Eco-friendly green synthesis of silver nanoparticles using salmalia malabarica: synthesis, characterization, antimicrobial, and catalytic activity studies

Potentials of roots, stems, leaves, flowers, fruits, and seeds extract for the synthesis of silver nanoparticles

Silver nanoparticles (AgNPs) have gained significant attention in various applications due to their unique properties that differ from bulk or macro-sized counterparts. In the advancement of nanotechnology, a reliable, non-toxic, and eco-friendly green synthesis has widely been developed as an alternative method for the production of AgNPs, overcoming limitations associated with the traditional physical and chemical methods. Green synthesis of AgNPs involves the utilization of biological sources including plant extracts with silver salt as the precursor. The potential of phytochemicals in plant extracts serves as a reducing/capping and stabilizing agent to aid in the bio-reduction of Ag+ ions into a stable nanoform, Ag0. This review provides insights into the potentials of various plant parts like root, stem, leaf, flower, fruit, and seed extracts that have been extensively reported for the synthesis of AgNPs.

Genotoxicity of Copper, Silver and Green Synthetic Gold Nanoparticles in Fish (Ctenopharyngodon idella)

Grass carp (Ctenopharyngodon idella) was exposed to nanoparticles of different concentrations, i.e., copper oxide nanoparticles (CuO-NPs), silver nanoparticles (Ag-NPs), and green synthetic gold nanoparticles (Au-NPs).The administered doses of the three concentration groups were 20mg L-1, 30 mg L-1, and 40mg L-1 each for a period of 14 and 28 days, respectively. The DNA damage in the erythrocytes of grass carp was detected through a comet assay technique. The values of total comet score (TCS) were noted for the exposed concentrations with a significant increasing trend (p < 0.05) and ordered as CuO-NPs > Ag-NPs > Au-NPs. The highest TCS value of the exposed erythrocytes was recorded for CuO-NPs at 40 mg L-1 after 14 days of exposition period. Comparatively, TCS values of erythrocytes exposed to green synthetic Au-NPs at all the concentrations and exposed time were less as compared to the Ag-NPs and CuO-NPs. The study confirmed the adverse effects of nanoparticles on the genetic material of fish cells.

Biological Synthesis of Silver Nanoparticles by Amaryllis vittata (L.) Herit: From Antimicrobial to Biomedical Applications

The current study sought to synthesize silver nanoparticles (AgNPs) from Amaryllis vittata (L.) leaf and bulb extracts in order to determine their biological significance and use the toxic plants for human health benefits. The formation of silver nanoparticles was detected by a change in color from whitish to brown for bulb-AgNPs and from light green to dark brown for leaf-AgNPs. For the optimization of silver nanoparticles, various experimental physicochemical parameters such as pH, temperature, and salt were determined. UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray dispersion spectroscopy, scanning electron microscopy, and energy dispersion spectroscopy analysis were used to characterize nanoparticles. Despite the fact that flavonoids in plant extracts were implicated in the reduction and capping procedure, the prepared nanoparticles demonstrated maximum absorbency between 400 and 500 nm. SEM analysis confirmed the preparation of monodispersed spherical crystalline particles with fcc structure. The bioinspired nanoparticles were found to show effective insecticidal activity against Tribolium castaneum and phytotoxic activity against Lemna aequincotialis. In comparison to plant extracts alone, the tested fabricated nanoparticles showed significant potential to scavenge free radicals and relieve pain. Antibacterial testing against human pathogenic strains, i.e., Escherichia coli and Pseudomonas aureginosa, and antifungal testing against Aspergillus niger revealed the significant potential for microbe resistance using AgNPs. As a result of the findings, the tested silver nanoparticles demonstrated promising potential for developing new and effective pharmacological and agricultural medications. Furthermore, the effects of biogenic AgNPs on an in vitro culture of Solanum tuberosum L. plants were investigated, and the findings indicated that bulb-AgNPs and leaf-AgNPs produced biomass and induced antioxidants via their active constituents. As a result, bulb-AgNPs and leaf-AgNPs may be recommended for use in Solanum tuberosum L. tissue culture for biomass fabrication and metabolic induction.

A Critical Review of the Antimicrobial and Antibiofilm Activities of Green-Synthesized Plant-Based Metallic Nanoparticles

Metallic nanoparticles (MNPs) produced by green synthesis using plant extracts have attracted huge interest in the scientific community due to their excellent antibacterial, antifungal and antibiofilm activities. To evaluate these pharmacological properties, several methods or protocols have been successfully developed and implemented. Although these protocols were mostly inspired by the guidelines from national and international regulatory bodies, they suffer from a glaring absence of standardization of the experimental conditions. This situation leads to a lack of reproducibility and comparability of data from different study settings. To minimize these problems, guidelines for the antimicrobial and antibiofilm evaluation of MNPs should be developed by specialists in the field. Being aware of the immensity of the workload and the efforts required to achieve this, we set out to undertake a meticulous literature review of different experimental protocols and laboratory conditions used for the antimicrobial and antibiofilm evaluation of MNPs that could be used as a basis for future guidelines. This review also brings together all the discrepancies resulting from the different experimental designs and emphasizes their impact on the biological activities as well as their interpretation. Finally, the paper proposes a general overview that requires extensive experimental investigations to set the stage for the future development of effective antimicrobial MNPs using green synthesis.

Multifarious global flora fabricated phytosynthesis of silver nanoparticles: a green nanoweapon for antiviral approach including SARS-CoV-2

The progressive research into the nanoscale level upgrades the higher end modernized evolution with every field of science, engineering, and technology. Silver nanoparticles and their broader range of application from nanoelectronics to nano-drug delivery systems drive the futuristic direction of nanoengineering and technology in contemporary days. In this review, the green synthesis of silver nanoparticles is the cornerstone of interest over physical and chemical methods owing to its remarkable biocompatibility and idiosyncratic property engineering. The abundant primary and secondary plant metabolites collectively as multifarious phytochemicals which are more peculiar in the composition from root hair to aerial apex through various interspecies and intraspecies, capable of reduction, and capping with the synthesis of silver nanoparticles. Furthermore, the process by which intracellular, extracellular biological macromolecules of the microbiota reduce with the synthesis of silver nanoparticles from the precursor molecule is also discussed. Viruses are one of the predominant infectious agents that gets faster resistance to the antiviral therapies of traditional generations of medicine. We discuss the various stages of virus targeting of cells and viral target through drugs. Antiviral potential of silver nanoparticles against different classes and families of the past and their considerable candidate for up-to-the-minute need of complete addressing of the fulminant and opportunistic global pandemic of this millennium SARS-CoV2, illustrated through recent silver-based formulations under development and approval for countering the pandemic situation.

Graphical abstract

Reduction of 4-nitrophenol using green-fabricated metal nanoparticles

Noble metal (silver (Ag), gold (Au), platinum (Pt), and palladium (Pd)) nanoparticles have gained increasing attention due to their importance in several research fields such as environmental and medical research. This review focuses on the basic perceptions of the green synthesis of metal nanoparticles and their supported-catalyst-based reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The mechanisms for the formation of these nanoparticles and the catalytic reduction of 4-NP are discussed. Furthermore, the parameters that need to be considered in the catalytic efficiency calculations and perspectives for future studies are also discussed.

Noble metal (silver (Ag), gold (Au), platinum (Pt), and palladium (Pd)) nanoparticles have gained increasing attention due to their importance in several research fields such as environmental and medical research.

Sunlight-driven rapid and facile synthesis of Silver nanoparticles using Allium ampeloprasum extract with enhanced antioxidant and antifungal activity

Green nanotechnology has acquired immense demand due to its cost-effective, eco-friendly and benevolent approach for the synthesis of nanoparticles. Among the biological methods, plants aid as a significant green resource for synthesizing nanoparticles that are safe and non-toxic for human use. In the present investigation, Silver nanoparticles (AgNPs) were synthesized using bulbs extract of Allium ampeloprasum under the influence of sunlight irradiation and characterized using different techniques. Distinct in-vitro assays were performed to test the antioxidant and anticandida potential of the synthesized AgNPs. Results suggested the efficient and rapid sunlight-driven synthesis of AgNPs using A. ampeloprasum extract. UV–Vis spectrum showed absorption peak at 446 nm which confirmed the formation of AgNPs. FTIR analysis suggested the presence of functional groups associated with flavonoids and sulfur compounds in A. ampeloprasum extract. The synthesized AgNPs showed Face Centred Cubic (FCC) structure with an average size of 35 nm. Spherical, quasi spherical, triangular and ellipsoidal morphology of the NPs were observed from the TEM micrograph. The synthesized AgNPs showed pronounced free radical scavenging potential for DPPH, ABTS∙+ and H₂O₂ radicals. The anticandida potency of the synthesized AgNPs was observed as follows: C. albicans ≥ C. tropicalis ≥ C. glabrata ≥ C. parapsilosis ≥ C. krusei. Results showed that sunlight driven nanoparticle synthesis of AgNPs is rapid, facile and exhibit enhanced antioxidant and antifungal activity.

Green synthesis of silver nanoparticles using plant extracts and their antimicrobial activities: a review of recent literature

Synthesis of metal nanoparticles using plant extracts is one of the most simple, convenient, economical, and environmentally friendly methods that mitigate the involvement of toxic chemicals. Hence, in recent years, several eco-friendly processes for the rapid synthesis of silver nanoparticles have been reported using aqueous extracts of plant parts such as the leaf, bark, roots, etc. This review summarizes and elaborates the new findings in this research domain of the green synthesis of silver nanoparticles (AgNPs) using different plant extracts and their potential applications as antimicrobial agents covering the literature since 2015. While highlighting the recently used different plants for the synthesis of highly efficient antimicrobial green AgNPs, we aim to provide a systematic in-depth discussion on the possible influence of the phytochemicals and their concentrations in the plants extracts, extraction solvent, and extraction temperature, as well as reaction temperature, pH, reaction time, and concentration of precursor on the size, shape and stability of the produced AgNPs. Exhaustive details of the plausible mechanism of the interaction of AgNPs with the cell wall of microbes, leading to cell death, and high antimicrobial activities have also been elaborated. The shape and size-dependent antimicrobial activities of the biogenic AgNPs and the enhanced antimicrobial activities by synergetic interaction of AgNPs with known commercial antibiotic drugs have also been comprehensively detailed.

Biogenic Silver and Zero-Valent Iron Nanoparticles by Feijoa: Biosynthesis, Characterization, Cytotoxic, Antibacterial and Antioxidant Activities

Background: and Purpose:

Green nanotechnology is an interesting method for the synthesis of functional nanoparticles. Because of their wide application, they have set up great attention in recent years.

Objective:

The present research examines the green synthesis of Ag and zero-valent iron nanoparticles (AgNPs, ZVINPs) by Feijoa sellowiana fruit extract. In this synthesis, no stabilizers or surfactants were applied.

Methods:

Eco-friendly synthesis of Iron and biogenic synthesis of Ag nanoparticles were accomplished by controlling critical parameters such as concentration, incubation period and temperature. Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier-Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction analysis (XRD), Dynamic Light Scattering (DLS) and UV-Vis were applied to characterize NPs. The cytotoxicity of NPs was investigated in two cell lines, MCF-7 (breast cancer) and AGS (human gastric carcinoma). A high-performance liquid chromatography (HPLC) analysis was also performed for characterization of phenolic acids in the extract.

Results:

Both NPs displayed powerful anticancer activities against two tumor cell lines with little effect on BEAS-2B normal cells. Synthesized AgNPs and ZVINPs inhibited the growth of all selected bacteria. Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella pneumonia, Staphylococcus aureus, Enterococcus faecalis, Acinetobacter baumannii and Escherichia coli have been studied in two stages. We initially examined the ATCCs followed by clinical strain isolation. Based on the results from resistant strains, we showed that nanoparticles were superior to conventional antibiotics. DPPH (diphenyl-1-picrylhydrazyl) free radical scavenging assay and iron chelating activity were used for the determination of antioxidant properties. Results showed a high antioxidant activity of scavenging free radicals for ZVINPs and powerful iron-chelating activity for AgNPs. Based on the HPLC data, catechin was the major phenolic compound in the extract.

Conclusion:

Our synthesized nanoparticles displayed potent cytotoxic, antibacterial and antioxidant activities.

Design and development of porous terracotta disc: An eco-friendly novel control agent for mosquito larvae

In the present work, we synthesized silver nanoparticles supported by rice husk by hydrothermal treatment, as-synthesized silver nanoparticles rice husk (AgNPs-RH) bio-composite mixed with potter clay thoroughly, molded, dried into a disc-shaped before firing and applying as a point of use larvicidal agent. As designed, porous terracotta disc (PTD) infused with AgNPs-RH-biocomposite were characterized by UV spectrophotometer, Fourier-transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction analysis and energy-dispersive X-ray spectroscopy. The amount of silver ions released from the PTD was also found to be within the prescribed limit of 0.1 ppm-level. Later we dropped the PTD and tested its larvicidal activity against the IV^th instar larva stage of Aedes, Anopheles and Culex species. We found 100% larvicidal mortality in 24 h of exposure to the designed PTD and the amount of silver released from the porous disc was found to be 0.0343 ppm. Further from the histopathological studies of dead larvae revealed that the silver ions from the PTD have substantially damaged the exoskeleton of larvae.

Simple and cleaner system of silver nanoparticle synthesis using kenaf seed and revealing its anticancer and antimicrobial potential

The clean and eco-friendly synthesis of silver nanoparticles (AgNPs) has provided promising characteristics with impressive biomedical related potential. Here, we have employed a green process for the synthesis of AgNPs using kenaf seed (KS) extract as a bilateral mediator for reducing and capping of Ag⁺ ions under hydrothermal condition. The synthesis pathways, such as varying amounts of KS, Ag ion concentration and autoclaving time were optimized. The manifestation of a strong absorption peak from 420-430 nm in UV-vis spectroscopy indicated the successful synthesis of KS@AgNPs. Fourier transform infrared spectroscopy confirmed the presence of hydroxyl and carbonyl functionalities involved in the reduction and stabilization of Ag⁺ ions. Furthermore, transmission electron microscopy revealed that the KS@AgNPs are spherical in shape having a size around 7-11 nm, whereas high-quality crystals were evidenced by x-ray diffraction analysis. Moreover, inductively coupled plasma-optical emission spectrometry revealed that 19.6 μg l^-1 of Ag⁺ ions were released from the KS@AgNPs. In cell line studies, KS@AgNPs at a higher dose were shown to be non-toxic to the healthy (NIH3T3) cells, while strong anti-proliferative response was found in the case of lung cancer (A549) cells. Furthermore, a significant zone of inhibition was observed for both Gram-positive and Gram-negative microorganisms, and a combination of KS@AgNPs with ampicillin revealed a notable synergistic anti-pathogenic effect. Overall, our study proved the potentiality of KS as an efficient bio-resource for the synthesis of AgNPs and also its original feature as an anti-cancer and antimicrobial agent.

Catalytic and antibacterial properties of gold nanoparticles synthesized by a green approach for bioremediation applications

In this work, we are proposing the green synthesis of gold nanoparticles (AuNPs) using aqueous extracts of A. triphylla and evaluating their antibacterial and catalytic properties. Characterization was performed by UV-Vis and FT-IR spectroscopies, X-ray diffraction, and transmission electron microscopy (TEM). Antibacterial activity of AuNPs was analyzed using E. coli and S. Aureus and catalytic activity was determined by the degradation of methylene blue and congo red. UV-Vis analysis showed an increase in AuNPs concentration by increasing the extract concentration, volume extract, and precursor salt concentration. The crystalline nature of AuNPs was corroborated by X-ray diffraction. TEM analysis showed nanoparticles with spherical morphology (mostly) and size between 40 and 60 nm. These results are novel because they showed a homogeneous morphology and a narrow size distribution which is difficult to obtain in green synthesis processes. Results of antibacterial activity showed inhibition zones of 11.3 mm and 10.6 mm for S. Aureus and E. coli, respectively, indicating the bactericidal capacity of the nanoparticles. The degradation periods for methylene blue and congo red were 5 and 11 min, respectively, which are very short compared with previous reports. These results are of great significance for catalytic applications. Therefore, A. triphylla extracts made possible AuNPs synthesis and the nanoparticles obtained can be used as catalytic and antibacterial materials for water remediation.

Larvicidal Activity of Synthesized Silver Nanoparticles from Curcuma zedoaria Essential Oil against Culex quinquefasciatus

Culex quinquefasciatus is the major vector of the bancroftian filarial parasite which causes human lymphatic filariasis and St. Louis encephalitis. The simple way to stop the transmission is to control the vector by using synthetic chemicals. However, herbal essential oils have biological properties, such as a larvicidal effect and are ecofriendly to use. In this study, we investigated the larvicidal activity of Curcuma zedoaria essential oil (ZEO) and biosynthesized silver nanoparticles using this essential oil (ZEO-AgNPs). The larvicidal activity against both insecticide-susceptible and -resistant strains of Cx. quinquefasciatus larvae of ZEO were investigated and compared with ZEO-AgNPs. The ZEO-AgNPs showed the utmost toxicity against both strains of Cx. quinquefasciatus. After 24 h of exposure, LC₅₀ and LC₉₉ of ZEO against susceptible strain were 36.32 and 85.11 ppm, respectively. While LC₅₀ and LC₉₉ of ZEO against the resistant strain were 37.29 and 76.79 ppm, respectively. Whereas ZEO-AgNPs offered complete larval mortality within 24 h of exposure, LC₅₀ and LC₉₉ of ZEO-AgNPs against the susceptible strain, were 0.57 and 8.54 ppm, respectively. For the resistant strain, LC₅₀ and LC₉₉ values were 0.64 and 8.88 ppm, respectively. The potency in killing Cx. quinquefasciatus and stability of ZEO-AgNPs have made this product a good candidate for the development of novel natural larvicides.

Eco-friendly synthesis of silver and gold nanoparticles with enhanced antimicrobial, antioxidant, and catalytic activities

The present work is emphasised on the bio-fabrication of silver and gold nanoparticles in a single step by a microwave-assisted method using the leaf extract of Synedrella nodiflora as both reducing and stabilising agent. The synthesised nanoparticles are highly stable and show surface plasmon resonance peak at 413 and 535 nm, respectively, for silver and gold nanoparticles in UV-Vis spectrum. The functional group responsible for the reduction of metal ions were obtained from Fourier transform infrared spectroscopy. The crystalline nature of nanoparticles with face-centred cubic geometry was confirmed by the X-ray diffraction and selected area electron diffraction patterns. The morphology and sizes of the silver and gold nanoparticles were obtained from transmission electron microscopy images. The nanoparticles exhibit effective antimicrobial activities against various pathogenic strains. These antimicrobial properties were analysed by employing agar well diffusion method. The nanoparticles show significant antioxidant properties, and it was determined using 2, 2-diphenyl-1-picrylhydrazyl assay. The nanoparticles also show potent catalytic activity in the degradation of anthropogenic pollutant dyes Congo red and eosin Y by excess NaBH4. Thus, the current study demonstrates the potential use of S. nodiflora as a reducing and stabilising agent for the synthesis of silver and gold nanoparticles and their relevance in the field of biomedicine and catalysis.

Comparison of Antimicrobial Properties of Silver Nanoparticles Synthesized from Selected Bacteria

Green silver nanoparticle (AgNP) biosynthesis is facilitated by the enzyme mediated reduction of Ag ions by plants, fungi and bacteria. The antimicrobial activity of green AgNPs is useful to overcome the challenge of antimicrobial resistance. Antimicrobial properties of biosynthesized AgNPs depend on multiple factors including culture conditions and the microbial source. The antimicrobial activity of AgNPs biosynthesized by Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Acinetobacter baumannii (confirmed clinical isolate) were investigated in this study. Biosynthesis conditions (AgNO3 concentration, pH, incubation temperature and incubation time) were optimized to obtain the maximum AgNP yield. Presence of AgNPs was confirmed by observing a characteristic UV-Visible absorbance peak in 420-435 nm range. AgNP biosynthesis was optimal at 0.4 g/L AgNO3 concentration under alkaline conditions at 60-70 °C. The biosynthesized AgNPs showed higher stability compared to chemogenized AgNPs in the presence of electrolytes. AgNPs synthesized by P. aeruginosa were the most stable while NPs of S. aureus were the least stable. AgNPs synthesized by P. aeruginosa and S. aureus showed good antimicrobial potential against E. coli, P. aeruginosa, S. aureus, MRSA and Candida albicans. AgNPs synthesized by S. aureus had greater antimicrobial activity. The antimicrobial activity of NPs may vary depending on the size and the morphology of NPs.

A review on biosynthesis of silver nanoparticles and their biocidal properties

Use of silver and silver salts is as old as human civilization but the fabrication of silver nanoparticles (Ag NPs) has only recently been recognized. They have been specifically used in agriculture and medicine as antibacterial, antifungal and antioxidants. It has been demonstrated that Ag NPs arrest the growth and multiplication of many bacteria such as Bacillus cereus, Staphylococcus aureus, Citrobacter koseri, Salmonella typhii, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, Vibrio parahaemolyticus and fungus Candida albicans by binding Ag/Ag+ with the biomolecules present in the microbial cells. It has been suggested that Ag NPs produce reactive oxygen species and free radicals which cause apoptosis leading to cell death preventing their replication. Since Ag NPs are smaller than the microorganisms, they diffuse into cell and rupture the cell wall which has been shown from SEM and TEM images of the suspension containing nanoparticles and pathogens. It has also been shown that smaller nanoparticles are more toxic than the bigger ones. Ag NPs are also used in packaging to prevent damage of food products by pathogens. The toxicity of Ag NPs is dependent on the size, concentration, pH of the medium and exposure time to pathogens.

Green synthesis of silver nanoparticles combined to calcium glycerophosphate: antimicrobial and antibiofilm activities

AIM

To synthesize, characterize and evaluate the antimicrobial and antibiofilm activities of novel nanocomposites containing silver nanoparticles (AgNPs) associated or not to β-calcium glycerophosphate.

MATERIALS & METHODS

These nanocomposites were produced through a 'green' route using extracts of different parts of pomegranate. Antimicrobial and antibiofilm properties against Candida albicans and Streptococcus mutans were determined by the minimum bactericidal/fungicidal concentration and biofilm density after treatments.

RESULTS

All extracts used were successful in producing AgNPs. Composites made with peel extracts showed the highest antimicrobial and antibiofilm activity against both microorganisms tested and performed similarly or even better than chlorhexidine.

CONCLUSION

AgNPs associated or not to calcium glycerophosphate produced by a 'green' process may be a promising novel antimicrobial agent against oral microorganisms.

Mussel inspired green synthesis of silver nanoparticles-decorated halloysite nanotube using dopamine: characterization and evaluation of its catalytic activity

Naturally occurring ceramic tubular clay, Halloysite nanotubes (HNTs), having a significant amount of surface hydroxyls has been coated by self-polymerized dopamine in this work. The polydopamine-coated HNTs acts as a self-reducing agent for Ag+ ion to Ag0 in nanometer abundance. Herein, nano size Ag0 deposited on solid support catalyst has been used to mitigate water pollution within 10 min. To establish the versatility of the catalyst, nitroaryl (4-nitrophenol) and synthetic dye (methylene blue) have been chosen as model pollutant. The degradation/reduction of the aforementioned pollutants was confirmed after taking UV–visible spectra of the respective compounds. All the study can make sure that the catalyst is green and the rate constant value for catalytic reduction of 4-nitrophenol and methylene blue was calculated to be 4.45 × 10−3 and 1.13 × 10−3 s−1, respectively, which is found to be more efficient in comparison to other nanostructure and commercial Pt/C nanocatalyst (1.00 × 10−3 s−1).

Biosynthesis of silver nanoparticles formation from Caesalpinia pulcherrima stem metabolites and their broad spectrum biological activities

The present work illustrates eco-friendly, rapid and cost effective method of AgNPs synthesis using C. pulcherrima stem extract. Initially, various physico chemical factors were optimized. Characterization was done by different spectroscopic and microscopic analysis. AgNPs were spherical in shape with an average size of 8 nm. AgNPs showed good synergistic antimicrobial, antibiofilm and antioxidant activity. The cytotoxicity effect against HeLa cancer cell line was dose dependent while genotoxic study revealed the non toxic nature of AgNPs at lower concentration. The results suggest that AgNPs from C. pulcherrima stem extract have great potential in biomedical applications.

Biosynthesis of amino acid functionalized silver nanoparticles for potential catalytic and oxygen sensing applications

A green approach to the biosynthesis of amino acid functionalized silver nanoparticles (AgNPs) using Neem gum is reported herein.

Biosynthesized silver nanoparticles: are they effective antimicrobials?

BACKGROUND

Silver nanoparticles (AgNPs) are increasingly being used in medical applications. Therefore, cost effective and green methods for generating AgNPs are required.

OBJECTIVES

This study aimed towards the biosynthesis, characterisation, and determination of antimicrobial activity of AgNPs produced using Pseudomonas aeruginosa ATCC 27853.

METHODS

Culture conditions (AgNO₃ concentration, pH, and incubation temperature and time) were optimized to achieve maximum AgNP production. The characterisation of AgNPs and their stability were evaluated by UV-visible spectrophotometry and scanning electron microscopy.

FINDINGS

The characteristic UV-visible absorbance peak was observed in the 420–430 nm range. Most of the particles were spherical in shape within a size range of 33–300 nm. The biosynthesized AgNPs exhibited higher stability than that exhibited by chemically synthesized AgNPs in the presence of electrolytes. The biosynthesized AgNPs exhibited antimicrobial activity against Escherichia coli, P. aeruginosa, Salmonella typhimurium, Staphylococcus aureus, methicillin-resistant S. aureus, Acinetobacter baumannii, and Candida albicans.

MAIN CONCLUSION

As compared to the tested Gram-negative bacteria, Gram-positive bacteria required higher contact time to achieve 100% reduction of colony forming units when treated with biosynthesized AgNPs produced using P. aeruginosa.

Larvicidal and pupicidal evaluation of silver nanoparticles synthesized using Aquilaria sinensis and Pogostemon cablin essential oils against dengue and zika viruses vector Aedes albopictus mosquito and its histopathological analysis

Mosquitoes pose a threat to humans and animals, causing millions of deaths every year. Vector control by effective eco-friendly pesticides of natural origin is a serious issue that requires urgent attention. The employment of green-reducing extracts for nanoparticles biosynthesis in a rapid and single-step process represents a promising strategy. In this study, silver nanoparticles (AgNPs) were biofabricated using an essential oil of Aquilaria sinensis (AsEO) and Pogostemonis Herba essential oil of Pogostemon cablin (PcEO) in one step and cost-effective manner. UV-vis spectrophotometry, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis and energy-dispersive X-ray spectroscopy were used to confirm the AgNPs formation and their biophysical characterization. The larvicidal and pupicidal toxicity of AsEO, PcEO and biosynthesized AgNPs were evaluated against larvae and pupae of the dengue and Zika virus vector Aedes albopictus. Compared to the tested essential oils, the biofabricated AgNPs showed the highest toxicity against larvae and pupae of Ae.albopictus. In particular, the LC₅₀ values of AsEO ranged from 44.23 (I) to 166 (pupae), LC₅₀ values of PcEO ranged from 32.49 (I) to 90.05(IV), LC₅₀ values of AsEO-AgNPs from 0.81 (I) to 1.12 (IV) and LC₅₀ values of PcEO-AgPNs from 0.85 (I) to 1.19 (IV). Furthermore, histological analysis of the midgut cells of the control and treated larvae exhibited that the epithelial cells and brush border were highly affected by the fabricated AgNPs compared to the essential oils (AsEO and PcEO). Overall, the A. sinensis and P. cablin essential oils fabricated AgNPs have a potential of application as a biopesticide for mosquito control through safer and cost-effective approach.

Facile synthesis of multifunctional silver nanoparticles using mangrove plant Excoecaria agallocha L. for its antibacterial, antioxidant and cytotoxic effects

The current study describes a simple, rapid and eco-friendly method for the synthesis of silver nanoparticles (AgNPs) using Excoecaria agallocha (E. agallocha) leaf extract as stabilizer, bioreductant and capping agent. Synthesized AgNPs were characterized by UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX). Generation of AgNPs was initially confirmed with the color change from yellow to dark brown which produces intense absorbance spectra at 440 nm in UV-Vis spectroscopy without any shifting of peaks. Further, XRD pattern confirms that the synthesized AgNPs was face centered cubic (fcc) crystalline in structure with an average size of 20 nm. On the other hand, FTIR spectrum reveals that the active metabolites like water soluble phenolic compounds, flavonoids, methylene groups, amides and carboxylate groups. These active biocompounds plays a vital role in the reduction of Ag⁺ into their nanoscale values, it also acts as a stabilizing and surface functionalization agent. FESEM micrographs of synthesized AgNPs shows spherical and hexagonal shaped well dispersed particles in the dimension ranging between 23 and 42 nm. EDAX confirms the presence of silver (Ag) as the major constituent element without any impurities; also substantiate the stability of generated AgNPs. The biomedical insights of nanoparticles (NPs) were assessed through radical scavenging and antibacterial properties. Additionally, synthesized AgNPs was also exhibits an excellent cytotoxic effect against human breast carcinoma cell lines (MCF-7). This study proves that synthesized AgNPs can be developed as a potential nano-drug formulation to combat pathogenic disease and also for the expansion of breast cancer therapy.