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PubMed1997

Dual silver staining to characterise Helicobacter spp. outer membrane components.

Helicobacter pylori is a bacterial pathogen, estimated to infect half the world's population. The bacterium is the aetiological cause of gastritis, the common precursor for peptic ulcer disease and gastric cancer. Immunisation of at-risk individuals is the most cost-effective means of dealing with such a widespread pathogen. Potential vaccine candidates need to be identified and characterised. Conventional silver staining is commonly used for the sensitive detection of bacterial protein components separated by SDS-PAGE. Modified silver stains employing periodate oxidation have also been developed for the analysis of purified bacterial lipopolysaccharide. By using these methods in parallel, as a dual silver stain, bacterial fractions can be characterised in terms of protein and LPS content. Strain differences can also be readily identified by comparing protein and LPS profiles. When combined with differential immunoblotting, the dual silver stain is a useful analytical tool for characterising potential vaccine candidate antigens.

Animals↗

PubMed1991

Corrosion pattern of silver points in vivo.

The purpose of this study was to examine the electrochemical behavior of silver points in vivo. The apices of silver points removed from teeth with successful or failed endodontic treatments were subjected to complete surface characterization by small-area ESCA, scanning electron microscopy, and electron probe microanalyzer. Cross-sections of the points near the apex were examined with scanning electron microscopy and electron probe microanalyzer to identify the depth of corrosion involvement. According to the results, all silver points manifested evidence of corrosion attack. Electron probe microanalyzer showed no difference in the elemental distribution found on the points. ESCA analysis of the uppermost 5-nm point layer revealed the presence of N on silver points removed from failed treatments. The examination of cross-sections manifested deep S penetration in the bulk of the points removed from failed treatments. Considering the results of this study, no direct association seems to exist between the extent of the corrosion involvement and the prognosis of the treatment. Handling factors and the presence of bacteria are probably the parameters determining the outcome of a treatment.

Corrosion↗

PubMed1989

Unusual case of silver cone disintegration.

An unusual case of silver cone disintegration associated with progressive root resorption is reported. The use of the scanning electron microscope and the electron microprobe provided evidence of different states of corrosion in two remaining silver cones. Light microscopic examination showed the presence of silver particles apparently released from the disintegrated or progressively corroded cones in the surrounding tissues. The possible interaction between such silver accumulations or their chemical combinations with other elements and the tissue is discussed.

Corrosion↗

PubMed2000

Silver stained polyacrylamide gels and fluorescence-based automated capillary electrophoresis for detection of amplified fragment length polymorphism patterns obtained from white-rot fungi in the genus Trametes.

Silver stained denaturing polyacrylamide gels (PAGEs) and fluorescent denaturing automated capillary electrophoresis (CE) were used to detect amplified fragment length polymorphism (AFLP) patterns obtained from white-rot fungi belonging to the genus Trametes. AFLP fingerprinting detected by the fluorescence-based method as well as by silver staining showed a high discriminatory power in differentiating nine strains of Trametes ochracea, nine strains of Trametes hirsuta and ten isolates of Trametes versicolor. UPGMA dendrograms derived from fluorescently labelled and silver stained AFLP patterns were similar, but a few differences were detected especially in the clustering of T. ochracea and T. hirsuta strains. Compared to silver-stained AFLP, detection of fluorescent AFLP was fast, reliable and easy to perform and it facilitated surveying with a computerized analysis system. Fluorescent CE seems to be well suited for studying similarity between Trametes species.

Basidiomycota↗

PubMed2003

Silver nitrate cauterization: characterization of a new model of corneal inflammation and hyperalgesia in rat.

Chemical cauterization of the central cornea with silver nitrate was assessed as a superficial injury model of tissue sensitization accompanying acute inflammation. Adult male Sprague-Dawley rats were anesthetized with halothane gas, and the centers of their right corneas treated with a silver nitrate applicator stick (75% silver nitrate, 25% potassium nitrate) to produce a discrete lesion 1 mm in diameter. Edema of the corneal stroma and elevated immune cell counts became significant 4 h after cauterization, and were still evident after 48 h. Behavioral sensitization to chemical stimuli was determined by counting the number of blinks following application of 1 microM capsaicin directly to the corneal surface. A significant increase in stimulus-induced blinking was evident 2 h after cauterization. Chemical sensitization peaked at 6 h, and was no longer significant at 12 h. We conclude that silver nitrate cauterization produces acute corneal inflammation and hyperalgesia, and may prove a useful model for the study of primary afferent nociceptors.

Animals↗

PubMed2004

The role of Acticoat with nanocrystalline silver in the management of burns.

Silver is an effective antimicrobial agent, but older silver-containing formulations are rapidly inactivated by the wound environment, requiring frequent replenishment. These older formulations may also be pro-inflammatory and may delay healing. Acticoat (Smith & Nephew, Hull, UK) is a relatively new form of silver antimicrobial barrier dressing which helps avoid the problems of earlier agents. It has rapid and sustained bactericidal activity, and because of this may reduce inflammation and promote healing. Despite extensive testing and clinical experience, no evidence has emerged of resistance or cytotoxicity to nanocrystalline silver. This article collects together a number of presentations that were given at the 2003 European Burns Association Meeting on the use of Acticoat in the management of burns.

Anti-Bacterial Agents↗

PubMed1995

Prevention of catheter-related infections by silver coated central venous catheters in oncological patients.

Catheter-related infection (CRI) is a serious complication of central venous catheterization. We have investigated the efficacy of a silver-coated polyurethane catheter (Pellethane, Fresenius AG, Germany) in preventing CRI in oncological patients receiving chemotherapy in a phase II study. From November 1992 through April 1994, 266 patients were assigned to receive single lumen catheters, either standard uncoated catheters (UC, n = 113) or silver-coated ones (SC, n = 120). Catheters were inserted into the internal jugular vein after institutional approval and informed consent. Duration of catheterization (UC vs. SC = 13.3 vs. 12.7 days) and leukopenia (< 1.0 x 10(9) WBC/l; 4.3 vs. 3.6 days) were similar in both groups demonstrating a comparable risk for infections. Skin reactions at the catheter entry site were recorded daily. CRI and colonization rates were studied by semiquantitatively culturing intradermal and intravascular segments. CRI were confirmed by blood cultures obtained via catheter and from peripheral veins in cases of suspected sepsis or at the end of catheterization. No adverse effects from the silver-coated catheter could be observed. The bacteriological results showed that SC were colonized (> 15 CFU) in 45.1% and UC in 44.2%. CRI developed in 21.2% of the UC patients but only in 10.2% of the SC patients (p = 0.011). We conclude that this new silver-coated central venous catheter is biocompatible and effective in reducing the incidence of catheter-related infections in oncological patients.

Adolescent↗

PubMed2003

Silver nanoparticle enhanced immunoassays: one step real time kinetic assay for insulin in serum.

Silver nanoparticle enhanced fluorescence is introduced as an alternative method to surface plasmon resonance techniques for real time monitoring of biorecognitive interactions or immunoassays. This method relies on the phenomenon that an electromagnetic near field is generated upon illumination on the surface of silver nanoparticles. The interaction of this field with nearby fluorophores results in fluorescence enhancement. Thus, fluorophores in the bulk solution can be discriminated from surface bound fluorophores. Anti-insulin-antibodies were immobilized on the surface of silver colloids in the following order: A ready to use microplate was prepared by bottom up coating with layers of aminosilane, silver nanoparticles, Fc-recognizing F(ab)(2)-fragments and anti-insulin-antibodies. At equilibrium conditions fluorescein-labeled insulin could only be detected in the presence of the colloid; the detection limit was 250 nM, and a fourfold increase in fluorescence was observed upon real time monitoring. The competitive assay of labeled and unlabeled insulin revealed a working range of 10-200 nM insulin in serum. The rapid single step immunoassay is easy to perform even in microplate format, its sensitivity is comparable to ELISA techniques, and offers broad application for real time monitoring of molecular recognitive processes.

Humans↗

PubMed2003

Peculiar features of the aggregation effect of silver(I) ion on hemoglobin.

Silver(I) ion has been shown to produce aggregation effect on bovine oxyhemoglobin (HbO(2)) in Tris buffer even when taken in amounts corresponding to only two or less silver ions per one HbO(2) tetramer. The extent of produced effect is comparable to those previously observed for Hg(II), Cd, Zn, and Ni in spite of significantly different electronic configurations of the ions in question. Aggregation effect of the silver is ascribed to an interaction of the reactive thiol group sulfur-bound silver atom with the carboxylate residues surrounding the reactive thiol group-bearing cysteine beta93 group of hemoglobin. Mercury ligands, in particular, Tris molecules and OH(-) anions markedly suppress the protein coagulation, thereby supporting the proposed protein aggregation mechanism.

Animals↗

PubMed1991

Corrosion and fracture of a silver tracheostomy tube.

A sterling silver tracheostomy tube broke in use resulting in the death of a child. The nature of the fracture in the brazed joint is described, and corrosion identified as the mechanism of degradation of the joint. The corrosion is due either to exposure to body fluids over a long period, or to the use of hypochlorite solutions for cleaning and disinfection. The silver braze used had inferior corrosion resistance. It is recommended that appropriate grades of silver brazing alloy be used in the future, and that the mechanical integrity of medical devices joined with silver braze be regularly checked to anticipate failure in use.

Alloys↗

PubMed2005

Fiber-optic microsensor array based on fluorescent bulk optode microspheres for the trace analysis of silver ions.

An optical microsensor array is described for the rapid analysis of silver ions at low parts per trillion levels. Because the ionophore o-xylylenebis(N,N-diisobutyldithiocarbamate) (Cu-I) was reevaluated and shown to exhibit excellent selectivity for silver ions, ion-selective electrode (ISE) membranes were optimized and found to exhibit the lowest reported detection limit so far (3 x 10(-10) M). A corresponding Ag+-selective fluorescent optical microsensor array for the rapid sensing of trace level Ag+ was then developed. It was fabricated using plasticized PVC-based micrometer-scale fluorescent microspheres that were produced via a sonic particle casting device. They contained 156 mmol/kg Cu-I, 10 mmol/kg 9-(diethylamino)-5-[4-(15-butyl-1,13-dioxo-2,14-dioxanodecyl) phenylimino]benzo[a]phenoxazine (chromoionophore VII, ETH 5418), 2.3 mmol/kg 1,1' '-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (internal reference dye), and 14 mmol/kg sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate and were deposited onto the etched distal end of a 3200-microm-diameter optical fiber bundle. The microarray was characterized by fluorescence spectroscopy in samples containing 10(-12)-10(-8) M AgNO3 at pH 7.4, with selectivity characteristics comparable to the corresponding ISEs. The response time of the microsensor array was found to be less than 15 min for 10(-9) M AgNO3, which is drastically shorter than earlier data on optode films (8 h) and corresponding ISEs (30 min). A detection limit of 4 x 10(-11) M for Ag+ was observed, lower than any previously reported optode or silver-selective ISE. The microsensor array was applied for measurement of free silver levels in buffered pond water samples.

Calibration↗

PubMed1993

Copper- and silver-substituted yeast metallothioneins: sequential 1H NMR assignments reflecting conformational heterogeneity at the C terminus.

Complete 1H NMR sequential assignments have been made for copper(I)- and silver (I)-substituted metallothionein (MT) from Saccharomyces cerevisiae using standard 2D 1H NMR methods. The fingerprint region of the COSY spectrum of both metalloproteins shows a doubling of a few backbone proton resonances from residue K41 onward in the C terminus. This doubling of resonances is absent in the spectrum of the truncated mutant protein that lacks the five C-terminal residues which includes two cysteines. Concurrently, it has been established from a comparison of the heteronuclear 1H-109 Ag multiple-quantum coherence transfer (HMQC) spectrum on the silver-substituted mutant and the wild-type protein that metal ligation is similar in both molecules. Thus, the 2 C-terminal Cys are not essential for metal cluster formation in the wild-type yeast MT and only 10 of the 12 Cys present in this protein appear to be involved in ligating the 7 mol of bound metal ions. A qualitative analysis of the coupling constant, hydrogen exchange, and NOE data indicates the presence of many type I beta-turns and the lack of any other regular secondary structural elements. A comparison of chemical shifts and NOE data for native copper- and silver-substituted yeast MT indicates a high degree of conservation of structural elements in both proteins. Therefore, it seems reasonable to conclude that the metal to Cys connectivities which are obtained directly from the HMQC data on silver-substituted metallothionein are conserved in the native copper protein. Interestingly, a mixture of both 2 and 3 coordination was found for the bound Ag(I) ions in a single Ag7Cys10 cluster. This mixed coordination number and a single cluster arrangement is most probably also shared with the Cu(I) ion coordination in the native protein.

Amino Acid Sequence↗

PubMed2006

Effect of intracellular resuscitation of Legionella pneumophila in Acanthamoeba polyphage cells on the antimicrobial properties of silver and copper.

The property of Legionella pneumophila entering into a viable but noncultivable (VBNC) state under drinking water conditions (50 mL, pH 7.0, and 25 degrees C) and the intracellular resuscitation in Acanthamoeba polyphage cells were investigated. Then, the survival profiles of L. pneumophila residing in the planktonic phase and the endosymbiosis phase against antimicrobial silver and copper reagents were differentially compared with the case of Pseudomonas aeruginosa. The number of L. pneumophila in a cultivable state was rapidly reduced to below the detection limit (5.0 log reduction) within 30 days of incubation in synthetic drinking water, while the number of L. pneumophila in a viable state varied in only 0.1 log reduction during the same period, and the levels were sustained constantly for 190 days; in contrast, P. aeruginosa multiplied even in drinking water and continuously maintained its cultivability and viabilityfor 190 days. Distinctively, the numbers of E. coli in both cultivable and viable states were simultaneously diminished as 3.0 log and 1.6 log reduction. The cultivability of L. pneumophila in the VBNC state was recovered and started to multiply after coincubation with A. polyphage in the same environment (initial population of inoculated amoeba was adjusted as 1.0 x 10(5) amoeba/ mL), and P. aeruginosa also multiplied in amoeba cells. Finally, the populations of L. pneumophila in the planktonic phase after 10 days coincubation were detected at 1.7 x 10(7) CFU/mL, and this population was considered to have originated from the release of bacteria residing inside amoeba caused by the destruction of amoeba cells. Bacteria in the planktonic phase that were exposed to silver and copper were completely inactivated (more than 7 log reduction) within 30 min, while bacteria in the endosymbiosis phase showed much higher resistance against the exposure to the same concentrations of silver and copper. L. pneumophila and P. aeruginosa in A. polyphage cells survived to levels of 5.6 x 10(1) and 1.1 x 10(1) CFU/mL at the silver exposure (0.1 mgAg/L) and 7.3 x 10(3) and 6.1 x 10(4) CFU/ mL at the copper exposure (1.0 mgCu/L), respectively, after 7 days.

Acanthamoeba↗

PubMed2001

Crystal and solution structures of N,N-dimethylthioformamide-solvated copper(I), silver(I), and gold(I) ions studied by X-ray diffraction, X-ray absorption, and vibrational spectroscopy.

Crystal structures of the solvated copper(I) and silver(I) perchlorate salts crystallizing from N,N-dimethylthioformamide solution have been determined by single-crystal X-ray diffraction at 295 K. Tetrakis(N,N-dimethylthioformamide)copper(I) perchlorate, [Cu(SCHN(CH(3))(2))(4)]ClO(4), crystallizes in the monoclinic space group P2/n (No. 13) with a = 8.428(2), b = 9.605(2), and c = 15.096(3) A, beta = 104.35(2) degrees, and Z = 2. The copper(I) ion in a site of C(2) symmetry coordinates four N,N-dimethylthioformamide ligands in a slightly distorted tetrahedral coordination with Cu-S bond distances of 2.3249(8) and 2.3494(8) A. The triclinic (P1, No. 2) tris(N,N-dimethylthioformamide)silver(I) perchlorate, Ag(SCHN(CH(3))(2))(3)ClO(4), with a = 7.4149(5), b = 7.7953(5), and c = 17.1482(1) A, alpha = 98.341(5), beta = 93.910(5), and gamma = 107.084(5) degrees, and Z = 2, contains centrosymmetric Ag(2)(SCHN(CH(3))(2))(6)(2+) dimers in which two almost planar AgS(3) units are held together by an asymmetric double sulfur bridge with one short and one long Ag-S bond, 2.529(1) and 2.930(1) A, respectively. The Ag-S bond distances to the two terminal N,N-dimethylthioformamide ligands are 2.469(1) and 2.543(1) A. The solvated copper(I) and silver(I) ions in solution were found by means of large-angle X-ray scattering (LAXS) to coordinate four N,N-dimethylthioformamide molecules with the mean Cu-S and Ag-S bond distances 2.36(1) and 2.58(1) A, respectively, probably with distorted tetrahedral coordination geometry, while an EXAFS study gave the Cu-S bond distance 2.34(1) A. EXAFS studies showed a linear S-Au-S entity with an Au-S bond distance of 2.290(5) A in the structure of the solid bis(N,N-dimethylthioformamide)gold(I) tetrafluoroborate, Au(SCHN(CH(3))(2))(2)BF(4). The structure in solution is similar with a mean Au-S bond distance of 2.283(4) A. Raman and infrared vibrational spectra of the solvated copper(I), silver(I), and gold(I) ions in the solid state and N,N-dimethylthioformamide solution have been recorded and assigned.

Absorptiometry, Photon↗

PubMed2005

Silver(I)-carbene complexes/ionic liquids: novel N-heterocyclic carbene delivery agents for organocatalytic transformations.

[reaction: see text] N-Heterocyclic carbene (NHC) complexes with silver were investigated as sources of unsaturated NHC carbene catalysts via thermal decomposition. The NHC complex (1-ethyl-3-methylimidazol-2-ylidene)silver(I) chloride is an ionic liquid, and was found to catalyze the ring-opening polymerization of lactide at elevated temperatures to give narrowly dispersed polylactide of predictable molecular weight. Silver-carbene complexes can also be used for the catalysis of small molecule transesterification reactions. Thermolysis of the silver complexes in the presence of CS(2) yielded the zwitterionic CS(2) adducts of the carbene, implicating the intermediacy of the free carbene in these reactions.

Catalysis↗

PubMed2005

Electronic structure of Ag2Cu2O4. Evidence of oxidized silver and copper and internal charge delocalization.

The electronic structure of the recently isolated silver copper oxide Ag(2)Cu(2)O(4) is analyzed along with its precursor Ag(2)Cu(2)O(3) and similar binary oxides, Ag(2)O, AgO, CuO, and NaCuO(2), using X-ray photoemission (XPS) and X-ray absorption (XAS) measurements. The results for Ag(2)Cu(2)O(4) reveal an electronic distribution in which silver and copper share a delocalized valence scheme with both metals in formal oxidation states larger than the usual Ag(I) and Cu(II). Only one type of crystallographic silver or copper is found, but disorder-strain parameters are considerable and the possibilities of thermal disorder, atomic motion, oxygen contribution, mixed valence, and internal charge delocalization are considered. Classical coordination descriptions for oxidized silver are revisited in terms of this new internal charge delocalization framework found for the electronic structure.

Copper↗

PubMed2005

DNA-network-templated self-assembly of silver nanoparticles and their application in surface-enhanced Raman scattering.

A large-scale lambda-DNA network on a mica surface was successfully fabricated with a simple method. Silver nanoparticles capped with the cationic surfactant cetyltrimethylammonium bromide (CTAB) were self-assembled onto a two-dimensional DNA network template by electrostatic interaction and formed nanoporous silver films, which can be used as active surface-enhanced raman scattering (SERS) substrates. Two probe molecules, Rhodamine 6G (R6G) and 4-aminothiophenol (4-ATP), were studied on these substrates with very low concentrations, and great enhancement factors for R6G (0.21 x 10(10)-4.09 x 10(11)) and 4-ATP (approximately 1.70 x 10(5)) were observed. It was found that the enhancement ability was affected by the DNA concentration and the electrostatic absorption time of the CTAB-stabilized silver nanoparticles on the DNA strands. These SERS substrates formed by the self-assembly of silver nanoparticles on DNA network also show good stability and reproducibility in our experiments.

Aniline Compounds↗

PubMed2005

Laser photolysis of silver colloid prepared by citric acid reduction method.

By irradiating a silver colloid, prepared via the citric reduction method, using the second harmonic of a Nd:YAG laser, lambda = 532 nm, with laser fluence more than about 0.2 J/cm(2), we prepared a colloid consisting of small spherical silver nanoparticles with d(p) = 8 nm. The process of particle formation can be divided into three steps. First, large particles that existed in the initial colloid evaporate fully, producing a large amount of silver atoms. Next, primary particles with d(p) = 2-4 nm are formed in mini plumes. Finally, these primary particles grow up to 8 nm, as silver atoms diffuse to them through water.

Citric Acid↗