Exploring the biogenic synthesis of silver nanoparticles for versatile applications—prospects and promises

Nanotechnology has rapidly advanced over the recent past. Top-down and bottom-up approaches are the two major processes used to synthesize nanoparticles. Most of chemical and physical methods of nanoparticle synthesis are time consuming and costly. Most methods require high temperatures, vacuum conditions or harsh chemicals which may have adverse effects on involved persons. In recent years, researchers have shown immense interest in the environment - friendly green synthesis of nanoparticles. Honey mediated green synthesis is a relatively novel green synthesis method that has been used in recent years to synthesize metal nanoparticles. Honey-mediated green synthesis of nanoparticles is a simple, rapid, cost-effective, biocompatible, reproducible, and safe method. In the present work, we present the sunlight - induced green synthesis of silver nanoparticles using honey from aqueous silver nitrate. We studied the effect of light intensity on the synthesis of silver nanoparticles and also analyzed the growth of the nanoparticles. The particle size is determined from plasmon resonance using Mie theory.Nanotechnology has rapidly advanced over the recent past. Top-down and bottom-up approaches are the two major processes used to synthesize nanoparticles. Most of chemical and physical methods of nanoparticle synthesis are time consuming and costly. Most methods require high temperatures, vacuum conditions or harsh chemicals which may have adverse effects on involved persons. In recent years, researchers have shown immense interest in the environment - friendly green synthesis of nanoparticles. Honey mediated green synthesis is a relatively novel green synthesis method that has been used in recent years to synthesize metal nanoparticles. Honey-mediated green synthesis of nanoparticles is a simple, rapid, cost-effective, biocompatible, reproducible, and safe method. In the present work, we present the sunlight - induced green synthesis of silver nanoparticles using honey from aqueous silver nitrate. We studied the effect of light intensity on the synthesis of silver nanoparticles and also analyzed the growt...

The unique physicochemical properties of nanoparticles due to very high surface energy lead to the alternation of miscellaneous biological functions, specifically the generation of reactive oxygen species (ROS). The nanoparticle’s size, shape, and surface chemistry are responsible for the production of ROS. The critical specific roles of ROS are concentration dependent and it is instrumental in regulating various biological functions. Nanoparticles induced toxicity along with cellular signaling leads to cell death. Redox-based bioconjugation combinational nano therapies are also a better option for the production of ROS. Development of novel immunotherapeutic agents for ROS generation, such as defining synergistic drug combinations, understanding the tumor microenvironment defects in antigen processing and presentation, and the number, type, quality, and distribution of immune cells in a tumor, and the pathways that regulate them are critical for ongoing clinical success. Green synthesis of a nanoparticle is the safest method of synthesis which avoids the production of toxic by-products. Natural components such as organic systems are ideal for solvent free toxic green synthesis. Numerous biological materials like bacteria, fungi, algae, and plant extracts are used for the green synthesis of metallic nanoparticles. In this chapter, we describe the synthesis of biogenic nanoparticles and their role in the generation of ROS to perform various activities. The biogenic synthesis of nanoparticles with the help of biomolecules, organic waste materials, and microbes leads to a reduction in toxicity. The biogenic syntheses not only reduce cost but also reduce hazardous chemicals and promote green synthesis. Moreover, we also describe the bioconjugated drugs with nanoparticles as promising anticancer nanomedicine. Such novel smart drug delivery nanomedicine induces ROS and decreases the side effects and improves the efficacy.KeywordsNanoparticlesReactive oxygen speciesToxicityBiogenic synthesis

Chapter 6 - Plant and bacteria mediated green synthesis of silver nanoparticles

Silver nanomaterials have been integrated into industrial, biomedical and agricultural application, including biosensor, anti-microbial, anti-tumor, drug delivery, waste treatment, coated fabrics and nano fertilizer. Nanoparticle possesses unusual character due to their large surface area to volume ratio and an extraordinary catalytic activity, electronic properties, optical properties and anti-microbial activity while they are constructed in atomic level. The unique and major task in the synthesis of nanoparticle is choosing of an advanced and ecofriendly method. Nevertheless, physical and chemical methods of synthesis of nanoparticles are too expensive and environmentally unsound. In this study, the green synthesis of nanoparticle’s production methods was evaluated on the basis of variable literatures. Currently, there is a better possibility of using green synthesis of silver nanoparticles, especially a plant, bacterial and fungal production of nanoparticles which is emerging as a novel ecofriendly technique. The growth rate of bacterial culture, the extract of plant secondary metabolite and mycelial surface area of fungus are the main comprehensible mechanism in green synthesis of silver nanoparticles. The silver nanoparticles, which are produced through green biosynthesis is safe and hold a better possibility to be administered for medical and agricultural usages. Over all we found that the fungal green biosynthesis of silver nanoparticles is considered more preferable and is excellently chosen in it in industrial level production.

Fabrication of silver nanoparticles by green approach is the most effective and eco-friendly technique in recent technologies. The current study aimed to generate a simple, valid, and justifiable method for biogenic synthesis of silver nanoparticles (HP-AgNPs) using aqueous extract of Hypecoum pendulum L.(HP) and to assess their invitro anticancer and genotoxic potentials on baby hamster kidney cell (BHK-21) and human blood lymphocytes using 3-(4,5-dimethylthiazol-2-yl-)-2,5-di-phenyltetrazolium bromide (MTT) and alkaline comet assay, respectively. HP-AgNP characterization was done using UV-vis spectrometry, EDX, SEM, XRD, and FTIR techniques. The crystalline nature of HP-AgNPs with a particle size of 36.3 nm was assessed using the XRD technique. The surface morphologies with a particle size of 80 nm were verified by SEM analysis. UV spectroscopy verified the existence of HP-AgNPs by yielding a sharp peak at 417 nm with an absorbance intensity of 1.54. FTIR assessment revealed the existence of different functional moieties that contribute to the HP-AgNPs stabilization and reduction. Similarly, EDX analysis revealed Ag as a principal element (49%). MTT assay showed significant cytotoxicity by Doxorubicin and HP-AgNPs with a smaller IC50 value of 104.21 ± 4.33 and 134.91 ± 6.33 μg/mL correlated to HP extract (229.84 ± 4.66 μg/mL). The outcomes of the comet assay revealed potential DNA damage in a positive trend with concentration (25-600 μg/mL). HP-AgNP-treated lymphocytes showed higher DNA damage as compared to HP extract-treated cells, but less damage as compared to a positive control, H2O2. These outcomes showed that HP-AgNPs have demonstrated promising anticancer and genotoxic action than HP extract due to their size and shape.

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Nanotechnology is an escalating field that has made its contribution to all spheres of human life. The green synthesis of nanoparticles has paved for better methodologies and approaches in the medicinal field. Nowadays silver, gold and other metallic nanoparticles are used as an efficient carrier for drug molecules for developing novel drug delivery systems. In course of synthesizing these nanoparticles various chemicals, solvents and reagents are used which harms our eco system directly or indirectly. Silver nanoparticles (Ag NPs) have been widely used as a novel therapeutic agent extending its use as antibacterial, antifungal, anti-viral and anti-inflammatory agent. Silver nanoparticles (Ag NPs) prepared by green synthesis have many advantages over conventional methods involving chemical agents associated with environmental toxicity. Green synthetic methods include polysaccharide method, irradiation method, biological method, polyoxometallates method and tollens method. Green synthesis of nanoparticles is found to be an emerging branch of nanotechnology. The use of environmentally benign materials like plant leaf extract for the synthesis of nanoparticles offers numerous benefits of eco-friendliness and compatibility for pharmaceutical and biomedical applications as they do not use toxic chemicals in the synthesis protocols. Rapid and green synthetic methods using various plant extracts have shown a great potential in silver nanoparticles (Ag NPs) synthesis. This review article describes the bio-inspired synthesis of nanoparticles that provides advancement over chemical and physical methods as it is cost effective, eco-friendly and more effective in a variety of applications.

General Background: Nanotechnology has gained significant attention for its potential applications in environmental remediation, particularly in the degradation of organic pollutants. Specific Background: Green synthesis of nanoparticles using plant extracts is a sustainable approach that reduces the need for hazardous chemicals. Knowledge Gap: However, the role of Laurus nobilis (bay laurel) in synthesizing cadmium nanoparticles (CdNPs) and their effectiveness in dye degradation remains underexplored. Aims: This study investigates the feasibility of synthesizing CdNPs using Laurus nobilis leaf extract as a natural reducing and stabilizing agent and evaluates their potential in methylene blue (MB) dye degradation. Results: The formation of CdNPs was confirmed by UV-visible spectroscopy, exhibiting a surface plasmon resonance peak at 435 nm, and SEM-EDX analysis revealed spherical nanoparticles with an average size of 61.36 nm and a cadmium composition of 87.57%. The synthesized CdNPs achieved a 60% degradation efficiency for MB dye under visible light exposure. Novelty: This work presents an eco-friendly, rapid, and simple method for synthesizing CdNPs using Laurus nobilis, highlighting the phytochemical-mediated nanoparticle stabilization. Implications: The findings demonstrate the potential of plant-based CdNPs for wastewater treatment applications, contributing to sustainable and green chemistry solutions for environmental pollution. Highlights: Green synthesis of cadmium nanoparticles using Laurus nobilis extract. Spherical CdNPs (61.36 nm) achieved 60% methylene blue degradation. Eco-friendly nanotechnology for wastewater treatment and environmental remediation. Keywords: cadmium nanoparticles, degradation, green synthesis, Laurus nobilis Leaves extract.

White biotechnology can be regarded as applied biocatalysis, with enzymes and microorganisms, aiming at industrial production of bulk and fine chemicals to food and animal feed additives. In its turn biocatalysis has many attractive features in the context of greenchemistry: mild reaction conditions (physiological pH and temperature); environmentally compatible catalysts and solvent (often water) combined with high activities; and chemo-, regio-, and stereoselectivities in multifunctional molecules. This affords processes which are shorter, generate less waste, and are, therefore, both environmentally and economically more attractive than conventional routes. This special issue includes aspects involving the use of white biotechnology (enzymes, microorganisms, and plant tissues) within the green chemistry concept, concerning the use of alternative solvents (supercritical fluids, pressurized gases, ionic liquids, and micellar systems) and energies (microwaves and ultrasound); sustainable approaches for production of fine and bulk chemicals (aromas, polymers, pharmaceuticals, and enzymes); use of renewable resources or agroindustrial residues; biocatalysts recycling; and waste minimization. This special issue contains six papers, where three are related to green synthesis of nanoparticles and one paper covers biological pretreatment for enzymatic hydrolysis and bioethanol production. Two papers regard the use of alternative reaction systems. In the first paper entitled “Green synthesis of silver nanoparticles using Pinus eldarica bark extract,” S. Iravani and B. Zolfaghari present the optimization of the biosynthesis production of silver nanoparticles through the evaluation of Pinus eldarica bark extract quantity, substrate concentration, temperature, and pH on the formation of such material. The preparation of nanostructured silver particles using P. eldarica bark extract provides an environmentally friendly option, as compared to currently available chemical and/or physical methods. The second paper, “Green and rapid synthesis of anticancerous silver nanoparticles by Saccharomyces boulardii and insight into mechanism of nanoparticle synthesis,” by A. Kaler et al. describes an ecofriendly method for the synthesis of silver nanoparticles (AgNPs) by cell free extract (CFE) of Saccharomyces boulardii. In addition to the optimization of relevant synthesis parameters as culture age, cell mass concentration, temperature, and reaction time, the paper presents particles characterization by UV-Visible spectroscopy, EDX (energy dispersive X-Rays) analysis, transmission electron microscopy, and zeta potential, as well as the elucidation of proteins/peptides role in nanoparticles formation and stability and their anticancer activity. The method therein described a method that does not require tedious downstream processing and it may be scaled up to develop a viable technology for the Ag-nanoparticle synthesis. In the third paper, “Biosynthesis, antimicrobial and cytotoxic effect of silver nanoparticles using a novel Nocardiopsis sp. MBRC-1,” P. Manivasagan et al. present another green approach for biosynthesis of nanoparticles using the culture supernatant of Nocardiopsis sp. MBRC-1 to achieve the reduction of silver ions from a silver nitrate solution. The obtained nanoparticles were characterized by UV-visible, TEM, FE-SEM, EDX, FTIR, and XRD spectroscopy. The prepared silver nanoparticles exhibited strong antimicrobial activity against bacteria and fungi. Cytotoxicity of biosynthesized AgNPs against in vitro human cervical cancer cell line (HeLa) showed a dose-response activity. In the fourth paper, “Biological pretreatment of rubberwood with Ceriporiopsis subvermispora for Enzymatic hydrolysis and bioethanol production,” F. Nazarpour et al. investigate a novel feedstock for enzymatic hydrolysis and bioethanol production using biological pretreatment: rubberwood (Hevea brasiliensis). To improve ethanol production, rubberwood was pretreated with white rot fungus Ceriporiopsis subvermispora to increase fermentation efficiency. The fungal pretreatment provides a cost-effective method for reducing the recalcitrance of rubberwood with high selectivity of lignin degradation rate and minimal cellulose loss for enzymatic hydrolysis and bioethanol production. In the fifth paper, the research of G. D. Yadav and S. Devendran entitled “Microwave assisted enzymatic kinetic resolution of (±)-1-phenyl-2-propyn-1-ol in non-aqueous media,” proposes a kinetic resolution of 1-phenyl-2-propyn-1-ol, an important chiral synthon, through esterification with acyl acetate. The authors investigate synergism between microwave irradiation and enzyme catalysis. The lipase (Novozym 435) catalyzed kinetic resolution under microwave irradiation. The maximum conversion of 48.78% was obtained in 2 h using 10 mg enzyme loading with equimolar concentration of alcohol and ester at 60°C under microwave irradiation. From the progress curve analysis, it was found that reaction followed the ping-pong bi-bi mechanism with dead end inhibition of alcohol. Beside the previous papers herein described, the preparation of chiral secondary alcohols using lipase catalyzed kinetic resolution is mild and clean as compared to chemical process. In the seventh paper entitled “Demonstration of redox potential of Metschnikowia koreensis for stereoinversion of secondary alcohols/1,2-diols,” by V. S. Meena et al. reports the Metschnikowia koreensis-catalyzed one-pot deracemization of secondary alcohols/1,2-diols and their derivatives with in vivo cofactor regeneration. This ecofriendly method afforded the product in high yield (88%) and excellent optical purity (>98% ee), minimizing the requirement of multistep reaction and expensive cofactor. Bernardo Dias Ribeiro Isabel Marrucho Luciana Goncalves Maria Alice Z. Coelho

Ocimum gratissimum L. is a perennial herbaceous plant used in the treatment of fungal and bacterial infections. Green synthesis has provided cost effective, environment friendly procedure and raising safe strategies for the synthesis of nanoparticles. This study was aimed at investigating the potential of O. gratissimum for the synthesis of selenium nanoparticles (SeNPs) and their antimicrobial activities. Phytochemical screening on aqueous extract was carried out using standard procedures. Selenium nanoparticles was biosynthesized by O. gratissimum and characterized using Visual detection, UV-Visible spectroscopy, Scanning Electron Microscope, Transmission Electron Microscope, Energy dispersive X-ray, Fourier Transform Infra-red spectroscopy and X-ray diffraction spectroscopy. Antimicrobial activity of the biosynthesized selenium nanoparticles by O. gratissimum was done using agar well diffusion method. Saponins, tannins, cardiac glycosides, terpenoids and phenols were present. The biosynthesized SeNPs had a strong plasmon resonance band at 300 nm, changes in colour from dark brown to ruby red. The SeNPs were spherical and aggregated with varying shapes and size ranged from 20 – 50 nm. Strong signal of selenium element was observed. Hydroxyl, esters, aldehyde, alkane and amine are present and responsible for the efficient stabilization and bioreduction of Selenium nanoparticle. Furthermore, biosynthesized SeNPs by O. gratissimum (OGSeNPs) exhibited higher antimicrobial activity against both Gram ositive and Gram negative bacteria. Green synthesis of nanoparticles is a promising method in the biomedical field, due to its high bioactive components.

Nanobiotechnology is an encouraging and noticeable field of nanotechnology. In recent years, the demands for the synthesis of biocompatible nanoparticles (NPs) are increasing for various applications in different areas such as health, medicine, environmental pollution, and agriculture, etc. A green synthesis of various NPs from different metal/ metal ions using different plant extracts has been extensively studied. Green synthesis of NPs is an alternative way of chemical and physical methods of NPs synthesis and is considered an eco-friendly approach in nanotechnology. Green synthesis of NPs is affected by various factors such as pH, temperature, and incubation time which must be considered to obtain an optimal result. NPs synthesized via green methodology have many potential applications in environment and climate change, biomedicals and agriculture. This mini-review provides brief information about different approaches and methods in synthesizing NPs, their characterization by various instrumental applications, and their applications in many areas that are important for humans, animals, and plants.

A critical need in the field of nanotechnology is the development of a sustainable and eco-friendly process for the synthesis of metallic nanoparticles (NPs). To accomplish this, the use of live plants becomes essential for the production of low-cost, energy-efficient, and nontoxic metallic NPs. In this study, we tried in-vivo synthesis (green synthesis) of silver and gold NPs using seeds of bean, radish, and alfalfa, which were grown hydroponically in aqueous solutions containing metal salts, 20-25 nm sized NPs were found on the inner surfaces of the plants' vascular cylinders and cortex. The amounts of NPs taken up by the intracellular systems were clearly dependent on the exposure time and concentration of the metal salts. Although these results regarding the green synthesis of NPs on the growth of plant species are somewhat interesting and effective, metal salts adversely affected the root growth of the plants. Silver ions in the growth media showed a more negative impact on root growth compared to gold ions. Therefore, even though biosynthesis of metal NPs using live plants is considered as green synthesis, we have to consider their phytotoxicity on plant growth.

Green synthesis of nanoparticles (NPs) has attracted considerable research interest in recent years because it is less expensive, more biocompatible, and environmentally friendly than common chemical or physical synthesis methods. In this work, silver (Ag) NPs were synthesized via green synthesis route involving the secondary metabolites extracted from Amaranthus viridus. The secondary metabolites were extracted using ionic liquid, 1-Butyl-3-methylimidazolium bromide ([BMIM] Br) assisted ultrasonication. They were utilized as a reducing agent to produce Ag NPs from silver nitrate (AgNO3). X-ray diffraction, field emission scanning electron microscopy, UV–visible spectroscopy, thermogravimetric analysis, and energy dispersive X-ray spectroscopy were used to determine the properties of the synthesized Ag NPs. Ag NPs were assessed for their antibacterial activity against three distinct strains of bacteria, including Aeromonas hydrophilia, Staphylococcus aureus, and Escherichia coli. According to the results, the Ag NPs displayed a face-centered cubic structure with an average particle diameter of 75 nm. In addition, the Ag NPs exhibit enhanced dispersion and thermal stability, as evidenced by their zeta potential of − 41 mV and 14% weight loss at a temperature as high as 700 °C. The synthesized Ag NPs showed outstanding antibacterial activity against A. hydrophilia, S. aureus, and E. coli, with maximum inhibitory zone diameter of 15.67 ± 1.16, 16.63 ± 0.57, and 15.34 ± 0.58 mm, respectively. This work demonstrated the remarkable ability of secondary metabolites extracted through ultrasonication to function as a reducing agent for the synthesis of Ag NPs and their application in the inactivation of potentially pathogenic bacteria.

Green synthesis method of nanoparticles has been developed for several years. Besides providing environmental-friendly process, green synthesis of nanoparticles using plant extract provides synergistic effect of the secondary metabolite in such antibiotic activity. The study with an intensification process in nanoparticles formation is also gaining great attention. This research deals with the green synthesis of silver nanoparticles using Datura metel flower extract for the antibacterial agent. The use of ultrasound-assisted method for the synthesis was investigated. Synthesis of silver nanoparticles (AgNPs) using Datura metel flower extract under ultrasound- assisted method has been conducted. Evaluation of the successful synthesis was done using UV-visible spectrophotometry, particle size analyzer, x-ray diffraction, and transmission electron microscopy. The prepared AgNPs were tested as an antibacterial against S. aureus, K. pneumoniae, S. pyogenes, and E. coli. The ultrasound-assisted synthesis of AgNPs produces particles ranging from 25-70 nm in size; meanwhile, the reflux method demonstrated the size of 50-170 nm. These particles size represents the effect on the antibacterial activity as the ultrasound-assisted synthesized Ag NPs have higher inhibition zone towards all tested bacteria. Subsequently, these data presented the applicability of Ag NPs synthesis using an ultrasound method as a potential candidate for biomedical applications. The profile of UV-Visible spectra and particle size analyses demonstrated the applicability of the ultrasound technique to produce a smaller size of the nanoparticles with higher antibacterial activity.

Chapter 6 - Biomolecule-assisted biogenic synthesis of metallic nanoparticles