Biogenic Silver Nanoparticles: Evaluation of Their Biological and Catalytic Potential

Toxicity of synthesized silver nanoparticles in a widespread fish: A comparison between green and chemical

Metallic nanoparticles are gaining importance in various fields of life due to their large surface area to volume ratio. However, metallic nanoparticles pose different toxic effects on fish when they appear with different shapes and compositions in water. Herein the present study was designed to evaluate the median (LC₅₀) and sub-lethal (1/10th of LC₅₀) concentrations of Ag-Green NPs, 700 μg/L for Ag-Chem NPs, and 50 μg/L for Ag₂O-Chem NPs were confirmed in Hypophthalmichthys molitrix. Furthermore, exposure of H. molitrix fingerlings to 10 % of LC₅₀ concentration of these particles induced significantly higher (p < 0.05) activities of serum alanine transaminase, aspartate aminotransferase, lactate dehydrogenase, white blood cells, acetylcholinesterase and catalase, superoxide dismutase, peroxidase, relative gene expressions of antioxidant enzymes, heat shock protein (Hsp70), hypoxia- inducible factor 1-alpha (HIF-1α) and lipid peroxidase level than the control, but decreased hematological parameters with less effects of Ag-Green NPs than chemically synthesized AgNPs. Moreover, the histopathological study also indicated morphological changes in the liver and gills of treated fish groups. The comparative toxicity evaluation revealed the maximum negative effect of Ag₂O-Chem NPs followed by Ag-Chem NPs while Ag-Green NPs showed the least toxic effects. Based on our results, replacement of chemically synthesized NPs to green synthesized AgNPs can be recommended in large scale application to reduce the noxious effects to aquatic environment.

Phyto-fabrication of silver nanoparticles and their catalytic dye degradation and antifungal efficacy

The biogenic synthesis of silver nanoparticles (AgNPs) and their potent application against dye degradation and phytopathogens are attracting many scientists to nanotechnology. An attempt was made to synthesize silver nanoparticles using Plantago ovata leaf extract and test their effectiveness in removing organic dyes and antifungal activity. In the present study, stable AgNPs were synthesized from 0.1 mM AgNO₃ and authenticated by observing the color change from yellow to red-brown, which was confirmed with wavelength UV-Vis spectrophotometer detection. The crystalline nature of the particles was characterized by x-ray diffraction (XRD) patterns. Furthermore, the AgNPs were characterized by high-resolution transmission electron microscope and scanning electron microscope investigations. Atomic force microscopy (AFM) and Raman spectra were also used to confirm the size and structure of the synthesized AgNPs. The elemental analysis and functional groups responsible for the reduction of AgNPs were analyzed by electron dispersive spectroscopy and fourier transform infra-red spectroscopy Fourier transforms infrared, respectively. A new biological approach was taken by breaking down organic dyes such as methylene blue and congo red. The AgNPs effectively inhibit the fungal growth of Alternaria alternata. This could be a significant achievement in the fight against many dynamic pathogens and reduce dye contamination from waste water.

Biosynthesis of silver nanoparticles with antibacterial, antioxidant, anti-inflammatory properties and their burn wound healing efficacy

The current study aims to develop a novel burn wound ointment consisting of sheep’s tail ointment loaded with AgNP. The AgNP in the ointment serves as an antibacterial, antioxidant and anti-inflammatory agent. The AgNP was developed via the biological method with the assistance of the medicinal plant Rhodiola rosea. The characterization of AgNP was assessed using UV-Vis spectroscopy, FTIR, Zeta Potential, XRD, PCCS, SEM, and EDX techniques. The formation of AgNP was confirmed by UV-Vis spectrum at the absorbance of ∼430 nm, and the biomolecules responsible for reducing and capping the AgNP were characterized by FTIR analysis. The stability of AgNP was determined with Zeta potential, which revealed a highly stable colloidal solution with a surface charge of −68.38 ± 3.4 mV. The synthesized AgNP had a face-centered cubic structure with a crystallite size of 23 nm and average grain size of 67.5 nm. The SEM image showed a fairly monodisperse 20 nm-sized spherical-shaped AgNP. The synthesized AgNP contained high purity of the silver, and a low concentration of AgNP inhibited both Gram-positive and Gram-negative bacteria. Moreover, the scavenging activity of AgNP was investigated using DPPH and H₂O₂ scavenging assay, and the results revealed a dose-dependent antioxidant activity with the highest activity at a concentration of 450 μg/ml. Finally, the burn wound healing effect was evaluated by applying the AgNP-loaded ointment to the wound site of BALB/c mice. The in-vivo studies confirmed that AgNP-loaded ointment reduced the wound size, decreased the epidermis layer, and lowered mast cell migration compared to untreated burn wounds. And the synthesized AgNP regulated both pro-inflammatory and anti-inflammatory gene expression, thereby promoting burn wound closure on BALB/c mice. The developed AgNP-loaded ointment has the potential to be applied in the biomedical field.

Green Synthesis of Silver Nanoparticles Using Allium cepa var. Aggregatum Natural Extract: Antibacterial and Cytotoxic Properties

The chemical content of plant excerpts can be efficiently employed to reduce the metal ions to nanoparticles in the one-pot green production method. Here, green production of silver nanoparticles (AC-AgNPs) is performed by means of Allium cepa var. Aggregatum (shallot) extract as a stabilizer and reducer. The shape, size, and morphology of resultant AC-AgNPs are examined by optical spectroscopy analysis such as UV for nucleation and coalescence processes of the AC-AgNPs. Through FTIR functional group is determined and through DLS size is defined, it was confirmed that metallic AgNPs were successfully synthesized through the green synthesis route, and these results agreed well with the results obtained in the XRD pattern along with TEM spectroscopy, where the TEM images confirm the formation of sphere-like nanostructures along with SAED analysis. The chemical characterization is performed with XPS; the obtained molecular species in the materials are determined from the energy profile. Antioxidant activity of AC-AgNPs versus DPPH substrate is carried out. Antibacterial activity is well established against Gram-negative and Gram-positive organisms. Cell viability is accomplished, followed by an MTT assay, and a cytotoxicity assay of AC-AgNPs on MCF—7 cell lines is also carried out. Highlights: (1). This study highlights the eco-friendly synthesis of silver nanoparticles from Allium cepa var. Aggregatum Natural Extract. (2). The synthesized AC-AgNPs were characterized by UV-VIS, FT-IR, XRD, TEM, and XPS. (3). The synthesized nanoparticles were well dispersed in nature and the size range of 35 ± 8 nm. (4). The anti-candidal activity of biosynthesized silver nanoparticles was evaluated against the following Gram-Negative organisms: Escherichia coli (E. coli), and the following Gram-positive organisms: Staphylococcus aureus strains. The biosynthesized AC-AgNPs showed enhanced antiseptic features anti both Gram-positive and negative organisms. (5). Besides, the in vitro cytotoxic outcomes of AC-AgNPs were assessed versus MCF-7 cancerous cells, and the reduction in the feasibility of cancer cells was established via MTT assay, which suggests potential biomedical applications.

Molecular Recognition of Citroflavonoids Naringin and Naringenin at the Active Site of the HMG-CoA Reductase and DNA Topoisomerase Type II Enzymes of Candida spp. and Ustilago maydis

Two agents from natural sources, citroflavonoids naringin and naringenin, can target enzymes in pathogenic yeasts responsible for hospital infections and crop failure. The aim of this study was to examine the molecular recognition site for naringin and naringenin on the HMGR and TOPOII enzymes of eleven Candida species and one phytopathogen, U. maydis, and evaluate yeast susceptibility to these flavonoids. The HMGR and TOPOII enzymes were analyzed in silico. The alignment of the two enzymes in the twelve pathogenic organisms with the corresponding enzyme of Homo sapiens revealed highly conserved amino acid sequences. Modeling studies of the enzymes indicated highly conserved structures. According to molecular docking simulations, both citroflavonoids recognized the amino acid residues of the active site of the enzymes. Binding energy values were higher for naringin (-10.75 and -9.38 kcal/mol, respectively) than simvastatin on HMGR (-9.9) and curcumin on TOPOII (-8.37). The appraisal of twenty-nine virtual mutations provided evidence of probable mechanisms of resistance (high binding energy) or susceptibility (low energy) to the drugs and emphasized the role of key residues. An in vitro susceptibility evaluation of the twelve yeasts demonstrated that the two flavonoids have similar or better MIC values than those reported for the reference compounds, obtaining the lowest with Candida dubliniensis (2.5 µg/ml) and U. maydis (5 µg/ml). Based on the present findings, naringin and naringenin could possibly be effective for treating diseases caused by pathogenic yeasts of the Candida species and U. maydis, presumably by inhibition of their HMGR and TOPOII enzymes.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12088-021-00980-0.

Investigating the Possibility of Green Synthesis of Silver Nanoparticles Using Vaccinium arctostaphlyos Extract and Evaluating Its Antibacterial Properties

Objective

Vaccinium genus plants have medicinal value, of which Vaccinium arctostaphylos (Caucasian whortleberry or Qare-Qat in the local language) is the only available species in Iran. Public tendency to use herbal remedies and natural products such as synthesized nanoparticles is increasing due to the proof of the destructive side effects of chemical drugs. Nanosilver products have been effective against more than 650 microbe types. This study was aimed at assessing the possibility of green synthesis of silver nanoparticles using Vaccinium arctostaphylos aqueous extract and at evaluating its antibacterial properties, as well.

Materials and Methods

In order to synthesize silver nanoparticles, different volumes of Vaccinium arctostaphylos aqueous extract (3, 5, 10, 15, and 30 ml) were assessed with different silver nitrate solution concentrations (0.5, 1, 3, 5, and 10 mM) and different reaction time durations (1, 3, 5, 10, and 20 minutes) at room temperature using a rotary shaker with a speed of 150 rpm. Ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction analysis (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were carried out. The antibacterial activity of the aqueous extract and the synthesized nanoparticles was evaluated, as well.

Results

Silver nanoparticle formation process was confirmed with XRD analysis, transmission electron microscopy (TEM), and FTIR spectroscopy. The UV-Vis spectroscopy of silver colloidal nanoparticles showed a surface plasmon resonance peak at 443 nm under optimal conditions (3 ml aqueous extract volume, 1 mM silver nitrate solution concentration, and 3 min reaction time under sunlight exposure). The reduction of silver ions to silver nanoparticles in solution was confirmed, as well. Based on X-ray diffraction analysis, the size of silver nanoparticles was in the range of 7-16 nm. TEM images showed an even distribution of silver nanoparticles, with a spherical shape. FTIR spectroscopy demonstrated the presence of different functional groups of oxygenated compounds such as carboxyl, hydroxyl, and nitrogenous groups. The antibacterial properties of the synthesized nanoparticles were confirmed.

Conclusion

The synthesized nanoparticles showed more antibacterial properties against gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) than gram-negative ones (Escherichia coli and Salmonella enteritidis).

Assessment of antibacterial and anticancer capability of silver nanoparticles extracellularly biosynthesized using Aspergillus terreus

The present study explores biosynthesis of silver nanoparticles (AgNPs) employing extracellular extract of Aspergillus terreus ITCC 9932.15. Modulation of various variables that dictate the biosynthesis of AgNPs, suggested of optimal AgNPs synthesis using AgNO3, 1 mM at pH 8 and temperature, 35 °C. The biosynthesis of AgNPs was observed to be time dependent with incremental particle synthesis till 24 h. Various studies were undertaken to authenticate formation and characterization of AgNPs for size, crystallinity and biomolecules involved. A sharp SPR peak observed at 420 nm in the UV–vis absorption spectra validated synthesis of nanoparticles. These particles exhibited spherical morphology with size ∼25 nm and −16 mV of zeta potential. Further, the existence of proteins and other biomolecules onto the surface of AgNPs was confirmed with FTIR studies. The SAED pattern investigated by employing TEM authenticated the crystallinity of AgNPs. The AgNPs also exhibited potential antibacterial activity against Gram-negative and Gram-positive bacteria (E. coli and P. aeruginosa). In addition, remarkable anticancer activity was obtained in breast cancer cell line (MCF-7).