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 by using eugenol and evaluation of antimicrobial potential

The importance of green synthesis was revealed with advantages such as: eliminating the use of expensive chemicals; consume less energy; and generate environmentally benign products. With this aim, silver nanoparticles (AgNPs) were synthesized by using isolated eugenol from clove extract. Its antimicrobial potential was determined on three different microorganisms. Clove was extracted and eugenol was isolated from this extract. Green synthesis was performed and an anti‐microbial study was performed. All extraction and isolation analyses were performed by high‐performance liquid chromatography (HPLC); identification and confirmation were achieved using liquid chromatography–mass spectrometry (LC–MS); and scanning electron microscopy was used for characterization. Both HPLC and LC–MS analyses showed that eugenol obtained purely synthesized AgNPs and 20‐25‐nm‐sized and homogeneous shaped particles seen in images. The antimicrobial effects of AgNPs at eight concentrations were determinated against Staphylococcus aureus, Escherichia coli and Candida albicans, and maximum inhibition zone diameters were found as 2.6 cm, 2.4 cm and 1.5 cm, respectively. The results of the antimicrobial study showed that eugenol as a biological material brought higher antimicrobial effect to AgNPs in comparison to the other materials found in the literature.     

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.     

Phytogenic-mediated silver nanoparticles using Persicaria hydropiper extracts and its catalytic activity against multidrug resistant bacteria

Multidrug resistance (MDR) is one of the major global threats of this century. So new innovative approaches are needed for the development of existing antibiotics to limit antibacterial resistance. The current study was aimed to utilize extracts of root, stem, and leaves of Persicaria hydropiper for the synthesis of silver nanoparticles (AgNPs) using standard procedure. Synthesis of AgNPs was evident from the change in color of the solution to dark brownish and then it was further revealed by UV–Vis and Fourier Transformed Infrared Spectroscopy (FTIR). UV–Vis spectroscopy has revealed absorbance peak at 370 nm while, FTIR spectrum displayed that aromatics amines were used as reducing agent in the fabrication of AgNPs. In addition, Scanning Electron Microscopy (SEM micrograph) displaying tetrahedron, spherical and oval shapes of synthesized AgNPs whereas, average size of synthesized AgNPs was found in the range of 32–77 nm. Beside this, it was also observed that the potency of antibiotics against MDR bacteria increased after coating with synthesized AgNPs i.e., the potency of Ceftazidime and Ciprofloxacin increased up to 450% and 500% against Bacillus respectively while, the potency of Gentamicin, Vancomycin and Linezolid increased up to 150%, 200% and 58% against Bacillus, Staphylococcus, and Proteus species respectively. Furthermore, it was concluded that utilizing AgNPs in combination with commercially available antibiotics would provide an alternate therapy for the treatment of infectious diseases caused by MDR bacteria.     

Green Synthesis and Characterization of Silver Nanoparticles Using Spondias mombin Extract and Their Antimicrobial Activity against Biofilm-Producing Bacteria

Multidrug resistant bacteria create a challenging situation for society to treat infections. Multidrug resistance (MDR) is the reason for biofilm bacteria to cause chronic infection. Plant-based nanoparticles could be an alternative solution as potential drug candidates against these MDR bacteria, as many plants are well known for their antimicrobial activity against pathogenic microorganisms. Spondias mombin is a traditional plant which has already been used for medicinal purposes as every part of this plant has been proven to have its own medicinal values. In this research, the S. mombin extract was used to synthesise AgNPs. The synthesized AgNPs were characterized and further tested for their antibacterial, reactive oxygen species and cytotoxicity properties. The characterization results showed the synthesized AgNPs to be between 8 to 50 nm with -11.52 of zeta potential value. The existence of the silver element in the AgNPs was confirmed with the peaks obtained in the EDX spectrometry. Significant antibacterial activity was observed against selected biofilm-forming pathogenic bacteria. The cytotoxicity study with A. salina revealed the LC50 of synthesized AgNPs was at 0.81 mg/mL. Based on the ROS quantification, it was suggested that the ROS production, due to the interaction of AgNP with different bacterial cells, causes structural changes of the cell. This proves that the synthesized AgNPs could be an effective drug against multidrug resistant bacteria.     

Biosynthesis,characterization, and antimicrobial effect of silver nanoparticles obtained using <Emphasis Type="Italic">Lavandula</Emphasis> × <Emphasis Type="Italic">intermedia</Emphasis>

The use..... of aqueous leaf extract of Lavandula × intermedia for biosynthesis of silver nanoparticles (AgNPs) is presented. The plant extract was obtained by boiling dried leaves and using the obtained filtrate for the synthesis of AgNPs. The study was conducted to investigate an ecofriendly approach to metal nanoparticle synthesis and to evaluate the antimicrobial potential of both the aqueous plant extract and resulting silver nanoparticles against different microbes using the disc diffusion method. The synthesis of silver nanoparticles was monitored using ultraviolet–visible (UV–v is) spectroscopy, which showed a localized surface plasmon resonance band at 411 nm and a shift of the band to higher wavenumber of 422 nm after 90 min of reaction. Powder X-ray diffraction analysis and transmission electron microscopy of the obtained AgNPs revealed their crystalline nature, with average size of 12.6 nm. Presence of elemental silver was further confirmed by energy-dispersive X-ray spectroscopy. Fourier-transform infrared spectroscopy confirmed presence of phytochemicals from Lavandula × intermedia leaf extract on the AgNPs. The AgNPs showed good antimicrobial activity with inhibition zone ranging from 10 to 23 mm; the largest inhibition zone (23 mm) occurred against Escherichia coli. Generally, the AgNPs displayed more antimicrobial activity against all investigated pathogens compared with Lavandula × intermedia leaf extract, and were also more active than streptomycin against Klebsiella oxytoca and E. coli at the same concentration. The silver nanoparticles showed prominent antimicrobial activity with a lowest minimum inhibitory concentration (MIC) value of 15 μg/mL against E. coli, K. oxytoca, and Candida albicans.     

Nanocomposites based on cationic polyelectrolytes and silver nanoparticles: Synthesis,characterization, molybdate retention and antimicrobial activity

The objective of this work was to synthesize nanocomposites based on cationic polyelectrolytes and silver nanoparticles using poly(N-vinylbenzyl-N-triethylammonium chloride) as polymer phase. For that, a nanostructured crosslinker was synthesized from silver nanoparticles (AgNPs) and acrylic acid. Molybdate retention properties of nanocomposites were studied in function of pH and ionic strength. In addition, their antimicrobial properties were evaluated against E. coli and S. aureus. It was evidenced that AgNPs can be stabilized using acrylic acid and that this material can be incorporated to the polymer phase during polymerization by free radical of cationic monomers. The effect of pH on retention of molybdate, by the nanostructured polymer, was significant only to low ionic strength (the order seen was pH 5.0 > pH 7.0 > pH 9.0 for 0.0% NaCl). Results suggest that the main interaction influencing the molybdate retention is electrostatic in nature. Finally, antimicrobial activity was enhanced by incorporation of polymerizable nanostructured crosslinker based on AgNPs.     

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.     

Biogenic Synthesis of Silver Nanoparticles with High Antimicrobial and Catalytic Activities using Sheng Di Huang (Rehmannia glutinosa)

Silver nanoparticles (AgNPs) are widely sought after for a variety of biomedical and environmental applications due to their antimicrobial and catalytic properties. We present here a green and simple synthesis of AgNPs utilizing traditional Chinese medicinal herbs. The screening of 20 aqueous herb extracts shows that Sheng Di Huang (Rehmannia glutinosa) had the most promising potential in producing AgNPs of 30±6 nm, with narrow size distribution and high crystallinity. The antimicrobial activities of these AgNPs conducted on E. coli cells were found to be superior in comparison to poly(vinylpyrrolidone)-capped AgNPs synthesized using common chemical method. Additionally, the AgNPs obtained possess excellent catalytic performance in the reduction of 4-nitrophenol to 4-aminophenol. We compared the phytochemical and FTIR spectral analyses of the herb extract before and after synthesis, in order to elucidate the phytochemicals responsible for the reduction of Ag⁺ ions and the capping of the AgNPs produced.     

Synthesis of Gossypium hirsutum‐derived silver nanoparticles and their antibacterial efficacy against plant pathogens

Malvaceae and Brassicaceae family crops are economically important; however, their production has been markedly decreased in recent years due to various plant pests. Hence, the search for novel classes of efficient biological approaches continues due to unavailability of precise pesticides. The present study was designed to synthesize, characterize and evaluate the efficacy of silver nanoparticles (AgNPs) obtained using stem extract of Gossypium hirsutum (cotton plant) against plant pathogens Xanthomonas axonopodis pv. malvacearum and Xanthomonas campestris pv. campestris. Biosynthesized AgNPs were characterized using UV–visible spectrophotometry, Dynamic Light Scattering, Scanning Electron Microscopy combined with energy‐dispersive X‐ray analysis and Fourier transform infrared spectroscopy. The synthesized AgNPs were spherical in shape with size ranging from 20 to 100 nm. The characterized AgNPs were investigated for their efficacy against bacterial plant pathogens using the paper disc method. In vitro studies with two concentrations of AgNPs (50 and 100 μg mL^?1) showed zone of inhibition 11.0 ± 1.0 and 12.3 ± 0.5 mm for X. axonopodis pv. malvacearum and 9.7 ± 0.6 and 15.33 ± 1.0 mm for X. campestris pv. campestris. Furthermore, the AgNPs exhibited strong antioxidant activity, and a phytotoxicity study on Vigna unguiculata (cowpea plant) showed no toxicity. Overall, the findings suggest that G. hirsutum stem extract could be efficiently used in the synthesis of AgNPs and showed antimicrobial activity against plant pathogens. Hence, the synthesized nanoparticles could be used to combat plant pathogens in the agriculture sector.     

Phyto-Extract-Mediated Synthesis of Silver Nanoparticles Using Aqueous Extract of Sanvitalia procumbens,and Characterization,Optimization and Photocatalytic Degradation of Azo Dyes Orange G and Direct Blue-15

Green synthesis of silver nanoparticles (AgNPs) employing an aqueous plant extract has emerged as a viable eco-friendly method. The aim of the study was to synthesize AgNPs by using plant extract of Sanvitalia procumbens (creeping zinnia) in which the phytochemicals present in plant extract act as a stabilizing and reducing agent. For the stability of the synthesized AgNPs, different parameters like AgNO₃ concentration, volume ratios of AgNO₃, temperature, pH, and contact time were studied. Further, AgNPs were characterized by UV–visible spectroscopy, FT-IR (Fourier Transform Infrared Spectroscopy), XRD (X-ray Diffraction), SEM (Scanning Electron Microscopy), and EDX (Energy Dispersive X-ray Spectrometer) analysis. FT-IR analysis showed that the plant extract contained essential functional groups like O–H stretching of carboxylic acid, N–H stretching of secondary amides, and C–N stretching of aromatic amines, and C–O indicates the vibration of alcohol, ester, and carboxylic acid that facilitated in the green synthesis of AgNPs. The crystalline nature of synthesized AgNPs was confirmed by XRD, while the elemental composition of AgNPs was detected by energy dispersive X-ray analysis (EDX). SEM studies showed the mean particle diameter of silver nanoparticles. The synthesized AgNPs were used for photocatalytic degradation of Orange G and Direct blue-15 (OG and DB-15), which were analyzed by UV-visible spectroscopy. Maximum degradation percentage of OG and DB-15 azo dyes was observed, without any significant silver leaching, thereby signifying notable photocatalytic properties of AgNPs.     

Green Synthesis of Silver Nanoparticles by Extracellular Extracts from Aspergillus japonicus PJ01

The present study focuses on the biological synthesis, characterization, and antibacterial activities of silver nanoparticles (AgNPs) using extracellular extracts of Aspergillus japonicus PJ01.The optimal conditions of the synthesis process were: 10 mL of extracellular extracts, 1 mL of AgNO₃ (0.8 mol/L), 4 mL of NaOH solution (1.5 mol/L), 30 °C, and a reaction time of 1 min. The characterizations of AgNPs were tested by UV-visible spectrophotometry, zeta potential, scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric (TG) analyses. Fourier transform infrared spectroscopy (FTIR) analysis showed that Ag⁺ was reduced by the extracellular extracts, which consisted chiefly of soluble proteins and reducing sugars. In this work, AgNO₃ concentration played an important role in the physicochemical properties and antibacterial properties of AgNPs. Under the AgNO₃ concentration of 0.2 and 0.8 mol/L, the diameters of AgNPs were 3.8 ± 1.1 and 9.1 ± 2.9 nm, respectively. In addition, smaller-sized AgNPs showed higher antimicrobial properties, and the minimum inhibitory concentration (MIC) values against both E. coli and S. aureus were 0.32 mg/mL.     

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.     

Development of silver-containing nanocellulosics for effective water disinfection

Electrospun cellulose nanofibers and cellulose-graft-polyacrylonitrile (Cell-g-PAN) copolymer nanofibers containing silver nanoparticles (AgNPs) were synthesized for effective water disinfection. Surface morphology, AgNPs content, physical distribution of AgNPs, levels of silver leaching from the fibers in water and antimicrobial efficacy were studied. Scanning electron microscope images revealed that AgNPs in cellulose nanofibers were more evenly dispersed than in Cell-g-PAN copolymer nanofibers, but with the certainty that Cell-g-PAN copolymer nanofibers had higher AgNPs content. This was confirmed by energy dispersive X-ray analysis and atomic absorption analysis. Both cellulose nanofibers and Cell-g-PAN copolymer nanofibers containing AgNPs had excellent antimicrobial activity against Escherichia coli, Salmonella typhi, and Staphylococcus aureus, with cellulose-nAg nanofibers killing between 91 and 99 % of bacteria in a contaminated water sample and Cell-g-PAN-nAg copolymer nanofibers killed 100 %. Neither Cell-g-PAN copolymer nanofibers nor cellulose nanofibers leached silver into water.     

Study of Antibacterial and Anticancer Properties of bioAgNPs Synthesized Using Streptomyces sp. PBD-311B and the Application of bioAgNP-CNC/Alg as an Antibacterial Hydrogel Film against P. aeruginosa USM-AR2 and MRSA

Here, we report the extracellular biosynthesis of silver nanoparticles (AgNPs) and determination of their antibacterial and anticancer properties. We also explore the efficacy of bioAgNPs incorporated in cellulose nanocrystals (CNCs) and alginate (Alg) for the formation of an antibacterial hydrogel film. Streptomyces sp. PBD-311B was used for the biosynthesis of AgNPs. The synthesized bioAgNPs were characterized using UV-Vis spectroscopy, TEM, XRD, and FTIR analysis. Then, the bioAgNPs’ antibacterial and anticancer properties were determined using TEMA and cytotoxicity analysis. To form the antibacterial hydrogel film, bioAgNPs were mixed with a CNC and Alg solution and further characterized using FTIR analysis and a disc diffusion test. The average size of the synthesized bioAgNPs is around 69 ± 2 nm with a spherical shape. XRD analysis confirmed the formation of silver nanocrystals. FTIR analysis showed the presence of protein capping at the bioAgNP surface and could be attributed to the extracellular protein binding to bioAgNPs. The MIC value of bioAgNPs against P. aeruginosa USM-AR2 and MRSA was 6.25 mg/mL and 3.13 mg/mL, respectively. In addition, the bioAgNPs displayed cytotoxicity effects against cancer cells (DBTRG-0.5MG and MCF-7) and showed minimal effects against normal cells (SVG-p12 and MCF-10A), conferring selective toxicity. Interestingly, the bioAgNPs still exhibited inhibition activity when incorporated into CNC/Alg, which implies that the hydrogel film has antibacterial properties. It was also found that bioAgNP-CNC/Alg displayed a minimal or slow release of bioAgNPs owing to the intermolecular interaction and the hydrogel’s properties. Overall, bioAgNP-CNC/Alg is a promising antibacterial hydrogel film that showed inhibition against the pathogenic bacteria P. aeruginosa and MRSA and its application can be further evaluated for the inhibition of cancer cells. It showed benefits for surgical resection of a tumor to avoid post-operative wound infection and tumor recurrence at the surgical site.     

In Vitro Antioxidant,Antitumor and Photocatalytic Activities of Silver Nanoparticles Synthesized Using Equisetum Species: A Green Approach

The ethanolic extracts of three Equisetum species (E. pratense Ehrh., E. sylvaticum L. and E. telmateia Ehrh.) were used to reduce silver ions to silver nanoparticles (AgNPs). The synthesized AgNPs were characterized using UV-Vis spectrophotometry, Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive X-ray (EDX), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) measurements. FTIR data revealed the functional groups of biomolecules involved in AgNPs synthesis, such as O-H, C-H, C=O, C-O, and C-C. EDX spectroscopy was used to highlight the presence of silver, while DLS spectroscopy provided information on the mean diameter of AgNPs, that ranged from 74.4 to 314 nm. The negative Zeta potential values (−23.76 for Ep–AgNPs, −29.54 for Es–AgNPs and −20.72 for Et–AgNPs) indicate the stability of the obtained colloidal solution. The study also focused on establishing the photocatalytic activity of AgNPs, which is an important aspect in terms of removing organic dyes from the environment. The best photocatalytic activity was observed for AgNPs obtained from E. telmateia, which degraded malachite green in a proportion of 97.9%. The antioxidant action of the three AgNPs samples was highlighted comparatively through four tests, with the best overall antioxidant capacity being observed for AgNPs obtained using E. sylvaticum. Moreover, the biosynthesized AgNPs showed promising cytotoxic efficacy against cancerous cell line MG63, the AgNPs obtained from E. sylvaticum L. providing the best result, with a LD₅₀ value around 1.5 mg/mL.     

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.     

A new green method for the synthesis of silver nanoparticles and their antibacterial activities against gram‐positive and gram‐negative bacteria

This study aims to evaluate the capability of Ageratum conyzoides and Mikania micrantha extracts to synthesize silver nanoparticles (AgNPs) and their antibacterial capability against gram‐positive and gram‐negative bacteria. Several properties of the synthesized AgNPs, including plasmonic, biomolecule bonding, shape, size, and antibacterial, were investigated. Ultraviolet–visible (UV–vis) spectroscopy was employed for characterizing their plasmonic properties. Functional groups on the produced AgNPs were investigated by Fourier‐transform infrared (FT‐IR) spectroscopy. The size and shape of the AgNPs were identified using the field‐emission scanning electron microscopy (FESEM). Inhibition zone measurement was carried out for evaluating the antibacterial capability. This study showed that the extracts of A. conyzoides and M. micrantha were able reducing agents as evidenced by the formation of the spherical AgNPs. UV–vis spectroscopy, FT‐IR spectroscopy, and FESEM confirmed the physicochemical characteristics of AgNPs. AgNPs that were synthesized using M. micrantha were slightly smaller than those produced using A. conyzoides. In general, the present work establishes that the synthesized AgNPs have antibacterial capability depending on their size and synthesis procedure.     

Synthesis of Metallic Silver Nanoparticles by Fluconazole Drug and Gamma Rays to Inhibit the Growth of Multidrug-Resistant Microbes

Here we tailored a methodology, including green synthesis of silver nanoparticles (AgNPs) in aqueous solution using Fluconazole (Fluc.), a broad-spectrum antifungal agent under the influence of gamma rays. AgNPs were characterized by UV–Vis., FTIR, XRD, DLS, and TEM image. Antimicrobial activities of AgNPs, Fluc., and Ag⁺ were investigated against multidrug-resistant (MDR) bacteria and unicellular fungi. From our results, AgNPs production was found to be dependent on the concentration of Ag⁺, Fluc. and gamma doses. DLS with TEM image explained the size and shape of AgNPs and were found to be spherical with diameter of 11.65 nm. FTIR analysis indicates that, the hydroxyl, nitrogen and fluoride moiety in Fluc. were responsible for the reduction and binding process. AgNPs possesses antimicrobial activity against all tested microbes more than Ag⁺. It produced high efficacy against Acinetobacter baumannii (20.0 mm ZOI). AgNPs are synergistically active towards Candida albicans (17.0 mm ZOI). Investigated action mechanisms for AgNPs activity had been discussed. Thereby, owing to its unique features as cost-effective with continued-term stabilization, it can discover potential targets in biomedical applications and infectious diseases control.     

Green synthesis of silver nanoparticles using water extract of Salvia leriifolia: Antibacterial studies and applications as catalysts in the electrochemical detection of nitrite

Here, a green method is described for the biosynthesis of Ag nanoparticles (Ag NPs) using aqueous extracts of the leaf of Salvia leriifolia as reducing and stabilizing agent. Various techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and X‐ray diffraction (XRD) were employed for the characterization of the structure and morphology of bio‐synthesized AgNPs. The results reveal that AgNPs synthesized with uniform spherical morphology and average diameters of 27 nm. The AgNPs as a green and efficient heterogeneous catalyst presented superior antibacterial activity. Direct electrochemistry studies of the synthesized AgNPs confirmed that nanoparticles retained their direct electrochemical activity. This is mainly attributed to the proper biosynthesis process, the large specific surface area and the good conductivity of the synthesized nanoparticles. Hence, the present synthesized AgNPs displayed good electrocatalytic activity to the reduction of nitrite ions. The proposed method is highly recommended as a novel platform for the development of electrochemical sensors which can further expand the applications of AgNPs. Antibacterial activity of the synthesized AgNPs was evaluated against nine microorganisms. AgNPs prevented the growth of all selected bacteria. The nanoparticles inhibited the growth of Pseudomonas aeruginosa, Klebsiella pneumonia, Staphylococcus coagulase, Acinetobacter baumannii, and Streptococcus pneumonia more than antibiotic of vancomycin, however, the ability of AgNPs against Echerishia coli and Serratia marcescens was less than the antibiotic. On the other hand AgNPs were active against Citrobacter frurdii, while the antibiotic was inactive.