Synthesis and characterization of silver cluster particles in hydrogels

2015 ◽  
Vol 35 (4) ◽  
pp. 303-309
Author(s):  
Aman Deo ◽  
Syed Sauban Ghani
Keyword(s):  
Silver Cluster ◽  
Maximum Size ◽  
Spectrophotometric Analysis ◽  
E Coli ◽  
Hydrogel Network ◽  
Microscopy Analysis ◽  
Antibacterial Material ◽  
Spectroscopy Studies

Abstract A chitosan-based hydrogel network was crosslinked with genipin; the crosslinked and uncrosslinked hydrogels were prepared and studied. Uniformly distributed silver cluster particles (AgCPs) were prepared using these hydrogel networks as a carrier via in situ reduction of silver nitrate (AgNO3) in the presence of sodium borohydride (NaBH4) as a reducing agent; UV irradiation reduction was also done. Fourier transform infrared (FTIR) spectroscopy studies of the hydrogels gave results on the decree of crosslinking and some indication on the presence of the AgCPs. The spectrophotometric analysis indicated the presence of AgCPs, as a peak appeared around 400 nm. The microscopy analysis gave images of the presence of AgCPs and their size; it showed that the crosslinked hydrogels have uniformly distributed AgCPs and as the crosslinking increased, the AgCPs size decreased. The studies on the increasing concentration of AgNO3 solution gave an increase AgCPs size; the maximum size of AgCPs clusters was ∼0.2 micron in uncrosslinked chitosan. It was demonstrated, by using Escherichia coli (E. coli) bacterium, that the AgCPs hydrogel can be effectively employed as antibacterial material.

scholarly journals Electrospun Nanofibrous Poly(3-Hydroxybutyrate-Co-3-Hydroxyvalerate) With Antibacterial Activity

2019 ◽  
pp. 1-7
Author(s):  
Samir Abbad Andaloussi ◽  
Davy Louis Versace ◽  
Estelle Renard ◽  
Etienne Dessauw ◽  
Valerie Langlois
Keyword(s):  
Antiradical Activity ◽  
Layered Materials ◽  
Antibacterial Activities ◽  
E Coli ◽  
Cyclodextrin Inclusion Complexes ◽  
Cyclodextrin Inclusion ◽  
Electron Microscopy Analysis ◽  
Microscopy Analysis ◽  
Antibacterial Material ◽  
Scanning Electron

Elaboration of electrospun nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV)-based mats was implemented through two routes to obtain antibacterial material containing carvacrol, a phenolic compound extracted from essential oils. The first strategy relied on a direct blend of PHBHV and carvacrol/-cyclodextrin inclusion complexes, PHBHV (carvCD-IC), while the second approach implied the elaboration of multilayered scaffold via the introduction of poly(β-CD-epichlorohydrin), PolyCD. The PolyCD/carv-based mat was electrospun between two hydrophobic PHBHV mats. Scanning Electron Microscopy analysis of mats showed uniform and beadless fibers. The three layered materials [PHBHV-(PolyCD/carv)-PHBHV] is sufficient to ensure optimal antiradical activity (RSA of 88.6%) and exhibit interesting antibacterial activities against E. coli and S. aureus.

Antibacterial Activity of Surface-Modified Fabric with Ag/AgCl-Doped Quaternary Ammonium-Modified Silicate Hybrid

2019 ◽  
Vol 19 (11) ◽  
pp. 7285-7293 ◽  
Author(s):  
Kuo-Hui Wu ◽  
Yin-Chiung Chang ◽  
Ken-Fa Cheng ◽  
Je-Chuang Wang
Keyword(s):  
Colloidal Suspension ◽  
Sol Gel ◽  
Antimicrobial Properties ◽  
Woven Fabrics ◽  
Dipolar Interactions ◽  
Zone Of Inhibition ◽  
E Coli ◽  
Antibacterial Material ◽  
Surface Modified

An organic–inorganic hybrid antibacterial material based on Ag/AgCl and quaternary ammoniummodified silicate (Ormosil (NR+4 Cl-)) was prepared by sol–gel processes and an in situ reduction method, in which silver nitrate, tetraethoxysilane (TEOS), N-trimethoxysilylpropyl-N,N,Ntrimethylammonium chloride (TMAPS) and N-[3-(trimethoxysilyl)propyl]diethylenetriamine (ATS) acted as precursor, linker and colloidal suspension stabilizer, respectively. The physical properties of the Ormosil (NR+4 Cl-) and Ormosil (NR+4 Cl-)/Ag hybrids were examined using XPS and TGA spectroscopy, the results of which indicated that Ag/AgCl was immobilized in channels by dipolar interactions with the Ormosil (NR+4 Cl-) matrix. Ormosil (NR+4 Cl-) and Ormosil (NR+4 Cl-)/Ag sol solutions were used to functionalize non-woven fabrics by simply immersing the textiles into the dispersions in order to obtain antimicrobial fabrics. The antibacterial effects of the Ormosil/Ag- and Ormosil (NR+4 Cl-)/Ag-modified fabrics against Gram-negative P. aeruginosa and E. coli, and Grampositive S. aureus and B. subtilis, were assessed using the zone of inhibition and the plate-counting method. The antibacterial efficacy was maintained even after 20 laundry cycles. The results indicated that the Ormosil/Ag and Ormosil (NR+4 Cl-)/Ag hybrids are useful as non-leaching agents imparting durable antimicrobial properties to fabrics.

scholarly journals Rheological Characterization of Hydrogels from Alginate-Based Nanodispersion

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 259 ◽  
Author(s):  
Francesca Cuomo ◽  
Martina Cofelice ◽  
Francesco Lopez
Keyword(s):  
Essential Oil ◽  
Tween 80 ◽  
Creep Recovery ◽  
Ion Release ◽  
Rheological Characterization ◽  
Burger Model ◽  
Food Industries ◽  
Hydrogel Network

The interest toward alginate and nanoemulsion-based hydrogels is driven by the wide potential of application. These systems have been noticed in several areas, ranging from pharmaceutical, medical, coating, and food industries. In this investigation, hydrogels prepared through in situ calcium ion release, starting from lemongrass essential oil nanodispersions stabilized in alginate aqueous suspensions in the presence of the nonionic surfactant Tween 80, were evaluated. The hydrogels prepared at different concentrations of oil, alginate, and calcium were characterized through rheological tests. Flow curves demonstrate that the hydrogels share shear thinning behavior. Oscillatory tests showed that the strength of the hydrogel network increases with the crosslinker increase, and decreases at low polymer concentrations. The hydrogels were thixotropic materials with a slow time of structural restoration after breakage. Finally, by analyzing the creep recovery data, the hydrogel responses were all fitted to the Burger model. Overall, it was demonstrated that the presence of essential oil in the proposed hydrogels does not affect the mechanical characteristics of the materials, which are mainly influenced by the concentration of polymer and calcium as a crosslinker.

scholarly journals Fabrication and Characterization of In Situ Synthesized SiC/Al Composites by Combustion Synthesis and Hot Press Consolidation Method

Scanning ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Hongyu Yang ◽  
Erting Dong ◽  
Bingqi Zhang ◽  
Yanyan Yuan ◽  
Shili Shu
Keyword(s):  
Combustion Synthesis ◽  
Maximum Size ◽  
Holding Time ◽  
Mass Ratio ◽  
Hot Press ◽  
Uniform Size ◽  
Average Hardness ◽  
Sic Particles

The in situ SiC/Al composites were fabricated in Al-Si-C systems with different Si/C mass ratios and holding time by the method of combustion synthesis and hot press consolidation. The influences of Si/C mass ratio and holding time on the phase constitution, microstructure, and hardness of the composites were investigated. The results indicate that the increase of Si/C mass ratio leads to more uniform size distribution of the SiC particles in the Al matrix. Moreover, by improving the Si/C mass ratio from 4 : 1 to 5 : 1, the maximum size of SiC particle was reduced from 4.1 μm to 2.0 μm. Meanwhile, the percentage of submicroparticles was increased from 22% to 63%, and the average hardness value of the composites was increased by 13%. In addition, when the holding time is set to be fifteen minutes, the Al4C3 phase did not exist in the composites because of its total reactions with Si atoms to form SiC particles, and the average hardness value was 73.8 HB.

scholarly journals In situ genotyping of a pooled strain library after characterizing complex phenotypes

2017 ◽  
Author(s):  
Michael J. Lawson ◽  
Daniel Camsund ◽  
Jimmy Larsson ◽  
Özden Baltekin ◽  
David Fange ◽  
...  
Keyword(s):  
Fluorescence Imaging ◽  
Single Molecule ◽  
Single Molecule Fluorescence ◽  
Detailed Characterization ◽  
E Coli ◽  
Complex Phenotypes

So far, it has not been possible to perform advanced microscopy on pool generated strain libraries and at the same time know each strain’s genotype. We have overcome this barrier by identifying the genotypes for individual cells in situ after a detailed characterization of the phenotype. The principle is demonstrated by single molecule fluorescence imaging of E. coli strains harboring barcoded plasmids that express a sgRNA which suppress different genes through dCas9.

scholarly journals Preparation and Characterization of Chitosan Nanocomposite Based on Nanoscale Silver and Nanomontmorillonite

2019 ◽  
Vol 2 (2) ◽  
pp. 5-12 ◽  
Author(s):  
Fatemeh- Sadat Ebnerasool ◽  
Negar Motakef Kazemi
Keyword(s):  
Food Packaging ◽  
Solution Method ◽  
In Situ Synthesis ◽  
Diffusion Method ◽  
X Ray ◽  
E Coli ◽  
Packaging Industry ◽  
Scanning Electron

The chitosan nanocomposites were rapidly prepared by simple solution method. This biopolymer matrix was modified by prepared nanoscale silver (Ag) using in situ synthesis from precursor and nanomontmorillonite (NMMT). The samples were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), and energy dispersive x-ray spectroscopy (EDX). The water vapor properties (WVP) of nanocomposites were investigated using gravimetric standard. The antibacterial activity of nanocomposite was measured by the well diffusion method on Muller–Hinton Agar against Escherichia coli (E. coli) by zone inhibition. Based on the obtained results, the nanocomposite can have a good candidate for different applications and food packaging industry.

scholarly journals Infrared Characterization of the Bidirectional Oxygen-Sensitive [Nife]-Hydrogenase from E. Coli

2018 ◽  
Author(s):  
Moritz Senger ◽  
Konstanin Laun ◽  
Basem Soboh ◽  
Sven Timo Stripp
Keyword(s):  
Escherichia Coli ◽  
Green Chemistry ◽  
Ftir Spectroscopy ◽  
Biological Macromolecules ◽  
E Coli ◽  
Gas Processing ◽  
H2 Generation ◽  
Oxygen Sensitive

[NiFe]-hydrogenases are gas-processing metalloenzymes that catalyze the conversion of dihydrogen (H2) to protons and electrons in a broad range of microorganisms. Within the framework of green chemistry, the molecular proceedings of biological hydrogen turnover inspired the design of novel catalytic compounds for H2 generation. The bidirectional “O2-sensitive” [NiFe]-hydrogenase from Escherichia coli HYD-2 has recently been crystallized; however, a systematic infrared characterization in the presence of natural reactants is not available yet. In this study, we analyze HYD-2 from E. coli by in situ ATR FTIR spectroscopy under quantitative gas control. We provide an experimental assignment of all catalytically relevant redox intermediates alongside the O2- and CO-inhibited cofactor species. Furthermore, the reactivity and mutual competition between H2, O2, and CO was probed in real time, which lays the foundation for a comparison with other enzymes, e.g., “O2-tolerant” [NiFe]-hydrogenases. Surprisingly, only Ni-B was observed in the presence of O2 with no indications for the “unready” Ni-A state. The presented work proves the capabilities of in situ ATR FTIR spectroscopy as an efficient and powerful technique for the analysis of biological macromolecules and enzymatic small molecule catalysis.

scholarly journals In Situ Characterization of Mycobacterial Growth Inhibition by Lytic Enzymes Expressed in Vectorized E. coli

2014 ◽  
Vol 3 (12) ◽  
pp. 932-934 ◽  
Author(s):  
Iva Atanaskovic ◽  
Amel Camélia Bencherif ◽  
Matthew Deyell ◽  
Sebastián Jaramillo-Riveri ◽  
Marguerite Benony ◽  
...  
Keyword(s):  
Growth Inhibition ◽  
Lytic Enzymes ◽  
In Situ Characterization ◽  
E Coli ◽  
Mycobacterial Growth

scholarly journals Truncation of poly-N-acetylglucosamine (PNAG) polymerization with N-acetylglucosamine analogues

2021 ◽  
Author(s):  
Zachary Morrison ◽  
Alexander Eddenden ◽  
Adithya S Subramanian ◽  
P. Lynne Howell ◽  
mark nitz
Keyword(s):  
Biofilm Formation ◽  
Chain Termination ◽  
Salvage Pathway ◽  
Biofilm Inhibition ◽  
E Coli ◽  
Substrate Analogues

Bacteria require polysaccharides for structure, survival, and virulence. Despite the central role these structures play in microbiology few tools are available to manipulate their production. In E. coli the glycosyltransferase complex PgaCD produces poly-N-acetylglucosamine (PNAG), an extracellular matrix polysaccharide required for biofilm formation. We report that C6-substituted (H, F, N3, SH, NH2) UDP-GlcNAc substrate analogues are inhibitors of PgaCD. In vitro the inhibitors cause PNAG chain termination; consistent with the mechanism of PNAG polymerization from the non-reducing terminus. In vivo, expression of the GlcNAc-1-kinase NahK in E. coli provided a non-native GlcNAc salvage pathway that produced the UDP-GlcNAc analogue inhibitors in situ. The 6-fluoro and 6-deoxy derivatives were potent inhibitors of biofilm formation in the transformed strain, providing a tool to manipulate this key exopolysaccharide. Characterization of the UDP-GlcNAc pool and quantification of PNAG generation support PNAG termination as the primary in vivo mechanism of biofilm inhibition by 6-fluoro UDP-GlcNAc.

scholarly journals The mechanoelectrical response of the cytoplasmic membrane of Vibrio cholerae

2013 ◽  
Vol 142 (1) ◽  
pp. 75-85 ◽  
Author(s):  
Ian Rowe ◽  
Merina Elahi ◽  
Anwar Huq ◽  
Sergei Sukharev
Keyword(s):  
Vibrio Cholerae ◽  
Cytoplasmic Membrane ◽  
Mechanosensitive Channel ◽  
Inward Rectification ◽  
Electrogenic Transport ◽  
E Coli ◽  
Esherichia Coli ◽  
Membrane Components

Persistence of Vibrio cholerae in waters of fluctuating salinity relies on the capacity of this facultative enteric pathogen to adapt to varying osmotic conditions. In an event of osmotic downshift, osmolytes accumulated inside the bacterium can be quickly released through tension-activated channels. With the newly established procedure of giant spheroplast preparation from V. cholerae, we performed the first patch-clamp characterization of its cytoplasmic membrane and compared tension-activated currents with those in Esherichia coli. Saturating pressure ramps revealed two waves of activation belonging to the ∼1-nS mechanosensitive channel of small conductance (MscS)-like channels and ∼3-nS mechanosensitive channel of large conductance (MscL)-like channels, with a pressure midpoint ratio p0.5MscS/p0.5MscL of 0.48. We found that MscL-like channels in V. cholerae present at a density three times higher than in E. coli, and yet, these vibrios were less tolerant to large osmotic downshocks. The Vibrio MscS-like channels exhibit characteristic inward rectification and subconductive states at depolarizing voltages; they also adapt and inactivate at subsaturating tensions and recover within 2 s upon tension release, just like E. coli MscS. Trehalose, a compatible internal osmolyte accumulated under hypertonic conditions, significantly shifts activation curves of both MscL- and MscS-like channels toward higher tensions, yet does not freely partition into the channel pore. Direct electrophysiology of V. cholerae offers new avenues for the in situ analysis of membrane components critical for osmotic survival and electrogenic transport in this pathogen.

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