Controlled biosynthesis of AgCl nanoparticles by a thermotolerant <Emphasis Type="Italic">Aspergillus terreus</Emphasis> in the L-Tryptophan supplemented media: Characterization and antimicrobial activity

A simple and green method was developed for the extracellular biosynthesis of silver chloride nanoparticles, free from silver nanoparticles, using cell-free filtrate of a thermotolerant fungal strain Aspergillus terreus 8. The synthesized silver chloride nanoparticles exhibited characteristic absorption maximum at 275 nm. As-fabricated AgCl-NPs were characterized by UV-vis spectroscopy, XRD, SEM-EDX, and FT-IR. The biosynthesized silver chloride nanoparticles exhibited strong antimicrobial activity towards pathogenic microorganisms such as Fusarium oxysporum f. sp. vasinfectum and Verticillium dahliae. The synthesized silver chloride nanoparticles can be exploited as a promising new biocide bionanocomposite against pathogenic microorganisms.     

Novel microbial route to synthesize silver nanoparticles using spore crystal mixture of Bacillus thuringiensis

Metallic nanoparticles are traditionally synthesized by wet chemical techniques, where the chemicals used are often toxic and flammable. In the present study, the spore crystal mixture of Bacillus thuringiensis was used for the synthesis of silver nanoparticles. Nanoparticles were characterized using UV-Vis absorption spectroscopy, XRD and TEM. X-ray diffraction and TEM analysis showed the average particle size of 15 nm and mixed (cubic and hexagonal) structure. This is for the first time that any bacterial spore crystal mixture was used for the synthesis of nanoparticles. Further, these biologically synthesized nanoparticles were found to be highly toxic against different multi drug resistant human pathogenic bacteria.     

Silver glyconanoparticles functionalized with sugars of sweet sorghum syrup as an antimicrobial agent

Bio-directed synthesis of metal nanoparticles is gaining importance due to their biocompatibility, low toxicity and eco-friendly nature. We used sweet sorghum syrup for a facile and cost-effective green synthesis of silver glyconanoparticles. Silver nanoparticles were formed due to reduction of silver ions when silver nitrate solution was treated with sorghum syrup solutions of different pH values. The nanoparticles were characterized by UV–vis, TEM (transmission electron microscopy), DLS (dynamic light scattering), EDAX (energy dispersive X-ray spectroscopy), FT-IR (fourier transform infrared spectroscopy) and XRD (X-ray diffraction spectroscopy). The silver glyconanoparticles exhibited a characteristic surface plasmon resonance around 385 nm. At pH 8.5, the nanoparticles were mono-dispersed and spherical in shape with average particle size of 11.2 nm. The XRD and SAED studies suggested that the nanoparticles were crystalline in nature. EDAX analysis showed the presence of elemental silver signal in the synthesized glyconanoparticles. FT-IR analysis revealed that glucose, fructose and sucrose present in sorghum syrup acted as capping ligands. Silver glyconanoparticles prepared at pH 8.5 had a zeta potential of ?28.9 mV and were anionic charged. They exhibited strong antimicrobial activity against Gram-positive, Gram-negative and different Candida species at MIC values ranging between 2 and 32 μg ml^?1. This is first report on sweet sorghum syrup sugars-derived silver glyconanoparticles with antimicrobial property.     

Antimicrobial Activities of Silver Nanoparticles Synthesized by Using Water Extract of Arnicae anthodium

Green synthesis of nanoparticles has gained significant importance in recent years and has become the one of the most preferred methods. Also, green synthesis of nanoparticles is valuable branch of nanotechnology. Plant extracts are eco-friendly and can be an economic option for synthesis of nanoparticles. This study presents method the synthesis of silver nanoparticles using water extract of Arnicae anthodium. Formation of silver nanoparticles was confirmed by UV–visble spectroscopy, Fourier transform infrared spectroscopy and total reflection X-ray fluorescence analysis. The morphology of the synthesized silver nanoparticles was verified by SEM–EDS. The obtained silver nanoparticles were used to study their antimicrobial activity.     

Synthesis of silver nanoparticles by endosymbiont Pseudomonas fluorescens CA 417 and their bactericidal activity

The present study emphasizes on biogenic synthesis of silver nanoparticles and their bactericidal activity against human and phytopathogens. Nanoparticle synthesis was performed using endosymbiont Pseudomonas fluorescens CA 417 inhabiting Coffea arabica L. Synthesized nanoparticles were characterized using hyphenated spectroscopic techniques such as UV–vis spectroscopy which revealed maximum absorption 425 nm. Fourier transform infrared spectroscopy (FTIR) analysis revealed the possible functional groups mediating and stabilizing silver nanoparticles with predominant peaks occurring at 3346 corresponding to hydroxyl group, 1635 corresponding carbonyl group and 680 to aromatic group. X-ray diffraction (XRD) analysis revealed the Bragg’s diffraction pattern with distinct peaks at 38° 44°, 64° and 78° revealing the face-centered cubic (fcc) metallic crystal corresponding to the (111), (200), (220) and (311) facets of the crystal planes at 2θ angle. The energy dispersive X-ray spectroscopy (EDS) analysis revealed presence of high intense absorption peak at 3 keV is a typical characteristic of nano-crystalline silver which confirmed the presence of elemental silver. TEM analysis revealed the size of the nanoparticles to be in the range 5–50 nm with polydisperse nature of synthesized nanoparticles bearing myriad shapes. The particle size determined by Dynamic light scattering (DLS) method revealed average size to be 20.66 nm. The synthesized silver nanoparticles exhibited significant antibacterial activity against panel of test pathogens. The results showed Klebsiella pneumoniae (MTCC 7407) and Xanthomonas campestris to be more sensitive among the test human pathogen and phyto-pathogen respectively. The study also reports synergistic effect of silver nanoparticles in combination with kanamycin which displayed increased fold activity up to 58.3% against Klebsiella pneumoniae (MTCC 7407). The results of the present investigation are promising enough and attribute towards growing scientific knowledge on development of new antimicrobial agents to combat drug resistant microorganisms. The study provides insight on emerging role of endophytes towards reduction of metal salts to synthesize nanoparticles.     

Extracellular synthesis of gold bionanoparticles by <Emphasis Type="Italic">Nocardiopsis</Emphasis> sp. and evaluation of its antimicrobial,antioxidant and cytotoxic activities

Advancement of biological process for the synthesis of bionanoparticles is evolving into a key area of research in nanotechnology. The present study deals with the biosynthesis, characterization of gold bionanoparticles by Nocardiopsis sp. MBRC-48 and evaluation of their antimicrobial, antioxidant and cytotoxic activities. The gold bionanoparticles obtained were characterized by UV–visible spectroscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray analysis and transmission electron microscopy (TEM). The synthesized gold bionanoparticles were spherical in shape with an average of 11.57 ± 1.24 nm as determined by TEM and dynamic light scattering (DLS) particle size analyzer, respectively. The biosynthesized gold nanoparticles exhibited good antimicrobial activity against pathogenic microorganisms. It showed strong antioxidant activity as well as cytotoxicity against HeLa cervical cancer cell line. The present study demonstrated the potential use of the marine actinobacterial strain of Nocardiopsis sp. MBRC-48 as an important source for gold nanoparticles with improved biomedical applications including antimicrobial, antioxidant as well as cytotoxic agent.     

Cytotoxicity and anti-microbial analysis of silver and graphene oxide bio nanoparticles

It is of interest to document the cytotoxicity and anti microbial analysis of silver and graphene oxide nanoparticles. The plant extracts from Andrographis paniculata and Ocimum sanctum Linn were used as reducing agent. The nanoparticles were characterized using UV-visible spectroscopy, FT-IR, XRD and TEM. The antimicrobial activity was completed for oral pathogens. Brine Shrimp Lethality assay was conducted for cytotoxicity. Thus, we show that silver and graphene oxide bio based nanoparticles have antimicrobial activity with minimum cytotoxic effects.     

Green synthesis of silver nanoparticles from aqueous extract of Scutellaria barbata and coating on the cotton fabric for antimicrobial applications and wound healing activity in fibroblast cells (L929)

Scutellaria barbata is a perennial herb which was vastly prescribed in Chinese medicine to treat inflammations, infections and it is also used a detoxifying agent. We synthesized silver nanoparticles with Scutellaria barbata extract and characterized the nanoparticles with UV–Vis spectroscopic analysis, TEM, AFM, FTIR and XRD. The biofilm inhibiting property of synthesized silver nanoparticles were examined with XTT reduction assay and the antimicrobial property was examined with well diffusion method. The silver nanoparticles were also coated with cotton fabrics and their efficacy against antimicrobials was analyzed to prove its application. The cytotoxic property of synthesized silver nanoparticles was examined with L929 fibroblast cells using MTT assay. Finally we analyzed the wound healing property of synthesized silver nanoparticles with wound scratch assay. The result of our UV–Vis spectroscopic analysis confirms Scutellaria barbata aqueous extract reduced silver ions and synthesized silver nanoparticles. The characterization studies TEM, AFM, FTIR and XRD confirms the synthesized silver nanoparticles are in ideal shape and size to be utilized as a drug. The XTT reduction assay proves silver nanoparticles effectively inhibits the biofilm formation in both resistant and sensitive strains. Antimicrobial sensitivity tests confirms synthesized silver nanoparticles and cotton coated synthesized silver nanoparticles both are effective against gram positive, gram negative and fungal species. Further the results of MTT assay confirms the synthesized silver nanoparticles are non toxic and finally the wound healing potency of the nanoparticles was confirmed with wound scratch assay. Over all our results authentically confirms the silver nanoparticles synthesized with Scutellaria barbata aqueous extract is potent wound healing drug.     

Green synthesis of silver nanoparticles by Rivina humilis leaf extract to tackle growth of Brucella species and other perilous pathogens

Novel approaches are obligatory to treat chronic intracellular bacterial infectious diseases like Brucellosis specifically, are very complicated to deal with. The aim of the study to take upon nanotechnology approach to exploit the efficacy of the synthesized nanoparticles, to overcome barriers for treatment of Brucella species and other pathogens. Present study used Rivina humilis extract as reductant of silver ions for synthesis of silver nanoparticles for the first time. Rh-AgNP’s was characterized by UV–visible spectroscopy, DLS, FT-IR, SEM, EDS, TEM and XRD. Radical scavenging, antibrucellosis, bactericidal activity was evaluated. Clinical application was assessed by Rate of haemolysis, fibrinolytic and Hemagglutination activity. UV–visible spectrum of synthesized Rh-AgNP’s showed maximum peak at 440 nm indicating the formation of nanoparticles. TEM showed that the average particle size of nanoparticles 51 nm with spherical shape, DLS depicted monodisperse state in water; EDS confirmed the presence of silver metal. Rh-AgNP’s exhibited potential antibrucellosis activity against B. abortus, B. melitensis and B. suis effective inhibition at 800 μg/mL. The bio-compatibility of Rh-AgNP’s was established by rate of haemolysis, hemagglutination and fibrinolytic activity. For the first time it has been proved that Rh-AgNP’s have efficacy as antimicrobial agent with potential application in the biological domain.     

Antibacterial and antibiofilm effects of silver nanoparticles against the uropathogen Escherichia coli U12

The drug-resistant bacterial strains' emergence increases day by day. This may be a result of biofilm presence, which protects bacteria from antimicrobial agents. Thus, new approaches must be used to control biofilm-related infections in healthcare settings. In such a study, biological silver nanoparticles were introduced in such a study as an anti-biofilm agent against multidrug-resistant E. coli U12 on urinary catheters. Seven different silver nanoparticles concentrations were tested for their antimicrobial activities. Also, anti-biofilm activities against E. coli U12 were tested. Using the dilution method, the silver nanoparticles concentration of 85 μg/ml was the MIC (Minimum Inhibitory Concentration) that had excellent biocompatibility and showed significant antibacterial activity against E. coli U12. Scanning electron microscopy (SEM) confirmed that the highest efficient dose of silver nanoparticles was 340 μg/ml at 144 h that reduced adhesion of E. coli U12 to the urinary catheter. E. coli U12 cells ruptured cell walls and cell membranes after being examined using transmission electron microscopy (TEM). Thus, biologically prepared silver nanoparticles could be used to coat medical devices since it is effective and promising to inhibit biofilm formation by impregnating urinary catheters with silver nanoparticles.     

Development of an eco-friendly approach for biogenesis of silver nanoparticles using spores of Bacillus athrophaeus

The biological synthesis methods have been emerging as a promising new approach for production of nanoparticles due to their simplicity and non-toxicity. In the present study, spores of Bacillus athrophaeus were used to achieve the objective of developing a green synthesis method of silver nanoparticles. Enzyme assay revealed that the spores and their heat inactivated forms (microcapsules) were highly active and their enzymatic contents differed from the vegetative cells. Laccase, glucose oxidase, and alkaline phosphatase activities were detected in the dormant forms, but not in the vegetative cells. Although no nanoparticle was produced by active cells of B. athrophaeus, both spores and microcapsules were efficiently capable of reducing the silver ions (Ag⁺) to elemental silver (Ag⁰) leading to the formation of nanoparticles from silver nitrate (AgNO₃). The presence of biologically synthesized silver nanoparticles was determined by obtaining broad spectra with maximum absorbance at 400 nm in UV–visible spectroscopy. The X-ray diffraction analysis pattern revealed that the nanoscale particles have crystalline nature with various topologies, as confirmed by transmission electron microscopy (TEM). The TEM micrograph showed the nanocrystal structures with dimensions ranging from 5 to 30 nm. Accordingly, the spore mixture could be employed as a factory for detoxification of heavy metals and subsequent production of nanoparticles. This research introduces an environmental friendly and cost effective biotechnological process for the extracellular synthesis of silver nanoparticles using the bacterial spores.     

The effect of temperature on antibacterial activity of biosynthesized silver nanoparticles

The purpose of this study was the evaluation of two different temperatures on antibacterial activity of the biosynthesized silver nanoparticles. 38 silver nanoparticles-producing bacteria were isolated from soil and identified. Biosynthesis of silver nanoparticles by these bacteria was verified through visible light spectrophotometry. Two strains were relatively active for production of silver nanoparticles. These strains were subjected for molecular identification and recognized as Bacillus sp. and Acinetobacter schindleri. In the present study, the effect of temperatures was evaluated on structure and antimicrobial properties of the silver nanoparrticles by transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis and antimicrobial Agar well diffusion methods. The silver nanoparticles showed antibacterial activity against all the pathogenic bacteria; however, this property was lost after treatment of the silver nanoparticles by high temperatures (100 and 300 °C). TEM images showed that the average sizes of heated silver nanoparticles were >100 nm. However, these were <100 nm for non-heated silver nanoparticles. Although, XRD patterns showed the crystalline structure of heated silver nanoparticles, their antibacterial activities were less. This was possible because of the sizes and accordingly less penetration of the particles into the bacterial cells. In addition, elimination of the capping agents by heat might be considered another reason.     

Analysis of antimicrobial silver nanoparticles synthesized by coastal strains of Escherichia coli and Aspergillus niger

The present study investigated the extracellular biosynthesis of antimicrobial silver nanoparticles by Escherichia coli AUCAS 112 and Aspergillus niger AUCAS 237 derived from coastal mangrove sediment of southeast India. Both microbial species were able to produce silver nanoparticles, as confirmed by X-ray diffraction spectrum. The nanoparticles synthesized were mostly spherical, ranging in size from 5 to 20 nm for E. coli and from 5 to 35 nm for A. niger, as evident by transmission electron microscopy. Fourier transform spectroscopy revealed prominent peaks corresponding to amides I and II, indicating the presence of a protein for stabilizing the nanoparticles. Electrophoretic analysis revealed the presence of a prominent protein band with a molecular mass of 45 kDa for E. coli and 70 kDa for A. niger. The silver nanoparticles inhibited certain clinical pathogens, with antibacterial activity being more distinct than antifungal activity. The antimicrobial activity of E. coli was more pronounced than that of A. niger and was enhanced with the addition of polyvinyl alcohol as a stabilizing agent. This work highlighted the possibility of using microbes of coastal origin for synthesis of antimicrobial silver nanoparticles.     

Synthesis and comparative study on the antimicrobial activity of hybrid materials based on silver nanoparticles (AgNps) stabilized by polyvinylpyrrolidone (PVP)

Hybrid materials based on polyvinylpyrrolidone (PVP) with silver nanoparticles (AgNps) were synthesized applying two different strategies based on thermal or chemical reduction of silver ions to silver nanoparticles using PVP as a stabilizer. The formation of spherical silver nanoparticles with diameter ranging from 9 to 16 nm was confirmed by TEM analysis. UV-vis and FTIR spectroscopy were also applied to confirm the successful formation of AgNps. The antibacterial activity of the synthesized AgNPs/PVP against etalon strains of three different groups of bacteria—Staphylococcus aureus (S. aureus; gram-positive bacteria), Escherichia coli (E. coli; gram-negative bacteria), Pseudomonas aeruginosa (P. aeruginosa; non-ferment gram-negative bacteria), as well as against spores of Bacillus subtilis (B. subtilis) was studied. AgNps/PVP were tested for the presence of fungicidal activity against different yeasts and mold such as Candida albicans, Candida krusei, Candida tropicalis, Candida glabrata, and Aspergillus brasiliensis. The hybrid materials showed a strong antimicrobial effect against the tested bacterial and fungal strains and therefore have potential applications in biotechnology and biomedical science.     

Green synthesis,characterization, enhanced functionality and biological evaluation of silver nanoparticles based on Coriander sativum

The present study focused on the green synthesis of silver nanoparticles from Coriander sativum (CS) containing structural polymers, phenolic compounds and glycosidic bioactive macromolecules. Plant phenolic compounds can act as antioxidants, lignin, and attractants like flavonoids and carotenoids. Henceforth, silver nanoparticles (AgNPs) were prepared extracellularly by the combinatorial action of stabilizing and reduction of the CS leaf extract. The biologically synthesized CS-AgNPs were studied by UV-spectroscopy, zeta potential determination, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis to characterize and confirm the formation of crystalline nanoparticles. The synthesized nanoparticles demonstrated strong antimicrobial activity against all microbial strains examined with varying degrees. The scavenging action on free radicals by CS-AgNPs showed strong antioxidant efficiency with superoxide and hydroxyl radicals at different concentrations as compared with standard ascorbic acid. The presence of in vitro anticancer effect was confirmed at different concentrations on the MCF-7 cell line as revealed with decrease in cell viability which was proportionately related to the concentration of CS-AgNPs illustrating the toxigenic nature of synthesized nanoparticles on cancerous cells.     

Green synthesis of silver nanoparticles using Rhodobacter Sphaeroides

The use of microorganisms in the synthesis of nanoparticles emerges as an eco-friendly and exciting approach. In this study, silver nanoparticles were successfully synthesized from AgNO₃ by reduction of aqueous Ag⁺ ions with the cell filtrate of Rhodobacter sphaeroides. Nanoparticles were characterized by means of UV–vis absorption spectroscopy, X-Ray Diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Crystalline nature of the nanoparticles in the fcc structure are confirmed by the peaks in the XRD pattern corresponding to (111), (200), (220) and (311) planes, bright circular spots in the selected are a electron diffraction (SAED) and clear lattice fringes in the high-resolution TEM image. Also, the size of silver nanoparticles was controlled by the specific activity of nitrate reductase in the cell filtrate.     

Synthesis of silver nanoparticles using haloarchaeal isolate Halococcus salifodinae BK3

Numerous bacteria, fungi, yeasts and viruses have been exploited for biosynthesis of highly structured metal sulfide and metallic nanoparticles. Haloarchaea (salt-loving archaea) of the third domain of life Archaea, on the other hand have not yet been explored for nanoparticle synthesis. In this study, we report the intracellular synthesis of stable, mostly spherical silver nanoparticles (AgNPs) by the haloarchaeal isolate Halococcus salifodinae BK₃. The culture on adaptation to silver nitrate exhibited growth kinetics similar to that of the control. NADH-dependent nitrate reductase was involved in silver tolerance, reduction, synthesis of AgNPs, and exhibited metal-dependent increase in enzyme activity. The AgNPs preparation was characterized using UV–visible spectroscopy, XRD, TEM and EDAX. The XRD analysis of the nanoparticles showed the characteristic Bragg peaks of face-centered cubic silver with crystallite domain size of 22 and 12 nm for AgNPs synthesized in NTYE and halophilic nitrate broth (HNB), respectively. The average particle size obtained from TEM analysis was 50.3 and 12 nm for AgNPs synthesized in NTYE and HNB, respectively. This is the first report on the synthesis of silver nanoparticles by haloarchaea.     

Elucidating the chemical and biochemical applications of Citrus sinensis-mediated silver nanocrystal

Abstract

Synthesis of nanoparticles using biodegradable source is safer and echo-friendly. Here, we describe the synthesis of polycrystalline silver nanocrystals using Citrus sinensis acting as both reducing and capping agents. After exposing the silver ions to orange extract, rapid reduction of silver ions led to the formation of stable silver nanocrystals due to the reducing and stabilizing properties of orange fruit juice. The synthesized silver nanocrystals were characterized using various analytical techniques like UV–vis spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The biochemical activity of the synthesized nanocrystals was studied in the light of affinity to bovine serum albumin using several biophysical methods like absorbance, fluorescence and circular dichroism spectroscopy. Cytotoxic activity of these nanocrystals was also studied against Hep-2 cell line using fluorescence microscopy. It was also found that the synthesized nanocrystals can sense mercuric ion down to 50?µM in the presence of a number of cations. Furthermore, we established that the silver nanoparticles can effectively catalyse the reduction of methylene blue by ascorbic acid. The present study will enrich our knowledge on the chemical and biochemical activities of green-synthesized silver nanocrystals.     

Antibacterial Activity of Green Synthesized Silver Nanoparticles Using Vasaka (Justicia adhatoda L.) Leaf Extract

There is an increasing demand for silver nanoparticles due to its wide applicability in various area of biological science such as in field of antimicrobial and therapeutics, biosensing, drug delivery etc. To use in bioprocess the silver nanoparticles should be biocompatible and free from toxic chemicals. In the present study we report a cost effective and environment friendly route for green synthesis of silver nanoparticles using Vasaka (Justicia adhatoda L.) leaf extract as reducing as well as capping agent. This plant has been opted for the present study for its known medicinal properties and it is easily available. The biosynthesized silver nanoparticles are characterized by UV–Vis spectroscopy and TEM analysis. It is observed the nanoparticles are well shaped and the average particle size is 20 nm in the range of 5–50 nm. The antibacterial activity of these nanoparticles against Pseudomonas aeruginosa MTCC 741 has been measured by disc diffusion method, agar cup assay and serial dilution turbidity measurement assay. The results show green synthesized silver nanoparticles, using Vasaka leaf extract, have a potential to inhibit the growth of bacteria.

Electronic supplementary material

The online version of this article (doi:10.1007/s12088-015-0512-1) contains supplementary material, which is available to authorized users.     

Synthesis of methylcellulose-silver nanocomposite and investigation of mechanical and antimicrobial properties

In this paper we reported preparation of methylcellulose-silver nanocomposite films by mixing of aqueous solution of methylcellulose with silver nitrate followed by casting. The silver nanoparticles were generated in methylcellulose matrix through reduction and stabilization by methylcellulose. The surface plasmon band at 412nm indicated the formation of Ag nanoparticles. The MC-Ag nanocomposite films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR). The X-ray diffraction analysis of synthesized MC-Ag nanocomposite films revealed that metallic silver was present in face centered cubic crystal structure. Average crystallite size of silver nanocrystal was 22.7nm. The FTIR peaks of as-synthesized MC-Ag nanocomposite fully designated the strong interaction between Ag nanoparticles and MC matrix. Nano-sized silver modified methylcellulose showed enhanced mechanical properties i.e. the introduction of Ag leading to both strengthening and toughening of MC matrix. The methylcellulose-silver nanocomposite films offered excellent antimicrobial activity against various microorganisms.