Does the antibacterial activity of silver nanoparticles depend on the shape of the nanoparticle? A study of the Gram-negative bacterium Escherichia coli

In this work we investigated the antibacterial properties of differently shaped silver nanoparticles against the gram-negative bacterium Escherichia coli, both in liquid systems and on agar plates. Energy-filtering transmission electron microscopy images revealed considerable changes in the cell membranes upon treatment, resulting in cell death. Truncated triangular silver nanoplates with a {111} lattice plane as the basal plane displayed the strongest biocidal action, compared with spherical and rod-shaped nanoparticles and with Ag(+) (in the form of AgNO(3)). It is proposed that nanoscale size and the presence of a {111} plane combine to promote this biocidal property. To our knowledge, this is the first comparative study on the bactericidal properties of silver nanoparticles of different shapes, and our results demonstrate that silver nanoparticles undergo a shape-dependent interaction with the gram-negative organism E. coli.     

Phosphonic acid analogue of forfenicine — synthesis, antibacterial activity and degradation byPseudomonas fluorescens

Summary Phosphonic acid analogue of forfenicine, amino (p-formylbenzyl)-phosphonic acid, was synthesized and evaluated as antibacterial agent. As indicated by disc diffusion test this compound was found to inhibit significantly the growth ofBacillus subtilis andStaphylococcus aureus and moderately the growth ofEscherichia coli. Resistance ofPseudomonas fluorescens to the action of the aminophosphonate may result from the ability of the strain to degrade this compound.     

Antioxidant,cytotoxic and antibacterial potentials of biosynthesized silver nanoparticles using bee’s honey from two different floral sources in Saudi Arabia

Nowadays, the innovative study of silver nanoparticles (AgNPs) is excessive since they have incredible biomedical applications. The current study aimed to find out the potential of honey from two different floral sources (Ziziphus spina-christi and Acacia gerrardii) as biogenic mediators to synthesize AgNPs and to evaluate their antioxidant, cytotoxic and antimicrobial abilities. Biogenic AgNPs were studied for particle characterizations and the expected biomolecules helped in the reduction process of silver (Ag) ions to AgNPs. Results demonstrated different sizes (50–98 nm) and potentials −42 and −40 for AgNPs prepared using different biological materials, therefore different 1,1-Diphenyl-2-picrylhydrazyl (DPPH) scavenging free radicals were observed. Cytotoxic effect in a dose-dependent manner was detected against HepG2 ca cells for biogenic AgNPs resulted from cell apoptosis that detected by caspase 3/7 activation and AO/EB staining in the treated cells compared to their corresponding controls. Furthermore, biogenic AgNPs suppressed the growth of Methicillin-resistant bacteria Staphylococcus aureus (Gram-positive) besides Escherichia coli and Peseudomonas aeruginosa (Gram-negative). The IC₅₀ of AgNPs was between 15.8 and 14.1 μg/mL and the antibacterial capability was between 22.8 ± 1.2 and 17.0 ± 0.1 mm. Bacterial membrane disturbance was evident in the current study when treated bacteria were studied by field emission scanning electron microscopy (FE-SEM) in relation to untreated controls. Overall, the present findings indicated the possibility of simple green synthesis of AgNPs using bee’s honey, which are effective agents in some biomedical applications. Detailed future work is needed to further validate the results.     

Design,synthesis and structure–activity relationships of substituted oxazole–benzamide antibacterial inhibitors of FtsZ

The design, synthesis and structure–activity relationships of a series of oxazole–benzamide inhibitors of the essential bacterial cell division protein FtsZ are described. Compounds had potent anti-staphylococcal activity and inhibited the cytokinesis of the clinically-significant bacterial pathogen Staphylococcus aureus. Selected analogues possessing a 5-halo oxazole also inhibited a strain of S. aureus harbouring the glycine-to-alanine amino acid substitution at residue 196 of FtsZ which conferred resistance to previously reported inhibitors in the series. Substitutions to the pseudo-benzylic carbon of the scaffold improved the pharmacokinetic properties by increasing metabolic stability and provided a mechanism for creating pro-drugs. Combining multiple substitutions based on the findings reported in this study has provided small-molecule inhibitors of FtsZ with enhanced in vitro and in vivo antibacterial efficacy.     

Ionic liquid promoted synthesis, antibacterial and in vitro antiproliferative activity of novel α-aminophosphonate derivatives

Ionic liquid ethyl ammonium nitrate is used as an excellent catalyst and solvent for three-component one-pot reaction of an aldehydes, amines and diethylphosphite to form novel α-aminophosphonates at room temperature. Among the various catalysts, the preparation of ethyl ammonium nitrate is an environmental friendly, cost effective and recyclable catalyst. Compounds 4b, 4c, 4d, 4f and 4j were found more potent antibacterials against pathogenic microorganisms. Whereas, compounds 4a, 4g, 4h and 4j inhibits growth of active Escherichia coli NCIM 2645 and Salmonella typhi NCIM 2501. Compound 4j was found a promising antiproliferative agent against A549 and SK-MEL2 human melanoma cell lines.     

In vitro antileukemia,antibacterial and antifungal activities of some 3d metal complexes: Chemical synthesis and structure – activity relationships

The present paper describes the synthesis, characterization and in vitro biological evaluation screening of different classes (ammoniacates, dioximates, carboxylates, semi- and thiosemicarbazidates) of Co(II), Co(III), Cu(II), Ni(II), Mn(II), Zn(II) and Fe(III) complexes. Schiff bases were obtained from the reaction of some salicyl aldehydes with, respectively, furoylhydrazine, benzoylhydrazine, semicarbazide, thiosemicarbazide and S-methylthiosemicarbazide to give tridentate ligands containing ONO, ONS or ONN as donor atoms. The synthetic metal complexes are of various geometrical and electronic structures, thermodynamic and thermal stabilities, and magnetic and conductance properties. All complexes, except those of Cu, are octahedral. Some Cu, Co and Mn compounds have a dimeric or a polymeric structure. The composition and structure of complexes were analysed by elemental analysis, IR and ¹H NMR and ¹³C NMR spectroscopies, and magnetochemical, thermoanalytical and molar conductance measurements. All ligands and metal complexes were tested as inhibitors of human leukemia (HL-60) cells growth, and the most potent, the Cu(II) complexes, have been also tested for their in vitro antibacterial and antifungal activities. Structure-activity relationships were carried out.     

Design,synthesis and exploring the quantitative structure–activity relationship of some antioxidant flavonoid analogues

A series of flavonoid analogues were synthesized and screened for the in vitro antioxidant activity through their ability to quench 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical. The activity of these compounds, measured in comparison to the well-known standard antioxidants (29–32), their precursors (38–42) and other bioactive moieties (38–42) resembling partially the flavone skeleton was analyzed further to develop Quantitative Structure–Activity Relationship (QSAR) models using the Genetic Function Approximation (GFA) technique. Based on the essential structural requirements predicted by the QSAR models, some analogues were designed, synthesized and tested for activity. The predicted and experimental activities of these compounds were well correlated. Flavone analogue 20 was found to be the most potent antioxidant.     

Enzymatic synthesis of novel oligosaccharides from N-acetylsucrosamine and melibiose using Aspergillus niger α-galactosidase,and properties of the products

Two kinds of oligosaccharides, N-acetylraffinosamine (RafNAc) and N-acetylplanteosamine (PlaNAc), were synthesized from N-acetylsucrosamine and melibiose using the transgalactosylation activity of Aspergillus niger α-galactosidase. RafNAc and PlaNAc are novel trisaccharides in which d-glucopyranose residues in raffinose (Raf) and planteose are replaced with N-acetyl-d-glucosamine. These trisaccharides were more stable in acidic solution than Raf. RafNAc was hydrolyzed more rapidly than Raf by α-galactosidase of green coffee bean. In contrast, RafNAc was not hydrolyzed by Saccharomyces cerevisiae invertase, although Raf was hydrolyzed well by this enzyme. These results indicate that the physicochemical properties and steric structure of RafNAc differ considerably from those of Raf.     

A randomized,double-blind,prospective, placebo-controlled study of the efficacy of a diet supplemented with curcuminoids extract,hydrolyzed collagen and green tea extract in owner’s dogs with osteoarthritis

Background

We have previously demonstrated that a mixture of Curcuminoids extract, hydrolyzed COllagen and green Tea extract (CCOT) inhibited inflammatory and catabolic mediator’s synthesis by bovine and human chondrocytes. A randomly allocated, double-blind, prospective, placebo-controlled study was performed to evaluate the efficacy of a diet containing this CCOT mixture on dogs with naturally occurring osteoarthritis (OA). Therefore, 42 owner’s dogs with OA were randomly assigned to receive for 3 months an experimental diet (control) or the same diet supplemented with CCOT.

Results

Ground reaction forces did not show statistical differences between groups. After 3 months of feeding, there was a significant reduction of pain at manipulation in the CCOT group, but not in the control group. The evolution for pain at manipulation depended on the diet. The three other parameters evaluated by veterinary subjective assessment (lameness, pain at palpation and joint mobility) did not show statistical differences. Concerning owner subjective assessment, pain severity score worsened in the control group but remained stable in CCOT group. The evolution for pain severity depended on the diet. No statistical difference was found for pain interference, except for the ability to rise to standing from lying down, which was significantly improved in the CCOT compared to the control group. Serum OA biomarkers did not show statistical differences.

Conclusions

Objective variables measured, such as ground reaction forces and OA biomarkers, did not show statistical differences. However, indicators of pain appeared reduced in dogs receiving CCOT mixture for 3 months. The difference of evolution between groups suggests that a greater number of dogs may be necessary to reach a stronger effect on other parameters.

     

Anti-inflammatory, pro-apoptotic, and anti-proliferative effects of a methanolic neem (Azadirachta indica) leaf extract are mediated via modulation of the nuclear factor-κB pathway

Azadirachta indica (neem tree) is used in traditional Indian medicine for its pharmacological properties including cancer prevention and treatment. Here, we studied a neem extract's anti-inflammatory potential via the nuclear factor-κB (NF-κB) signaling pathway, linked to cancer, inflammation, and apoptosis. Cultured human leukemia cells were treated with a methanolic neem leaf extract with or without tumor necrosis factor (TNF)-α stimulation. Inhibition of NF-κB activity was demonstrated by luciferase assay and electrophoretic mobility shift assay (EMSA). Inhibition of viability by neem extracts was assessed by luminescent assays. Western blot analysis allowed assessing the inhibitory effect of the neem extract on TNF-α-induced degradation of inhibitor of κB (IκB) and nuclear translocation of the NF-κB p50/p65 heterodimer. Inhibition of IκB kinase (IKK) activity was shown as well as the effect of neem extract on the induction of apoptotic cell death mechanisms by nuclear fragmentation analysis and flow cytometry analysis. In conclusion, our data provide evidence for a strong effect of the neem extract on pro-inflammatory cell signaling and apoptotic cell death mechanisms, contributing to a better understanding of the mechanisms triggered by Azadirachta indica.     

An assay for mutagenic activity of 4CMB, 4HMB and BC,using the “microtitre” fluctuation test

4CMB, 4HMB and BC were assayed for mutagenic activity using the ‘microtitre’ bacterial fluctuation test without metabolic activation. 4CMB was positive in strains of Salmonella typhimurium detecting both base-substitution and frameshift mutation. BC was weakly positive only in the strain which detects base-substitution mutation. 4HMB was negative in both strains. 4CMB and 4HMB were equally toxic to the strains, whilst BC was comparatively less toxic.     

Are phytochrome-mediated effects on leaf growth, carbon partitioning and extractable sucrose-phosphatesynthase activity the mere consequence of stem-growthresponses in light-grown mustard?

Growth, carbohydrate pools and extractable sucrose-phosphatesynthase (SPS) activity were studied in the leaves of light-grownmustard seedlings exposed tored or far-red end-of-day lightpulses. Over a single dark period far-red, compared to red light(a) had no effect on leaf amounts of reducing sugars, sucrose,starch, and hemicellulose, (b) reduced cellulose accu-mulationin the leaves, and (c) caused a rapid promo-tion of extractableactivity for SPS (lag     

Structural characteristics and aboveground biomass of old‐growth spruce–fir stands in the eastern Carpathian mountains,Ukraine

Abstract

Temperate old‐growth forests are known to have ecological characteristics distinct from younger forests, but these have been poorly described for the remaining old‐growth Picea abies–Abies alba forests in the eastern Carpathian mountains. In addition, recent studies suggest that old‐growth forests may be more significant carbon sinks than previously recognized. This has stimulated interest in quantifying aboveground carbon stocks in primary forest systems. We investigated the structural attributes and aboveground biomass in two remnant old‐growth spruce–fir stands and compared these against a primary (never logged) mature reference stand. Our sites were located in the Gorgany Nature Reserve in western Ukraine. Overstory data were collected using variable radius plots; coarse woody debris was sampled along line intercept transects. Differences among sites were assessed using non‐parametric statistical analyses. Goodness‐of‐fit tests were used to evaluate the form of diameter distributions. The results strongly supported the hypothesis that old‐growth temperate spruce–fir forests have greater structural complexity compared to mature forests, including higher densities of large trees, more complex horizontal structure, and elevated aboveground biomass. The late‐successional sites we sampled exhibited rotated sigmoid diameter distributions; these may reflect natural disturbance dynamics. Old‐growth Carpathian spruce–fir forests store on average approximately 155–165 Mg ha^?1 of carbon in aboveground tree parts alone. This is approximately 50% higher than mature stands. Given the scarcity of primary spruce–fir forests in the Carpathian region, remaining stands have high conservation value, both as habitat for late‐successional species and as carbon storage reservoirs.     

Biological activity in Cerrado soils: evaluation of vegetation,fire and seasonality effects using the “bait-lamina test”

Aims

The Cerrado, a South American savanna, is considered a priority for conservation. In this case study, we assessed soil feeding activity as a way to improve understanding of the ecosystem functioning, in order to support and refine conservation strategies.

Methods

Soil feeding activity was assessed using the bait-lamina method under different environmental conditions: in the dry and rainy seasons, in burned and unburned areas, and under native and invasive grasses.

Results

Feeding activity was significantly reduced after fire, but recovered to pre-fire levels with the rains. Activity increased significantly during the rainy season in both areas, being more pronounced in the unburned area. The highest feeding activity was observed under the invasive grass (Melinis minutiflora). Feeding activity declined with soil depth and was affected by season and fire.

Conclusions

Seasonality was the most important factor affecting the feeding activity of soil organisms, followed by the fire history and the extant vegetation. Although this method does not allow distinguishing between feeding activity of different organisms, it can provide valuable insights into differences in soil functioning due to changes in environmental conditions.     

Ιn vitro plant regeneration from leaf explants of the cherry rootstocks CAB-6P,Gisela 6, and MxM 14 using sodium nitroprusside

Conventional multiplication of cherry (Prunus cerasus L.) rootstocks utilizes division, cuttings, and propagation through seed, which are relatively slow and labor intensive and result in genetic variability. Tissue culture, on the other hand, ensures rapid, large-scale, and low-cost production of genetically identical, physiologically uniform, and pathogen-free plants. In the cherry rootstocks CAB-6P, Gisela 6, and MxM 14, sodium nitroprusside (SNP) promoted callus induction, in vitro shoot proliferation, and rooting from leaf explants in a medium containing 17.6 μM benzyladenine and 2.68 μM α-naphthaleneacetic acid. CAB-6P explants treated with 10 μM SNP gave the maximum shoot number (5), whereas 30 μM SNP gave the longest shoots and the greatest shoot induction rate (26.67%). Best rooting was obtained with 50 μM SNP. In Gisela 6 rootstock, the shoot number (10) and shoot length (20.5 mm) were maximal in the control group without plant growth regulators. The shoot induction rate was enhanced (40%) with 40 μM SNP. SNP at 40 μM resulted in root formation, while 30 μM produced the largest callus size, and 10 μM SNP resulted in the maximum callus fresh weight. MxM 14 leaves treated with 30 μM SNP gave the maximum shoot number (3), root number (7.56), and shoot induction rate (40%), whereas 40 μM SNP gave the longest shoots (12 mm) and roots (20 mm). Best results for callus size, callus fresh weight, and callus induction rate (100%) in the CAB-6P and MxM 14 rootstocks were observed with 30 and 40 μM SNP, respectively. Rooted explants with shoots were gradually acclimatized to the external environment with a high survival percentage (85%). An efficient protocol of indirect organogenesis was established for the three cherry rootstocks using SNP.     

Biomimetic synthesis and characterization of cobalt nanoparticles using apoferritin, and investigation of direct electron transfer of Co(NPs)–ferritin at modified glassy carbon electrode to design a novel nanobiosensor

Oxyhydroxy cobalt CoO(OH) nanoparticles (Co-NPs) were prepared in horse spleen apoferritin (HsAFr) cavity. Transmission electron microscopy revealed the particle size was 5.5-6 nm. Mineralization effect on HsAFr was investigated by fluorescence and far-UV circular dichroism (far-UV CD) spectroscopies. The far-UV CD experiments indicated an increase in the α-helical content after mineralization. Intrinsic fluorescence data showed that mineralization acts as a quencher of HsAFr. For the first time, direct electron transfer between Co(NPs)-HsAFr and a glassy carbon electrode in the thin film of dihexadecylphosphate (DHP) was investigated by cyclic voltammetry (CV) to design a biosensor. The anionic surfactant DHP was used to achieve direct electron-transfer between Co(NPs)-HsAFr molecules and the GC electrode surface. CV result showed clearly a pair of well-defined and quasi-reversible redox peaks arise from Co(NPs)-HsAFr embedded in DHP film. This novel biosensor can be used in medical and industrial fields to detect different analytes.     

Design,synthesis and structure–activity relationship of novel quinoxalin-2-carboxamides as 5-HT3 receptor antagonists for the management of depression

A novel series of quinoxalin-2-carboxamides were designed based on the ligand-based approach, employing a three-point pharmacophore model; it consists of an aromatic residue and a linking carbonyl group and a basic nitrogen. The target new chemical entities were synthesized from the key intermediate, quinoxalin-2-carboxylic acid, by coupling it with various amines in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 1-hydroxybenzotriazole (HOBt). The obtained compounds’ structures were confirmed by spectral data. The target new chemical entities were evaluated for their 5-HT₃ receptor antagonisms in longitudinal muscle myenteric plexus preparation from guinea pig ileum against 5-HT₃ agonist, 2-methyl-5-HT, which was expressed in the form of pA₂ value. All the synthesized compounds showed antagonism towards 5-HT₃ receptor; based on this result, a structure–activity relationship was derived, which reveals that the aromatic residue in 5-HT₃ receptor antagonists may have hydrophobic interaction with 5-HT₃ receptor. Regardless of their antagonistic potentials, all the synthesized molecules were screened for their anti-depressant potentials by using forced swim test in mice model; interestingly none of the tested compounds affect the locomotion of mice in the tested dose levels. Compounds with significant pA₂ values exhibited good anti-depressant-like activity as compared to the vehicle-treated group.     

Design,synthesis and evaluations of acridone derivatives using Candida albicans—Search for MDR modulators led to the identification of an anti-candidiasis agent

In order to search for MDR modulators, rationally designed acridone derivatives were investigated for their effect on influx or efflux of Rhodamine6G (R6G) in CAI4 cells. Results of these investigations indicate that in presence of compound 12, inhibition of growth of CAI4 cells and also an increased influx/efflux of R6G in CAI4 cells have been observed. This seems to be occurring due to the cell wall rupturing of Candida albicans. Compound 12 may be a suitable candidate for candidiasis therapy.     

Flow-injection chemiluminescence method for the determination of moxifloxacin in pharmaceutical tablets and human urine using silver nanoparticles sensitized calcein–KMnO<Subscript>4</Subscript> system

Silver nanoparticles have been synthesized and were utilized for the enhanced luminometric estimation of moxifloxacin antibiotic. During the experimental procedure, it was clearly found that the addition of silver nanoparticles intensifies the weak chemiluminescence signal intensity of calcein–KMnO₄ system by several folds. It was also obvious that the intensity enhancement was linearly proportional to the moxifloxacin concentration and this phenomenon was further utilized for the quantitative determination of target analyte. Effects of the different chemical variables during the experiment were studied to achieve best chemiluminescence signal. Under the optimized experimental parameters, the linear calibration graph was established over the moxifloxacin concentration range of 6.0 × 10^?8 M to 2.5 × 10^?6 M with coefficient of correlation (r ²) value 0.9998. The lower detection limit was found to be 5.6 × 10^?9 M. The percentage relative standard deviation calculated from five replicate chemiluminescence measurements was found to be 2.63 %. The developed chemiluminescence technique was successfully applied to the determination of moxifloxacin in tablet formulation and spiked human urine sample.