Green Synthesis of Ag/Ag₂O Nanoparticles Using Aqueous Leaf Extract of Eupatorium odoratum and Its Antimicrobial and Mosquito Larvicidal Activities

Green Synthesis of Silver Oxide Nanoparticles from Mauritia flexuosa Fruit Extract: Characterization and Bioactivity Assessment

The increasing prevalence of multidrug-resistant (MDR) pathogens, persistent biofilms, oxidative stress, and cancerous cell proliferation poses significant challenges in healthcare and environmental settings, highlighting the urgent need for innovative and sustainable therapeutic solutions. The exploration of nanotechnology, particularly the use of green-synthesized nanoparticles, offers a promising avenue to address these complex biological challenges due to their multifunctional properties and biocompatibility. Utilizing a green synthesis approach, Mauritia flexuosa Mf-Ag2ONPs were synthesized and characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy coupled with scanning electron microscopy (EDS-SEM), UV-Vis spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The Mf-Ag2ONPs exhibited potent antibacterial effects against both non-resistant and MDR bacterial strains, with minimum inhibitory concentrations (MICs) ranging from 11.25 to 45 µg/mL. Mf-Ag2ONPs also demonstrated significant antifungal efficacy, particularly against Candida glabrata, with an MIC of 5.63 µg/mL. Moreover, the nanoparticles showed strong biofilm inhibition capabilities and substantial antioxidant properties, underscoring their potential to combat oxidative stress. Additionally, Mf-Ag2ONPs exhibited pronounced anticancer properties against various cancer cell lines, displaying low IC50 values across various cancer cell lines while maintaining minimal hemolytic activity at therapeutic concentrations. These findings suggest that Mf-Ag2ONPs synthesized via an eco-friendly approach offer a promising alternative for biomedical applications, including antimicrobial, antifungal, antioxidant, and anticancer therapies, warranting further in vivo studies to fully exploit their therapeutic potential.

Investigating antibacterial activity of biosynthesized silver oxide nanoparticles using Phragmanthera Macrosolen L. leaf extract

The crude leaf extract of Phragmanthera macrosolen L. has been utilized for the first time as an effective reducing, capping and stabilizing agent to synthesize silver oxide nanoparticles (Ag2O NPs) through a green approach. The prepared Ag2O NPs were analyzed by scanning electron-microscopy (SEM), High Resolution Transmission electron microscope (HR-TEM), X-ray diffractions (XRD), Fourier transforms infrared (FTIR) spectroscopy, energy dispersive spectroscopy (EDS), and Ultra-violet visible spectrometry (UV-Vis). The biosynthesized Ag2O NPs applied on gram-positive (S. aureus) and gram-negative (E. coli) bacterial types. FTIR spectral peaks indicate that the phytochemicals in the extract are responsible for the formation of Ag2O nanoparticles. The XRD result shown, poly-crystalline nanoparticles and the average crystalline size calculated was 45.8 nm. UV-Vis analysis shows absorbance existed at 590.5 nm, and the energy band gap calculated through the Tauc relation was 2.1 eV. The SEM images gave a globular and some rod like morphology with diameter of particle obtained between 20.11 and 46.50 nm with some hollow cubic microstructure of Ag2O NPs which makes it suitable for antimicrobial application. The EDS confirms the elemental composition and existence of Ag and O2. The HR-TEM images, specific area electron diffraction (SAED), and XRD patterns confirmed the morphology of Ag2O NPs mean 45.84 nm and polycrystalline nature of the nanoparticles. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were 15 and 30 µl respectively for the samples tested. In this study, it was observed that Ag2O NPs highly sensitive to E. coli than s. aureus. The present study revealed that the possible use of green synthesized Ag2O NPs as potential antibacterial agent.

Biogenically synthesized green silver nanoparticles exhibit antimalarial activity

The suboptimal efficacies of existing anti-malarial drugs attributed to the emergence of drug resistance dampen the clinical outcomes. Hence, there is a need for developing novel drug and drug targets. Recently silver nanoparticles (AgNPs) constructed with the leaf extracts of Euphorbia cotinifolia were shown to possess antimalarial activity. Therefore, the synthesized AgNPs from Euphorbia cotinifolia (EcAgNPs) were tested for their parasite clearance activity. We determined the antimalarial activity in the asexual blood stage infection of 3D7 (laboratory strain) P. falciparum. EcAgNPs demonstrated the significant inhibition of parasite growth (EC50 of 0.75 µg/ml) in the routine in vitro culture of P. falciparum. The synthesized silver nanoparticles were seen to induce apoptosis in P. falciparum through increased reactive oxygen species (ROS) ROS production and activated programmed cell death pathways characterized by the caspase-3 and calpain activity. Also, altered transcriptional regulation of Bax/Bcl-2 ratio indicated the enhanced apoptosis. Moreover, inhibited expression of PfLPL-1 by EcAgNPs is suggestive of the dysregulated host fatty acid flux via parasite lipid storage. Overall, our findings suggest that EcAgNPs are a non-toxic and targeted antimalarial treatment, and could be a promising therapeutic approach for clearing malaria infection.

Synergistic effect of Silver-Nanodiamond composite as an efficient antibacterial agent against E. coli and S. aureus

Bacterial antimicrobial resistance (BAMR) seems to pose the greatest threat to public health, food safety, and agriculture in this century. The development of novel efficient antimicrobial agents to combat bacterial infections has become a global issue. Silver nanoparticles (Ag NPs) appeared as a feasible alternative to antibiotics. However, Ag NPs face cost, toxicity, and aggregation issues which limit their antibacterial activity. This work aims to stabilize Ag NPs with enhanced antimicrobial activity at comparatively lower Ag concentrations to prevent bacterial infections. For this purpose, the Ag core was covered with nanodiamonds (NDs). Ag-NDs composite have been synthesized by microplasma technique. TEM analysis confirmed the presence of both Ag and NDs in the Ag-NDs composite. A particle size (∼19 nm) was reported for Ag-NDs at the highest concentration as compared to Ag NPs (∼3 nm). The conduction band of the diamond acted as an extremely strong reducing agent for Ag NPs. The large surface area of NDs stabilized the Ag NPs. A redshift (∼400 nm-406 nm) in UV-visible spectra of the Ag-NDs composite indicated the formation of bigger-sized Ag NPs after incorporating NDs. XRD and LIBS analysis verified the increase in intensity of Ag-NPs by increasing ND concentration. The presence of functional groups including OH, CH, and Ag/Ag2O was confirmed by FTIR. Bacterial inhibition growth appeared to be a dose-dependent process. The minimum inhibition concentration value of Ag-NDs composite at the highest NDs concentration against E. coli (∼ 0.69 μg/ml) and S. aureus (∼44 μg/ml). This is the first study to report the smallest MIC for E. coli (<1 μg/ml). Ag-ND composites emerged to be more efficient than Ag NPs and preferred to be used against BAMR. The enhanced antibacterial activity of the Ag-NDs composite makes it a potential candidate for antibiotics, food products, and pesticides.

Synthesis of Silver Oxide Nanoparticles: A Novel Approach for Antimicrobial Properties and Biomedical Performance, Featuring Nodularia haraviana from the Cholistan Desert

Nanoparticles have emerged as a prominent area of research in recent times, and silver nanoparticles (AgNPs) synthesized via phyco-technology have gained significant attention due to their potential therapeutic applications. Nodularia haraviana, a unique and lesser-explored cyanobacterial strain, holds substantial promise as a novel candidate for synthesizing nanoparticles. This noticeable research gap underscores the novelty and untapped potential of Nodularia haraviana in applied nanotechnology. A range of analytical techniques, including UV-vis spectral analysis, dynamic light scattering spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray powder diffraction, were used to investigate and characterize the AgNPs. Successful synthesis of AgNPs was confirmed through UV-visible spectroscopy, which showed a surface plasmon resonance peak at 428 nm. The crystalline size of AgNPs was 24.1 nm. Dynamic light scattering analysis revealed that silver oxide nanoparticles had 179.3 nm diameters and a negative surface charge of -18 mV. Comprehensive in vitro pharmacogenetic properties revealed that AgNPs have significant therapeutic potential. The antimicrobial properties of AgNPs were evaluated by determining the minimum inhibitory concentration against various microbial strains. Dose-dependent cytotoxicity assays were performed on Leishmanial promastigotes (IC50: 18.71 μgmL-1), amastigotes (IC50: 38.6 μgmL-1), and brine shrimps (IC50: 134.1 μg mL-1) using various concentrations of AgNPs. The findings of this study revealed that AgNPs had significant antioxidant results (DPPH: 57.5%, TRP: 55.4%, TAC: 61%) and enzyme inhibition potential against protein kinase (ZOI: 17.11 mm) and alpha-amylase (25.3%). Furthermore, biocompatibility tests were performed against macrophages (IC50: >395 μg mL-1) and human RBCs (IC50: 2124 μg mL-1). This study showed that phyco-synthesized AgNPs were less toxic and could be used in multiple biological applications, including drug design and in the pharmaceutical and biomedical industries. This study offers valuable insights and paves the way for further advancements in AgNPs research.

Green synthesis of Ag2O nanoparticles using Punica granatum leaf extract for sulfamethoxazole antibiotic adsorption: characterization, experimental study, modeling, and DFT calculation

Silver oxide (Ag2O) nanoparticles (NPs) were generated by synthesizing green leaf extract of Punica granatum, and afterwards they were used as adsorbent to remove the antibiotic additive sulfamethoxazole (SMX) from aqueous solutions. Prior of their use as adsorbent, the Ag2O NPs were characterized by various methods such as X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy/energy-dispersive X-ray (SEM-EDX), and transmission electron microscopy (TEM). The Ag2O NPs were found to be spherically shaped and stabilized by the constituents of the extract. Further, at SMX antibiotic concentration of 100 mg L-1, the Ag2O NPs achieved almost complete removal of 98.93% within 90 min, and by using 0.8 g L-1 of adsorbent dose at pH=4 and temperature T=308 K. In addition, the experimental data were well fitted with the theoretical Langmuir model indicating homogeneous adsorbed layer of the SMX antibiotic on the Ag2O NPs surface. The maximum uptake capacity was 277.85 mg g-1. A good agreement was also found between the kinetic adsorption data and the theoretical pseudo-second-order model. Regarding the thermodynamic adsorption aspects, the data revealed an endothermic nature and confirmed the feasibility and the spontaneity of the adsorption reaction. Furthermore, the regeneration study has shown that the Ag2O NPs could be efficiently reused for up to five cycles. The geometric structures have been optimized and quantum chemical parameters were calculated for the SMX unprotonated (SMX+/-) and protonated (SMX+) using density functional theory (DFT) calculation. The DFT results indicated that the unprotonated SMX+/- reacts more favorably on the Ag2O surface, as compared to the protonated SMX+. The SMX binding mechanism was predominantly controlled by the electrostatic attraction, hydrogen bond, hydrophobic, and π-π interactions. The overall data suggest that the Ag2O NPs have promising potential for antibiotic removal from wastewater.

Characterization of Silver Nanoparticles Synthesized by the Aqueous Extract of Zanthoxylum nitidum and Its Herbicidal Activity against Bidens pilosa L

Phytosynthesis of silver nanoparticles (Ag NPs) has been progressively acquiring attractiveness. In this study, the root of Zanthoxylum nitidum was used to synthesize Ag NPs, and its pre-emergence herbicidal activity was tested. The synthesized Ag NPs by the aqueous extract from Z. nitidum were characterized by visual inspection, ultraviolet-visible spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The plant-mediated synthesis was completed within 180 min and the Ag NPs exhibited a characteristic peak at around 445 nm. The results of the DLS measurement showed that the average hydrodynamic diameter was 96 nm with a polydispersity index (PDI) of 0.232. XRD results indicated the crystalline nature of the phytogenic Ag NPs. A TEM analysis revealed that the nanoparticles were spherical with an average particle size of 17 nm. An EDX spectrum confirmed the presence of an elemental silver signal. Furthermore, the Ag NPs exhibited a herbicidal potential against the seed germination and seedling growth of Bidens Pilosa L. The present work indicates that Ag NPs synthesized by plant extract could have potential for the development of a new nanoherbicide for weed prevention and control.

Green Synthesis of Bioinspired Nanoparticles Mediated from Plant Extracts of Asteraceae Family for Potential Biological Applications

The Asteraceae family is one of the largest families in the plant kingdom with many of them extensively used for significant traditional and medicinal values. Being a rich source of various phytochemicals, they have found numerous applications in various biological fields and have been extensively used for therapeutic purposes. Owing to its potential phytochemicals present and biological activity, these plants have found their way into pharmaceutical industry as well as in various aspects of nanotechnology such as green synthesis of metal oxide nanoparticles. The nanoparticles developed from the plants of Asteraceae family are highly stable, less expensive, non-toxic, and eco-friendly. Synthesized Asteraceae-mediated nanoparticles have extensive applications in antibacterial, antifungal, antioxidant, anticancer, antidiabetic, and photocatalytic degradation activities. This current review provides an opportunity to understand the recent trend to design and develop strategies for advanced nanoparticles through green synthesis. Here, the review discussed about the plant parts, extraction methods, synthesis, solvents utilized, phytochemicals involved optimization conditions, characterization techniques, and toxicity of nanoparticles using species of Asteraceae and their potential applications for human welfare. Constraints and future prospects for green synthesis of nanoparticles from members of the Asteraceae family are summarized.

Synthesis and characterization of Ag2O, CoFe2O4, GO, and their ternary composite for antibacterial activity

Currently, nanomaterials with exceptional antibacterial activity have become an emerging domain in research. The optimization of nanomaterials against infection causing agents is the next step in dealing with the present-day problem of antibiotics. In this research work, Ag₂O, CoFe₂O₄, and Ag₂O/CoFe₂O₄/rGO are prepared by chemical methods. Ag₂O was prepared by co-precipitation method, while solvothermal technique was utilized for the synthesis of CoFe₂O₄. The ternary nanocomposite was synthesized by a simple in situ reduction using a two-step approach. The structural and morphological properties were studied by UV-Vis spectroscopy, X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (SEM), dynamic light scattering (DLS), and Fourier-transform infrared spectroscopy (FTIR). From the X-ray diffraction analysis, the crystallite size is found to be 14 nm, 5 nm, and 6 nm for Ag₂O, CoFe₂O₄, and Ag₂O/CoFe₂O₄/rGO respectively. The synthesized nanomaterials were investigated for antibacterial activities against gram-positive strain Staphylococcus aureus (S. aureus) and gram-negative strain Escherichia coli (E. coli) using Agar well diffusion method. Ag₂O and CoFe₂O₄ showed zones of inhibition (ZOI) of 13 mm and 11 mm against gram positive bacteria while 12 mm against gram negative bacteria respectively, while ternary nanocomposite showed 14 mm and 13 mm of ZOI. The antibacterial activity of nanomaterials showed a gradual increment with an increase in the concentration of the materials. Ag₂O, CoFe₂O₄, and Ag₂O/CoFe₂O₄/rGO showed minimum inhibitory concentration (MIC) values of 4.5, 6.5, and 4.5 μg/mL for S. aureus and 6.5, 7.2, and 4.8 μg/mL for E. coli respectively. Minimum bactericidal concentrations were found to be same as the MIC values. Additionally, a time-kill curve analysis was performed and for ternary nanocomposite; the killing response was most effective as the complete killing was achieved at 3 h of incubation at 3-MIC (9.75 μg/mL). These results demonstrate that all the nanomaterials, as a kind of antibacterial material, have a great potential for a wide range of biomedical applications.

Ag2O Nanoparticles as a Candidate for Antimicrobial Compounds of the New Generation

Antibiotic resistance in microorganisms is an important problem of modern medicine which can be solved by searching for antimicrobial preparations of the new generation. Nanoparticles (NPs) of metals and their oxides are the most promising candidates for the role of such preparations. In the last few years, the number of studies devoted to the antimicrobial properties of silver oxide NPs have been actively growing. Although the total number of such studies is still not very high, it is quickly increasing. Advantages of silver oxide NPs are the relative easiness of production, low cost, high antibacterial and antifungal activities and low cytotoxicity to eukaryotic cells. This review intends to provide readers with the latest information about the antimicrobial properties of silver oxide NPs: sensitive organisms, mechanisms of action on microorganisms and further prospects for improving the antimicrobial properties.

Recent advances on botanical biosynthesis of nanoparticles for catalytic, water treatment and agricultural applications: A review

Green synthesis of nanoparticles using plant extracts minimizes the usage of toxic chemicals or energy. Here, we concentrate on the green synthesis of nanoparticles using natural compounds from plant extracts and their applications in catalysis, water treatment and agriculture. Polyphenols, flavonoid, rutin, quercetin, myricetin, kaempferol, coumarin, and gallic acid in the plant extracts engage in the reduction and stabilization of green nanoparticles. Ten types of nanoparticles involving Ag, Au, Cu, Pt, CuO, ZnO, MgO, TiO₂, Fe₃O₄, and ZrO₂ with emphasis on their formation mechanism are illuminated. We find that green nanoparticles serve as excellent, and recyclable catalysts for reduction of nitrophenols and synthesis of organic compounds with high yields of 83-100% and at least 5 recycles. Many emerging pollutants such as synthetic dyes, antibiotics, heavy metal and oils are effectively mitigated (90-100%) using green nanoparticles. In agriculture, green nanoparticles efficiently immobilize toxic compounds in soil. They are also sufficient nanopesticides to kill harmful larvae, and nanoinsecticides against dangerous vectors of pathogens. As potential nanofertilizers and nanoagrochemicals, green nanoparticles will open a revolution in green agriculture for sustainable development.

Plant Extract-Based Synthesis of Metallic Nanomaterials, Their Applications, and Safety Concerns

Nanotechnology has attracted the attention of researchers from different scientific fields because of the escalated properties of nanomaterials compared with the properties of macromolecules. Nanomaterials can be prepared through different approaches involving physical and chemical methods. The development of nanomaterials through plant-based green chemistry approaches is more advantageous than other methods from the perspectives of environmental safety, animal, and human health. The biomolecules and metabolites of plants act as reducing and capping agents for the synthesis of metallic green nanomaterials. Plant-based synthesis is a preferred approach as it is not only cost-effective, easy, safe, clean, and eco-friendly but also provides pure nanomaterials in high yield. Since nanomaterials have antimicrobial and antioxidant potential, green nanomaterials synthesized from plants can be used for a variety of biomedical and environmental remediation applications. Past studies have focused mainly on the overall biogenic synthesis of individual or combinations of metallic nanomaterials and their oxides from different biological sources, including microorganisms and biomolecules. Moreover, from the viewpoint of biomedical applications, the literature is mainly focusing on synthetic nanomaterials. Herein, we discuss the extraction of green molecules and recent developments in the synthesis of different plant-based metallic nanomaterials, including silver, gold, platinum, palladium, copper, zinc, iron, and carbon. Apart from the biomedical applications of metallic nanomaterials, including antimicrobial, anticancer, diagnostic, drug delivery, tissue engineering, and regenerative medicine applications, their environmental remediation potential is also discussed. Furthermore, safety concerns and safety regulations pertaining to green nanomaterials are also discussed. This article is protected by copyright. All rights reserved.

Methods for Green Synthesis of Metallic Nanoparticles Using Plant Extracts and their Biological Applications - A Review

Nanotechnology, a fast-developing branch of science, is gaining extensive popularity among researchers simply because of the multitude of applications it can offer. In recent years, biological synthesis has been widely used instead of physical and chemical synthesis methods, which often produce toxic products. These synthesis methods are now being commonly adapted to discover new applications of nanoparticles synthesized using plant extracts. In this review, we elucidate the various ways by which nanoparticles can be biologically synthesized. We further discuss the applications of these nanoparticles.

Green Synthesis of Silver Oxide Nanoparticles for Photocatalytic Environmental Remediation and Biomedical Applications

Among the most notable nanotechnology applications is its employment in environmental remediation and biomedical applications. Nonetheless, there is a need for cleaner and sustainable methods in preparing nanomaterials that use cheaper, more environment-friendly precursors than the conventional synthesis process. The green chemistry approach for the preparation of nanoparticles is becoming more attractive as it uses non-toxic chemicals and reagents. It also offers cost-effective synthesis process as it uses readily available plant sources and microbe as redox mediators in converting metallic cations to metal or metal oxide nanoparticles. The extracts of these plants and microbe sources contain phytochemicals and metabolites in variable quantities, which serve as redox mediators and capping agents that stabilize the biosynthesized nanoparticles. The present article reviews the recent studies on the fabrication of silver oxide nanoparticles (Ag2O-NPs) via plant-mediated and microbe-mediated green synthesis, giving a concise discussion on the green preparation of Ag2O-NPs employing extracts of different plants and microbial sources. The performances of the biosynthesized Ag2O-NPs are also reviewed, highlighting their potential use in photocatalysis and biomedical applications.

Formation, antimicrobial activity, and biomedical performance of plant-based nanoparticles: a review

Because many engineered nanoparticles are toxic, there is a need for methods to fabricate safe nanoparticles such as plant-based nanoparticles. Indeed, plant extracts contain flavonoids, amino acids, proteins, polysaccharides, enzymes, polyphenols, steroids, and reducing sugars that facilitate the reduction, formation, and stabilization of nanoparticles. Moreover, synthesizing nanoparticles from plant extracts is fast, safe, and cost-effective because it does not consume much energy, and non-toxic derivatives are generated. These nanoparticles have diverse and unique properties of interest for applications in many fields. Here, we review the synthesis of metal/metal oxide nanoparticles with plant extracts. These nanoparticles display antibacterial, antifungal, anticancer, and antioxidant properties. Plant-based nanoparticles are also useful for medical diagnosis and drug delivery.

One-pot fabrication of Ag @Ag2O core-shell nanostructures for biosafe antimicrobial and antibiofilm applications

Microbial contamination is one of the major dreadful problems that raises hospitalization, morbidity and mortality rates globally, which subsequently obstructs socio-economic progress. The continuous misuse and overutilization of antibiotics participate mainly in the emergence of microbial resistance. To circumvent such a multidrug-resistance phenomenon, well-defined nanocomposite structures have recently been employed. In the current study, a facile, novel and cost-effective approach was applied to synthesize Ag@Ag₂O core-shell nanocomposites (NCs) via chemical method. Several techniques were used to determine the structural, morphological, and optical characteristics of the as-prepared NCs. XRD, Raman, FTIR, XPS and SAED analysis revealed a crystalline hybrid structure of Ag core and Ag₂O shell. Besides, SEM and HRTEM micrographs depicted spherical nanoparticles with size range of 19-60 nm. Additionally, zeta potential and fluorescence spectra illustrated aggregated nature of Ag@Ag₂O NCs by - 5.34 mV with fluorescence emission peak at 498 nm. Ag@Ag₂O NCs exhibited higher antimicrobial, antibiofilm, and algicidal activity in dose-dependent behavior. Interestingly, a remarkable mycocidal potency by 50 μg of Ag@Ag₂O NCs against Candida albican; implying promising activity against COVID-19 white fungal post-infections. Through assessing cytotoxicity, Ag@Ag₂O NCs exhibited higher safety against Vero cells than bulk silver nitrate by more than 100-fold.

Application of mycogenic silver/silver oxide nanoparticles in electrochemical glucose sensing; alongside their catalytic and antimicrobial activity

The present work describes the biofabrication of highly stable, water-dispersible mycogenic silver/silver (I) oxide nanoparticles (Ag/Ag₂O NPs) alongside its potential applications in non-enzymatic electrochemical glucose sensing and catalytic degradation of methylene blue (MB) dye in presence of reducing agent NaBH₄. These Ag/Ag₂O NPs were fabricated from silver oxide micro powder using endophytic fungus Fusarium oxysporum based environmentally friendly, bio-inspired, top-down approach which is highly reproducible, reliable, and cheap. Bacterial and plant-mediated bottom-up approaches have been previously reported for the production of Ag/Ag₂O NPs. Bacterial methods are not economical as they require expensive sophisticated instruments for separation and purification. Similarly, plant-based means of synthesis are not reliable and reproducible due to geographical and seasonal variability's. UV-Visible spectroscopy, TEM, SAED, FTIR, XRD, TGA, and DSC were used for the characterization and investigation of thermal properties of mycogenic nanoparticles and their antimicrobial activity was evaluated by filter- paper bioassay technique.

Green Synthesized of Ag/Ag2O Nanoparticles Using Aqueous Leaves Extracts of Phoenix dactylifera L. and Their Azo Dye Photodegradation

In this study, silver/silver oxide nanoparticles (Ag/Ag2O NPs) were successfully biosynthesized using Phoenix dactylifera L. aqueous leaves extract. The effect of different plant extract/precursor contractions (volume ratio, v/v%) on Ag/Ag2O NP formation, their optical properties, and photocatalytic activity towards azo dye degradation, i.e., Congo red (CR) and methylene blue (MB), were investigated. X-ray diffraction confirmed the crystalline nature of Ag/Ag2O NPs with a crystallite size range from 28 to 39 nm. Scanning electron microscope images showed that the Ag/Ag2O NPs have an oval and spherical shape. UV-vis spectroscopy showed that Ag/Ag2O NPs have a direct bandgap of 2.07-2.86 eV and an indirect bandgap of 1.60-1.76 eV. Fourier transform infrared analysis suggests that the synthesized Ag/Ag2O NPs might be stabilized through the interactions of -OH and C=O groups in the carbohydrates, flavonoids, tannins, and phenolic acids present in Phoenix dactylifera L. Interestingly, the prepared Ag/Ag2O NPs showed high catalytic degradation activity for CR dye. The photocatalytic degradation of the azo dye was monitored spectrophotometrically in a wavelength range of 250-900 nm, and a high decolorization efficiency (84.50%) was obtained after 50 min of reaction. As a result, the use of Phoenix dactylifera L. aqueous leaves extract offers a cost-effective and eco-friendly method.

Elucidation of larvicidal potential of metallic and environment friendly food-grade nanostructures against Aedes albopictus

To combat health challenges associated with mosquito-borne diseases, the larvicidal activity of metallic nanoparticles, food-grade polymeric nano-capsules and insecticides was investigated against larvae of Aedes albopictus as an effective alternate control approach. The Ae. albopictus was identified using sequencing and phylogenetic analyses of COXI, CYTB and ITS2 genes. The characterization of synthesized nanostructures was performed through Zetasizer, UV-VIS spectroscopy, atomic force microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The mosquito larvae were exposed to varying concentration of nanostructures and insecticides, and their percentage mortality was evaluated at different time intervals of 24 h and 48 h exposure. The highest efficacy was observed in zinc oxide nanoparticles (ZnO-NPs) and polymeric nanocapsules FG-Cur E-III (LC50 = 0.24 mg/L, LC90 = 0.6 mg/L) and (LC50 = 3.8 mg/L, LC90 = 9.33 mg/L), respectively, after 24 h; while (LC50 = 0.18 mg/L, LC90 = 0.43 mg/L) and (LC50 = 1.95 mg/L, LC90 = 6.46 mg/L), respectively, after 48 h against fourth instar larvae of Ae. albopictus. Ag, CuO, NiTiO3 and CoTiO3 nanoparticles evaluated in this study also showed promising larvicidal activity. Although ZnO-NPs proved to be effective larvicides, their possible toxicity (producing ROS species) can limit their use. The curcumin nanostructures (FG-Cur E-III) stabilized by food-grade materials are thought to exert their larvicidal activity by binding to sterol carrier protein-2, and depriving the larvae from the essential dietary cholesterol, and bears effective larvicidal potential as safe alternative for chemical larvicides, due to their environment friendly, food-grade and easy biodegradability.

Through quorum sensing, Pseudomonas aeruginosa resists noble metal-based nanomaterials toxicity

Noble metal-based nanomaterials (NMNs), such as platinum nanoparticles (Pt@NPs) and palladium nanoparticles (Pd@NPs), are increasingly being used as antibacterial agents. However, little information is available on bacterial resistance to NMNs. In this study, owing to their oxidase-like and peroxidase-like properties, both Pt@NPs and Pd@NPs induce reactive oxygen species (ROS) and manifest antibacterial activities: 6.25 μg/mL of either Pt@NPs or Pd@NPs killed >50% of Staphylococcus aureus strain ATCC29213. However, Pseudomonas aeruginosa strain PAO1 completely resisted 12.5 μg/mL of Pt@NPs and 6.25 μg/mL of Pd@NPs. Compared to the non-NMN groups, these NMNs promoted 2-3-fold upregulation of the quorum sensing (QS) gene lasR in strain PAO1. In fact, the lasR gene upregulation induced a 1.5-fold reduction in ROS production and increased biofilm formation by 11% (Pt@NPs) and 27% (Pd@NPs) in strain PAO1. The ΔlasR mutants (lasR gene knock out in strain PAO1), became sensitive to NMNs. The survival rates of ΔlasR mutants at 12.5 μg/mL Pt@NPs and Pd@NPs treatments were only 77% and 58%, respectively. This is the first report indicating that bacteria can resist NMNs through QS. Based on these results, evaluation of the ecological risks of using NMNs as antibacterial agents is necessary.

Potential Role of Plant Extracts and Phytochemicals Against Foodborne Pathogens

Foodborne diseases are one of the major causes of morbidity and mortality, especially in low-income countries with poor sanitation and inadequate healthcare facilities. The foremost bacterial pathogens responsible for global outbreaks include Salmonella species, Campylobacter jejuni, Escherichia coli, Shigella sp., Vibrio, Listeria monocytogenes and Clostridium botulinum. Among the viral and parasitic pathogens, norovirus, hepatitis A virus, Giardia lamblia, Trichinella spiralis, Toxoplasma and Entamoeba histolytica are commonly associated with foodborne diseases. The toxins produced by Staphylococcus aureus, Bacillus cereus and Clostridium perfringens also cause these infections. The currently available therapies for these infections are associated with various limited efficacy, high cost and side-effects. There is an urgent need for effective alternative therapies for the prevention and treatment of foodborne diseases. Several plant extracts and phytochemicals were found to be highly effective to control the growth of these pathogens causing foodborne infections in in vitro systems. The present review attempts to provide comprehensive scientific information on major foodborne pathogens and the potential role of phytochemicals in the prevention and treatment of these infections. Further detailed studies are necessary to evaluate the activities of these extracts and phytochemicals along with their mechanism of action using in vivo models.

Synthesis of nanohybrids of polycarbazole with α-MnO2 derived from Brassica oleracea: a comparison of photocatalytic degradation of an antibiotic drug under microwave and UV irradiation

The present work describes the synthesis of α-MnO₂ nanorods using a natural extract of Brassica oleracea (cabbage) and the formulation of its nanohybrids with polycarbazole, i.e., α-MnO₂/PCz. Synergistic interaction between PCz and MnO₂ is revealed from infrared spectroscopy (IR) studies while the composition is determined by X-ray photoelectron spectroscopy (XPS). The formation of α-MnO₂ nanorods is confirmed via high-resolution transmission electron microscopy (HRTEM). The indirect bandgap of α-MnO₂ is reported as 2.5 eV while for the nanohybrids it is found to be ranging between 2.3 and 2.5 eV. Results show that 91% and 89% of degradation is achieved within 30 min and 90 min under the microwave and UV irradiation respectively. Hydroxyl radicals (^•OH) and superoxide (^•O₂^-) radicals are responsible for photocatalytic degradation of the drug Bactrim DS which is confirmed by radical scavenging experiments. The nanohybrids show promising catalytic activity under UV as well as microwave irradiation.

Synthesis of Silver Nanoparticles and their Biomedical Applications - A Comprehensive Review

Generally, silver is considered as a noble metal used for treating burn wound infections, open wounds and cuts. However, the emerging nanotechnology has made a remarkable impact by converting metallic silver into silver nanoparticles (AgNPs) for better applications. The advancement in technology has improved the synthesis of NPs using biological method instead of physical and chemical methods. Nonetheless, synthesizing AgNPs using biological sources is ecofriendly and cost effective. Till date, AgNPs are widely used as antibacterial agents; therefore, a novel idea is needed for the successful use of AgNPs as therapeutic agents to uncertain diseases and infections. In biomedicine, AgNPs possess significant advantages due to their physical and chemical versatility. Indeed, the toxicity concerns regarding AgNPs have created the need for non-toxic and ecofriendly approaches to produce AgNPs. The applications of AgNPs in nanogels, nanosolutions, silver based dressings and coating over medical devices are under progress. Still, an improvised version of AgNPs for extended applications in an ecofriendly manner is the need of the hour. Therefore, the present review emphasizes the synthesis methods, modes of action under dissipative conditions and the various biomedical applications of AgNPs in detail.

Application of protein-functionalised aluminium nanosheets synthesised from sewage sludge for dye removal in a fixed-bed column: Investigation on design parameters and kinetic models

Protein-functionalised aluminium nanosheets (PRS-AlNs) were packed in a continuous fixed-bed column to remove crystal violet (CV) and Congo red (CR) dyes. A group of characterisation techniques, like SEM, TEM, AFM, XRD, BET, DSC and Raman spectroscopy, was performed for PRS-AlNs. The influence of several factors like bed depth (1, 2 and 3 cm), inlet dye concentration (50, 100 and 150 mg/L) and inlet flow rate (1.17, 2.26 and 3.34 mL/min) on the characteristics of the breakthrough profile of the adsorption process was examined at optimum pH 9.8 and 3.5 for CV and CR, respectively. The maximum adsorption capacity was achieved as 38.70 and 57.86 mg/g for CV and CR at 1 cm bed depth, 150 mg/L inlet concentration of the dye and 3.34 mL/min inlet rate of flow. The experimental data were analysed using kinetic models like the Yoon-Nelson, Adams-Bohart and Thomas models. Also, a detailed mechanism behind the CV and CR adsorption using PRS-AlNs was proposed in this research work. Graphical abstract .

Plant extracts for developing mosquito larvicides: From laboratory to the field, with insights on the modes of action

In the last decades, major research efforts have been done to investigate the insecticidal activity of plant-based products against mosquitoes. This is a modern and timely challenge in parasitology, aimed to reduce the frequent overuse of synthetic pesticides boosting resistance development in mosquitoes and causing serious threats to human health and environment. This review covers the huge amount of literature available on plant extracts tested as mosquito larvicides, particularly aqueous and alcoholic ones, due to their easy formulation in water without using surfactants. We analysed results obtained on more than 400 plant species, outlining that 29 of them have outstanding larvicidal activity (i.e., LC₅₀ values below 10 ppm) against major vectors belonging to the genera Anopheles, Aedes and Culex, among others. Furthermore, synergistic and antagonistic effects between plant extracts and conventional pesticides, as well as among selected plant extracts are discussed. The efficacy of pure compounds isolated from the most effective plant extracts and - when available - their mechanism of action, as well as the impact on non-target species, is also covered. These belong to the following class of secondary metabolites: alkaloids, alkamides, sesquiterpenes, triterpenes, sterols, flavonoids, coumarins, anthraquinones, xanthones, acetogenonins and aliphatics. Their mode of action on mosquito larvae ranges from neurotoxic effects to inhibition of detoxificant enzymes and larval development and/or midugut damages. In the final section, current drawbacks as well as key challenges for future research, including technologies to synergize efficacy and improve stability - thus field performances - of the selected plant extracts, are outlined. Unfortunately, despite the huge amount of laboratory evidences about their efficacy, only a limited number of studies was aimed to validate their efficacy in the field, nor the epidemiological impact potentially arising from these vector control operations has been assessed. This strongly limits the development of commercial mosquito larvicides of botanical origin, at variance with plant-borne products developed in the latest decades to kill or repel other key arthropod species of medical and veterinary importance (e.g., ticks and lice), as well as mosquito adults. Further research on these issues is urgently needed.

Cytotoxicity of Ag, Au and Ag-Au bimetallic nanoparticles prepared using golden rod (Solidago canadensis) plant extract

Production and use of metallic nanoparticles have increased dramatically over the past few years and design of nanomaterials has been developed to minimize their toxic potencies. Traditional chemical methods of production are potentially harmful to the environment and greener methods for synthesis are being developed in order to address this. Thus far phytosynthesis have been found to yield nanomaterials of lesser toxicities, compared to materials synthesized by use of chemical methods. In this study nanoparticles were synthesized from an extract of leaves of golden rod (Solidago canadensis). Silver (Ag), gold (Au) and Ag-Au bimetallic nanoparticles (BNPs), synthesized by use of this "green" method, were evaluated for cytotoxic potency. Cytotoxicity of nanomaterials to H4IIE-luc (rat hepatoma) cells and HuTu-80 (human intestinal) cells were determined by use of the xCELLigence real time cell analyzer. Greatest concentrations (50 µg/mL) of Ag and Ag-Au bimetallic were toxic to both H4IIE-luc and HuTu-80 cells but Au nanoparticles were not toxic. BNPs exhibited the greatest toxic potency to these two types of cells and since AuNPs caused no toxicity; the Au functional portion of the bimetallic material could be assisting in uptake of particles across the cell membrane thereby increasing the toxicity.

Bacterial indoleacetic acid-induced synthesis of colloidal Ag2O nanocrystals and their biological activities

The biosynthesis and biological activity of colloidal Ag₂O nanocrystals have not been well studied, although they have potential applications in many fields. For the first time, we developed a reducing agent free, cost-effective technique for Ag₂O biosynthesis using Xanthomonas sp. P5. The optimal conditions for Ag₂O synthesis were 50 °C, pH 8, and 2.5 mM AgNO₃. Using these conditions the yield of Ag₂O obtained at 10 h was about five times higher than that obtained at 12 h under unoptimized conditions. Ag₂O was characterized by FESEM-EDS, TEM, dynamic light scattering, XRD, and UV-Visible spectroscopy. Indoleacetic acid produced by the strain P2 was involved in the synthesis of Ag₂O. Ag₂O exhibited a broad antimicrobial spectrum against several human pathogens. Furthermore, Ag₂O exhibited 1,1-diphenyl-2-picrylhydrazyl (IC₅₀ = 25.1 µg/ml) and 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonate (IC₅₀ = 16.8 µg/ml) radical scavenging activities, and inhibited collagenase (IC₅₀ = 27.9 mg/ml). Cytotoxicity of Ag₂O was tested in fibroblast cells and found to be non-toxic, demonstrating biocompatibility.

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

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

Uniform Generation of Sub-nanometer Silver Clusters in Zeolite Cages Exhibiting High Photocatalytic Activity under Visible Light

Sub-nanometer silver clusters that exhibit discrete electronic structure with molecular-like properties are highly desirable in various technologies. However, the methods for their preparation suffer from limitations related with the reproducibility and particles uniformity and/or the possibility of the scale-up. Another critical drawback is that free sub-nanometer silver clusters tend to aggregate into larger particles. In this work, a new approach that successfully overcomes the above limitations is developed. It allows, for the first time, an ultrafast preparation of sub-nanometer silver particles with high abundance, uniformity (7 Å), and stability into the cages of nanosized zeolite crystals. The new method consists of UV excitation of a water suspension of nanozeolite containing photoactive vanadate clusters in the presence of ethanol (as an electron donor) and silver precursor. The characteristic features of sub-nanometer silver particles are presented, and the mechanism of their formation is discussed. Sub-nanometer Ag clusters exhibit exceptional photocatalytic activity and selectivity in the reforming of formic acid to H₂ and CO₂ under visible light.

Bactericidal Properties of Plants-Derived Metal and Metal Oxide Nanoparticles (NPs)

Nanoparticles (NPs) are nano-sized particles (generally 1–100 nm) that can be synthesized through various methods. The wide range of physicochemical characteristics of NPs permit them to have diverse biological functions. These particles are versatile and can be adopted into various applications, particularly in biomedical field. In the past five years, NPs’ roles in biomedical applications have drawn considerable attentions, and novel NPs with improved functions and reduced toxicity are continuously increasing. Extensive studies have been carried out in evaluating antibacterial potentials of NPs. The promising antibacterial effects exhibited by NPs highlight the potential of developing them into future generation of antimicrobial agents. There are various methods to synthesize NPs, and each of the method has significant implication on the biological action of NPs. Among all synthetic methods, green technology is the least toxic biological route, which is particularly suitable for biomedical applications. This mini-review provides current update on the antibacterial effects of NPs synthesized by green technology using plants. Underlying challenges in developing NPs into future antibacterials in clinics are also discussed at the present review.

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.