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PubMed2006

Dendron-like growth of silver nanoparticles using a water-soluble oligopeptide.

A dendron-like nanostructure of silver was grown in solution using a water-soluble tetrapeptide Tyr-Aib-Tyr-Val (Aib, alpha-amino isobutyric acid), silver nitrate, and methanol. These structures are composed of silver nanoparticles having a bimodal size distribution with the median diameters around 2.0 and 19.5 nm, respectively. The dendron-like growth is ascribed to the effect of the local electric field generated by the dipoles associated with the peptide molecules. The optical absorption spectra have been analyzed by Mie scattering theory, which shows that there is a metal-nonmetal transition in silver particles having diameters less than approximately 2.0 nm.

Dendrimers↗
PubMed2006

Formation of silver nanoparticles in deoxyribonucleic acid-poly(o-methoxyaniline) hybrid: a novel nano-biocomposite.

A novel nano-biocomposite of silver and poly(o-methoxy aniline) (POMA)/DNA hybrid has been prepared by adding DNA solution to an aqueous solution of POMA (emeraldine base, EB) and AgNO(3) mixture. The mixture was aged for 10 days and was freeze-dried to form the hybrid nanocomposite (weight fraction of DNA = 0.75). FESEM pictures show a fibrillar network morphology of the biomolecular hybrid with silver nanoparticles on its surface. The TEM picture also corroborates silver nanoparticle formation in the biomolecular hybrid, and the denser population of nanoparticles in the TEM micrograph as compared to that in the SEM micrograph indicates that the nanoparticles are present inside the fibrils in greater proportion. The dc conductivity value of the hybrid indicates that POMA (EB) is doped by silver ion and the doped POMA form complexes with DNA through electrostatic interaction of the radical cation of POMA (emeraldine salt form, ES) and the DNA anion. During the doping process and Ag nanoparticle formation, a fluctuation of the pi band to polaron band transition peak occurs together with a complementary fluctuation of the polaron band to pi* band transition peak. After 53 h of aging, the former shows a slow but continuous red shift with aging time. This has been attributed to the slow uncoiling of POMA on the DNA surface. The conformation and crystal structure of DNA remain intact during the nano-biocomposite formation. The dc conductivity value of the nano-biocomposite is almost the same as that of the pure POMA-DNA hybrid at the same composition, but the I-V characteristic curve of the nano-biocomposite is somewhat different showing an insulating region on low applied voltage. At higher applied voltage, it shows a semiconducting property characterizing the large band gap semiconducting behavior of the nano-biocomposite.

Aniline Compounds↗
PubMed2004

Silver-colloid-nucleated cytochrome c superstructures encapsulated in silica nanoarchitectures.

We recently discovered that self-organized superstructures of the heme protein cytochrome c (cyt. c) are nucleated in buffer by gold nanoparticles. The protein molecules within the superstructure survive both silica sol-gel encapsulation and drying from supercritical carbon dioxide to form air-filled biocomposite aerogels that exhibit gas-phase binding activity for nitric oxide. In this investigation, we report that viable proteins are present in biocomposite aerogels when the nucleating metal nanoparticle is silver rather than gold. Silver colloids were synthesized via reduction of an aqueous solution of Ag+ using either citrate or borohydride reductants. As determined by transmission electron microscopy and UV-visible absorption spectroscopy, the silver nanoparticles vary in size and shape depending on the synthetic route, which affects the fraction of cyt. c that survives the processing necessary to form a biocomposite aerogel. Silver colloids synthesized via the citrate preparation are polydisperse, with sizes ranging from 1 to 100 nm, and lead to low cyt. c viability in the dried bioaerogels (approximately 15%). Protein superstructures nucleated at approximately 10-nm Ag colloids prepared via the borohydride route, including citrate stabilization of the borohydride-reduced metal, retain significant protein viability within the bioaerogels (approximately 45%).

Chemical Phenomena↗
PubMed2002

Susceptibility and features of the ultrastructure of Prototheca zopfii following exposure to copper sulphate, silver nitrate and chlorexidine.

One of the most important forms of the occurrence of protothecosis is bovine mastitis. Studies on the "in vivo" and "in vitro" susceptibility to antimicrobials have shown that the microorganism is resistant to most of them. Looking for alternative treatments this study aimed to study the susceptibility to copper sulphate (which has an important algicide effect) and silver nitrate (used in dairy cattle breeding for the cauterization of mammary glands) and also to chlorexidine (an important post-dipping anti-septic used in dairy practice), and the effect of these antimicrobials in the ultrastructure of Prototheca zopfii before and after the exposure to these drugs. The "in vitro" susceptibility tests to chlorexidine, silver nitrate and copper sulphate of the strains of Prototheca zopfii for the determination of their minimal microbicidal concentrations (MMC), were performed using the tube dilution method in Sabouraud dextrose broth and evaluation of colony growth after plating in Sabouraud dextrose agar. The MMCs of chlorexidine, copper sulphate and silver nitrate of the 50 strains tested were 0.01%, 0.1% and 0.3%, respectively. The tubes containing the material used in the antimicrobial susceptibility tests were prepared for the examination in an electron microscope. The untreated controls of P. zopfii showed a similar ultrastructural appearance with the typical characteristics of the microorganism. Cells exposed to silver nitrate showed changes suggesting thickness of the cell wall. Cells exposed to chlorexidine showed changes suggesting degradation of intra-cellular organelles present in the cytoplasm. P. zopfii treated with copper sulphate showed changes suggesting fibrilation of inner layer of cell wall.

Animals↗
PubMed2003

Complexation of silver and co-recovered metals with novel aza-crown ether macrocycles by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) is used to evaluate the metal binding selectivities of an array of novel caged macrocycles for silver, gold, copper, nickel, zinc, iron, lead, manganese and alkali metal ions. It is found that five of the new compounds display silver selectivity, and their relative affinities for various metals depend on the type, number, and arrangement of heteroatoms (N, O), the cavity size, and the presence of aromatic substituents. Alkali metal cation binding studies are used to evaluate the size-selectivities of the cavities of the macrocycles. Electronic structure calculation by B3LYP density function theory methods were used to model the metal complexes. The presence of nitrogen atoms in the macrocyclic ring is essential for silver selectivity over other transition metals and alkali metal ions, and the presence of aromatic groups also enhances silver avidity. Macrocycle 3, a triaza-18-crown-6 analog modified with two phenyl groups and a cage group, is capable of selective extraction of Ag+ from aqueous solutions in the presence of other transition metal ions and the most common alkali and alkaline earth metal ions.

Crown Ethers↗
PubMed1996

An assessment of the ability of a silver-releasing device to prevent bacterial contamination of urethral catheter drainage systems.

OBJECTIVE: To investigate the ability of a silver-releasing device to protect the catheterized bladder from infection by blocking the ascending migration of bacteria from contaminated urine-drainage bags. MATERIALS AND METHODS: A simple physical model of the catheterized bladder and drainage system was used with the device located in the drainage-tube just below the sampling port. Urine was supplied to the model at 1.0 mL/min and the drainage bag was contaminated with Pseudomonas aeruginosa, Escherichia coli and Proteus mirabilis. Over 10 days, urine from the bag, catheter sampling-port and bladder were examined for contamination. RESULTS: Bacteriological analysis showed that the mean time for test organisms to reach the sampling ports of four different control bag systems ranged from 5.7 to 7.7 days. Urine from the sampling ports of the test systems incorporating the silver device remained sterile for 10 days. The device also prevented the growth of the large populations of bacteria (10(8) colony-forming units per mL) that occurred in the control bags. While scanning electron microscopy showed the formation of bacterial biofilm throughout the control drainage systems, no bacterial colonization was visible on the surfaces of the test systems. Chemical analysis established that the devices consistently generated concentrations of silver in urine ranging from 1.0 to 2.0 micrograms/mL. CONCLUSION: The incorporation of the silver-releasing device into the drainage systems produced an antibacterial barrier which protected the catheterized bladder from intraluminal contamination for at least 10 days. These in vitro tests suggest a useful role for the device in controlling infection in patients undergoing short-term indwelling bladder catheterization.

Bacterial Infections↗
PubMed2000

Biodetoxification of silver-cyanide from electroplating industry wastewater.

A bacterial consortium capable of utilizing metal-cyanides as a source of nitrogen was used to develop a microbiological process for the detoxification of silver-cyanide from electroplating wastewater. When the treatment was carried out in a 27-l rotating biological contactor (R3C) in continuous mode, the system could achieve > 99.5% removal of 0.1 mmol l(-1) silver-cyanide (approximately 5 mg l(-1) cyanide and 10 mg l(-1) silver) in 10 h with sugarcane molasses (0.1 ml l(-1)) as carbon source. The silver ions set free during biodegradation were efficiently adsorbed by the bacterial biomass. The RBC-treated effluent was found to be safe for discharge into the environment, as confirmed by chemical analysis and fish bioassay studies.

Animals↗
PubMedDate not supplied

Comparative trial of octyl-cyanoacrylate and silver sulfadiazine for the treatment of full-thickness skin wounds.

A prospective, randomized, blinded, controlled experimental trial was performed in pigs to compare the rates of reepithelialization of 126 full-thickness cutaneous 4-mm punches treated with an octyl-cyanoacrylate spray, silver sulfadiazine, or a dry gauze (controls). Full thickness biopsies were taken 7, 14, or 30 days later for histopathological evaluation of hematoxylin and eosin stained tissue sections by a dermatopathologist. The primary outcome measure was the proportion of wounds completely re-epithelialized at days 7 and 14. Secondary outcomes were the rates of infection, foreign body reactions, and the depth of any resulting cutaneous dells measured with a micrometer. Between-group comparisons were performed with ANOVA or Chi-square tests. Octyl-cyanoacrylate treated wounds re-epithelialized more slowly, as fewer wounds treated with octyl-cyanoacrylate were re-epithelialized at day 7 in comparison with silver sulfadiazine or control wounds (50% vs. 90% vs. 100%, p < 0.001). There were no infections or foreign body type reactions. Amounts of granulation tissue were similar among groups. Octyl-cyanoacrylate wounds were more depressed than silver sulfadiazine wounds at days 7 and 14 yet had similar histopathological characteristics at day 30. We conclude that treatment of small, full thickness cutaneous wounds with octyl-cyanoacrylate results in delayed re-epithelialization and dermal repair in comparison with silver sulfadiazine, yet it does not result in any foreign body-type reaction. However, by 30 days, histopathological wound characteristics were similar in all groups.

Animals↗
PubMed2005

Healing characteristics of a new silver-coated, gelatine impregnated vascular prosthesis in the porcine model.

OBJECTIVES: To investigate the intraluminal and extraluminal healing behaviour of a new metallic silver coated, gelatine impregnated vascular graft. DESIGN: Comparative animal experimental investigation with randomisation of the animals to control and experimental groups. MATERIAL AND METHODS: 24 pigs were assigned to two control and two experimental groups. The prostheses were interposed in the pigs' infrarenal aorta. For the evaluation, macroscopic, histological and immunohistochemical criteria were applied. RESULTS: The macroscopic evaluation after explantation of the prosthesis revealed similar healing characteristics in the control and experimental groups. The microscopic determination of neo-intimal thickness showed no significant differences between the groups; nor did the immunohistochemical investigations show any significant difference between the control group and the silver-coated prosthesis group. CONCLUSIONS: No disadvantage of the silver coating in terms of healing and graft patency was found. A possible advantage in terms of the antibacterial effect of the silver coating must be investigated in the clinical setting.

Animals↗
PubMed2006

[Corneal and conjunctival findings in systemic silver intoxication].

BACKGROUND: Chronic silver intoxication is a rare disease and therefore the typical ocular findings may be missed. Based on a case with severe intoxication, the clinical and histological findings as well as the prognosis in argyria are presented. HISTORY: A 33-years-old-employee of a battery production plant developed a biopsy proven systemic argyria. On slit lamp examination the conjunctiva showed a dark, blue-grey discoloration in the areas of the tear flow and the small conjunctival arteries. Diffuse silver deposits were noticed on the level of Descemet's membrane without endothelial damage. Silver deposits were also visible in the trabecular meshwork. Chemical reaction of the silver particles upon exposure to UV light results in irreversible tissue discoloration. Without options for an effective treatment, early diagnosis and prevention of overexposure are most important. CONCLUSIONS: The typical ocular findings in systemic argyria are helpful in occupational medicine for establishing the correct diagnosis.

Adult↗
PubMed2002

Silver nitrate injury in the rat sciatic nerve: a model of facial nerve injury.

BACKGROUND: An unpublished communication of a permanent facial paralysis secondary to silver nitrate application in a postoperative mastoid cavity with a dehiscent facial nerve raises concern regarding its neurotoxicity. This study was performed to examine functional neural injury and the morphology of nerve injury due to silver nitrate contact with a peripheral motor nerve. METHODS: Sprague-Dawley male rats were assigned to a sham surgery group or to a group where silver nitrate was applied directly to a surgically exposed sciatic nerve for 1, 5, or 10 seconds. Individual walking track data were collected on postoperative days (POD) 1, 4, 7, and 14, and the Sciatic Functional Index (SFI) was calculated to assess neural function. On POD 14, the cauterized nerve was harvested, and the histologic axon loss of each specimen was graded. RESULTS: In all experimental groups, the most severe functional loss was noted on POD 1. At POD 14 the greatest neural recovery was observed in the 1-second group, whereas the 5- and 10-second cautery groups demonstrated a significantly worse deficit. A moderate or greater degree of axon loss was observed in 50% of animals injured for 1 second and nearly all animals injured for 5 or 10 seconds. CONCLUSION: Functional and neuropathologic data demonstrate that silver nitrate causes significant injury to the rat sciatic nerve. A 5-second cautery causes greater functional impairment and more severe axonal loss than a 1-second injury.

Animals↗
PubMed2003

Scar-localized argyria secondary to silver sulfadiazine cream.

Silver sulfadiazine cream is a topical antibacterial agent that combines the antibacterial effects of both silver and sulfadiazine. Its reported cutaneous side effects include hypersensitivity reactions, allergic contact dermatitis, erythema multiforme, and systemic argyria. We report the case of a patient who had localized argyria develop in a scar after the use of silver sulfadiazine cream. In this case, the silver sulfadiazine cream was applied to and argyria developed within a postsurgical wound and area of severe contact dermatitis.

Administration, Cutaneous↗
PubMed1979

Trace polypeptides in cellular extracts and human body fluids detected by two-dimensional electrophoresis and a highly sensitive silver stain.

Development of a highly sensitive silver stain permits the characterization of trace cellular and body fluid proteins separated by the two-dimensional electrophoresis technique of O'Farrell. Many of the proteins detected by the silver stain in urine, spinal fluid, amniotic fluid, and cells were undetected with the widely used Coomassie blue stain. Trace polypeptides observed in Escherichia coli cell lysates with this silver stain could be detected previously only by growth in radioactive precursors followed by lengthy autoradiography. In situations that do not permit the use of radioactive labeling, as in human clinical studies, the enhanced ability to detect proteins achieved by the silver stain will facilitate metabolic studies and the screening for protein abnormalities in mutational studies and in genetic diseases.

Amniotic Fluid↗
PubMed1995

Copper and silver transport by CopB-ATPase in membrane vesicles of Enterococcus hirae.

The P-type ATPase, CopB, of Enterococcus hirae is required for the copper resistance displayed by this organism and thus was postulated to be a copper pump. Using 64Cu+ and 110mAg+, we here show ATP-driven copper and silver accumulation catalyzed by CopB in native inside-out membrane vesicles of E. hirae. CopB ATPase exhibited an apparent Km for Cu+ and Ag+ of 1 microM and for ATP of 10 microM. Transport was maximal at pH 6 and had an apparent Vmax of 0.07 nmol.min-1.mg-1 for both copper and silver transport. Vanadate displayed a biphasic effect on transport: maximal inhibition was observed at 40 microM vanadate for copper transport and 60 microM for silver transport, respectively. At higher vanadate concentrations, these inhibitions were reversed. The CopB ATPase of E. hirae is thus a pump for the extrusion of monovalent copper and silver ions, with copper probably being the natural substrate.

Adenosine Triphosphatases↗
PubMed1997

Aneuploidy in sclerosing adenosis may predict an increased risk of malignancy. A study using the AgNOR silver stain.

Sclerosing adenosis (SA) of the breast if a disease associated with an increase relative risk of malignancy. The exact incidence and factors influencing malignant transformation in association with SA are not well established. Two counts of the AgNOR silver staining technique have been correlated with ploidy and proliferative activity. The first count which is the mean number of AgNOR granules (mAgNOR), correlates with ploidy. The second count is the percentage of nuclei exhibiting > or = 5 AgNORs/nucleus (pAgNOR) and reflects proliferative activity. The hypothesis in the current study was that aneuploidy, as determined by the AgNOR silver staining technique, may potentially identify lesions of SA with an increased association with malignant breast disease. The AgNOR silver staining technique was performed on 69 cases of SA with the application of the two counts. Of these cases 53 were not associated with malignancy and 16 were associated with synchronous or metachronous carcinoma of the breast, these being 11 cases of invasive ductal carcinoma (IDC), four cases of ductal carcinoma in situ (DCIS) and one case of lobular carcinoma in situ (LCIS). The patient ages ranged from 27 to 84 years (median 53 years) with a median follow up of 28 months. Six of the 53 cases of SA no associated with malignancy (11%) had aneuploid mAgNOR counts of > or = 2.4 whereas 12 of the 16 cases associated with carcinoma (80%) had such counts (p < 0.0005). This included nine cases of IDC, two cases of DCIS and the case of LCIS. Of the six aneuploid cases not associated with malignancy, two cases showed cytological atypia, one case was associated with atypical ductal hyperplasia and one case was seen in a leukemic patient who had received chemotherapy and radiation therapy. The pAgNOR counts showed a statistically less significant correlation with malignancy (p < 0.03). These findings suggest that aneuploidy, measured by the AgNOR silver stein, seen in SA may help identify lesions with a higher relative risk of being associated with breast carcinoma and hence that may require more aggressive management than diploid ones.

Adult↗
PubMedDate not supplied

Simultaneous visualization of rDNA clusters and the nucleolus by combining fluorescence in situ hybridization and silver staining.

We designed two procedures to visualize simultaneously clusters of ribosomal RNA genes (rDNA) and the nucleolus in plant cells. The procedures combine fluorescence in situ hybridization (FISH) to visualize the rDNA clusters and silver staining to observe the nucleolus. When FISH is followed by silver staining, many minute FISH signals are localized in the nucleolus, and several large FISH signals are seen on the nucleolar periphery. When FISH was applied to the specimens with silver nitrate staining, large FISH signals were visualized in the nucleoplasm associated with the nucleolar periphery, but no signals were seen in the nucleoli. Thus, the two combinations of FISH and silver staining provided different details regarding the arrangement of rDNA clusters in the nucleolus of plant cells.

Allium↗
PubMed2000

Healing of porcine donor sites covered with silver-coated dressings.

OBJECTIVE: To compare rates of healing of donor sites in pigs between those dressed with silver-coated dressings and those dressed with petrolatum-impregnated absorbent gauze. DESIGN: Open study with each animal acting as its own control. SETTING: University research facility, Canada. ANIMALS: 6 young specific-pathogen-free domestic pigs. INTERVENTIONS: A total of 72 wounds about 1 cm x 2 cm x 0.4 mm were made in rows of eight on each pig with a dermatome. They were divided into three groups of 24, and dressed with petrolatum gauze, or silver-coated dressings moistened with sterile water either once only or daily for 10 days. All dressings were secured in place with an elastic bandage. MAIN OUTCOME MEASURES: Erythema, infection, epidermal migration, and healing. RESULTS: Wounds dressed with moistened silver-coated dressings re-epithelialised significantly more quickly. This resulted in complete re-epithelialisation within 70% of the time taken by those wounds dressed with petrolatum gauze. CONCLUSION: Silver-coated dressings provide a moist environment for the healing wound combined with an effective antimicrobial agent, and this significantly accelerates healing compared with wounds dressed with traditional petrolatum gauze dressings.

Animals↗
PubMedDate not supplied

Rapid Bielschowsky silver impregnation method using microwave heating.

The Bielschowsky silver impregnation method has been used extensively to demonstrate neuronal processes including dendrites, axons and neurofibrils. In this study, we examined the differences in the time required for and the staining quality of the Bielschowsky method for neuronal processes when microwave heating was used instead of processing at room temperature. For this purpose, a control group of sections stained according to the conventional method at room temperature was compared to an experimental group stained in a microwave oven at 180 W for 2, 4 and 1 min in 2% silver nitrate, ammoniacal silver nitrate and gold chloride, respectively. Light microscopic examination demonstrated that the normal structure was preserved in both groups and that there was no difference in the staining quality between the control and the microwave groups. In addition, staining time for this procedure was reduced to 8 min by using the microwave oven. Our study revealed that microwave irradiation can be used safely for Bielschowsky silver impregnation of neuronal tissues.

Animals↗