Formation Of Selenium Nanoparticles Research Articles

Characterizations of biogenic selenium nanoparticles and their anti-biofilm potential against Streptococcus mutans ATCC 25175

IntroductionS. mutans has been identified as the primary pathogenic bacterium in biofilm-mediated dental caries. The biogenic selenium nanoparticles (SeNPs) produced by L. plantarum KNF-5 were used in this study against S. mutans ATCC 25175. ObjectivesThe aims of this study were: (1) the biosynthesis of SeNPs by L. plantarum KNF-5, (2) the characterization of SeNPs, (3) the investigation of the inhibitory effect of biogenic SeNPs against S. mutans ATCC 25175, and (4) the determination of the anti-biofilm potential of SeNPS against S. mutans ATCC 25175. Methodology3 mL of the culture was added to 100 mL of MRS medium and incubated. After 4 h, Na2SeO3 solution (concentration 100 μg/mL) was added and incubated at 37 °C for 36 h. The color of the culture solution changed from brownish-yellow to reddish, indicating the formation of SeNPs. The characterization of SeNPs was confirmed by UV-Vis spectrophotometry, FTIR, SEM-EDS and a particle size analyzer. The antibacterial activity was determined by the disk diffusion method, the MIC by the micro-double dilution method, and the biofilm inhibitory potential by the crystal violet method and the MTT assay. The effect of SeNPs on S. mutans ATCC 25175 was determined using SEM and CLSM spectrometry techniques. The sulfate-anthrone method was used to analyze the effect of SeNPs on insoluble extracellular polysaccharides. The expression of genes in S. mutans ATCC 25175 was analyzed by real-time quantitative polymerase chain reaction (RT-qPCR). Preparation of nanoparticlesSeNPs produced by probiotic bacteria are considered a safe method. In this study, L. plantarum KNF-5 (probiotic strain) was used for the production of SeNPs. ResultsThe biogenic SeNPs were spherical and coated with proteins and polysaccharides and had a diameter of about 270 nm. The MIC of the SeNPs against S. mutans ATCC 25175 was 3.125 mg/mL. Biofilm growth was also significantly suppressed at this concentration. The expression of genes responsible for biofilm formation (GtfB, GtfC, BrpA and GbpB,) was reduced when S. mutans ATCC 25175 was treated with SeNPs. ConclusionIt was concluded that the biogenic SeNPs produced by L. plantarum KNF-5 was highly effective to inhibit the growth of S. mutans ATCC 25175. Novelty statementThe application of biogenic SeNPs, a natural anti-biofilm agent against S. mutans ATCC 25175. In the future, this study will provide a new option for the prevention and treatment of dental caries.

Green Synthesis of Selenium Nanoparticles Using Luffa cylindrica and its Biocompatibility Studies for Potential Biomedical Applications

Selenium nanoparticles (SeNPs), due to their unique properties, have attracted researchers’ attention. Though SeNPs have been used for wide applications, the chemically synthesized one lacks stability due to aggregation, and it releases toxic byproducts. These drawbacks can be overcome by producing SeNPs using natural sources as reducing and capping agents. Luffa cylindrica is an immense source of phytochemical compounds reported for its potential therapeutical value towards cancer, asthma, and sinusitis. In the current study, we have synthesized SeNPs using leaf extract of L. cylindrica and evaluated its biocompatibility and haemocompatibility using peripheral blood mononuclear cells and erythrocytes respectively. The formation of SeNPs was confirmed by a color change from greenish yellow to ruby red during 6 h incubation at 40[Formula: see text]C and further confirmed by the maximum absorbance at 266[Formula: see text]nm and 380[Formula: see text]nm in the UV–Vis spectrum. The fingerprint regions of the Fourier-transform infrared spectroscopy spectrum between 1500[Formula: see text]cm[Formula: see text] and 500[Formula: see text]cm[Formula: see text] revealed the presence of phytoconstituents of L. cylindrica. The particle size analysis showed a size range of 100[Formula: see text]nm and zeta potential of −13.6 mV. Scanning electron micrograph showed flower-shaped surface morphology with a size range of 100[Formula: see text]nm. The erythrocytes treated with higher concentrations of LC-SeNPs showed less than 5% lysis compared to the positive control. Similarly, in the apoptosis assay, 80.45% of cells remained viable after being treated with LC-SeNPs, which is comparable with that of untreated control. Since the synthesized SeNPs possess biocompatibility and are less cytotoxic, they could be used in cardiac tissue engineering applications. However, further in vitro and in vivo studies are required to confirm its role in cardiac tissue engineering.

Modification of Some Structural and Functional Parameters of Living Culture of Arthrospira platensis as the Result of Selenium Nanoparticle Biosynthesis.

Selenium nanoparticles are attracting the attention of researchers due to their multiple applications, including medicine. The biosynthesis of selenium nanoparticles has become particularly important due to the environmentally friendly character of the process and special properties of the obtained particles. The possibility of performing the biosynthesis of selenium nanoparticles via the living culture of Arthrospira platensis starting from sodium selenite was studied. The bioaccumulation capacity of the culture, along with changes in the main biochemical parameters of the biomass, the ultrastructural changes in the cells during biosynthesis and the change in the expression of some genes involved in stress response reactions were determined. Protein, lipid and polysaccharide fractions were obtained from the biomass grown in the presence of sodium selenite. The formation of selenium nanoparticles in the protein fraction was demonstrated. Thus, Arthrospira platensis culture can be considered a suitable matrix for the biosynthesis of selenium nanoparticles.

Green-synthesized selenium nanoparticles using garlic extract and their application for rapid detection of salicylic acid in milk

The highly selective, sensitive, and quick interference green synthesis-based sensing of possible milk adulterants i.e., salicylic acid has been reported here. Salicylic acid interacts with nanoparticles through strong bonding interactions, hence resulting in an interruption within the formation of selenium nanoparticles which is confirmed by UV-VIS spectroscopy, scanning electron microscopy, and x-ray diffraction. This interaction in the synthesis of nanoparticles resulted in transmittance wavelength that decrease with the increasing amount of salicylic acid, showing strong binding of selenium nanoparticles with adulterant thereby permitting in-situ fast detection of salicylic acid from milk having a limit of detection at 10-3 mol and linear coefficient correlation of 0.9907.

Actinomycetes mediated microwave-assisted synthesis of nanoselenium and its biological activities

Selenium nanoparticles (SeNPs), an essential trace element are known to be nontoxic with excellent biocompatibility and bioavailability among other selenium compounds. Considering the potential benefits as well as toxic effects of the SeNPs regarding dosage, it is important to evaluate the biomedical efficacy of the functional SeNPs with great care. The current investigation involves the synthesis of SeNPs using culture supernatant of Nocardia concava through microwave-assisted synthesis method. The formation of SeNPs was confirmed by UV-Visible spectroscopy at 570 nm. The XRD spectrum confirmed the monoclinic crystalline phase of the synthesized SeNPs. FTIR spectra depicted the possible functional groups such as hydroxyl and hydrocarbon groups involved in the reduction. EDX micrographs showed strong Se signals at 2 KeV regions. The zeta potential of the synthesized SeNPs was found to be 6.5 mV which confirms good stability in water. SEM micrograph confirmed the spherical nature of the SeNPs. Good antimicrobial efficacy was reported for Xanthomonas campestris MTCC 2286 and Vibrio harveyi MTCC 7954 with a MIC of 1.625 µg/ml and 3.25 µg/ml concentration respectively. Also, they showed strong antioxidant activity in the DPPH assay (IC50 = 31.26 µg/ml) and ABTS assay (IC50 = 35.7 µg/ml). Remarkable cytotoxic activity was observed against MDAMB 231 and U87MG cancer cells with an IC50 value of 119 µg/ml and 65.8 µg/ml respectively whereas, mild toxicity was observed in the case of HT-29 cell lines. This is the first report on the synthesis of SeNPs from Nocardia concava and specifically by a microwave-assisted method. Synthesized SeNPs displayed unique properties that can be used in diverse biomedical applications.

Biotransformation of selenium in the mycelium of the fungus Phycomyces blakesleeanus.

Biotransformation of toxic selenium ions to non-toxic species has been mainly focused on biofortification of microorganisms and production of selenium nanoparticles (SeNPs), while far less attention is paid to the mechanisms of transformation. In this study, we applied a combination of analytical techniques with the aim of characterizing the SeNPs themselves as well as monitoring the course of selenium transformation in the mycelium of the fungus Phycomyces blakesleeanus. Red coloration and pungent odor that appeared after only a few hours of incubation with 10mM Se+4 indicate the formation of SeNPs and volatile methylated selenium compounds. SEM-EDS confirmed pure selenium NPs with an average diameter of 57nm, which indicates potentially very good medical, optical, and photoelectric characteristics. XANES of mycelium revealed concentration-dependent mechanisms of reduction, where 0.5mM Se+4 led to the predominant formation of Se-S-containing organic molecules, while 10mM Se+4 induced production of biomethylated selenide (Se-2) in the form of volatile dimethylselenide (DMSe) and selenium nanoparticles (SeNPs), with the SeNPs/DMSe ratio rising with incubation time. Several structural forms of elemental selenium, predominantly monoclinic Se8 chains, together with trigonal Se polymer chain, Se8 and Se6 ring structures, were detected by Raman spectroscopy.

Selenite Reduction by Proteus sp. YS02: New Insights Revealed by Comparative Transcriptomics and Antibacterial Effectiveness of the Biogenic Se0 Nanoparticles.

Biotransformation of selenite by microorganisms is an effective detoxification (in cases of dissimilatory reduction, e.g., to Se0) and assimilation process (when Se is assimilated by cells). However, the current knowledge of the molecular mechanism of selenite reduction remains limited. In this study, a selenite-resistant bacterium was isolated and identified as Proteus sp. YS02. Strain YS02 reduced 93.2% of 5.0 mM selenite to selenium nanoparticles (SeNPs) within 24 h, and the produced SeNPs were spherical and localized intracellularly or extracellularly, with an average dimension of 140 ± 43 nm. The morphology and composition of the isolated and purified SeNPs were characterized using dynamic light scattering (DLS), scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectrometry, and Fourier transform infrared (FTIR) spectroscopy. FTIR spectroscopy indicated the presence of proteins, polysaccharides, and lipids on the surface of the isolated SeNPs. Furthermore, the SeNPs showed excellent antimicrobial activity against several Gram-positive and Gram-negative pathogenic bacteria. Comparative transcriptome analysis was performed to elucidate the selenite reduction mechanism and biosynthesis of SeNPs. It is revealed that 197 genes were significantly upregulated, and 276 genes were significantly downregulated under selenite treatment. Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that genes associated with ABC transporters, sulfur metabolism, pentose phosphate pathway (PPP), and pyruvate dehydrogenase were significantly enhanced, indicating selenite is reduced by sulfite reductase with PPP and pyruvate dehydrogenase supplying reducing equivalents and energy. This work suggests numerous genes are involved in the response to selenite stress, providing new insights into the molecular mechanisms of selenite bioreduction with the formation of SeNPs.

Simultaneous Sonochemical Coloration and Antibacterial Functionalization of Leather with Selenium Nanoparticles (SeNPs).

The development of antibacterial coatings for footwear components is of great interest both from an industry and consumer point of view. In this work, the leather material was developed taking advantage of the intrinsic antibacterial activity and coloring ability of selenium nanoparticles (SeNPs). The SeNPs were synthesized and implemented into the leather surface by using ultrasonic techniques to obtain simultaneous coloring and functionalization. The formation of SeNPs in the solutions was evaluated using UV/Vis spectroscopy and the morphology of the NPs was determined by transmission electron microscopy (TEM). The treated leather material (leather/SeNPs) was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The effects of SeNPs on the coloration and antibacterial properties of the leather material were evaluated. The results revealed that the NPs were mostly spherical in shape, regularly distributed, and closely anchored to the leather surface. The particle size distribution of SeNPs at concentrations of 25 mM and 50 mM was in the range of 36–77 nm and 41–149 nm, respectively. It was observed that leather/SeNPs exhibited a higher depth of shade compared to untreated ones, as well as excellent fastness properties. The results showed that leather/SeNPs can significantly enhance the antibacterial activity against model of bacteria, including Gram-positive bacteria (Bacillus cereus) and Gram-negative bacteria (Pseudomonas aeruginosa, Salmonella typhi and Escherichia coli). Moreover, the resulting leather exhibited low cytotoxicity against HFB4 cell lines. This achievement should be quite appealing to the footwear industry as a way to prevent the spread of bacterial infection promoted by humidity, poor breathability and temperature which promote the expansion of the microflora of the skin.

Kinetics of reduction of Se (IV) by vitamin C with green synthesis of cluster-grapes nanoparticles: A Mechanistic approach on electron-transfer of nanoparticle growth rates

• Kinetics and mechanistic study of reduction of Se(IV) by vitamin C in acidic solutions. • Green synthesis of selenium nanoparticles of cluster-grapes nature for the first time by using Vitamin C. • Characteristics of synthesized of the synthesized cluster-grapes nanoparticles. • Prospective mechanistic for the nanoparticles growth pathway. • Information on the electron-transfer pathway in the rate-determining step In a series of spectrophotometric investigation studies on some redox reactions involving vitamin C (ascorbic acid) as a reducing agent for reduction of metal ion oxidants in aqueous acidic solutions. It was surprising when the naked eye observations noticed the rabidly turning of selenium dioxide Se(IV) solution from colorless into deeply bright crimson color of colloidal aggregate sol when just mixed with solution of excess vitamin C in either neutral or acidic media. Then, the formed crimson color was gradually turned into crystals of dark purple color on keeping it aside for a long time or on drying in either sunlight or into an electric oven. This result suggests the occurrence of phase-transition with formation of selenium nanoparticles. The formed selenium nanoparticles were characterized by FTIR, XRD as well as the SEM and TEM microscopic morphology. It has been found the formation of such selenium nanoparticles of cluster-grapes nature for the first time. This phenomenon and the great importance of such nanoparticles in biotechnology applications encouraged us to follow the rate of nanoparticles growth through the reduction of selenium dioxide by vitamin C on using a conventional spectrophotometer. A first-order dependences in both selenium (IV) and vitamin C concentrations; second-order overall kinetics have been revealed. Free-radical intervention was detected during the oxidation progression. The influence of [H + ] on the rate constants showed that the oxidation was of acid-inhibition nature. In view of the evaluated kinetic parameters, a plausible reaction mechanism of two-electron transfer pathway of inner-sphere nature was suggested and discussed.

Green synthesis of selenium nanoparticle by Abelmoschus esculentus extract and assessment of its antibacterial activity

ABSTRACT Green synthesis of selenium nanoparticles (Se-NPs) was done using Abelmoschus esculentus extract as the capping and reducing agent and sodium selenite (Na2SeO3) as the selenium source. UV-Vis spectrum confirmed the formation of Se-NPs in the solution. According to the XRD pattern, the average particle size was estimated to be about 30.7 nm. The TEM images shown the spherical shape of Se-NPs. The antimycobacterial effects of Se-NPs were tested against the standard strains of Mycobacterium tuberculosis (H37RV) and Mycobacterium simiae isolates. Antibacterial impacts were examined through the usage of resazurin microtiter assay (REMA) against bacterial strains, including Staphylococcus aureus, Streptococcus mutans, Escherichia coli, and Pseudomonas aeruginosa. There were no significant abilities to be reported from the Se-NPs for combating M. tuberculosis H37Rv and M. simiae strains. Based on the results, the nanoparticles displayed stronger antibacterial activities towards the Gram-positive bacteria.

Mycosynthesis and characterization of selenium nanoparticles using standard penicillium chrysogenum PTCC 5031 and their antibacterial activity: A novel approach in microbial nanotechnology

Objective(s): This study deals with mycosynthesis and characterization of selenium nanoparticles (SeNPs) using the Penicillium chrysogenum PTCC 5031 and evaluating their antibacterial activity. Materials and Methods: The formation of SeNPs was confirmed with the color change from pale yellow to orange. Tyndall effect also confirmed the formation of colloidal systems through the samples. The SeNPs were characterized using different analytical techniques including photon correlation spectroscopy (PCS), Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), Energy Dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR) analysis.Results: Our findings revealed that SeNPs were fairly uniformed with good monodispersity and the lesser aggregation of particles in pH value of 7 with the average hydrodynamic size of 24.65 nm, polydispersity index (PdI) of 0.392 and zeta potential of -34 mV. The SeNPs revealed antibacterial activity against gram positive bacteria including Staphylococcus aureus, and Listeria monocytogenes with the zone of inhibition (ZOI) of 10 and 13 mm, respectively. Conclusion: The results of this study provided a potential solution to the growing need for the development of cost-effective and eco-friendly ways of nanoparticle synthesis to overcome the microbial resistance and control the infectious diseases. However, further investigations are required to demonstrate the efficacy of SeNPs through in vivo models.

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Leaf Extract of Dillenia indica as a Source of Selenium Nanoparticles with Larvicidal and Antimicrobial Potential toward Vector Mosquitoes and Pathogenic Microbes

Chikungunya, dengue, Zika, malaria, Japanese encephalitis, filariasis, West Nile, etc. are mosquito transmitted diseases that have killed millions of people worldwide, and millions of people are at risk of these diseases. Control of the mosquitoes, such as Aedes aegypti and Culex quinquefasciatus, is challenging due to their development of resistance to synthetic insecticides. The habitats of the young mosquitoes are also the habitats for foodborne pathogens like Staphylococcus aureus (MTCC96) and Serratia marcescens (MTCC4822). The present study was aimed at synthesizing eco-friendly green nanoparticles using Dillenia indica leaf broth and analyzing its efficacy in controlling the vector mosquitoes A. aegypti and C. quinquefasciatus, as well as the microbial pathogens St. aureus and Se. marcescens. The formation of selenium nanoparticles (SeNps) was confirmed using UV-Vis spectroscopy (absorption peak at 383.00 nm), Fourier transform infrared radiation (FTIR spectrum peaks at 3177, 2114, 1614, 1502, 1340, 1097, 901, 705, and 508 cm−1), X-ray diffraction (diffraction peaks at 23.3 (100), 29.6 (101), 43.5 (012), and 50.05 (201)), and scanning electron microscopy (oval shaped). The size of the nanoparticles and their stability were analyzed using dynamic light scattering (Z-Average value of 248.0 nm) and zeta potential (−13.2 mV). The SeNps disorganized the epithelial layers and have broken the peritrophic membrane. Histopathological changes were also observed in the midgut and caeca regions of the SeNPs treated A. aegypti and C. quinquefasciatus larvae. The SeNps were also active on both the bacterial species showing strong inhibitory zones. The present results will explain the ability of SeNps in controlling the mosquitoes as well as the bacteria and will contribute to the development of multi potent eco-friendly compounds.

A rapid synthesis and antibacterial property of selenium nanoparticles using egg white lysozyme as a stabilizing agent

A simple method for the rapid synthesis of selenium nanoparticles (SeNPs) by the reduction of selenium dioxide using an aqueous egg white lysozyme solution (stabilizing agent) and ascorbic acid solution (reducing agent) has been described. The formation of SeNPs is assured by characterization with UV–Vis, FT-IR, XRD and morphological characters that were observed using TEM analyses. The absorbance of the SeNPs is found at 250 nm. The TEM images show that the SeNPs are uniform and in spherical shape of size 40–60 nm. The crystalline nature of SeNPs is assured by XRD analysis. The antibacterial property of synthesized SeNPs was tested against the pathogenic bacteria, i.e., Bacillus subtilis, Bacillus cereus, Escherichia coli, Staphylococcus pneumoniae, Proteus mirabilis and Klebsiella pneumoniae. SeNPs showed more antibacterial activity against B. subtilis (19 mm) and Streptococcus pneumoniae (15 mm) as compared with commercially available antibiotics such as streptomycin and erythromycin. The SeNPs synthesized via this process has proficient antimicrobial activity against pathogenic bacteria. SeNPs could play a significant role in pharmaceutical industries for the development of efficient antibiotic agents.

Characterization of biogenic selenium nanoparticles derived from cell-free extracts of a novel yeast Magnusiomyces ingens.

A facile one-pot and effective green process for biogenic selenium nanoparticles (SeNPs) was obtained using the cell-free extracts of a novel yeast Magnusiomyces ingens LH-F1. The corresponding absorption peak of SeNPs was observed at ~ 560nm by UV-vis spectrophotometer. In the present study, SeO2 2mM, protein 500mgL-1 and pH 7 were preferable to the biosynthesis of SeNPs. The effects of pH, SeO2 concentration and protein concentration on the synthesis process were different. Transmission electron microscopy image exhibited that all the SeNPs were spherical and quasi-spherical with the diameters mainly distributed in 70-90nm (average particles size was 87.82 ± 2.71nm). X-ray diffraction suggested that the nanoparticles were composed of standard hexagonal crystalline Se with high purity. Fourier transform infrared spectroscopy indicated that some biomolecules such as hydroxyl, carboxyl and amino groups in the yeast cell-free extracts might be involved in the formation of SeNPs. Analyses of sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that two proteins with low molecular weight approximately ~ 16 and ~ 21kDa were detected on the surface of SeNPs and in the extracts, which could play the role of natural stabilizers and confer stability to synthesized SeNPs; whereas, unbound proteins on the SeNPs surface could act as reducing agents. Antibacterial analysis showed that the SeNPs could inhibit Arthrobacter sp. W1 (Gram positive) but not E. coli BL21 (Gram negative), which could provide reference for antimicrobial application of biogenic SeNPs.

Laser Fabrication and Fragmentation of Selenium Nanoparticles in Aqueous Media

The formation of selenium nanoparticles by laser ablation of its target in pure water and water containing biocompatible surfactants has been experimentally investigated. Experiments were performed using three different techniques: ablation in a stationary liquid, ablation in a continuous-flow cell, and laser fragmentation of the obtained mixture of selenium micro- and nanoparticles. The mass and size distribution functions of selenium nanoparticles were determined by sedimentation analysis. A production rate of 20mg min−1 was implemented for selenium nanoparticles. These nanoparticles (less than 100 nm in diameter) were found to be amorphous.

FTIR spectroscopic studies of selenite reduction by cells of the rhizobacterium Azospirillum brasilense Sp7 and the formation of selenium nanoparticles

Microbially driven reduction of selenium oxyanions to elementary selenium, often in the form of nanoparticles (NPs), is widespread in nature. A diversity of possible applications of such biogenic NPs, including those in nanobiotechnology, as well as the specificity of methodologies and mechanisms of their formation via “green synthesis” are very attractive features justifying further studies of the processes of selenium oxyanion bioreduction and the resulting Se0 nanostructures. In this study, live biomass of the rhizobacterium Azospirillum brasilense Sp7 (harvested after the logarithmic growth phase and washed from culture medium components) was used to obtain extracellular Se NPs relatively homogeneous in size (with average diameters within 50–100 nm) in the process of selenite reduction. Both the control cultures of A. brasilense Sp7 and those incubated with SeO32− (producing Se NPs), as well as the resulting separated Se NPs were studied using Fourier transform infrared (FTIR) spectroscopy in the transmission mode (measured as dried layers on a ZnSe disc), in addition to transmission electron microscopy (TEM), to compare metabolic changes in cells and the bioorganic layers associated with the Se NPs. In the control culture (stored for 24 h in physiological saline), FTIR spectroscopic signs of poly-3-hydroxybutyrate (a ‘reserve’ biopolyester) were observed as a response to the lack of nutrients (trophic stress), whereas they were virtually absent in cells incubated for 24 h in physiological saline with 10 mM SeO32− (toxicity stress). FTIR spectra of Se NPs separated from bacterial cells showed bands typical of proteins, polysaccharides and lipids associated with the particles (in line with their TEM images showing a thin layer over the NPs), in addition to strong carboxylate bands, which evidently stabilise the NP structure and morphology.

Impact of microwave irradiation on cyclo-octeno-1,2,3-selenadiazole: formation of selenium nanoparticles and their polymorphs

In this work a one-pot microwave assisted synthesis of selenium nanoparticles and their different forms, by decomposition of cyclo-octeno-1,2,3-selenadiazole is described first ever time.

Reduction of selenite by Azospirillum brasilense with the formation of selenium nanoparticles.

The ability to reduce selenite (SeO(3)(2-)) ions with the formation of selenium nanoparticles was demonstrated in Azospirillum brasilense for the first time. The influence of selenite ions on the growth of A. brasilense Sp7 and Sp245, two widely studied wild-type strains, was investigated. Growth of cultures on both liquid and solid (2 % agar) media in the presence of SeO(3)(2-) was found to be accompanied by the appearance of the typical red colouration. By means of transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS) and X-ray fluorescence analysis (XFA), intracellular accumulation of elementary selenium in the form of nanoparticles (50 to 400 nm in diameter) was demonstrated for both strains. The proposed mechanism of selenite-to-selenium (0) reduction could involve SeO(3)(2-) in the denitrification process, which has been well studied in azospirilla, rather than a selenite detoxification strategy. The results obtained point to the possibility of using Azospirillum strains as endophytic or rhizospheric bacteria to assist phytoremediation of, and cereal cultivation on, selenium-contaminated soils. The ability of A. brasilense to synthesise selenium nanoparticles may be of interest to nanobiotechnology for "green synthesis" of bioavailable amorphous red selenium nanostructures.

Formation of Selenium Nanoparticles in the Selenite-Ascorbate Redox System in Aqueous Solutions of Polyelectrolyte Complexes of Various Compositions

Selenium nanoparticles were synthesized in aqueous solutions of polyelectrolyte complexes of sodium dodecyl sulfate, and the size and morphology of the forming nanostructures were determined.