Synthesis, toxicity evaluation and determination of possible mechanisms of antimicrobial effect of arabinogalactane-capped selenium nanoparticles.

BACKGROUND: The elemental selenium nanoparticles (Se0NPs) find application in biology and medicine due to wide spectrum of their biological activity combined with low toxicity. For instance, Se0NPs are promising antimicrobial agents for plant treatment against the bacterial phytopathogen Clavibacter michiganensis sepedonicus (Cms). Careful characterization of possible mechanisms of antimicrobial action of Se0NPs as well as the assessment of their biosafety for plant and animal organisms represents urgent challenge. METHODS: AG-stabilized Se0NPs (AG/Se0NPs) were synthesized by oxidation of selenide-anions by molecular oxygen dissolved in the reaction medium in the presence of AG macromolecules. The antimicrobial activity of AG/Se0NPs against Cms was investigated both by observing the change in optical density of bacterial suspension and directly evaluating the cell death using fluorescent microscopy with propidium iodide staining. The effect of AG/Se0NPs on the dehydrogenase activity was studied by determination of Cms enzymes ability to reduce colorless TTC to formazan. The effect of AG/Se0NPs nanocomposite on the respiration rate of Cms cells was examined by polarographic method. For qualitative visualization of the potential on the inner membrane of Cms mesosomes, the potential-dependent TMRM dye and fluorescence microscopy were used. The toxicity of the AG/Se0NPs was investigated on white mice by the Litchfield-Wilcoxon method. The effect of AG/Se0NPs on plant organisms (potato plants) was studied on healthy and Cms-infected plants by determining the level of chlorophyll and lipid peroxidation products (LPO) in their leaves when treated with nanoparticles. RESULTS: Spherical Se° nanoparticles with an average size of 94 nm were obtained using the stabilizing potential of AG. It was found that these nanoparticles exhibited the pronounced (up to 60 %) bacteriostatic action (in 6.25 µg/mL concentration) against the bacterial phytopathogen Cms. It was shown and experimentally confirmed for the first time that the probable causes of the bacteriostatic action of AG/Se°NPs against Cms are non-reversible inhibition of Cms cell respiration, a decrease of the transmembrane potential with a change in the cell wall permeability for H+ protons and a decrease in their dehydrogenase activity. It was revealed that the treatment of healthy and Cms-infected potato plants with an aqueous solution of AG/Se°NPs involved no significant changes in the content of LPO and negative effect on the chlorophyll content, thus contributing to the saving of these values at the level of control intact plants. CONCLUSION: Using a complex of complementary methods, we have found that antimicrobial activity of AG/Se0NPs is apparently due to their ability to inhibit the dehydrogenase activity of Cms cells, as well as to disrupt the integrity of the cell membrane, resulting in a decrease of transmembrane potential and reduction of cellular respiration. The antimicrobial and antibiofilm activity of AG/Se0NPs, together with their nontoxicity and safety for plant and animal organisms, determine the prospects for design of AG/Se0NPs-based drugs for the rehabilitation of plants from the Cms.

Chitosan effects on monolayers of zwitterionic, anionic and a natural lipid extract from E. coli at physiological pH.

Langmuir monolayers are used to simulate the biological membrane environment, acting as a mimetic system of the outer or the inner membrane leaflet. Herein, we analyze the interaction of membrane models with a partially N-acetylated chitosan (Ch35%) possessing a quasi-ideal random pattern of acetylation, full water solubility up to pH ≈ 8.5 and unusually high weight average molecular weight. Lipid monolayers containing dipalmitoyl phosphatidyl choline (DPPC), dipalmitoyl phosphatidyl ethalonamine (DPPE), dipalmitoyl phosphatidyl glycerol (DPPG) or E. coli total lipid extract were spread onto subphases buffered at pH 4.5 or 7.4. The incorporation of Ch35% chitosan caused monolayer expansion and a general trend of decreasing monolayer rigidity with Ch35% concentration. Due to its relatively high content of N-acetylglucosamine (GlcNAc) units, Ch35% interactions with negatively charged monolayers and with E. coli extract were weaker than those involving zwitterionic monolayers or lipid rafts. While the smaller interaction with negatively charged lipids was unexpected, this finding can be attributed to the degree of acetylation (35%) which imparts a small number of charged groups for Ch35% to interact. Chitosan properties are therefore determinant for interactions with model cell membranes, which explains the variability in chitosan bactericide activity in the literature. This is the first study on the effects from chitosans on realistic models of bacterial membranes under physiological pH.

Synthesis and bactericide activity of nanofiltration composite membranes - Cellulose acetate/silver nanoparticles and cellulose acetate/silver ion exchanged zeolites.

The present work addresses the synthesis of nanofiltration composite membranes with bactericide properties. The cellulose acetate based membranes with polyvinylpyrrolidone coated silver nanoparticles, silver ion-exchanged ß-zeolite and ß-zeolite are casted by the phase inversion technique and subjected to an annealing post-treatment. They are characterized in terms of the nanofiltration permeation performance and antibacterial properties. The incorporation of silver nanoparticles produces a threefold increase in the membrane hydraulic permeability when compared to the silver-free membranes and the incorporation of silver ion loaded zeolite resulted in a 56.3% increase in hydraulic permeability. In contrast to the influence of silver presence, either in nanometric or in the ionic form, the presence of zeolite does not significantly influence the hydraulic permeability. The rejection coefficients to salts range from 83% to 93% for the silver ion-exchanged zeolite membrane and from 84% to 97% for the polyvinylpyrrolidone coated silver nanoparticles membrane. They are higher for sulfate salts than for chloride salts. The antibacterial properties of the membranes were evaluated against Escherichia coli. The results have shown that the silver ion-exchanged ß-zeolite membrane was effective in inactivating Escherichia coli after just 210 min of contact time. No bacterial activity was detected following 24 h of contact time with the membrane containing polyvinylpyrrolidone coated silver nanoparticles. A reduction of more than 6-log, in the number of Escherichia coli, was achieved for both membranes. The different patterns of bactericide activity are associated to the silver speciation in metallic or ionic form. The high flux nanofiltration composite membranes with bactericidal properties represent a strong asset in water treatment biofouling control.

High Concentrations of Sodium Chloride Improve Microbicidal Activity of Ibuprofen against Common Cystic Fibrosis Pathogens.

Ibuprofen (IBU-H), a widely used anti-inflammatory, also shows a marked antimicrobial effect against several bacterial species, including those involved in cystic fibrosis such as Pseudomona aeruginosa, methicillin resistant Staphylococcus aureus and Burkholderia cepacia complex. Additionally, our results show significant synergy between water soluble Na-ibuprofen (IBU-Na) and ionic strength. Salt concentrations above 0.5 M modify the zeta potential promoting the action of Na-IBU; thus, with 1 M sodium chloride, IBU-Na is ten times more efficient than in the absence of ionic strength, and the minimum effective contact time is reduced from hours to minutes. In short time periods, where neither IBU-Na nor controls with 1 M NaCl show activity, the combination of both leads to a reduction in the bacterial load. We also analyzed whether the changes caused by salt on the bacterial membrane also promoted the activity of other microbicide compounds used in cystic fibrosis like gentamicin, tobramycin and phosphomycin. The results show that the presence of ionic strength only enhanced the bactericidal activity of the amphipathic molecule of IBU-Na. In this respect, the effect of saline concentration was also reflected in the surface properties of IBU-Na, where, in addition to the clear differences observed between 145 mM and 1 M, singular behaviors were also found, different in each condition. The combination of anti-inflammatory activity and this improved bactericidal effect of Na-IBU in hypertonic solution provides a new alternative for the treatment of respiratory infections of fibrotic patients based on known and widely used compounds.

Supplementation with humic substances affects the innate immunity in layer hens in posfasting phase / El suplemento de sustancias húmicas afecta la inmunidad innata en gallinas ponedoras en fase posmuda

Objective. Asses the effect of supplementation with Humic substances (HS) over some innate immunity parameters (serum bactericidal activity, phagocytosis, bacterial agglutination, respiratory burst and lisozyme activity) in phase after fasting of layer hens. Materials and methods. 120 posfasting phase Hy Line Brown layer hens were taken which were distributed into four groups: The first and the second were supplemented with 0.1 and 0.2% of HS, respectively. The third group was supplemented with 0.25 mg/kg on levamisole hydrochloride and fourth group have no supplementation; during sixty days period. Blood samples were collected on 8th, 30th and 60th of experiment day. Results. The phagocytic index and respiratory burst increased significantly at day 30th in HS supplemented groups. Alike, serum bactericidal activity and lisozyme activity improved on 8 th day, nevertheless, changes were no evident latter. The bacterial agglutination was high in supplemented groups evaluated at everyone times. Conclusions. Results showed that HS behave as immunostimulant in the early phase after fasting layer hens.

Objetivos. Evaluar el efecto de las sustancias húmicas (SH) sobre algunos parámetros de la inmunidad innata (actividad bactericida del suero, fagocitosis, aglutinación bacteriana, explosión respiratoria y actividad de la lisozima) en la fase posmuda de gallinas ponedoras. Materiales y métodos. Se utilizaron 120 gallinas ponedoras Hy Line Brown en la fase de posmuda, las cuales fueron divididas en cuatro grupos: Los dos primeros fueron suplementados con 0.1 y 0.2% de SH respectivamente, el tercer grupo fue suplementado con 0.25 mg/kg de Clorhidrato de levamisol y el cuarto grupo control sin suplemento; durante un período de 60 días. Las muestras sanguíneas se tomaron los días 8, 30 y 60 del experimento. Resultados. El Índice fagocítico y la explosión respiratoria se incrementaron significativamente a partir del día 30 de suplementación con SH. De la misma manera, la actividad bactericida del suero y la actividad de la lisozima aumentaron al día 8; no obstante no se evidenciaron cambios posteriores. La aglutinación bacteriana fue significativamente mayor en los grupos suplementados en todos los tiempos evaluados. Conclusiones. Los resultados demuestran que las SH se comportan como agentes inmunoestimulantes en la fase temprana de la posmuda en gallinas ponedoras Hy Line Brown.

Difusão de microrganismos, inibição do crescimento e atividade biocida do cianoacrilato super bonder / Diffusion, growth Inhibition and biocide activity of the super bonder cyanoacrylate

Os objetivos do presente trabalho foram avaliar se o Super Bonder" apresenta algum risco de veiculação de microorganismos em humanos e se possui alguma atividade bactericida ou bacteriostática para cocos gram-positivo. Foi testada a esterilidade de dez tubas do adesivo nos meios de cultivo BHI, agar sangue, agar Sabouraud com cloranfenicol e Mycosel. A provável ação bactericida ou bacteriostática do adesivo Super Bonder"', in vitro, foi verificada utilizando cepas de Staphylococcus aureus e staphylococcus epidermidir, semeadas em meio de cultura agar sangue e agar Mueller-Hinton. Nao foi observado crescimento de microrganismos nos meios de cultura contendo somente gotas de Super Bonder"'. No agar sangue, observou-se ausência de beta-hemólise e de crescimento bacteriano nas áreas de sobreposição do adesivo. Em agarMueller-Hinton, houve rarefação de colônias ao redor das gotas do cianoacrilato.Os dados deste trabalho mostram que a cola de cianoacrilato Super Bonder"' parece ser livre de contaminação por microrganismos e apresenta possfvel atividade bacteriostatica in vitro.

The purposes of the present study were to verify the human's risk of the Super Bondet microorganisms' diffusion and the probably biocide or bacteriostatic adhesive's activity for gram-positive cocci. The sterility of ten tubes of the adhesive was tested in BHI culture tube and blood-agar, agar-Sabouraud with cloranfenicol and Mycosel culture plates. The biocide or bacteriostatic activity of the Super Bondet adhesive, in vitro, was verified using cultures of Staphylococcus aureus and staphylococcus epidermidis,seeded on blood-agar and agar-Mueller-Hinton culture plates. No microorganisms' growth was observed in the culture plates containing only drops of the Super Bondet. In agar-Mueller-Hinton, zones with reduced number of colonies were noticed around the cyanoacrylate's drops. In blood-agar, absence of haemolysis-beta and bacterial growth were observed in the covered areas of the adhesive. According to the results of this investigation, the Super Bondet cyanoacrylate is free of microorganisms' diffusion and probably inhibits in vitro the bacterial growth.