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     

Characterisation and antifungal activity of silver nanoparticles biologically synthesised by Amaranthus retroflexus leaf extract

ABSTRACT

Following the emergence of resistant fungal pathogens, silver nanoparticles (AgNPs) biosynthesized by plants have been recognized as promising tools to combat parasitic fungi. This study evaluated the potency of Amaranthus retroflexus in producing AgNPs, followed by testing their antifungal effects. The AgNPs exhibited a maximum absorption at 430 nm through ultraviolet-visible spectroscopy, while the X-ray diffraction indicated that they were crystal in nature. Fourier transform infrared spectroscopy confirmed the conversion of Ag⁺ ions to AgNPs due to the reduction by capping material of plant extract. The transmission electron microscope analysis further revealed that the AgNPs were spherical ranging from 10 nm to 32 nm in size. The AgNPs at the concentrations of 50, 100, 200, and 400 μg/mL were applied to the growth of plant, mushroom, and human pathogenic fungi. The 50% minimum inhibitory concentrations (MIC₅₀) against Macrophomina phaseolina, Alternaria alternata and Fusarium oxysporum were observed to be 159.80 ± 14.49, 337.09 ± 19.72, and 328.05 ± 13.29 μg/mL, respectively. However, no considerable inhibition was observed regarding Trichoderma harzianum or Geotrichum candidum. These findings may suggest A. retroflexus as a green solution for biosynthesizing AgNPs with potent antifungal activities against plant pathogenic fungi.     

Effect of green synthesised silver nanoparticles on morphogenic and biochemical variations in callus cultures of kinnow mandarin (Citrus reticulata L.)

Citrus reticulata is economically important tree fruit crop in Pakistan, fortified with various nutrients and minerals including Vitamin C and secondary metabolites. Nanotechnology is a twenty‐first century science and deals with production of minute particles termed as nanoparticles. In present study, silver nanoparticles (AgNPs) were synthesised through green method by utilising leaves of Olea europea as main reducing and capping agent. The synthesised AgNPs were characterised through UV visible spectroscopy, SEM, and energy dispersive X‐ray. Furthermore, different concentrations of AgNPs (10, 20, 30 ppm) in combination with Thidiazuron (0.5, 1.0 mg/l) were added onto MS medium to study development and secondary metabolites production in callus culture of C. reticulata. Callus induction percentage (96%) was more in 20 ppm AgNPs and 1 mg/l TDZ concentration. Moreover, high total phenolic, flavonoid contents, and antioxidant activity was observed in 20 ppm AgNPs combined with 0.5 and 1 mg/l TDZ. Enzymatic components (SOD, POD and CAT) were increased in MS medium augmented with 30 ppm AgNPs and TDZ. The total protein content (TPC) was significant in callus cultures treated with TDZ only. This study provides the first evidence of green synthesised AgNPs on callus culture developments and further quantification of biochemical profiling in C. reticula. Inspec keywords: nanoparticles, silver, ultraviolet spectra, scanning electron microscopy, antibacterial activity, agricultural products, nanotechnology, biotechnology, agricultural engineering, nanofabrication, genetic engineering, cropsOther keywords: green synthesised silver nanoparticles, morphogenic variations, biochemical variations, kinnow mandarin, citrus reticulata L, nutrients, minerals, green method, UV visible spectroscopy, energy dispersive X‐ray, MS medium, secondary metabolites production, callus induction percentage, TDZ, flavonoid contents, callus culture developments, capping agent, phenolic contents, tree fruit crop     

Antibacterial effects of biosynthesized silver nanoparticles using aqueous leaf extract of Rosmarinus officinalis L.

In this study, we demonstrate a green approach for the synthesis of silver nanoparticles (AgNPs) using aqueous leaf extract of Rosmarinus officinalis under ambient conditions. The uniqueness of this method lies in its rapid synthesis within 15 min. The synthesized AgNPs were characterized using UV–vis, FTIR, XRD, FE-SEM coupled with EDX, TEM and AFM. The synthesized particles were found to be 14.20–42.42 nm with face centered cubic geometry. The functional group of flavonoids and terpenoids was largely identified by FTIR which was found to be responsible for the synthesis and stabilization of the AgNPs. Further, antibacterial efficacy of the biologically synthesized AgNPs was investigated by the standard method against Pseudomonas aeruginosa and Staphylococcus aureus. The results showed that the aqueous leaf extract mediated synthesized AgNPs is an excellent antibacterial agent against clinical pathogens.     

Green synthesis of silver nanoparticles using Glaucium corniculatum (L.) Curtis extract and evaluation of its antibacterial activity

The metal nanoparticles, due to interesting features such as electrical, optical, chemical and magnetic properties, have been investigated repeatedly. Also, the mentioned nanoparticles have specific uses in terms of their antibacterial activity. The biosynthesis method is more appropriate than the chemical method for producing the nanoparticles because it does not need any special facilities; it is also economically affordable. In the current study, the silver nanoparticles (AgNPs) were obtained by using a very simple and low‐cost method via Glaucium corniculatum (L.) Curtis plant extract. The characteristics of the AgNPs were investigated using techniques including: X‐ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy. The SEM and TEM images showed that the nanoparticles had a spherical shape, and the mean diameter of them was 53.7 and 45 nm, respectively. The results of the disc diffusion test used for measuring the anti‐bacterial activity of the synthesised nanoparticles indicated that the formed nanoparticles possessed a suitable anti‐bacterial activity.Inspec keywords: silver, nanoparticles, antibacterial activity, nanomedicine, nanofabrication, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectraOther keywords: green synthesis, silver nanoparticles, Glaucium corniculatum Curtis extract, antibacterial activity, metal nanoparticles, biosynthesis method, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, SEM, TEM, spherical shape, disc diffusion test, Ag     

Antibacterial and dye degradation potential of zero‐valent silver nanoparticles synthesised using the leaf extract of Spondias dulcis

The present study reports a simple and low cost synthesis of zero‐valent silver nanoparticles (ZVSNPs) from silver nitrate using the leaf extract of Spondias dulcis. The ZVSNPs showed a unique peak at 420 nm in UV–vis spectrum. The SEM image portrayed cuboidal shaped particles. The EDX spectrum designated the elemental silver peak at 3 keV. In XRD, a sharp peak at 32.47° denoted the existence of (1 0 1) lattice plane and the average crystallite size was calculated as 48.61 nm. The lattice parameter was determined as 0.39 nm. The FTIR spectra of the leaf extract and ZVSNPs showed shifts in the specific functional group bands which ascertained the involvement of phytoconstituents in the formation and capping of nanoparticles. The average hydrodynamic size was measured as 59.66 nm by DLS method. A low PDI, 0.187 witnessed the monodispersity. A negative zeta potential value of −15.7 mV indicated the negative surface charges of the nanoparticles. The bactericidal action of ZVSNPs was demonstrated against two pathogens S.typhimurium and E.coli during which a dosage dependent zone of inhibition results was observed. Additionally, the catalytic potential of ZVSNPs was examined for the degradation of methylene blue dye in which an accelerated degradation of the dye was observed.Inspec keywords: antibacterial activity, crystallites, electrokinetic effects, scanning electron microscopy, nanoparticles, particle size, ultraviolet spectra, X‐ray chemical analysis, microorganisms, light scattering, nanofabrication, materials preparation, X‐ray diffraction, visible spectra, silver, dyes, Fourier transform infrared spectraOther keywords: wavelength 420.0 nm, Ag, voltage ‐15.7 mV, size 59.66 nm, size 0.39 nm, size 48.61 nm, electron volt energy 3.0 keV, Fourier transform infrared spectra, methylene blue dye, bactericidal action, dynamic light scattering, lattice parameter, Escherichia coli, Salmonella typhimurium, Spondias dulcis, negative zeta potential, polydispersity index, crystallite size, leaf extract, X‐ray diffraction, energy dispersive X‐ray spectrum, cuboidal‐shaped particles, scanning electron microscopy image, ultraviolet–visible spectrum, silver nitrate, zero‐valent silver nanoparticles     

Preparation and bactericidal properties of silver nanoparticles in aqueous tea leaf extract

Ag nanoparticles 10 to 60 nm in size have been prepared by reducing silver ions in aqueous tea leaf extract. The properties of the nanoparticles have been studied by ultraviolet spectroscopy, atomic absorption, surface-enhanced Raman spectroscopy, and atomic force microscopy. According to the Raman spectroscopy results, the equilibrium of the redox reaction is displaced to an antioxidant form of flavonoids. The presence of silver nanoparticles enhances the antioxidant and bactericidal properties of tea.     

Characterisation of gold nanoparticles synthesised by leaf and seed extract of Syzygium cumini L.

Here, Syzygium cumini leaf extract (LE) and seed extract (SE) were explored for the synthesis of gold nanoparticles (GNP). LE and SE as well as their polar (water) fractions showed potential for GNP synthesis. Comparative synthesis kinetics and morphological characterisation studies revealed the synthesis of smaller sized GNP by LE than SE. Only polar (water) fractions showed potential for GNP synthesis, which are smaller in size compared to their respective extracts. SE contained more polyphenols and biochemical constituents than LE and therefore, showed higher synthesis rate and bigger sized GNP. Atomic force microscope and scanning electron microscope analysis indicated that both extracts and their fractions catalysed the synthesis of spherical GNP. The average size of GNP synthesised by LE, leaf water fraction (LWF), SE and seed water fraction (SWF) were 24, 23, 35 and 32?nm, respectively. Fourier transform infrared analysis identified the biomolecules involved in the synthesis and stability of GNP. This study documented the potential of S. cumini for the synthesis of GNP in addition to silver nanoparticles (SNP). However, nature and types of polyphenols involved in GNP synthesis seem to be different from that involved in SNP synthesis. This might be the possible reason for smaller sized GNP that SNP.     

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     

Broad‐spectrum inhibitory effect of green synthesised silver nanoparticles from Withania somnifera (L.) on microbial growth,biofilm and respiration: a putative mechanistic approach

Multi‐drug resistance in pathogenic bacteria has created immense clinical problem globally. To address these, there is need to develop new therapeutic strategies to combat bacterial infections. Silver nanoparticles (AgNPs) might prove to be next generation nano‐antibiotics. However, improved efficacy and broad‐spectrum activity is still needed to be evaluated and understood. The authors have synthesised AgNPs from Withania somnifera (WS) by green process and characterised. The effect of WS‐AgNPs on growth kinetics, biofilm inhibition as well as eradication of preformed biofilms on both gram‐positive and gram‐negative pathogenic bacteria was evaluated. The authors have demonstrated the inhibitory effect on bacterial respiration and disruption of membrane permeability and integrity. It was found that WS‐AgNPs inhibited growth of pathogenic bacteria even at 16 µg/ml. At sub‐minimum inhibitory concentration concentration, there was approximately 50% inhibition in biofilm formation which was further validated by light and electron microscopy. WS‐AgNPs also eradicated the performed biofilms by varying levels at elevated concentration. The bacterial respiration was also significantly inhibited. Interaction of WS‐AgNPs with test pathogen caused the disruption of cell membrane leading to leakage of cellular content. The production of intracellular reactive oxygen species reveals that WS‐AgNPs exerted oxidative stress inside bacterial cell causing microbial growth inhibition and disrupting cellular functions.Inspec keywords: silver, nanoparticles, nanofabrication, nanomedicine, antibacterial activity, biomedical materials, cellular biophysics, microorganisms, biomembranes, electron microscopy, oxidation, biochemistry, permeabilityOther keywords: broad‐spectrum inhibitory effect, green synthesised silver nanoparticles, Withania somnifera (L.), microbial growth, putative mechanistic approach, multidrug resistance, therapeutic strategies, bacterial infections, next generation nanoantibiotics, broad‐spectrum activity, WS‐AgNPs, growth kinetics, biofilm inhibition, gram‐positive pathogenic bacteria, gram‐negative pathogenic bacteria, bacterial respiration, membrane permeability, membrane integrity, subminimum inhibitory concentration concentration, biofilm formation, light pathogenic bacteria, electron microscopy, cell membrane, cellular content leakage, intracellular reactive oxygen species, oxidative stress, microbial growth inhibition, Ag     

A novel approach for the biosynthesis of silver oxide nanoparticles using aqueous leaf extract of Callistemon lanceolatus (Myrtaceae) and their therapeutic potential

This study describes a novel biological route for the biosynthesis of silver oxide nanoparticles utilising the aqueous extract of Callistemon lanceolatus D.C. leaves. Formation of silver oxide nanoparticles was confirmed by UV–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscope–energy dispersive X-ray spectroscopy and X-ray diffraction spectroscopy analysis. The biologically synthesised silver oxide nanoparticles were found to be 3–30 nm in size with spherical and hexagonal shape by high-resolution transmission electron microscope analysis. Furthermore, the biogenic silver oxide nanoparticles demonstrated significant (p?in vitro antioxidant methods. These particles also exhibited significant (p?相似文献   

Antimicrobial potential and in vitro cytotoxicity study of polyvinyl pyrollidone‐stabilised silver nanoparticles synthesised from Lysinibacillus boronitolerans

The main emphasis herein is on the eco‐friendly synthesis and assessment of the antimicrobial potential of silver nanoparticles (AgNPs) and a cytotoxicity study. Silver nanoparticles were synthesised by an extracellular method using bacterial supernatant. Biosynthesised silver nanoparticles were characterised by UV‐vis spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, dynamic light scattering, and zeta potential analysis. The synthesised silver nanoparticles exhibited a characteristic peak at 420 nm. TEM analysis depicted the spherical shape and approximately 20 nm size of nanoparticles. Silver nanoparticles carry a charge of −33.75 mV, which confirms their stability. Biogenic polyvinyl pyrrolidone‐coated AgNPs exhibited significant antimicrobial effects against all opportunistic pathogens (Gram‐positive and Gram‐negative bacteria, and fungi). Silver nanoparticles equally affect the growth of both Gram‐positive and Gram‐negative bacteria, with a maximum inhibition zone observed at 22 mm and a minimum at 13 mm against Pseudomonas aeruginosa and Fusarium graminearum, respectively. The minimum inhibitory concentration (MIC) of AgNPs against P. aeruginosa and Staphylococcus aureus was recorded at between 15 and 20 μg/ml. Synthesised nanoparticles exhibited a significant synergistic effect in combination with conventional antibiotics. Cytotoxicity estimates using C2C12 skeletal muscle cell line via 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) test and lactate dehydrogenase assay were directly related to the concentration of AgNPs and length of exposure. On the basis of the MTT test, the IC50 of AgNPs for the C2C12 cell line was approximately 5.45 μg/ml concentration after 4 h exposure.     

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     

Self-assembly of silver nanoparticles into dendritic flowers from aqueous solution

Similar to folding of proteins into three-dimensional (3D) structure, self-assembly of metallic nanoparticles (NPs) into dendritic or other supramolecular structures is of greater interest, yet less understood. We observed spontaneous, template-free organisation of silver NPs into 3D, dendritic, elegant, flower-like structures from an aqueous solution containing AgNO₃ and L-cysteine (Cys). The resultant NPs and dendritic structures were characterised using UV–Vis spectroscopy and scanning and transmission electron microscopy. The process initiated most likely by diffusion-limited aggregation in the liquid phase, which were further grown into elegant, dendritic flowers probably by evaporation of residual wetting layer of larger NPs. Electrostatic attraction between –COO^? and –NH₃ ⁺ groups of L-Cys on the surface of silver NPs may also have a role in their growth.     

Biosynthesis of silver nanoparticles using aqueous extract of silky hairs of corn and investigation of its antibacterial and anticandidal synergistic activity and antioxidant potential

This paper investigated the green synthesis of silver nanoparticles (AgNPs) using aqueous extract of silky hairs of corn (Zea mays L.) which is a waste material of the crop, as both a reducing and stabilising/capping agent. The AgNPs were characterised by UV‐visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X‐ray analysis (EDX), thermogravimetric analysis (TGA), X‐ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT‐IR). The average size of AgNPs was found to be 249.12 nm. The AgNPs displayed strong antibacterial activity against five different foodborne pathogenic bacteria with diameter of inhibition zones ranged between (9.23 − 12.81 mm). It also exhibited potent synergistic antibacterial activity together with standard antibiotics, kanamycin (10.6 − 13.65 mm inhibition zones) and rifampicin (10.02 − 12.86 mm inhibition zones) and anticandidal activity with amphotericin b (10.57 − 13.63 mm inhibition zones). The AgNPs exhibited strong antioxidant activity in terms of nitric oxide scavenging (IC₅₀ 91.56 µg/mL), ABTS (2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid) radical scavenging (IC₅₀ 115.75 µg/mL), DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) radical scavenging (IC₅₀ 385.87 µg/mL), and reducing power (IC_0.5 23.14 µg/mL). This study demonstrated the synthesis of spherical AgNPs with strong antibacterial, anticandidal and antioxidant properties that could potentially be utilised in the biomedical, cosmetic, food and pharmaceutical industries.Inspec keywords: silver, nanoparticles, nanomedicine, antibacterial activity, biomedical materials, nanofabrication, botany, ultraviolet spectra, visible spectra, scanning electron microscopy, X‐ray chemical analysis, Fourier transform infrared spectra, crystallitesOther keywords: biomedical industry, cosmetic industry, food industry, pharmaceutical industry, Ag, crystallite size, 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging, 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid) radical scavenging, nitric oxide scavenging, amphotericin b, anticandidal activity, rifampicin, kanamycin, standard antibiotics, inhibition zones, foodborne pathogenic bacteria, Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, energy‐dispersive X‐ray analysis, scanning electron microscopy, ultraviolet‐visible spectroscopy, Zea mays L, antioxidant potential, anticandidal synergistic activity, antibacterial synergistic activity, corn, silky hair aqueous extract, silver nanoparticles biosynthesis     

Seed germination and biochemical profile of Citrus reticulata (Kinnow) exposed to green synthesised silver nanoparticles

The biosynthesis of silver nanoparticles (AgNPs) is substantial for its applications in different fields. The Moringa oleifera leaves were used as reducing and stabilising agent for the biosynthesis of AgNPs. The synthesised AgNPs were characterised through UV–visible spectroscopy, zeta analyser, scanning electron microscopy (SEM) and energy dispersive Xray (EDX). In this study, effects of the synthesised AgNPs were also evaluated on nucellus tissues germination frequency and biochemical parameters of plant tissues. Nucellus tissues of Citrus reticulata were inoculated on MS medium supplemented with 10, 20, 30 and 40 µg/ml suspension of the synthesised AgNPs. Green synthesised AgNPs enhanced the in vitro germination because of low toxicity and nonfriendly issues. Significant results were obtained for germination parameters i.e. root and shoot length and seedling vigour index in response to 30 µg/ml suspension of green synthesised AgNPs. The 30 µ/ml suspension of AgNPs also enhanced antioxidant activity (41%) and SOD activity (0.36 nM/min/mg FW) while total phenolic content (4.7 µg/mg FW) and total flavonoid content (1.1 µg/mg FW) was significantly high when MS medium was fortified with 40 µg/ml suspension of the synthesised AgNPs. The content of total protein was significant (558 µg/BSA Eq/mg FW) in control plantlets as compared to the other treatments.Inspec keywords: antibacterial activity, ultraviolet spectra, X‐ray chemical analysis, proteins, microorganisms, biochemistry, nanofabrication, silver, nanotechnology, visible spectra, surface plasmon resonance, nanoparticles, suspensions, nanomedicine, scanning electron microscopy, electrokinetic effectsOther keywords: green synthesised silver nanoparticles, superoxide dismutase activity, biochemical profile, UV–visible spectroscopy, Citrus reticulata, green synthesised suspension, EDX detector, zeta potential, scanning electron microscopy, SEM, energy dispersive X‐ray, EDX, total phenolic content, total flavonoid content, size 423.0 nm to 425.0 nm, size 8.0 nm to 28.0 nm     

Removal of toxic contaminants from water by sustainable green synthesised non‐toxic silver nanoparticles

The study describes the synthesis of silver nanoparticles using 21 different plant extracts having medicinal properties. Molecular ultraviolet‐visible spectroscopy shows that the λ _max of nanoparticles synthesised by different plant extracts varied and ranged between 400 and 468 nm. The ultraviolet results revealed that although synthesis of nanoparticles occurred by all plant extracts successfully, their size varies, this was further confirmed by differential light scattering. The synthesised nanoparticles were investigated for their antimicrobial properties. The most promising silver nanoparticles Ocimum sanctum and Artemisia annua assisted were further characterised using transmission electron microscopy and energy dispersive X‐ray spectroscopy (EDX). EDX data confirms that synthesised nanoparticles are highly pure. Further these two plant assisted nanoparticles were studied for chemocatalytic and adsorptive properties. The silver nanoparticles from Ocimum sanctum can catalyse the reduction of 4‐nitrophenol (63%) within 20 min in the presence of NaBH₄, whereas Artemisia annua assisted silver nanoparticles did not show significant chemocatalytic activity. Both the promising nanoparticles can efficiently adsorb textile dyes from aqueous solutions. These synthesised nanoparticles were also exploited to remove microbial and other contaminants from Yamuna River water. The nanoparticles show excellent antimicrobial properties and can be reused repeatedly.Inspec keywords: antibacterial activity, nanofabrication, silver, dyes, light scattering, visible spectra, microorganisms, X‐ray diffraction, transmission electron microscopy, X‐ray chemical analysis, catalysis, nanoparticles, ultraviolet spectra, adsorption, reduction (chemical)Other keywords: sustainable green synthesised nontoxic silver nanoparticles, silver nitrate, molecular ultraviolet–visible spectroscopy, plant assisted nanoparticles, plant extracts, Ocimum sanctum, Artemisia annua, E. coli, C. albicans, plasmon absorbance, differential light scattering, energy dispersive X‐ray spectroscopy, 4‐nitrophenol, chemocatalytic activity, Yamuna River water, antimicrobial properties, time 20.0 min, time 5.0 min to 240.0 hour, size 1.0 nm to 5.0 nm, size 5.0 nm to 20.0 nm, wavelength 400.0 nm to 468.0 nm, NaBH₄ , Ag     

Optical and morphological studies of L-histidine functionalised silver nanoparticles synthesised by two different methods

Silver nanoparticles (NPs) functionalised with L-histidine is synthesised by a chemical reduction approach using two different methods of stirring – using a magnetic stirrer and an ultrasonicator. The former method exhibits a strong narrow absorption peak at 396 nm and the latter a blue-shifted weak broad plasmon band for the bare silver NPs. When the capping agent is incorporated, a single broad peak at low intensity evolves for the first method of stirring whereas two distinct peaks are noticed for the second. The Transmission Electron Microscope (TEM) results confirm the spherical shape of the silver NPs in the first case. In the second case, both spherical and elliptical particles are obtained. Zeta potential measurements further confirm the stability of the histidine-capped silver NPs in comparison with the pure silver NPs. A study of the variation of the plasmon peak with pH indicates that a basic medium favours the growth of the histidine-capped silver NPs. A surface-enhanced Raman scattering investigation confirms the adsorption of the capping molecule through the nitrogen of the imidazole ring with the carboxylate group pointing outwards. L-histidine-capped silver NPs can find application in biosensors and biomedicine, particularly when prepared by the magnetic stirrer method due to its greater stability.     

Nigella arvensis leaf extract mediated green synthesis of silver nanoparticles: Their characteristic properties and biological efficacy

In the present study, the potential of aqueous leaf extract of Nigella arevensis for biosynthesis of silver nanoparticles (AgNPs) was evaluated. The formation of AgNPs was confirmed by color changes and UV–visible spectroscopy, which showed absorbance maxima peak at 416?nm. The transmission electron microscope (TEM) image showed the AgNPs to be anisotropic and mostly spherical with sizes in the range of 5–100?nm. Fourier transform infrared (FTIR) analysis indicated that the flavonoids, alkaloids and phenolic groups present in leaf extract were involved in the reduction and capping of phytogenic AgNPs. These nanoparticles showed the cytotoxic effects against H1229 and MCF-7 cancer cell lines with an IC₅₀ value of 10?μg/mL. AgNPs showed insignificant antioxidant properties compared to the crude extract, and it was effective against clinical isolated bacterial strains. Furthermore, the bioderived AgNPs displayed significant catalytic activity against methylene blue. These results confirmed the advantages and applications of these phytogenic AgNPs using the green method in various fields.     

Layer-by-layer deposition of green synthesised silver nanoparticles on polyester air filters and its antimicrobial activity

Silver nanoparticles stabilised with anionic polymeric polyelectrolytes were successfully synthesised by high-energy UV reduction. Three types of polyelectrolytes were used including poly(methacrylic acid) (PMA), poly(acrylic acid) (PAA) and poly(4-styrenesulphonic acid-co-maleic acid) (CoPSS). The formation of the prepared solutions exhibited surface plasmon resonance at the wavelength of 475, 730 and 408 nm by using PMA, PAA and CoPSS as the stabilising agents. UV–visible spectrophotometer, transmission electron microscope (TEM) and zeta potential analyser were employed to characterise the formation of the prepared solutions. The silver nanoparticles stabilised with anionic polyelectrolytes were immobilised on polyester air filters using a layer-by-layer technique. This is the sequential dipping of polyester air filters in a dilute solution of cationic poly(diallyldimethylammonium chloride) and anionic polymeric polyelectrolytes capped silver. The surface topography of the polyester air filters were measured by field emission scanning electron microscope. Results showed that silver nanoparticles had the highest surface coverage on the polyester air filters probably because it is a good bonding candidate and insures strong film growth. The multilayers polyester air filters coated silver nanoparticles were tested against the gram positive pathogen Staphylococcus aureus. The deposition of silver nanoparticles onto the polyester air filters resulted in 92.18%, 84.32% and 71.19% of bacteria removal using PMA, PAA and CoPSS as the stabilising agent.