In vitro evaluation of antimicrobial and antibiofilm potentials of silver nanoparticles biosynthesised by Streptomyces griseorubens

This study was performed to determine the antimicrobial and antibiofilm activities of silver nanoparticles (AgNPs) biosynthesised using Streptomyces griseorubens AU2 isolated from soil. The antimicrobial activity of the AgNPs was determined by agar well diffusion, disc diffusion and broth microdilution methods. Diameters of the zone of inhibition results clearly displayed that the microbially biosynthesised AgNPs have potent antimicrobial activity against Candida albicans, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) of the nanoparticles that had been determined by broth microdilution method were found to be 20 and 50 µg/ml for C. albicans, B. subtilis and S. aureus; 10 and 20 µg/ml for E. coli and P. aeruginosa, respectively. For determining the effect of AgNPs on biofilm formation under in vitro conditions, MIC and subMICs were studied on P. aeruginosa and S. aureus biofilms by using microplate biofilm assay. Treatment of the AgNPs resulted in a decrease in the biofilm formation of S. aureus and P. aeruginosa as 26.52 and 25.50%, respectively. As a result of this study, it can be suggested that actinobacterially synthesised AgNPs have an effective potential to be used for pharmaceutical applications against multi‐resistant microorganisms.Inspec keywords: silver, nanoparticles, nanomedicine, antibacterial activity, biomedical materials, microorganismsOther keywords: antimicrobial potentials, antibiofilm potentials, silver nanoparticles, antimicrobial activity, antibiofilm activity, Streptomyces griseorubens AU2, disc diffusion, microdilution method, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, nanoparticle minimum inhibitory concentration, nanoparticle minimum lethal concentration, biofilm formation, in vitro conditions, microplate biofilm assay, pharmaceutical applications, multiresistant microorganisms, Ag     

Antibacterial potential of silver nanoparticles biosynthesised using Canarium ovatum leaves extract

Silver nanoparticles (AgNPs) have been extensively used as antibacterial agents, owing to their ease of preparation. In the present study, leaves extract of Canarium ovatum have been employed for the biosynthesis of silver nanoparticles (CO‐AgNPs). CO‐AgNPs were synthesised under very mild, eco‐friendly manner where the plant extract acted both as reducing and capping agent. These AgNPs were synthesised by taking into account several parameters, that included, time of reaction, concentration of AgNO₃, amount of extract and temperature of reaction. The optimisation studies suggested efficient synthesis of CO‐AgNPs at 25°C when 1.5 mM AgNO₃ was reduced with 1:20 ratio of plant extract for 40 min. Size determination studies done on dynamic light scattering and scanning electron microscope suggested of spherical shape nanoparticles of size 119.7 ± 7 nm and 50–80 nm, respectively. Further, characterisations were done by Fourier transform infrared and energy‐dispersive X‐ray spectroscopy to evaluate the functional groups and the purity of CO‐AgNPs. The antibacterial efficacy of CO‐AgNPs was determined against the bacterial strain Pseudomonas aeruginosa. As evident from disc diffusion method studies, CO‐AgNPs remarkably inhibited the growth of the tested microorganism. This study suggested that C. ovatum extract efficiently synthesises CO‐AgNPs with significant antibacterial properties and can be good candidates for therapeutics.Inspec keywords: antibacterial activity, nanoparticles, silver, nanofabrication, particle size, light scattering, scanning electron microscopy, Fourier transform infrared spectra, X‐ray chemical analysis, microorganisms, biomedical materials, nanomedicineOther keywords: antibacterial potential, silver nanoparticles, biosynthesis, Canarium ovatum leave extract, plant extract, reducing agent, capping agent, antibacterial agents, reaction time, reaction temperature, dynamic light scattering, scanning electron microscopy, spherical shape nanoparticles, Fourier transform infrared spectroscopy, functional groups, bacterial strain Pseudomonas aeruginosa, disc diffusion method, microorganism, energy‐dispersive X‐ray spectroscopy, temperature 25 degC, time 40 min, Ag     

Green synthesis of metal nanoparticles loaded ultrasonic‐assisted Spirulina platensis using algal extract and their antimicrobial activity

The synthesis of metal nanoparticles (NPs) loaded on the ultrasonic‐assisted Spirulina platensis (MNPs/UASP) was investigated using the green synthesis method. The S. platensis algal extract was taken as a reducing agent. The formations of metal NPs were characterised using UV–visible spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The antimicrobial activity of different metal NPs demonstrated various inhibitory activities against one gram‐positive bacteria (Staphylocicus aureus), four gram‐negative bacteria (Klebsiella pneumonia, Proteus vulgaris, Pseudomonas aeruginosa and Escherichia coli) and one fungus (Aspergillus niger). Both CrNPs/UASP and ZnNPs/UASP show good antimicrobial activity when compared with other MNPs/UASP against microorganisms. This MNPs/UASP is effective in preventing and treating the microbial infection and water pollution in the environment.Inspec keywords: antibacterial activity, nanoparticles, nanomedicine, ultraviolet spectra, visible spectra, microorganisms, Fourier transform infrared spectraOther keywords: metal nanoparticles loaded ultrasonic‐assisted Spirulina platensis, algal extract, antimicrobial activity, green synthesis method, UV–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, gram‐positive bacteria, Staphylocicus aureus, Klebsiella pneumonia, Proteus vulgaris, Pseudomonas aeruginosa, Escherichia coli, Aspergillus niger, fungus, microorganisms, microbial infection, water pollution     

Assessment of cytotoxicity and immune compatibility of phytochemicals‐mediated biosynthesised silver nanoparticles using Cynara scolymus

The study was focused on the phytochemicals‐mediated biosynthesis of silver nanoparticles using leaf extracts and infusions from Cynara scolymus. To identify the antioxidant activity and total phenolic content, the 1,1‐diphenyl‐1‐picrylhydrazyl and Folin–Ciocalteau methods were applied, respectively. The formation and stability of the reduced silver ions were monitored by UV–vis spectrophotometer. The particle sizes of the silver nanoparticles were characterised using the dynamic light scattering technique and scanning electron microscope. The phase composition of the obtained silver nanoparticles was characterised by X‐ray diffraction. The silver nanoparticles suspension, artichoke infusion, and silver ions were separately tested towards potential cytotoxicity and pro‐inflammatory effect using mouse fibroblasts and human monocytes cell line, respectively. The total phenolic content and antioxidant activity of ethanol extract and infusion were found significantly higher as compared to aqueous extract and infusion. The UV–visible spectrophotometric analysis revealed the presence of the characteristic absorption band of the Ag nanoparticles. Moreover, it was found that with the increasing volume of plant extract, the average size of particles was increased. Biocompatibility results evidently showed that silver nanoparticles do not induce monocyte activation, however in order to avoid their cytotoxicity suspension at a concentration <2 ppm should be applied.Inspec keywords: pharmaceuticals, health and safety, renewable materials, toxicology, organic compounds, antibacterial activity, X‐ray diffraction, nanomedicine, nanoparticles, nanofabrication, suspensions, ultraviolet spectra, visible spectra, scanning electron microscopy, silver, particle sizeOther keywords: phytochemicals‐mediated biosynthesis, antioxidant activity, total phenolic content, dynamic light scattering technique, silver nanoparticles suspension, scanning electron microscopy, Cynara scolymus, 1,1 diphenyl‐1‐picrylhydrazyl method, cytotoxicity, immune compatibility, leaf extracts, UV‐vis spectrophotometry, particle size, Folin‐Ciocalteau methods, phase composition, X‐ray diffraction, artichoke infusion, pro‐inflammatory effect, mouse fibroblasts, human monocytes cell line, Ag     

Evaluation of antimicrobial activity of synthesised silver nanoparticles using Thymus kotschyanus aqueous extract

Development of a green chemistry process for the synthesis of silver nanoparticles (AgNPs) has become a focus of interest. Characteristics of AgNPs were determined using techniques, such as ultraviolet–visible spectroscopy (UV–vis), Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy and X‐ray diffraction (XRD). The synthesised AgNPs using Thymus kotschyanus had the most growth inhibition against gram‐positive bacteria such as Staphylococcus aureus and Bacillus subtilise, while the growth inhibition of AgNPs at 1000–500 µg/ml occurred against Klebsiella pneumonia and at 1000–250 µg/ml of AgNPs was observed against E. coli. The UV–vis absorption spectra confirmed the formation of the AgNPs with the characteristic peak at 415 nm and SEM micrograph acknowledged spherical particles in a nanosize range. FTIR measured the possible biomolecules that are responsible for stabilisation of AgNPs. XRD analysis exhibited the crystalline nature of AgNPs and showed face‐centred cubic structure. The synthesised AgNPs revealed significant antibacterial activity against gram‐positive bacteria.Inspec keywords: visible spectra, microorganisms, ultraviolet spectra, biomedical materials, nanofabrication, nanoparticles, X‐ray diffraction, scanning electron microscopy, molecular biophysics, X‐ray chemical analysis, nanomedicine, silver, antibacterial activity, Fourier transform infrared spectraOther keywords: green chemistry process, ultraviolet–visible spectroscopy, gram‐positive bacteria, silver nanoparticles, Thymus kotschyanus aqueous extract, UV–vis spectroscopy, Fourier transform infrared spectroscopy, FTIR analysis, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, SEM micrograph, X‐ray diffraction, XRD, Staphylococcus aureus, Bacillus subtilise, Klebsiella pneumonia, E. coli, UV–vis absorption spectra, face‐centred cubic structure, antibacterial activity, antimicrobial activity, wavelength 415.0 nm, Ag     

Green biosynthesis,characterisation and antimicrobial activities of silver nanoparticles using fruit extract of Solanum viarum

Green synthesis of nanoparticles is considered an efficient method when compared with chemical and physical methods because of its bulk production, eco‐friendliness and low cost norms. The present study reports, for the first time, green synthesis of silver nanoparticles (AgNPs) at room temperature using Solanum viarum fruit extract. The visual appearance of brownish colour with an absorption band at 450 nm, as detected by ultraviolet‐visible spectrophotometer analysis, confirmed the formation of AgNPs. X‐ray diffraction confirmed the AgNPs to be crystalline with a face‐centred lattice. The transmission electron microscopy‐energy dispersive X‐ray spectroscopy image showed the AgNPs are poly‐dispersed and are mostly spherical and oval in shape with particle size ranging from 2 to 40 nm. Furthermore, Fourier transform‐infrared spectra of the synthesised AgNPs confirmed the presence of phytoconstituents as a capping agent. The antimicrobial activity study showed that the AgNPs exhibited high microbial activity against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus susp. aureus, Aspergillus niger, and Candida albicans. The highest antimicrobial activity of AgNPs synthesised by S. viarum fruit extract was observed in P. aeruginosa, S. aureus susp. aureus and C. albicans with zone of inhibition, 26.67 mm.Inspec keywords: nanomedicine, antibacterial activity, X‐ray chemical analysis, nanoparticles, transmission electron microscopy, particle size, infrared spectra, microorganisms, X‐ray diffraction, Fourier transform spectra, ultraviolet spectra, scanning electron microscopy, visible spectra, nanofabricationOther keywords: green biosynthesis, antimicrobial activities, silver nanoparticles, green synthesis, physical methods, study reports, solanum viarum fruit, ultraviolet‐visible spectrophotometer analysis, high microbial activity, highest antimicrobial activity, s. viarum fruit, transmission electron microscopy, energy dispersive X‐ray spectroscopy image     

Green synthesis of silver nanoparticles using Nervalia zeylanica leaf extract and evaluation of their antioxidant,catalytic, and antimicrobial potentials

ABSTRACT

Here we report a simple, one-pot, inexpensive, and eco-friendly method for the synthesis of silver nanoparticles. The leaf extract of a medicinal plant Nervalia zeylanica was used as reducing and stabilizing agent for the synthesis of nanoparticles by microwave-assisted strategy. The nanoparticles show characteristic surface plasmon peak at 468?nm in UV–vis absorption spectrum. The involvement of phytochemicals in the reduction and stabilization of nanoparticles was confirmed by FTIR analysis. Using X-ray diffraction analysis, the crystalline nature of the nanoparticles was demonstrated. Transmission electron microscopic analysis shows that the nanoparticles were in spherical shape with average particle size of 34.2?nm. The antioxidant studies were performed by the 1,1-diphenyl-2-picryl hydrazyl method. The nanoparticles show excellent scavenging activities than the leaf extract. The IC₅₀ values of silver nanoparticles and the leaf extract, respectively, were 15.20 and 92.83?µg?mL^?1. The catalytic activities of synthesized nanoparticles were examined by using them in the reduction of organic dyes. The nanoparticles show excellent catalytic activities and follow pseudo-first-order kinetics. The antimicrobial activities of nanoparticles were analyzed by an agar well diffusion method against six microbial strains and found that the nanoparticles were highly toxic against all the tested microbial strains.     

In vitro germination and biochemical profiling of Brassica napus in response to biosynthesised zinc nanoparticles

With the progression of nanotechnology, the use of nanoparticles (NPs) in consumer products has increased dramatically and green synthesis is one of the cheapest and eco‐friendly methods to obtain non‐hazardous NPs. In the current research zinc (Zn) NPs synthesis was carried out by using the fresh and healthy leaves of Mentha arvensis L. followed by characterisation through ultraviolet (UV)–visible spectroscopy, X‐ray diffraction (XRD) and scanning electron microscopy (SEM). UV–visible spectroscopy confirmed the green synthesis of ZnNPs, while XRD confirmed the size of NPs, which was 30–70 nm. SEM shows that the shape of ZnNPs was irregular. The effects of green synthesised NPs on two different varieties of Brassica napus were evaluated. Exposure to ZnNPs (5, 15, and 25 mg/l⁻¹) caused a significant increase in root and shoot length of B. napus. The application of NPs significantly improved plant germination and triggered the production of secondary metabolite and antioxidant enzymes. ZnNPs showed a significant increase in chlorophyll, superoxide dismutase, total flavonoid content (TFC) and antioxidant enzymes while total phenolic content was decreased when TFC increased. Thus, it has been concluded from the current study that ZnNPs may possibly trigger the production of antioxidant enzymes and various biochemical compounds.Inspec keywords: zinc, nanoparticles, nanofabrication, ultraviolet spectra, visible spectra, X‐ray diffraction, scanning electron microscopy, particle size, enzymes, molecular biophysics, biochemistry, nanobiotechnology, botanyOther keywords: biochemical profiling, Brassica napus, biosynthesised zinc nanoparticles, nanotechnology, Mentha arvensis L, ultraviolet‐visible spectroscopy, X‐ray diffraction, Zn, biochemical compounds, total phenolic content, total flavonoid content, superoxide dismutase, chlorophyll, antioxidant enzymes, secondary metabolite, plant germination, green synthesis, SEM, scanning electron microscopy, XRD     

Synthesis and characterization of silver nanoparticles and their antimicrobial efficacy

An efficient protocol for synthesis of silver nanoparticles (AgNPs) using the combination of aqueous extract of Tinospora cordifolia leaves and 5 mM silver nitrate (AgNO₃) solution was developed. This study revealed that bioactive compounds present in the extract function as stabilizing and capping agent for AgNPs. Scanning electron microscope and transmission electron microscope studies confirm the structure and surface morphology of the AgNPs. The size of synthesized AgNPs was in the range of 30–50 nm having spherical morphology. The crystalline nature of NPs was defined by the X-ray diffraction pattern. The AgNPs were found to be toxic against pathogenic bacteria such as Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), and Staphylococcus aureus (ATCC 29213) and against plant pathogenic fungi Fusarium oxysporum (MTCC 8608) and Sclerotinia sclerotiorum (MTCC 8785). The use of AgNPs as antibacterial and antifungal agent is advantageous over other methods for control of pathogenic microorganisms, and it can be of great importance in developing novel drugs for curing many lethal diseases.     

Biosynthesis,characterisation and antimicrobial activity of silver and gold nanoparticles by Dolichos biflorus Linn seed extract

The bioreduction method employed for the synthesis of colloidal AgNPs and AuNPs is reported here. Methanolic and aqueous extracts of Dolichos biflorus Linn seed was used as the bio-reducing agent. The structural and morphological aspects of the synthesised metal nanoparticles were investigated using X-ray diffraction (XRD), energy-dispersive spectroscopy (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD, revealed crystalline nature of the synthesised particles, UV–vis spectrophotometric analysis showed characteristic absorption peak for both AgNPs and AuNPs. EDX analysis confirmed the presence of elemental silver and gold particles and the average size and morphology were determined by SEM and TEM. The synthesised AgNPs exhibited good antibacterial potential whereas AuNPs showed poor activity against human pathogenic, gram-positive bacteria such as Staphylococcus aureus, Bacillus subtilis and gram-negative bacteria, such as Escherichia coli, Pseudomonas aeruginosa.     

Preparation of linoleic acid-capped silver nanoparticles and their antimicrobial effect

Silver nanoparticles have been prepared through the chemical reduction of silver ions by ethanol using linoleic acid as a stabilising agent. This colloidal solution shows an absorption band in the visible range with an absorption peak at 421 nm. The peaks in the X-ray diffraction (XRD) pattern matches well with the standard values of the face-centred-cubic form of metallic silver. Transmission Electron Microscope (TEM) micrograph shows a nearly uniform distribution of the particles with an average size of 8 nm. This linoleic acid-capped silver nanoparticles show antimicrobial activity against Escherichia coli and Staphylococcus aureus.     

Antibacterial and anticancer activity of biosynthesised CuO nanoparticles

The present investigation aims for the synthesis of copper oxide nanoparticles (CuO NPs) using Nilgirianthus ciliatus plant extract. The obtained CuO NPs were characterised by X‐ray diffraction, Fourier transform infrared spectrum, ultraviolet–visible spectroscopy, photoluminescence, scanning electron microscopy and transmission electron microscopy analysis. Significant bacterial activity was manifested by CuO nanoparticles against both Gram‐positive (Staphylococcus aureus and Staphylococcus mutans) and Gram‐negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. The synthesised CuO NPs have good cytotoxicity against both human breast cancer cell line (MCF‐7) and lung cancer cell line (A549) with minimum cytotoxic effect on normal L929 (fibroblast) cell lines.Inspec keywords: microorganisms, ultraviolet spectra, nanomedicine, transmission electron microscopy, visible spectra, cellular biophysics, antibacterial activity, nanoparticles, X‐ray diffraction, lung, copper compounds, cancer, toxicology, biomedical materials, scanning electron microscopy, photoluminescence, Fourier transform infrared spectraOther keywords: antibacterial activity, anticancer activity, biosynthesised CuO nanoparticles, copper oxide nanoparticles, Nilgirianthus ciliatus plant, X‐ray diffraction, infrared spectrum, ultraviolet–visible spectroscopy, transmission electron microscopy analysis, bacterial activity, Gram‐negative bacteria, synthesised CuO NPs, human breast cancer cell line, Staphylococcus aureus, Staphylococcus mutans, CuO     

Cytotoxicity,leishmanicidal, and antioxidant activity of biosynthesised zinc sulphide nanoparticles using Phoenix dactylifera

The synthesis of zinc sulphide nanoparticles (ZnS NPs) using a green approach was explored. The resulting nanoparticles (NPs) were characterised by UV–vis spectroscopy, scanning and transmission electron microscopy, X‐ray diffraction and Fourier transform infrared spectroscopy. The leishmanicidal, cytotoxic and antioxidant activity of the resulting synthesised ZnS NPs (<70 nm) were evaluated against Leishmania major (L. major) promastigotes and amastigotes by MTT assay and using a macrophage model. The ZnS NPs were able to counteract the effects of oxidative metabolites as demonstrated by the oxidant activity. The IC₅₀ value of butylated hydroxyanisole was 26.04 µg/ml as compared with the IC₅₀ for ZnS NPs (90.95 µg/ml). The NPs displayed no cytotoxicity for the murine macrophaghes as the selectivity index (SI) fell into the safety range (SI ≥ 10). These nanomaterials exhibited good antileishmanial activity against the L. major stages that were comparable to that of Glucantime, the drug of choice. The IC₅₀ values of ZnS NPs and Glucantime against amastigotes were 11.59 ± 2.51 and 4.95 ± 2.51 μg/ml, respectively. The IC₅₀ values for ZnS NPs and Glucantime versus promastigote were 29.81 ± 3.15 and 14.75 ± 4.05 μg/ml, respectively. Further investigation is essential to explore the biological effects of ZnS NPs on animal and/or clinical models.Inspec keywords: nanoparticles, nanofabrication, microorganisms, antibacterial activity, ultraviolet spectra, visible spectra, nanobiotechnology, X‐ray diffraction, Fourier transform infrared spectra, zinc compoundsOther keywords: cytotoxicity, leishmanicidal activity, antioxidant activity, biosynthesised zinc sulphide nanoparticles, Phoenix dactylifera, green approach, UV–vis spectroscopy, scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, Leishmania major promastigotes, Leishmania major amastigotes, MTT assay, macrophage model, oxidative metabolites, butylated hydroxyanisole, murine macrophaghes, selectivity index, glucantime, ZnS     

Biosynthesised silver nanoparticles using aqueous leaf extract of Tagetes patula L. and evaluation of their antifungal activity against phytopathogenic fungi

In the recent decades, nanotechnology is gaining tremendous impetus due to its capability of modulating metals into their nanosize, which drastically changes the chemical, physical, biological and optical properties of metals. In this study, silver nanoparticles (AgNPs) synthesis using aqueous leaf extracts of Tagetes patula L. which act as reducing agent as well as capping agent is reported. Synthesis of AgNPs was observed at different parameters like temperature, concentration of silver nitrate, leaf extract concentration and time of reduction. The AgNPs were characterized using UV‐vis spectroscopy, scanning electron microscope with energy dispersive spectroscopy, transmission electron microscopy with selected area electron diffraction, X‐ray diffraction, Fourier transform infrared and dynamic light scattering analysis. These analyses revealed the size of nanoparticles ranging from 15 to 30 nm as well revealed their spherical shape and cubic and hexagonal lattice structure. The lower zeta potential (−14.2mV) and the FTIR spectra indicate that the synthesized AgNPs are remarkably stable for a long period due to the capped biomolecules on the surface of nanoparticles. Furthermore, these AgNPs were found to be highly toxic against phytopathogenic fungi Colletotrichum chlorophyti by both in vitro and in vivo and might be a safer alternative to chemical fungicides.Inspec keywords: silver, nanoparticles, nanofabrication, nanobiotechnology, ultraviolet spectra, visible spectra, scanning electron microscopy, X‐ray chemical analysis, electron diffraction, X‐ray diffraction, Fourier transform infrared spectra, crystal structure, electrokinetic effects, antibacterial activityOther keywords: biosynthesised silver nanoparticles, aqueous leaf extract, Tagetes patula L, antifungal activity, phytopathogenic fungi, nanotechnology, UV–vis spectroscopy, scanning electron microscope, energy dispersive spectroscopy, transmission electron microscopy, selected area electron diffraction, X‐ray diffraction, Fourier transform infrared spectra, dynamic light scattering analysis, hexagonal lattice structure, zeta potential, phytopathogenic fungi Colletotrichum chlorophyti, cubic lattice structure, size 15 nm to 30 nm, Ag     

Green synthesis and characterisation of silver nanoparticles and their effects on antimicrobial efficacy and biochemical profiling in Citrus reticulata

The synthesis of nanoparticles by utilising plant extract has revolutionised the field of nanotechnology. In the present study, AgNPs were synthesised by utilising the leaves of Moringa oleifera as reducing and stabilising agent. UV‐visible spectroscopy showed characteristic surface plasmon band in the range of 413–420 nm. Scanning electron microscopy (SEM) elucidated rectangular segments fused together. X‐ray diffraction (XRD) analysis confirmed the crystalline nature of AgNPs and presence of metallic silver ions was confirmed by energy dispersive X‐ray (EDX). The different concentrations (10, 20, 30 and 40 ppm) of AgNPs were exogenously applied on Citrus reticulata to record the disease incidence at different day intervals. The disease intensity was progressively increased in all the applied treatments with the passage of time. The 30 ppm concentration of AgNPs was found to be most suitable concentration for creating the resistance against brown spot disease. Moreover, the effects of AgNPs were also assessed for biochemical profiling in C. reticulata. The enhanced production of endogenous enzymes and non‐enzymatic components was observed in response to 30 ppm concentration of AgNPs. The present work highlighted that green synthesised AgNPs can be as used as biological control of citrus diseases and the enhanced production of secondary metabolites antioxidants.Inspec keywords: nanoparticles, silver, nanofabrication, nanomedicine, biomedical materials, biochemistry, enzymes, molecular biophysics, plant diseases, ultraviolet spectra, visible spectra, scanning electron microscopy, surface plasmon resonance, X‐ray diffraction, X‐ray chemical analysisOther keywords: green synthesis, silver nanoparticles, antimicrobial efficacy, biochemical profiling, Citrus reticulata, plant extract, nanotechnology, medical sciences, environment friendly AgNPs, biomedical fields, leaves, Moringa oleifera, reducing agent, stabilising agent, ultraviolet‐visible spectroscopy, characteristic surface plasmon band, scanning electron microscopy, rectangular shape, X‐ray diffraction analysis, crystalline nature, energy dispersive X‐ray spectroscopy, disease incidence, disease intensity, applied treatments, Alternaria brown spot disease, total phenolic content, dry weight, total flavonoid content, T4 treatment, superoxide dismutase activity, fresh weight, maximum peroxidase production, DPPH radical scavenging assay, biological control, citrus disease, secondary metabolites antioxidants     

An optical tweezer-based study of antimicrobial activity of silver nanoparticles

Understanding and characterizing microbial activity reduction in the presence of antimicrobial agents can help in the design and manufacture of antimicrobial drugs. We demonstrate the use of an optical tweezer setup in recording the changes in bacterial activity with time, induced by the presence of foreign bodies in a bacterial suspension. This is achieved by monitoring the fluctuations of an optically trapped polystyrene bead immersed in it. Examining the changes in the fluctuation pattern of the bead with time provides an accurate characterization of the reduction in the microbial activity. Here, we report on the effect of addition of silver nanoparticles on bacterial cultures of Pseudomonas aeroginosa, Escherichia coli and Bacillus subtilis. We observe a decrease in the bacterial activity with time for the investigated bacterial samples. This method in our opinion, enables one to track changes in bacterial activity levels as a function of time of contact with the antibacterial agent with greater efficacy than traditional cell counting methods.     

In vitro mutagenic and anti‐mutagenic properties of green synthesised silver nanoparticles

This study is aimed at determining the mutagenic and anti‐mutagenic properties of silver nanoparticles (AgNPs) biosynthesised from Streptomyces griseorubens AU2. To the authors’ knowledge, this is the first study about the investigation of these properties for biogenic AgNPs bacterially synthesised. The mutagenic and anti‐mutagenic potencies were determined by the Ames Salmonella /microsome mutagenicity test using Salmonella typhimurium TA98 and TA100 strains. After determining the cytotoxic dose of green synthesised AgNPs against S. typhimurium TA98 and TA100 strains, subcytotoxic doses (250, 100 and 50 µg/plate) were used in the assays. Biogenic AgNPs at the tested concentrations exhibited no mutagenic effects in the mutagenicity test conducted with the test strains. Moderate anti‐mutagenic effects were observed at high test concentrations. The concentration of 250 µg/plate showed the strongest anti‐mutagenic activity on S. typhimurium TA98. The results did not indicate any mutagenic effect against either of the strains used for screening the mutagenicity of the biogenic AgNPs as they were found to be genotoxically safe. It can be concluded that biogenic AgNPs showed great anti‐mutagenic attributes, standing as a significant factor with respect to medical, pharmaceutical and cosmetic industries.Inspec keywords: biomedical materials, microorganisms, nanomedicine, nanoparticles, silver, toxicologyOther keywords: in vitro mutagenic properties, in vitro antimutagenic properties, green synthesised silver nanoparticles, Streptomyces griseorubens AU2, biogenic silver nanoparticle biosynthesis, microsome mutagenicity test, Salmonella typhimurium TA98 strains, Salmonella typhimurium TA100 strains, subcytotoxic doses, medical industries, pharmaceutical industries, cosmetic industries, Ag     

In-vivo and in-vitro biocompatibility evaluations of silver nanoparticles with antimicrobial activity

In this study, the biocompatibility and antimicrobial activity of silver nanoparticles (Ag NPs) were evaluated in vitro and in vivo. The cytotoxicity of Ag NPs (average diameter: 2-5 nm) against CHO-K1 cells was determined via WST-8 assay, and their genotoxicity was examined via Salmonella typhimurium reverse mutation assay (Ames test). The acute toxicity and intracutaneous reactivity of Ag NPs were evaluated using animal models of mice and rabbits, respectively. The antibacterial effects of Ag NPs on the Gram (-) bacterial strains of Escherichia coli ATCC 8739 and Pseudomonas aeruginosa ATCC 9027 and on the Gram (+) bacterial strains of Staphylococcus aureus ATCC 6538p and Bacillus subtilius ATCC 6633 were determined by measuring the minimum inhibitory concentrations. The Ag NPs were highly cytotoxic to the L-929 cells at over 2 ppm but were non-cytotoxic at lower than 1 ppm. Moreover, the Ag NPs at 1 ppm or lower did not show genotoxicity, acute toxicity and intracutaneous reactivity. It was also found that the Ag NPs exerted effective antimicrobial activities on both the Gram (-) and (+) bacterial strains within the range from 0.06 to 0.98 ppm for 50% MIC.     

Synthesis and characterisation of silver nanoparticles using leaf extract of Artemisia afra and their in vitro antimicrobial and antioxidant activities

In this study, the conversion of silver ions into ∼30.74 nm sized silver nanoparticles (AgNPs) was achieved in 30 min at a reaction temperature of 80–90°C in aqueous leaf extract of Artemisia afra. The synthesised AgNPs showed surface plasmon resonance in the range of 423–438 nm. Spherical and face‐centred cubic nanoparticles were confirmed by transmission electron microscope (TEM) and X‐ray diffraction (XRD) analysis, respectively. Fourier transform infra‐red (FTIR) results indicated that the obtained nanoparticles were stabilised and capped through the carbonyl and carboxylate ion groups possibly from flavonoids, terpenoids, phenolics and esters content of the extracts. In addition, the AgNPs were assessed for their biological potentials against some microbes and, also, their free radical scavenging ability was established. The AgNPs exhibited interesting antimicrobial and antioxidant properties better than the aqueous extract of A. afra. Inspec keywords: silver, transmission electron microscopy, ultraviolet spectra, visible spectra, surface plasmon resonance, antibacterial activity, X‐ray diffraction, microorganisms, nanoparticles, nanofabrication, Fourier transform infrared spectraOther keywords: silver nanoparticles, reaction temperature, surface plasmon resonance, face‐centred cubic nanoparticles, antioxidant properties, silver ion conversion, aqueous leaf extract, carboxylate ion group, antimicrobial properties, Artemisia afra, spherical nanoparticles, TEM, XRD, FTIR spectra, Ag, temperature 80 degC to 90 degC, time 30.0 min, free radical scavenging, esters, phenolics, terpenoids, flavonoids, carbonyl ion group