Synthesis of Rumex hastatus-based silver nanoparticles induced the inhibition of human pathogenic bacterial strains

The development of antibiotic resistance in pathogenic bacterial strains has drawn attention to the quest for new natural antibacterial drugs. Therefore, in the present study, extracts of Rumex hastatus leaves were obtained in methanol and water, and R. hastatus-based silver nanoparticles (AgNPs) were synthesized. Structural and functional properties of synthesized silver nanoparticles were determined by UV–vis spectroscopy, XRD, FTIR and SEM. The synthesized AgNPs and crude extracts were tested to check their antibacterial potential against human pathogenic bacterial strains of Staphylococcus aureus, Staphylococcus haemoliticus, Bacillus cereus, Escherichia coli, Salmonella typhi and Pseudomonas aeruginosa in well diffusion and broth dilution methods. The present investigation has revealed for the first time that the broth dilution method was found more reproducible than that of the well diffusion method even at lower concentrations of AgNPs and crude extracts. UV– Vis spectroscopic analysis of AgNPs revealed a peak at 367 nm_. XRD pattern showed a face-centered cubical to the spherical structure of AgNP crystals. FTIR analysis revealed that flavonoids and terpenoids are responsible for the reduction of AgNO₃ to Ag⁺. SEM analysis determined the spherical structure and 51 nm average diameter of nanoparticles. The antibacterial activity of R. hastatus-based (AgNPs) was found to be significantly higher than aqueous plant extract and silver nitrate alone. Bacterial growth was inhibited by R. hastatus-based AgNPs in a dose-dependent manner. To our knowledge, silver nanoparticles (AgNPs) of R. hastatus were synthesized and characterized for the first time in this study and, based on the findings of current research work R. hastatus extract-based silver nanoparticles are suggested to be used as an antibacterial drug instead of synthetic drugs for the treatment of various human diseases/infections caused by the tested bacterial strains.     

Biosynthesis of silver nanoparticles using Onosma sericeum Willd. and evaluation of their catalytic properties and antibacterial and cytotoxic activity

In this study, silver nanoparticle (AgNP) synthesis was carried out using Onosma sericeum Willd. aqueous extract for the first time, with a simple, economical, and green method without the need for any other organic solvent or external reducing or stabilizing agent. A variety of AgNPs, all of different particle sizes, were synthesized by controlling the silver ion concentration, extract volume, temperature, and pH. It was determined that the optimum conditions for AgNP synthesis were 1 mM AgNO3, pH 8, 25 °C, 20 g/200 mL extract, silver nitrate, and extract ratio 5:1 (v/v). The AgNPs were defined using UV-Vis spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The particle size distribution and zeta potential measurements of the AgNPs were measured using the dynamic light scattering (DLS) technique. It was determined that the AgNPs with a particle size of less than 10 nm showed a higher catalytic effect in the reduction of 2-nitrobenzenamine. It was also found that these nanoparticles had a cytotoxic effect on the MCF-7 breast cancer cell line depending on dosage and time. The resulting IC50 values were between 76.63 µg/mL and 169.77 µg/mL. Furthermore, the biosynthesized AgNPs showed effective antibacterial activity against the Acinetobacter baumannii bacteria. The results of the study showed that synthesized AgNPs can have a promising role in biomedical and nanobiotechnology applications.     

Antibacterial effect of silver nanoparticles prepared in bipolymers at moderate temperature

The purpose of this study was to investigate the antibacterial effect of silver nanoparticles in chitosan–poly(ethylene glycol) suspension. The silver nanoparticles (AgNPs) were prepared by use of an environmentally benign method from chitosan (Cts) and poly(ethylene glycol) (PEG) at moderate temperature and with stirring for different times. Silver nitrate (AgNO₃) was used as the metal precursor and Cts and PEG were used as solid support and polymeric stabilizer, respectively. The antibacterial activity of silver–chitosan–poly(ethylene glycol) nanocomposites (Ag–Cts–PEG NCs) against Staphylococcus aureus, Micrococcus luteum, Pseudomonas aeruginosa, and Escherichia coli was tested by use of the Mueller–Hinton agar disk-diffusion method. Formation of AgNPs was determined by UV–visible spectroscopy; surface plasmon absorption maxima were observed at 415–430 nm in the UV–visible spectrum. The peaks in the XRD pattern confirmed that the AgNPs had a face-centered cubic structure; peaks of contaminated crystalline phases were not observed. Transmission electron microscopy (TEM) revealed that the AgNPs synthesized were spherical. The optimum stirring time for synthesis of the smallest particle size (mean diameter 5.50 nm) was 12 h. The AgNPs in Cts–PEG were effective against all the bacteria tested. Higher antibacterial activity was observed for AgNPs with smaller size. These results suggest that AgNPs can be used as an effective inhibitor of bacteria and can be used in medical applications. These results also suggest that AgNPs were successfully synthesized in Cts–PEG suspension at moderate temperature with different stirring times.     

Antibacterial Activity and Synergistic Effect of Biosynthesized AgNPs with Antibiotics Against Multidrug-Resistant Biofilm-Forming Coagulase-Negative Staphylococci Isolated from Clinical Samples

Silver nanoparticles form promising template for designing antimicrobial agents against drug resistant pathogenic microorganisms. Thus, the development of a reliable green approach for the synthesis of nanoparticles is an important aspect of current nanotechnology research. In the present investigation, silver nanoparticles synthesized by a soil Bacillus sp. were characterized using UV–vis spectroscopy, FTIR, SEM, and EDS. The antibacterial potential of biosynthesized silver nanoparticles, standard antibiotics, and their conjugates were evaluated against multidrug-resistant biofilm-forming coagulase-negative S. epidermidis strains, S. aureus, Salmonella Typhi, Salmonella Paratyphi, and V. cholerae. Interestingly, silver nanoparticles (AgNPs) showed remarkable antibacterial activity against all the test strains with the highest activity against S. epidermidis strains 145 and 152. In addition, the highest synergistic effect of AgNPs was observed with chloramphenicol against Salmonella typhi. The results of the study clearly indicate the promising biomedical applications of biosynthesized AgNPs.     

Green Synthesized Silver Nanoparticles Immobilized on Activated Carbon Nanoparticles: Antibacterial Activity Enhancement Study and Its Application on Textiles Fabrics

This research aimed to enhance the antibacterial activity of silver nanoparticles (AgNPs) synthesized from silver nitrate (AgNO₃) using aloe vera extract. It was performed by means of incorporating AgNPs on an activated carbon nanoparticle (ACNPs) under ultrasonic agitation (40 kHz, 2 × 50 watt) for 30 min in an aqueous colloidal medium. The successful AgNPs synthesis was clarified with both Ultraviolet-Visible (UV-Vis) and Fourier Transform Infrared (FTIR) spectrophotometers. The successful AgNPs–ACNPs incorporation and its particle size analysis was performed using Transmission Electron Microscope (TEM). The brown color suspension generation and UV-Vis’s spectra maximum wavelength at around 480 nm confirmed the existence of AgNPs. The particle sizes of the produced AgNPs were about 5 to 10 nm in the majority number, which collectively surrounded the aloe vera extract secondary metabolites formed core-shell like nanostructure of 8.20 ± 2.05 nm in average size, while ACNPs themselves were about 20.10 ± 1.52 nm in average size formed particles cluster, and 48.00 ± 8.37 nm in average size as stacking of other particles. The antibacterial activity of the synthesized AgNPs and AgNPs-immobilized ACNPs was 57.58% and 63.64%, respectively (for E. coli); 61.25%, and 93.49%, respectively (for S. aureus). In addition, when the AgNPs-immobilized ACNPs material was coated on the cotton and polyester fabrics, the antibacterial activity of the materials changed, becoming 19.23% (cotton; E. coli), 31.73% (polyester; E. coli), 13.36% (cotton; S. aureus), 21.15% (polyester; S. aureus).     

Biogenic Silver Nanoparticles from Two Varieties of Agaricus bisporus and Their Antibacterial Activity

Agaricus bisporus, the most widely cultivated mushroom, is safe to eat and enriched with protein and secondary metabolites. We prepared silver nanoparticles (AgNPs) from two varieties of A. bisporus and tested their antibacterial activity The synthesized AgNPs were initially confirmed by UV-Vis spectroscopy peaks at 420 and 430 nm for white and brown mushrooms AgNPs, respectively. AgNPs were further characterized by zeta sizer, transmission electronic microscopy (TEM), Fourier transform infrared (FTIR), and energy-dispersive X-ray spectroscopy (EDX) prior to antibacterial activity by the well diffusion method against six bacterial strains which include Staphylococcus aureus, Staphylococcus epidermis, Bacillus subtilis, Escherichia coli, Salmonella typhi, and Pseudomonas aeruginosa. TEM results revealed a spherical shape with an average diameter of about 11 nm in the white mushroom extract and 5 nm in the brown mushroom extract. The presence of elemental silver in the prepared AgNPs was confirmed by EDS. The IR spectrum of the extract confirmed the presence of phenols, flavonoids, carboxylic, or amide groups which aided in the reduction and capping of synthesized AgNPs. The AgNPs from both extracts showed almost the same results; however, nanoparticles prepared from brown mushrooms were smaller in size with strong antibacterial activity.     

Green synthesis of silver nanoparticles using olive leaf extract and its antibacterial activity

The silver nanoparticles (AgNPs) synthesized using hot water olive leaf extracts (OLE) as reducing and stabilizing agent are reported and evaluated for antibacterial activity against drug resistant bacterial isolates. The effect of extract concentration, contact time, pH and temperature on the reaction rate and the shape of the Ag nanoparticles are investigated. The data revealed that the rate of formation of the nanosilver increased significantly in the basic medium with increasing temperature. The nature of AgNPs synthesized was analyzed by UV–vis spectroscopy, X-ray diffraction, scanning electron microscopy and thermal gravimetric analysis (TGA). The silver nanoparticles were with an average size of 20–25 nm and mostly spherical. The antibacterial potential of synthesized AgNPs was compared with that of aqueous OLE by well diffusion method. The AgNPs at 0.03–0.07 mg/ml concentration significantly inhibited bacterial growth against multi drug resistant Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli). This study revealed that the aqueous olive leaf extract has no effect at the concentrations used for preparation of the Ag nanoparticles. Thus AgNPs showed broad spectrum antibacterial activity at lower concentration and may be a good alternative therapeutic approach in future.     

Synthesis of Silver Nanoparticles from Extracts of Wild Ginger (Zingiber zerumbet) with Antibacterial Activity against Selective Multidrug Resistant Oral Bacteria

Antibiotic resistance rate is rising worldwide. Silver nanoparticles (AgNPs) are potent for fighting antimicrobial resistance (AMR), independently or synergistically. The purpose of this study was to prepare AgNPs using wild ginger extracts and to evaluate the antibacterial efficacy of these AgNPs against multidrug-resistant (MDR) Staphylococcus aureus, Streptococcus mutans, and Enterococcus faecalis. AgNPs were synthesized using wild ginger extracts at room temperature through different parameters for optimization, i.e., pH and variable molar concentration. Synthesis of AgNPs was confirmed by UV/visible spectroscopy and further characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy analysis (EDXA), and Fourier-transform infrared spectroscopy (FTIR). Disc and agar well diffusion techniques were utilized to determine the in vitro antibacterial activity of plant extracts and AgNPs. The surface plasmon resonance peaks in absorption spectra for silver suspension showed the absorption maxima in the range of 400–420 nm. Functional biomolecules such as N–H, C–H, O–H, C–O, and C–O–C were present in Zingiber zerumbet (Z. zerumbet) (aqueous and organic extracts) responsible for the AgNP formation characterized by FTIR. The crystalline structure of ZZAE-AgCl-NPs and ZZEE-AgCl-NPs was displayed in the XRD analysis. SEM analysis revealed the surface morphology. The EDXA analysis also confirmed the element of silver. It was revealed that AgNPs were seemingly spherical in morphology. The biosynthesized AgNPs exhibited complete antibacterial activity against the tested MDR bacterial strains. This study indicates that AgNPs of wild ginger extracts exhibit potent antibacterial activity against MDR bacterial strains.     

Biosynthesis of silver nanoparticle using flowers of Calotropis gigantea (L.) W.T. Aiton and activity against pathogenic bacteria

Silver nanoparticles (AgNPs) from silver nitrate solution are carried out using the flower extract of Calotropis gigantea. Silver nanoparticles were characterized by UV–vis spectrophotometer, X-Ray diffractometer (XRD). Reduction of silver ions in the aqueous solution of silver during the reaction was observed by UV–vis spectroscopy. Crystalline nature of synthesized silver nanoparticles was studied by XRD pattern, refraction peak using the Scherrer’s equation. Antibacterial activity of the silver nanoparticles was performed by disc diffusion method against Bacillus subtilis, Pseudomonas putida and Escherichia coli. The antibacterial activity of synthesized silver nanoparticles by flower extract of C. gigantea was found against B. subtilis (10 mm). Synthesised AgNPs has the efficient antibacterial activity against Gram positive bacteria.     

In Vitro Antibacterial Activity of Green Synthesized Silver Nanoparticles Using Azadirachta indica Aqueous Leaf Extract against MDR Pathogens

Rice is the most important staple food crop feeding more than 50% of the world’s population. Rice blast is the most devastating fungal disease, caused by Magnaporthe oryzae (M. oryzae) which is widespread in rice growing fields causing a significant reduction in the yield. The present study was initiated to evaluate the effect of green synthesized silver nanoparticles (AgNPs) on the biochemical constituents of rice plants infected with blast. AgNPs were synthesized by using Azadirachta indica leaf extract and their characterization was performed using UV-visible spectroscopy, particle size analyser (PSA), scanning electron microscope (SEM), and X-ray diffraction (XRD) which confirmed the presence of crystalline, spherical shaped silver nanoparticles with an average size of 58.9 nm. After 45 days of sowing, artificial inoculation of rice blast disease was performed. After the onset of disease symptoms, the plants were treated with AgNPs with different concentrations. Application of nanoparticles elevated the activity of antioxidative enzymes such as superoxide dismutase, catalase, peroxidase, glutathione reductase, and phenylalanine ammonia-lyase compared to control plants, and total phenol and reducing sugars were also elevated. The outcome of this study showed that an increase in all biochemical constituents was recorded for A. indica silver nanoparticles-treated plants. The highest values were recorded in 30 ppm and 50 ppm AgNPs-treated plants, which showed the highest resistance towards the pathogen. Green synthesized AgNPs can be used in future for disease control in susceptible varieties of rice. The synthesized AgNPs using A. indica leaf extract have shown promising antibacterial activity when tested against 14 multidrug-resistant (MDR) bacteria comprising Gram-negative bacteria Escherichia coli (n = 6) and Klebsiella pneumoniae (n = 7) with a good zone of inhibition diameter, tested with the disc diffusion method. Based on these findings, it appears that A. indica AgNPs have promise as an antibacterial agent effective against MDR pathogens.     

Antimicrobial and cytotoxicity properties of biosynthesized gold and silver nanoparticles using D. brittonii aqueous extract

Recently, the production of nanoparticles using biological resources has gained considerable attention due to their application for animal and human well-being. In this study, we used a green synthesis to fabricate gold and silver nanoparticles by reducing HAuCl₄ and AgNO₃ into AuNPs and AgNPs, respectively, using Dudleya brittonii (DB) extract. The physio-chemical properties of the synthesized nanoparticles were analyzed using a UV–vis spectrophotometer, FESEM, EDX, HR-TEM, AFM and FT-IR. Furthermore, the antimicrobial and cytotoxicity activities of DB-AuNPs and DB-AgNPs against livestock pathogenic bacteria and different cell lines, as well as anti-oxidant activity, were investigated. DB synthesized AuNPs and AgNPs were mostly spherical with a few triangular rods and sizes ranging of 5–25 nm and 10–40 nm, respectively. The in vitro antibacterial and antifungal studies demonstrated the DB-AuNPs and DB-AgNPs have good antibacterial activity against E. coli and other livestock pathogens, including Y. pseudotuberculosis and S. typhi. Cell studies revealed that the higher concentrations of both DB-AuNPs and DB-AgNPs (1 µg/ml to 1 mg/ml) showed potent cytotoxicity in chicken cells after 24 hrs, whereas the middle and lower concentrations of DB-AuNPs and DB-AgNPs did not show cytotoxicity in selected cell lines after 24 hrs. In addition, the DB synthesized AuNPs and AgNPs exhibited good free scavenging activity in a dose-dependent manner. Therefore, the biosynthesized nanoparticles can be utilized by the livestock industry to develop an effective source against livestock microbial infections.     

Biosynthesis of Bixa orellana seed extract mediated silver nanoparticles with moderate antioxidant,antibacterial and antiproliferative activity

Biosynthesis of metallic silver nanoparticles (AgNPs) has gained much interest and offers an attractive alternate to physical and chemical approaches. In recent year several safe, easy, cost-effective, reproducible, and environmentally friendly synthesis approaches for silver nanoparticles have been developed. In this research work, a simple, cheap, and unexplored method was applied on green synthesis of AgNPs using secondary metabolites extracted from Bixa orellana seeds. The seeds are rich of flavonoids and phenolic compounds which presumably responsible for the fast reduction and stabilization of silver ion into silver nanoparticles. The biosynthesis process is very likely to be able to reduce silver ions under simple physiological conditions. The surface plasmon resonance (SPR) that was appeared at 420 nm in UV–vis spectrum, had confirmed the formation of AgNPs. Moreover, the functional groups in secondary metabolite that act as reducing, capping and stabilizing agents for silver nanoparticles, are identified by Fourier transform infrared (FTIR) spectra. An X-ray diffraction analysis generated four peaks for Bixa orellana seed extract mediated AgNPs positioned at 2θ angles of 38.1°, 44.2°, 64.6°, and 77.5° corresponding to crystal planes (1 1 1), (2 0 0), (2 2 0), and (3 1 1). Field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) images confirmed the formation of nanosized silver particles. The z-average of the synthesized particles measured by dynamic light scattering (DLS) was found to be 92.9 nm. AgNPs synthesized exhibited remarkable antioxidant activity, antibacterial and antiproliferative activity against human breast (MCF-7) cell line. On the basis of our results, we conclude that biologically synthesized AgNPs exhibited favorable characteristics and have the potential to be used in biomedical fields.     

Antioxidant and antibacterial activity of silver nanoparticles biosynthesized using Chenopodium murale leaf extract

Silver is known for its antimicrobial effects and silver nanoparticles are gaining their importance due to their antimicrobial activities. The aims of the current study were to use plant extract for the biosynthesis of silver nanoparticles and to evaluate their antibacterial and antioxidant activity in vitro. The results indicated that silver nanoparticles (AgNPs) can be synthesized in a simple method using Chenopodium murale leaf extract. The TEM analysis showed that the sizes of the synthesized AgNps ranged from 30 to 50 nm. The essential oil of C. murale leaf extract was formed mainly of α-Terpinene, (Z)-Ascaridole and cis-Ascaridole. The total phenolic compounds and total flavonides were higher in AgNPs-containing plant extract compared to the plant extract. AgNPs-containing leaf extract showed a higher antioxidant and antimicrobial activity compared to C. murale leaf extract alone or silver nitrate. It could be concluded that C. murale leaf extract can be used effectively in the production of potential antioxidant and antimicrobial AgNPs for commercial application.     

Alga-mediated facile green synthesis of silver nanoparticles: Photophysical,catalytic and antibacterial activity

A facile, convenient and green method has been employed for the synthesis of silver nanoparticles (AgNPs) using dried biomass of a green alga, Chlorella ellipsoidea. The phytochemicals from the alga, as a mild and non-toxic source, are believed to serve as both reducing and stabilizing agents. The formation of silver nanoparticles was confirmed from the appearance of a surface plasmon resonance band at 436 nm and energy dispersive X-ray spectroscopy. The transmission electron microscopy images showed the nanoparticles to be nearly spherical in shape with different sizes. A dynamic light scattering study revealed the average particle size to be 220.8 ± 31.3 nm. Fourier transform infrared spectroscopy revealed the occurrence of alga-derived phytochemicals attached to the outer surface of biogenically accessed silver nanoparticles. The powder X-ray diffraction study revealed the face-centred cubic crystalline structure of the nanoparticles. The as-synthesized biomatrix-loaded AgNPs exhibited a high photocatalytic activity for the degradation of the hazardous pollutant dyes methylene blue and methyl orange. The catalytic efficiency was sustained even after three reduction cycles. A kinetic study indicated the degradation rates to be pseudo-first order with the degradation rate being 4.72 × 10⁻² min⁻¹ for methylene blue and 3.24 × 10⁻² min⁻¹ for methyl orange. The AgNPs also exhibited significant antibacterial activity against four selected pathogenic bacterial strains.     

Green Synthesis of Silver Nanoparticles Using the Plant Extract of Acer oblongifolium and Study of Its Antibacterial and Antiproliferative Activity via Mathematical Approaches

In this study, the antibacterial and antifungal properties of silver nanoparticles synthesized with the aqueous plant extract of Acer oblongifolium leaves were defined using a simplistic, environmentally friendly, reliable, and cost-effective method. The aqueous plant extract of Acer oblongifolium, which served as a capping and reducing agent, was used to biosynthesize silver nanoparticles. UV visible spectroscopy, X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and scanning electron microscopy were used to analyze the biosynthesized Acer oblongifolium silver nanoparticles (AgNPs). Gram-positive bacteria (Bacillus paramycoides and Bacillus cereus) and Gram-negative bacteria (E. coli) were used to test the AgNPs’ antibacterial activity. The presence of different functional groups was determined by FTIR. The AgNPs were rod-like in shape. The nanoparticles were more toxic against Escherichia coli than both Bacillus cereus and Bacillus paramycoides. The AgNPs had IC₅₀ values of 6.22 and 9.43 and mg/mL on HeLa and MCF-7, respectively, proving their comparatively strong potency against MCF-7. This confirmed that silver nanoparticles had strong antibacterial activity and antiproliferative ability against MCF-7 and HeLa cell lines. The mathematical modeling revealed that the pure nanoparticle had a high heat-absorbing capacity compared to the mixed nanoparticle. This research demonstrated that the biosynthesized Acer oblongifolium AgNPs could be used as an antioxidant, antibacterial, and anticancer agent in the future.     

Antibacterial and antibiofilm activity of nanochelating based silver nanoparticles against several nosocomial pathogens

The emergence of multi‐drug resistant (MDR) bacteria and dynamic pattern of infectious diseases demand to develop alternative and more effective therapeutic strategies. Silver nanoparticles (AgNPs) are among the most widely commercialized engineered nanomaterials, because of their unique properties and increasing use for various applications in nanomedicine. This study for the first time aimed to evaluate the antibacterial and antibiofilm activities of newly synthesized nanochelating based AgNPs against several Gram‐positive and ‐negative nosocomial pathogens. Nanochelating technology was used to design and synthesize the AgNPs. The cytotoxicity was tested in human cell line using the MTT assay. AgNPs minimal inhibitory concentration (MIC) was determined by standard broth microdilution. Antibiofilm activity was assayed by a microtiter‐plate screening method. The two synthesized AgNPs including AgNPs (A) with the size of about 20‐25 nm, and AgNPs (B) with 30‐35 nm were tested against Staphylococcus aureus, Staphylococcus epidermidis, Acinetobacter baumannii, and Pseudomonas aeruginosa. AgNPs exhibited higher antibacterial activity against Gram‐positive strains. AgNPs were found to significantly inhibit the biofilm formation of tested strains in concentration 0.01 to 10 mg/mL. AgNPs (A) showed significant effective antibiofilm activity compared to AgNPs (B). In summary, our results showed the promising antibacterial and antibiofilm activity of our new nanochelating based synthesized AgNPs against several nosocomial pathogens.     

Biosynthesis,Characterization and Antibacterial Application of Novel Silver Nanoparticles against Drug Resistant Pathogenic Klebsiella pneumoniae and Salmonella Enteritidis

The present study highlights the biosynthesis of silver nanoparticles (AgNPs) using culture supernatant of Massilia sp. MAHUQ-52 as well as the antimicrobial application of synthesized AgNPs against multi-drug resistant pathogenic Klebsiella pneumoniae and Salmonella Enteritidis. Well-defined AgNPs formation occurred from the reaction mixture of cell-free supernatant and silver nitrate (AgNO₃) solution within 48 h of incubation. UV-visible spectroscopy analysis showed a strong peak at 435 nm, which corresponds to the surface plasmon resonance of AgNPs. The synthesized AgNPs were characterized by FE-TEM, EDX, XRD, DLS and FT-IR. From FE-TEM analysis, it was found that most of the particles were spherical shape, and the size of synthesized nanoparticles (NPs) was 15–55 nm. EDX spectrum revealed a strong silver signal at 3 keV. XRD analysis determined the crystalline, pure, face-centered cubic AgNPs. FT-IR analysis identified various functional molecules that may be involved with the synthesis and stabilization of AgNPs. The antimicrobial activity of Massilia sp. MAHUQ-52 mediated synthesized AgNPs was determined using the disk diffusion method against K. pneumoniae and S. Enteritidis. Biosynthesized AgNPs showed strong antimicrobial activity against both K. pneumoniae and S. Enteritidis. The MICs of synthesized AgNPs against K. pneumoniae and S. Enteritidis were 12.5 and 25.0 μg/mL, respectively. The MBC of biosynthesized AgNPs against both pathogens was 50.0 μg/mL. From FE-SEM analysis, it was found that the AgNPs-treated cells showed morphological changes with irregular and damaged cell walls that culminated in cell death.     

Green Synthesis of Silver Nanoparticles Using Euphorbia wallichii Leaf Extract: Its Antibacterial Action against Citrus Canker Causal Agent and Antioxidant Potential

Biologically synthesized silver nanoparticles are emerging as attractive alternatives to chemical pesticides due to the ease of their synthesis, safety and antimicrobial activities in lower possible concentrations. In the present study, we have synthesized silver nanoparticles (AgNPs) using the aqueous extract of the medicinal plant Euphorbia wallichii and tested them against the plant pathogenic bacterium Xanthomonas axonopodis, the causative agent of citrus canker, via an in vitro experiment. The synthesized silver nanoparticles were characterized by techniques such as UV-Vis spectroscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis and transmission electron microscopy. Moreover, the plant species were investigated for phenolics, flavonoids and antioxidant activity. The antioxidant potential of the extract was determined against a DPPH radical. The extract was also evaluated for phenolic compounds using the HPLC technique. The results confirmed the synthesis of centered cubic, spherical-shaped and crystalline nanoparticles by employing standard characterization techniques. A qualitative and quantitative phytochemical analysis revealed the presence of phenolics (41.52 mg GAE/g), flavonoids (14.2 mg QE/g) and other metabolites of medicinal importance. Different concentrations (1000 µg/mL to 15.62 µg/mL—2 fold dilutions) of AgNPs and plant extract (PE) alone, and both in combination (AgNPs-PE), exhibited a differential inhibition of X. axanopodis in a high throughput antibacterial assay. Overall, AgNPs-PE was superior in terms of displaying significant antibacterial activity, followed by AgNPs alone. An appreciable antioxidant potential was recorded as well. The observed antibacterial and antioxidant potential may be attributed to eight phenolic compounds identified in the extract. The Euphorbia wallichii leaf-extract-induced synthesized AgNPs exhibited strong antibacterial activity against X. axanopodis, which could be exploited as effective alternative preparations against citrus canker in planta in a controlled environment. In addition, as a good source of phenolic compounds, the plant could be further exploited for potent antioxidants.     

Green synthesis of silver nanoparticles by bloom forming marine microalgae Trichodesmium erythraeum and its applications in antioxidant,drug-resistant bacteria,and cytotoxicity activity

In the present study, we developed an eco-friendly method of stable silver nanoparticles (AgNPs) production using the aqueous extract of Trichodesmium erythraeum. The biosynthesized AgNPs were characterized using UV–Vis spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Energy-Dispersive X-ray (EDX), and X-ray diffraction (XRD). The results affirmed that synthesized AgNPs were crystalline in nature, cubical in shape, and the average size of T. erythraeum silver nanoparticles (TENPs) was 26.5 nm. The antioxidant potential of synthesized AgNPs (500 µg/ml) was 77.01 ± 0.17% in DPPH, 67.5 ± 0.22% in Deoxy-ribose, 52.77 ± 0.42% in ABTS and 88.12 ± 0.26% in nitric oxide radical scavenging assays. The antibacterial results showed excellent inhibition against the clinical strains (Staphylococcus aureus and Proteus mirabilis) and drug-resistant bacterial strains such as E. coli (Amikacin^R), S. aureus (Tetracycline^R) and S. pneumoniae (Penicillin^R). The maximum anti-proliferative effect of TENPs was seen using 50 µg concentration against He La and MCF-7 cell lines, and IC₅₀ values were 25.0 ± 0.50 µg/ml and 30.0 ± 0.50 µg/ml, respectively, at 24 h.     

In situ generation of silver nanoparticles in cellulose matrix using Azadirachta indica leaf extract as a reducing agent

In the present work, silver nanoparticles (AgNPs) were in situ generated in cellulose matrix using leaf extract of Azadirachta indica as a reducing agent. The cellulose/AgNP composite films prepared were characterized by FTIR, X-ray diffraction (XRD), scanning electron microscope, and antibacterial tests. The infrared spectra indicated the association of organic materials with silver nanoparticles to serve as capping agents. Scanning electron micrographs showed that synthesized silver nanoparticles were nearly uniform and spherical in shape with diameter in the range of 61–110?nm. XRD confirmed the formation of AgNPs and Ag–O nanoparticles. The nanocomposite films showed good antibacterial activity against Escherichia coli bacteria.