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At least 667 records · Page 37Linked to original sources
PubMed1980

Activation of antibacterial silver coatings on surgical implants by direct current: preliminary studies in rabbits.

Staphylococcus aureus contamination on intramedullary silver pins in the femurs of rabbits was decreased 69% by the application of 9 muA for 1 hour of positive direct current/cm2 (9muAH+DC/cm2). Injection of a solution of silver chloride or silver nitrate into the bone marrow before insertion of the contaminated pins and subsequent application of 12 muAH+DC/cm2 to the stainless steel pins reduced the colony counts 25% and 64%, respectively, and indicated a need for the Ag+ and Cl- ionic state on the pins' surfaces. Stainless steel pins electroplated with silver and charged with 12 muAH+DC/cm2 decreased the bacterial counts by 85%. A 91% inhibition with stainless steel pins electroplated with silver and chlorided indicated that bacteriostasis was possible due to the Ag+/AgCl/Cl- surface effect. Total bacterial inhibition was achieved by 12 muAH+DC/cm2 on stainless steel pins coated with 100 monomolecular layers of silver stearate. The electrical activation of this coating eliminated up to approximately 3,000 S aureau contaminating the intramedullary pins.

Animals↗
PubMed1995

Preliminary evaluation of silver-coated peritoneal catheters in rats.

Silver is known to have powerful antibacterial properties against a variety of micro-organisms and has a low toxicity and a favorable biocompatibility profile. This study was designed to evaluate the effectiveness of silver-coated catheters in preventing early exit-site infection and to assess tunnel morphology. Seven male Sprague-Dawley rats underwent simultaneous implantation of two double-cuffed, silver-coated silicone rubber and standard silicone rubber catheters. Weekly observations and photographs documented exit-site characteristics. The animals were sacrificed and catheters removed and processed for histopathology of the external tunnel at 5 weeks. Exit sites of silver-coated catheters tended to have less inflammation and infection and healed better than those of uncoated catheters; however, these data did not achieve significance using the Wilcoxon signed-rank test. Sections of the external tunnel of well-healing exit sites showed an epithelialized tract with granulation tissue near the cuff and significant invasion of the external cuff by collagen with a mild neutrophilic inflammatory response. In contrast, the histology of the external tunnel of infected exists revealed exudate overlying inflammatory granulation tissue and a variable degree of fibrosis of the cuff. When the exit sites appeared similar, no significant histopathological differences in sinus tract and cuff morphology were noted with either silver or standard catheters. In conclusion, these findings suggest that silver coating of catheters may decrease the incidence of early exit-site infections and allow better ingrowth of the catheter.

Animals↗
PubMed1955

Silver deposition in the central nervous system and the hematoencephalic barrier studied with the electron microscope.

For the purpose of studying the hematoencephalic barrier as it is concerned with silver circulating in the blood stream, silver nitrate was vitally administered to rats in their drinking water over periods of 6 to 8 months. The cerebrum, cerebellum, medulla, area postrema, and choroid plexus were prepared for light and electron microscopy. Silver deposition was found in the perivascular spaces in the choroid plexus, area postrema, in the medulla surrounding the area postrema, and in minute quantities in the cerebrum, cerebellum, and most of the medulla. Two levels of the hematoencephalic barrier were apparently demonstrated in our investigations. The endothelial linings of the vessels in the cerebrum, cerebellum, and medulla constitute the first threshold of the hematoencephalic barrier (specifically here, blood-brain barrier). The cell membranes adjacent to the perivascular spaces form the second threshold, as follows:-the neuroglial cell membranes in the cerebrum, cerebellum, and medulla (blood-brain barrier); the membranes of the neuroglial cells in the area postrema (blood-brain barrier); and the membranes of the epithelial cells of the choroid plexus (blood-cerebrospinal fluid barrier). This study deals with silver deposition and does not infer that the penetration of ionic silver, if present in the blood stream, would necessarily be limited to the regions described. Bleb-like structures were observed to cover the epithelial cell surfaces in the choroid plexus. They may be cellular projections increasing the cell surface area or they may be secretory droplets.

Animals↗
PubMed2005

[The structure and properties of self-assembly complex LB films of silver nanoparticles].

The structure and properties of Ag self-assembly films have attracted much attention in the past decade, which are to a large extent influenced by the structure and properties of the nanoparticles. In the present work, the single-layer and multi-layer complex films of silver nanoparticles and their absorbates were fabricated by using self-assembly technique. The interaction of silver nanoparticle and its absorbate was studied using absorption spectroscopy and surface enhanced Raman scattering spectroscopy.The Raman enhanced properties of silver nanoparticles, and the structure and properties of the complex films were also investigated. The experimental results indicate that the interaction of octodecyl amic (OA) and silver nanoparticle takes place via the NH2 substitute and the active site on Ag, and there might exist photocatalysis under the laser excitation. In addition, the product from otcodecyl amic and stearic acid(SA) has a weak interaction with silver nanoparticle, which mainly takes place as spatial encumbrance in the self-assembly complex film.

Benzene Derivatives↗
PubMed2004

A simple hydrothermal route to large-scale synthesis of uniform silver nanowires.

This paper describes the preparation of uniform silver nanowires by reducing freshly prepared silver chloride with glucose at 180 degrees C for 18 hours in the absence of any surfactants or polymers. Scanning electron microscopy studies indicated that the silver nanowires are about 100 nm in diameter and up to 500 microm in length. High-resolution transmission electron microscopy analyses showed that the silver nanowires grow perpendicularly to the Ag(200) plane. The silver nanowires are believed to grow through a solid-solution-solid process. Some influential factors on the growth of silver nanowires are also discussed.

Journal Article↗
PubMed2004

Form and function in the unique inner ear of a teleost: the silver perch (Bairdiella chrysoura).

Members of the teleost family Sciaenidae show significant variation in inner ear and swim bladder morphology as well as in the relationship between the swim bladder and the inner ear. In the silver perch (Bairdiella chrysoura), a Stellifer-group sciaenid, both the saccular and utricular otoliths are enlarged relative to those in other teleosts. Additionally, its swim bladder is two-chambered, and the anterior chamber surrounds the otic capsule and terminates lateral to the saccules. Structure and function of the auditory system of the silver perch were explored by using gross dissections, scanning electron microscopy, CT scan reconstruction, and auditory brainstem response approach. Several morphological specializations of the auditory system of the silver perch were found, including expansion of the utricular and lagenar otoliths, close proximity between the saccules and the utricles, deeply grooved sulci on the saccular otoliths, two-planar saccular sensory epithelia, and a unique orientation pattern of sensory hair cell ciliary bundles on the saccular sensory epithelium. It was determined that the silver perch can detect up to 4 kHz, with lowest auditory thresholds between 600 Hz and 1 kHz. Audition in the silver perch is comparable to that in the goldfish (Carassius auratus), a hearing "specialist." The morphological specializations of the inner ear and swim bladder of the silver perch may be linked to its enhanced hearing capabilities. The findings of this study support the proposal that sciaenids are excellent model species for investigating structure-function relations in the teleost auditory system.

Air Sacs↗
PubMed2006

Molecular cloning and characterization of alpha-class glutathione S-transferase gene from the liver of silver carp, bighead carp, and other major Chinese freshwater fishes.

Two full-length cDNAs encoding glutathione S-transferase (GST) were cloned and sequenced from the hepatopancreas of planktivorous silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis). The silver carp and bighead carp GST cDNA were 920 and 978 bp in length, respectively, and both contained an open reading frame that encoding 223 amino acids. Partial GST cDNA sequences were also obtained from the liver of grass carp (Ctenopharyngodon idellus), crucian carp (Carassius auratu), mud carp (Cirrhinus molitorella), and tilapia (Oreochromis nilotica). All these GSTs could be classified as alpha-class GSTs on the basis of their amino acid sequence identity with other species. The three-dimensional structure of the silver carp GST was predicted using a computer program, and was found to fit the classical two-domain GST structure. Using the genome walker method, a 875-bp 5'-flanking region of the silver carp GST gene was obtained, and several lipopolysaccharide (LPS) response elements were identified in the promoter region of the phytoplanktivorous fish GST gene, indicating that the GST gene expression of this fish might be regulated by LPS, released from the toxic blue-green algae producing microcystins. To compare the constitutive expression level of the liver GST gene among the six freshwater fishes with completely different tolerance to microcystins, beta-actin was used as control and the ratio GST/beta-actin mRNA (%) was determined as 130.7 +/- 6.6 (grass carp), 103.1 +/- 8.9 (bighead carp), 92.6 +/- 15.0 (crucian carp), 72.3 +/- 7.8 (mud carp), 58.8 +/- 11.5 (silver carp), and 33.6 +/- 13.7 (tilapia). The constitutive expression level of the liver GST gene clearly shows that all the six freshwater fishes had a negative relationship with their tolerance to microcystins: high-resistant fishes (phytoplanktivorous silver carp and tilapia) had the lowest tolerance to microcystins and the high-sensitive fish (herbivorous grass carp) had the highest tolerance to microcystins. Taken together with the reciprocal relationship of constitutive and inducible liver GST expression level in some of the tested fish species to microcystin exposure, a molecular mechanism for different microcystin detoxification abilities of the warm freshwater fishes was discussed.

5' Flanking Region↗
PubMed2005

Silver nanoparticle assemblies supported on glassy-carbon electrodes for the electro-analytical detection of hydrogen peroxide.

Electrochemical detection of hydrogen peroxide using an edge-plane pyrolytic-graphite electrode (EPPG), a glassy carbon (GC) electrode, and a silver nanoparticle-modified GC electrode is reported. It is shown, in phosphate buffer (0.05 mol L(-1), pH 7.4), that hydrogen peroxide cannot be detected directly on either the EPPG or GC electrodes. However, reduction can be facilitated by modification of the glassy-carbon surface with nanosized silver assemblies. The optimum conditions for modification of the GC electrode with silver nanoparticles were found to be deposition for 1 min at -0.5 V vs. Ag from 5 mmol L(-1) AgNO3/0.1 mol L(-1) TBAP/MeCN, followed by stripping for 2 min at +0.5 V vs. Ag in the same solution. A wave, due to the reduction of hydrogen peroxide on the silver nanoparticles is observed at -0.68 V vs. SCE. The limit of detection for this modified nanosilver electrode was 2.0 x 10(-6) mol L(-1) for hydrogen peroxide in phosphate buffer (0.05 mol L(-1), pH 7.4) with a sensitivity which is five times higher than that observed at a silver macro-electrode. Also observed is a shoulder on the voltammetric wave corresponding to the reduction of oxygen, which is produced by silver-catalysed chemical decomposition of hydrogen peroxide to water and oxygen then oxygen reduction at the surface of the glassy-carbon electrode.

Journal Article↗
PubMed2004

Formation of silver bromide precipitate of nanoparticles in a single microemulsion utilizing the surfactant counterion.

Silver bromide precipitate of nanoparticles was prepared by addition of silver nitrate aqueous solution to a single microemulsion system consisting of dioctyldimethylammonium bromide, n-decanol, and water in isooctane. The silver ion reacted readily with the surfactant counterion, bromide, to form the precipitate of nanoparticles, which was stabilized in the water pools. The use of the surfactant counterion as a reactant is a new approach to nanoparticle preparation in microemulsions. It is characterized by high reactivity and less dependency on the intermicellar exchange of solubilizate. The effects of the surfactant and the cosurfactant concentrations, the amount of silver nitrate, and the water to surfactant mole ratio, R, were evaluated. Increasing the surfactant concentration at fixed R and amount of silver nitrate enhanced the role of intermicellar nucleation and resulted in the formation of larger particles, while increasing the amount of silver nitrate at fixed values of all the other variables enhanced the direct nucleation and resulted in the formation of smaller particles. Particle aggregation and flocculation took place when the concentration of n-decanol or the value of R was increased. Particle aggregation and flocculation were attributed to the decrease in the interaction between the surfactant protective layer and the nanoparticles in the water pools.

Journal Article↗
PubMed2004

Concentration-dependent surface-enhanced Raman scattering of 2-benzoylpyridine adsorbed on colloidal silver particles.

Surface-enhanced Raman scattering (SERS) of 2-benzoylpyridine (2-BP) adsorbed on silver hydrosols has been investigated. It has been observed that with a small change in the adsorbate concentration, the SER spectra of 2-BP show significant change in their features, indicating different orientational changes of the different part of the flexible molecule on the colloidal silver surface with adsorbate concentration. The time dependence of the SER spectra of the molecule has been explained in terms of aggregation of colloidal silver particles and co-adsorption and replacement kinetics of the adsorbed solute and solvent molecules on the silver surface. The broad long-wavelength band in the absorption spectra of the silver sol due to solute-induced coagulation of colloidal silver particles is found to be red-shifted with the increase in adsorbate concentration. The surface-enhanced Raman excitation profiles indicate that the resonance of the Raman excitation radiation with the new aggregation band contributes more to the SERS intensity than that with the original sol band.

Journal Article↗
PubMed2006

Application of a multi-dentate amphiphilic compound to transfer silver nanoparticles into an organic solvent.

A multi-dentate amphiphilic compound, 3,3'-(dodecylazanediyl)-bis-[N-(2-aminoethyl)propanamide] (12C-2NH2) has been synthesized. The molecular structure was characterized by Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-vis) spectra, nuclear magnetic resonance (NMR) spectra, and fast atom bombardment mass (FAB-MS) spectra. 12C-2NH2 was employed to stabilize silver nanoparticles. Surface properties and stability of silver nanoparticles were controlled by adjusting the 12C-2NH2 to silver (0) molar ratio. 12C-2NH2 was also applied to transfer silver nanoparticles from an aqueous to an organic phase. The transfer efficiency depends on 12C-2NH2 concentration. When 12C-2NH2 to silver (0) molar ratio was 2:1, the highest efficiency of phase transfer to toluene was obtained. These 12C-2NH2 stabilized silver nanoparticles are very stable over a period of four days in toluene.

Journal Article↗
PubMed2004

Evaluation of silver methenamine method for nanoleakage.

OBJECTIVES: The aim of this study was to evaluate nanoleakage patterns following silver methenamine staining of restorations bonded with a total-etch single bottle system, a self-etching primer system and a total-etch single bottle system after collagen depletion. METHODS: The dentin bonding systems used in this study were Prime and bond 2.1 (PB) and Clearfil SE Bond (CSEB). Cavities were made in grounded labial surfaces of 15 extracted bovine lower incisors, randomly divided into 3 Groups. Group 1 (PB), Group 2 (CSEB) and Group 3 (PB/SH) PB after collagen depletion with sodium hypochlorite (SH). The specimens were restored, sectioned and submitted to silver methenamine staining, polished and observed with low-vacuum back-scattered SEM. One way ANOVA and multiple-comparison Tukey's test were used for statistical analysis of the leakage scores. RESULTS: PB presented significantly greater silver deposition and a distinct pattern when compared to CSEB. No silver deposition was detected for PB after collagen depletion. SIGNIFICANCE: The dentine bonding systems tested were unable to prevent nanoleakage when used according to the manufacturers' instructions; however, CSEB presented a lower level of silver deposition. Collagen depletion prior to PB application may prevent nanoleakage occurrence in dentine walls. Silver methenamine staining may be a useful method for detection of nanoleakage in dentine when the collagen fibrils remain exposed within the hybrid layers.

Acetone↗
PubMed2005

Is the silvering process similar to the effects of pressure acclimatization on yellow eels?

To reproduce eels need to migrate over 6000 km and at pressure but before this migration they metamorphose into silver eels (silvering). The question raised in this study is to determine whether and how the silvering process contributes to pressure resistance. As migration represents a long swimming activity mainly performed with slow muscles, the red muscle energetics of pressure exposed silver eels was studied. By comparing these results to what has already been shown in yellow eels, we point out that the effects of the silvering process on pressure resistance are similar to the effects of pressure acclimatization in yellow eels. As previously shown, success of pressure acclimatization depends on membrane fluidity, but we raise the hypothesis that the high-pressure resistance of silver eels is due to more fluid membranes.

Acclimatization↗
PubMed2003

Adsorption of cations onto the surfaces of silver nanoparticles.

The effects of cations on the absorption spectra of silver sols have been investigated by the UV-vis spectrometry and TEM. Experiments showed that injection of certain amounts of transition metal cations into silver sols resulted not only in the aggregation of silver nanoparticles but also in the appearance of a new band centered near 510 nm in the absorption spectra of silver sols. However, the new band was not observed in the presence of alkaline earth metal cations or the Mv2+ cations. The peak position of the new band depends on the nature as well as the concentration of metal cations used. Comparing the peak positions of the new bands, it was found that the new band induced by the injection of Cr3+ was red-shifted with respect to those induced by Cu2+, Zn2+, or the Cd2+ cations. It is reasonable that this band near 510 nm should be attributed to the coeffects of the adsorption of metal cations onto the surfaces of silver nanoparticles and the aggregation of silver nanoparticles.

Journal Article↗
PubMed2003

Phase transfer of silver nanoparticles from aqueous to organic solutions using fatty amine molecules.

We demonstrate the phase transfer of silver nanoparticles synthesized in an aqueous medium into hexane containing the cationic surfactant octadecylamine (ODA). During vigorous shaking of the biphasic mixture, rapid phase transfer of the silver nanoparticles into the organic phase was observed. The phase transfer of the silver nanoparticles arises due to coupling of the silver nanoparticles with the ODA molecules present in organic phase via either coordination bond formation or weak covalent interaction. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilized silver nanoparticles could be separated out from the organic phase in the form of a powder and are readily redispersible in different organic solvents. The nature of binding of the ODA molecules to the silver nanoparticle surface was characterized using UV-vis spectroscopy, thermogravimetry, transmission electron microscopy, nuclear magnetic resonance spectroscopy, X-ray photoemission spectroscopy, and Fourier transform infrared spectroscopy.

Journal Article↗
PubMed1989

Silver staining of Pneumocystis carinii in the rat's lung.

The backscattered electron imaging mode of the scanning electron microscope was used to study the ontogenetic acquisition of argyrophilia in Pneumocystis carinii in rats. Silver staining continually increased from the late trophozoite to the mature cyst stage. The silver uptake began with a fine outline at the surface of the bodies of the late trophozoites; their cellular extensions, however, did not stain. The oblate precyst forms acquired the silver in heterogeneous patches. On spherical cysts the silver staining became more uniform and intense with at least one dense spot. The spherical and collapsed cysts also had short silver staining projections that may represent microvilli. Collapsed forms were paler than spherical ones and appear to be cysts that have undergone partial or complete release of sporozoites. These cell surface observations confirm and amplify previous transmission electron microscopical and histochemical studies indicating that silver staining correlates with the acquisition of the cell pellicle.

Animals↗
PubMed2006

Printed silver ohmic contacts for high-mobility organic thin-film transistors.

Oleic acid-stabilized silver nanoparticles prepared by a facile synthesis afforded highly conductive elements upon proper annealing. Regioregular polythiophene-based thin-film transistors (OTFTs) using source/drain electrodes prepared from these silver nanoparticles provided excellent field-effect characteristics, despite a significant difference between the work function of silver and the HOMO of polythiophene semiconductor. This was attributable to conductive doping of the semiconductor interface by residual oleic acid or its thermally transformed derivative from the silver electrodes, thus enabling ohmic contact formation. This is in sharp contrast to the OTFTs with silver electrodes fabricated from both vacuum deposition and oleylamine-stabilized silver nanoparticles, which exhibited markedly lower mobility and current on/off ratio, a consequence of energetic mismatch of the electrode/semiconductor pairs.

Journal Article↗
PubMed2002

Silver complexes with unsaturated thiacrown ethers: inclusion behavior of conformationally restricted macrocycles.

The reactions of 18- and 21-membered unsaturated thiacrown ethers, 18-UT-6 and 21-UT-7, with CF(3)COOAg in acetone afforded novel silver(I) complexes Ag(I)(18-UT-6)(CF(3)COO) and Ag(I)(2)(21-UT-7)(CF(3)COO)(2), respectively. The crystal structure of Ag(I)(18-UT-6)(CF(3)COO) shows that the silver atom occupies the cavity of the 18-UT-6 and the geometry around the silver atom has a distorted five-coordinate square pyramidal arrangement. The crystal structure of Ag(I)(2)(21-UT-7)(CF(3)COO)(2) shows that the two silver atoms and all sulfur atoms are nearly coplanar and the two trifluoroacetate groups are located at the opposite sides of the plane. The stoichiometry for the complexation of 15-UT-5, 18-UT-6, and 21-UT-7 with CF(3)COOAg in solution was examined by (1)H NMR measurement. The titration plots of 15-UT-5 and 21-UT-7 show a distinct inflection point at 1:1 and 2:1 metal/macrocycle ratios, respectively, whereas the plot of 18-UT-6 gradually changes at the range of 1:1 to 2:1. From these results, 15-UT-5 and 21-UT-7 were found to show inclusion selectivity for number of silver ions, respectively, whereas 18-UT-6 showed low selectivity for the inclusion number of metals. Comparison of the oxidation and reduction potentials of the silver(I) complexes with those of free macrocycles and CF(3)COOAg revealed that unsaturated thiacrown ethers become difficult to be oxidized by complexation with CF(3)COOAg, and CF(3)COOAg becomes difficult to be reduced by complexation with unsaturated thiacrown ethers.

Journal Article↗