Biosynthesis of Silver Nanoparticles by Aspergillus terreus: Characterization, Optimization, and Biological Activities

Silver secnidazole nano-hybrid emulsion-based probiotics as a novel antifungal formula against multidrug-resistant vaginal pathogens

This study presents a novel approach to manage vaginal infections due to Candidiasis, utilizing a novel silver secnidazole nano-hybrid emulsion (Ag-Secn-NHE)-based probiotics and free Ag-Secn-NHE. Ag-Secn-NHE was prepared by simple homogenization‒ultrasonication technique and validated by using a ultraviolet‒visible scan, dynamic light scattering, transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, and zeta potential. Saccharomyces cerevisiae (RCMB 002Y001) is the most effective probiotic-producing organism that demonstrates significant effects when combined with Ag-Secn-NHE. Ag-Secn-NHE-based probiotics showed significant antifungal effect compared to free Ag-Secn-NHE, silver nitrate, silver nanoparticles, secnidazole, secnidazole nanoemulsion, and commercial vaginal wash against multidrug-resistant vaginal pathogens. The highest inhibitory effect was achieved with Ag-Secn-NHE-based probiotic against Candida auris, Candida albicans, and Cryptococcus neoformans with minimal inhibitory concentration (MIC) 0.625 ± 0.002, 0.00625:1.25 ± 0.012 and 0.00625:1.25 ± 0.032 mg/mL, respectively, in comparison with Ag-Secn-NHE that show MIC at 0.00625:1.25 ± 0.612, 0.0125:2.5 ± 0.812, and 0.0125:2.5 ± 0.112 mg/mL (Ag:Secn). Ag-Secn-NHE-based- probiotic show minimum fungicidal concentration (MFC) at range from 2.5 to 20 mg/mL, wherever free Ag-Secn-NHE show MFC range from 5 to >20 mg/mL. Additionally, Ag-Secn-NHE-based probiotics have 75% inhibition of biofilm formation against C. auris and 60% inhibition of biofilm formation against both Cryptococcus neoformans and C. albicans in comparison with free Ag-Secn-NHE. Time-kill curves showed that the antifungal effect of Ag-Secn-NHE-based probiotics was fungistatic at 2MIC value after 4 h and after 16 h for Ag-Secn-NHE. TEM photographs showed that C. auris cells treated with Ag-Secn-NHE-based probiotic formula revealed severe deformations and distored ultrastructural changes. furthermore, results indicated that the Gamma radiation up to 15 kGy increases production of Ag-Secn-NHE in comparison with non-irradiated one.

Green synthesis of silver nanoparticles from the endophytic fungus Panax notoginseng and their antioxidant and antimicrobial activities and effects on cherry tomato preservation

This study investigated endophytic fungi isolated from the medicinal plant Panax notoginseng. Among these, the endophytic fungus SQ3, identified as Chaetomium globosum, was capable of reducing silver ions to form metallic silver nanoparticles. The green-synthesized silver nanoparticles (AgNPs) presented a distinct surface plasmon resonance peak at 424 nm, with particle sizes between 2.92 and 31.34 nm, indicating strong antioxidant activity. In vitro assessments demonstrated that AgNPs exhibited significant antifungal activity against Phytophthora infestans, Botrytis cinerea, and Helminthosporium maydis. AgNPs produced inhibition zones measuring 17.5 mm, 15.2 mm, and 13.4 mm against Staphylococcus aureus, Escherichia coli, and Bacillus subtilis, respectively. When applied to cherry tomatoes, AgNP treatment effectively inhibited the growth of Botrytis cinerea, minimized weight loss, preserved fruit firmness and soluble solids content, slowed the reduction in titratable acidity, and prolonged storage life. Additionally, AgNPs suppressed the increase in malondialdehyde content and maintained increased superoxide dismutase activity. These findings highlight the potential of green biosynthetic silver nanoparticles as biological control agents, providing promising resources for developing innovative treatments against postharvest fungal infections in crops.

Advancing food safety with biogenic silver nanoparticles: Addressing antimicrobial resistance, sustainability, and commercial viability

The escalating threat of antimicrobial resistance (AMR), particularly among foodborne pathogens such as Escherichia coli, Salmonella enterica, and Listeria monocytogenes, necessitates innovative solutions beyond conventional antimicrobials. Silver nanoparticles (AgNPs) have garnered significant attention for their broad-spectrum antimicrobial efficacy, ability to target multidrug-resistant strains, and versatile applications across the food sector. This review critically examines AgNPs' integration into food safety strategies, including their roles in antimicrobial food packaging, agricultural productivity enhancement, and livestock disease mitigation. Key advancements in eco-friendly synthesis methods, leveraging algae, agricultural byproducts, and microbial systems, are highlighted as pathways to address scalability, sustainability, and cost constraints. However, the potential risks of silver bioaccumulation, environmental toxicity, and regulatory challenges present significant barriers to their widespread implementation. By reviewing cutting-edge research, this review provides a comprehensive analysis of AgNP efficacy, safety, and commercial viability, proposing a roadmap for overcoming current limitations. It calls for collaborative, interdisciplinary efforts to bridge technological, ecological, and regulatory gaps, positioning AgNPs as a transformative solution for combating AMR and ensuring global food security.

Trametes versicolor laccase-derived silver nanoparticles: Green synthesis, structural characterization and multifunctional biological properties

Isolated enzymes serve as advantageous platforms for the fabrication of nanomaterials. The objective of this study was to fabricate silver nanoparticles (AgNPs) incorporated with Trametes versicolor laccase and evaluate their diverse biological properties. The AgNPs fabricated through laccase-mediated methods were characterized using various characterization techniques including UV-visible (UV-vis) spectroscopy, Energy-dispersive X-ray (EDX) spectroscopy, Dynamic light scattering (DLS) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and Field emission scanning electron microscopy (FE-SEM). The results showed that the laccase-incorporated AgNPs were spherical in shape with a Z-average diameter of 19.40 nm and a zeta potential of -19.2 mV. The AgNPs exhibited significant dose-dependent in vitro α-amylase, urease, and DPPH free radical inhibitory activities, with maximum inhibitions of 83.49 ± 1.06 %, 68.95 ± 3.60 %, and 67.36 ± 3.40 %, respectively, at a concentration of 1000 μg mL-1. Furthermore, the intrinsic pathway-mediated anticoagulant activity of the fabricated AgNPs was confirmed through the activated partial thromboplastin time (aPTT) assay, which serves as a global coagulation assay. Additionally, the laccase-incorporated AgNPs demonstrated antibacterial properties against both standard gram-positive strains of Staphylococcus epidermidis and Streptococcus mutans, with minimum inhibitory concentration (MIC) values of 2 and 4 μg mL-1, and minimum bactericidal concentration (MBC) values of 16 and 16 μg mL-1, respectively. The dose-dependent antibacterial performance of the AgNPs against both bacterial populations was also confirmed through flow cytometry. Moreover, the AgNPs exhibited 61.53 ± 3.17 % and 63.03 ± 1.44 % biofilm degradation against S. epidermidis and S. mutans, respectively, at the maximum tested concentration (20∗MIC).

Plant assisted synthesis of silver nanoparticles using Persicaria perfoliata (L.) for antioxidant, antibacterial, and anticancer properties

Persicaria perfoliata (L.) is an herbaceous medicinal plant belonging to the Polygonaceae family. The plant is distributed in Nepal, India, Japan, China, Russia, and Korea. The present study involved the analysis of plant secondary metabolites, synthesis of silver nanoparticles (Ag NPs) using the plant, characterization, and exploration of antioxidant, antidiabetic, antibacterial, and cytotoxic activities. Among six different solvent extracts, the methanol extract displayed the highest total phenolic content (TPC) and total flavonoid content (TFC) of 68.61 ± 0.57 mg GAE/g and 40.69 ± 5.0 mg QE/g respectively. Ag NPs and hexane extract displayed the potential antioxidant activity of IC50 69.40 ± 0.13 and 144.50 ± 1.36 μg/mL in the DPPH assay. The α-amylase inhibition shown by an aqueous extract and the synthesized Ag NPs IC50 of 1188.83 ± 33.52 and 1369.30 ± 46.86 μg/mL respectively. In antibacterial activity, the highest ZOI of 16 mm was displayed by Ag NPs against Klebsiella pneumoniae followed by a ZOI of 11 mm for methanol extract against Shigella sonnei. Similarly, the lowest MIC and MBC of 0.78125 and 1.5625 mg/mL were recorded for both Ag NPs and methanol extract against Staphylococcus aureus. Aqueous extract and Ag NPs did not display significant toxicity against brine shrimp nauplii. Ag NPs displayed an IC50 of 251.86 ± 58.90 μg/mL against HeLa cell lines. Biosynthesized Ag NPs showed a distinct peak at 409 nm in UV-visible spectra. FTIR analysis revealed the involvement of different functional groups of the organic compounds present in plant extract as reducing, capping, and stabilizing agents in the synthesis of Ag NPs. XRD analysis confirmed the crystal structure of Ag NPs, whereas the average grain size of 44.28 nm was determined by FE-SEM analysis. EDX spectra established the elemental composition of Ag NPs. The present study shows the synthesized Ag NPs using plant extract impart the potential biological activities as compared to that of the crude extract.

Assessment of the Biocontrol Efficacy of Silver Nanoparticles Synthesized by Trichoderma asperellum Against Infected Hordeum vulgare L. Germination

This study investigated the biosynthesis, statistical optimization, characterization, and biocontrol activity of silver nanoparticles (AgNPs) produced by newly isolated Trichoderma sp. The Trichoderma asperellum strain TA-3N was identified based on the ITS gene sequence, together with its phenotypic characteristics (GenBank accession number: OM321439). The color change from light yellow to brown after the incubation period indicates AgNPs biosynthesis. The UV spectrum revealed a single peak with the maximum absorption at 453 nm, indicating that T. asperellum produces AgNPs effectively. A Rotatable Central Composite Design (RCCD) was used to optimize the biosynthesis of AgNPs using the aqueous mycelial-free filtrate of T. asperellum. The optimal conditions for maximum AgNPs biosynthesis (156.02 µg/mL) were predicted theoretically using the desirability function tool and verified experimentally. The highest biosynthetic produced AgNPs by T. asperellum reached 160.3 µg/mL using AgNO3 concentration of 2 mM/mL, initial pH level of 6, incubation time of 60 h, and biomass weight of 6 g/100 mL water. SEM and TEM imaging revealed uniform spherical shape particles that varied in size between 8.17 and 17.74 nm. The synthesized AgNPs have a Zeta potential value of -9.51 mV. FTIR analysis provided insights into the surface composition of AgNPs, identifying various functional groups such as N-H, -OH, C-H, C=O, and the amide I bond in proteins. Cytotoxicity and genotoxicity assays demonstrated that AgNPs in combination with T. asperellum can mitigate the toxic effects of Fusarium oxysporum on barley. This intervention markedly enhanced cell division rates and decreased chromosomal irregularities. The results indicate that AgNPs synthesized by T. asperellum show the potential as an eco-friendly and efficient method for controlling plant diseases. Further studies are necessary to investigate their possible use in the agricultural sector.

Antibacterial Efficacy and Characterization of Silver Nanoparticles Synthesized via Methanolic Extract of Fomes fomentarius L. Fr

Green synthesis employs environmentally friendly, biodegradable substances for the production of nanomaterials. This study aims to develop an innovative method for synthesizing silver nanoparticles (AgNPs) using a methanolic extract of Fomes fomentarius L. Fr. as the reducing agent and to assess the potential antibacterial properties of the resulting nanoparticles. The successful synthesis of AgNPs was confirmed through characterization techniques such as UV-visible (UV-Vis) spectrophotometry, Fourier-transform infrared spectroscopy (FT-IR), and powder X-ray diffraction (PXRD). The UV-Vis analysis revealed an absorption peak at 423 nm, while FT-IR identified key phytochemical compounds involved in the reduction process. PXRD analysis indicated a face-centered cubic (fcc) structure with prominent peaks observed at 2θ = 38°, 44.6°, 64.6°, and 78°, confirming the crystalline nature of the AgNPs, with a crystallite diameter of approximately 24 nm, consistent with TEM analysis. The synthesized AgNPs demonstrated significant antibacterial activity, particularly against S. aureus, with higher efficacy against gram-positive bacteria.

Nanotechnology and malaria: Evaluation of efficacy and toxicity of green nanoparticles and future perspectives

Malaria is a global health problem that causes 1.5-2.7 million deaths worldwide each year. Resistance to antimalarial drugs in malaria parasites and to insecticides in vectors is one of the most serious issues in the fight against this disease. Moreover, the lack of an effective vaccine against malaria is still a major problem. Recent developments in nanotechnology have resulted in new prospects for the fight against malaria, especially by obtaining metal nanoparticles (NPs) that are less toxic, highly biocompatible, environmentally friendly, and less expensive. Numerous studies have been conducted on the synthesis of green NPs using plants and microorganisms (bacteria, fungi, algae, actinomycetes, and viruses). To our knowledge, there is no literature review that compares toxicities and antimalarial effects of some of the existing metallic nanoparticles, revealing their advantages and disadvantages. Hence, the purpose of this work is to assess metal NPs obtained through various green synthesis processes, to display the worth of future malaria research and determine future strategies. Results revealed that there are very few studies on green NPs covering all stages of malaria parasites. Additionally, green metal nanoparticles have yet to be studied for their possible toxic effects on infected as well as healthy erythrocytes. Morever, the toxicities of green metal NPs obtained from various sources differed according to concentration, size, shape, synthesis method, and surface charge, indicating the necessity of optimizing the methods to be used in future studies. It was concluded that studies on the toxic properties of green nanoparticles would be very important for the future.

Untargeted metabolomics and molecular docking studies on green silver nanoparticles synthesized by Sarocladium subulatum: Exploring antibacterial and antioxidant properties

The biological synthesis of silver nanoparticles (Ag-NPs) with fungi has shown promising results in antibacterial and antioxidant properties. Fungi generate metabolites (both primary and secondary) and proteins, which aid in the formation of metal nanoparticles as reducing or capping agents. While several studies have been conducted on the biological production of Ag-NPs, the exact mechanisms still need to be clarified. In this study, Ag-NPs are synthesized greenly using an unstudied fungal strain, Sarocladium subulatum AS4D. Three silver salts were used to synthesize the Ag-NPs for the first time, optimized using a cell-free extract (CFE) strategy. Additionally, these NPs were assessed for their antimicrobial and antioxidant properties. Various spectroscopic and microscopy techniques were utilized to confirm Ag-NP formation and analyze their morphology, crystalline properties, functional groups, size, stability, and concentrations. Untargeted metabolomics and proteome disruption were employed to explore the synthesis mechanism. Computational tools were applied to predict metabolite toxicity and antibacterial activity. The study identified 40 fungal metabolites capable of reducing silver ions, with COOH and OH functional groups playing a pivotal role. The silver salt type impacted the NPs' size and stability, with sizes ranging from 40 to 52 nm and zeta potentials from -0.9 to -30.4 mV. Proteome disruption affected size and stability but not shape. Biosynthesized Ag-NPs using protein-free extracts ranged from 55 to 62 nm, and zeta potentials varied from -18 to -27 mV. Molecular docking studies and PASS results found no role for the metabolome in antibacterial activity. This suggests the antibacterial activity comes from Ag-NPs, not capping or reducing agents. Overall, the research affirmed the vital role of specific reducing metabolites in the biosynthesis of Ag-NPs, while proteins derived from biological extracts were found to solely affect their size and stability.

Penicillium polonicum-mediated green synthesis of silver nanoparticles: Unveiling antimicrobial and seed germination advancements

Silver nanoparticles (AgNPs), widely recognized for their nanoscale geometric size and unique properties, such as large specific surface area, high permeability, and high safety, were synthesized using the endophytic fungus Penicillium polonicum PG21 through a green approach. Four key synthesis factors-48 h, 45 °C, pH 9.0, and 80 mM AgNPs concentration-were optimized. Characterization via ultraviolet-visible spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction revealed the AgNPs as approximately 3-25 nm spherical particles with numerous functional groups ensuring stability. AgNPs were tested against various fungal and bacterial plant pathogens, including Botrytis cinerea (EB-1), Alternaria alternata (EB-2, EB-3), Fusarium solani (RG-1), Williamsia serinedens (SL-1), Sphingopyxis macrogoltabida (SL-2), Bacillus velezensis (SL-3), and Pseudomonas mediterranea (SL-4), causing agricultural challenges. PG21-synthesized AgNPs exhibited inhibition rates against all tested fungi, with 60 μg/mL AgNPs demonstrating optimal inhibition rates. Notably, EB-1 experienced a significant growth inhibition, reaching an inhibition rate reached of 74.22 ± 1.54%. Conversely, RG-1 exhibited the smallest inhibitory effect at 48.13 ± 0.92%. The effect of AgNPs on safflower seed germination and growth revealed notable increases in shoot length, fresh weight, stem length, and number of lateral roots-1.4, 1.4, 1.33, and 10.67 times higher than the control, respectively, at an AgNPs concentration of 80 μg/mL. In conclusion, green-synthesized AgNPs demonstrate pathogen toxicity, showcasing potential applications in disease management for industrial crops and promoting plant growth.

Plant extract preparation and green synthesis of silver nanoparticles using Swertia chirata: Characterization and antimicrobial activity against selected human pathogens

Herbal medicinal plants have been used for centuries in traditional medicine, and it is interesting to see how modern research has identified the active compounds responsible for their therapeutic effects. The green synthesis of silver nanoparticles using herbal medicinal plants, such as Swertia chirata, is particularly noteworthy due to its antimicrobial properties. In the current study, the Swertia chirata plant was collected for the first time from the region of Murree, Punjab, Pakistan. After collection, extracts were prepared in different solvents (ethanol, methanol, chloroform, and distilled water), and silver nanoparticles were synthesized by reducing silver nitrate (AgNO3). The UV-visible spectrophotometer, SEM, and EDX were used to characterize the synthesized nanoparticles in terms of their size and shape. The phytochemical analysis of crude extract was performed to determine the presence of different kinds of phytochemicals. The antibacterial activity of plant extracts and the silver nanoparticles were then assessed using the agar well diffusion method against various pathogenic bacteria. The results showed that the plant contains several phytochemicals with remarkable antioxidant potential. The antibacterial analysis revealed that silver nanoparticles and the plant extracts exhibited a significant zone of inhibition against human pathogenic bacteria (Escherichia coli, S. capitis, B. subtilis, and Pseudomonas aeruginosa) as compared to the cefixime and norfloxacin. This implies that the nanoparticles have the potential to be used in nano-medicine applications, such as drug delivery systems, as well as for their antibacterial, antifungal, and antiviral activities. Additionally, the development and application of materials and technologies at the nanometer scale opens possibilities for the creation of novel drugs and therapies. Overall, the study highlights the promising potential of herbal medicinal plants found in Murree, Punjab, Pakistan, and green-synthesized silver nanoparticles in various fields of medicine and nanotechnology.

Green Synthesis of Silver Nanoparticles Using the Cell-Free Supernatant of Haematococcus pluvialis Culture

The green synthesis of silver nanoparticles (AgNPs) using the cell-free supernatant of a Haematococcus pluvialis culture (CFS) was implemented in the current study, under illumination conditions. The reduction of Ag+ to AgNPs by the CFS could be described by a pseudo-first-order kinetic equation at the temperature range tested. A high reaction rate during synthesis and stable AgNPs were obtained at 45 °C, while an alkaline pH (pH = 11.0) and a AgNO3 aqueous solution to CFS ratio of 90:10 (v/v) proved to be the most effective conditions in AgNPs synthesis. A metal precursor (AgNO3) at the concentration range tested (1-5 mM) was the limited reactant in the synthesis process. The synthesis of AgNPs was accomplished under static and agitated conditions. Continuous stirring enhanced the rate of reaction but induced aggregation at prolonged incubation times. Zeta potential and polydispersity index measurements indicated stable AgNPs and the majority of AgNPs formation occurred in the monodisperse phase. The X-ray diffraction (XRD) pattern revealed the face-centered cubic structure of the formed AgNPs, while TEM analysis revealed that the AgNPs were of a quasi-spherical shape with a size from 30 to 50 nm. The long-term stability of the AgNPs could be achieved in darkness and at 4 °C. In addition, the synthesized nanoparticles showed antibacterial activity against Escherichia coli.

Improved production of Bacillus subtilis cholesterol oxidase by optimization of process parameters using response surface methodology

BACKGROUND

Cholesterol oxidase has numerous biomedical and industrial applications. In the current study, a new bacterial strain was isolated from sewage and was selected for its high potency for cholesterol degradation (%) and production of high cholesterol oxidase activity (U/OD600).

RESULTS

Based on the sequence of 16S rRNA gene, the bacterium was identified as Bacillus subtilis. The fermentation conditions affecting cholesterol degradation (%) and the activity of cholesterol oxidase (U/OD600) of B. subtilis were optimized through fractional factorial design (FFD) and response surface methodology (RSM). According to this sequential optimization approach, 80.152% cholesterol degradation was achieved by setting the concentrations of cholesterol, inoculum size, and magnesium sulphate at 0.05 g/l, 6%, and 0.05 g/l, respectively. Moreover, 85.461 U of cholesterol oxidase/OD600 were attained by adjusting the fermentation conditions at initial pH, 6; volume of the fermentation medium, 15 ml/flask; and concentration of cholesterol, 0.05 g/l. The optimization process improved cholesterol degradation (%) and the activity of cholesterol oxidase (U/OD600) by 139% and 154%, respectively. No cholesterol was detected in the spectroscopic analysis of the optimized fermented medium via gas chromatography-mass spectroscopy (GC-MS).

CONCLUSION

The current study provides principal information for the development of efficient production of cholesterol oxidase by B. subtilis that could be used in various applications.

Mycosynthesis of silver nanoparticles from endophytic Aspergillus flavipes AUMC 15772: ovat-statistical optimization, characterization and biological activities

BACKGROUND

Mycosynthesis of silver nanoparticles (SNPs) offers a safe, eco-friendly, and promising alternative technique for large-scale manufacturing. Our study might be the first report that uses mycelial filtrate of an endophytic fungus, Aspergillus flavipes, for SNPs production under optimal conditions as an antimicrobial agent against clinical multidrug-resistant (MDR) wound pathogens.

RESULTS

In the present study, among four different endophytic fungi isolated from leaves of Lycium shawii, the only one isolate that has the ability to mycosynthesize SNPs has been identified for the first time as Aspergillus flavipes AUMC 15772 and deposited in Genebank under the accession number OP521771. One variable at a time (OVAT) and Plackett Burman design (PBD) were conducted for enhancing the production of mycosynthesized SNPs (Myco-SNPs) through optimization using five independent variables. The overall optimal variables for increasing the mycosynthesis of SNPs from mycelial filtrate of A. flavipes as a novel endophytic fungus were a silver nitrate concentration of 2 mM, a pH of 7.0, an incubation time of 5 days, and a mycelial filtrate concentration of 30% in dark conditions. UV-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), X-ray spectroscopy (XRD), Transmission electron microscopy (TEM), and Selected-Area Electron Diffraction (SAED) patterns were used to characterize Myco-SNPs, which showed the peak of absorbance at 420 nm, and FTIR showed the bands at 3426.44, 2923.30, 1681.85, 1552.64, and 1023.02 cm-1, respectively, which illustrated the presence of polyphenols, hydroxyl, alkene, nitro compounds, and aliphatic amines, respectively. The XRD pattern revealed the formation of Myco-SNPs with good crystal quality at 2θ = 34.23° and 38.18°. The TEM image and SAED pattern show the spherical crystalline shape of Myco-SNPs with an average size of 6.9232 nm. High antibacterial activity of Myco-SNPs was recorded against MDR wound pathogens as studied by minimum inhibitory concentrations ranging from 8 to 32 µg/mL, time kill kinetics, and post-agent effects. Also, in vitro cell tests indicated that Myco-SNPs support the cell viability of human skin fibroblast cells as a nontoxic compound.

CONCLUSION

The obtained results revealed the successful production of Myco-SNPs using the mycelial filtrate of A. flavipes, which may be a promising nontoxic alternative candidate for combating MDR wound pathogens.

Hyaluronic acid production by Klebsiella pneumoniae strain H15 (OP354286) under different fermentation conditions

BACKGROUND

Hyaluronic acid (HA) has gained significant attention due to its unique physical, chemical, and biological properties, making it widely used in various industries. This study aimed to screen bacterial isolates for HA production, characterize favorable fermentation conditions, and evaluate the inhibitory effect of bacterial HA on cancer cell lines.

RESULTS

A total of 108 bacterial isolates from diverse sources were screened for HA production using HPLC, turbidimetric, and carbazole determination methods. Among the HA-producing isolates, Klebsiella pneumoniae H15 isolated from an animal feces sample, was superior in HA production. The strain was characterized based on its morphological, cultural, and biochemical characteristics. Molecular identification using 16S rDNA sequencing and phylogenetic analysis confirmed its identity. Fermentation conditions, including pH, temperature, time, and agitation rate, were optimized to maximize HA production. The basal medium, comprising sucrose (7.0%) as carbon source and combined yeast extract with peptone (1.25% each) as nitrogen substrate, favored the highest HA production at pH 8.0, for 30 h, at 30 °C, under shaking at 180 rpm. The average maximized HA concentration reached 1.5 g L-1. Furthermore, bacterial HA exhibited a significant inhibitory effect on three cancer cell lines (MCF-7, HepG-2 and HCT), with the lowest concentration ranging from 0.98-3.91 µg mL-1.

CONCLUSIONS

K. pneumoniae H15, isolated from animal feces demonstrated promising potential for HA production. The most favorable fermentation conditions led to a high HA production. The inhibitory effect of bacterial HA on cancer cell lines highlights its potential therapeutic applications. These findings contribute to a broader understanding and utilization of HA in various industries and therapeutic applications.

Current Overview of Metal Nanoparticles' Synthesis, Characterization, and Biomedical Applications, with a Focus on Silver and Gold Nanoparticles

Metal nanoparticles (NPs) have garnered considerable attention, due to their unique physicochemical properties, that render them promising candidates for various applications in medicine and industry. This article offers a comprehensive overview of the most recent advancements in the manufacturing, characterization, and biomedical utilization of metal NPs, with a primary focus on silver and gold NPs. Their potential as effective anticancer, anti-inflammatory, and antimicrobial agents, drug delivery systems, and imaging agents in the diagnosis and treatment of a variety of disorders is reviewed. Moreover, their translation to therapeutic settings, and the issue of their inclusion in clinical trials, are assessed in light of over 30 clinical investigations that concentrate on administering either silver or gold NPs in conditions ranging from nosocomial infections to different types of cancers. This paper aims not only to examine the biocompatibility of nanomaterials but also to emphasize potential challenges that may limit their safe integration into healthcare practices. More than 100 nanomedicines are currently on the market, which justifies ongoing study into the use of nanomaterials in medicine. Overall, the present review aims to highlight the potential of silver and gold NPs as innovative and effective therapeutics in the field of biomedicine, citing some of their most relevant current applications.

Fungi-mediated synthesis of nanoparticles: characterization process and agricultural applications

In the field of nanotechnology, the use of biologically active products from fungi for the reduction and synthesis of nanoparticles as an alternative to toxic chemicals has received extensive attention, due to their production of large quantities of proteins, high yields, easy handling, and the low toxicity of the residues. Fungi have become valuable tools for the manufacture of nanoparticles in comparison with other biological systems because of their enhanced growth control and diversity of metabolites, including enzymes, proteins, peptides, polysaccharides, and other macro-molecules. The ability to use different species of fungi and to perform the synthesis under different conditions enables the production of nanoparticles with different physicochemical characteristics. Fungal nanotechnology has been used to develop and offer products and services in the agricultural, medicinal, and industrial sectors. Agriculturally, it has found applications in plant disease management, crop improvement, biosensing, and the production of environmentally friendly, non-toxic pesticides and fertilizers to enhance agricultural production in general. The subject of this review is the application of fungi in the synthesis of inorganic nanoparticles, characterization, and possible applications of fungal nanoparticles in the diverse agricultural sector. The literature shows potential uses of fungi in biogenic synthesis, enabling the production of nanoparticles with different physiognomies. © 2023 Society of Chemical Industry.

Biofabrication of novel silver and zinc oxide nanoparticles from Fusarium solani IOR 825 and their potential application in agriculture as biocontrol agents of phytopathogens, and seed germination and seedling growth promoters

Introduction: Plant pathogenic microorganisms adversely affect the growth and yield of crops, which consequently leads to losses in food production. Metal-based nanoparticles (MNPs) can be a remedy to solve this problem. Methods: Novel silver nanoparticles (AgNPs) and zinc oxide nanoparticles (ZnONPs) were biosynthesized from Fusarium solani IOR 825 and characterized using Dynamic Light Scattering (DLS), Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), X-ray diffraction (XRD) and measurement of Zeta potential. Antibacterial activity of NPs was evaluated against four plant pathogenic strains by determination of the minimum inhibitory (MIC) and biocidal concentrations (MBC). Micro-broth dilution method and poisoned food technique were used to assess antifungal activity of NPs against a set of plant pathogens. Effect of nanopriming with both types of MNPs on maize seed germination and seedlings growth was evaluated at a concentration range of 1-256 μg mL-1. Results: Mycosynthesis of MNPs provided small (8.27 nm), spherical and stable (zeta potential of -17.08 mV) AgNPs with good crystallinity. Similarly, ZnONPs synthesized by using two different methods (ZnONPs(1) and ZnONPs(2)) were larger in size (117.79 and 175.12 nm, respectively) with Zeta potential at -9.39 and -21.81 mV, respectively. The FTIR spectra showed the functional groups (hydroxyl, amino, and carboxyl) of the capping molecules on the surface of MNPs. The values of MIC and MBC of AgNPs against bacteria ranged from 8 to 256 μg mL-1 and from 512 to 1024 μg mL-1, respectively. Both types of ZnONPs displayed antibacterial activity at 256-1024 μg mL-1 (MIC) and 512-2048 μg mL-1 (MBC), but in the concentration range tested, they revealed no activity against Pectobacterium carotovorum. Moreover, AgNPs and ZnONPs inhibited the mycelial growth of Alternaria alternata, Fusarium culmorum, Fusarium oxysporum, Phoma lingam, and Sclerotinia sclerotiorum. MIC and MFC values of AgNPs ranged from 16-128 and 16-2048 μg mL -1, respectively. ZnONPs showed antifungal activity with MIC and MFC values of 128-2048 μg mL-1 and 256-2048 μg mL-1, respectively. The AgNPs at a concentration of ≥32 μg mL-1 revealed sterilization effect on maize seeds while ZnONPs demonstrated stimulatory effect on seedlings growth at concentrations of ≥16 μg mL-1 by improving the fresh and dry biomass production by 24% and 18%-19%, respectively. Discussion: AgNPs and ZnONPs mycosynthesized from F. solani IOR 825 could be applied in agriculture to prevent the spread of pathogens. However, further toxicity assays should be performed before field evaluation. In view of the potential of ZnONPs to stimulate plant growth, they could be crucial in increasing crop production from the perspective of current food assurance problems.

Ganoderma lucidum-Mediated Green Synthesis of Silver Nanoparticles with Antimicrobial Activity

"Green chemistry" is a simple and easily reproductible method that provides nanoparticles characterized by better stability and good dispersion in an aqueous solution. Nanoparticles can be synthesized by algae, bacteria, fungi, and plant extracts. Ganoderma lucidum is a commonly used medicinal mushroom with distinctive biological properties, such as antibacterial, antifungal, antioxidant, anti-inflammatory, anticancer, etc. In this study, aqueous mycelial extracts of Ganoderma lucidum were used to reduce AgNO₃ to form silver nanoparticles (AgNPs). The biosynthesized nanoparticles were characterized by UV-visible spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analysis. The maximum UV absorption was obtained at 420 nm, which represents the specific surface plasmon resonance band for biosynthesized silver nanoparticles. SEM images showed particles as predominantly spherical, while FTIR spectroscopic studies illustrated the presence of functional groups that can support the reducing of ion Ag⁺ to Ag(0). XRD peaks ratified the presence of AgNPs. The antimicrobial effectiveness of synthesized nanoparticles was tested against Gram-positive and Gram-negative bacterial and yeasts strains. The silver nanoparticles were effective against pathogens, inhibiting their proliferation, and thus reducing the risk to the environment and to public health.

Exploring the biological application of Penicillium fimorum-derived silver nanoparticles: In vitro physicochemical, antifungal, biofilm inhibitory, antioxidant, anticoagulant, and thrombolytic performance

This study showed the anti-candida, biofilm inhibitory, antioxidant, anticoagulant, and thrombolytic properties of biogenic silver nanoparticles (AgNPs) fabricated by using the supernatant of Penicillium fimorum (GenBank accession number OQ568180) isolated from soil. The biogenic AgNPs were characterized by using different analytical techniques. A sharp surface plasmon resonance (SPR) peak of the colloidal AgNPs at 429.5 nm in the UV-vis spectrum confirmed the fabrication of nanosized silver particles. The broth microdilution assay confirmed the anti-candida properties of AgNPs with a minimum inhibitory concentration (MIC) of 4 μg mL^-1. In the next step, the protein and DNA leakage assays as well as reactive oxygen species (ROS) assay were performed to evaluate the possible anti-candida mechanisms of AgNPs representing an increase in the total protein and DNA of supernatant along with a climb-up in ROS levels in AgNPs-treated samples. Flow cytometry also confirmed a dose-dependent cell death in the AgNPs-treated samples. Further studies also confirmed the biofilm inhibitory performance of AgNPs against Candia albicans. The AgNPs at the concentrations of MIC and 4*MIC inhibited 79.68 ± 14.38% and 83.57 ± 3.41% of biofilm formation in C. albicans, respectively. Moreover, this study showed that the intrinsic pathway may play a significant role in the anticoagulant properties of AgNPs. In addition, the AgNPs at the concentration of 500 μg mL^-1, represented 49.27%, and 73.96 ± 2.59% thrombolytic and DPPH radical scavenging potential, respectively. Promising biological performance of AgNPs suggests these nanomaterials as a good candidate for biomedical and pharmaceutical applications.

Sedeveria pink ruby Extract-Mediated Synthesis of Gold and Silver Nanoparticles and Their Bioactivity against Livestock Pathogens and in Different Cell Lines

Biological synthesis of metal nanoparticles has a significant impact in developing sustainable technologies for human, animal, and environmental safety. In this study, we synthesized gold and silver nanoparticles (NPs) using Sedeveria pink ruby (SP) extract and characterized them using UV–visible spectrophotometry, FESEM-EDX, HR-TEM, XRD, and FT-IR spectroscopy. Furthermore, antimicrobial and antioxidant activities and cytotoxicity of the synthesized NPs were evaluated. UV–visible absorption spectra showed λmax at 531 and 410 nm, corresponding to the presence of SP gold NPs (SP-AuNPs) and SP silver NPs (SP-AgNPs). Most NPs were spherical and a few were triangular rods, measuring 5–30 and 10–40 nm, respectively. EDX elemental composition analysis revealed that SP-AuNPs and SP-AgNPs accounted for >60% and 30% of NPs, respectively. Additionally, some organic moieties were present, likely derived from various metabolites in the natural plant extract, which acted as stabilizing and reducing agents. Next, the antimicrobial activity of the NPs against pathogenic microbes was tested. SP-AgNPs showed potent antibacterial activity against Escherichia coli and Yersinia pseudotuberculosis. Moreover, at moderate and low concentrations, both NPs exhibited weak cytotoxicity in chicken fibroblasts (DF-1) and macrophages (HD11) as well as human intestinal cancer cells (HT-29). Meanwhile, at high concentrations, the NPs exhibited strong cytotoxicity in both chicken and human cell lines. Therefore, the synthesized SP-AuNPs and SP-AgNPs may act as promising materials to treat poultry diseases.

Biosynthesis of Metal and Metal Oxide Nanoparticles Using Microbial Cultures: Mechanisms, Antimicrobial Activity and Applications to Cultural Heritage

Nanoparticles (1 to 100 nm) have unique physical and chemical properties, which makes them suitable for application in a vast range of scientific and technological fields. In particular, metal nanoparticle (MNPs) research has been showing promising antimicrobial activities, paving the way for new applications. However, despite some research into their antimicrobial potential, the antimicrobial mechanisms are still not well determined. Nanoparticles' biosynthesis, using plant extracts or microorganisms, has shown promising results as green alternatives to chemical synthesis; however, the knowledge regarding the mechanisms behind it is neither abundant nor consensual. In this review, findings from studies on the antimicrobial and biosynthesis mechanisms of MNPs were compiled and evidence-based mechanisms proposed. The first revealed the importance of enzymatic disturbance by internalized metal ions, while the second illustrated the role of reducing and negatively charged molecules. Additionally, the main results from recent studies (2018-2022) on the biosynthesis of MNPs using microorganisms were summarized and analyzed, evidencing a prevalence of research on silver nanoparticles synthesized using bacteria aiming toward testing their antimicrobial potential. Finally, a synopsis of studies on MNPs applied to cultural heritage materials showed potential for their future use in preservation.

Mycosynthesis of Metal-Containing Nanoparticles-Synthesis by Ascomycetes and Basidiomycetes and Their Application

Fungi contain species with a plethora of ways of adapting to life in nature. Consequently, they produce large amounts of diverse biomolecules that can be generated on a large scale and in an affordable manner. This makes fungi an attractive alternative for many biotechnological processes. Ascomycetes and basidiomycetes are the most commonly used fungi for synthesis of metal-containing nanoparticles (NPs). The advantages of NPs created by fungi include the use of non-toxic fungus-produced biochemicals, energy efficiency, ambient temperature, pressure conditions, and the ability to control and tune the crystallinity, shape, and size of the NPs. Furthermore, the presence of biomolecules might serve a dual function as agents in NP formation and also capping that can tailor the (bio)activity of subsequent NPs. This review summarizes and reviews the synthesis of different metal, metal oxide, metal sulfide, and other metal-based NPs mediated by reactive media derived from various species. The phyla ascomycetes and basidiomycetes are presented separately. Moreover, the practical application of NP mycosynthesis, particularly in the fields of biomedicine, catalysis, biosensing, mosquito control, and precision agriculture as nanofertilizers and nanopesticides, has been studied so far. Finally, an outlook is provided, and future recommendations are proposed with an emphasis on the areas where mycosynthesized NPs have greater potential than NPs synthesized using physicochemical approaches. A deeper investigation of the mechanisms of NP formation in fungi-based media is needed, as is a focus on the transfer of NP mycosynthesis from the laboratory to large-scale production and application.

Nanomaterials in the future biotextile industry: A new cosmovision to obtain smart biotextiles

For centuries, man has dominated the development of fibers and textiles to make clothing that protects them against environmental adversities, and gradually dissimilar cultural and ethnic identity traits have been created. Our garments are composed of natural elements such as animal leather, vegetable fibers, and synthetic textiles that result in ultra-resistant and durable materials. However, the textile industry has a non-sustainable character mainly because population growth will limit the use of natural resources, such as land and water, exclusively for food. At the same time, petrochemical-derived materials will gradually be replaced by more biodegradable alternatives due to their toxic accumulation in the local environment and their contribution to global climate change. The vast inventiveness of human-being is opening the possibility of replacing our clothes by mimicking, reproducing, and scaling up nature’s biosynthetic machinery through cutting-edge biotechnological approaches. Nevertheless, the new cosmovision of biotextiles must meet two requirements: 1) the appearance and performance of the clothes should be preserved to join the current textile market demand, and at the same time, 2) new functionalities should be incorporated into our clothes to embrace the impressive technological advances occurring day to day. In this regard, nanotechnological developments will be able to provide the desired properties so that the textile industry can provide bio-based materials enhanced with nanotechnology-based intelligent functionalities. This perspective article discloses nano-biotechnological approaches to address the challenge of dressing up future societies and new material consciousness.

Entomopathogenic Fungi-Mediated AgNPs: Synthesis and Insecticidal Effect against Plutella xylostella (Lepidoptera: Plutellidae)

The insect Plutella xylostella is known worldwide to cause severe damage to brassica plantations because of its resistance against several groups of chemicals and pesticides. Efforts have been conducted to overcome the barrier of P. xylostella genetic resistance. Because of their easy production and effective insecticidal activity against different insect orders, silver nanoparticles are proposed as an alternative for agricultural pest control. The use of entomopathogenic fungi for nanoparticle production may offer additional advantages since fungal biomolecules may synergistically improve the nanoparticle's effectiveness. The present study aimed to synthesize silver nanoparticles using aqueous extracts of Beauveria bassiana, Metarhizium anisopliae, and Isaria fumosorosea isolates and to evaluate their insecticidal activity against P. xylostella, as innovative nano-ecofriendly pest control. The produced silver nanoparticles were evaluated by measuring the UV-vis spectrum and the mean particle size by dynamic light scattering (DLS). I. fumosorosea aqueous extract with 3-mM silver nitrate solution showed the most promising results (86-nm mean diameter and 0.37 of polydispersity). Scanning electron microscopy showed spherical nanoparticles and Fourier-Transform Infrared Spectroscopy revealed the presence of amine and amide groups, possibly responsible for nanoparticles' reduction and stabilization. The CL₅₀ value of 0.691 mg mL^-1 was determined at 72-h for the second-instar larvae of the P. xylostella, promoting a 78% of cumulative mortality rate after the entire larval stage. From our results, the synthesis of silver nanoparticles mediated by entomopathogenic fungi was successful in obtaining an efficient product for insect pest control. The I. fumosorosea was the most suitable isolate for the synthesis of silver nanoparticles contributing to the development of a green nanoproduct and the potential control of P. xylostella.

Biogenic silver nanoparticles as antifungal agents

In recent years, an increase in multidrug-resistant fungal strains has been observed, which, together with the limited number of clinically available antifungal agents, highlights the need for the development of new antifungal agents. Due to the proven antifungal activity of silver nanoparticles (AgNPs), there is a growing interest in their use in the treatment of fungal infections. Nanoparticles are usually synthesised through a variety of physical and chemical processes that are costly and pollute the environment. For this reason, biogenic synthesis is emerging as an environmentally friendly technology and new strategies are increasingly based on the use of biogenic AgNPs as antifungal agents for clinical use. The aim of this review is to compare the antifungal activity of different biogenic AgNPs and to summarise the current knowledge on the mechanisms of action and resistance of fungi to AgNPs. Finally, a general analysis of the toxicity of biogenic AgNPs in human and veterinary medicine is performed.

Green synthesized silver nanoparticles using Cyperus rotundus L. extract as a potential antiviral agent against infectious laryngotracheitis and infectious bronchitis viruses in chickens

Background

Infectious laryngotracheitis (ILT) and infectious bronchitis (IB) are two common respiratory diseases of poultry that inflict great economic burden on the poultry industry. Developing an effective agent against both viruses is a crucial step to decrease the economic losses. Therefore, for the first time green synthesized silver nanoparticles using Cyperus rotundus L. aqueous extract was evaluated in vitro as a potential antiviral against both viruses.

Results

Silver nanoparticles from Cyperus rotundus were characterized by the spherical shape, 11-19 nm size, and zeta potential of - 6.04 mV. The maximum nontoxic concentration (MNTC) was 50 µg mL-1 for both viruses without harmful toxicity impact. The study suggested that some of the compounds in C. rotundus extract (gallic acid, chlorogenic acid, and naringenin) or its silver nanoparticles could interact with the external envelope proteins of both viruses, and inhibiting extracellular viruses.

Conclusions

The results highlight that C. rotundus green synthesized silver nanoparticles could have antiviral activity against infectious laryngotracheitis virus (ILTV) and infectious bronchitis virus (IBV) in chickens.

Graphical Abstract

Soil Fungi as Biomediator in Silver Nanoparticles Formation and Antimicrobial Efficacy

Introduction and Objectives

Biogenic agents in nanoparticles fabrication are gaining great interest due to their lower possible negative environmental impacts. The present study aimed to isolate fungal strains from deserts in Saudi Arabia and assess their ability in silver nanoparticles (AgNPs) fabrication and evaluate their antibacterial effect.

Methods

Soil fungi were identified using 18s rDNA, and their ability in NPs fabrication was assessed as extracellular synthesis, then UV-vis spectroscopy, dynamic light scattering (DLS), energy-dispersive X-ray spectroscopy, and transmission electron microscopy were used for AgNPs characterization. The antibacterial activity of fungal-based NPs was assessed against one Gram-positive methicillin-resistant S. aureus (MRSA) and three Gram-negative bacteria (E. coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae). Ultrastructural changes caused by fungal-based NPs on K. pneumoniae were investigated using TEM along with SDS-PAGE for protein profile patterns.

Results

The three fungal isolates were identified as Phoma sp. (MN995524), Chaetomium globosum (MN995493), and Chaetomium sp. (MN995550), and their filtrate reduced Ag ions into spherical P-AgNPs, G-AgNPs, and C-AgNPs, respectively. DLS data showed an average size between 12.26 and 70.24 nm, where EDX spectrums represent Ag at 3.0 keV peak. G-AgNPs displayed strong antibacterial activities against Klebsiella pneumoniae, and the ultrastructural changes caused by NPs were noted. Additionally, SDS-PAGE analysis of treated K. pneumoniae revealed fewer bands compared to control, which could be related to protein degradation.

Conclusion

Present findings have consequently developed an eco-friendly approach in NPs formation by environmentally isolated fungal strains to yield NPs as antibacterial agents.

Superior in vivo Wound-Healing Activity of Mycosynthesized Silver Nanogel on Different Wound Models in Rat

Wound healing is a complex phenomenon particularly owing to the rise in antimicrobial resistance. This has attracted the attention of the scientific community to search for new alternative solutions. Among these, silver being antimicrobial has been used since ancient times. Considering this fact, the main goal of our study was to evaluate the wound-healing ability of mycofabricated silver nanoparticles (AgNPs). We have focused on the formulation of silver nanogel for the management of wounds in albino Wistar rats. Mycosynthesized AgNPs from Fusarium oxysporum were used for the development of novel wound-healing antimicrobial silver nanogel with different concentrations of AgNPs, i.e., 0.1, 0.5, and 1 mg g^-1. The formulated silver nanogel demonstrated excellent wound-healing activity in the incision, excision, and burn wound-healing model. In the incision wound-healing model, silver nanogel at a concentration of 0.5 mg g^-1 exhibited superior wound-healing effect, whereas in the case of excision and burn wound-healing model, silver nanogel at the concentrations of 0.1 and 1 mg g^-1 showed enhanced wound-healing effect, respectively. Moreover, silver nanogel competently arrests the bacterial growth on the wound surface and offers an improved local environment for scald wound healing. Histological studies of healed tissues and organs of the rat stated that AgNPs at less concentration (1 mg g^-1) do not show any toxic or adverse effect on the body and promote wound healing of animal tissue. Based on these studies, we concluded that the silver nanogel prepared from mycosynthesized AgNPs can be used as a promising antimicrobial wound dressing.

Proficient mycogenic synthesis of silver nanoparticles by soil derived fungus Aspergillus melleus SSS-10 with cytotoxic and antibacterial potency

The present study aimed at evaluating the extracellular synthesis of silver nanoparticles by soil fungus Aspergillus melleus SSS-10 for antibacterial and cytotoxic activity. In this study, the formation of silver nanoparticles (AgNPs) was estimated by the colour change in cell free extract from pale yellow to golden yellow after 24 h of the reaction. UV-Vis study showed the absorbance maxima at 410 nm. Tauc plot analysis revealed the band gap energy as 2.34 eV. Dynamic Light Scattering (DLS) data revealed polydisperse anisotropic silver nanoparticles with average hydrodynamic diameter of 92.006 nm. Zeta potential of - 19.6 mV provided evidence of stable silver nanoparticles. X-ray diffraction (XRD) analysis revealed four prominent Bragg peaks corresponding to (111), (200), (220) and (311) planes characteristic of silver (Ag) in FCC structural configuration. Average crystallite size was found to be 87.3 nm from Scherrer equation. Scanning Electron Microscope (SEM) analysis revealed irregular morphology of silver nanoparticles. EDS analysis displayed characteristic energy peaks of silver from 2.72 keV to 3.52 keV confirming the presence of silver nanoparticles. Biosynthesized AgNPs exhibited strong cytotoxic potential on MG-63 cells. AgNPs also showed antibacterial activity against both Staphylococcus aureus and Escherichia coli. In conclusion, this study provides a platform to explore the utility of fungal mediated silver nanoparticles synthesized for various pharmaceutical and cosmeceutical applications.

Green synthesis of silver nanoparticles using Hagenia abyssinica (Bruce) J.F. Gmel plant leaf extract and their antibacterial and anti-oxidant activities

Green synthesis of silver nanoparticles (AgNPs) was achieved by bio-reduction of silver nitrate using Hagenia Abyssinica plant leaf extract (HAPLE). The AgNPs formation was confirmed by Ultraviolet-Visible (UV-Vis) spectrophotometer. The synthesized AgNPs in solution have shown maximum absorption at 430 nm. The different parameters like temperature, pH, time, silver nitrate concentration and volume of leaf extract were optimized spectrophotometrically. The Fourier-Transform Infrared (FTIR) Spectroscopy was used to confirm the existence of various functional groups responsible for reducing and stabilizing during the biosynthesis process. The X-Ray Diffraction (XRD) analysis confirmed the structure, crystal size and nature of the AgNPs. The synthesized AgNPs showed antimicrobial (gram-negative bacteria (klebsiella pneumoniae and salmonella typhimurium) and gram-positive bacteria (Streptococcus pneumoniae)) and antioxidant (2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging method) activities. The developed method for the AgNPs synthesis using HAPLE is an eco-friendly and convenient method. In near future, the synthesized AgNPs could be used in the fields of water treatment, biomedicine, biosensor and nanotechnology.

A Novel Green Preparation of Ag/RGO Nanocomposites with Highly Effective Anticancer Performance

The efficacy of current cancer therapies is limited due to several factors, including drug resistance and non-specific toxic effects. Due to their tuneable properties, silver nanoparticles (Ag NPs) and graphene derivative-based nanomaterials are now providing new hope to treat cancer with minimum side effects. Here, we report a simple, inexpensive, and eco-friendly protocol for the preparation of silver-reduced graphene oxide nanocomposites (Ag/RGO NCs) using orange peel extract. This work was planned to curtail the use of toxic chemicals, and improve the anticancer performance and cytocompatibility of Ag/RGO NCs. Aqueous extract of orange peels is abundant in phytochemicals that act as reducing and stabilizing agents for the green synthesis of Ag NPs and Ag/RGO NCs from silver nitrate and graphene oxide (GO). Moreover, the flavonoid present in orange peel is a potent anticancer agent. Green-prepared Ag NPs and Ag/RGO NCs were characterized by UV-visible spectrophotometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and dynamic light scattering (DLS). The results of the anticancer study demonstrated that the killing potential of Ag/RGO NCs against human breast cancer (MCF7) and lung cancer (A549) cells was two-fold that of pure Ag NPs. Moreover, the cytocompatibility of Ag/RGO NCs in human normal breast epithelial (MCF10A) cells and normal lung fibroblasts (IMR90) was higher than that of pure Ag NPs. This mechanistic study indicated that Ag/RGO NCs induce toxicity in cancer cells through pro-oxidant reactive oxygen species generation and antioxidant glutathione depletion and provided a novel green synthesis of Ag/RGO NCs with highly effective anticancer performance and better cytocompatibility.

Green Synthesis of Metallic Nanoparticles: Applications and Limitations

The past decade has witnessed a phenomenal rise in nanotechnology research due to its broad range of applications in diverse fields including food safety, transportation, sustainable energy, environmental science, catalysis, and medicine. The distinctive properties of nanomaterials (nano-sized particles in the range of 1 to 100 nm) make them uniquely suitable for such wide range of functions. The nanoparticles when manufactured using green synthesis methods are especially desirable being devoid of harsh operating conditions (high temperature and pressure), hazardous chemicals, or addition of external stabilizing or capping agents. Numerous plants and microorganisms are being experimented upon for an eco–friendly, cost–effective, and biologically safe process optimization. This review provides a comprehensive overview on the green synthesis of metallic NPs using plants and microorganisms, factors affecting the synthesis, and characterization of synthesized NPs. The potential applications of metal NPs in various sectors have also been highlighted along with the major challenges involved with respect to toxicity and translational research.