木霉菌合成银纳米粒子条件的优化及其对甜瓜尖孢镰刀菌抑制作用

随着绿色环保观念的普及,生物合成金属纳米粒子的方法备受青睐。纳米银(Silver nanoparticles,AgNPs)由于其抗菌活性强且不易产生抗药性等特点在农业病害防治中越来越受到关注。文中利用橘绿木霉Trichoderma citrinoviride和毛簇木霉Trichoderma velutinous研究了AgNPs的最适合成条件和AgNPs对尖孢镰刀菌抑菌活性。结果表明,所有合成的AgNPs均在400–500 nm处有吸收峰,两种木霉生物合成AgNPs的最适合成条件为CL法(菌丝滤液)静置光照培养,底物AgNO₃浓度为2.0mmol/L,pH值为7,反应温度为45℃。橘绿木霉和毛簇木霉合成的AgNPs均对尖孢镰刀菌有抑制作用,抑菌效果随浓度的增加而增大,AgNPs在浓度为200 mg/L时,抑菌率分别达到33.745%和36.083%。     

Biosynthesis of silver nanoparticles using novel Bacillus sp. SBT8

Biosynthesis of silver nanoparticles (AgNPs) using microorganisms is an important application of nanobiotechnology and green chemistry because of interest by pharmaceutical and food manufacturers. In this study, biosynthesis of AgNPs by a novel Bacillus strain isolated from a soil sample from Sakarya district in Turkey was investigated. Biosynthesis was performed using cell-free supernatant of the bacterium following 24?h growth. Effects of varying AgNO₃ concentration (1–10?mM), pH (5–10), and temperature (30–40°C) on the synthesis of AgNPs were determined. Formation of AgNPs was monitored by UV–VIS spectroscopy. Field emission scanning electron microscopy was used to compare morphologies among the various culture conditions. The peaks created by surface plasmon resonance (SPR) of metals were obtained only at 4 and 6?mM AgNO₃ concentrations and the maximum concentration for the biosynthesis was observed at 6?mM. The highest yield was achieved at pH 10 and larger nanoparticles were obtained at this pH. The optimum temperatures for biosynthesis were 33 and 37°C. Fourier transform infrared spectroscopy analysis and transmission electron microcopy images confirmed that the proteins served as capping. Energy-dispersive spectroscopy analysis validated the formation of AgNPs. AgNPs exhibited antibacterial activity toward Gram-positive and Gram-negative pathogens.     

Application of statistical experimental design for optimization of silver nanoparticles biosynthesis by a nanofactory Streptomyces viridochromogenes

Central composite design was chosen to determine the combined effects of four process variables (AgNO₃ concentration, incubation period, pH level and inoculum size) on the extracellular biosynthesis of silver nanoparticles (AgNPs) by Streptomyces viridochromogenes. Statistical analysis of the results showed that incubation period, initial pH level and inoculum size had significant effects (P<0.05) on the biosynthesis of silver nanoparticles at their individual level. The maximum biosynthesis of silver nanoparticles was achieved at a concentration of 0.5% (v/v) of 1 mM AgNO₃, incubation period of 96 h, initial pH of 9 and inoculum size of 2% (v/v). After optimization, the biosynthesis of silver nanoparticles was improved by approximately 5-fold as compared to that of the unoptimized conditions. The synthetic process of silver nanoparticle generation using the reduction of aqueous Ag+ ion by the culture supernatants of S. viridochromogenes was quite fast, and silver nanoparticles were formed immediately by the addition of AgNO₃ solution (1 mM) to the cell-free supernatant. Initial characterization of silver nanoparticles was performed by visual observation of color change from yellow to intense brown color. UV-visible spectrophotometry for measuring surface plasmon resonance showed a single absorption peak at 400 nm, which confirmed the presence of silver nanoparticles. Fourier Transform Infrared Spectroscopy analysis provided evidence for proteins as possible reducing and capping agents for stabilizing the nanoparticles. Transmission Electron Microscopy revealed the extracellular formation of spherical silver nanoparticles in the size range of 2.15–7.27 nm. Compared to the cell-free supernatant, the biosynthesized AgNPs revealed superior antimicrobial activity against Gram-negative, Gram-positive bacterial strains and Candida albicans.     

绿色木霉菌合成金纳米颗粒的可能性及影响因素

【背景】金纳米颗粒(AuNPs)凭借其稳定性、抗氧化性能和生物相容性在许多领域有广泛应用。目前关于微生物合成金纳米颗粒的研究较少。【目的】对微生物合成金纳米颗粒的可能性以及影响因素进行探究,有利于揭示具体的合成机制,发现AuNPs的特性以及合成位置与菌丝和影响因素的关系。【方法】以绿色木霉菌(Trichoderma viride)菌株(GIM3.141)为菌种资源,通过目视检测法、紫外可见分光光度计、X射线衍射和透射电镜等手段分析合成AuNPs的特征。探讨细胞内生物合成金纳米颗粒(AuNPs)的可能性,研究生物量、初始金离子浓度、溶液pH等因素对细胞内合成AuNPs的影响。【结果】X射线衍射分析表明AuNPs以金纳米晶体形态存在。透射电镜分析表明AuNPs主要位于细胞壁膜间隙,一小部分附着在细胞壁上。紫外可见分光光度计分析表明,金纳米颗粒粒径随着生物量添加量和溶液pH的升高而变小,随着初始金离子浓度的升高而变大。【结论】非致病性真菌绿色木霉菌可以在细胞内合成AuNPs,其中包括伪球形、三角形、四边形和六边形等多种形状,粒径范围从几纳米到三百纳米,为大规模、低成本、无污染地生物合成纳米颗粒工艺提供了菌种资源。     

Exploring the Therapeutic Properties of Alga-Based Silver Nanoparticles: Anticancer,Antibacterial, and Free Radical Scavenging Capabilities

The current study was designed to evaluate the antioxidant, anticancer and antimicrobial activities of silver nanoparticles (AgNPs) biosynthesized by Spirulina platensis extract. The biosynthesized silver nanoparticles were characterized using Fourier transform infrared (FT-IR) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The antioxidant activity of the biosynthesized AgNPs were determined via DPPH radical scavenging assay while its anticancer activity was determined using the MTT assay. The antimicrobial activity of the biosynthesized AgNPs were analyzed by disc diffusion method. Spirulina platensis acts as a reducing and capping agent. The efficacy of silver nanoparticles (AgNPs) in inhibiting the growth of Gram-negative bacteria, specifically Acetobacter, Klebsiella, Proteus vulgaris, and Pseudomonas aeruginosa, was assessed by the utilisation of the diffusion method. The study aimed to evaluate the efficacy of biosynthesized silver nanoparticles (AgNPs) against many strains of Pseudomonas aeruginosa bacteria. The findings of the study revealed that when administered in doses of 50 μl, 75 μl, and 100 μl, the largest observed zone of inhibition corresponded to measurements of 10.5 mm, 14 mm, and 16 mm, respectively. A zone of inhibition with dimensions of 8 mm, 10.5 mm, and 12 mm was detected during testing against Acetobacter at concentrations of 50 μl, 75 μl, and 100 μl, respectively. The findings also indicate that there is a positive correlation between the concentration of AgNP and the DPPH scavenging ability of silver nanoparticles. The percentage of inhibition observed at concentrations of 500 μg/ml, 400 μg/ml, 300 μg/ml, 200 μg/ml, and 100 μg/ml were recorded as 80±1.98, 61±1.98, 52±1.5, 42±1.99, and 36±1.97, respectively. In addition, it was observed that the silver nanoparticles exhibited the greatest antioxidant activity at a concentration of 500 g/ml, with a measured value of 80.89±1.99. The IC-50 values, representing the inhibitory concentration required to achieve 50 % inhibition, were found to be 8.16, 19.15, 30.14, 41.13, and 63.11 at inhibition levels of 36±1.97, 42±1.99, 52±1.5, 61±1.98, and 80±1.98, respectively.     

Synthesis of biocompatible chitosan decorated silver nanoparticles biocomposites for enhanced antimicrobial and anticancer property

Numerous studies investigated the biosynthesis of silver nanoparticles (AgNPs); however, there is a large gap for the ideal time-consuming process and their cytotoxicity. Herein, for the first time, rapid AgNPs was synthesized in a short time span, using Piper betle leaf (PBL) extract by applying microwave exposure. PB-AgNPs antibacterial activity and cell compatibility were enhanced by capping with chitosan (CS@PB-AgNPs). The synthesized nanoparticles were characterized by bioanalytical techniques. PB-AgNPs expressed significant antibacterial activity against Gram-positive and Gram-negative bacterial pathogens, while hybrid CS@PB-AgNPs presented the enhanced bactericidal activity. In addition, PB-AgNPs exhibited IC₅₀ value of 140 μg/mL against RAW 264.7 macrophages and 100 μg/mL against lung cancer cells while, CS capping reduced its toxicity at IC₅₀ values of 400 μg/mL and 180 μg/mL respectively were affirmed by MTT, apoptosis and DNA damage detection. Overall it was demonstrated that CS capping could be a phenomenal finding to improve the biomedical potential of AgNPs.     

Extracellular biosynthesis,characterization, optimization of silver nanoparticles (AgNPs) using Bacillus mojavensis BTCB15 and its antimicrobial activity against multidrug resistant pathogens

Abstract

Biosynthesis of metal nanoparticles is an area of interest among researchers because of its eco-friendly approach. Current study focuses at biosynthesis of silver nanoparticles (AgNPs) and optimization of physico-chemical conditions to obtain mono-dispersed and stable AgNPs having antimicrobial activity. Initially Bacillus mojavensis BTCB15 produced silver nanoparticles (AgNPs) of 105?nm. Silver nanoparticles (AgNPs) were characterized by particle size analyzer, UV-Vis Spectroscopy, Fourier transforms infrared spectroscopy (FTIR), Atomic force microscopy (AFM), and X-ray diffraction (XRD). Whereas, under optimal conditions of temperature 55?°C, pH 8, addition of surfactant Tween 20, and metal ion K₂SO₄, about 104% size reduction was achieved with average size of 2.3nm. Molecular characterization revealed 98% sequence homology with Bacillus mojavensis. AgNPs exhibited antibacterial activity at concentrations ranging from 0.5 to 2.5?µg/µl against Escherichia coli BTCB03, Klebsiella pneumonia BTCB04, Acinetobacter sp. BTCB05, and Pseudomonas aeruginosa BTCB01 but none against Staphylococcus aureus BTCB02. Highest antibacterial activity was observed at 0.27?µg/µl and lowest at 0.05?µg/µl of AgNPs indicated by zone of inhibition. Conclusively, under optimum conditions, Bacillus mojavensis BTCB15 was able to produce AgNPs of 2.3?nm size and had antibacterial activity against multi drug resistant pathogens.     

Larvicidal activity of acetone extract and green synthesized silver nanoparticles from Allium sativum L. (Amaryllidaceae) against the dengue vector Aedes aegypti L. (Diptera: Culicidae)

Mosquito vectors of major human diseases are currently controlled using chemical and biological products. Extensive insecticide use has led to resistance development and human/environmental health risks, and alternative sustainable control options are needed; in this study, activity of an extract of garlic (Allium sativum; Amaryllidaceae), and silver nanoparticles (AgNPs) synthesized from the extract, were evaluated against 2nd and 3rd instar larvae of the yellow fever mosquito, Ae. aegypti (Diptera: Culicidae). Synthesis of AgNPs was confirmed using UV–Vis spectroscopy, and characterised using powdered X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Larvae were exposed to five concentrations (50, 100, 150, 200, 250 ppm) of garlic extract or synthesized AgNPs, with distilled water and silver nitrate solution (1 mM) as controls. The mortality of larvae was recorded after 6, 12, 24, 36, and 48 h following addition of the respective extracts.Dose- and time-dependent toxicity were recorded in both treatment groups with no mortality in control groups. Exposure to AgNPs at 250 ppm for 48 h yielded 100% mortality for both larval instars, with corresponding LC₅₀ values of 44.77 (2nd) and 62.82 ppm (3rd). Exposure to garlic extract resulted in similar 48-hour mortality (99 ± 0.77% (2nd) and 98 ± 1.10% (3rd), but consistently higher LC₅₀ values after all exposure times compared to AgNPs (e.g. 48-hour exposure: 108.42 ppm (2nd), 129.11 ppm (3rd), suggesting that AgNPs may potentially be used at lower concentrations for Ae. aegypti control.     

Development and evaluation of different strategies for the clean synthesis of silver nanoparticles using Yarrowia lipolytica and their antibacterial activity

An environment-friendly, cheap method, biogenic synthesis of silver nanoparticles (AgNPs) is interesting as compared to physical and chemical synthesis methods. The aim of the present study was to utilize the inherent capability of Yarrowia lipolytica as a novel biocatalyst for green production of AgNPs using different strategies, including growing cells, resting cells, and cell-free extracts (CFE) under optimized reaction conditions. The produced AgNPs were evaluated with UV–vis spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, and Fourier transform infrared spectrometry. In the growing cells strategy, Y. lipolytica produced spherical AgNPs under the optimized conditions, 2.5 mM of silver ions, 7.5 g/l of yeast biomass, a temperature of 30 °C, a pH of 6, and a shaking rate of 50 rpm after 48 h. The sizes and monodispersity of the AgNPs in the resting cells strategy were better than those in the other two. However, the AgNPs were produced faster in the CFE strategy. The antibacterial activity and minimal inhibitory concentration of the AgNPs against certain Gram-positive and Gram-negative bacteria were determined by the agar well diffusion and broth microdilution methods. The AgNPs had a considerable antibacterial effect compared to chloramphenicol as a broad-spectrum antibiotic.     

Ion exchange/complexation of the uranyl ion by Rhizopus biosorbent

Nonliving biomass of nine Rhizopus species effectively sequestered the uranyl ion from solution, taking up 150-250 mg U/g dry cells at 300 ppm U equilibrium concentration in solution, and 100-160 mg U/g dry cells with 100 ppm U in solution. The affinity of this biosorbent for the uranyl ion was found to be affected by timing of harvesting and medium composition. Uptake of the uranyl ion by nonliving biomass of Rhizopus oligosporus was due to ion exchange or complexation, since binding was reversed by the addition of complexing ligands or the reduction of pH to a value less than 2. Uptake isotherms were interpreted in terms of a model of multiple equilibria. At pH 相似文献   

Nutritional assessment study and role of green silver nanoparticles in shelf-life of coconut endosperm to develop as functional food

Tender coconut water is a pure and nutritious drink which play important role as nutraceuticals and pharmaceuticals contributes to the rapid growth of the functional food industry. In the mean-time the safety and shelf-life of the food is crucial for the both product as well as consumers. The intervention or application of nanotechnology gives immense a solution for the prolonged sustainability of the food products. This work reports on the nature of physiological changes of coconut liquid endosperm along with the interaction of its DNA with green route synthesized Ag nanoparticles (AgNPs) using Garuga pinnata leaf, an important ethnomedicinal plant. The physical and nutritional study of the coconut water were carried by UV–visible, XRD, NMR analysis whereas the synthesized Ag nanoparticles (AgNPs) were characterized by UV–Visible spectrophotometer, Raman Spectroscopy, DLS, AFM and FE-SEM analysis. The pH of the endosperm was found to decrease from 6.31 to 4.01, following an exponential decay trend and giving a decay constant of ~8.8 h. The broad absorption peak at ~310 nm gradually turns featureless with elapse of time. The proton nuclear magnetic resonance (H¹-NMR) spectrum essentially revealed the presence of esters or organic acids, confirming a sudden fall in the rate of intensity in the immature coconut endosperms as compared to the matured coconut cases. While the pentosyl methyl group (~1.4–1.5 ppm) concentration is observably lowered, free amino acid (~1 ppm) is apparently suppressed in the former specimen. Gel electrophoresis of 10 kb DNA with Ag nanoparticles (AgNPs) showed a gradual decrease of band intensity for a concentration varying between 3:1 and 1:1. The less intense band was due to the lack of migration of DNA into the micropores of the gel as a consequence of interaction of negatively charged DNA with negatively charged AgNPs. The study of DNA interaction with AgNPs could help identifying and addressing the nature of degradation process while considering prevention from microbial attack and make the coconut water as potential functional food entity.     

Green biosynthesis of silver nanoparticles from Annona squamosa leaf extract and its in vitro cytotoxic effect on MCF-7 cells

The biological method for the synthesis of silver nanoparticles (AgNPs) using Annona squamosa leaf extract and its cytotoxicity against MCF-7 cells are reported. The synthesized AgNPs using A. squamosa leaf extract was determined by UV–visible spectroscopy and it was further characterized by FT-IR, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Zeta potential and energy dispersive spectrometric (EDS) analysis. The UV–visible spectrum showed an absorption peak at 444 nm which reflects surface plasmon resonance (SPR) of AgNPs. TEM photography showed biosynthesized AgNPs were predominantly spherical in shape with an average size ranging from 20 to 100 nm. The Zeta potential value of ?37 mV revealed the stability of biosynthesized AgNPs. Furthermore, the green synthesized AgNPs exhibited a dose-dependent cytotoxicity against human breast cancer cell (MCF-7) and normal breast epithelial cells (HBL-100) and the inhibitory concentration (IC₅₀) were found to be 50 μg/mL, 30 μg/mL, and 80 μg/mL, 60 μg/ml for AgNPs against MCF-7 and normal HBL-100 cells at 24 h and 48 h incubation respectively. An induction of apoptosis was evidenced by (AO/EtBr) and DAPI staining. Application of such eco-friendly nanoparticles makes this method potentially exciting for the large scale synthesis of nanoparticles.     

Genotoxicity of silver nanoparticles evaluated using the Ames test and in vitro micronucleus assay

Silver nanoparticles (AgNPs) have antimicrobial properties, which have contributed to their widespread use in consumer products. A current issue regarding nanomaterials is the extent to which existing genotoxicity assays are useful for evaluating the risks associated with their use. In this study, the genotoxicity of 5 nm AgNPs was assessed using two standard genotoxicity assays, the Salmonella reverse mutation assay (Ames test) and the in vitro micronucleus assay. Using the preincubation version of the Ames assay, Salmonella strains TA102, TA100, TA1537, TA98, and TA1535 were treated with 0.15-76.8 μg/plate of the AgNPs. Toxicity limited the doses that could be assayed to 2.4-38.4 μg/plate; no increases in mutant frequency over the vehicle control were found for the concentrations that could be assayed. Human lymphoblastoid TK6 cells were treated with 10-30 μg/ml AgNPs, and additional cells were treated with water and 0.73 gy X-rays as vehicle and positive controls. Micronucleus frequency was increased by the AgNP treatment in a dose-dependent manner. At a concentration of 30 μg/ml (with 45.4% relative population doubling), AgNPs induced a significant, 3.17-fold increase with a net increase of 1.60% in micronucleus frequency over the vehicle control, a weak positive response by our criteria. These results demonstrate that the 5 nm AgNP are genotoxic in TK6 cells. Also, the data suggest that the in vitro micronucleus assay may be more appropriate than the Ames test for evaluating the genotoxicity of the AgNPs.     

Influence of temperature and pH on biomass production and protein biosynthesis in a putative Spirulina sp

The influence of temperature and pH on biomass production and protein biosynthesis in a Spirulina sp. isolated from an oil-polluted brackish water environment in the Niger Delta was studied. The isolated organism was identified on the basis of its phenotypic characteristics such as nature and direction of helix, temperature, pH and salt tolerance ranges. Biomass concentration in the culture media was calculated as cell dry weight. The combination of 30 degrees C and pH 9.0 gave the highest values of 4.9 mg/ml and 48.2g/100 g for biomass and total crude protein, respectively. The effect of pH was modulated by temperature and vice versa during biomass production. This native isolate of Spirulina sp. offers a good source of natural protein that could be easily accepted by rural communities as single cell protein in the form of feed, food and health supplement when properly processed.     

Comparison of Antimicrobial Properties of Silver Nanoparticles Synthesized from Selected Bacteria

Green silver nanoparticle (AgNP) biosynthesis is facilitated by the enzyme mediated reduction of Ag ions by plants, fungi and bacteria. The antimicrobial activity of green AgNPs is useful to overcome the challenge of antimicrobial resistance. Antimicrobial properties of biosynthesized AgNPs depend on multiple factors including culture conditions and the microbial source. The antimicrobial activity of AgNPs biosynthesized by Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Acinetobacter baumannii (confirmed clinical isolate) were investigated in this study. Biosynthesis conditions (AgNO₃ concentration, pH, incubation temperature and incubation time) were optimized to obtain the maximum AgNP yield. Presence of AgNPs was confirmed by observing a characteristic UV–Visible absorbance peak in 420–435 nm range. AgNP biosynthesis was optimal at 0.4 g/L AgNO₃ concentration under alkaline conditions at 60–70 °C. The biosynthesized AgNPs showed higher stability compared to chemogenized AgNPs in the presence of electrolytes. AgNPs synthesized by P. aeruginosa were the most stable while NPs of S. aureus were the least stable. AgNPs synthesized by P. aeruginosa and S. aureus showed good antimicrobial potential against E. coli, P. aeruginosa, S. aureus, MRSA and Candida albicans. AgNPs synthesized by S. aureus had greater antimicrobial activity. The antimicrobial activity of NPs may vary depending on the size and the morphology of NPs.     

Biosynthesis of gold and silver nanoparticles using Senna alexandrina Miller extract against Culex pipiens L. (Diptera: Culicidae)

The use of nanoparticles for various purposes, including pest control, has become increasingly popular because of their cost and environmental safety. In the present study, gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) were synthesized in an extract of Senna alexandrina Miller leaves with the aim of use against vectors of disease such as Culex pipiens L. (the filarial vector in Saudi Arabia). The nanoparticles were characterized by scanning electron microscopy and spectroscopic techniques. The larvicidal activity of the nanoparticles against Cx. pipiens was evaluated according to the protocol of the World Health Organization. According to the lethal concentration LC₅₀, the result shows differentiation in the sensitivity on mosquitoes. The AuNPs (51.383 ppm) the best one followed by AgNPs (52.525 ppm) while S. alexandrina leaf extract alone (355.25 ppm), the lowest effectiveness. Generally, the Cx. pipiens mosquito larvae proved to be more susceptible to AuNPs and AgNPs than leaf extract alone by about 6.91 and 6.76 times, respectively.     

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.     

Biofabricated Silver Nanoparticles Act as a Strong Fungicide against Bipolaris sorokiniana Causing Spot Blotch Disease in Wheat

The present study is focused on the extracellular synthesis of silver nanoparticles (AgNPs) using culture supernatant of an agriculturally important bacterium, Serratia sp. BHU-S4 and demonstrates its effective application for the management of spot blotch disease in wheat. The biosynthesis of AgNPs by Serratia sp. BHU-S4 (denoted as bsAgNPs) was monitored by UV–visible spectrum that showed the surface plasmon resonance (SPR) peak at 410 nm, an important characteristic of AgNPs. Furthermore, the structural, morphological, elemental, functional and thermal characterization of bsAgNPs was carried out using the X-ray diffraction (XRD), electron and atomic microscopies, energy dispersive X-ray (EDAX) spectrometer, FTIR spectroscopy and thermogravimetric analyzer (TGA), respectively. The bsAgNPs were spherical in shape with size range of ∼10 to 20 nm. The XRD and EDAX analysis confirmed successful biosynthesis and crystalline nature of AgNPs. The bsAgNPs exhibited strong antifungal activity against Bipolaris sorokiniana, the spot blotch pathogen of wheat. Interestingly, 2, 4 and 10 µg/ml concentrations of bsAgNPs accounted for complete inhibition of conidial germination, whereas in the absence of bsAgNPs, conidial germination was 100%. A detached leaf bioassay revealed prominent conidial germination on wheat leaves infected with B. sorokiniana conidial suspension alone, while the germination of conidia was totally inhibited when the leaves were treated with bsAgNPs. The results were further authenticated under green house conditions, where application of bsAgNPs significantly reduced B. sorokiniana infection in wheat plants. Histochemical staining revealed a significant role of bsAgNPs treatment in inducing lignin deposition in vascular bundles. In summary, our findings represent the efficient application of bsAgNPs in plant disease management, indicating the exciting possibilities of nanofungicide employing agriculturally important bacteria.     

Antibiofilm and antimicrobial activities of green synthesized silver nanoparticles using marine red algae Gelidium corneum

In our study, green synthesis of silver nanoparticles was carried out using a red algae Gelidium corneum extract as reducing agent. The obtained silver nanoparticles were characterized by UV–vis, TEM, XRD, FTIR and ICP-MS measurements. FTIR measurements indicated the possible functional groups responsible for the stabilization and reduction of nanoparticles, while XRD analysis results explained the crystalline structure of the particles with centric cubic geometry. TEM micrographs showed that the size of the nanoparticles was between 20–50 nm. According to the broth microdilution test results, AgNPs showed a high antimicrobial activity with very low MIC values (0.51 μg/ml for Candida albicans yeast and 0.26 μg/ml for Escherichia coli bacteria). The different ultrastructural effects of silver nanoparticles on yeast and bacterial cells were observed by TEM. Antibiofilm efficacy studies were also examined in two stages as prebiofilm and postbiofilm effect. In prebiofilm effect studies, AgNPs (0.51 μg/ ml) exhibited 81% reducing effect on biofilm formation. The highest reduction rate in postbiofilm studies was 73.5% and this was achieved with 2.04 μg/ml AgNPs. Our data support that the silver nanoparticles obtained by this environmentally friendly process have potential to be used for industrial and therapeutic purposes.     

Cytotoxic effect of Green synthesized silver nanoparticles using Melia azedarach against in vitro HeLa cell lines and lymphoma mice model

This communication explains the biosynthesis of stable silver nanoparticles (AgNPs) from Melia azedarach and its cytotoxicity against in vitro HeLa cells and in vivo Dalton's ascites lymphoma (DAL) mice model. The AgNPs synthesis was determined by UV–visible spectrum and it was further characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS) and X-ray diffraction (XRD) analysis. Zeta potential analysis revealed stable AgNPs at ?24.9 mV. UV visible spectrum indicated an absorption peak at 436 nm which reflects its specific Surface Plasmon Resonance (SPR). Biosynthesized AgNPs were predominantly cubical and spherical with an average particle size of 78 nm approximately as observed through SEM and DLS analysis, respectively. Cytotoxicity of biosynthesized AgNPs against in vitro Human epithelial carcinoma cell line (HeLa) showed a dose–response activity. Lethal dose (LD₅₀) value was found to be 300 μg/mL of AgNPs against HeLa cell line. Cytotoxicity against normal continuous cell line human breast lactating, donor 100 (HBL 100) was found only in increased concentration of both AgNPs and 5-FU. In addition, in vivo DAL mice model showed significant increase in life span, induction of apoptosis was evidenced by acridine orange and ethidium bromide (AO and EB) staining.