Biogenically proficient synthesis and characterization of silver nanoparticles employing marine procured fungi Aspergillus brunneoviolaceus along with their antibacterial and antioxidative potency

Exploration of reducing and stabilizing phytoconstituents in Arisaema dracontium extract for the effective synthesis of Silver nanoparticles and evaluation of their antibacterial and toxicological proprties

Medicinal plants have been widely used for their antimicrobial properties against various microorganisms. Arisaema dracontium a familiar medicinal plant, was analyzed and silver nanoparticles (AgNPs) were synthesized using extracts of different parts of its shoot including leaves and stem. Further, the antimicrobial activity of different solvent extracts such as ethyl acetate, n-hexane, ethanol, methanol, and chloroform extracts were analyzed. AgNPs were prepared using aqueous silver nitrate solution and assessed their antibacterial activity against multidrug-resistant (MDR) and Non-multidrug-resistant bacteria. The characterization of AgNPs was done by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV-visible spectroscopy, Fourier Transform Infrared (FTI), and X-ray Diffraction approaches. The leaf extract contained Tannins, Flavonoids, Terpenoids, and Steroids while Alkaloids, Saponins, and Glycosides were undetected. The stem extract contained Alkaloids, Tannins, Flavonoids, Saponins, Steroids, and Glycosides while Terpenoids were not observed. The AgNPs synthesized from stem and leaf extracts in the current study had spherical shapes and ranged in size from 1 to 50 nm and 20-500 nm respectively as were visible in TEM. The leaf extract-prepared AgNPs showed significantly higher activities i.e., 27.75 mm ± 0.86 against the MDR strains as compared to the stem-derived nanoparticles i.e., 24.33 ± 0.33 by comparing the zones of inhibitions which can be attributed to the differences in their phytochemical constituents. The acute toxicity assay confirmed that no mortality was noticed when the dosage was 100 mg per kg which confirms that the confirms that the AgNPs are not toxic when used in low quantities. It is concluded that leaf extract from A. dracontium could be used against pathogenic bacteria offering economic and health benefits compared to the chemical substances.

The potential biological activities of Aspergillus luchuensis-aided green synthesis of silver nanoparticles

Biosynthetic metals have attracted global attention because of their safety, affordability, and environmental friendliness. As a consequence, the cell-free filtrate (CFF) of Dill leaf-derived endophytic fungus Aspergillus luchuensis was employed for the extracellularly synthesis silver nanoparticles (AgNPs). A reddish-brown color shift confirmed that AgNPs were successfully produced. The obtained AgNPs were characterized by UV-Vis (ultraviolet-visible spectroscopy), Transmission electron microscopy (TEM), FTIR, EDX, and zeta potential. Results demonstrated the creation of crystalline AgNPs with a spherical shape at 427.81 nm in the UV-Vis spectrum, and size ranged from 16 to 18 nm as observed by TEM. Additionally, the biogenic AgNPs had a promising antibacterial activity versus multidrug-resistant bacteria, notably, S. aureus, E. coli, and S. typhi. The highest growth reduction was recorded in the case of E. coli. Furthermore, the biosynthesized AgNPs demonstrated potent antifungal potential versus a variety of harmful fungi. The maximum growth inhibition was evaluated from A. brasinsilles, followed by C. albicans as compared to cell-free extract and AgNO3. In addition, data revealed that AgNPs possess powerful antioxidant activity, and their ability to scavenge radicals increased from 33.0 to 85.1% with an increment in their concentration from 3.9 to 1,000 μg/mL. Furthermore, data showed that AgNPs displayed high catalytic activity of safranin under light irradiation. The maximum decolorization percentage (100%) was observed after 6 h. Besides, the biosynthesized AgNPs showed high insecticidal potential against 3rd larval instar of Culex pipiens. Taken together, data suggested that endophytic fungus, A. luchuensis, is an attractive candidate as an environmentally sustainable and friendly fungal nanofactory.

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.

Biosynthesis of Silver Nanoparticles and Exploring Their Potential of Reducing the Contamination of the In Vitro Culture Media and Inducing the Callus Growth of Rumex nervosus Explants

Among biological methods, green synthesis of the nanomaterials using plant extracts was shown to be an environmentally friendly, economical, and simple approach. In the current study, the biogenic synthesis of silver nanoparticles (AgNPs) was achieved using the leaf extract of Hibiscus tiliaceus, in order to prevent the contamination of the tissue culture media and induce callus growth. The nanostructures of the fabricated AgNPs were characterized using UV-visible spectroscopy, Fourier transform infra-red spectra (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), zeta size, and zeta potential techniques. Our results indicate that The UV-vis spectrum of AgNPs exhibited an absorption band at 415 nm. The FTIR analysis identified the functional groups which could involve in the reduction of silver ions to AgNPs, this was also confirmed by the (hkl) diffraction peaks in the XRD diffractogram. Moreover, the TEM analysis showed a spherical nanoparticle with a size ranging from 21 and 26 nm. Thereafter, the potential antibacterial and antifungal activity of the biogenic AgNPs was evaluated against Bacillus pumilus and Alternaria alternata which were isolated from the in vitro culture media and identified based on 16S rDNA and ITS rDNA sequences, respectively. The results showed that the AgNPs significantly inhibited the growth of Alternaria alternata and Bacillus pumilus at all applied concentrations (5, 10, 20 and 40 mg/L). Compared to the control more fungal radial growth reduction (42.59%,) and bacterial inhibition (98.12%) were registered in the plates containing high doses of AgNPs (40 mg/L). Using Rumex nervosus explants, the biosynthesized AgNPs were tested for their impact to promote callus growth. The obtained results showed a significant effect of AgNPs on callus fresh weight at all applied doses. Moreover, AgNPs treatments showed a polymorphism of 12.5% which was detected by RAPD markers. In summary, the results revealed that AgNPs (40 mg/L) can be effectively added to the in vitro culture media for reducing microbial contamination and improving callus growth while greatly maintaining its genetic stability.

Mycosynthesis of Zinc Oxide Nanoparticles Exhibits Fungal Species Dependent Morphological Preference

Filamentous fungi can synthesize a variety of nanoparticles (NPs), a process referred to as mycosynthesis that requires little energy input, do not require the use of harsh chemicals, occurs at near neutral pH, and do not produce toxic byproducts. While NP synthesis involves reactions between metal ions and exudates produced by the fungi, the chemical and biochemical parameters underlying this process remain poorly understood. Here, the role of fungal species and precursor salt on the mycosynthesis of zinc oxide (ZnO) NPs is investigated. This data demonstrates that all five fungal species tested are able to produce ZnO structures that can be morphologically classified into i) well-defined NPs, ii) coalesced/dissolving NPs, and iii) micron-sized square plates. Further, species-dependent preferences for these morphologies are observed, suggesting potential differences in the profile or concentration of the biochemical constituents in their individual exudates. This data also demonstrates that mycosynthesis of ZnO NPs is independent of the anion species, with nitrate, sulfate, and chloride showing no effect on NP production. These results enhance the understanding of factors controlling the mycosynthesis of ceramic NPs, supporting future studies that can enable control over the physical and chemical properties of NPs formed through this "green" synthesis method.

Novel biosynthesis of MnO NPs using Mycoendophyte: industrial bioprocessing strategies and scaling-up production with its evaluation as anti-phytopathogenic agents

This report provides the first description of the myco-synthesis of rod-shaped MnO NPs with an average crystallite size of ~ 35 nm, employing extracellular bioactive metabolites of endophytic Trichoderma virens strain EG92 as capping/reducing agents and MnCl₂·4H₂O as a parent component. The wheat bran medium was chosen to grow endophytic strain EG92, which produced a variety of bioactive metabolites in extracellular fraction, which increases the yield of MnO NPs to 9.53 g/l. The whole medium and fungal growth conditions that influenced biomass generation were optimized as successive statistical optimization approaches (Plackett-Burman and Box-Behnken designs). The production improvements were achieved at pH 5.5, WBE (35%), and inoculum size (10%), which increased X_max to twelve-folds (89.63 g/l); thereby, P_max increased to eight-folds (82.93 g/l). After 162 h, X_max (145.63 g/l) and P_max (99.52 g/l) on the side of µ_max and Y_X/S were determined as 0.084 and 7.65, respectively. Via Taguchi experimental design, fungus-fabricated MnO NPs reaction was improved by adding 0.25 M of MnCl₂·4H₂O to 100% of fungal extract (reducing/capping agents) and adjusting the reaction pH adjusted to ~ 5. This reaction was incubated at 60 °C for 5 h before adding 20% fungal extract (stabilizing agent). Also, P_max was raised 40-fold (395.36 g/l) over the BC. Our myco-synthesized MnO NPs exhibit faster and more precise antagonistic actions against phytopathogenic bacteria than fungi; they could be employed as an alternative and promised nano-bio-pesticide to manage a variety of different types of disease-pathogens in the future.

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.

Green-Based Approach to Synthesize Silver Nanoparticles Using the Fungal Endophyte Penicillium oxalicum and Their Antimicrobial, Antioxidant, and In Vitro Anticancer Potential

A green-based approach for the synthesis of silver nanoparticles has gained tremendous attention in biomedical applications. Fungal endophytes have been recognized as a remarkable biological source for the synthesis of potential nanodrugs. The present study focuses on the fabrication of silver nanoparticles using the fungal endophyte Penicillium oxalicum (POAgNPs) associated with the leaf of the Amoora rohituka plant. Sharp UV-visible spectra at 420 nm appeared due to the surface plasmon resonance of POAgNPs and the reduction of silver salt. FT-IR analysis revealed the presence of functional groups of bioactive compounds of P. oxalicum responsible for the reduction of silver salt and validated the synthesis of POAgNPs. A high degree of crystallinity was revealed through XRD analysis, and microscopy-based characterizations such as AFM, TEM, and FESEM showed uniformly distributed, and spherically shaped nanoparticles. Furthermore, POAgNPs showed a potential inhibitory effect against bacterial and fungal strains of pathogenic nature. POAgNPs also exhibited potential antioxidant activity against the synthetically generated free radicals such as DPPH, superoxide, hydroxyl, and nitric oxide with EC50 values of 9.034 ± 0.449, 56.378 ± 1.137, 34.094 ± 1.944, and 61.219 ± 0.69 μg/mL, respectively. Moreover, POAgNPs exhibited cytotoxic potential against the breast cancer cell lines, MDA-MB-231 and MCF-7 with IC50 values of 20.080 ± 0.761 and 40.038 ± 1.022 μg/mL, respectively. POAgNPs showed anticancer potential through inhibition of wound closure and by altering the nuclear morphology of MDA-MB-231 and MCF-7 cells. Further anticancer activity revealed that POAgNPs induced apoptosis in MDA-MB-231 and MCF-7 cells by differential expression of genes related to apoptosis, tumor suppression, and cell cycle arrest and increased the level of Caspase-3. The novel study showed that P. oxalicum-mediated silver nanoparticles exhibit potential biological activity, which can be exploited as nanodrugs in clinical applications.

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.

Biosynthesis of Silver Nanoparticles at Various pH values and their Applications in Capturing Irradiation Solar Energy

BACKGROUND

Metallic nanoparticles (NPs), in general, are able, due to the high surface area per unit volume, to absorb the maximum incoming light flux through the vicinity of plasmonic structures and then provide local heating. Thus, silver (Ag) NPs has been used to generate heat and increase the temperature of water from solar radiation energy. The optimal plasmonic heating generation can be obtained as soon as the wavelength of the light source is close to the plasmonic resonance wavelength of Ag NPs.

OBJECTIVE

Ag NPs have been fabricated through a straightforward, cheap, as well as environmentally friendly approach. In this study, Salix babylonica L., weeping willow leaf extract has been utilized as a reducing, capping, and stabilizing agent, without using any other toxic materials. The importance of this study lies in the generation of hot electrons, which can be obtained by collecting the solar spectrum near the infrared and infrared regions, which cannot be obtained by the conventional photocatalytic devices.

METHODS

Numerous characterization techniques such as; UV-Vis, FT-IR spectroscopy, X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis were used to study the optical, chemical, structural, morphological, properties of the Ag NPs.

RESULTS

The impact of pH on the properties of Ag NPs and their performance to generate heat during solar irradiation have been investigated intensively. This study showed that the synthesized Ag NPs with pH value 12 is the optimum condition and can increase the temperature of water dramatically.

CONCLUSION

An evaluation of the current patents displays that the field of green synthesis Ag NPs utilizing plant extracts is a vital field and produces rather stable, safe and effective Ag NPs. The novelty of this patent is that Ag NPs can be synthesized from a one-pot reaction without using any exterior stabilizing and reducing agent, which is not conceivable by means of the existing processes. This study, also, is rare and distinctive, and it demonstrates that even a slight quantity of the Ag NPs is significantly raising the temperature of water effectively.

Biogenesis and characterization of proficient silver nanoparticles employing marine procured fungi Hamigera pallida and assessment of their antioxidative, antimicrobial and anticancer potency

OBJECTIVE

To assess the anticancer potential of biosynthesized silver nanoparticles using marine derived fungi Hamigera pallida with their antibacterial and antioxidant activities.

RESULTS

The biosynthesis of silver nanoparticles (AgNPs) was assessed by the change in color from bright yellow to dark brown. UV-Visible spectroscopy revealed its stability at 429 nm; ATR-FTIR spectroscopy revealed the functional group responsible for its production; X-Ray Diffraction revealed its crystalline FCC structure resembling the peaks in the XRD pattern, corresponding to (110), (111), (200), and (311) planes; TEM imaging revealed its spherical morphology with an average particle size of 5.85 ± 0.84 nm ranging from 3.69 to 16.11 nm and Tauc's plot analysis revealed a band gap energy of 2.22 eV, revealing aptitude of AgNPs as a semiconductors. The subsequent characterization results revealed the effective synthesis of silver nanoparticles. The biosynthesized AgNPs were found to have significant antimicrobial effect against three Gram-positive and three Gram-negative bacteria. They also demonstrated higher antioxidative potential by demonstrating strong radical scavenging activity against DPPH (2, 2-diphenyl-1-picrylhydrazyl). AgNPs showed highest anticancer activity (62.69 ± 1.73%) against human breast cancer (MCF-7) cell line at 100 µg/mL with the IC₅₀ value of 66.07 ± 2.17 µg/mL.

CONCLUSIONS

This study revealed the prospect for further utilization of AgNPs by Cell free filtrate of Hamigera pallida as an antibacterial, antioxidative and anticancer agents.

Synergistic Antibacterial Activity of Green Synthesized Silver Nanomaterials with Colistin Antibiotic against Multidrug-Resistant Bacterial Pathogens

The high frequency of nosocomial bacterial infections caused by multidrug-resistant pathogens contributes to significant morbidity and mortality worldwide. As a result, finding effective antibacterial agents is of critical importance. Hence, the aim of the present study was to greenly synthesize silver nanoparticles (AgNPs) utilizing Salvia officinalis aqueous leaf extract. The biogenic AgNPs were characterized utilizing different physicochemical techniques such as energy-dispersive X-ray spectroscopy (EDX), ultraviolet-visible spectrophotometry (UV-Vis), X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) analysis. Additionally, the synergistic antimicrobial effectiveness of the biosynthesized AgNPs with colistin antibiotic against multidrug-resistant bacterial strains was evaluated utilizing the standard disk diffusion assay. The bioformulated AgNPs revealed significant physicochemical features, such as a small particle size of 17.615 ± 1.24 nm and net zeta potential value of −16.2 mV. The elemental mapping of AgNPs revealed that silver was the main element, recording a relative mass percent of 83.16%, followed by carbon (9.51%), oxygen (5.80%), silicon (0.87%), and chloride (0.67%). The disc diffusion assay revealed that AgNPs showed antibacterial potency against different tested bacterial pathogens, recording the highest efficiency against the Escherichia coli strain with an inhibitory zone diameter of 37.86 ± 0.21 mm at an AgNPs concentration of 100 µg/disk. In addition, the antibacterial activity of AgNPs was significantly higher than that of colistin (p ≤ 0.05) against the multidrug resistant bacterial strain namely, Acinetobacter baumannii. The biosynthesized AgNPs revealed synergistic antibacterial activity with colistin antibiotic, demonstrating the highest synergistic percent against the A. baumannii strain (85.57%) followed by Enterobacter cloacae (53.63%), E. coli (35.76%), Klebsiella pneumoniae (35.19%), Salmonella typhimurium (33.06%), and Pseudomonas aeruginosa (13.75%). In conclusion, the biogenic AgNPs revealed unique physicochemical characteristics and significant antibacterial activities against different multidrug-resistant bacterial pathogens. Consequently, the potent synergistic effect of the AgNPs–colistin combination highlights the potential of utilizing this combination for fabrication of highly effective antibacterial coatings in intensive care units for successful control of the spread of nosocomial bacterial infections.

Polyphenol-Capped Biogenic Synthesis of Noble Metallic Silver Nanoparticles for Antifungal Activity against Candida auris

In terms of reduced toxicity, the biologically inspired green synthesis of nanoparticles has emerged as a promising alternative to chemically fabricated nanoparticles. The use of a highly stable, biocompatible, and environmentally friendly aqueous extract of Cynara cardunculus as a reducing and capping agent in this study demonstrated the possibility of green manufacturing of silver nanoparticles (CC-AgNPs). UV-visible spectroscopy validated the development of CC-AgNPs, indicating the surface plasmon resonance (SPR) λ_max band at 438 nm. The band gap of CC-AgNPs was found to be 2.26 eV. SEM and TEM analysis examined the surface morphology of CC-AgNPs, and micrographs revealed that the nanoparticles were spherical. The crystallinity, crystallite size, and phase purity of as-prepared nanoparticles were confirmed using XRD analysis, and it was confirmed that the CC-AgNPs were a face-centered cubic (fcc) crystalline-structured material. Furthermore, the role of active functional groups involved in the reduction and surface capping of CC-AgNPs was revealed using the Fourier transform infrared (FTIR) spectroscopic technique. CC-AgNPs were mostly spherical and monodispersed, with an average size of 26.89 nm, and were shown to be stable for a longer period without any noticeable change at room temperature. Further, we checked the antifungal mechanism of CC-AgNPs against C. auris MRL6057. The minimum inhibitory concentrations (MIC) and minimum fungicidal concentrations (MFC) were 50.0 µg/mL and 100.0 µg/mL respectively. The cell count and viability assay confirmed the fungicidal potential of CC-AgNPs. Further, the analysis showed that CC-AgNPs could induce apoptosis and G2/M phase cell cycle arrest in C. auris MRL6057. Our results also suggest that the CC-AgNPs were responsible for the induction of mitochondrial toxicity. TUNEL assay results revealed that higher concentrations of CC-AgNPs could cause DNA fragmentation. Therefore, the present study suggested that CC-AgNPs hold the capacity for antifungal drug development against C. auris infections.

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.

Molecular Weight Identification of Compounds Involved in the Fungal Synthesis of AgNPs: Effect on Antimicrobial and Photocatalytic Activity

The biological synthesis of silver nanoparticles (AgNPs) for medical, environmental, and industrial applications is considered an alternative to chemical synthesis methods. Additionally, the reducing, capping, and stabilizing molecules produced by the organisms can play a key role in the further activity of AgNPs. In this work, we evaluated the synthesis of AgNPs by four molecular weight fractions (S1: <10 kDa, S2: 10 to 30 kDa, S3: 30 to 50 kDa, and S4: >50 kDa) of mycelia-free aqueous extract produced by the white-rot fungus Stereum hirsutum and their effect on the antimicrobial activity against Pseudomonas syringae and photocatalytic decolorization of nine synthetic dyes exposed to sunlight radiation. All synthesis assay fractions showed the characteristic surface plasmon resonance (SPR) with 403 to 421 nm peaks. TEM analysis of synthesized AgNPs showed different sizes: the whole mycelia-free extracts S0 (13.8 nm), S1 (9.06 nm), S2 (10.47 nm), S3 (22.48 nm), and S4 (16.92 nm) fractions. The results of disk diffusion assays showed an inverse relation between antimicrobial activity and the molecular weight of compounds present in the mycelia-free aqueous extract used to synthesize AgNPs. The AgNPs synthesized by S0 (14.3 mm) and S1(14.2 mm) generated the highest inhibition diameter of P. syringae growth. By contrast, in the photocatalytic assays, the AgNPs synthesized by the S2 fraction showed the highest discoloration in all the dyes tested, reaching 100% of the discoloration of basic dyes after 2 h of sunlight exposure. The maximum discoloration observed in reactive and acid dyes was 53.2% and 65.3%, respectively. This differentiation in the antimicrobial and photocatalytic activity of AgNPs could be attributed to the capping effect of the molecules present in the extract fractions. Therefore, the molecular separation of synthesis extract enables the specific activities of the AgNPs to be enhanced.

Green approaches for the synthesis of metal and metal oxide nanoparticles using microbial and plant extracts

Green synthesis approaches are gaining significance as promising routes for the sustainable preparation of nanoparticles, offering reduced toxicity towards living organisms and the environment. Nanomaterials produced by green synthesis approaches can offer additional benefits, including reduced energy inputs and lower production costs than traditional synthesis, which bodes well for commercial-scale production. The biomolecules and phytochemicals extracted from microbes and plants, respectively, are active compounds that function as reducing and stabilizing agents for the green synthesis of nanoparticles. Microorganisms, such as bacteria, yeasts, fungi, and algae, have been used in nanomaterials' biological synthesis for some time. Furthermore, the use of plants or plant extracts for metal and metal-based hybrid nanoparticle synthesis represents a novel green synthesis approach that has attracted significant research interest. This review discusses various biosynthesis approaches via microbes and plants for the green preparation of metal and metal oxide nanoparticles and provides insights into the molecular aspects of the synthesis mechanisms and biomedical applications. The use of agriculture waste as a potential bioresource for nanoparticle synthesis and biomedical applications of biosynthesized nanoparticles is also discussed.

Green approaches for the synthesis of metal and metal oxide nanoparticles using microbial and plant extracts

Green synthesis approaches are gaining significance as promising routes for the sustainable preparation of nanoparticles, offering reduced toxicity towards living organisms and the environment.

Marine organisms: Pioneer natural sources of polysaccharides/proteins for green synthesis of nanoparticles and their potential applications

Current innovations in the marine bionanotechnology arena are supporting and stimulating developments in other fields, including nanomedicine, pharmaceuticals, sensors, environmental trends, food, and agriculture aspects. Many oceanic creatures, particularly algae, plants, bacteria, yeast, fungi, cyanobacteria, actinomyces, invertebrates, animals and sponges can survive under extreme circumstances. They can biogenerate a broad spectrum of phytochemicals/metabolites, including proteins, peptides, alkaloids, flavonoids, polyphenols, carbohydrate polymers, polysaccharides, sulfated polysaccharides, polysaccharide-protein complexes such as carrageenan, fucoidanase, fucoidan, carboxymethyl cellulose, poly-γ-glutamic acid, sugar residues with proteins, melanin, haemocyanin, etc). These products exhibit exclusive advantages that offer pioneering roles in the eco-friendly fabrication of several nanoparticles (NPs) i.e., Ag, Au, Ru, Fe₂O₃, Cobalt (III) Oxide (Co₂O₃), ZnO and Ag@AgCl within a single phase. Importantly, marine organisms can biosynthesize NPs in two modes, namely extracellular and intracellular. Biosynthesized NPs can be characterized using various methodologies among them, ultraviolet-visible spectroscopy, fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Taken together, this review focuses on the green synthesis of metallic, metallic oxides and nonmetallic NPs utilizing extracts/derivatives from marine organisms based on eco-friendly green biogenic procedures. Moreover, significant attention is given to the medicinal and industrial importance of such marine organisms mediated NPs.

Biosynthesis of Silver Nanoparticles and Their Applications in Harvesting Sunlight for Solar Thermal Generation

Silver (Ag) nanoparticles (NPs) have been synthesized through an easy, inexpensive, and ecofriendly method. Petroselinum crispum, parsley, leaf extract was utilized as a reducing, capping, and stabilizing agent, without using any hazardous chemical materials, for producing Ag NPs. The biosynthesized Ag NPs were characterized using different characterization techniques, namely UV-Vis, FT-IR spectroscopy, X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), dynamic light scattering (DLS), zeta potential, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), transmission electron microscope (TEM), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) analysis to investigate the optical, thermal, structural, morphological, and chemical properties of the plant extract and the biosynthesized Ag NPs. After that, the biosynthesized Ag NPs were utilized in harvesting sunlight for solar thermal generation. Surface plasmon resonance (SPR) for the green synthesized Ag NPs with the dark color were adjusted at nearly 450 nm. Once the Ag NPs are excited at the SPR, a large amount of heat is released, which causes a change in the local refractive index surrounding the Ag NPs. The released heat from the Ag NPs under the solar irradiation at the precise wavelength of plasmon resonance significantly increased the temperature of the aqueous medium. Different percentages of Ag NPs were dispersed in water and then exposed to the sunlight to monitor the temperature of the suspension. It was found that the temperature of the aqueous medium reached its highest point when 0.3 wt. % of Ag NPs was utilized. This investigation is rare and unique, and it shows that utilizing a small amount of the biosynthesized Ag NPs can increase the temperature of the aqueous medium remarkably.

Efficient biodegradation of Congo red dye using fungal consortium incorporated with Penicillium oxalicum and Aspergillus tubingensis

A novel approach had been carried out to develop fungal consortium, namely, RH-2, containing two marine procured fungal isolates in order to evaluate biodegradation of recalcitrant diazo dye Congo red. The fungi were isolated from the seacoast of Diu, India. According to the ITS sequencing, the strains were identified as Penicillium oxalicum (DS-2) and Aspergillus tubingensis (DS-4). Discs of 12 mm were cut out from the edge of both the fungal isolates (DS-2 and DS-4) and inoculated in flasks consisting of potato dextrose broth with 100 mg/L Congo red for the development of fungal consortium RH-2. The degradation by the fungal consortium RH-2 was more effective than the fungal monocultures DS-2 and DS-4 with the respective degradation reaching 97.15 ± 0.15%, 68.96 ± 0.09%, and 29.96 ± 0.21% in addition of yeast extract (1% w/v) within 12 h. The influence of dextrose (1% w/v), yeast extract (1% w/v), pH 5, and salt concentration (1% w/v) enhanced the degradation potential of fungal consortium RH-2. The maximal degradation was correlated with the production of laccase (12.498 ± 0.21 U/mL) and manganese peroxidase (10.314 ± 0.25 U/mL). The catabolism of Congo red was confirmed by UV-Visible spectroscopic analysis (Congo red λ-max = 499 nm) and ATR-FTIR spectroscopic analysis. The filtrates obtained after Congo red degradation were also evaluated for microbial toxicity against bacteria (Bacillus haynesii) and phytotoxicity analysis on plant seed (Trigonella foenum) which revealed that the filtrate acquired after the treatment of Congo red by fungal consortium RH-2 was less toxic than the original dye in nature. A novel aspect is determined by the evidence of mutualistic interaction between two different fungi for the rapid decolorization and degradation of dye providing a prospective of utilizing the developed consortium RH-2 as a cost-effective approach in textile wastewater treatment for cleaner environment.

Au@Ag Core@Shell Nanoparticles Synthesized with Rumex hymenosepalus as Antimicrobial Agent

In this work, we used a sequential method of synthesis for gold-silver bimetallic nanoparticles with core@shell structure (Au@AgNPs). Rumex hymenosepalus root extract (Rh), which presents high content in catechins and stilbenes, was used as reductor agent in nanoparticles synthesis. Size distribution obtained by Transmission Electron Microscopy (TEM) gives a mean diameter of 36 ± 11 nm for Au@AgNPs, 24 ± 4 nm for gold nanoparticles (AuNPs), and 13 ± 3 nm for silver nanoparticles (AgNPs). The geometrical shapes of NPs were principally quasi-spherical. The thickness of the silver shell over AuNPs is around 6 nm and covered by active biomolecules onto the surface. Nanoparticles characterization included high angle annular dark field images (HAADF) recorded with a scanning transmission electron microscope (STEM), Energy-Dispersive X-ray Spectroscopy (EDS), X-Ray Diffraction (XRD), UV-Vis Spectroscopy, Zeta Potential, and Dynamic Light Scattering (DLS). Fourier Transform Infrared Spectrometer (FTIR), and X-ray Photoelectron Spectroscopy (XPS) show that nanoparticles are stabilized by extract molecules. A growth kinetics study was performed using the Gompertz model for microorganisms exposed to nanomaterials. The results indicate that AgNPs and Au@AgNPs affect the lag phase and growth rate of Escherichia coli and Candida albicans in a dose-dependent manner, with a better response for Au@AgNPs.