Green Synthesis of Silver Nanoparticles Using Plant Extracts: Recent Advances in Mechanisms, Parameters, and Characterization Methods

These days, research in agriculture is focusing on the theme of sustainability along with protection of agriculture produce. Nanotechnology in the agriculture sector aims for the enhancement of agricultural produce and the reduction of pesticides through providing innovative agrochemical agents and their novel delivery mechanisms. The current investigation involved the green synthesis of silver nanoparticles (AgNPs) from the aqueous leaf extract of Melia azedarach by following a microwave-assisted method to control Fusarium oxysporum, the causal agent of tomato wilt. Biosynthesized Melia leaf extract (MLE)-AgNPs were characterized by UV-visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectrometry, dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and zeta potential analysis. The intensity of the peak at 434 nm in UV-vis spectra, attributed to the surface plasmon resonance of MLE-AgNPs, changes with reaction parameters. TEM exhibits spherical shaped nanoparticles with an average particle size range from 12 to 46 nm. Efficient inhibition of F. oxysporum, the causal agent of tomato wilt, was achieved after exposure to MLE-AgNPs both in vivo and in vitro. In vitro studies exhibited repressed fungal mycelial growth with 79–98% inhibition as compared to the control. Significant increases in growth parameters of tomato seedlings were observed after treatment with biosynthesized nanoparticles as compared to F. oxysporum-infected plants grown without them under greenhouse conditions. Furthermore, SEM imaging was done to reveal the prominent damage on the cell wall of hyphae and spores after MLE-AgNP treatment. Propidium iodide (PI) staining of mycelium indicated the extent of cell death, causing irretrievable damage and disintegration of cellular membranes by altering the membrane permeability. Also, 2′,7′-dichlorofluorescin diacetate (DCFH-DA) fluorescence specifies intracellular reactive oxygen species (ROS) production in F. oxysporum after treatment with MLE-AgNPs. The current investigation suggested that biosynthesized nanoparticles can revolutionize the field of plant pathology by introducing an environment-friendly approach for disease management and playing a potential part in agriculture industry. However, to date, little work has been done to integrate nanotechnology into phytopathology so, this area of research is in need of adoption and exploration for the management of plant diseases.

Cannabis sativa L. (hemp) is a plant used in the textile industry and green building material industry, as well as for the phytoremediation of soil, medical treatments, and supplementary food products. The synergistic effect of terpenes, flavonoids, and cannabinoids in hemp extracts may mediate the biogenic synthesis of metal nanoparticles. In this study, the chemical composition of aqueous leaf extracts of three varieties of Romanian hemp (two monoecious, and one dioecious) have been determined by Fourier-Transformed Infrared spectroscopy (FT-IR), high-performance liquid chromatography, and mass spectrometry (UHPLC-DAD-MS). Then, their capability to mediate the green synthesis of silver nanoparticles (AgNPs) and their pottential antibacterial applications were evaluated. The average antioxidant capacity of the extracts had 18.4 ± 3.9% inhibition determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and 78.2 ± 4.1% determined by 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS™) assays. The total polyphenolic content of the extracts was 1642 ± 32 mg gallic acid equivalent (GAE) L−1. After this, these extracts were reacted with an aqueous solution of AgNO3 resulting in AgNPs, which were characterized by UV−VIS spectroscopy, FT-IR, scanning electron microscopy (SEM-EDX), and dynamic light scattering (DLS). The results demonstrated obtaining spherical, stable AgNPs with a diameter of less than 69 nm and an absorbance peak at 435 nm. The mixture of extracts and AgNPs showed a superior antioxidant capacity of 2.3 ± 0.4% inhibition determined by the DPPH• assay, 88.5 ± 0.9% inhibition as determined by the ABTS•+ assay, and a good antibacterial activity against several human pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas fluorescens, and Staphylococcus aureus.

Green synthesis of silver nanoparticles using Melia azedarach leaf extract and their antifungal activities: In vitro and in vivo

Green synthesis is the synthesis of nanoparticles using biological systems and is greatly beneficial because of its non-toxicity and eco-friendly behaviour. This study focuses on the green synthesis of silver nanoparticles using Aloe vera gel extract and Abelmoschus esculentus extract and its characterization and antibacterial activity. The synthesized nanoparticles were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and UV- Vis Spectroscopy. The bio-reduction of aqueous Ag+ ions by these extracts were identified by their colour change. The change in colour indicates the formation of AgNPs (Silver Nanoparticles). Silver nanoparticles showed maximum absorbance at 250nm in both Aloe vera gel extract and Abelmoschus esculentus. A peak obtained at this point confirmed the presence of AgNPs. Moreover, the synthesized silver nanoparticle showed potential antibacterial activity against the selective strains of bacteria such as Escherichia coli, Staphylococcus aureus and Streptococcus pyogenes which were studied using the well-diffusion method. This study gives a scope for its potential applications in biomedical field.

A green synthesis of silver nanoparticles (AgNPs) was conducted using the stem extract of Piper chaba, which is a plant abundantly growing in South and Southeast Asia. The synthesis was carried out at different reaction conditions, i.e., reaction temperature, concentrations of the extract and silver nitrate, reaction time, and pH. The synthesized AgNPs were characterized by visual observation, ultraviolet–visible (UV-vis) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), energy dispersive x-ray (EDX), and Fourier transform infrared (FTIR) spectroscopy. The characterization results revealed that AgNPs were uniformly dispersed and exhibited a moderate size distribution. They were mostly spherical crystals with face-centered cubic structures and an average size of 19 nm. The FTIR spectroscopy and DLS analysis indicated that the phytochemicals capping the surface of AgNPs stabilize the dispersion through anionic repulsion. The synthesized AgNPs effectively catalyzed the reduction of 4-nitrophenol (4-NP) and degradation of methylene blue (MB) in the presence of sodium borohydride.

Green synthesis of silver nanoparticles from waste leaves of tea (Camellia sinensis) and their catalytic potential for degradation of azo dyes

The use of bacteria as nanofactories for the green synthesis of nanoparticles is considered a sustainable approach, owing to the stability, biocompatibility, high yields and facile synthesis of nanoparticles. The green synthesis provides the coating or capping of biomolecules on nanoparticles surface, which confer their biological activity. In this study, we report green synthesis of silver nanoparticles (AgNPs) by an environmental isolate; named as AgNPs1, which showed 100% 16S rRNA sequence similarity with Solibacillus isronensis. UV/visible analysis (UV/Vis), transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and Fourier-transform infrared spectroscopy (FTIR) were used to characterize the synthesized nanoparticles. The stable nature of nanoparticles was studied by thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS). Further, these nanoparticles were tested for biofilm inhibition against Escherichia coli and Pseudomonas aeruginosa. The AgNPs showed minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 3.12 µg/mL and 6.25 µg/mL for E. coli, and 1.56 µg/mL and 3.12 µg/mL for P. aeruginosa, respectively.

Background:Green synthesized silver nanoparticles (AgNPs) have been used in a wide range of biological applications, including their use as antimicrobial agents. The aim of this study was to evaluate the antibacterial activity of green synthesis AgNPs using nisin against Pseudomonas aeruginosa (P. aeruginosa).Materials and Methods:In order to synthesize Ag-nisin, a 1 mg/ml nisin solution was mixed with a 1-mM silver nitrate solution and incubated. The Fourier transform infrared spectroscopy (FTIR) analysis was employed to determine the presence of various biomolecules around AgNPs. The AgNPs were morphologically observed and characterized using field emission scanning electron microscopy assessment, dynamic light scattering (DLS), and zeta potential analysis. The microdilution broth method based on CLSI principles was used for the assessment of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of nisin on P. aeruginosa isolates.Results:Field emission scanning electron microscope showed spherical shaped nanoparticles. DLS revealed that the average size of nanoparticles was 37.2 nm. The zeta potential of AgNPs was − 13.3 mV. FTIR findings revealed that nitrogen atoms of nisin’s amine and amide groups are responsible for the capping and stability of the nanoparticles. The MIC and MBC showed that Ag/nisin nanoparticles had higher antimicrobial activity than nisin or AgNPs alone.Conclusion:The findings of this study show that the antibacterial activity of nisin can be increased by assembling it into the AgNP interface using a green chemical synthesis method. As a result, the technique may be used to develop an antibacterial formulation to enhance the effectiveness of nisin.

The green synthesis of silver nanoparticles (AgNPs) and their applications have attracted many researchers as the AgNPs are used effectively in targeting specific tissues and pathogenic microorganisms. The purpose of this study is to synthesize and characterize silver nanoparticles from fully expanded leaves of Eugenia roxburghii DC., as well as to test their effectiveness in inhibiting biofilm production. In this study, at 0.1 mM concentration of silver nitrate (AgNO3), stable AgNPs were synthesized and authenticated by monitoring the color change of the solution from yellow to brown, which was confirmed with spectrophotometric detection of optical density. The crystalline nature of these AgNPs was detected through an X-Ray Diffraction (XRD) pattern. AgNPs were characterized through a high-resolution transmission electron microscope (HR-TEM) to study the morphology and size of the nanoparticles (NPs). A new biological approach was undertaken through the Congo Red Agar (CRA) plate assay by using the synthesized AgNPs against biofilm production. The AgNPs effectively inhibit biofilm formation and the biofilm-producing bacterial colonies. This could be a significant achievement in contending with many dynamic pathogens.

Sumac (Rhuscoriaria L., family Anacardiaceae) is rich in bioactive components like tannins and phenolic compounds, exhibiting antioxidant properties. Green synthesis of silver nanoparticles (SAgNP) offers eco-friendly and cost-effective production methods. In this study, the effect of Sumac nano silver particles (SAgNP) on lead pharmacokinetics was assessed. Green synthesis of silver nanoparticles involved adding 25 ml of sumac extract to 200 ml of 1 mM silver nitrate solution under hot stirring. Twenty-one male albino rats were randomly divided into three groups: lead group (60 mg/kg of lead acetate orally), crude group (100 mg/kg of crude sumac extract orally), and nano group (100 mg/kg of SAgNP orally followed by lead acetate). Results demonstrated successful SAgNP formation and significant reduction (p≤0.05) in blood lead concentration after 6 hours, suggesting SAgNP's potential in lowering lead levels. SAgNP exhibited stronger efficacy than crude extract in reducing blood lead concentrations. Green synthesis of silver nanoparticles offers a safe, cost-effective, and environmentally friendly approach with promising applications in mitigating lead toxicity.

Objectives: To green synthesize silver nanoparticles by using weed plant Tridax procumbens also prepare and check antimicrobial activity of silver nanoparticles impregnated bandages against one gram positive bacteria and one-gram negative. Methods: The green synthesis of silver nanoparticles was done by chemical precipitation method using Tridax leaves extract as reducing agent. Synthesis of silver nanoparticles are characterized by UV-Visible spectroscopy, Dynamic light scattering (DLS), Zeta potential analysis, Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray diffraction analysis (XRD) to confirm size distribution, composition and crystalline nature of silver nanoparticles. Results: The peak was shown at 446nm by UV-Vis spectrophotometer and Scanning Electron Microscopy analysis reveals the spherical -shaped nanoparticles with a mean size of 99nm. Fourier transform infrared spectroscopy proved that the phytochemicals in extract were responsible for formation of the silver nanoparticles and acted as reducing and stabilizing agent. XRD study have revealed the highly crystalline nature of nanoparticles. These nanoparticles were impregnated onto bandages and they showed appreciable inhibitory activity against Escherichia coli (6mm) and Staphylococcus aureus (2mm). Conclusion: The characterization results shown the characteristic nature of the green synthesized silver nanoparticles. Thus the green synthesis was ecofriendly and nanoparticles showed promising antimicrobial activity. These antibacterial bandages can potentially be used for treating and open and infection-prone wounds.

Among the various types of nanoparticles and their strategy for synthesis, the green synthesis of silver nanoparticles has gained much attention in the biomedical, cellular imaging, cosmetics, drug delivery, food, and agrochemical industries due to their unique physicochemical and biological properties. The green synthesis strategies incorporate the use of plant extracts, living organisms, or biomolecules as bioreducing and biocapping agents, also known as bionanofactories for the synthesis of nanoparticles. The use of green chemistry is ecofriendly, biocompatible, nontoxic, and cost-effective. We shed light on the recent advances in green synthesis and physicochemical properties of green silver nanoparticles by considering the outcomes from recent studies applying SEM, TEM, AFM, UV/Vis spectrophotometry, FTIR, and XRD techniques. Furthermore, we cover the antibacterial, antifungal, and antiparasitic activities of silver nanoparticles.

Chapter 1 - Green route synthesis of silver nanoparticles (Ag-NPs) and their applications

Nanotechnology deals with the synthesis of nanoparticles with controlled size, shape and dispersity of materials at the nanometer scale and their potential use for human well bein g. This leads to focus on “Green Synthesis” of nanoparticles which seems to be an easy, efficient and eco- friendly approach. In this study, the green synthesis of silver nanoparticles was carried out using root extract of Morinda pubescens as reducing agent. It was found that aqueous silver ions can be reduced by aqueous root extr act of Morinda pubescens to generate extremely stable silver nanoparticles in water. The silver nanoparticles (AgNPs) formation was confirmed by the colour change of the mixture and further confirmed by spectral analysis. UV-Visible spectrum of the aqueous medium containing silver nanoparticles showed a peak around 416.5 nm. FT -IR analysis confirmed reduction of Ag+ ions to Ag0 ions in synthesized silver nanoparticles. Further, the produced silver nanoparticles showed bactericidal effect against Staphylococcus aureus, Escherichia coli and Aspergillus niger. From this study concluded that the root extract of Morinda pubescens reduces Ag+ to Ag0 and enhances synthesis of silver nanoparticles with antimicrobial activity.

The current study reports the green synthesis of silver nanoparticles (AgNPs) using Capparis spinosa leaf extract acting as a capping and reducing agent. The characterization of AgNPs was confirmed using ultraviolet-visible spectrophotometry (UV-Visible), fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The plant extract used reduces Ag+ into AgNPs within a few minutes as indicated by the changed color, from yellow to reddish-brown. The UV-vis spectrum of AgNPs appeared a characteristic surface plasmon resonance peak at 400-450 nm. FTIR spectroscopy confirmed the role of plant extract as a reducing and capping agent of silver ions. The spectra of FTIR revealed a broad transmission peaks from 3412 to 617 cm-1. An EDX analysis signal at 3 keV and weight 65.38% showed the peak to be in the silver region, a fact which was confirmed by the presence of elemental silver. Under TEM, the nanoparticles were seen to be spherical, with an average particle size of 13 nm. AgNPs showed antibacterial activity against S.epidermidis, S. aureus, MRSA and E. coli. The inhibition zones for S.epidermidis and S. aureus were 8 to 10 mm, while MRSA is 7 to 10 mm. The inhibition zone of E. coli was higher at 10 to 13 mm.