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.     

Green synthesis,characterization and biological activity of Solanum trilobatum-mediated silver nanoparticles

Biologically inspired synthesis of nanoparticles was found to be more attractive in metal nanoparticle synthesis. The present study reported an in-situ biogenic synthesis of silver nanoparticles (AgNPs) using Solanum trilobatum aqueous leaf extract. On this basis, the aqueous leaf extract of S. trilobatum acted as a reducing agent and stabilizing agent to synthesize highly stable AgNPs at ambient temperature. Eventually, the synthesized and stabilized AgNPs surface plasmon resonance was near 430 nm through a UV–visible (UV–vis) spectrophotometer. Here, the stability of the silver colloids monitored through zeta potential and mean particle size was evaluated through diffraction light scattering (DLF). Further, the average particle size was found to be 27.6 nm and spherical, confirmed with transmission electron microscopy (TEM). Also, colloidal AgNPs and aqueous extract are found to be rich sources of antioxidants and exhibit higher free radical scavenging ability. Thus, efficient inhibition with COX1 and COX2 enzymes and the protective effect with human red blood cell (HRBC) membrane stability showed significant results. These features are promising, suggesting the possibility of the AgNPs to be useful to disease-modifying for treating inflammatory disorders and associated complications.     

Phyconanotechnology: synthesis of silver nanoparticles using brown marine algae Cystophora moniliformis and their characterisation

Biosynthesis of metallic nanoparticles is a relatively new developing area of nanotechnology which has economic and environmentally friendly advantages over conventional chemical and physical methods of synthesis. In this paper, we report for the first time, on the synthesis of silver nanoparticles (AgNPs) using the Australasian brown marine algae Cystophora moniliformis. An extract of this alga was used as a reducing and stabilising agent. Temperature-dependent variation of the size of the AgNPs was observed. Agglomeration of the nanoparticles was observed at high temperatures. The average size of the AgNPs formed at temperatures?<?65°C was 75 nm, whereas they were >2 μm at higher temperatures. The X-ray diffraction (XRD) pattern revealed face-centered cubic structure of the formed Ag nanoparticles.     

Influence of Optical Properties of Ag NPs from Raphanus sativus Leaf Extract on Lanthanide Complexes

Plasmonics - Simple rapid green synthesis route using Raphanus sativus leaf extract as reducing and stabilizing agent produced silver nanoparticles (Ag NPs) at room temperature. The formation of Ag...     

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.     

Functionalization of cotton fabrics with titanium oxide doped silver nanoparticles: Antimicrobial and UV protection activities

The target of our current work was designed to prepare titanium oxide doped silver nanoparticles (Ag/TiO₂NPs) and their impact on the functionalization of cotton fabrics. Additionally, the effect of Ag/TiO₂NPs was compared with the individually prepared silver nanoparticles (AgNPs) and titanium oxide nanoparticles (TiO₂NPs). In this work, AgNPs were prepared in the solid state using arabic gum as efficient stabilizing and reducing agent. Then, two concentrations of the as-synthesized nanoparticles were used to functionalize the cotton fabrics by pad-dry-cure treatment in the presence of fixing agent to increase the durability of treated cotton fabrics against vigorous washing cycles. The findings implied that the as-prepared nanoparticles were successfully synthesized in nano-size with spherical shape and homogeneity. The efficacy of the functionalized cotton fabrics with those nanoparticles were evaluated in terms of multifunctional properties including antimicrobial and ultraviolet protection factor (UPF) and the mechanical features before and after many washing cycles; 10, 15 and 20 times. The resultant also proved that Ag/TiO₂NPs-treated cotton fabrics exhibited the greater values of both antimicrobial and UPF properties with enhancement in the tensile strength and elongation features. Thus, the combination between these two nanoparticles through doping reaction is suitable for imparting superior antimicrobial properties against the four tested microbial species (Staphylococcus aureus, Escherichia coli, Candida albicans, and Aspergillus niger) and good UPF properties. Depending on the promising obtained results of the multi-finishing fabrics, these nanoparticles of Ag/TiO₂NPs can be applied for the production of an efficient medical clothes for doctors, nurses and bed sheets for patients in order to kill and prevent the spread of bacteria and then, reduce the transmission of infection to others.     

Crystallization of silver through reduction process using Elaeis guineensis biosolid extract

This study presents a special, economically valuable, unprecedented eco-friendly green process for the synthesis of silver nanoparticles. The silver nanoparticles were obtained from a waste material with oil palm biosolid extract as the reducing agent. The use of the oil palm biosolid extract for the nanoparticle synthesis offers the benefit of amenability for large-scale production. An aqueous solution of silver (Ag(+) ) ions was treated with the oil palm biosolid extract for the formation of Ag nanoparticles. The nanometallic dispersion was characterized by surface plasmon absorbance measuring 428 nm. Transmission electron microscopy showed the formation of silver nanoparticles in the range of 5-50 nm. Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction analysis of the freeze-dried powder confirmed the formation of metallic silver nanoparticles. Moreover, Fourier Transform Infrared Spectroscopy provided evidence of phenolics or proteins as the biomolecules that were likely responsible for the reduction and capping agent, which helps to increase the stability of the synthesized silver nanoparticles. In addition, we have optimized the production with various parameters.     

Biogenic synthesis of silver nanoparticles: Antibacterial and cytotoxic potential

In green chemistry, the application of a biogenic material as a mediator in nanoparticles formation is an innovative nanotechnology. Our current investigation aimed at testing the cytotoxic potential and antimicrobial ability of silver nanoparticles (AgNPs) that were prepared using Calligonum comosum roots and Azadirachta indica leaf extracts as stabilizing and reducing agents. An agar well diffusion technique was employed to detect synthesized AgNPs antibacterial ability on Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus bacterial strains. Furthermore, their cytotoxic capability against LoVo, MDA-MB231 and HepG2 ca cells was investigated. For phyto-chemical detection in the biogenic AgNPs the Fourier-transform infrared spectroscopy (FT-IR) was considered. Zeta sizer, TEM (Transmission Electron Microscope) and FE-SEM (Field Emission Scanning Electron Microscope) were used to detect biogenic AgNPs’ size and morphology. The current results showed the capability of tested plant extract for conversion of Ag ions to AgNPs with a mean size ranging between 90.8 ± 0.8 and 183.2 ± 0.7 nm in diameter. Furthermore, prepared AgNPs exhibited apoptotic potential against HepG2, LoVo, and MDA-MB 231cell with IC₅₀ ranging between 10.9 and 21.4 μg/ml and antibacterial ability in the range of 16.0 ± 0.1 to 22.0 ± 1.8 mm diameter. Activation of caspases in AgNPs treated cells could be the main indicator for their positive effect causing apoptosis. The current investigation suggested that the green production of AgNPs could be a suitable substitute to large-scale production of AgNPs, since stable and active nanoparticles could be obtained.     

Exopolysaccharide-mediated silver nanoparticles produced by <Emphasis Type="Italic">Lactobacillus brevis</Emphasis> NM101-1 as antibiotic adjuvant

A green, simple and effective approach was performed to synthesize potent silver nanoparticles using bacterial exopolysaccharide as both a reducing and stabilizing agent. The formation of nanoparticles was first screened by measuring the surface plasmon resonance peak around 400 nm using UV-vis spectroscopy. The morphology of the synthesized AgNPs was determined using TEM, which indicated that the AgNPs were spherical in shape and with an average size of 11–25 nm. The presence of elemental silver of the AgNPs was confirmed by EDX analysis. The possible functional groups of EPS responsible for the reduction and stabilization of AgNPs were evaluated using FTIR. The EPS reduced AgNPs showed excellent antibacterial, and antibiofilm activities against various human pathogenic bacteria. In addition, the efficiency of AgNPs with various broad-spectrum antibiotics against the tested strains was evaluated. It is evident that, the antibacterial and antibiofilm activities of the selected antibiotics were increased in the presence of AgNPs. The increase in activity was more pronounced for gram-negative bacteria Pseudomonas aeruginosa and E. coli. Interestingly, the combination of antibiotics with AgNPs has significantly increased the membrane protein leakage and ROS generation than antibiotics or AgNPs alone. This work supports that AgNPs can be used to enhance the activity of existing antibiotics against gram-negative and gram-positive bacteria for the treatment of infectious diseases.     

Ultrasensitive and selective detection of copper (II) and mercury (II) ions by dye-coded silver nanoparticle-based SERS probes

A simple and distinctive method for the ultrasensitive detection of Cu(2+) and Hg(2+) based on surface-enhanced Raman scattering (SERS) using cysteine-functionalized silver nanoparticles (AgNPs) attached with Raman-labeling molecules was developed. The glycine residue in a silver nanoparticle-bound cysteine can selectively bind with Cu(2+) and Hg(2+) and form a stable inner complex. Silver nanoparticles co-functionalized with cysteine and 3,5-Dimethoxy-4-(6'-azobenzotriazolyl)phenol (AgNP conjugates) can be used to detect Cu(2+) and Hg(2+) based on aggregation-induced SERS of the Raman tags. The addition of SCN(-) to the analyte can successfully mask Hg(2+) and allow for the selective detection of Cu(2+). This SERS-based assay showed an unprecedented limit of detection (LOD) of 10pM for Cu(2+) and 1pM for Hg(2+); these LODs are a few orders of magnitude more sensitive than the typical colorimetric approach based on the aggregation of noble nanoparticles. The analysis of real water samples diluted with pure water was performed and verified this conclusion. We envisage that this SERS-based assay may provide a general and simple approach for the detection of other metal ions of interest, which can be adopted from their corresponding colorimetric assays that have already been developed with significantly improved sensitivity and thus have wide-range applications in many areas.     

Quasi‐spherical silver nanoparticles with high dispersity and uniform sizes: preparation,characterization and bioactivity in their interaction with bovine serum albumin

A stepwise seeded growth route for the preparation of silver nanoparticles (AgNPs) is reported. In the process, silver nitrate was used as a precursor, with sodium borohydride as a reducing agent and trisodium citrate as both a reductant and stabilizer. The AgNPs were characterized using several methods, including UV–vis spectroscopy, X‐ray diffraction and transmission electron microscopy. The prepared AgNPs were quasi‐spherical and crystalline, with an average diameter of 21 nm. Interactions between the AgNPs and bovine serum albumin (BSA) were investigated using UV–vis, fluorescence spectroscopy and synchronous fluorescence spectroscopy (SFS). It was proved that the quenching mechanism is a static process. The binding constants and number of binding sites were calculated. The thermodynamic parameters implied that the binding process was spontaneous and the main driving force of the interaction was electrostatic. The results of the SFS indicated that the conformational change of BSA was induced by AgNPs. Copyright © 2016 John Wiley & Sons, Ltd.     

Genus-wide physicochemical evidence of extracellular crystalline silver nanoparticles biosynthesis by Morganella spp

This study was performed to determine whether extracellular silver nanoparticles (AgNPs) production is a genus-wide phenotype associated with all the members of genus Morganella, or only Morganella morganii RP-42 isolate is able to synthesize extracellular Ag nanoparticles. To undertake this study, all the available Morganella isolates were exposed to Ag+ ions, and the obtained nanoproducts were thoroughly analyzed using physico-chemical characterization tools such as transmission electron microscopy (TEM), UV-visible spectrophotometry (UV-vis), and X-ray diffraction (XRD) analysis. It was identified that extracellular biosynthesis of crystalline silver nanoparticles is a unique biochemical character of all the members of genus Morganella, which was found independent of environmental changes. Significantly, the inability of other closely related members of the family Enterobacteriaceae towards AgNPs synthesis strongly suggests that AgNPs synthesis in the presence of Ag+ ions is a phenotypic character that is uniquely associated with genus Morganella.     

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.     

Valorization of mutant Bacillus licheniformis M09 supernatant for green synthesis of silver nanoparticles: photocatalytic dye degradation,antibacterial activity,and cytotoxicity

Bioprocess and Biosystems Engineering - The present study reports the optimization of a green method for the synthesis of&nbsp;silver nanoparticles (AgNPs) via reduction of Ag+ ions using...     

Phytosynthesis of silver nanoparticles using Mangifera indica flower extract as bioreductant and their broad-spectrum antibacterial activity

The present study focused on the evaluation of antibacterial property of silver nanoparticles (AgNPs) synthesized using mango flower extract. The morphology of the synthesized AgNPs was observed under transmission electron microscopy and the particles have shown spherical shape in the range of 10–20 nm. X-ray powder diffraction analysis confirmed the crystalline nature of the AgNPs. The atomic percentage of the Ag element in the nanoparticles was about 7.58% which is greater than the other elements present in the sample. The AgNPs showed extensive lethal effect on both Gram-positive (Staphylococcus sp.) and Gram-negative (Klebsiella sp., Pantoea agglomerans, and Rahnella sp.) bacteria. The extensive lethal effect of AgNPs against clinically important pathogens demonstrated that the mango flower mediated AgNPs could be applied as potential antibacterial agent to control the bacterial population in the respective industries.     

Green synthesis of silver nanoparticles using Andean blackberry fruit extract

Green synthesis of nanoparticles using various plant materials opens a new scope for the phytochemist and discourages the use of toxic chemicals. In this article, we report an eco-friendly and low-cost method for the synthesis of silver nanoparticles (AgNPs) using Andean blackberry fruit extracts as both a reducing and capping agent. The green synthesized AgNPs were characterized by various analytical instruments like UV–visible, transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The formation of AgNPs was analyzed by UV–vis spectroscopy at λ_max = 435 nm. TEM analysis of AgNPs showed the formation of a crystalline, spherical shape and 12–50 nm size, whereas XRD peaks at 38.04°, 44.06°, 64.34° and 77.17° confirmed the crystalline nature of AgNPs. FTIR analysis was done to identify the functional groups responsible for the synthesis of the AgNPs. Furthermore, it was found that the AgNPs showed good antioxidant efficacy (>78%, 0.1 mM) against 1,1-diphenyl-2-picrylhydrazyl. The process of synthesis is environmentally compatible and the synthesized AgNPs could be a promising candidate for many biomedical applications.     

Synthesis and Characterization of Eugenia uniflora L. Silver Nanoparticles and L-Cysteine Sensor Application

L-Cysteine (Cys) is a non-essential sulfur-containing amino acid, crucial for protein synthesis, detoxification, and several metabolic functions. Cys is widely used in the agricultural, food, cosmetic, and pharmaceutical industries. So, a suitable sensitive and selective sensing approach is of great interest, and a low-cost sensor would be necessary. This article presents silver nanoparticles (EuAgNPs) synthesized by a green synthesis method using Eugenia uniflora L. extracts and photoreduction. The nanoparticles were characterized by UV/VIS, transmission electron microscopy, high-performance liquid chromatography (HPLC), FTIR, and Zeta potential. With the addition of Cys in the EuAgNPs solution, the terminal thiol part of L-cysteine binds on the surface of nanoparticles through Ag−S bond. The EuAgNPs and CysAgNPs coexist until flavonoids bound the amino group of Cys, enhancing the red color of solutions. The EuAgNPs provided selectivity to detect Cys among other amino acids, and its detection limit was found to be 3.8 nM. The sensor has the advantages of low-cost synthesis, fast response, high selectivity, and sensitivity.     

Influence of strong bases on the synthesis of silver nanoparticles (AgNPs) using the ligninolytic fungi Trametes trogii

Silver nanoparticles (AgNPs) were biosynthesized using fungal extract of Trametes trogii, a white rot basidiomycete involved in wood decay worldwide, which produces several ligninolytic enzymes. According to previous studies using fungi, enzymes are involved in nanoparticles synthesis, through the so-called green synthesis process, acting as reducing and capping agents. Understanding which factors could modify nanoparticles’ shape, size and production efficiency is relevant. The results showed that under the protocol used in this work, this strain of Trametes trogii is able to synthesize silver nanoparticles with the addition of silver nitrate (AgNO₃) to the fungal extract obtained with an optimal incubation time of 72 h and pH 13, using NaOH to adjust pH. The progress of the reaction was monitored using UV–visible spectroscopy and synthesized AgNPs was characterized by scanning electron microscope (SEM), through in-lens and QBDS detectors, and energy-dispersive X-ray spectroscopy (EDX). Additionally, SPR absorption was modeled using Mie theory and simple nanoparticles and core-shell configurations were studied, to understand the morphology and environment of the nanoparticles. This protocol represents a simple and cheap synthesis in the absence of toxic reagents and under an environmentally friendly condition.     

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.     

Pomegranate peel induced biogenic synthesis of silver nanoparticles and their multifaceted potential against intracellular pathogen and cancer

In the field of nano-biotechnology, silver nanoparticles (AgNPs) share a status of high repute owing to their remarkable medicinal values. Biological synthesis of environment-friendly AgNPs using plant extracts has emerged as the beneficial alternative approach to chemical synthesis. In the current study, we have synthesized biogenic silver nanoparticles (PG-AgNPs) using the peel extract of Punica granatum as a reducing and stabilizing agent. The as-synthesized PG-AgNPs were characterized and evaluated for their antibacterial and anticancer potential. UV–Visible spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS) confirmed the formation of biogenic PG-AgNPs. The antibacterial potential was assessed against the biofilm of Listeria monocytogenes. The PG-AgNPs were efficacious against sessile bacteria and their biofilm as well. The as-synthesized nanoparticles at sub-MIC values showed dose-dependent inhibition of biofilm formation. Corroborating results were observed under crystal violet assay, Congo red staining, Confocal microscopy and SEM analysis. The anticancer ability of the nanoparticles was evaluated against MDA-MB-231 metastatic breast cancer cells. As evident from the MTT results, PG-AgNPs significantly reduced the cell viability in a dose-dependent manner. Exposure of MDA-MB-231 cells led to the accumulation of reactive oxygen species (ROS). Morphological changes and DNA fragmentation showed the strong positive effect of PG-AgNPs on the induction of apoptosis. Collectively, the as-synthesized PG-AgNPs evolved with synergistically emerged attributes that were effective against L. monocytogenes and also inhibited its biofilm formation; moreover, the system displayed lower cytotoxic manifestation towards mammalian cells. In addition, the PG-AgNPs embodies intriguing anticancer potential against metastatic breast cancer cells.