with three incubation times (3, 6, and 9 h). PVP enhanced mitotic index and cdc2 expression. Both silver forms decreased mitotic index and cdc2 expression. Genotoxicity of both silver forms were indicated by three major distinguishable classes of chromosome aberrations: spindle disturbances, clastogenic aberrations, and chromosome stickiness. Concerning Ag⁺ treatments, significant enhancements in occurrence of any chromosome aberration type was associated with significant decrease in mitotic index. On the other hand, disturbed spindle in AgNPs treatments was observed even in absence of significant reduction in mitotic index suggesting that AgNPs inhibit cellular events occurring during mitosis to proceed normally rather than starting of cell division.     

Is there a way to protect human immune cells against nanocytotoxicity?

The silver nanoparticles (AgNPs) prepared by chemical reduction with sodium hypophosphite as a reducing agent and sodium hexametaphosphate as a stabilising agent were highly cytotoxic against human cells (U-937 and HL-60). The aim of the study was to determine the impact of selected antioxidants: ascorbic acid (AA), gallic acid (GA), scavenger (trolox (TX)) and Ag⁺ chelator (N-acetylcysteine, NAC) on viability, modulation of inflammatory response and apoptosis index of cells treated by AgNPs. Selected protectants added individually or together affects the viability of cells treated by AgNPs (1?mg/L). The mixtures assuring the most efficient defense against AgNPs were: AgNPs?+?TX?+?AA, AgNPs?+?GA?+?AA, AgNPs?+?TX?+?GA?+?AA and AgNPs?+?TX?+?GA?+?AA?+?NAC which synergistically interact in the mixture. The greatest reduction in IL-6 and TNF-α levels was found for the mixture containing AgNPs?+?TX?+?GA?+?AA. Mixture of this composition exhibited also the strongest anti-apoptotic effect. Highly cytotoxic AgNPs may not damage human cells if cytoprotectants are present.     

Nano silver entrapped in phospholipids membrane: Synthesis,characteristics and antibacterial kinetics

Abstract

The antimicrobial property of stabilized silver nanoparticles (AgNPs) with phospholipid membrane was investigated on both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterial strains. The influence of phospholipid concentrations on antibacterial kinetics actions of AgNPs was studied with two different methodologies in order to understand the bactericidal and bacteriostatic effects. The bacterial inactivation of synthesized AgNPs fitted well to the Chick-Watson model with a high regression coefficient, R² > 0.91. The antibacterial properties of AgNPs depend on the particle size, stabilizer and lecithin concentrations. Only the stabilized AgNPs that have the K_lec/Ag values of 1 and 2 presented the inhabitation zone, while unstabilized AgNPs agglomerated quickly, settled on the wells and did not diffuse in agar. In addition, the specific coefficient of lethality depends on the lecithin concentration. An increase in lecithin concentration caused multilayer creation on the AgNPs' surface and reduced the release of AgNPs which led to low bacterial killing rate.     

Extracellular biosynthesis of silver nanoparticles using a novel and non-pathogenic fungus,Neurospora intermedia: controlled synthesis and antibacterial activity

In the present study, the biosynthesis of silver nanoparticles (AgNPs) using Neurospora intermedia, as a new non-pathogenic fungus was investigated. For determination of biomass harvesting time, the effect of fungal incubation period on nanoparticle formation was investigated using UV–visible spectroscopy. Then, AgNPs were synthesized using both culture supernatant and cell-free filtrate of the fungus. Two different volume ratios (1:100 and 1:1) of the culture supernatant to the silver nitrate were employed for AgNP synthesis. In addition, cell-free filtrate and silver nitrate were mixed in presence and absence of light. Smallest average size and highest productivity were obtained when using equal volumes of the culture supernatant and silver nitrate solution as confirmed by UV–visible spectra of colloidal AgNPs. Comparing the UV–visible spectra revealed that using cell-free filtrate for AgNP synthesis resulted in the formation of particles with higher stability and monodispersity than using culture supernatant. The absence of light in cell-free filtrate mediated synthesis led to the formation of nanoparticles with the lowest rate and the highest monodispersity. The presence of elemental silver in all prepared samples was confirmed using EDX, while the crystalline nature of synthesized particles was verified by XRD. FTIR results showed the presence of functional groups which reduce Ag⁺ and stabilize AgNPs. The presence of nitrate reductase was confirmed in the cell-free filtrate of the fungus suggesting the potential role of this enzyme in AgNP synthesis. Synthesized particles showed significant antibacterial activity against E. coli as confirmed by examining the growth curve of bacterial cells exposed to AgNPs.     

Toxicity of biosynthetic silver nanoparticles on the growth,cell ultrastructure and physiological activities of barley plant

Silver nanoparticles (AgNPs) were biosynthesized using the cell-free filtrate of bacterium Proteus mirabilis, reacted with 1 mM of AgNO₃ solutions at 37 °C. The synthesis of AgNPs was monitored by UV–Vis spectroscopy and transmission electron microscopy (TEM) equipped with selected area electron diffraction (SAED). The results point to formation of spherical to cubical particles of AgNPs ranging in size from 5 to 35 nm with an average of 25 nm in diameter. The toxicity of Ag on barley (Hordeum vulgare L. cv. Gustoe) that was subjected to Ag⁺ as AgNO₃ and AgNPs was explored. The grain germination and seedling growth of barley decreased in the presence of 0.1 mM Ag⁺ and was inhibited at 1 mM Ag⁺. In contrast, our results indicated that the AgNPs at low concentration (0.1 mM) could be useful for barley grain germination and seedling growth. However, the higher concentrations of AgNPs (0.5 and 1 mM) reduced grain germination and exhibited a stronger reduction in the root length. A decline in the photosynthetic pigments and disorganization of chloroplast grana thylakoids in Ag⁺ and AgNPs-treated plants confirmed the leaf chlorosis. An increase of plastoglobuli within chloroplasts was observed in Ag⁺ and AgNPs-treated leaves. Ag⁺ caused dense aggregation of nuclear chromatin materials and degeneration of mitochondria. Ag⁺ and AgNPs increased contents of malondialdehyde, soluble proteins, total phenolic compounds and activity of guaiacol peroxidase in barley leaves; these results point to activation of plant defence mechanisms against oxidative stress in barley.     

Green synthesis and antibacterial effects of aqueous colloidal solutions of silver nanoparticles using camomile terpenoids as a combined reducing and capping agent

Green synthesis method using camomile extract was applied to synthesize silver nanoparticles to tune their antibacterial properties merging the synergistic effect of camomile and Ag. Scanning transmission electron microscopy revealed that camomile extract (CE) consisted of porous globular nanometer sized structures, which were a perfect support for Ag nanoparticles. The Ag nanoparticles synthesized with the camomile extract (AgNPs/CE) of 7 nm average sizes, were uniformly distributed on the CE support, contrary to the pure Ag nanoparticles synthesized with glucose (AgNPs/G), which were over 50 nm in diameter and strongly agglomerated. The energy dispersive X-ray spectroscopy chemical analysis showed that camomile terpenoids act as a capping and reducing agent being adsorbed on the surface of AgNPs/CE enabling their reduction from Ag⁺ and preventing them from agglomeration. Fourier transform infrared and ultraviolet–visible spectroscopy measurements confirmed these findings, as the spectra of AgNPs/CE, compared to pure CE, did not contain the 1109 cm^?1 band, corresponding to –C–O groups of terpenoids and the peaks at 280 and 320 nm, respectively. Antibacterial tests using four bacteria strains showed that the AgNPs/CE performed five times better compared to CE AgNPs/G samples, reducing totally all the bacteria in 2 h.     

Hormesis Effects of Silver Nanoparticles at Non-Cytotoxic Doses to Human Hepatoma Cells

Silver nanoparticles (AgNPs) have attracted considerable attentions due to their unique properties and diverse applications. Although it has been reported that AgNPs have acute toxic effects on a variety of cultured mammalian cells and animal models, few studies have been conducted to evaluate the associated risk of AgNPs to human health at non-cytotoxic doses. In this paper, HepG2 cells were exposed to 10 nm and 100 nm AgNPs under non-cytotoxic conditions, and cell viability was assessed. At low doses, AgNPs displayed “hormesis” effects by accelerating cell proliferation. Further studies indicated that the activation states of MAPKs were differentially regulated in this process. Specifically, by increasing the expression of downstream genes, p38 MAPK played a central role in non-cytotoxic AgNP-induced hormesis. Moreover, the treatment of HepG2 cells with silver ions (Ag⁺) at the same dose levels induced distinct biological effects, suggesting that different intrinsic properties exist for AgNPs and Ag⁺.     

Influence of outer membrane c‐type cytochromes on particle size and activity of extracellular nanoparticles produced by Shewanella oneidensis

The metal‐reducing bacterium Shewanella oneidensis is capable of reducing various metal(loid)s and produces nanoparticles (NPs) extracellularly, in which outer membrane c‐type cytochromes (OMCs) have been suggested to play important roles. The objective of this study was to investigate the influence of the OMCs, that is, MtrC and OmcA, on the size and activity of the extracellular silver NPs (AgNPs) and silver sulfide NPs (Ag₂S NPs) produced by S. oneidensis MR‐1. We found that (i) the lack of OMCs on S. oneidensis cell surface decreased the particle size of the extracellular biogenic AgNPs and Ag₂S NPs; (ii) the biogenic AgNPs from the mutant lacking OMCs showed higher antibacterial activity; and (iii) the biogenic Ag₂S NPs from the mutant lacking OMCs exhibited higher catalytic activity in methylviologen reduction. The results suggest that it may be possible to control particle size and activity of the extracellular biogenic NPs via controlled expression of the genes encoding surface proteins. In addition, we also reveal that in extracellular biosynthesis of NPs the usually neglected non‐cell‐associated NPs could have high catalytic activity, highlighting the need of novel methods that can efficiently retain extracellular NPs in the biosynthesis processes. Biotechnol. Bioeng. 2013; 110: 1831–1837. © 2013 Wiley Periodicals, Inc.     

Biosynthesis and characterization of silver nanoparticles produced by Pleurotus ostreatus and their anticandidal and anticancer activities

The biosynthesis of nanoparticles has received increasing interest because of the growing need to develop safe, cost-effective and environmentally friendly technologies for the synthesis of nano-materials. In this study, silver nanoparticles (AgNPs) were synthesized using a reduction of aqueous Ag⁺ ions with culture supernatant from Pleurotus ostreatus. The bioreduction of AgNPs was monitored by ultra violet-visible spectroscopy and the obtained AgNPs were characterized by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy techniques. TEM studies showed the size of the AgNPs to be in the range of 4–15 nm. The formation of AgNPs might be an enzyme-mediated extracellular reaction process. Furthermore, the antifungal effect of AgNPs against Candida albicans as compared with commercially antifungal drugs was examined. The effect of AgNPs on dimorphic transition of C. albicans was tested. The anticancer properties of AgNPs against cells (MCF-7) were also evaluated. AgNPs caused a significant decrease in cell viability of an MCF-7 cell line (breast carcinoma). Exposure of MCF-7 cells with AgNPs resulted in a dose-dependent increase in cell growth inhibition varying from 5 to 78 % at concentrations in the range of 10–640 μg ml^?1. The present study demonstrated that AgNPs have potent antifungal, antidimorphic, and anticancer activities. The current research opens a new avenue for the green synthesis of nano-materials.     

Hybrid nanofibrous yarns based on N-carboxyethylchitosan and silver nanoparticles with antibacterial activity prepared by self-bundling electrospinning

Hybrid nanofibrous materials with antibacterial activity consisting of yarns from N-carboxyethylchitosan (CECh) and poly(ethylene oxide) (PEO) that contain 5 wt % or 10 wt % silver nanoparticles (AgNPs) were prepared. This was achieved by electrospinning using formic acid as a solvent and as a reducing agent for silver ions. AgNO₃ was used as an Ag⁺-containing salt. Its concentration was selected to be 0.02 mol/L or 0.04 mol/L in order the content of the AgNPs in the electrospun nanofibers to be 5 wt % or 10 wt %, respectively. The self-bundling of the fibers into yarns with a mean diameter of ca. 35 μm was enabled only by using a grounded needle electrode. The reduction of the silver ions to an elemental silver was evidenced by UV-vis spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The transmission electron microscopy (TEM) analyses revealed that AgNPs formed at AgNO₃ concentration of 0.02 mol/L were with a mean diameter of 4 ± 0.5 nm and were distributed uniformly within the fiber. The increase of AgNO₃ concentration to 0.04 mol/L led to the preparation of AgNPs with a higher mean diameter and a broader diameter distribution as well as to aggregate formation. The performed studies on the antibacterial activity of CECh/PEO/AgNPs fibrous materials against Staphylococcus aureus showed that at AgNPs content of 5 wt % the mats had bacteriostatic, and at AgNPs content of 10 wt %—bactericidal activity.     

Estuarine sediment hydrocarbon-degrading microbial communities demonstrate resilience to nanosilver

Little is currently known about the potential impact of silver nanoparticles (AgNPs) on estuarine microbial communities. The Colne estuary, UK, is susceptible to oil pollution through boat traffic, and there is the potential for AgNP exposure via effluent discharged from a sewage treatment works located in close proximity. This study examined the effects of uncapped AgNPs (uAgNPs), capped AgNPs (cAgNPs) and dissolved Ag₂SO₄, on hydrocarbon-degrading microbial communities in estuarine sediments. The uAgNPs, cAgNPs and Ag₂SO₄ (up to 50 mg L⁻¹) had no significant impact on hydrocarbon biodegradation (80–92% hydrocarbons were biodegraded by day 7 in all samples). Although total and active cell counts in oil-amended sediments were unaffected by silver exposure; total cell counts in non-oiled sediments decreased from 1.66 to 0.84 × 10⁷ g⁻¹ dry weight sediment (dws) with 50 mg L⁻¹ cAgNPs and from 1.66 to 0.66 × 10⁷ g⁻¹ dws with 0.5 mg L⁻¹ Ag₂SO₄ by day 14. All silver-exposed sediments also underwent significant shifts in bacterial community structure, and one DGGE band corresponding to a member of Bacteroidetes was more prominent in non-oiled microcosms exposed to 50 mg L⁻¹ Ag₂SO₄ compared to non-silver controls. In conclusion, AgNPs do not appear to affect microbial hydrocarbon-degradation but do impact on bacterial community diversity, which may have potential implications for other important microbial-mediated processes in estuaries.     

Evaluation of the interaction between proliferation,oxidant–antioxidant status,Wnt pathway,and apoptosis in zebrafish embryos exposed to silver nanoparticles used in textile industry

Antimicrobial textile products are developing rapidly as an important part of functional textiles. Silver nanoparticles (AgNPs) are nanotechnology products with antimicrobial properties. However, exposure to nanoparticles in daily life is an important issue for public health, still being updated. Aim was to evaluate the effects of AgNPs on the development of zebrafish embryos focusing on Wnt pathway, proliferation, oxidant–antioxidant status, and apoptosis. The expressions of ccnd1 and gsk3β were determined by RT‐PCR, whereas β‐catenin and proliferative cell antigen (PCNA) expressions were determined immunohistochemically. Lipid peroxidation, superoxide dismutase, and glutathione‐S‐transferase activities were determined spectrophotometrically. Apoptosis was determined using acridine orange staining. Oxidant status, apoptosis, immunohistochemical PCNA, and β catenin staining increased, whereas ccnd1 and antioxidant enzyme activities decreased in AgNPs‐exposed embryos in a dose‐dependent manner. Our results indicate the interaction of possible mechanisms that may be responsible for the toxic effects of AgNPs in zebrafish embryos.     

Biocidal properties of maltose reduced silver nanoparticles against American foulbrood diseases pathogens

Bee disease caused by spore-forming Paenibacillus larvae and Paenibacillus alvei is a serious problem for honey production. Thus, there is an ongoing effort to find an effective agent that shows broad biocidal activity with minimal environmental hazard. In this study, the biocidal effect of maltose reduced silver nanoparticles (AgNPs) is evaluated against American foulbrood and European foulbrood pathogens. The results demonstrate that the maltose reduced AgNPs are excellent short and long-term biocides against P. larvae isolates. The long-term effect suggests that the Ag⁺ ions are released from the AgNPs with increasing time in a controlled manner.     

Bioaccumulation of silver by a multispecies community of bacteria

A stable community of bacteria that had unusually high tolerance of soluble silver was isolated from soil by chemostat enrichment. The community consisted of three bacteria: Pseudomonas maltophilia, Staphylococcus aureus and a coryneform organism. The pseudomonas was primarly responsible for the silver resistance. The tolerance of high silver concentrations, up to 100 mM Ag⁺, was greatly reduced when the community was grown in the absence of silver. Pseudomonas maltophilia comprised approximately 50% by numbers of the community when grown in chemostats in the presence or absence of Ag⁺ but large fluctuations occurred in population sizes of the other two bacteria; the S. aureus population was small (less than 1%) in the presence of Ag⁺ but comparised a third of the total numbers when Ag⁺ was omitted from the medium. Silver-resistant respiration of the silveradapted community was significant even when it was confronted with high concentrations of Ag⁺. In contrast the respiration of the coryneform organism and particularly S. aureus was highly sensitive to silver. The inhibition constants for silver-sensitive respiration were 0.78 mM and 0.04 mM for silver acclimatized and nonacclimatized communities respectively.The community had great capacity for silver bioaccumulation. Maximum concentrations of over 300 mg silver per g dry weight of biomass were recorded at an accumulation rate of 21 mg Ag⁺ h^-1 (g biomass)^-1. The extent of silver removal from solution was a function of initial concentration of silver; at low external concentrations (ca. 1 mM) all the silver was rapidly removed from solution, at high concentrations (ca. 12 mM) 84% removal occurred in 15 h.     

A comparative life cycle assessment of commercially available household silver-enabled polyester textiles

Purpose

Silver-enabled textiles use the inherent antimicrobial properties of silver to produce a product with odor reduction capabilities. A touted benefit of these products is the ability to reduce their lifetime environmental impact through reductions in laundering. A comprehensive life cycle assessment is needed to fully understand the potential benefit of reduced laundering, environmental payback period, and potential to shift consumer-laundering behavior.

Methods

Three commercially available silver-enabled polyester fabrics are compared to a conventional fabric using life cycle assessment methodology. Sima Pro software along with the Tool for Reduction and Assessment of Chemicals and Other Environmental Impacts (TRACI) impact categories are used to model the environmental impact of the four textiles (three with added silver, and one conventional textile) throughout their lifetimes. Environmental payback is used to determine the number of reductions of launderings necessary for environmental benefit to be realized from the inclusion of silver. Current literature on laundering motivations and habits is reviewed to yield insight on whether there is the potential for consumers to launder their textiles less frequently.

Results and discussion

The lifetime environmental impact of the three textiles considered varies as a function of the silver content and environmental impact category. In some impact categories, such as global warming potential, the laundering phase has the greatest environmental impact and thus has the potential for the greatest reduction. In other categories, such as ecotoxicity, the most significant impact is due to the percentage of silver that is released into surface water from the textile. In this case, environmental parity (the point at which the environmental impacts are the same) is not always possible to achieve. A review of the literature suggests that the motivation to launder textiles along with the frequency varies significantly across populations and times in history.

Conclusions

Silver-enabled textiles have the potential to reduce the odors produced by unwashed textiles through bacterial inhibition. In some cases, there is the potential to achieve adequate reductions in laundering to compensate for the increased energy and raw materials needed to produce silver-enabled textile. However, frequency of laundering is largely a cultural norm based on perceived cleanliness and is unlikely to be shifted as a function of textile adoption.

     

Synergistic Antibacterial Efficiency of Bacteriocin and Silver Nanoparticles Produced by Probiotic Lactobacillus paracasei Against Multidrug Resistant Bacteria

Contamination of wounds with multidrug-resistant microorganisms is one of the greatest challenges in the curing of many diseases, and therefore, the search for alternative antimicrobial agents becomes urgent. In the present study, out of 280 bacterial isolates recovered from 57 wound swabs of patients, 199 isolates (71.1%) showed multiple drug resistance (MDR). Staphylococcus aureus was the most predominant (80.0%), followed by Pseudomonas aeuroginosa (78.87%). A number of 121 isolates (60.80%) of MDR was sensitive to bacteriocin produced by a probiotic strain of Lactobacillus paracasei. However, considering that bacteriocins may be degraded before reaching its target, silver nanoparticles (AgNPs) can be used as a suitable candidate for combinations with bacteriocin in order to be more effective. AgNPs were synthesized using the same strain and then characterized by UV–Vis spectroscopy, TEM and XRD analyses. Bacteriocin/AgNPs bioconjugate exhibited a higher antibacterial efficiency against MDR strains than that of bacteriocin or AgNPs alone. Interestingly, the bioconjugate has significantly increased the disruption of cell membrane permeability, leakages of protein and DNA, in addition to the formation of bactericidal reactive oxygen species than any other extracts. Therefore, the combination of bacteriocin with metal nanoparticles is recommended as a promising approach for the elimination of MDR organisms.

     

Phyto-synthesis of silver nanoparticles using <Emphasis Type="Italic">Alternanthera tenella</Emphasis> leaf extract: an effective inhibitor for the migration of human breast adenocarcinoma (MCF-7) cells

In this study, phyto-synthesis of silver nanoparticles (AgNPs) was achieved using an aqueous leaf extract of Alternanthera tenella. The phytochemical screening results revealed that flavonoids are responsible for the AgNPs formation. The AgNPs were characterised using UV–visible spectrophotometer, field emission scanning microscopy/energy dispersive X-ray, transmission electron microscopy, fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction. The average size of the nanoparticles was found to be ≈48 nm. The EDX results show that strong signals were observed for the silver atoms. The strong band appearing at 1601–1595 cm^?1 correspond to C–C stretching vibration from dienes in FT-IR spectrum indicating the formation of AgNPs. Human breast adenocarcinoma (MCF-7) cells treated with various concentrations of AgNPs showed a dose-dependent increase in cell inhibition. The IC₅₀ value of the AgNPs was calculated to be 42.5 μg mL^?1. The AgNPs showed a significant reduction in the migration of MCF-7 cells.