Preparation and testing of silver-protein compounds.
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Coloring Agents↗
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Characterization of organometallic coordinative cluster compounds of silver by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was successfully applied to characterize the organosilver coordinative cluster compounds, silver phenylacetylide and three silver thiolates, namely, silver tertiary butylthiolate, silver 2,6-dimethylbenzenethiolate, and silver 2, 6-dichlorobenzenethiolate. Samples and dithranol matrix were finely dispersed in 1:1 tetrahydrofuran (THF)/chloroform (CHCl(3)) mixed solvent. In most cases the monomer units remained intact during ionization, and the oligomeric molecular ions were produced through silver cationization, with a general molecular ion formula [nM + Ag](+). This was further verified by the relative abundances of the isotopic peaks within the molecular ion clusters, which were in close agreement with those theoretically calculated for nM cationized with one silver ion. In the case of silver 2, 6-dichlorobenzenethiolate, in addition to the dominant [nM + Ag](+) peaks, weak peaks corresponding to the successive losses of hydrogen chloride molecules were observed. Copyright 2000 John Wiley & Sons, Ltd.
Journal Article↗
[Is there such a thing as encephalopathy related to organic compounds of silver?].
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Aged↗
Partitioning and effects of silver in amended freshwater sediments.
Sediments that represented a wide range of characteristics were amended with silver compounds to observe partitioning and bioavailability. In laboratory studies, silver partitioning to particulates, sediment pore water, and overlying water was measured and bioavailability of silver was determined using Hyalella azteca in 10-day sediment toxicity tests. Three silver compounds were used as sources of silver for this study: silver nitrate, silver chloride, and silver thiosulfate complex. Sediment amendment procedures were adjusted as necessary depending on the characteristics of the individual compounds. Several sediment characteristics such as organic carbon, pH, redox, and acid volatile sulfides regulated silver partitioning and bioavailability. Bioavailability of silver was correlated with the overlying water concentration of silver. Ten-day LC50 values ranged from 1.62 to 379.7 mg Ag/kg for H. azteca exposed to sediments amended with AgNO3. In laboratory experiments, silver chloride and silver thiosulfate were orders of magnitude less toxic and bioavailable than silver nitrate, with 10-day LC50 values greater than the highest concentrations of AgCl and silver thiosulfate complex amended to sediments (2560 and 1125 mg Ag/kg, respectively.
Animals↗
Evaluation of a standardized method for determining soluble silver in workplace air samples.
Several occupational exposure limits and guidelines exist for silver, but the values for each depend on the chemical form of the silver compound in question. In the past, it generally was not possible, without prior knowledge of the work process, to distinguish soluble silver from insoluble silver compounds collected in workplace air samples. Therefore, analytical results were historically reported as total silver. In this study, work was conducted to evaluate a method to differentiate between the quantities of water-soluble silver compounds and total silver collected on filters. The investigation entailed an evaluation of an International Organization for Standardization method to determine soluble silver in airborne particulate matter. The study design incorporated laboratory experiments to evaluate analytical figures of merit, such as selection of appropriate filter media and extraction solution, analytical recovery, and sample stability during storage. Polytetrafluoroethylene (PTFE) filters (2 microm, 37 mm) in opaque cassettes were either spiked with known amounts of silver nitrate or contained a known mass of solid silver nitrate. Results showed that over 90% of the silver was recovered from PTFE filters. Also, field studies were conducted in which workplace air samples were collected in two silver refineries. Some of these samples were analyzed only for soluble silver while others were sequentially extracted and analyzed, first, for soluble silver, then for total silver. The mass fractions of soluble silver, as compared to total silver, were approximately 2% or less. This investigation served to validate an international standard procedure for the determination of soluble silver in workplace air samples.
Air Pollutants, Occupational↗
Silver in health care: antimicrobial effects and safety in use.
Silver has a long and intriguing history as an antibiotic in human health care. It has been developed for use in water purification, wound care, bone prostheses, reconstructive orthopaedic surgery, cardiac devices, catheters and surgical appliances. Advancing biotechnology has enabled incorporation of ionizable silver into fabrics for clinical use to reduce the risk of nosocomial infections and for personal hygiene. The antimicrobial action of silver or silver compounds is proportional to the bioactive silver ion (Ag(+)) released and its availability to interact with bacterial or fungal cell membranes. Silver metal and inorganic silver compounds ionize in the presence of water, body fluids or tissue exudates. The silver ion is biologically active and readily interacts with proteins, amino acid residues, free anions and receptors on mammalian and eukaryotic cell membranes. Bacterial (and probably fungal) sensitivity to silver is genetically determined and relates to the levels of intracellular silver uptake and its ability to interact and irreversibly denature key enzyme systems. Silver exhibits low toxicity in the human body, and minimal risk is expected due to clinical exposure by inhalation, ingestion, dermal application or through the urological or haematogenous route. Chronic ingestion or inhalation of silver preparations (especially colloidal silver) can lead to deposition of silver metal/silver sulphide particles in the skin (argyria), eye (argyrosis) and other organs. These are not life-threatening conditions but cosmetically undesirable. Silver is absorbed into the human body and enters the systemic circulation as a protein complex to be eliminated by the liver and kidneys. Silver metabolism is modulated by induction and binding to metallothioneins. This complex mitigates the cellular toxicity of silver and contributes to tissue repair. Silver allergy is a known contra-indication for using silver in medical devices or antibiotic textiles.
Administration, Cutaneous↗
Synthesis, a case of isostructural packing, and antimicrobial activity of silver(I)quinoxaline nitrate, silver(I)(2,5-dimethylpyrazine) nitrate and two related silver aminopyridine compounds.
The synthesis and low temperature crystal structures of [Ag(quinoxaline)]n(NO3)n, 1, [Ag(2,5-dimethylpyrazine)(NO3)]n, 2 and [Ag4(3-aminopyridine)4(NO3)4]n 3 are presented. The quinoxaline compound forms a 1D coordination polymer with the characteristic linear 2-coordination figure of silver(I), the N-Ag-N angle being 164.2(1) degrees, and only weak silver-nitrate interactions. In addition there is an interaction giving pairs of parallel chains as the main structural theme. The 2,5-dimethylpyrazine compound has approximately trigonal-planar coordination, also binding one nitrate at the relatively short Ag-O distances 2.444(3) angstroms and 2.484(3) angstroms, respectively, for the two crystallographically different silver atoms. This also results in a 1D coordination polymer that, despite the large differences in the Ag(I) coordination environment, is isostructural with 1. [Ag4(3-aminopyridine)4(NO3)4]n 3 forms a 2D coordination polymer by bridging nitrate ions. The antimicrobial activity of 1-3, and also of [Ag3(2-aminopyridine)4](NO3)3, 4 was screened for 13 different pathogens and substantial activity was shown for 1 against Escherichia coli and Pseudomonas aeruginosa (MIC 4 microg cm(-3)) and somewhat lower activity was registered against Sarcina lutea and Salmonella typhi for 1, Bordetella bronchiseptica for 2, Salmonella typhi and Pseudomonas aeruginosa for 3, and Escherichia coli and Shigella sonnie for 3 (MIC 8 microg cm(-3)). Only low activity was shown against the yeast Candida albicans for 1, 2 and 4 whereas no activity against this pathogen was registered for 3.
Aminopyridines↗
Systemic argyria.
A 74 year old man presented with signs and symptoms of mild cardiac failure. His face and chest were severely discoloured, which was thought to be due to cyanosis. He deteriorated and died of bronchopneumonia. At post mortem examination multiple organs, including the skin, showed silver pigment deposition; he also had a gastric malignant neuroendocrine tumour. He gave no history of contact with silver compounds. Systemic argyria caused by chronic ingestion of silver compounds is a rare condition which, apart from its cosmetic effects, is thought to be relatively harmless; it is not thought to be carcinogenic. This condition can pose diagnostic problems for both clinicians and pathologists.
Adenoma↗
A historical review of the use of silver in the treatment of burns. II. Renewed interest for silver.
In 1965, Moyer revived interest in silver nitrate solution. He concluded on the basis on in vitro and in vivo studies that a 0.5% solution represented the lowest concentration at which antibacterial action (against Staphylococcus aureus, haemolytic streptococci and generally against Pseudomonas aeruginosa and E. coli) was obtained. Mafenide acetate was introduced a short time after the reintroduction of silver nitrate, followed a few years later by silver sulphadiazine. Thus, in a short period of time three medicaments appeared on the market which represented a radical change in the topical treatment of burns. The action of silver sulphadiazine has been intensively studied. Since silver sulphadiazine does not offer sufficient protection to prevent or retard the growth of gram-negative bacteria in patients with burns covering more than 50% of body surface, Monafo introduced the combined preparation silver sulphadiazine and cerium nitrate. Although various attempts have been made to develop more effective silver compounds, so far silver sulphadiazine still remains the most widely used substance of this type.
Anti-Infective Agents, Local↗
Silver(I) compounds consisting of [2.2]paracyclophane: reversible guest-driven solid-state transformation and incorporation behavior.
Reaction of [2.2]paracyclophane with silver(I) heptafluorobutyrate (AgC3F7CO2) has isolated three novel networks: [Ag4(pcp)(C3F7CO2)4] x pyrene (1), [Ag4(pcp)(C3F7CO2)4] x phen (phen = phenanthrene) (2), and [Ag4(pcp)(C3F7CO2)4] x fluorene (3), and an intercalation compound [Ag4(pcp)(C3F7CO2)4] x 2benzene (4). All the four complexes exhibit two-dimensional (2D) sheet structures in which AgC3F7CO2 form an infinite chain and pcp acts as linkage. 1, 2, and 3 show 2D flat sheets with cavities in which guest molecules are situated, whereas 4 exhibits 2D zigzag layers between which guest benzene molecules are intercalated. Pcp shows mu-di-eta1-eta2 coordination mode in 1, mu-tetra-eta1 coordination mode in 2 and 3, and mu-tetra-eta2 coordination mode in 4. The reversible guest exchanges were observed between complex 1, 2, or 3 and intercalation compound 4. It is unprecedented for metal-organic inclusion complexes that the guest exchange occurs where the guest is the solute molecule. Furthermore, 4 can release the guest, and the original framework was completely recovered after reincorporation of benzene. It should be noted that 4 can incorporate pyrene, phen, and fluorene to give 1, 2, and 3, respectively, after desorption.
Journal Article↗
Preparation and NMR Spectra of Difluoromethylated Silver(I) and Silver(III) Compounds. Structure of [PNP][Ag(CF(2)H)(4)].
The thermally unstable [Ag(CF(2)H)(2)](-) moiety is obtained in solution by reaction of silver(I) salts with Cd(CF(2)H)(2) in DMF/diglyme at -80 degrees C. Oxidation with I(2) leads to the argentate(III) [Ag(CF(2)H)(4)](-), which has been isolated as its PNP salt. According to DSC/TG analysis, the exothermic decomposition of this air-stable salt proceeds in two steps at 121 and 150 degrees C with formal elimination of one and three CFH units, respectively. Difluoromethylation of [Ag(CN)(2)](-) in the presence of acetyl chloride leads to the argentate(I) [Ag(CF(2)H)(CN)](-), which is oxidized by bromine at low temperatures to the thermally labile [trans-Ag(CF(2)H)(2)(CN)(2)](-) anion. Stable argentates(III) containing both difluoromethyl and trifluoromethyl groups are obtained by reaction of [Ag(CF(3))(n)()(CN)(4)(-)(n)()](-) (n = 1, 2-cis, 2-trans, and 3) with Cd(CF(2)H)(2)-the cis and trans configurations of the reactants being retained in their products for n = 2. The compounds are identified and characterized by multinuclear NMR spectroscopy. Crystals of [PNP][Ag(CF(2)H)(4)] belong to the tetragonal space group P4(3) with a = 9.475(1) Å, c = 42.159(6) Å, and Z = 4. The coordination of the silver atom is approximately square-planar with an average Ag-C bond length of 2.083(14) Å. The ligands are so oriented that each C-H bond is geared between the C-F bonds of a neighboring CF(2)H group-the overall symmetry being approximately C(4)(h)().
Journal Article↗
[The preparation of collagen burn pellicle of compound sulfadiazine silver and assessment of its efficacy in an animal experiment on deep partial thickness burn wound].
OBJECTIVE: To prepare the collagen burn pellicle of compound sulfadiazine sliver and observe its therapeutic effect on deep partial thickness burn wound. METHODS: The initator method was adopted for preparing the collagen burn pellicle of compound sulfadiazine sliver. A model of deep partial thickness burn wound was established in 84 SD rats for the observation of the effect of collagen burn pellicle of compound sulfadiazine sliver on burn wound healing. RESULTS: The collagen burn pellicle of compound sulfadiazine sliver enhanced the coming off of necrotic tissues and the healing of burn wound. The hydroxyproline content of burn wound was higher in the experiment group than that in the comparison groups, (P < 0.05). The percentage of G0/G1-phase in full skin cells of burn wound at 5, 7, 10 and 14 days after burn was lower than that in the comparison groups (P < 0.05). The percentage of S-phase at 5, 7 and 14 days was higher in the experiment group than that in the comparison groups (P < 0.05). The water content in full skin cells of burn wound at 24, 36 and 48 hours after burn was significantly lower in the experiment group than that the comparison groups (P < 0.05). CONCLUSION: The collagen burn pellicle of compound sulfadiazine sliver can enhance wound healing in the management of deep partial thickness burn wound.
Animals↗
Ring-opening polymerisation of coordination compounds: a silver(I) network with both ring and polymer components.
The terpyridyl ligand 2,6-C5H3N{C(=O)N(Me)-4-C5H4N}2, 1, combined with silver(I) salts to give the complexes [Ag2(1)2][BF4]2, 2, and [{Ag3(1)2}n][CF3SO3]3n, 3; the network structure of complex contains both macrocyclic units [Ag2(mu-1)2]2+ and ring-opened polymeric units [{Ag(mu-1)}n]n+.
Crystallography, X-Ray↗
[Cutaneous absorption and urinary elmination of a silver sulfadiazine compound used in the treatment of burns].
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Adolescent↗
In vitro quantitative study of newly made antibacterial braided nylon sutures.
This study was done to examine quantitatively the antibacterial property of a newly made, silver compound coated braided nylon suture and to confirm the previously reported qualitative antibacterial data. Three representative bacterial species were used and they were Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The suture specimens were embedded in a custom built plastic device filled with a fixed concentration of bacteria for predetermined periods of incubation. A direct current ranging from 0.4 to 40.0 microamperes was applied to the suture specimens. The bacterial suspension was periodically removed for a standard plate count in order to determine quantitatively the antibacterial capability of the suture specimens. The amounts of silver ions released to the medium under various direct current levels were also determined by a pH/ion meter. The antibacterial property of the suture was evident in the anode site of the material, and at a fixed current, the degree of bacteriostatic effect depended upon the type of bacterial species. For example, a difference of almost 10(3) in the number of Pseudomonas aeruginosa was observed within a period of six hours. The responses of Staphylococcus aureus and Escherichia coli to the silver compound coated nylon thread, however, were not as drastic as Pseudomonas aeruginosa. These quantitative data were consistent with the previously reported qualitative observation of the width of clear zone in bacterial culture plates. The silver ion concentration in the medium increased with increasing either the current level or time, or both. At the end of six hours, the ion concentrations were 7.3 micrograms per milliliter at 0.4 microampere, 44.3 micrograms per milliliter at 4.0 microamperes and 305.7 micrograms per milliliter at 40.0 microampere.
Anti-Bacterial Agents↗
Syntheses, structures, and properties of intercalation compounds of silver(I) complex with [2.2]paracyclophane.
Reaction of [2.2]paracyclophane (pcp) with silver(I) trifluoroacetate (AgCF(3)CO(2)) and silver(I) pentafluoroproprionate (AgC(2)F(5)CO(2)) has led to isolation of three novel intercalation polymers: [Ag(4)(pcp)(CF(3)CO(2))(4)](C(6)H(6)) (1), [Ag(4)(pcp)(CF(3)CO(2))(4)](C(6)H(3)Me(3)) (2), and [Ag(4)(pcp)(C(2)F(5)CO(2))(4)](pcp) (3). Structure studies using single crystal X-ray diffraction have shown that all compounds contain two-dimensional layered frameworks based on cation-pi interactions, in which pcp exhibits an unprecedented micro-tetra-eta(2) coordination mode. Guest molecules which weakly interact with the host pcp via C-H.pi interactions are intercalated between layers. The guest-eliminated complexes (1a and 2a) and guest-reincorporated ones (1b or 1c and 2b or 2c), accompanied by small structural changes, were confirmed by (1)H NMR, thermogravimetric analysis, mass spectra, and X-ray powder diffraction patterns. The structural changes from 1 --> 1a --> 1c (=1) can take place reversibly in the process of exposure of 1a to benzene vapor. The original framework of complex 2 is also completely recovered by immersing 2a in mesitylene as well as exposing it to mesitylene vapor.
Journal Article↗
Preparation and NMR Spectra of the (Trifluoromethyl)argentates(III) [Ag(CF(3))(n)X(4-n)](-), with X = CN (n = 1-3), CH(3), C&tbd1;CC(6)H(11), Cl, Br (n = 2, 3), and I (n = 3), and of Related Silver(III) Compounds. Structures of [PPh(4)][trans-Ag(CF(3))(2)(CN)(2)] and [PPh(4)][Ag(CF(3))(3)(CH(3))].
Trifluoromethylation of [Ag(CN)(2)](-) with (CF(3))(2)Cd.diglyme yields [Ag(CF(3))(CN)](-). The anion is readily oxidized by bromine to the argentates(III), [Ag(CF(3))(n)(CN)(4-n)](-), n = 1-4. The stability of these species decreases with an increasing number of CN groups. Halogenation of these complexes with acetyl chloride or with bromine affords the moderately stable (n = 3) or unstable (n = 2) haloargentates of the type [Ag(CF(3))(n)X(4-n)](-), X = Cl or Br. Their dehalogenation with AgNO(3) in a donor solvent D gives the adducts [Ag(CF(3))(3)D] and [Ag(CF(3))(2)D(2)](+), respectively. Decomposition of most argentates(III) proceeds by reductive elimination of CF(3)X (X = Cl, Br, or CN), but ligand exchange with participation of the CF(3) groups is also observed. The latter is used to prepare Ag(CF(3))(3) derivatives from the readily accessible [trans-Ag(CF(3))(2)(CN)(2)](-) anion. The syntheses of methyl(trifluoromethyl)argentates(III) and of (cyclohexylethynyl)(trifluoromethyl)argentates(III) are accomplished by reaction of the cyanoargentates (n = 2, 3) with CH(3)MgCl or LiC&tbd1;CC(6)H(11), respectively. Often multinuclear ((109)Ag, (19)F, (13)C, (1)H) NMR data of transient and stable Ag(III) species establish unambiguously not only their constitution but also the square-planar coordination of the metal. Couplings to the spin-(1)/(2) silver nuclei are interpreted on the basis of 5s(Ag) orbital participation in competition with 4d orbital contributions to Ag-CF(3) bonding. Crystals of [PPh(4)][Ag(CF(3))(2)(CN)(2)] belong to the monoclinic space group C2/c, with a = 18.174(2) Å, b = 7.8881(8) Å, c = 18.881(2) Å, beta = 93.036(8) degrees, and Z = 4, whereas [PPh(4)][Ag(CF(3))(3)(CH(3))] crystallizes in the orthorhombic space group Pca2(1), with a = 24.941(3) Å, b = 7.2629(6) Å, c = 14.9985(14) Å, and Z = 4. The coordination environments of these two argentates are approximately square planar. The Ag-CF(3) bonds in the dicyano complex (2.105(4) Å) are distinctly longer than the Ag-CN linkages (2.013(3) Å). In the [Ag(CF(3))(3)(CH(3))](-) anion, the Ag-CH(3) distance (2.097(5) Å) is slightly shorter than the average Ag-CF(3) bond lengths (2.119(10) Å).
Journal Article↗
Chemical nature of the first products (nuclei) of the argyrophil staining.
In agreement with LIESEGANG (1911) but in disagreement with VOIGT (1957), PARTRIDGE (1957) and WINKELMANN and SCHMIT (1959), the first product in the majority of the traditional argyrophil methods is submicroscopic grains (nuclei) of metallic silver forming in the impregnating bath at the effect of reducing groups of the tissue (argyrophil I reaction). It is the localization pattern of the metallic silver nuclei that determines the distribution of the silver in the final microscopic image, and not the colloid character of the tissue, as stated by VOIGT (1952) and others. In special cases, colloid grains of certain silver compounds (non-metallic silver nuclei) forming with the contribution of the tissue (argyrophil II reaction) in the impregnating bath constitute the basis of the staining. There are argyrophil methods which consist of pretreatments and a physical development but have no impregnation phase. In one part of them, non-metallic silver nuclei forming with the contribution of the tissue (argyrophil II reaction) in the physical developer, in the other part, certain points of the tissue structure with favourable chemical composition, capable of catalyzing the interaction of silver ions and the reducing component of the physical developer (argyrophil III reaction) serve for the initiation of the staining.
Animals↗