Optical and electrical properties of the silver cluster compound (Ag6Ge4P12)Ge6.
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Journal Article↗
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A Protest Against the Indiscriminate Use of the Organic Compounds of Silver in Ophthalmic Practice.
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Journal Article↗
Spectroscopic studies on 2,3,4,5-tetraphenylpyrylium salts with and without silver (I)-bridged structures.
Two novel phenylated pyrylium compounds, silver (I)-bridged 2,3,4,5-tetraphenylpyrylium perchlorate (P1) and its silver (I)-free pyrylium ligand (P2) were prepared from 1,2,3,4-tetraphenylcyclopentadiene to examine their spectroscopic behaviors. The UV/vis absorption and fluorescent emission spectra of P1 and P2, measured in three solvents (acetonitrile, dichloromethane and toluene), reveal that the photophysical behaviors are closely related to silver (I) fragment, and strongly dependent on solvent polarity. In polar acetonitrile, P1 displays longer absorption wavelength and much lower fluorescent emission intensity than P2, although they exhibit much similarity in shape. In contrast, in nonpolar toluene, while P2 shows an apparent absorption band at 338 nm, P1 displays a tail-like line without absorption band observed. All the spectra obtained indicate a better coplanarity and a stronger intra-molecular charge transfer in P1 due to the effect of silver (I) fragment. Additionally, the 1H NMR spectra of P1 and P2, which were recorded under the same conditions, indicate that the silver (I) fragment reinforces pyrylium ring's capacity to localize the formal positive charge within the heterocyclic ring.
Heterocyclic Compounds, 3-Ring↗
Avance: silver hydropolymer dressing for critically colonized wounds.
Avance is a hydropolymer dressing that has a silver compound bonded into it. The silver acts as a bacterial shield to prevent bacterial invasion, and as a bacterial barrier to impede cross-infection. This article aims to give an overview of the use of silver in eradicating surface bacteria, and provides case study evidence of the use of Avance on the leg ulcers of two patients. Both patients had complex medical histories and underlying aetiologies that delayed the wound-healing process.
Bandages↗
[The disinfection of the oral mucosa].
For evaluation of antiseptics intended for use on mucous membranes various effects, as bactericidal and fungicidal but also bacteriostatic and fungistatic effects as well as other mechanisms, have to be considered. The application of antiseptics on the oral mucous membrane is indicated to prevent wound infections, bacteremia following surgical intervention, infection caused by injuries as for example prosthetic ulcers as well as it is indicated for prophylaxis and therapy of infections like colds and for prevention of exogenic dissemination of bacteria. The substances used essentially are PVP-iodine-solutions, cation-active compounds, organic mercury- and silver-compounds and hydrogen peroxide-solutions. It has to be taken into account, however, that the toxicological properties of these substances vary. To this day there exists no generally accepted test model for the evaluation of these mucous membrane antiseptics. Therefore a test-solution on the basis of chlorhexidine digluconate was examined with the help of a rinse- and a swab-method, respectively. The total bacterial counts and the number of alpha-haemolytic streptococci was determined. The rinse-method resulted in reduction factors of log 1.0 after 5 to 120 min and the swab-method--applied at the buccal mucous membranes--in reduction factors of about log 1.5 after 5 min and log 1.0 to 1.2 after 120 min. At the gingival margin of the front teeth reduction factors rose from log 1.55 after 5 min to log 1.85 after 120 min. Possibly this rise was due to an after-effect of the tested antiseptic in this region. For examination of antiseptics a combination of both test methods is recommended.
Bacteria↗
New potent inhibitors of aquaporins: silver and gold compounds inhibit aquaporins of plant and human origin.
Silver and gold compounds were tested as potential inhibitors of aquaporins of plant- and human origin. Silver as AgNO(3) or silver sulfadiazine inhibited with high potency (EC(50) 1-10 microM) the water permeability of the peribacteroid membrane from soybean (containing Nodulin 26), the water permeability of plasma membrane from roots (containing plasma membrane integral proteins), and the water permeability of human red cells (containing aquaporin 1). Gold as HAuCl(4) was less effective but still inhibited peribacteroid membrane water permeability (EC(50)=10 microM). Silver and gold are more potent inhibitors of aquaporins than the presently widely used mercury containing compounds.
Aquaporin 1↗
Effect of silver on burn wound infection control and healing: review of the literature.
Silver compounds have been exploited for their medicinal properties for centuries. At present, silver is reemerging as a viable treatment option for infections encountered in burns, open wounds, and chronic ulcers. The gold standard in topical burn treatment is silver sulfadiazine (Ag-SD), a useful antibacterial agent for burn wound treatment. Recent findings, however, indicate that the compound delays the wound-healing process and that silver may have serious cytotoxic activity on various host cells. The present review aims at examining all available evidence about effects, often contradictory, of silver on wound infection control and on wound healing trying to determine the practical therapeutic balance between antimicrobial activity and cellular toxicity. The ultimate goal remains the choice of a product with a superior profile of infection control over host cell cytotoxicity.
Anti-Infective Agents↗
Silver nylon cloth: in vitro and in vivo evaluation of antimicrobial activity.
The topical agents used in burn care today, although beneficial, do have limitations, the most important of which is the failure to prevent or treat burn wound infections in patients with extensive injuries. Therefore, we evaluated the antimicrobial activity of two silver nylon fabrics (SN and HRS) on the growth of S. aureus, P. aeruginosa, and C. albicans. The theoretical advantages of these nylon fabrics over presently available silver compounds is their ability to continuously release silver ions into the burn wound as long as the material is in contact with the wound. Additionally, the release of silver from these fabrics can be augmented electrolytically. The results of these experiments indicated that both materials were microbicidal in vitro for all three test organisms. Furthermore, the antimicrobial activity could be significantly augmented by passing a weak DC current through the material, which increased the rate of release of silver ions from the fabrics. In vivo, HRS was as effective as silver sulfadiazine in preventing colonization of the burn wound. The use of silver nylon fabrics thus appears to be a promising way of delivering large quantities of silver ions into the burn wound without the potential side effects of a carrier molecule or cream.
Bandages↗
Silver bromide nanoparticle/polymer composites: dual action tunable antimicrobial materials.
We present a simple method of fabricating highly potent dual action antibacterial composites consisting of a cationic polymer matrix and embedded silver bromide nanoparticles. A simple and novel technique of on-site precipitation of AgBr was used to synthesize the polymer/nanoparticle composites. The synthesized composites have potent antibacterial activity toward both gram-positive and gram-negative bacteria. The materials form good coatings on surfaces and kill both airborne and waterborne bacteria. Surfaces coated with these composites resist biofilm formation. These composites are different from other silver-containing antibacterial materials both in the ease of synthesis and in the use of a silver salt nanoparticle instead of elemental silver or complex silver compounds. We also demonstrate the ability to tune the release of biocidal Ag(+) ions from these composites by controlling the size of the embedded AgBr nanoparticles. These composites are potentially useful as antimicrobial coatings in a wide variety of biomedical and general use applications.
Anti-Bacterial Agents↗
Light and electron microscopic localization of silver in biological tissue.
A method is described that visualizes trace amounts of silver in frozen, paraffin and epon sections from biological tissue. After exposure to light, which ensures reduction of silver ions that are not bound to sulphide, histological sections from animals treated with silver compounds are exposed to a photographic developer containing silver ions. Tissue silver acts as a catalyst for the hydroquinone reduction of silver ions to metallic silver which then accumulates at the site of the trace deposit. Light and electron micrographs showing silver in different organs from albino rats treated with silver lactate are presented. Localization of silver in motor neurons of the spinal gray matter and pons indicates a transport of silver over the blood-brain barrier. Silver precipitates in fetal liver suggest that silver ions can penetrate the placental barrier.
Animals↗
Interaction of the human leukocyte proteinases elastase and cathepsin G with gold, silver and copper compounds.
Gold thiomalate and the corresponding silver and copper derivatives were investigated as inhibitors of the human leukocyte proteinases elastase and cathepsin G. The kinetic inhibition mechanism for gold- and silver thiomalate is of the hyperbolic non-competitive type with both enzymes and the inhibitory efficiency of the metals increases in the order Cu less than Ag less than Au. On the contrary, D-penicillamine derivatives of the three metals do not influence at all the activity of the two proteinases. Although gold thiomalate is the most efficient of the investigated metal compounds (Ki = 33 microM and 25 microM for elastase and cathepsin G, respectively), the hyperbolic nature of the inhibition imposes a serious limit to its practical usefulness since the maximum inhibitory action on both enzymes is about 40%. We suggest that, in order to act as inhibitor, a copper, silver or gold compound must be able to easily transfer the metal to the enzyme.
Cathepsin G↗
Four-Coordinate Gold(I), Silver(I), and Copper(I) Complexes with a Large-Span Chiral Ditertiary Phosphine Ligand.
The ligand L = Ph(2)PCH(2)CHEtOPPh(2) (R,S) with two chemically different donor sites and a center of chirality in the middle of the loop connecting the phosphorus atoms has been chosen for the preparation of a series of gold(I), silver(I), and copper(I) complexes. The ligand-to-metal ratio was allowed to vary between 2:1, 1:1, and 1:2. The 1:1 complexes [LAuX](2) with X = Cl, Br, I, and SCN have been found to be components of solution equilibria (in di- or trichloromethane) of various cyclic dinuclear isomers involving also several complexes generated in ligand redistribution processes. However, single crystals (X = Cl, Br) obtained from these solutions are composed solely of centrosymmetrical dimers where the two metal atoms are part of 12-membered rings and are bridged transannularly by two halogen atoms. By symmetry, the metal bridging by the two ligands L follows a head-to-tail pattern and involves a pair of enantiomers of L. The silver compound [LAgClO(4)](2) has an analogous structure with the silver atoms attaining coordination number 4 by perchlorate bridging. The copper complex [LCuCl](2) is a tricyclic binuclear compound where each copper atom is chelated by an individual ligand L and doubly halogen bridged with the second metal atom. The 2:1 complex [L(2)Au]Cl is assigned a bis-chelated structure with the tetracoordinated metal atom as a spiro center of two six-membered rings. The solution (31)P NMR spectra show the presence of various stereoisomers which are readily identified via the strong couplings mediated by the metal center. Only small J(P, P') values would be expected for P-P' coupling along the ligand PCCOP' loops. The spectrum of the dinuclear 1:2 complex L(AuCl)(2) features only two singlet (31)P resonances.
Journal Article↗
Silver deposition and tissue staining associated with wound dressings containing silver.
Argyria is the general term used to denote a clinical condition in which excessive administration and deposition of silver causes a permanent irreversible gray-blue discoloration of the skin or mucous membranes. The amount of discoloration usually depends on the route of silver delivery (ie, oral or topical administration) along with the body's ability to absorb and excrete the administered silver compound. Argyria is accepted as a rare dermatosis but once silver particles are deposited, they remain immobile and may accumulate during the aging process. Topical application of silver salts (eg, silver nitrate solution) may lead to transient skin staining. To investigate their potential to cause skin staining, two silver-containing dressings (Hydrofiber and nanocrystalline) were applied to human skin samples taken from electively amputated lower limbs. The potential for skin discoloration was assayed using atomic absorption spectroscopy. When the dressings were hydrated with water, a significantly higher amount of silver was released from the nanocrystalline dressing compared to the Hydrofiber dressing (P <0.005), which resulted in approximately 30 times more silver deposition. In contrast, when saline was used as the hydration medium, the release rates were low for both dressings and not significantly different (silver deposition was minimal). Controlling the amount of silver released from silver-containing dressings should help reduce excessive deposition of silver into wound tissue and minimize skin staining.
Administration, Cutaneous↗
[Amperometric titration of erythrocyte membrane sulfhydryl groups].
The best conditions are selected for amperometric titration of erythrocyte membranes SH-groups by means of silver ions. On the basis of the experimental data, two types of SH-groups according to their capacity of binding Ag+ are found in the membranes. Dynamics of transition of SH-groups of types I into SH-groups of type II is studied. The chemical model explaining the presence of two bends in the course of the membranes amperometric titration curve is created. Calculations were made for the products of R-S-Ag solubility for SH-groups of type I and SH-groups of types I and II as well as for entropy and heat of formation of silver compounds with the membranes sulphydryl groups.
Cell Membrane↗
Gold(I) and silver(I) mixed-metal trinuclear complexes: dimeric products from the reaction of gold(I) carbeniates or benzylimidazolates with silver(I) 3,5-diphenylpyrazolate.
Trinuclear mixed-metal gold-silver compounds are obtained by the reaction of gold(I) carbeniate [Au(mu-C(OEt)=NC6H4-p-CH3)]3, TR(carb), or gold(I) imidazolate [Au-mu-C,N-1-benzyl-2-imidazolate]3, TR(bzim), with silver(I) pyrazolate [Ag(mu-3,5-Ph2pz)]3. The crystalline products are mixed-ligand, mixed-metal dimeric products [Au(carb)Ag2(mu-3,5-Ph2pz)2], [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2, [Au(bzim)2Ag2(mu-3,5-Ph2pz)], and [Au2(bzim)2Ag(mu-3,5-Ph2pz)]. They have been characterized by elemental analysis and 1H NMR and mass spectrometry. The X-ray structure of [Au(carb)Ag2(mu-3,5-Ph2pz)2] shows it to be a dimer with two Ag...Au contacts between the trinuclear units of 3.083(2) and 3.310(2) A and with average intramolecular Ag...Ag and Au...Ag distances of approximately 3.3 and 3.2 A, respectively. The structure of [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 is a dimer with one intermolecular Au...Au attraction of 3.3354(10) A and a short Ag...Au distance of approximately 3.42 A and intramolecular Ag...Au and Au...Au contacts of approximately 3.2 and approximately 3.3 A, respectively. Packing diagrams of both complexes show that the dimeric units are independent, similar to their parent molecules. The dimers of trinuclear [Au(carb)Ag2(mu-3,5-Ph2pz)2] and [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 crystallize in the triclinic space group P (Z = 2), a = 9.688(3) A, b = 15.542(4) A, c = 23.689(6) A, alpha = 82.560(5) degrees , beta = 87.887(6) degrees , gamma = 78.060(5) degrees , and the orthorhombic space group Pca2(1) (Z = 4), a = 29.644(4) A, b = 7.4582(10) A, c = 30.473(4) A, respectively. The structure of [Au(bzim)Ag2(mu-3,5-Ph2pz)2] is a dimer with two metallophilic Ag...Au interactions of 3.14 A. The complex crystallizes in the monoclinic space group C2/c (Z = 4), a = 26.368(5) A, b = 15.672(3) A, c = 17.010(3) A, beta = 102.206(3) degrees .
Crystallography, X-Ray↗
Superconductivity in copper, silver, and gold compounds.
High-temperature superconductivity exists in layered, square-planar cuprates, but is almost absent in most other Cu(II) compounds and in most Ag(II) and Au(II) compounds. Valence state II is quite unusual in silver and gold and often disproportionates to valence states I and III ("negative-U compounds"). The two-electron difference in oxidation state is suggestive of electron pairing, a prerequisite for superconductivity. In the present paper the connection between disproportionation and geometrical structure on one hand and superconductivity on the other is discussed by using the accepted theory for mixed valence complexes. It is concluded that absence of superconductivity in gold and silver compounds can be connected to the instability of oxidation state II and the large difference in equilibrium geometry between oxidation states I and III.
Journal Article↗
Microcomputer-controlled determination of dissociation constants of sulfanilamides and stability constants of the related silver complexes.
As a contribution to the structure-activity relationship of silver sulfanilamide complexes, the pKa-values of thirteen sulfanilamides and the log K-values of their related silver compounds were determined using a microcomputer-controlled titrator which determines the silver ion concentration and hydrogen ion concentration in a combined measurement. Predictions on antibacterial effectiveness and the risk of sensitization reactions of some of the investigated silver sulfanilamides are made on the basis of the conditional stability constants computed from the pKa- and log K-values at pH = 7.4.
Chemical Phenomena↗
[Adaptation of the treatment with a mixture of sulfur, silver and chromium compounds to the recovery of radiobromine in biology].
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Bromine↗