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Silver-109 NMR spectroscopy of inorganic solids.

In this study the (109)Ag NMR spectra of the following solid inorganic silver-containing compounds were investigated: AgNO(3), AgNO(2), Ag(2)SO(4), Ag(2)SO(3), AgCO(3), Ag(3)PO(4), AgCl, AgBr, AgI, AgSO(3)CH(3), silver p-toluenesulfonate, NaAg(CN)(2), KAg(CN)(2), K(3)Ag(CN)(4), Me(4)NAgCl(2), silver diethylthiocarbamate, silver lactate, silver acetate, silver citrate, and bis[(N,N(1)-di-tert-butylformamidinato)silver(I)]. The magic angle spinning (MAS) spectra of all compounds were obtained. In some cases, when protons were available, the (1)H to (109)Ag cross-polarization (CP) technique was used to enhance the signal and shorten the experimental relaxation delay. It was possible to obtain slow MAS (or CP/MAS) or nonspinning spectra for 10 samples, allowing the determination of the principal components of the (109)Ag chemical shift (CS) tensors. The isotropic chemical shifts and the CS tensors are discussed in light of the available crystal structures. The need for an accepted standard for referencing (109)Ag chemical shifts and the use of AgSO(3)CH(3) as a CP setup sample are also discussed.

Isotopes↗

Selective induction of anti-fibrillarin autoantibodies by silver nitrate in mice.

Female SJL (H-2s) mice developed serum IgG anti-nucleolar antibodies (ANoA) after 5 weeks treatment with 0.05% or 0.01% silver nitrate (AgNO3) in drinking water. Five more weeks of treatment increased the ANoA titre to 3410 +/- 853 and 640 +/- 175 (reciprocal mean +/- s.e.m.), respectively. Controls receiving ordinary tap water and mice given 0.002% AgNO3 showed no antinucleolar antibodies. The high-titre ANoA targeted a 34-kD nucleolar protein identified as fibrillarin, the major autoantigen in murine mercury-induced autoimmunity and in a fraction of patients with systemic scleroderma. Serum autoantibodies to chromatin or histones, kidney, spleen, stomach, thyroid, or skin antigens (except the nucleolus) were not found in any of the mice. There was no consistent significant increase of serum IgG1, IgG2a, IgG2b, or IgG3 concentrations after AgNO3 treatment compared with controls. Mice treated with 0.05% AgNO3 for 10 weeks showed a slight decrease in serum IgG1, IgG2b and IgG3 concentrations. These mice also showed a small but statistically significant increase in renal, mesangial IgM deposits, which was not accompanied by any increase in C3c deposits, whereas mice given lower doses of silver nitrate showed no significant increase in mesangial immunoglobulin immune deposits. Systemic vessel wall immune deposits were not found in any of the mice. In mice given 0.05% silver nitrate, the kidney showed the highest concentration of silver (12.2 +/- 0.09 micrograms Ag/g wet weight; mean +/- s.e.m.), followed by the spleen (8.7 +/- 1.3), and the liver (3.9 +/- 0.4). Treatment with 0.01% silver nitrate caused a different distribution of silver, with the highest concentration in the spleen (2.1 +/- 0.16 micrograms Ag/g), followed by the kidney (0.63 +/- 0.037), and the liver (< 0.29 micrograms Ag/g; mean). Silver seems to be a more specific inducer of antinucleolar/anti-fibrillarin autoantibodies than mercury and gold, lacks the general immune stimulating potential of mercury, and has only a weak tendency to induce renal immune deposits. These observations suggest that the autoimmune sequelae induced in mice by metals is dependent, not only upon the genetic haplotype of the murine strain, but also on the metal under investigation.

Animals↗

Silver products for medical indications: risk-benefit assessment.

BACKGROUND: Legitimate medicinal use of silver-containing products has dramatically diminished over the last several decades. Recently, however, some manufacturers have begun to enthusiastically promote oral colloidal silver proteins as mineral supplements and for prevention and treatment of many diseases. Indiscriminate use of silver products can lead to toxicity such as argyria. OBJECTIVE: To assist health care professionals in a risk versus benefit assessment of over-the-counter silver-containing products, we herein examine the following issues: historical uses, chemistry, pharmacology, clinical toxicology, case reports of adverse events in the literature, and the recent promotion of over-the-counter silver products. Other sources of silver exposure (including environmental and dietary) and EPA exposure standards are discussed. A list of currently available silver products is provided for easy reference and screening. CONCLUSIONS: We emphasize the lack of established effectiveness and potential toxicity of these products.

Animals↗

[Effect of silver preparations on the microflora regenerated from a condensate of atmospheric water vapor in a hermetically-sealed chamber].

The effect of different silver compounds (silver sulphate, silver nitrate, electrolytic ionic silver) on microorganisms in water reclaimed from the atmospheric condensate in an enclosed environment was investigated. The following microorganisms were examined: Alcaligenes faecalis, Citrobacter freundii. Aeromonas hydrophila, Staphylococcus epidermidis, etc. The ionic silver concentrations in solution varied from 0.1 to 10 mg/l. The efficiency of the silver compounds was found to depend on the microbial strain, ionic silver concentration in solution, and time of exposure. The microflora of the reclaimed water proved to be highly resistant to the preservatives which was strongly associated with the bacterial physical and chemical composition of the products preserved.

Aeromonas↗

The potential clinical and economic benefits of silver alloy urinary catheters in preventing urinary tract infection.

BACKGROUND: Catheter-associated urinary tract infection (UTI) is associated with increased morbidity, mortality, and costs. A recent meta-analysis concluded that silver alloy catheters reduce the incidence of UTI by 3-fold; however, clinicians must decide whether the efficacy of such catheters is worth the extra per unit cost of $5.30. OBJECTIVE: To assess the clinical and economic impact of using silver alloy urinary catheters in hospitalized patients. METHODS: The decision model, performed from the health care payer's perspective, evaluated a simulated cohort of 1000 hospitalized patients on general medical, surgical, urologic, and intensive care services requiring short-term urethral catheterization (2-10 days). We compared 2 catheterization strategies: silver alloy catheters and standard (noncoated) urinary catheters. Outcomes included the incidence of symptomatic UTI and bacteremia and direct medical costs. RESULTS: In the base-case analysis, use of silver-coated catheters led to a 47% relative decrease in the incidence of symptomatic UTI from 30 to 16 cases per 1000 patients (number needed to treat = 74) and a 44% relative decrease in the incidence of bacteremia from 4.5 to 2.5 cases per 1000 patients (number needed to treat = 500) compared with standard catheters. Use of silver alloy catheters resulted in estimated cost savings of $4.09 per patient compared with standard catheter use ($20.87 vs $16.78). In a multivariate sensitivity analysis using Monte Carlo simulation, silver-coated catheters provided clinical benefits over standard catheters in all cases and cost savings in 84% of cases. CONCLUSIONS: Using silver alloy catheters in hospitalized patients requiring short-term urinary catheterization reduces the incidence of symptomatic UTI and bacteremia, and is likely to produce cost savings compared with standard catheters.

Alloys↗

Deposition profile of antibacterial anodic silver in root canal systems of teeth.

Electrically activated silver was shown to have an antibacterial effect in vitro and in vivo. In this study the effect of placing a silver anode in the root canal systems of teeth was examined to establish a base for treatment of infected teeth. Pure silver wires were placed in the main canals of extracted human teeth (n = 26) whose roots were partly submerged in a lactated Ringer's solution. Seventeen microamperes of anodic direct current were applied to one group of silver wires (n = 15) for 4 days. Then the wires were removed and the roots of both group teeth were cut into six sections and demineralized Silver concentrations of the root sections and their bathing solutions were measured with an atomic absorption spectrophotometer. In the anode group, the electrically activated silver concentrations (range, 1-30 micrograms/microL) exceeded the antibacterial levels (minimum inhibitory concentration, 0.1 micrograms/microL Ag) in all sections, particularly in the middle and lower sites of the root. The amount of anodic silver that leaked out of the root was found as to be 0.4 +/- 0.2 micrograms/microL in the fluid medium. This was 10 to 100-fold higher than that found in the nonactivated controls.

Anti-Infective Agents↗

Electrogenerated chemiluminescence of luminol in neutral and alkaline aqueous solutions on a silver nanoparticle self-assembled gold electrode.

The electrochemiluminescence (ECL) behaviour of luminol on a silver nanoparticle self-assembled gold electrode in neutral and alkaline solutions was investigated using conventional cyclic voltammetry (CV). The silver nanoparticle self-assembled gold electrode exhibited excellent ECL properties for the luminol ECL system. In neutral solutions, four ECL peaks (ECL-1-ECL-4) were observed at 0.73, 1.15, -0.46 and -1.35 V (vs. SCE), respectively. The intensities of these peaks were enhanced significantly compared with those on a bulk gold electrode and a gold nanoparticle self-assembled gold electrode. It was found that ECL-1 and ECL-2 on a silver nanoparticle-modified electrode were about 1000 and 1770 times stronger than those on a bare Au electrode and were about 17 and 15 times stronger than those on a gold nanoparticle-modified electrode, respectively. In alkaline solutions, four ECL peaks were also observed that were much stronger than those in neutral solutions, and ECL-1 and ECL-2 were enhanced by about three orders and one order of magnitude compared with those on a bare Au electrode and on a gold nanoparticle self-assembled electrode, respectively. Moreover, the silver nanoparticle-modified electrode exhibited good stability and reproducibility for luminol ECL. These peaks were found to depend on a number of factors, including silver nanoparticles on the surface of the modified electrode, potential scan direction, scan rate, scan range, the presence of O2 or N2, pH values, the concentrations of NaBr and luminol, and buffer solutions. The emitter of the ECL was confirmed as 3-aminophthalate by analysing the CL spectra. The surface state of the silver nanoparticle self-assembled electrode was characterized by scanning electron microscopy (SEM) and the interface property of the electrode was studied by electrochemical impedance spectroscopy (EIS). A mechanism for the formation of these ECL peaks is proposed. The results demonstrate that luminol has excellent ECL properties, such as strong ECL intensity and good reproducibility on a silver nanoparticle-modified gold electrode, in both neutral and alkaline solutions, which is of great potential in analytical applications.

Air↗

Improved detection of lymphocyte membrane proteins in purified form and as a crude mixture using native and denaturing polyacrylamide gel electrophoresis by optimisation of coomassie brilliant blue and silver staining.

Optimised silver staining protocols were devised for the detection of membrane proteins in purified form and as a crude mixture. These were adduced in both sodium dodecyl sulphate (SDS) and native polyacrylamide gel electrophoresis and consisted of ethanol-acetic acid-formaldehyde fixation, Coomassie Brilliant Blue prestaining, Rapidfix pretreatment, formaldehyde enhancement and finally ammoniacal silver staining. With these modifications, numerous staining problems of membrane proteins were overcome. These included reduction in background staining, enhanced detection sensitivity in native gels, elimination of negative staining and the avoidance of metallic silver deposition on the gel surface. In overcoming these problems, some factors determining the colour and stainability of membrane proteins in their native state were determined. Both the anionic Coomassie Brilliant Blue dye and SDS detergent improved the sensitivity of silver staining in native gels, and ammoniacal silver was more sensitive than neutral silver, suggesting silver staining to be a charge dependent process.

Ammonia↗

Blue silver: a very sensitive colloidal Coomassie G-250 staining for proteome analysis.

A modified Neuhoff's colloidal Coomassie Blue G-250 stain is reported, dubbed "blue silver" on account of its considerably higher sensitivity, approaching the one of conventional silver staining. The main modifications, as compared to Neuhoff's protocol, were: a 20% increment in dye concentration (from 0.1% up to 0.12%) and a much higher level of phosphoric acid in the recipe (from 2% up to 10%). The "blue silver" exhibits a much faster dye uptake (80% during the first hour of coloration, vs. none with a commercial preparation from Sigma). Even at equilibrium (24 h staining), the "blue silver" exhibits a much higher sensitivity than all other recipes, approaching (but lower than) the one of the classical silver stain. Measurements of stain sensitivity after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of bovine serum albumin (BSA) gave a detection limit (signal-to-noise ratio > 3) of 1 ng in a single zone. The somewhat lower sensitivity of "blue silver" as compared to classical silvering protocols in the presence of aldehydes is amply compensated for by its full compatibility with mass spectrometry of eluted polypeptide chains, after a two-dimensional map analysis, thus confirming that no dye is covalently bound (or permanently modifies) to any residue in the proteinaceous material. It is believed that the higher level of phosphoric acid in the recipe, thus its lower final pH, helps in protonating the last dissociated residues of Asp and Glu in the polypeptide coils, thus greatly favoring ionic anchoring of dye molecules to the protein moiety. Such a binding, though, must be followed by considerable hydrophobic association with the aromatic and hydrophobic residues along the polypeptide backbone.

Animals↗

Polyamide/silver antimicrobials: effect of filler types on the silver ion release.

The efficiency of various silver-based antimicrobial fillers (elementary silver and silver substituted materials) in polyamide (PA) toward their silver ion (Ag+) release characteristics in an aqueous medium was investigated and discussed. Anode stripping voltammetry (ASV) was used for the quantitative estimation of Ag+ release from these composites. The biocidal (Ag+) release from the composites was found to be dependent on the time of soaking in water and the nature of the filler. The long-term Ag+ release capability of the elementary silver-based PA/Ag composite is promising compared with the commercial counterparts. The silver ion release potential of polyamide composites where the silver filling was performed by using supercritical carbon dioxide (scCO2) is also discussed. The composites release Ag+ at a concentration level capable of rendering antimicrobial efficacy and proved to be active against the microbes. A good agreement exists between the Ag+ release experiments and antimicrobial test results. The observed results on the influence of the nature of the filler and crystallinity on the biocidal release and the varying long-term release properties could be helpful in the design of industrially relevant biomaterials.

Animals↗

Characterization of peptides by liquid chromatography/electrospray ionization mass spectrometry using silver nitrate as a post-column complexant.

Two model peptides, des-Arg1-bradykinin (DAB) and bradykinin (B), were cationized by Ag+ after their separation by reversed-phase liquid chromatography (RPLC) prior to mass spectrometry (MS). Silver nitrate solution was used as a post-column reagent. The RPLC and MS experimental conditions were optimized using flow injection in order to obtain sufficiently abundant silver adducts to permit MS/MS experiments. The use of water-methanol with 0.1% formic acid as mobile phase allowed a good chromatographic separation of the two peptides with a polymeric stationary phase and sufficiently abundant silver-containing adducts, [M + Ag + H]2+ and [M + 2Ag]2+. The gas-phase dissociation of [DAB + Ag + H]2+ and [DAB + 2Ag]2+ led to interpretable mass spectra during the on-line cationization experiment. Most of the ions obtained by dissociating [DAB + Ag + H]2+ and [DAB + 2Ag]2+ species are silver-containing ions but the ions produced depend on the parent. The ions coming from the dissociation of the doubly charged silver adducts [DAB + Ag + H]2+ or [DAB + 2Ag]2+ are of interest compared with those coming from the singly charged silver species or doubly charged protonated species. The fragmentation of the doubly charged silver adducts provides ions over the entire mass range. Although the presence of several prolines in des-Arg1-bradykinin prevents the formation of some expected ions, the observation of triplets [an-H + Ag]+, [bn-H + Ag]+ and [bn + OH + Ag]+ produced by the dissociation of on-line Ag(+)-cationized peptides could contribute to greater success of automatic sequencing of peptides.

Bradykinin↗

Abundance of protein-bound sulfhydryl and disulfide groups at chromosomal nucleolus organizing regions: a cytochemical study on the selective silver staining of NORs.

Silver stainability of the chromosomal nucleolus organizing regions that contain the structural genes for ribosomal RNA can be abolished by proteolytic and oxidative treatments. Histone extraction has no effect. This indicates that reducing groups of non-histone chromosomal proteins are responsible for silver staining. Treatment with fluorescent sulfhydryl and disulfide specific reagents followed by silver staining demonstrates coincidence of silver dots and brightly fluorescent spots at the short arms of human acrocentric chromosomes where ribosomal RNA-genes are located. After treatment with cupric sulfite reagent in the presence of urea fluorescence and silver staining was no longer possible. Silver staining has been reported to be associated with ribosomal RNA-gene activity. Acrocentric chromosomes that are negative in silver staining also lack the brightly fluorescent spots. Therefore, we conclude that an abundance of protein-bound sulfhydryl and disulfide groups occur at nucleolar organizing regions with active genes. Differentially fluorescing spots could not be observed after staining with fluorescamine. So, either the sulfhydryl reagents used in this study are much more sensitive than fluorescamine to study protein distributions in cytological preparations, or our observations point to a local accumulation of some specific protein(s) rich in sulfhydryls. The presence of many sulfhydryl and disulfide groups at the nucleolus organizing regions seems suggestive of a great flexibility of protein(s) by transition of sulfhydryl groups to disulfide bridges and vice versa at these highly active regions of the genome.

Cells, Cultured↗

Enhancement of the periodic acid--Schiff (PAS) and periodic acid--thiocarbohydrazide--silver proteinate (PA-TCH-SP) reaction in LR white sections.

LR White is a well-suited resin for the demonstration of carbohydrates with the PAS or PA-TCH-SP reaction in semithin and ultrathin sections. The intensity of these reactions can be greatly enhanced by using 3 steps in tissue preparation, either singly or in combination: 1) The PAS reaction in semithin sections turns out stronger after partial (70% ethanol) than complete (100% ethanol) dehydration of the tissue before its transfer to 100% LR White. 2) Silver enhancement of the PA-TCH-SP reaction product can simply be effected by physical development of ultrathin sections (PA-TCH-SP-SE reaction). Least precipitates are formed in this procedure, when sections are mounted on uncoated gold grids, processed for cytochemistry, and thinly coated with carbon in the end. 3) The use of hot silver proteinate (50 degrees C) plus strong silver enhancement (15-20 min silver lactate developer) reveals minute concentrations of TCH-labelled aldehyde groups in the tissue that do not react with silver proteinate at room temperature.--Silver enhancement and the use of hot silver proteinate do not depend on LR White, but may also be applied to ultrathin sections of tissue embedded in other resins.

Acrylic Resins↗

Silver uptake by Agaricus bisporus from an artificially enriched substrate.

The champignon mushroom Agaricus bisporus was cultivated on compost (wheat and rye straw, hens' manure, gypsum, urea and peat) artificially fortified with silver nitrate added at four different concentrations (0.01, 0.1, 1.0 and 10.3 mg/kg) and 0 mg/kg (control) on a dry weight basis. The method of measurement was flame atomic absorption spectrophotometry after dry ashing of the samples at 420 degrees C and dissolving the residue in 1 M nitric acid. The highest concentration of silver, reaching between 120 +/- 30-150 +/- 36 mg/kg on a dry weight basis, was observed in fruit bodies grown on the most contaminated substrate containing 10.3 mg added Ag/kg dry weight. The silver concentration in caps/stalks/whole fruit bodies of A. bisporus was positively correlated (r = 0.72; P < 0.001) with an increasing level of fortification of the substrate. The bioconcentration factor (BCF) of silver in caps/stalks/whole fruit bodies of A. bisporus was inversely correlated (-0.44 < r < -0.36; 0.001 < p < 0.01) with the silver concentration of the contaminated substrate. The highest silver BCF value of 120-230 has been observed in caps and stalks of mushrooms grown on a substrate enriched with 0.01 mg Ag/kg dry weight. Silver ion added to the substrate in concentrations up to 10.3 mg/kg on a dry weight basis exhibited no observable toxic effect against the mycelial growth and fruiting of A. bisporus.

Agaricus↗

Linkage of silver to antibodies through 2-imino thiolane.

Earlier studies described the linkage of silver to antibodies using SH groups generated by the reduction of the SS groups using ascorbic acid (1) analogous to the Thakur and DeFulvio technique for linking technetium to antibodies. This work describes the linkage of silver to IgG after introducing SH groups by coupling the IgG to 2-imino thiolane. The protein was dissolved in sodium acetate buffer pH 4.5 containing 1 mM EDTA by dialysis/gel chromatography in a concentration of 20 mg/mL. 2-Imino thiolane dissolved in Tris-HCl acetate buffer, pH 8.2, 0.2M was added to give a final dilution of 0.2 mM 2-imino thiolane. The excess of 2-imino thiolane was removed by dialysis or G-25 Sephadex gel chromatography and then the protein was reacted with silver nitrate 0.1 mM. The unreacted SH groups were blocked by adding iodoacetamide to a concentration of 5 mM. The nonprotein reagents again were removed by dialysis or gel chromatography. The thiol groups were titrated using 1.5 mM 2 2-Py-SS-Py prior to and after addition of silver. It was observed that depending on the concentration of silver, 50-80% of the SH groups were coupled to silver. Higher concentrations of silver led to insoluble precipitates and should be avoided.

Animals↗

Metal-enhanced fluorescence using anisotropic silver nanostructures: critical progress to date.

In this critical and timely review, the effects of anisotropic silver nanostructures on the emission intensity and photostability of a key fluorophore that is frequently used in many biological assays is examined. The silver nanostructures consist of triangular, rod-like, and fractal-like nanoparticles of silver deposited on conventional glass substrates. The close proximity to silver nanostructures results in greater intensity and photostability of the fluorophore than for fluorophores solely deposited on glass substrates. These new anisotropic silver nanostructure-coated surfaces show much more favorable effects than silver island films or silver colloid-coated substrates. Subsequently, the use of metal-enhanced fluorescence (MEF) for biosensing applications is discussed.

Anisotropy↗

Ionoregulatory development and the effect of chronic silver exposure on growth, survival, and sublethal indicators of toxicity in early life stages of rainbow trout (Oncorhynchus mykiss).

Rainbow trout embryos and larvae were continuously exposed, in a flow-through system, to 0, 0.1 microg/l (measured=0.098 +/- 0.002 microg/l) or 1.0 microg/l (measured=0.853+/-0.022 microg/l) total silver (as AgNO3) in moderately hard water (120 mg CaCO3/l, 0.70 mM Cl, 1.3 mg/l dissolved organic matter and 13.7 +/- 0.1 degrees C) from fertilization to I week post-hatch. The objectives of the study were to investigate the effects of chronic silver exposure on mortality, time to hatch and growth, and on sublethal physiological indicators of toxicity. Exposure to 1.0 microg/l total silver resulted in a small, but statistically significant, increase in mortality (16%) relative to controls (12%) but interestingly, resulted in an increased rate of growth (as indicated by larval weight, length and extractable protein) and ionoregulatory development over the duration of this study. Whole body unidirectional Na uptake (J(in)Na+) increased with silver exposure concentration (both 0.1 microg/l and 1.0 microg/l total silver) just prior to and following hatch, with up to a three-fold elevation in J(in)Na+ in the 1.0 microg/l treatment relative to controls. Qualitatively similar changes in whole body Na+,K-ATPase activity (per mg protein or per whole embryo or larvae) also occurred over this period. By 1 week post-hatch, there were no differences in J(in)Na among treatments and Na+,K+-ATPase activity levels in silver exposed groups were significantly reduced relative to controls. Within 2 days following hatch, there was an elevation in whole larval ammonia levels, while cortisol levels were elevated at 1 week post-hatch in the 1.0 microg/l treatment relative to controls. Ionoregulatory disturbance and elevations in both cortisol and ammonia have also been observed during acute silver exposure in adult rainbow trout, indicating that chronic and acute mechanisms of toxicity may be similar.

Ammonia↗

Silver stain for proteins on a cellulose acetate membrane.

A rapid and sensitive silver staining method to detect proteins on a cellulose acetate membrane has been established. This method is achieved by modification of the silver-based color staining for detection of proteins in polyacrylamide gels [D. W. Sammons, L. D. Adams, and E. E. Nishizawa, Electrophoresis 2, 135-141 (1981)] and applied to our new type of two-dimensional electrophoresis for analysis of proteins on a cellulose acetate sheet [T. Toda, T. Fujita, and M. Ohashi, Anal. Biochem. 119, 167-176 (1982)]. Maximal sensitivity of silver stain for proteins on a cellulose acetate membrane can be obtained by an optimal balance between deposition of silver on the protein and on the background. Certain kinds of proteins are colored red, orange, or grayish-blue. The silver stain is 20-80 times more sensitive than Coomassie blue and some spots are visualized reproducibly by silver only. Densitometric evaluation of standard proteins stained with silver and Coomassie blue is also demonstrated. The method takes only 50 min to perform and is sensitive, simple, and reproducible.

Animals↗