Imposed Environmental Stresses Facilitate Cell-Free Nanoparticle Formation by Deinococcus radiodurans.
ABSTRACT: The biological synthesis of metal nanoparticles has been examined in a wide range of organisms, due to increased interest in green synthesis and environmental remediation applications involving heavy metal ion contamination. Deinococcus radiodurans is particularly attractive for environmental remediation involving metal reduction, due to its high levels of resistance to radiation and other environmental stresses. However, few studies have thoroughly examined the relationships between environmental stresses and the resulting effects on nanoparticle biosynthesis. In this work, we demonstrate cell-free nanoparticle production and study the effects of metal stressor concentrations and identity, temperature, pH, and oxygenation on the production of extracellular silver nanoparticles by D. radiodurans R1. We also report the synthesis of bimetallic silver and gold nanoparticles following the addition of a metal stressor (silver or gold), highlighting how production of these particles is enabled through the application of environmental stresses. Additionally, we found that both the morphology and size of monometallic and bimetallic nanoparticles were dependent on the environmental stresses imposed on the cells. The nanoparticles produced by D. radiodurans exhibited antimicrobial activity comparable to that of pure silver nanoparticles and displayed catalytic activity comparable to that of pure gold nanoparticles. Overall, we demonstrate that biosynthesized nanoparticle properties can be partially controlled through the tuning of applied environmental stresses, and we provide insight into how their application may affect nanoparticle production in D. radiodurans during bioremediation.IMPORTANCE Biosynthetic production of nanoparticles has recently gained prominence as a solution to rising concerns regarding increased bacterial resistance to antibiotics and a desire for environmentally friendly methods of bioremediation and chemical synthesis. To date, a range of organisms have been utilized for nanoparticle formation. The extremophile D. radiodurans, which can withstand significant environmental stresses and therefore is more robust for metal reduction applications, has yet to be exploited for this purpose. Thus, this work improves our understanding of the impact of environmental stresses on biogenic nanoparticle morphology and composition during metal reduction processes in this organism. This work also contributes to enhancing the controlled synthesis of nanoparticles with specific attributes and functions using biological systems.
Project description:Silver nanoparticles are extensively used due to their chemical and physical properties and promising applications in areas such as medicine and electronics. Controlled synthesis of silver nanoparticles remains a major challenge due to the difficulty in producing long-term stable particles of the same size and shape in aqueous solution. To address this problem, we examine three strategies to stabilise aqueous solutions of 15 nm citrate-reduced silver nanoparticles using organic polymeric capping, bimetallic core-shell and bimetallic alloying. Our results show that these strategies drastically improve nanoparticle stability by distinct mechanisms. Additionally, we report a new role of polymer functionalisation in preventing further uncontrolled nanoparticle growth. For bimetallic nanoparticles, we attribute the presence of a higher valence metal on the surface of the nanoparticle as one of the key factors for improving their long-term stability. Stable silver-based nanoparticles, free of organic solvents, will have great potential for accelerating further environmental and nanotoxicity studies.PACS: 81.07.-b; 81.16.Be; 82.70.Dd.
Project description:Metal nanoparticle synthesis is an interesting area in nanotechnology due to their remarkable optical, magnetic, electrical, catalytic and biomedical properties, but there needs to develop clean, non-toxic and environmental friendly methods for the synthesis and assembly of nanoparticles. Biological agents in the form of microbes have emerged up as efficient candidates for nanoparticle synthesis due to their extreme versatility to synthesize diverse nanoparticles with varying size and shape. In the present study, an eco favorable method for the biosynthesis of silver nanoparticles using marine bacterial isolate has been attempted. Very interestingly, molecular identification proved it as a strain of Ochrobactrum anhtropi. In addition, the isolate was found to have the potential to form silver nanoparticles intracellularly at room temperature within 24 h. The biosynthesized silver nanoparticles were characterized by UV-Vis spectroscopy, transmission electron microscope (TEM) and scanning electron microscope (SEM). The UV-visible spectrum of the aqueous medium containing silver nanoparticles showed a peak at 450 nm corresponding to the plasmon absorbance of silver nanoparticles. The SEM and TEM micrographs revealed that the synthesized silver nanoparticles were spherical in shape with a size range from 38 nm - 85 nm. The silver nanoparticles synthesized by the isolate were also used to explore its antibacterial potential against pathogens like Salmonella Typhi, Salmonella Paratyphi, Vibrio cholerae and Staphylococcus aureus.
Project description:Rapid synthesis of nanomaterials in scalable quantities is critical for accelerating the discovery and commercial translation of nanoscale-based technologies. The synthesis of metal nanogold and silver in volumes larger than 100 mL is not automatized and might require of the use of harsh conditions that in most cases is detrimental for the production of nanoparticles with reproducible size distributions. In this work, we present the development and optimization of an open-access low-cost NanoParticle Flow Synthesis System (NPFloSS) that allows for the rapid preparation of volumes of up to 1 L of gold and silver nanoparticle aqueous solutions.
Project description:The toxicity of silver and zinc oxide nanoparticles is hypothesised to be mediated by dissolved metal ions and cerium dioxide nanoparticles (CeO2 NPs) are hypothesised to induce toxicity specifically by oxidative stress dependant on their surface redox state. To test these hypotheses, RNAseq was applied to characterise the molecular responses of cells to metal nanoparticle and metal ion exposures. The human epithelial lung carcinoma cell line A549 was exposed to different CeO2 NPs with different surface charges, micron-sized and nano-sized silver particles and silver ions, micron-sized and nano-sized zinc oxide particles and zinc ions, or control conditions, for 1 hour, 6 hours and 24 hours. Concentrations were the lower of either EC20 or 128 micrograms/mL. Transcriptional responses were characterised by RNAseq transcriptomics using an Illumina HiSeq2500 .
Project description:Microorganisms offer an alternative green and scalable technology for the synthesis of value added products. Fungi secrete high quantities of bioactive substances, which play dual-functional roles as both reducing and stabilizing agents in the synthesis of colloidal metal nanoparticles such as silver nanoparticles, which display potent antimicrobial properties that can be harnessed for a number of industrial applications. The aim of this work was the production of silver nanoparticles using the extracellular cell free extracts of Phanerochaete chrysosporium, and to evaluate their activity as antimicrobial and antibiofilm agents. The 45-nm diameter silver nanoparticles synthesized using this methodology possessed a high negative surface charge close to -30 mV and showed colloidal stability from pH 3-9 and under conditions of high ionic strength ([NaCl] = 10-500 mM). A combination of environmental SEM, TEM, and confocal Raman microscopy was used to study the nanoparticle-E. coli interactions to gain a first insight into their antimicrobial mechanisms. Raman data demonstrate a significant decrease in the fatty acid content of E. coli cells, which suggests a loss of the cell membrane integrity after exposure to the PchNPs, which is also commensurate with ESEM and TEM images. Additionally, these biogenic PchNPs displayed biofilm disruption activity for the eradication of E. coli and C. albicans biofilms.
Project description:In this study, the metallothionein gene of Candida albicans (C. albicans) was assembled by polymerase chain reaction (PCR), inserted into pUC19 vector, and further transformed into Escherichia coli (E. coli) DH5? cells. The capacity of these recombinant E. coli DH5? cells to synthesize silver nanoparticles was examined. Our results demonstrated that the expression of C. albicans metallothionein in E. coli promoted the bacterial tolerance to metal ions and increased yield of silver nanoparticle synthesis. The compositional and morphological analysis of the silver nanoparticles revealed that silver nanoparticles synthesized by the engineered E. coli cells are around 20 nm in size, and spherical in shape. Importantly, the silver nanoparticles produced by the engineered cells were more homogeneous in shape and size than those produced by bacteria lack of the C. albicans metallothionein. Our study provided preliminary information for further development of the engineered E. coli as a platform for large-scale production of uniform nanoparticles for various applications in nanotechnology.
Project description:Plant extract of Pulicaria undulata (L.) was used as both reducing agent and stabilizing ligand for the rapid and green synthesis of gold (Au), silver (Ag), and gold-silver (Au-Ag) bimetallic (phase segregated/alloy) nanoparticles (NPs). These nanoparticles with different morphologies were prepared in two hours by stirring corresponding metal precursors in the aqueous solution of the plant extracts at ambient temperature. To infer the role of concentration of plant extract on the composition and morphology of NPs, we designed two different sets of experiments, namely (i) low concentration (LC) and (ii) high concentration (HC) of plant extract. In the case of using low concentration of the plant extract, irregular shaped Au, Ag, or phase segregated Au-Ag bimetallic NPs were obtained, whereas the use of higher concentrations of the plant extract resulted in the formation of spherical Au, Ag, and Au-Ag alloy NPs. The as-prepared Au, Ag, and Au-Ag bimetallic NPs showed morphology and composition dependent catalytic activity for the reduction of 4-nitrophenol (4-NPh) to 4-aminophenol (4-APh) in the presence of NaBH4. The bimetallic Au-Ag alloy NPs showed the highest catalytic activity compared to all other NPs.
Project description:Different functions were imparted to ramie fibers through treatment with noble metal nanoparticles including silver and gold nanoparticles. The in situ synthesis of silver and gold nanoparticles was achieved by heating in the presence of ramie fibers in the corresponding solutions of precursors. The unique optical property of synthesized noble metal nanoparticles, i.e., localized surface plasmon resonance, endowed ramie fibers with bright colors. Color strength (K/S) of fibers increased with heating temperature. Silver nanoparticles were obtained in alkaline solution, while acidic condition was conducive to gold nanoparticles. The optical properties of treated ramie fibers were investigated using UV-vis absorption spectroscopy. Scanning electron microscopy (SEM) was employed to observe the morphologies of silver and gold nanoparticles in situ synthesized on fibers. The ramie fibers treated with noble metal nanoparticles showed remarkable catalytic activity for reduction of 4-nitrophenol (4-NP) by sodium borohydride. Moreover, the silver nanoparticle treatment showed significant antibacterial property on ramie fibers.
Project description:Biological synthesis of silver nanoparticles using microorganisms has received profound interest because of their potential to synthesize nanoparticles of various size, shape and morphology. In the current study, synthesis of silver nanoparticles by a bacterial strain (CS 11) isolated from heavy metal contaminated soil is reported. Molecular identification of the isolate showed it as a strain of Bacillus sp. On treating the bacteria with 1 mM AgNO3, it was found to have the ability to form silver nanoparticles extracellularly at room temperature within 24 h. This was confirmed by the visual observation and UV-Vis absorption at 450 nm. Further characterization of nanoparticles by transmission electron microscopy confirmed the size of silver nanoparticles in 42-92 nm range. Therefore, the current study is a demonstration of an efficient synthesis of stable silver nanoparticle by a Bacillus strain.
Project description:From the result of the gene expression analyses of human hepatoma cell line, HepG2, a number of genes associated with cell proliferation and DNA repair were distinctively up-regulated by Ag-nanoparticle exposure, suggesting that Ag-nanoparticles might stimulate cell proliferation and DNA damage, which are considered to be mechanisms playing an important role for carcinogenesis and tumor progression. The inductions of these genes involved in cell proliferation were also observed in PS-nanoparticles and Ag2CO3-exposed cells. In addition, the inductions of DNA repair-associated genes were also observed in Ag2CO3-exposure. These results suggest that both “nanoshape” and “silver” can cause the inductions of these gene expression patterns. Furthermore, cysteine, a strong ionic silver ligand partially abolished these gene expressions induced by silver nanoparticles. Ionic silver sourced from Ag-nanoparticles could not fully explain these gene expressions. Overall design: In this study, we examined the gene expression alteration in human hepatoma cell line, HepG2 following exposures of silver nanoparticles (7-10 nm), polysthylene nanoparticles (15 nm) and silver carbonate using DNA microarray with 8795 human genes. Furthermore, we also performed the DNA microarray analyses for the cells exposed to silver nanoparticle in the presence of 5mM N-acetyl-L-cysteine to examine the contribution of silver ion to silver nanoparticle exposure.