Photocatalytic and Antimicrobial Activities of Biosynthesized Silver Nanoparticles Using Cytobacillus firmus

A review of microbes mediated biosynthesis of silver nanoparticles and their enhanced antimicrobial activities

In recent decades, biosynthesis of metal and (or) metal oxide nanoparticles using microbes is accepted as one of the most sustainable, cost-effective, robust, and green processes as it does not encompass the usage of largely hazardous chemicals. Accordingly, numerous simple, inexpensive, and environmentally friendly approaches for the biosynthesis of silver nanoparticles (AgNPs) were reported using microbes avoiding conventional (chemical) methods. This comprehensive review detailed an advance made in recent years in the microbes-mediated biosynthesis of AgNPs and evaluation of their antimicrobial activities covering the literature from 2015-till date. It also aimed at elaborating the possible effect of the different phytochemicals, their concentrations, extraction temperature, extraction solvent, pH, reaction time, reaction temperature, and concentration of precursor on the shape, size, and stability of the synthesized AgNPs. In addition, while trying to understand the antimicrobial activities against targeted pathogenic microbes the probable mechanism of the interaction of produced AgNPs with the cell wall of targeted microbes that led to the cell's reputed and death have also been detailed. Lastly, this review detailed the shape and size-dependent antimicrobial activities of the microbes-mediated AgNPs and their enhanced antimicrobial activities by synergetic interaction with known commercially available antibiotic drugs.

Endophytic Aspergillus hiratsukae mediated biosynthesis of silver nanoparticles and their antimicrobial and photocatalytic activities

In the current study, endophytic Aspergillus hiratsukae was used for the biosynthesis of silver nanoparticles (Ag-NPs) for the first time. The characterizations were performed using X ray diffraction (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), Dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), and UV-Vis spectroscopy. The obtained results demonstrated the successful formation of crystalline, spherical Ag-NPs with particle diameters ranging from 16 to 31 nm. The FT-IR studied and displayed the various functional groups involved, which played a role in capping and reducing agents for Ag-NPs production. The SEM-EDX revealed that the main constituent of the AS-formed sample was primarily Ag, with a weight percentage of 64.2%. The mycosynthesized Ag-NPs were assessed for antimicrobial as well as photocatalytic activities. The antimicrobial results indicated that the synthesized Ag-NPs possess notable antibacterial efficacy against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli, with minimum inhibitory concentrations (MICs) of Ag-NPs ranging from 62.5 to 250 μg/mL. Moreover, the biosynthesized Ag-NPs demonstrated weak antifungal activity against Aspergillus brasiliensis and Candida albicans, with MICs of 500 and 1,000 μg/mL, respectively. In addition, the mycosynthesized Ag-NPs exhibited photocatalytic activity toward acid black 2 (nigrosine) dye under both light and dark stimulation. Notably, After 300 min exposure to light, the nigrosine dye was degraded by 93%. In contrast, 51% degradation was observed after 300 min in darkness. In conclusion, Ag-NPs were successfully biosynthesized using endophytic A. hiratsukae and also exhibited antimicrobial and photocatalytic activities that can be used in environmental applications.

Comprehensive antifungal investigation of green synthesized silver nanoformulation against four agriculturally significant fungi and its cytotoxic applications

The present study reports the green synthesis of silver nanoparticles (AgNPs) in powder form using the leaf extract of Azadirachta indica. The synthesis of AgNPs was confirmed by UV-vis spectroscopy, FTIR, XRD, FESEM, and EDX. The synthesized AgNPs were in a powdered state and dispersed completely in 5% polyethylene glycol (PEG) and demonstrated prolonged shelf life and enhanced bioavailability over a year without any aggregation. The resulting silver nanoformulation demonstrated complete inhibition against Sclerotinia sclerotiorum and Colletotrichum falcatum and 68% to 80% inhibition against Colletotrichum gloeosporioides and Rhizoctonia solani respectively, at 2000 ppm. The EC50 values determined through a statistical analysis were 66.42, 157.7, 19.06, and 33.30 ppm for S. sclerotiorum, C. falcatum, C. gloeosporioides, and R. solani respectively. The silver nanoformulation also established significant cytotoxicity, with a 74.96% inhibition rate against the human glioblastoma cell line U87MG at 250 ppm. The IC50 value for the cancerous cell lines was determined to be 56.87 ppm through statistical analysis. The proposed silver nanoformulation may be used as a next-generation fungicide in crop improvement and may also find application in anticancer investigations. To the best of our knowledge, this is also the first report of silver nanoformulation demonstrating complete inhibition against the economically significant phytopathogen C. falcatum.

Green biosynthesis of bimetallic selenium-gold nanoparticles using Pluchea indica leaves and their biological applications

Increasing bacterial resistance and the negative impact of currently used antibacterial agents have produced the need for novel antibacterial agents and anticancer drugs. In this regard, nanotechnology could provide safer and more efficient therapeutic agents. The main methods for nanoparticle production are chemical and physical approaches that are often costly and environmentally unsafe. In the current study, Pluchea indica leaf extract was used for the biosynthesis of bimetallic selenium-gold nanoparticles (Se-Au BNPs) for the first time. Phytochemical examinations revealed that P. indica leaf extract includes 90.25 mg/g dry weight (DW) phenolics, 275.53 mg/g DW flavonoids, and 26.45 mg/g DW tannins. X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) techniques were employed to characterize Se-Au BNPs. Based on UV-vis spectra, the absorbance of Se-Au BNPs peaked at 238 and 374 nm. In SEM imaging, Se-Au BNPs emerged as bright particles, and both Au and Se were uniformly distributed throughout the P. indica leaf extract. XRD analysis revealed that the average size of Se-Au BNPs was 45.97 nm. The Se-Au BNPs showed antibacterial properties against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis, with minimum inhibitory concentrations (MICs) of 31.25, 15.62, 31.25, and 3.9 μg/mL, respectively. Surprisingly, a cytotoxicity assay revealed that the IC50 value toward the Wi 38 normal cell line was 116.8 μg/mL, implying that all of the MICs described above could be used safely. More importantly, Se-Au BNPs have shown higher anticancer efficacy against human breast cancer cells (MCF7), with an IC50 value of 13.77 μg/mL. In conclusion, this paper is the first to provide data on the effective utilization of P. indica leaf extract in the biosynthesis of biologically active Se-Au BNPs.

Green synthesis of gold and silver nanoparticles using crude extract of Aconitum violaceum and evaluation of their antibacterial, antioxidant and photocatalytic activities

Green synthesis of metal nanoparticles (NPs) has received extensive attention over other conventional approaches due to their non-toxic nature and more biocompatibility. Herein we report gold and silver NPs (AuNPs@AV and AgNPs@AV) prepared by employing a green approach using crude extract of Aconitum violaceum Jacquem. ex Stapf. The synthesized NPs were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX), X-ray Diffraction (XRD), UV/Visible spectroscopy, Fourier Transform Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Zeta Potential. Morphological analysis showed spherical and triangular shapes of the NPs with average size of <100 nm. The AuNPs@AV and AgNPs@AV exhibited effective antibacterial activities, with minimum inhibitory concentrations (MICs) of 95 and 70 μg/mL against Lactobacillus acidophilus (L. acidophilus) and 90 and 65 μg/mL against Escherichia coli (E. coli), respectively. Strong antioxidant effect of AuNPs@AV and AgNPs@AV were reported against DPPH radical and PTIO within range of IC50 values; 161-80 μg/ml as compared to the standard (23-11 μg/mL) respectively. Moreover, the AuNPs@AV and AgNPs@AV showed efficient photocatalytic activity and degraded 89.88% and 93.7% methylene blue (MB) dye under UV light, respectively.

Use of metal nanoparticles in agriculture. A review on the effects on plant germination

Agricultural nanotechnology has become a powerful tool to help crops and improve agricultural production in the context of a growing world population. However, its application can have some problems with the development of harvests, especially during germination. This review evaluates nanoparticles with essential (Cu, Fe, Ni and Zn) and non-essential (Ag and Ti) elements on plant germination. In general, the effect of nanoparticles depends on several factors (dose, treatment time, application method, type of nanoparticle and plant). In addition, pH and ionic strength are relevant when applying nanoparticles to the soil. In the case of essential element nanoparticles, Fe nanoparticles show better results in improving nutrient uptake, improving germination, and the possibility of magnetic properties could favor their use in the removal of pollutants. In the case of Cu and Zn nanoparticles, they can be beneficial at low concentrations, while their excess presents toxicity and negatively affects germination. About nanoparticles of non-essential elements, both Ti and Ag nanoparticles can be helpful for nutrient uptake. However, their potential effects depend highly on the crop type, particle size and concentration. Overall, nanotechnology in agriculture is still in its early stages of development, and more research is needed to understand potential environmental and public health impacts.

Bio-based antimicrobial food packaging films based on hydroxypropyl starch/polyvinyl alcohol loaded with the biosynthesized zinc oxide nanoparticles

In the last decades, bio-based active food packaging materials have received much attention. It is known that the utilization of traditional materials for food packaging applications lack some critical characteristics such as resistance to the harmful microbes that cause a damage to the preserved foods. Therefore, the current study aimed to find an alternative packaging films comprises an efficient biopolymers. This research work was designed to prepare film mats using hydroxypropyl starch (HPS), polyvinyl alcohol (PVA), palmitic acid (PA) and biosynthesized zinc oxide nanoparticles (ZnONPs). The fabricated films were coded as 1H, 2H, 3H and 4H based on the utilized concentration of ZnONPs. The biosynthesized ZnONPs and the bio-based films loaded with ZnONPs were characterized. The results revealed that ZnONPs exhibited nearly spherical shape and size ∼40 nm. The surface structure of the produced bioactive packaging films exhibited smooth with homogeneous features, excellent mechanical and thermal stability properties. The prepared bioactive packaging film loaded with ZnONPs (4H) exhibited superior antibacterial activity among other films against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 with inhibition zones 15.1 ± 0.76 and 12.1 ± 0.71 mm respectively. Correspondingly, packing film 4H exhibited potential antifungal activity toward Aspergillus niger RCMB 02724, A. flavus RCMB 02782, Penicillium expansum IMI 89372 and Fusarium oxysporum RCMB 001004 with inhibition zones (16 ± 1.0, 22 ± 0.90, 18.0 ± 1.1 and12.3 ± 0.57 mm respectively). Moreover, all prepared films did not show cytotoxicity on the normal cell line (Wi38) and recorded biodegradability properties that reached around 85 % after four weeks in soil. Based on these results, the antimicrobial films comprising HPS/PVA and loaded with the biosynthesized ZnONPs can be considered as a suitable film for food packaging purposes.

Dandelion flower-fabricated Ag nanoparticles versus synthetic ones with characterization and determination of photocatalytic, antioxidant, antibacterial, and α-glucosidase inhibitory activities

In the present work, Silver nanoparticles (AgNPs) were fabricated through the dandelion flower hydroalcoholic extract, and their properties were characterized by FTIR, XRD, UV visible, SEM, and EDX. The results demonstrated that the average diameter of the green fabricated AgNPs is 45-55 nm (G-AgNPs). The antioxidant, antimicrobial, antidiabetic, and photocatalytic properties of G-AgNPs were compared with two commercially available different diameter sizes (20 and 80-100 nm) of AgNPs (C-AgNPs1- and C-AgNPs2, respectively). The sample's capacity for antioxidants was evaluated by DPPH free radical scavenging method. The consequences showed that G-AgNPs have higher radical scavenging activity (47.8%) than C-AgNPs2 (39.49%) and C-AgNPs1 (33.91%). To investigate the photocatalytic property, methylene blue dye was used. The results displayed that G-AgNPs is an effective photo-catalyst compared to C-AgNPs2 and C-AgNPs1, which respectively have an inhibition potential of 75.22, 51.94, and 56.65%. Also, the antimicrobial capacity of nanoparticles was assayed against, the gram-negative Escherichia coli and gram-positive Staphylococcus aureus bacteria. The results indicated that G-AgNPs could effectively inhibit the growth of both bacteria, compared to C-AgNPs1 and C-AgNPs2. Finally, G-AgNPs exhibited a considerable α-glucosidase enzyme inhibitory effect (88.37%) in comparison with C-AgNPs1 (61.7%) and C-AgNPs2 (50.5%).

Biocontrol of bacterial seedling rot of rice plants using combination of Cytobacillus firmus JBRS159 and silicon

Burkholderia glumae causes bacterial panicle blight (BPB) and bacterial seedling rot (BSR) which are difficult to control in rice plants. Seed disinfection using microbes and eco-friendly materials is an efficient alternative practice for managing BPB and BSR. In this study, we applied Cytobacillus firmus JBRS159 (JBRS159) in combination with silicon dioxide (SiO2) nanoparticle or potassium silicate (K2SiO3) solution to control BSR. JBRS159, SiO2 nanoparticle, and K2SiO3 independently suppressed the BSR disease and promoted growths of rice and Arabidopsis. Population of B. glumae in the treated rice seeds was suppressed by the application of JBRS159 via competitions for nutrients and niches. The mixture of JBRS159 and each Si compound (SiO2 nanoparticle or K2SiO3) was complementary for disease-suppressing and growth-promoting activities of individual treatment. The results of this study indicate that mixture of JBRS159 with each Si compound can be harnessed for disease control and growth promotion as efficient alternatives to chemical pesticides and synthetic fertilizers. The efficacy of JBRS159 and Si compounds in the control of BSR and BPB in the field remains to be evaluated.

Antimicrobial, Antibiofilm, and Anticancer Activities of Syzygium aromaticum Essential Oil Nanoemulsion

In the current study, clove oil nanoemulsion (CL-nanoemulsion) and emulsion (CL-emulsion) were prepared through an ecofriendly method. The prepared CL-nanoemulsion and CL-emulsion were characterized using dynamic light scattering (DLS) and a transmission electron microscope (TEM), where results illustrated that CL-nanoemulsion droplets were approximately 32.67 nm in size and spherical in shape, while CL-nanoemulsion droplets were approximately 225.8 nm with a spherical shape. The antibacterial activity of CL-nanoemulsion and CL-emulsion was carried out using a microbroth dilution method. Results revealed that the preferred CL-nanoemulsion had minimal MIC values between 0.31 and 5 mg/mL. The antibiofilm efficacy of CL-nanoemulsion against S. aureus significantly decreased the development of biofilm compared with CL-emulsion. Furthermore, results illustrated that CL-nanoemulsion showed antifungal activity significantly higher than CL-emulsion. Moreover, the prepared CL-nanoemulsion exhibited outstanding antifungal efficiency toward Candida albicans, Cryptococcus neoformans, Aspergillus brasiliensis, A. flavus, and A. fumigatus where MICs were 12.5, 3.12, 0.78, 1.56, and 1.56 mg/mL, respectively. Additionally, the prepared CL-nanoemulsion was analyzed for its antineoplastic effects through a modified MTT assay for evaluating apoptotic and cytotoxic effects using HepG2 and MCF-7 cell lines. MCF-7 breast cancer cells showed the lowest IC50 values (3.4-fold) in CL-nanoemulsion relative to that of CL-emulsion. Thus, CL-nanoemulsion induces apoptosis in breast cancer cells by inducing caspase-8 and -9 activity and suppressing VEGFR-2. In conclusion, the prepared CL-nanoemulsion had antibacterial, antifungal, and antibiofilm as well as anticancer properties, which can be used in different biomedical applications after extensive studies in vivo.

Green Biosynthesis of Zinc Oxide Nanoparticles Using Pluchea indica Leaf Extract: Antimicrobial and Photocatalytic Activities

Nanotechnology is playing a critical role in several essential technologies with nanoscale structures (nanoparticles) in areas of the environment and biomedicine. In this work, the leaf extract of Pluchea indica was utilized to biosynthesize zinc oxide nanoparticles (ZnONPs) for the first time and evaluated for antimicrobial and photocatalytic activities. Different experimental methods were used to characterize the biosynthesized ZnONPs. The biosynthesized ZnONPs showed maximum Ultraviolet-visible spectroscopy (UV-vis) absorbance at a wavelength of 360 nm. The X-Ray diffraction (XRD) pattern of the ZnONPs exhibits seven strong reflection peaks, and the average particle size was 21.9 nm. Fourier-transform infrared spectroscopy (FT-IR) spectrum analysis reveals the presence of functional groups that help in biofabrication. The existence of Zn and O was confirmed by the Energy-dispersive X-ray (EDX) spectrum and the morphology by SEM images. Antimicrobial studies showed that the biosynthesized ZnONPs have antimicrobial efficacy against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Bacillus subtilis, Staphylococcus aureus, Candida albicans and Cryptococcus neoformans where inhibition zones at concentration 1000 µg/mL were 21.83 ± 0.76, 13.0 ± 1.1, 14.9 ± 0.85, 24.26 ± 1.1, 17.0 ± 1.0, 20.67 ± 0.57 and 19.0 ± 1.0 mm respectively. Under both dark and sunlight irradiation, the photocatalytic activity of ZnONPs was evaluated towards the degradation of the thiazine dye (methylene blue-MB). Approximately 95% of the MB dye was broken down at pH 8 after 150 min of sunlight exposure. The aforementioned results, therefore, suggest that ZnONPs synthesized by implementing environmentally friendly techniques can be employed for a variety of environmental and biomedical applications.

Biosynthesis, Characterization, and Antifungal Activity of Novel Trimetallic Copper Oxide-Selenium-Zinc Oxide Nanoparticles against Some Mucorales Fungi

Metal nanoparticles are assumed to be a new generation of biologically active materials. The integrations between more than one metal are synergetic multifunctional features. In the current study, trimetallic copper-selenium-zinc oxide nanoparticles (Tri-CSZ NPs) were successfully mycosynthesized using Aspergillus niger through an ecofriendly method for the first time. The biosynthesis of the particles was characterized using physiochemical and topographical analysis. The physiochemical analysis included Fourier transform infrared spectroscopy (FTIR), which affirmed that the biosynthesis of Tri-CSZ NPs relies on the functional groups of fungal filtrates. Additionally, the UV-visible and X-ray diffraction patterns were proposed for the formation of Tri-CSZ NPs; moreover, topography analysis confirmed that the micromorphology of the nanoparticles were similar to a stick, with ends having a tetragonal pyramid shape, and with an average nanosize of about 26.3 ± 5.4 nm. Cytotoxicity results reveled that the Tri-CSZ NPs have no cytotoxicity on the human normal cell line Wi 38 at low concentrations, where the IC50 was 521 µg/mL. Furthermore, the antifungal activity of the Tri-CSZ NPs was evaluated. The antifungal results revealed that the Tri-CSZ NPs have promising antifungal activity against Mucor racemosus, Rhizopus microsporus, Lichtheimia corymbifera, and Syncephalastrum racemosum, where the minimum inhibitory concentrations (MICs) were 1.95, 7.81, 62.5, and 3.9 µg/mL, and the minimum fungicidal concentrations (MFCs) were 250, 62.5, 125, and 1000 µg/mL, respectively. In conclusion, Tri-CSZ NPs were successfully mycosynthesized using A. niger, which have a promising antifungal activity against fungi causing mucormycosis.

Antibacterial activity of CuO-Ag Janus like nanoparticles against recombinant strain Escherichia coli

The toxic action of CuO-Ag Janus particles and a bicomponent mixture of CuO and Ag particles have been studied against a recombinant strain Escherichia coli K12 TG1 with cloned luxCDABE genes of marine bacteria Photobacterium leiognathi 54D10. An original method was used for the preparation CuO-Ag Janus like  nanoparticles by simultaneous electrical explosion of twisted Cu and Ag wires in a mixture of argon and oxygen gases. The bioluminescence inhibition on recombinant strain E. coli shows that CuO-Ag Janus NPs were effective. The concentration by 50% (EC₅₀) for CuO-Ag Janus NPs was 0.03 ± 0.001 mg/ml (p < 0.05). The bioactivity of the bicomponent mixture of CuO and Ag NPs (EC₅₀) was 0.25 ± 0.002 mg/ml (p < 0.05). The effective concentration of CuO-Ag Janus NPs against E. coli was comparatively lower than those of bicomponent mixture CuO and Ag against which explains the higher activity of CuO-Ag Janus NPs. The toxicity values of CuO and Ag as monocomponent nanoparticles were 2-32 times lower compared with the bicomponent nanoparticles. A dose-dependent inhibition of bacterial luminescence developed over time was noted. The result of contact E. coli with CuO-Ag Janus particles was 100% suppression of bacterial luminescence from the first minutes of contact occured starting with a content of 2.0 mg/ml and within the next 180 min. The effect of bioactivity prolonged in the final concentration of nanopowder (EC₁₀₀ = 0.0625 ± 0.002 mg/ml) (p < 0.05). CuO-Ag Janus particles exhibited more pronounced antibacterial activity compared to CuO, Ag nanoparticles and their mechanical mixture.

First report on isolation of Mucor bainieri from honeybees, Apis mellifera: Characterization and biological activities

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The schematic mechanism for R1234yf combustion were revealed in unimolecular lysis reactions, colliding reactions with oxygen molecules, collision reaction with active radicals (H and OH radicals).

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The new chemical reaction equations for the combustion of R1234yf were proposed.

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This paper provided an effective method to establish the combustion mechanism of flammable hydrofluoroolefins.

Fungi are potential biocontrol agents and rich sources of secondary metabolites with demonstrated biological activities. This study aimed to isolate and identify fungi from surface-sterilized honeybees (Apis mellifera), as well as to evaluate their biological activities. One fungal isolate was obtained and identified morphologically and genetically as Mucor bainieri MK-Bee-2. Gas chromatography-mass spectroscopy (GC–MS) analysis of fungus crude extract, showed the existence of six major metabolites representing 92.48% of the total peak area. The crude extract of Mucor bainieri MK-Bee-2 was tested for antimicrobial, antioxidant, and antitumor activities. It demonstrated wide antimicrobial activities against human pathogenic Gram-positive and Gram-negative bacterial strains, as well as Candida albicans, with MIC values ranged from 62.5 to 250 µg/ml. The results revealed that the extract exhibited considerable antioxidant activities indicated by strong inhibition of both DPPH and ABTS free radicals. Additionally, the extract exhibited greater potential anticancer activity against both adenocarcinomic human non-small cell lung cancer cells (A549) [IC₅₀ = 6.45 μg/ml], and immortal cell line hepatoma G2 (HepG2) human liver cancer cells [IC₅₀ = 27.48 μg/ml] and higher selectivity in cancer cells than normal cell lines. Furthermore, the extract showed less cytotoxic activity against normal cells with higher IC₅₀ values of 106.99 and 132.57 μg/ml against human lung fibroblast Wistar-38 (Wi-38) and oral epithelial cells (OEC), respectively. Taken together, the Mucor bainieri MK-Bee-2 extract comprises bioactive compounds as promising potential therapeutic candidates for the treatment of lung cancer. Strikingly, the extract sensitizes the lung cancer cells A549  to the ionizing radiation through the pro-apoptotic pathway as indicated by the annexin V flow cytometry analysis which showed that the extract reduced the apoptosis of lung cancer cells.

Mycosynthesis of Silica Nanoparticles Using Aspergillus niger: Control of Alternaria solani Causing Early Blight Disease, Induction of Innate Immunity and Reducing of Oxidative Stress in Eggplant

The threats to the life and production of crops are exacerbated by climate change and the misuse of chemical pesticides. This study was designed to evaluate the effectiveness of biosynthesized silica nanoparticles (SiO₂-NPs) as an alternative to pesticides against early blight disease of eggplant. Antifungal activity, disease index, photosynthetic pigments, osmolytes, oxidative stress, antioxidant enzymes activities were tested for potential tolerance of eggplant infected with Alternaria solani. Silica nanoparticles were successfully biosynthesized using Aspergillus niger through green and ecofriendly method. Results revealed that SiO₂-NPs exhibited promising antifungal activity against A. solani where MIC was 62.5 µg/mL, and inhibition growth at concentration 1000 µg/mL recorded 87.8%. The disease Index (DI) as a result of infection with A. solani reached 82.5%, and as a result, a severe decrease in stem and root length and number of leaves occurred, which led to a sharp decrease in the photosynthetic pigments. However, contents of free proline, total phenol and antioxidant enzymes activity were increased in infected plants. On the other hand, the treatment with SiO₂-NPs 100 ppm led to a great reduction in the disease Index (DI) by 25% and a high protection rate by 69.69%. A clear improvement in growth characteristics and a high content of chlorophyll and total carotenoids was also observed in the plants as a result of treatment with silica nanoparticles in (healthy and infected) plants. Interestingly, the noticeable rise in the content of infected and healthy plants of proline and phenols and an increase in the activity of super oxide dismutase (SOD) and polyphenol oxidase (PPO). It could be suggested that foliar application of SiO₂-NPs especially 100 ppm could be commercially used as antifungal and strong inducer of plant physiological immunity against early blight disease.

Antifungal Activity of Biosynthesized Silver Nanoparticles (AgNPs) against Aspergilli Causing Aspergillosis: Ultrastructure Study

Currently, nanoparticles and nanomaterials are widely used for biomedical applications. In the present study, silver nanoparticles (AgNPs) were successfully biosynthesized using a cell-free extract (CFE) of Bacillus thuringiensis MAE 6 through a green and ecofriendly method. The size of the biosynthesized AgNPs was 32.7 nm, and their crystalline nature was confirmed by XRD, according to characterization results. A surface plasmon resonance spectrum of AgNPs was obtained at 420 nm. Nanoparticles were further characterized using DLS and FTIR analyses, which provided information on their size, stability, and functional groups. AgNPs revealed less cytotoxicity against normal Vero cell line [IC₅₀ = 155 μg/mL]. Moreover, the biosynthesized AgNPs exhibited promising antifungal activity against four most common Aspergillus, including Aspergillus niger, A. terreus, A. flavus, and A. fumigatus at concentrations of 500 μg/mL where inhibition zones were 16, 20, 26, and 19 mm, respectively. In addition, MICs of AgNPs against A. niger, A. terreus, A. flavus, and A. fumigatus were 125, 62.5, 15.62, and 62.5 μg/mL, respectively. Furthermore, the ultrastructural study confirmed the antifungal effect of AgNPs, where the cell wall's integrity and homogeneity were lost; the cell membrane had separated from the cell wall and had intruded into the cytoplasm. In conclusion, the biosynthesized AgNPs using a CFE of B. thuringiensis can be used as a promising antifungal agent against Aspergillus species causing Aspergillosis.