Testing nano-silver food packaging to evaluate silver migration and food spoilage bacteria on chicken meat.

PubMed

Gallocchio, Federica; Cibin, Veronica; Biancotto, Giancarlo; Roccato, Anna; Muzzolon, Orietta; Carmen, Losasso; Simone, Belluco; Manodori, Laura; Fabrizi, Alberto; Patuzzi, Ilaria; Ricci, Antonia

2016-06-01

Migration of nanomaterials from food containers into food is a matter of concern because of the potential risk for exposed consumers. The aims of this study were to evaluate silver migration from a commercially available food packaging containing silver nanoparticles into a real food matrix (chicken meat) under plausible domestic storage conditions and to test the contribution of such packaging to limit food spoilage bacteria proliferation. Chemical analysis revealed the absence of silver in chicken meatballs under the experimental conditions in compliance with current European Union legislation, which establishes a maximum level of 0.010 mg kg(-1) for the migration of non-authorised substances through a functional barrier (Commission Regulation (EU) No. 10/2011). On the other hand, microbiological tests (total microbial count, Pseudomonas spp. and Enterobacteriaceae) showed no relevant difference in the tested bacteria levels between meatballs stored in silver-nanoparticle plastic bags or control bags. This study shows the importance of testing food packaging not only to verify potential silver migration as an indicator of potential nanoparticle migration, but also to evaluate the benefits in terms of food preservation so as to avoid unjustified usage of silver nanoparticles and possible negative impacts on the environment.

Nanoparticles in treatment of thermal injured rats: Is it safe?

NASA Astrophysics Data System (ADS)

Melo, P. S.; Marcato, P. D.; Huber, S. C.; Ferreira, I. R.; de Paula, L. B.; Almeida, A. B. A.; Durán, N.; Torsoni, S.; Seabra, A. B.; Alves, O. L.

2011-07-01

The aim of this study was to assess whether thermal trauma induced oxidative stress altered the balance between oxidant and antioxidant systems in the blood of burn wound rats in the absence and presence of silver nanoparticles and S-nitrosoglutathione, GSNO. Free silver nanoparticles, free GSNO and silver nanoparticles + GSNO had no cytotoxic effects. Under anesthesia, the shaved dorsum of the rats was exposed to 90°C (burn group) water bath. Studied compounds were administered topically immediately and at 28 days after the burn injury, four times a day. Silver nanoparticles and silver nanoparticles + GSNO were no toxic in vitro and in vivo. There were no significant differences in the levels of urea, creatinine, aminotransferases and hematological parameters, in control-burn groups (free silver nanoparticles) and treated-burn groups (free GSNO or silver nanoparticles + GSNO). There were no differences in lipid peroxidation and in the levels of protein carbonyls and glutathione, used as oxidative stress markers. A little inflammatory cell response, papillary dermis vascularization, fibroblasts differentiated into contractile myofibroblasts and the presence of a large amount of extracellular matrix were evidenced in treated groups following skin injury. These results indicate that silver nanoparticles and GSNO may provide an effective action on wound healing.

A silver ion water sterilization system

NASA Technical Reports Server (NTRS)

Parry, E. P.

1971-01-01

Small amounts of silver are incorporated in mixture of ion exchange resins, and water passing through this mixture is thus exposed to silver ion concentration. System is useful in self-contained water systems except city water systems where residual chlorine level is stipulated.

Novel silver-based nanoclay as an antimicrobial in polylactic acid food packaging coatings.

PubMed

Busolo, Maria A; Fernandez, Patricia; Ocio, Maria J; Lagaron, Jose M

2010-11-01

This paper presents a comprehensive performance study of polylactic acid (PLA) biocomposites, obtained by solvent casting, containing a novel silver-based antimicrobial layered silicate additive for use in active food packaging applications. The silver-based nanoclay showed strong antimicrobial activity against Gram-negative Salmonella spp. Despite the fact that no exfoliation of the silver-based nanoclay in PLA was observed, as suggested by transmission electron microscopy (TEM) and wide angle X-ray scattering (WAXS) experiments, the additive dispersed nicely throughout the PLA matrix to a nanoscale, yielding nanobiocomposites. The films were highly transparent with enhanced water barrier and strong biocidal properties. Silver migration from the films to a slightly acidified water medium, considered an aggressive food simulant, was measured by stripping voltammetry. Silver migration accelerated after 6 days of exposure. Nevertheless, the study suggests that migration levels of silver, within the specific migration levels referenced by the European Food Safety Agency (EFSA), exhibit antimicrobial activity, supporting the potential application of this biocidal additive in active food-packaging applications to improve food quality and safety.

Antibacterial potency of V.A.C. GranuFoam Silver(®) Dressing.

PubMed

Sachsenmaier, Saskia; Peschel, Andreas; Ipach, Ingmar; Kluba, Torsten

2013-10-01

V.A.C.(®) GranuFoam™ therapy is regularly used in the surgical therapy of infected wounds and soft tissue injuries. Silver nanoparticles can destroy bacterial cell walls and inhibit enzymes for cell replication. Silver dressings are therefore successfully used for many indications in wound therapy. In this study, we investigated the antimicrobial potency of ionic silver released from the silver-coated V.A.C.(®) GranuFoam™ during vacuum therapy. Silver dressing was exposed to agar plates populated with bacteria to measure silver release. A total of 15 agar plates colonised with either Staphylococcus aureus populations or with Staphylococcus epidermidis, were loaded with V.A.C. GranuFoam Silver(®) Dressing polyurethane foam (KCI, San Antonio, Texas). Each of 13 pieces of silver-coated foam was applied to an agar plate. Two plates were loaded with conventional black foam without any coating. After connecting to a vacuum pump, the vacuum therapy of the 15 plates lasted 5 days. The zone of inhibition of bacterial growth around the foam was measured daily. Silver release was also determined as a function of time. At each time point, there was evidence of silver in the agar independent of bacterial colonisation. The S. aureus agar showed a consecutive increase in silver concentration from baseline upon 48 h after exposure to the negative pressure of V.A.C. therapy. An increasing mean silver level after 48, 72 and 96 h was measured under V.A.C. therapy with a peak value after 120 h. In contrast, the results from the S. epidermidis plates did not follow a linear pattern. At the beginning of vacuum therapy, we documented a rise in silver concentration. After 48-96h, the silver levels fluctuated. A maximum zone of inhibition in both bacterial colonised plates (S. aureus and S. epidermidis) was found 39 h after the start of the V.A.C. GranuFoam Silver(®) therapy. From our results, we confirmed the antimicrobial effect of the silver ions against S. aureus and S. epidermidis under continuous V.A.C. GranuFoam(®) Silver therapy with a negative pressure of 25 mmHg. Furthermore we could quantify the amounts of silver, which were released from the foam under negative pressure as a function of time. Copyright © 2013 Elsevier Ltd. All rights reserved.

Colloidal silver fabrication using the spark discharge system and its antimicrobial effect on Staphylococcus aureus.

PubMed

Tien, Der-Chi; Tseng, Kuo-Hsiung; Liao, Chih-Yu; Tsung, Tsing-Tshih

2008-10-01

Nanoscale techniques for silver production may assist the resurgence of the medical use of silver, especially given that pathogens are showing increasing resistance to antibiotics. Traditional chemical synthesis methods for colloidal silver (CS) may lead to the presence of toxic chemical species or chemical residues, which may inhibit the effectiveness of CS as an antibacterial agent. To counter these problems a spark discharge system (SDS) was used to fabricate a suspension of colloidal silver in deionized water with no added chemical surfactants. SDS-CS contains both metallic silver nanoparticles (Ag(0)) and ionic silver forms (Ag(+)). The antimicrobial affect of SDS-CS on Staphylococcus aureus was studied. The results show that CS solutions with an ionic silver concentration of 30 ppm or higher are strong enough to destroy S. aureus. In addition, it was found that a solution's antimicrobial potency is directly related to its level of silver ion concentration.

Phenolic Compounds and Expression of 4CL Genes in Silver Birch Clones and Pt4CL1a Lines

PubMed Central

Sutela, Suvi; Hahl, Terhi; Tiimonen, Heidi; Aronen, Tuija; Ylioja, Tiina; Laakso, Tapio; Saranpää, Pekka; Chiang, Vincent; Julkunen-Tiitto, Riitta; Häggman, Hely

2014-01-01

A small multigene family encodes 4-coumarate:CoA ligases (4CLs) catalyzing the CoA ligation of hydroxycinnamic acids, a branch point step directing metabolites to a flavonoid or monolignol pathway. In the present study, we examined the effect of antisense Populus tremuloides 4CL (Pt4CL1) to the lignin and soluble phenolic compound composition of silver birch (Betula pendula) Pt4CL1a lines in comparison with non-transgenic silver birch clones. The endogenous expression of silver birch 4CL genes was recorded in the stems and leaves and also in leaves that were mechanically injured. In one of the transgenic Pt4CL1a lines, the ratio of syringyl (S) and guaiacyl (G) lignin units was increased. Moreover, the transcript levels of putative silver birch 4CL gene (Bp4CL1) were reduced and contents of cinnamic acid derivatives altered. In the other two Pt4CL1a lines changes were detected in the level of individual phenolic compounds. However, considerable variation was found in the transcript levels of silver birch 4CLs as well as in the concentration of phenolic compounds among the transgenic lines and non-transgenic clones. Wounding induced the expression of Bp4CL1 and Bp4CL2 in leaves in all clones and transgenic lines, whereas the transcript levels of Bp4CL3 and Bp4CL4 remained unchanged. Moreover, minor changes were detected in the concentrations of phenolic compounds caused by wounding. As an overall trend the wounding decreased the flavonoid content in silver birches and increased the content of soluble condensed tannins. The results indicate that by reducing the Bp4CL1 transcript levels lignin composition could be modified. However, the alterations found among the Pt4CL1a lines and the non-transgenic clones were within the natural variation of silver birches, as shown in the present study by the clonal differences in the transcripts levels of 4CL genes, soluble phenolic compounds and condensed tannins. PMID:25502441

Sensitivity of the spiny dogfish (Squalus acanthias) to waterborne silver exposure.

PubMed

De Boeck, G; Grosell, M; Wood, C

2001-10-01

The physiological effects of waterborne silver exposure (added as AgNO(3)) on spiny dogfish, Squalus acanthias, were evaluated at 30, 200 and 685 microg silver per l in 30 per thousand seawater. These concentrations cover the toxic range observed for freshwater teleosts, where silver is extremely toxic, to seawater teleosts which tolerate higher silver concentrations. However, these levels are considerably higher than those that occur in the normal environment. At 685 microg l(-1), dogfish died within 24 h. Causes of death were respiratory as well as osmoregulatory failure. Arterial P(a)O(2) rapidly declined below 20 Torr, and blood acidosis (both respiratory and metabolic) occurred. Urea excretion increased dramatically and plasma urea dropped from 340 to 225 mM. There were pronounced increases in plasma Na(+), Cl(-), and Mg(2+), indicative of ionoregulatory failure due to increased diffusive permeability as well as inhibited NaCl excretion. At 200 microg l(-1), fish died between 24 and 72 h of silver exposure. The same physiological events occurred with a small time delay. At 30 microg l(-1), effects were much less severe, although slight mortality (12.5%) still occurred. Respiratory alkalosis occurred, together with moderate elevations in plasma Na(+) and Cl(-) levels. Silver accumulated to the highest concentrations on gills, with only low levels in the intestine, in accord with the virtual absence of drinking. Na(+)/K(+)-ATP-ase activities of gill and rectal gland tissue were impaired at the highest silver concentration. Normal gill function was impaired due to swelling and fusion of lamellae, lamellar aneurism and lifting of the lamellar epithelium. Our results clearly indicate that this elasmobranch is much more sensitive (about 10-fold) to silver than marine teleosts, with silver's toxic action exerted on the gill rather than on the intestine, in contrast to the latter.

Impact of moderate silver carp biomass gradient on zooplankton communities in a eutrophic reservoir. Consequences for the use of silver carp in biomanipulation.

PubMed

Domaizon, I; Dévaux, J

1999-07-01

We examined the impacts of moderate gradient silver carp biomass (five levels from 0 to 36 g.m-3, i.e. about 0-792 kg.ha-1) on zooplankton communities of the eutrophic Villerest reservoir (France). During our mesocosm experiment changes in zooplankton assemblages were dependent on silver carp biomass. In the fishless and low fish biomass treatments, zooplankton abundance increased through time, owing to a peak in cladoceran density, but decreased (mainly cladocerans) at highest fish biomass. Copepods and rotifers were less affected at the highest fish biomass and dominated zooplankton communities. We highlighted that the presence of high silver carp biomass could lead to changes in phytoplankton assemblage via the impact on herbivorous zooplankton. Since silver carp efficiently graze on particles > 20 microns, the suppression of herbivorous cladocerans could result in an increase in small size algae (< 20 microns) abundance since these species would be released from grazers as well as competitors (large algae grazed by silver carp) and nutrients levels would be enhanced by fish internal loading. Our results showed that the use of low silver carp biomass (< 200 kg.ha-1) would allow us to minimize these negative effects.

Branchial versus intestinal silver toxicity and uptake in the marine teleost Parophrys vetulus.

PubMed

Grosell, M; Wood, C M

2001-10-01

Exposure to elevated waterborne silver as AgNO3 (4.07 microM=448 microg l(-1)) in seawater resulted in osmoregulatory disturbance in the lemon sole (Parophrys vetulus). The main effects were increased plasma Na+ and Cl- concentrations which translated into increased plasma osmolality. Plasma Mg2+ levels were also slightly increased after 96 h exposure. Using radioisotopic flux measurements, a 50% reduction in branchial unidirectional Na+ extrusion was observed after 48 h silver exposure. By applying an intestinal perfusion approach, we were able to separate and thus quantify the intestinal contribution to the observed silver-induced physiological disturbance and internal silver accumulation. This analysis revealed that the intestinal contribution to silver-induced ionoregulatory toxicity was as high as 50-60%. In marked contrast, internal silver accumulation (in liver and kidney) was found to be derived exclusively from uptake across the gills. Drinking of silver-contaminated seawater resulted in substantial silver accumulation in the intestinal tissue (but apparently not silver uptake across the intestine), which probably explains the intestinal contribution to silver-induced physiological disturbance.

The Effects of Toxic Particles in Human Lung Cells - Research Area 8. Life Sciences

DTIC Science & Technology

2016-01-05

Characterization of Metal Nanoparticles 2.1. Synthesis and Characterization of Nanoparticles We generated and tested a silver colloid solution with a mean... silver and gold nanoparticle -induced effects; and 6) Assess metal levels in whale skin biopsies in the Gulf of Mexico. The first five aims focused...We found that silver , gold and titanium dioxide nanoparticles were relatively non-toxic. Only silver 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND

Mechanical, electrical, and thermal expansion properties of carbon nanotube-based silver and silver-palladium alloy composites

NASA Astrophysics Data System (ADS)

Pal, Hemant; Sharma, Vimal

2014-11-01

The mechanical, electrical, and thermal expansion properties of carbon nanotube (CNT)-based silver and silver-palladium (10:1, w/w) alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver-palladium nanocomposite with CNT resulted in increases in the hardness and Young's modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion (CTE). The hardness and Young's modulus of the nanocomposites were increased by 30%-40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver-palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.

Migration of silver from commercial plastic food containers and implications for consumer exposure assessment.

PubMed

von Goetz, Natalie; Fabricius, Lars; Glaus, Reto; Weitbrecht, Volker; Günther, Detlef; Hungerbühler, Konrad

2013-01-01

Food storage containers with embedded silver as an antibacterial agent promise longer durability of food. For risk assessment the release of this silver into the stored food and resulting human exposure need to be known. For the purpose of exposure assessment, silver migration from commercial plastic containers with declared content of 'nano-' or 'micro-silver' into different food simulants (water, 10% ethanol, 3% acetic acid, olive oil) was quantitatively determined by ICP-MS and the form of the released silver was investigated. The highest migration of silver was observed for the acidic food simulant with 30 ng silver cm(-2) contact surface within 10 days at 20°C. In a second and third use cycle, migration dropped by a factor of up to 10, so that the maximum cumulated release over three use cycles was 34 ng cm(-2). The silver release over time was described using a power function and a numerical model that simulates Fickian diffusion through the plastic material. The released silver was found to be in ionic form, but also in the form of silver nanoparticles (around 12%). Consumer exposure to the total amount of silver released from the food containers is low in comparison with the background silver exposure of the general population, but since natural background concentrations are only known for ionic silver, the exposure to silver nanoparticles is not directly comparable with a safe background level.

Negative pressure and nanocrystalline silver dressings for nonhealing ulcer: A randomized pilot study.

PubMed

Sáez-Martín, Luis C; García-Martínez, Lourdes; Román-Curto, Concepción; Sánchez-Hernández, Miguel V; Suárez-Fernández, Ricardo M

2015-01-01

Chronic wounds have a high prevalence and wound care, treatment, and prevention consume large quantities of resources. Chronic wounds are a growing challenge for clinicians. A prospective randomized pilot study was conducted to assess the effectiveness in terms of reduction in area and safety of the combined use of negative-pressure wound therapy and nanocrystalline silver dressings as compared to negative pressure wound therapy (NPWT) alone in the management of outpatients with chronic wounds. A total of 17 patients were included in the study, 10 were treated with the combined method and 7 with NPWT. Patients were followed for 6 weeks, with a final assessment at 3 months. Clinical improvement, microbiologic data, and toxicity of silver were evaluated. The antibacterial effects of ionic silver together with the development of granulation tissue promoted by NPWT reduced significantly the median extension of the wound between weeks 3 and 6 of treatment. The combination with silver also reduced bacterial colonization with Pseudomonas aeruginosa and the bacterial load on the surface of the wound. The silver levels correlated positively with the extension of the wound, although in none of the patients' toxic levels were reached. The combination of NPWT with nanocrystalline silver dressings was safe and as effective as NPWT alone. © 2015 by the Wound Healing Society.

[Silver-Russell syndrome with panhypopituitarism (author's transl)].

PubMed

Stögmann, W; Borkenstein, M; Grubbauer, H M

1978-11-01

This is a report on a 14 years old boy suffering from the unusual combination of Silver-Russell syndrome with panhypopituitarism. The Silver-Russell syndrome is a special form of primordial dwarfism characterised by congenital asymmetry, craniofacial dysmorphy and other anomalies. Its cause is unknown, intrauterine noxes and genetical factors are discussed. In the most cases results of hormone determinations are normal, but also cases with elevated or very low hormone levels were published. This is the first report about a Silver-Russell syndrome combined with panhypopituitarism.

Silver Dissolution and Release from Ceramic Water Filters.

PubMed

Mittelman, Anjuliee M; Lantagne, Daniele S; Rayner, Justine; Pennell, Kurt D

2015-07-21

Application of silver nanoparticles (nAg) or silver nitrate (AgNO3) has been shown to improve the microbiological efficacy of ceramic water filters used for household water treatment. Silver release, however, can lead to undesirable health effects and reduced filter effectiveness over time. The objectives of this study were to evaluate the contribution of nanoparticle detachment, dissolution, and cation exchange to silver elution, and to estimate silver retention under different influent water chemistries. Dissolved silver (Ag(+)) and nAg release from filter disks painted with 0.03 mg/g casein-coated nAg or AgNO3 were measured as a function of pH (5-9), ionic strength (1-50 mM), and cation species (Na(+), Ca(2+), Mg(2+)). Silver elution was controlled by dissolution as Ag(+) and subsequent cation exchange reactions regardless of the applied silver form. Effluent silver levels fell below the drinking water standard (0.1 mg/L) after flushing with 30-42 pore volumes of pH 7, 10 mM NaNO3 at pH 7. When the influent water was at pH 5, contained divalent cations or 50 mM NaNO3, silver concentrations were 5-10 times above the standard. Our findings support regular filter replacement and indicate that saline, hard, or acidic waters should be avoided to minimize effluent silver concentrations and preserve silver treatment integrity.

FINE GRAIN NUCLEAR EMULSION

DOEpatents

Oliver, A.J.

1962-04-24

A method of preparing nuclear track emulsions having mean grain sizes less than 0.1 microns is described. The method comprises adding silver nitrate to potassium bromide at a rate at which there is always a constant, critical excess of silver ions. For minimum size grains, the silver ion concentration is maintained at the critical level of about pAg 2.0 to 5.0 during prectpitation, pAg being defined as the negative logarithm of the silver ion concentration. It is preferred to eliminate the excess silver at the conclusion of the precipitation steps. The emulsion is processed by methods in all other respects generally similar to the methods of the prior art. (AEC)

The effects of nanosilver on egg quality traits in laying Japanese quail

NASA Astrophysics Data System (ADS)

Farzinpour, Amjad; Karashi, Naser

2013-04-01

Silver nanoparticles could prove to be a valuable alternative raw material for antibiotics and disinfectants as it is relatively free of adverse effects. Nanosilver is now been put to practical use in commonly used items, such as, clothes, electric home appliances, and electronic industry, but has not been widely applied in the medical or pharmacological fields. This study was designed to investigate the effects of nanosilver on egg quality traits in laying Japanese quail in completely randomized design with four treatments and six repetitions at 0, 4, 8 and 12 ppm of silver nanoparticle levels. Eggs collected daily and egg parameters, including egg weight, length, width; yolk weight and eggshell thickness were examined. The effect of the different silver nanoparticle levels was determined using the General Linear Model of SAS procedure, whilst differences between the groups were determined using least significant difference test. Results indicated that silver nanoparticles at all levels caused significantly reduce of yolk weight and hen-day egg production for each week than the control treatment ( P < 0.05), whilst silver nanoparticle had no significant effect on egg weight, egg length and width and eggshell thickness.

Chronic effects of silver exposure on ion levels, survival, and silver distribution within developing rainbow trout (Oncorhynchus mykiss) embryos.

PubMed

Guadagnolo, C M; Brauner, C J; Wood, C M

2001-03-01

Rainbow trout embryos were chronically exposed to silver (as AgNO3) in moderately hard water (120 mg CaCO3/L, 0.70 mM Cl-, 1.3 mg/L dissolved organic matter. 12.3+/-0.1 degrees C) at nominal concentrations of 0.1, 1, and 10 microg/L (measured = 0.117+/-0.008, 1.22+/-0.16, and 13.51+/-1.58 microg/L, respectively) to investigate the effects on mortality, ionoregulation, and silver uptake and distribution of the embryo. Mortalities in the low concentrations (0.1 and 1.2 microg/L) were not significantly different from controls throughout embryonic development (days 1-32 postfertilization). Mortalities of embryos in the 13.5-microg/L treatment reached 56% by day 32 postfertilization (33% when accounting for control mortality), by which time more than 50% of surviving embryos had hatched. Accumulation of silver in whole embryos of 1.2- and 13.5-microg/L treatments reached the highest concentrations of 0.13 and 0.24 microg/g total silver, respectively, by day 32, but whole embryo silver burden was not correlated with mortality. Silver concentrations in different compartments of the whole embryo (chorion, dissected embryo, and yolk) were greatest just before hatch and were higher in the chorion for all experimental treatments. Up to 85% of total whole embryo silver content was bound to the chorion, which acts as a protective barrier during silver exposure. Whole embryo Na+ concentration in the 13.5-microg/L treatment was significantly reduced relative to controls from days 23 to 32 postfertilization, and levels in the embryo were reduced by 40% at day 32 postfertilization, indicating that silver toxicity in the whole embryo is associated with an ion regulatory disturbance that is similar to the acute effect of AgNO3 in juvenile and adult trout.

Silver ion doped ceramic nano-powder coated nails prevent infection in open fractures: In vivo study.

PubMed

Kose, Nusret; Çaylak, Remzi; Pekşen, Ceren; Kiremitçi, Abdurrahman; Burukoglu, Dilek; Koparal, Savaş; Doğan, Aydın

2016-02-01

Despite improvement in operative techniques and antibiotic therapy, septic complications still occur in open fractures. We developed silver ion containing ceramic nano powder for implant coating to provide not only biocompatibility but also antibacterial activity to the orthopaedic implants. We hypothesised silver ion doped calcium phosphate based ceramic nano-powder coated titanium nails may prevents bacterial colonisation and infection in open fractures as compared with uncoated nails. 33 rabbits divided into three groups. In the first group uncoated, in the second group hydroxyapatite coated, and in the third group silver doped hydroxyapatite coated titanium nails were inserted left femurs of animals from knee regions with retrograde fashion. Before implantation of nails 50 μl solution containing 10(6)CFU/ml methicillin resistance Staphylococcus aureus (MRSA) injected intramedullary canal. Rabbits were monitored for 10 weeks. Blood was taken from rabbits before surgery and on 2nd, 6th and 10th weeks. Blood was analysed for biochemical parameters, blood count, C-reactive protein and silver levels. At the end of the 10 weeks animals were sacrificed and rods were extracted in a sterile fashion. Swab cultures were taken from intramedullary canal. Bacteria on titanium rods were counted. Liver, heart, spleen, kidney and central nervous tissues samples were taken for determining silver levels. Histopathological evaluation of bone surrounding implants was also performed. No significant difference was detected between the groups from hematologic, biochemical, and toxicological aspect. Microbiological results showed that less bacterial growth was detected with the use of silver doped ceramic coated implants compared to the other two groups (p=0.003). Accumulation of silver was not detected. No cellular inflammation was observed around the silver coated prostheses. No toxic effect of silver on bone cells was seen. Silver ion doped calcium phosphate based ceramic nano powder coating to orthopaedic implants may prevents bacterial colonisation and infection in open fractures compared with those for implants without any coating. Copyright © 2015 Elsevier Ltd. All rights reserved.

The effects of bacteria-nanoparticles interface on the antibacterial activity of green synthesized silver nanoparticles.

PubMed

Ahmad, Aftab; Wei, Yun; Syed, Fatima; Tahir, Kamran; Rehman, Aziz Ur; Khan, Arifullah; Ullah, Sadeeq; Yuan, Qipeng

2017-01-01

Neutralization of bacterial cell surface potential using nanoscale materials is an effective strategy to alter membrane permeability, cytoplasmic leakage, and ultimate cell death. In the present study, an attempt was made to prepare biogenic silver nanoparticles using biomolecules from the aqueous rhizome extract of Coptis Chinensis. The biosynthesized silver nanoparticles were surface modified with chitosan biopolymer. The prepared silver nanoparticles and chitosan modified silver nanoparticles were cubic crystalline structures (XRD) with an average particle size of 15 and 20 nm respectively (TEM, DLS). The biosynthesized silver nanoparticles were surface stabilized by polyphenolic compounds (FTIR). Coptis Chinensis mediated silver nanoparticles displayed significant activity against E. coli and Bacillus subtilus with a zone of inhibition 12 ± 1.2 (MIC = 25 μg/mL) and 18 ± 1.6 mm (MIC = 12.50 μg/mL) respectively. The bactericidal efficacy of these nanoparticles was considerably increased upon surface modification with chitosan biopolymer. The chitosan modified biogenic silver nanoparticles exhibited promising activity against E. coli (MIC = 6.25 μg/mL) and Bacillus subtilus (MIC = 12.50 μg/mL). Our results indicated that the chitosan modified silver nanoparticles were promising agents in damaging bacterial membrane potential and induction of high level of intracellular reactive oxygen species (ROS). In addition, these nanoparticles were observed to induce the release of the high level of cytoplasmic materials especially protein and nucleic acids into the media. All these findings suggest that the chitosan functionalized silver nanoparticles are efficient agents in disrupting bacterial membrane and induction of ROS leading to cytoplasmic leakage and cell death. These findings further conclude that the bacterial-nanoparticles surface potential modulation is an effective strategy in enhancing the antibacterial potency of silver nanoparticles. Copyright © 2016 Elsevier Ltd. All rights reserved.

Occupational exposure limit for silver nanoparticles: considerations on the derivation of a general health-based value.

PubMed

Weldon, Brittany A; M Faustman, Elaine; Oberdörster, Günter; Workman, Tomomi; Griffith, William C; Kneuer, Carsten; Yu, Il Je

2016-09-01

With the increased production and widespread commercial use of silver nanoparticles (AgNPs), human and environmental exposures to silver nanoparticles are inevitably increasing. In particular, persons manufacturing and handling silver nanoparticles and silver nanoparticle containing products are at risk of exposure, potentially resulting in health hazards. While silver dusts, consisting of micro-sized particles and soluble compounds have established occupational exposure limits (OELs), silver nanoparticles exhibit different physicochemical properties from bulk materials. Therefore, we assessed silver nanoparticle exposure and related health hazards in order to determine whether an additional OEL may be needed. Dosimetric evaluations in our study identified the liver as the most sensitive target organ following inhalation exposure, and as such serves as the critical target organ for setting an occupational exposure standard for airborne silver nanoparticles. This study proposes an OEL of 0.19 μg/m(3) for silver nanoparticles derived from benchmark concentrations (BMCs) from subchronic rat inhalation toxicity assessments and the human equivalent concentration (HEC) with kinetic considerations and additional uncertainty factors. It is anticipated that this level will protect workers from potential health hazards, including lung, liver, and skin damage.

A Pharmacological and Toxicological Profile of Silver as an Antimicrobial Agent in Medical Devices

PubMed Central

Lansdown, Alan B. G.

2010-01-01

Silver is used widely in wound dressings and medical devices as a broad-spectrum antibiotic. Metallic silver and most inorganic silver compounds ionise in moisture, body fluids, and secretions to release biologically active Ag+. The ion is absorbed into the systemic circulation from the diet and drinking water, by inhalation and through intraparenteral administration. Percutaneous absorption of Ag+ through intact or damaged skin is low. Ag+ binds strongly to metallothionein, albumins, and macroglobulins and is metabolised to all tissues other than the brain and the central nervous system. Silver sulphide or silver selenide precipitates, bound lysosomally in soft tissues, are inert and not associated with an irreversible toxic change. Argyria and argyrosis are the principle effects associated with heavy deposition of insoluble silver precipitates in the dermis and cornea/conjunctiva. Whilst these changes may be profoundly disfiguring and persistent, they are not associated with pathological damage in any tissue. The present paper discusses the mechanisms of absorption and metabolism of silver in the human body, presumed mechanisms of argyria and argyrosis, and the elimination of silver-protein complexes in the bile and urine. Minimum blood silver levels consistent with early signs of argyria or argyrosis are not known. Silver allergy does occur but the extent of the problem is not known. Reference values for silver exposure are discussed. PMID:21188244

45 CFR 156.400 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., silver, gold, or platinum level of coverage is referred to as a standard bronze plan, a standard silver plan, a standard gold plan, and a standard platinum plan, respectively. Zero cost sharing plan...

Governing factors affecting the impacts of silver nanoparticles on wastewater treatment.

PubMed

Zhang, Chiqian; Hu, Zhiqiang; Li, Ping; Gajaraj, Shashikanth

2016-12-01

Silver nanoparticles (nanosilver or AgNPs) enter municipal wastewater from various sources, raising concerns about their potential adverse effects on wastewater treatment processes. We argue that the biological effects of silver nanoparticles at environmentally realistic concentrations (μgL -1 or lower) on the performance of a full-scale municipal water resource recovery facility (WRRF) are minimal. Reactor configuration is a critical factor that reduces or even mutes the toxicity of silver nanoparticles towards wastewater microbes in a full-scale WRRF. Municipal sewage collection networks transform silver nanoparticles into silver(I)-complexes/precipitates with low ecotoxicity, and preliminary/primary treatment processes in front of biological treatment utilities partially remove silver nanoparticles to sludge. Microbial functional redundancy and microbial adaptability to silver nanoparticles also greatly alleviate the adverse effects of silver nanoparticles on the performance of a full-scale WRRF. Silver nanoparticles in a lab-scale bioreactor without a sewage collection system and/or a preliminary/primary treatment process, in contrast to being in a full scale system, may deteriorate the reactor performance at relatively high concentrations (e.g., mgL -1 levels or higher). However, in many cases, silver nanoparticles have minimal impacts on lab-scale bioreactors, such as sequencing batch bioreactors (SBRs), especially when at relatively low concentrations (e.g., less than 1mgL -1 ). The susceptibility of wastewater microbes to silver nanoparticles is species-specific. In general, silver nanoparticles have higher toxicity towards nitrifying bacteria than heterotrophic bacteria. Copyright © 2016 Elsevier B.V. All rights reserved.

Topical colloidal silver as an anti-biofilm agent in a Staphylococcus aureus chronic rhinosinusitis sheep model.

PubMed

Rajiv, Sukanya; Drilling, Amanda; Bassiouni, Ahmed; James, Craig; Vreugde, Sarah; Wormald, Peter-John

2015-04-01

Treatment of recalcitrant chronic rhinosinusitis (CRS) is a challenge with increasing antibiotic resistance, leading to re-emergence of topical therapies. The aim of this study was to assess safety and efficacy of topical colloidal silver solution for the treatment of Staphylococcus aureus biofilms in a sheep model. In the safety study, normal saline (control) and 30-ppm colloidal silver solution (test) was used to flush the frontal sinuses for 14 days in 8 sheep (4 sheep each). In the efficacy study, following frontal sinus infection with Staphylococcus aureus, sheep were treated with either control saline or topical silver solution of varying concentrations (30 ppm/20 ppm/10 ppm/5 ppm) for 5 days, with 4 sheep in each group. Blood silver level, full blood counts, and biochemical parameters were analyzed in both safety and efficacy studies. Sinus tissue was harvested for histological examination and ciliary structure analysis in safety and for biofilm biomass quantification by fluorescence in situ hybridization (FISH) technique and COMSTAT 2 software in the efficacy study. Results were analyzed using appropriate statistical tests. Sheep treated with silver showed a significant decrease in biofilm biomass (0.004, 0.004, 0.004, and 0.007, in the 4 silver-treated groups, respectively) compared to saline control (0.175), p < 0.001. Although average blood silver levels were higher in the treated groups compared to controls (p < 0.05), blood counts and biochemical parameters were normal. Histology and ciliary structure analysis did not show any difference between control and treatment groups. Topical colloidal silver solution has effective antibiofilm activity in Staphylococcus aureus CRS in a sheep model and appears safe. © 2015 ARS-AAOA, LLC.

An examination of silver nanoparticles in socks using screening-level life cycle assessment

NASA Astrophysics Data System (ADS)

Meyer, David E.; Curran, Mary Ann; Gonzalez, Michael A.

2011-01-01

Screening-level life cycle assessment (LCA) can provide a quick tool to identify the life cycle hot spots and focus research efforts to help to minimize the burdens of a technology while maximizing its benefits. The use of nanoscale silver in consumer products has exploded in popularity. Although its use is considered beneficial because of antimicrobial effects, some attention must be given to the potential environmental impacts it could impart on the life cycle of these nanoproducts as production demands escalate. This work examines the environmental impact of including silver nanoparticles in commercially available socks using screening-level LCA. Initial results suggest washing during the use phase contributes substantially more than the manufacturing phase to the product life cycle impacts. Comparison of nanoparticles prepared by either chemical reduction, liquid flame spray (LFS), or plasma arc demonstrate how the type of manufacturing process used for the nanoscale silver can change the resulting life cycle impact of the sock product. The magnitude of this impact will depend on the type of process used to manufacture the nanoscale silver, with LFS having the most impact because of the need for large quantities of hydrogen and oxygen. Although the increased impacts for a single nanoproduct may be relatively small, the added environmental load can actually be a significant quantity when considered at the regional or global production level.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soelberg, Nicholas Ray; Watson, Tony Leroy

Deep-bed methyl iodide adsorption testing has continued in Fiscal Year 2016 under the Department of Energy (DOE) Fuel Cycle Technology (FCT) Program Offgas Sigma Team to further research and advance the technical maturity of solid sorbents for capturing iodine-129 in off-gas streams during used nuclear fuel reprocessing. Adsorption testing with higher levels of NO (approximately 3,300 ppm) and NO2 (up to about 10,000 ppm) indicate that high efficiency iodine capture by silver aerogel remains possible. Maximum iodine decontamination factors (DFs, or the ratio of iodine flowrate in the sorbent bed inlet gas compared to the iodine flowrate in the outletmore » gas) exceeded 3,000 until bed breakthrough rapidly decreased the DF levels to as low as about 2, when the adsorption capability was near depletion. After breakthrough, nearly all of the uncaptured iodine that remains in the bed outlet gas stream is no longer in the form of the original methyl iodide. The methyl iodide molecules are cleaved in the sorbent bed, even after iodine adsorption is no longer efficient, so that uncaptured iodine is in the form of iodine species soluble in caustic scrubber solutions, and detected and reported here as diatomic I2. The mass transfer zone depths were estimated at 8 inches, somewhat deeper than the 2-5 inch range estimated for both silver aerogels and silver zeolites in prior deep-bed tests, which had lower NOx levels. The maximum iodine adsorption capacity and silver utilization for these higher NOx tests, at about 5-15% of the original sorbent mass, and about 12-35% of the total silver, respectively, were lower than for trends from prior silver aerogel and silver zeolite tests with lower NOx levels. Additional deep-bed testing and analyses are recommended to expand the database for organic iodide adsorption and increase the technical maturity if iodine adsorption processes.« less

Timescale of silver nanoparticle transformation in neural cell cultures impacts measured cell response

NASA Astrophysics Data System (ADS)

Hume, Stephanie L.; Chiaramonti, Ann N.; Rice, Katherine P.; Schwindt, Rani K.; MacCuspie, Robert I.; Jeerage, Kavita M.

2015-07-01

Both serum protein concentration and ionic strength are important factors in nanoparticle transformation within cell culture environments. However, silver nanoparticles are not routinely tracked at their working concentration in the specific medium used for in vitro toxicology studies. Here we evaluated the transformation of electrostatically stabilized citrate nanoparticles (C-AgNPs) and sterically stabilized polyvinylpyrrolidone nanoparticles (PVP-AgNPs) in a low-serum ( 0.2 mg/mL bovine serum albumin) culture medium, while measuring the response of rat cortex neural progenitor cells, which differentiate in this culture environment. After 24 h, silver nanoparticles at concentrations up to 10 µg/mL did not affect adenosine triphosphate levels, whereas silver ions decreased adenosine triphosphate levels at concentrations of 1.1 µg/mL or higher. After 240 h, both silver nanoparticles, as well as silver ion, unambiguously decreased adenosine triphosphate levels at concentrations of 1 and 1.1 µg/mL, respectively, suggesting particle dissolution. Particle transformation was investigated in 1:10 diluted, 1:2 diluted, or undiluted differentiation medium, all having an identical protein concentration, to separate the effect of serum protein stabilization from ionic strength destabilization. Transmission electron microscopy images indicated that particles in 1:10 medium were not surrounded by proteins, whereas particles became clustered within a non-crystalline protein matrix after 24 h in 1:2 medium and at 0 h in undiluted medium. Despite evidence for a protein corona, particles were rapidly destabilized by high ionic strength media. Polyvinylpyrrolidone increased the stability of singly dispersed particles compared to citrate ligands; however, differences were negligible after 4 h in 1:2 medium or after 1 h in undiluted medium. Thus low-serum culture environments do not provide sufficient colloidal stability for long-term toxicology studies with citrate- or polyvinylpyrrolidone-stabilized silver nanoparticles.

Silver(I) complexes of 2,4-dihydroxybenzaldehyde-amino acid Schiff bases-Novel noncompetitive α-glucosidase inhibitors.

PubMed

Zheng, Jingwei; Ma, Lin

2015-01-01

A series of silver(I) complexes of 2,4-dihydroxybenzaldehyde-amino acid Schiff bases were designed and tested for α-glucosidase inhibition. Our results indicate that all the silver complexes (4a-18a) possessed strong inhibitory activity at μmolL(-1) level, especially glutamine (12a) and histidine (18a) Schiff base silver(I) complexes exhibited an IC50 value of less than 0.01μmolL(-1). This series of compounds exhibited noncompetitive inhibition characteristics in kinetic studies. In addition, we investigated the mechanism of inhibition and the structure-activity relationships of the amino acid Schiff base silver complexes. Our results reveal that Schiff base silver complexes may be explored for their therapeutic potential as alternatives of α-glucosidase inhibitors. Copyright © 2015 Elsevier Ltd. All rights reserved.

In Situ Probing of Cholesterol in Astrocytes at the Single Cell Level using Laser Desorption Ionization Mass Spectrometric Imaging with Colloidal Silver

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perdian, D.C.; Cha, Sangwon; Oh, Jisun

2010-03-18

Mass spectrometric imaging has been utilized to localize individual astrocytes and to obtain cholesterol populations at the single-cell level in laser desorption ionization (LDI) with colloidal silver. The silver ion adduct of membrane-bound cholesterol was monitored to detect individual cells. Good correlation between mass spectrometric and optical images at different cell densities indicates the ability to perform single-cell studies of cholesterol abundance. The feasibility of quantification is confirmed by the agreement between the LDI-MS ion signals and the results from a traditional enzymatic fluorometric assay. We propose that this approach could be an effective tool to study chemical populations atmore » the cellular level.« less

Characterisation and potential migration of silver nanoparticles from commercially available polymeric food contact materials.

PubMed

Addo Ntim, Susana; Thomas, Treye A; Begley, Timothy H; Noonan, Gregory O

2015-01-01

The potential for consumer exposure to nano-components in food contact materials (FCMs) is dependent on the migration of nanomaterials into food. Therefore, characterising the physico-chemical properties and potential for migration of constituents is an important step in assessing the safety of FCMs. A number of commercially available food storage products, purchased domestically within the United States and internationally, that claim to contain nanosilver were evaluated. The products were made of polyethylene, polypropylene and polyphenylene ether sulfone and all contained silver (0.001-36 mg kg(-1) of polymer). Silver migration was measured under various conditions, including using 3% acetic acid and water as food simulants. Low concentrations (sub-ppb levels) of silver were detected in the migration studies generally following a trend characterised by a surface desorption phenomenon, where the majority of the silver migration occurred in the first of three consecutive exposures. Silver nanoparticles were not detected in food simulants, suggesting that the silver migration may be due solely to ionic silver released into solution from oxidation of the silver nanoparticle surface. The absence of detectable silver nanoparticles was consistent with expectations from a physico-chemical view point. For the products tested, current USFDA guidance for evaluating migration from FCMs was applicable.

Disinfection of human enteric viruses in water by copper and silver in combination with low levels of chlorine.

PubMed Central

Abad, F X; Pintó, R M; Diez, J M; Bosch, A

1994-01-01

The efficacy of copper and silver ions, in combination with low levels of free chlorine (FC), was evaluated for the disinfection of hepatitis A virus (HAV), human rotavirus (HRV), human adenovirus, and poliovirus (PV) in water. HAV and HRV showed little inactivation in all conditions. PV showed more than a 4 log10 titer reduction in the presence of copper and silver combined with 0.5 mg of FC per liter or in the presence of 1 mg of FC per liter alone. Human adenovirus persisted longer than PV with the same treatments, although it persisted significantly less than HRV or HAV. The addition of 700 micrograms of copper and 70 micrograms of silver per liter did not enhance the inactivation rates after the exposure to 0.5 or 0.2 mg of FC per liter, although on some occasions it produced a level of inactivation similar to that induced by a higher dose of FC alone. Virus aggregates were observed in the presence of copper and silver ions, although not in the presence of FC alone. Our data indicate that the use of copper and silver ions in water systems may not provide a reliable alternative to high levels of FC for the disinfection of viral pathogens. Gene probe-based procedures were not adequate to monitor the presence of infectious HAV after disinfection. PV does not appear to be an adequate model viral strain to be used in disinfection studies. Bacteroides fragilis bacteriophages were consistently more resistant to disinfection than PV, suggesting that they would be more suitable indicators, although they survived significantly less than HAV or HRV. Images PMID:8074518

Lake level variability in Silver Lake, Michigan: a response to fluctuations in lake levels of Lake Michigan

USGS Publications Warehouse

Fisher, Timothy G.; Loope, Walter L.

2004-01-01

Sediment from Silver Lake, Michigan, can be used to constrain the timing and elevation of Lake Michigan during the Nipissing transgression. Silver Lake is separated from Lake Michigan by a barrier/dune complex and the Nipissing, Calumet, and Glenwood shorelines of Lake Michigan are expressed landward of this barrier. Two Vibracores were taken from the lake in February 2000 and contain pebbly sand, sand, buried soils, marl, peat, and sandy muck. It is suggested here that fluctuations in the level of Lake Michigan are reflected in Silver Lake since the Chippewa low phase, and possibly at the end of the Algonquin phase. An age of 12,490 B.P. (10,460±50 14C yrs B.P.) on wood from a buried Entisol may record the falling Algonquin phase as the North Bay outlet opened. A local perched water table is indicated by marl deposited before 7,800 B.P. and peat between 7,760-7,000 B.P. when Lake Michigan was at the low elevation Chippewa phase. Continued deepening of the lake is recorded by the transition from peat to sandy muck at 7,000 B.P. in the deeper core, and with the drowning of an Inceptisol nearly 3 m higher at 6,410 B.P. in the shallower core. A rising groundwater table responding to a rising Lake Michigan base level during the Nipissing transgression, rather than a response to mid-Holocene climate change, explains deepening of Silver Lake. Sandy muck was deposited continually in Silver Lake between Nipissing and modern time. Sand lenses within the muck are presumed to be eolian in origin, derived from sand dunes advancing into the lake on the western side of the basin.

A DFT study on photoinduced surface catalytic coupling reactions on nanostructured silver: selective formation of azobenzene derivatives from para-substituted nitrobenzene and aniline.

PubMed

Zhao, Liu-Bin; Huang, Yi-Fan; Liu, Xiu-Min; Anema, Jason R; Wu, De-Yin; Ren, Bin; Tian, Zhong-Qun

2012-10-05

We propose that aromatic nitro and amine compounds undergo photochemical reductive and oxidative coupling, respectively, to specifically produce azobenzene derivatives which exhibit characteristic Raman signals related to the azo group. A photoinduced charge transfer model is presented to explain the transformations observed in para-substituted ArNO(2) and ArNH(2) on nanostructured silver due to the surface plasmon resonance effect. Theoretical calculations show that the initial reaction takes place through excitation of an electron from the filled level of silver to the lowest unoccupied molecular orbital (LUMO) of an adsorbed ArNO(2) molecule, and from the highest occupied molecular orbital (HOMO) of an adsorbed ArNH(2) molecule to the unoccupied level of silver, during irradiation with visible light. The para-substituted ArNO(2)(-)˙ and ArNH(2)(+)˙ surface species react further to produce the azobenzene derivatives. Our results may provide a new strategy for the syntheses of aromatic azo dyes from aromatic nitro and amine compounds based on the use of nanostructured silver as a catalyst.

Micro-Raman Spectroscopy of Silver Nanoparticle Induced Stress on Optically-Trapped Stem Cells

PubMed Central

Bankapur, Aseefhali; Krishnamurthy, R. Sagar; Zachariah, Elsa; Santhosh, Chidangil; Chougule, Basavaraj; Praveen, Bhavishna; Valiathan, Manna; Mathur, Deepak

2012-01-01

We report here results of a single-cell Raman spectroscopy study of stress effects induced by silver nanoparticles in human mesenchymal stem cells (hMSCs). A high-sensitivity, high-resolution Raman Tweezers set-up has been used to monitor nanoparticle-induced biochemical changes in optically-trapped single cells. Our micro-Raman spectroscopic study reveals that hMSCs treated with silver nanoparticles undergo oxidative stress at doping levels in excess of 2 µg/ml, with results of a statistical analysis of Raman spectra suggesting that the induced stress becomes more dominant at nanoparticle concentration levels above 3 µg/ml. PMID:22514708

Largely Enhanced Single-molecule Fluorescence in Plasmonic Nanogaps formed by Hybrid Silver Nanostructures

PubMed Central

Zhang, Jian; Lakowicz, Joseph R.

2013-01-01

It has been suggested that narrow gaps between metallic nanostructures can be practical for producing large field enhancement. We design a hybrid silver nanostructure geometry in which fluorescent emitters are sandwiched between silver nanoparticles and silver island film (SIF). A desired number of polyelectrolyte layers are deposited on the SIF surface before the self-assembly of a second silver nanoparticle layer. Layer-by-layer configuration provides a well-defined dye position. It allows us to study the photophyical behaviors of fluorophores in the resulting gap at the single molecule level. The enhancement factor of a fluorophore located in the gap is much higher than those on silver surfaces alone and on glass. These effects may be used for increased detectability of single molecules bound to surfaces which contain metallic structures for either biophysical studies or high sensitivity assays. PMID:23373787

Visual Identification of Light-Driven Breakage of the Silver-Dithiocarbamate Bond by Single Plasmonic Nanoprobes

PubMed Central

Gao, Peng Fei; Yuan, Bin Fang; Gao, Ming Xuan; Li, Rong Sheng; Ma, Jun; Zou, Hong Yan; Li, Yuan Fang; Li, Ming; Huang, Cheng Zhi

2015-01-01

Insight into the nature of metal-sulfur bond, a meaningful one in life science, interface chemistry and organometallic chemistry, is interesting but challenging. By utilizing the localized surface plasmon resonance properties of silver nanoparticles, herein we visually identified the photosensitivity of silver-dithiocarbamate (Ag-DTC) bond by using dark field microscopic imaging (iDFM) technique at single nanoparticle level. It was found that the breakage of Ag-DTC bond could be accelerated effectively by light irradiation, followed by a pH-dependent horizontal or vertical degradation of the DTC molecules, in which an indispensable preoxidation process of the silver was at first disclosed. These findings suggest a visualization strategy at single plasmonic nanoparticle level which can be excellently applied to explore new stimulus-triggered reactions, and might also open a new way to understand traditional organic reaction mechanisms. PMID:26493773

Physiological response of juvenile rainbow trout to chronic low level exposures of waterborne silver.

PubMed

Galvez, F; Hogstrand, C; Wood, C M

1998-02-01

The physiological effects of chronic exposure to AgNO3 in moderately hard freshwater were investigated in juvenile rainbow trout (Oncorhynchus mykiss Walbaum). Two separate 28-day exposures were performed at silver concentrations of 0.5 and 2.0 micrograms/L in flowing Hamilton dechlorinated tap water. Exposure to 0.5 microgram/L Ag resulted in a slight increase (approximately 14.9%) in food consumption, whereas growth rates remained unaltered. Both plasma Na+ and Cl- levels were significantly decreased by 11.8% and 9.3%, respectively at day 16 of the exposure. Hepatic Ag concentrations were elevated approximately 4-fold in 0.5 microgram/L Ag-exposed fish. However, no significant increases in liver metallothionein (MT) concentrations were noted. No mortalities were observed during this 28-day exposure. In comparison, chronic exposure to 2.0 micrograms/L Ag resulted in a 28.8% decrease in food consumption and a 43.0% reduction in growth rate. Plasma [Na+] was decreased by 18.3%, whereas plasma [Cl-] was reduced by 12.2% at day 7. At both concentrations of silver, plasma ion concentrations appeared to recover thereafter. Silver accumulated steadily in the liver up until day 15 when concentrations were 39.7 micrograms/g wet weight (285-fold increase) above control levels. In addition, MT levels were increased by 81.2% at day 7. Silver exposure at 2.0 micrograms/L resulted in approximately 15.0% mortality over the 28-day period.

In situ probing of cholesterol in astrocytes at the single-cell level using laser desorption ionization mass spectrometric imaging with colloidal silver.

PubMed

Perdian, D C; Cha, Sangwon; Oh, Jisun; Sakaguchi, Donald S; Yeung, Edward S; Lee, Young Jin

2010-04-30

Mass spectrometric imaging has been utilized to localize individual astrocytes and to obtain cholesterol populations at the single-cell level in laser desorption ionization (LDI) with colloidal silver. The silver ion adduct of membrane-bound cholesterol was monitored to detect individual cells. Good correlation between mass spectrometric and optical images at different cell densities indicates the ability to perform single-cell studies of cholesterol abundance. The feasibility of quantification is confirmed by the agreement between the LDI-MS ion signals and the results from a traditional enzymatic fluorometric assay. We propose that this approach could be an effective tool to study chemical populations at the cellular level. Published in 2010 by John Wiley & Sons, Ltd.

Effects of water hardness on size and hatching success of silver carp eggs

USGS Publications Warehouse

Rach, Jeff J.; Sass, Greg G.; Luoma, James A.; Gaikowski, Mark P.

2010-01-01

Eggs of silver carp Hypophthalmichthys molitrix absorb water after release from the female, causing them to become turgid and to increase substantially in size. The volume of water that diffuses within an egg is most likely determined by (1) the difference in ionic concentration between the egg and the water that surrounds it and (2) the elasticity of the egg membrane. Prior observations suggest that silver carp eggs may swell and burst in soft waters. If water hardness affects silver carp reproductive success in nonnative ecosystems, this abiotic factor could limit silver carp distribution or abundance. In this study, we tested the effect of water hardness on silver carp egg enlargement and hatching success. Groups of newly fertilized silver carp eggs were placed in water at one of five nominal water hardness levels (50, 100, 150, 200, or 250 mg/L as CaCO3) for 1 h to harden (absorb water after fertilization). Egg groups were then placed in separate incubation vessels housed in two recirculation systems that were supplied with either soft (50 mg/L as CaCO3) or hard (250 mg/L as CaCO3) water to evaluate hatching success. Tests were terminated within 24 h after viable eggs had hatched. Eggs that were initially placed in 50-mg/L water to harden were larger (i.e., swelled more) and had a greater probability of hatch than eggs hardened in other water hardness levels. Unlike the effect of water hardness during egg hardening, the water hardness during incubation appeared to have no effect on egg hatching success. Our research suggests that water hardness may not be a limiting factor in the reproduction, recruitment, and range expansion of silver carp in North America.

Spatial and temporal variations in silver contamination and toxicity in San Francisco Bay

USGS Publications Warehouse

Flegal, A.R.; Brown, C.L.; Squire, S.; Ross, J.R.M.; Scelfo, G.M.; Hibdon, S.

2007-01-01

Although San Francisco Bay has a "Golden Gate", it may be argued that it is the "Silver Estuary". For at one time the Bay was reported to have the highest levels of silver in its sediments and biota, along with the only accurately measured values of silver in solution, of any estuarine system. Since then others have argued that silver contamination is higher elsewhere (e.g., New York Bight, Florida Bay, Galveston Bay) in a peculiar form of pollution machismo, while silver contamination has measurably declined in sediments, biota, and surface waters of the Bay over the past two to three decades. Documentation of those systemic temporal declines has been possible because of long-term, ongoing monitoring programs, using rigorous trace metal clean sampling and analytical techniques, of the United States Geological Survey and San Francisco Bay Regional Monitoring Program that are summarized in this report. However, recent toxicity studies with macro-invertebrates in the Bay have indicated that silver may still be adversely affecting the health of the estuarine system, and other studies have indicated that silver concentrations in the Bay may be increasing due to new industrial inputs and/or the diagenetic remobilization of silver from historically contaminated sediments being re-exposed to overlying surface waters and benthos. Consequently, the Bay may not be ready to relinquish its title as the "Silver Estuary". ?? 2007 Elsevier Inc. All rights reserved.

Electrochemical Detection of Ultratrace (Picomolar) Levels of Hg2+ Using a Silver Nanoparticle-Modified Glassy Carbon Electrode.

PubMed

Suherman, Alex L; Ngamchuea, Kamonwad; Tanner, Eden E L; Sokolov, Stanislav V; Holter, Jennifer; Young, Neil P; Compton, Richard G

2017-07-05

Ultratrace levels of Hg 2+ have been quantified by undertaking linear sweep voltammetry with a silver nanoparticle-modified glassy carbon electrode (AgNP-GCE) in aqueous solutions containing Hg 2+ . This is achieved by monitoring the change in the silver stripping peak with Hg 2+ concentration resulting from the galvanic displacement of silver by mercury: Ag(np) + 1/2Hg 2+ (aq) → Ag + (aq) + 1/2Hg(l). This facile and reproducible detection method exhibits an excellent linear dynamic range of 100.0 pM to 10.0 nM Hg 2+ concentration with R 2 = 0.982. The limit of detection (LoD) based on 3σ is 28 pM Hg 2+ , while the lowest detectable level for quantification purposes is 100.0 pM. This method is appropriate for routine environmental monitoring and drinking water quality assessment since the guideline value set by the US Environmental Protection Agency (EPA) for inorganic mercury in drinking water is 0.002 mg L -1 (10 nM).

A humidity sensing organic-inorganic composite for environmental monitoring.

PubMed

Ahmad, Zubair; Zafar, Qayyum; Sulaiman, Khaulah; Akram, Rizwan; Karimov, Khasan S

2013-03-14

In this paper, we present the effect of varying humidity levels on the electrical parameters and the multi frequency response of the electrical parameters of an organic-inorganic composite (PEPC+NiPc+Cu2O)-based humidity sensor. Silver thin films (thickness ~200 nm) were primarily deposited on plasma cleaned glass substrates by the physical vapor deposition (PVD) technique. A pair of rectangular silver electrodes was formed by patterning silver film through standard optical lithography technique. An active layer of organic-inorganic composite for humidity sensing was later spun coated to cover the separation between the silver electrodes. The electrical characterization of the sensor was performed as a function of relative humidity levels and frequency of the AC input signal. The sensor showed reversible changes in its capacitance with variations in humidity level. The maximum sensitivity ~31.6 pF/%RH at 100 Hz in capacitive mode of operation has been attained. The aim of this study was to increase the sensitivity of the previously reported humidity sensors using PEPC and NiPc, which has been successfully achieved.

A Humidity Sensing Organic-Inorganic Composite for Environmental Monitoring

PubMed Central

Ahmad, Zubair; Zafar, Qayyum; Sulaiman, Khaulah; Akram, Rizwan; Karimov, Khasan S.

2013-01-01

In this paper, we present the effect of varying humidity levels on the electrical parameters and the multi frequency response of the electrical parameters of an organic-inorganic composite (PEPC+NiPc+Cu2O)-based humidity sensor. Silver thin films (thickness ∼200 nm) were primarily deposited on plasma cleaned glass substrates by the physical vapor deposition (PVD) technique. A pair of rectangular silver electrodes was formed by patterning silver film through standard optical lithography technique. An active layer of organic-inorganic composite for humidity sensing was later spun coated to cover the separation between the silver electrodes. The electrical characterization of the sensor was performed as a function of relative humidity levels and frequency of the AC input signal. The sensor showed reversible changes in its capacitance with variations in humidity level. The maximum sensitivity ∼31.6 pF/%RH at 100 Hz in capacitive mode of operation has been attained. The aim of this study was to increase the sensitivity of the previously reported humidity sensors using PEPC and NiPc, which has been successfully achieved. PMID:23493124

Biomedical potential of silver nanoparticles synthesized from calli cells of Citrullus colocynthis (L.) Schrad.

PubMed

Satyavani, K; Gurudeeban, S; Ramanathan, T; Balasubramanian, T

2011-09-26

An increasingly common application is the use of silver nanoparticles for antimicrobial coatings, wound dressings, and biomedical devices. In this present investigation, we report, biomedical potential of silver nanopaticles synthesized from calli extract of Citrullus colocynthis on Human epidermoid larynx carcinoma (HEp -2) cell line. The callus extract react with silver nitrate solution confirmed silver nanoparticles synthesis through the steady change of greenish colour to reddish brown and characterized by using FT-IR, AFM. Toxicity on HEp 2 cell line assessed using MTT assay, caspase -3 assay, Lactate dehydrogenase leakage assay and DNA fragmentation assay. The synthesized silver nanoparticles were generally found to be spherical in shape with size 31 nm by AFM. The molar concentration of the silver nanoparticles solution in our present study is 1100 nM/10 mL. The results exhibit that silver nanoparticles mediate a dose-dependent toxicity for the cell tested, and the silver nanoparticles at 500 nM decreased the viability of HEp 2 cells to 50% of the initial level. LDH activities found to be significantly elevated after 48 h of exposure in the medium containing silver nanoparticles when compared to the control and Caspase 3 activation suggested that silver nanoparticles caused cell death through apoptosis, which was further supported by cellular DNA fragmentation, showed that the silver nanoparticles treated HEp2 cells exhibited extensive double strand breaks, thereby yielding a ladder appearance (Lane 2), while the DNA of control HEp2 cells supplemented with 10% serum exhibited minimum breakage (Lane 1). This study revealed completely would eliminate the use of expensive drug for cancer treatment.

Evaluation of a Silver-Embedded Ceramic Tablet as a Primary and Secondary Point-of-Use Water Purification Technology in Limpopo Province, S. Africa

PubMed Central

Ehdaie, Beeta; Rento, Chloe T.; Son, Veronica; Turner, Sydney S.; Samie, Amidou; Dillingham, Rebecca A.

2017-01-01

The World Health Organization (WHO) recognizes point-of-use water treatment (PoUWT) technologies as effective means to improve water quality. This paper investigates long-term performance and social acceptance of a novel PoUWT technology, a silver-infused ceramic tablet, in Limpopo Province, South Africa. When placed in a water storage container, the silver-embedded ceramic tablet releases silver ions into water, thereby disinfecting microbial pathogens and leaving the water safe for human consumption. As a result of its simplicity and efficiency, the silver-embedded ceramic tablet can serve as a stand-alone PoUWT method and as a secondary PoUWT to improve exisitng PoUWT methods, such as ceramic water filters. In this paper, three PoUWT interventions were conducted to evaluate the silver-embedded ceramic tablet: (1) the silver-embedded ceramic tablet as a stand-alone PoUWT method, (2) ceramic water filters stand-alone, and (3) a filter-tablet combination. The filter-tablet combination evaluates the silver-embedded ceramic tablet as a secondary PoUWT method when placed in the lower reservoir of the ceramic water filter system to provide residual disinfection post-filtration. Samples were collected from 79 households over one year and analyzed for turbidity, total silver levels and coliform bacteria. Results show that the silver-embedded ceramic tablet effectively reduced total coliform bacteria (TC) and E. coli when used as a stand-alone PoUWT method and when used in combination with ceramic water filters. The silver-embedded ceramic tablet’s performance as a stand-alone PoUWT method was comparable to current inexpensive, single-use PoUWT methods, demonstrating 100% and 75% median reduction in E. coli and TC, respectively, after two months of use. Overall, the the filter-tablet combination performed the best of the three interventions, providing a 100% average percent reduction in E. coli over one year. User surveys were also conducted and indicated that the silver-embedded ceramic tablet was simple to use and culturally appropriate. Also, silver levels in all treated water samples remained below 20 μg/L, significantly lower than the drinking water standard of 100 μg/L, making it safe for consumption. Long-term data demonstrates that the silver-embedded ceramic tablet has beneficial effects even after one year of use. This study demonstrates that the silver-embedded ceramic tablet can effectively improve water quality when used alone, or with ceramic water filters, to reduce rates of recontamination. Therefore, the tablet has the potential to provide a low-cost means to purify water in resource-limited settings. PMID:28095435

Evaluation of a Silver-Embedded Ceramic Tablet as a Primary and Secondary Point-of-Use Water Purification Technology in Limpopo Province, S. Africa.

PubMed

Ehdaie, Beeta; Rento, Chloe T; Son, Veronica; Turner, Sydney S; Samie, Amidou; Dillingham, Rebecca A; Smith, James A

2017-01-01

The World Health Organization (WHO) recognizes point-of-use water treatment (PoUWT) technologies as effective means to improve water quality. This paper investigates long-term performance and social acceptance of a novel PoUWT technology, a silver-infused ceramic tablet, in Limpopo Province, South Africa. When placed in a water storage container, the silver-embedded ceramic tablet releases silver ions into water, thereby disinfecting microbial pathogens and leaving the water safe for human consumption. As a result of its simplicity and efficiency, the silver-embedded ceramic tablet can serve as a stand-alone PoUWT method and as a secondary PoUWT to improve exisitng PoUWT methods, such as ceramic water filters. In this paper, three PoUWT interventions were conducted to evaluate the silver-embedded ceramic tablet: (1) the silver-embedded ceramic tablet as a stand-alone PoUWT method, (2) ceramic water filters stand-alone, and (3) a filter-tablet combination. The filter-tablet combination evaluates the silver-embedded ceramic tablet as a secondary PoUWT method when placed in the lower reservoir of the ceramic water filter system to provide residual disinfection post-filtration. Samples were collected from 79 households over one year and analyzed for turbidity, total silver levels and coliform bacteria. Results show that the silver-embedded ceramic tablet effectively reduced total coliform bacteria (TC) and E. coli when used as a stand-alone PoUWT method and when used in combination with ceramic water filters. The silver-embedded ceramic tablet's performance as a stand-alone PoUWT method was comparable to current inexpensive, single-use PoUWT methods, demonstrating 100% and 75% median reduction in E. coli and TC, respectively, after two months of use. Overall, the the filter-tablet combination performed the best of the three interventions, providing a 100% average percent reduction in E. coli over one year. User surveys were also conducted and indicated that the silver-embedded ceramic tablet was simple to use and culturally appropriate. Also, silver levels in all treated water samples remained below 20 μg/L, significantly lower than the drinking water standard of 100 μg/L, making it safe for consumption. Long-term data demonstrates that the silver-embedded ceramic tablet has beneficial effects even after one year of use. This study demonstrates that the silver-embedded ceramic tablet can effectively improve water quality when used alone, or with ceramic water filters, to reduce rates of recontamination. Therefore, the tablet has the potential to provide a low-cost means to purify water in resource-limited settings.

Assessment of Silver Based Disinfection Technology for CEV and Future US Spacecraft

NASA Technical Reports Server (NTRS)

Callahan, Michael R.; Adam, Niklas M.; Roberts, Michael S.; Garland, Jay L.; Sager, John C.; Pickering, Karen D.

2007-01-01

Silver biocide offers a potential advantage over iodine, the current state-of-the-art in US spacecraft disinfection technology, in that silver can be safely consumed by the crew. As such, silver may reduce the overall complexity and mass of future spacecraft potable water systems, particularly those used to support long duration missions. A primary technology gap identified for the use of silver biocide is one of material compatibility. Wetted materials of construction are required to be selected such that silver ion concentrations can be maintained at biocidally effective levels. Preliminary data on silver biocide depletion rates in heritage spacecraft potable water system wetted-materials of construction has been gathered as part of a multi-phase test project aimed at the characterization of silver based biocide technology through: development of preferred materials lists, investigation of silver biocide forms and delivery methods, down-selection of silver biocide technologies, and integrated testing. A 10% - 20% loss in silver ion concentration per day was observed for acid passivated Nitronic 40 tubing with surface area to volume (S/V) ratios of approximately 4.59 cm-1. The Nitronic 40 tubes were tested both with and without biocide pretreatment. Silver biocide depletion was also observed at approximately 0.1% per day for the first 35 days of exposure to acid passivated Inconel 718 coupon, S/V of approximately 0.14 cm-1. Surface analysis by scanning election microscopy (SEM) suggested deposition of silver metal on both test materials. SEM analysis also provided evidence of potential variability in the passivation process for tube configuration of the Nitronic 40 test apparatus. These preliminary results are presented and discussed herein, along with the current project status.

Class II glass ionomer/silver cermet restorations and their effect on interproximal growth of mutans streptococci.

PubMed

Berg, J H; Farrell, J E; Brown, L R

1990-02-01

The release of fluoride from glass ionomer materials is one of the most important features of this newly implemented material, and the remineralization effects of this phenomenon have been documented (Hicks and Silverstone 1986). This paper examines the effects of glass ionomer/silver cermet restorations on the plaque levels of interproximal mutans streptococci. Fifteen patients with Class II lesions in primary molars were selected for study. Interproximal plaque samples were obtained from each of the lesion sites and from one caries-free site approximal to a primary molar. One lesion was restored with composite resin to serve as a treated control to the glass ionomer/silver cermet (Ketac Silver, ESPE/Premier Sales Corp., Norristown, Pennsylvania) test site. A sound (unaltered) interproximal site served as the untreated control site. Plaque samples were collected before and at one week, one month, and three months post-treatment. Samples were serially diluted to enable colony counts of mutans streptococci. One week post-treatment counts showed that the glass ionomer/silver cermet restorations significantly reduced (P less than 0.05) the approximal plaque levels of mutans streptococci. Conversely, the untreated and treated control sites did not exhibit reductions in approximal plaque levels of mutans streptococci. These results indicate that glass ionomer restorations may be inhibitory to the growth of mutans streptococci in dental plaque approximal to this restorative material in the primary dentition.

Tin-silver-bismuth solders for electronics assembly

DOEpatents

Vianco, Paul T.; Rejent, Jerome A.

1995-01-01

A lead-free solder alloy for electronic assemblies composed of a eutectic alloy of tin and silver with a bismuth addition, x, of 0

Tin-silver-bismuth solders for electronics assembly

DOEpatents

Vianco, P.T.; Rejent, J.A.

1995-08-08

A lead-free solder alloy is disclosed for electronic assemblies composed of a eutectic alloy of tin and silver with a bismuth addition, x, of 0

Silver ions increase plasma membrane permeability through modulation of intracellular calcium levels in tobacco BY-2 cells.

PubMed

Klíma, Petr; Laňková, Martina; Vandenbussche, Filip; Van Der Straeten, Dominique; Petrášek, Jan

2018-05-01

Silver ions increase plasma membrane permeability for water and small organic compounds through their stimulatory effect on plasma membrane calcium channels, with subsequent modulation of intracellular calcium levels and ion homeostasis. The action of silver ions at the plant plasma membrane is largely connected with the inhibition of ethylene signalling thanks to the ability of silver ion to replace the copper cofactor in the ethylene receptor. A link coupling the action of silver ions and cellular auxin efflux has been suggested earlier by their possible direct interaction with auxin efflux carriers or by influencing plasma membrane permeability. Using tobacco BY-2 cells, we demonstrate here that besides a dramatic increase of efflux of synthetic auxins 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-naphthalene acetic acid (NAA), treatment with AgNO 3 resulted in enhanced efflux of the cytokinin trans-zeatin (tZ) as well as the auxin structural analogues tryptophan (Trp) and benzoic acid (BA). The application of AgNO 3 was accompanied by gradual water loss and plasmolysis. The observed effects were dependent on the availability of extracellular calcium ions (Ca 2+ ) as shown by comparison of transport assays in Ca 2+ -rich and Ca 2+ -free buffers and upon treatment with inhibitors of plasma membrane Ca 2+ -permeable channels Al 3+ and ruthenium red, both abolishing the effect of AgNO 3 . Confocal microscopy of Ca 2+ -sensitive fluorescence indicator Fluo-4FF, acetoxymethyl (AM) ester suggested that the extracellular Ca 2+ availability is necessary to trigger the response to silver ions and that the intracellular Ca 2+ pool alone is not sufficient for this effect. Altogether, our data suggest that in plant cells the effects of silver ions originate from the primal modification of the internal calcium levels, possibly by their interaction with Ca 2+ -permeable channels at the plasma membrane.

Food safety concerns deriving from the use of silver based food packaging materials.

PubMed

Pezzuto, Alessandra; Losasso, Carmen; Mancin, Marzia; Gallocchio, Federica; Piovesana, Alessia; Binato, Giovanni; Gallina, Albino; Marangon, Alberto; Mioni, Renzo; Favretti, Michela; Ricci, Antonia

2015-01-01

The formulation of innovative packaging solutions, exerting a functional antimicrobial role in slowing down food spoilage, is expected to have a significant impact on the food industry, allowing both the maintenance of food safety criteria for longer periods and the reduction of food waste. Different materials are considered able to exert the required antimicrobial activity, among which are materials containing silver. However, challenges exist in the application of silver to food contact materials due to knowledge gaps in the production of ingredients, stability of delivery systems in food matrices and health risks caused by the same properties which also offer the benefits. Aims of the present study were to test the effectiveness and suitability of two packaging systems, one of which contained silver, for packaging and storing Stracchino cheese, a typical Italian fresh cheese, and to investigate if there was any potential for consumers to be exposed to silver, via migration from the packaging to the cheese. Results did not show any significant difference in the effectiveness of the packaging systems on packaged Stracchino cheese, excluding that the active packaging systems exerted an inhibitory effect on the growth of spoilage microorganisms. Moreover, silver migrated into the cheese matrix throughout the storage time (24 days). Silver levels in cheese finally exceeded the maximum established level for the migration of a non-authorised substance through a functional barrier (Commission of the European Communities, 2009). This result poses safety concerns and strongly suggests the need for more research aimed at better characterizing the new packaging materials in terms of their potential impacts on human health and the environment.

Integration of silver nanoparticle-impregnated polyelectrolyte multilayers into murine splinted cutaneous wound beds

PubMed Central

Guthrie, Kathleen M.; Agarwal, Ankit; Teixeira, Leandro B. C.; Dubielzig, Richard R.; Abbott, Nicholas L.; Murphy, Christopher J.; Singh, Harpreet; McAnulty, Jonathan F.; Schurr, Michael J.

2013-01-01

Silver is a commonly used topical antimicrobial. However, technologies to immobilize silver at the wound surface are lacking, while currently available silver-containing wound dressings release excess silver that can be cytotoxic and impair wound healing. We have shown that precise concentrations of silver at lower levels can be immobilized into a wound bed using a polyelectrolyte multilayer (PEM) attachment technology. These silver nanoparticle-impregnated PEMs are non-cytotoxic yet bactericidal in vitro, but their effect on wound healing in vivo was previously unknown. Objective The purpose of this study was to determine the effect on wound healing of integrating silver nanoparticle/PEMs into the wound bed. Methods A full-thickness, splinted, excisional murine wound healing model was employed in both phenotypically normal mice and spontaneously diabetic mice (healing impaired model). Results Gross image measurements showed an initial small lag in healing in the silver-treated wounds in diabetic mice, but no difference in time to complete wound closure in either normal or diabetic mice. Histological analysis showed modest differences between silver-treated and control groups on day 9, but no difference between groups at the time of wound closure. Conclusions We conclude that silver nanoparticle/PEMs can be safely integrated into the wound beds of both normal and diabetic mice without delaying wound closure, and with transient histological effects. The results of this study suggest the feasibility of this technology for use as a platform to effect nanoscale wound engineering approaches to microbial prophylaxis or to augment wound healing. PMID:23511285

The Release of Nanosilver from Consumer Products Used in the Home

PubMed Central

Benn, Troy; Cavanagh, Bridget; Hristovski, Kiril; Posner, Jonathan D.; Westerhoff, Paul

2016-01-01

Nanosilver has become one of the most widely used nanomaterials in consumer products because of its antimicrobial properties. Public concern over the potential adverse effects of nanosilver's environmental release has prompted discussion of federal regulation. In this paper, we assess several classes of consumer products for their silver content and potential to release nanosilver into water, air, or soil. Silver was quantified in a shirt, a medical mask and cloth, toothpaste, shampoo, detergent, a towel, a toy teddy bear, and two humidifiers. Silver concentrations ranged from 1.4 to 270,000 μg Ag g product−1. Products were washed in 500 mL of tap water to assess the potential release of silver into aqueous environmental matrices (wastewater, surface water, saliva, etc.). Silver was released in quantities up to 45 μg Ag g product−1, and size fractions were both larger and smaller than 100 nm. Scanning electron microscopy confirmed the presence of nanoparticle silver in most products as well as in the wash water samples. Four products were subjected to a toxicity characterization leaching procedure to assess the release of silver in a landfill. The medical cloth released an amount of silver comparable to the toxicity characterization limit. This paper presents methodologies that can be used to quantify and characterize silver and other nanomaterials in consumer products. The quantities of silver in consumer products can in turn be used to estimate real-world human and environmental exposure levels. PMID:21284285

A Combined Theoretical and Experimental Study for Silver Electroplating

PubMed Central

Liu, Anmin; Ren, Xuefeng; An, Maozhong; Zhang, Jinqiu; Yang, Peixia; Wang, Bo; Zhu, Yongming; Wang, Chong

2014-01-01

A novel method combined theoretical and experimental study for environmental friendly silver electroplating was introduced. Quantum chemical calculations and molecular dynamic (MD) simulations were employed for predicting the behaviour and function of the complexing agents. Electronic properties, orbital information, and single point energies of the 5,5-dimethylhydantoin (DMH), nicotinic acid (NA), as well as their silver(I)-complexes were provided by quantum chemical calculations based on density functional theory (DFT). Adsorption behaviors of the agents on copper and silver surfaces were investigated using MD simulations. Basing on the data of quantum chemical calculations and MD simulations, we believed that DMH and NA could be the promising complexing agents for silver electroplating. The experimental results, including of electrochemical measurement and silver electroplating, further confirmed the above prediction. This efficient and versatile method thus opens a new window to study or design complexing agents for generalized metal electroplating and will vigorously promote the level of this research region. PMID:24452389

Substrate effect on the growth of Sn thin films

NASA Astrophysics Data System (ADS)

Chakraborty, Suvankar; Menon, Krishnakumar S. R.

2018-05-01

Growth of tin (Sn) on Ag(001), Ag(111) and W(110) substrate has been studied at elevated temperatures (473 K) using x-ray photoemission spectroscopy (XPS) and low energy electron diffraction (LEED). For Sn growth on silver substrates, it is noticed that both Sn 3d and Ag 3d core-level spectra shift in the higher binding energy direction due to the formation of surface alloy with the substrate. In both cases, surface alloy finally transforms into bulk alloy finally reaching bulk Sn value. For Sn growth on W(110) only Sn 3d core-level spectra shift in the higher binding energy direction due to surface core-level effect whereas no shift for tungsten core-level was noticed confirming no alloy formation. Sn is incorporated into the surface of substrate silver layer by removing every alternate or every third silver atoms to relieve the surface tensile stress as confirmed by LEED. On the other hand, tungsten being hard, Sn forms an overlayer structure by sitting in different energetically available positions rather than forming an alloy as energetically also it is not possible. Sn forms alloy with soft substrate silver and form overlayer films with tungsten. These studies are important in understanding the growth mechanism of Sn films on metal substrates.

Production of silver ions from colloidal silver by nanoparticle iontophoresis system.

PubMed

Tseng, Kuo-Hsiung; Liao, Chih-Yu

2011-03-01

Metal ions, especially the silver ion, were used to treat infection before the initiation of antibiotic therapy. Unfortunately, there is a lack of research on the metallic nanoparticle suspension as a reservoir for metal ion release application. For medical purposes, conversion of colloidal silver into an ionic form is necessary, but not using silver salts (e.g., AgNO3, Ag2SO4), due to the fact that the counter-ion of silver salts may cause problems to the body as the silver ion (Ag+) is consumed. The goal of this research is to develop a silver nanoparticle iontophoresis system (NIS) which can provide a relatively safe bactericidal silver ion solution with a controllable electric field. In this study, ion-selective electrodes were used to identify and observe details of the system's activity. Both qualitative and quantitative data analyses were performed. The experimental results show that the ion releasing peak time (R(PT)) has an inversely proportional relationship with the applied current and voltage. The ion releasing maximum level (R(ML)) and dosage (R(D)) are proportional to the current density and inversely proportional to the voltage, respectively. These results reveal that the nanoparticle iontophoresis system (NIS) is an alternative method for the controlled release of a metal ion and the ion's concentration profile, by controlling the magnitude of current density (1 microA/cm2 equal to 1 ppm/hour) and applied voltage.

Toxicity of fungal-generated silver nanoparticles to soil-inhabiting Pseudomonas putida KT2440, a rhizospheric bacterium responsible for plant protection and bioremediation.

PubMed

Gupta, Indarchand R; Anderson, Anne J; Rai, Mahendra

2015-04-09

Silver nanoparticles have attracted considerable attention due to their beneficial properties. But toxicity issues associated with them are also rising. The reports in the past suggested health hazards of silver nanoparticles at the cellular, molecular, or whole organismal level in eukaryotes. Whereas, there is also need to examine the exposure effects of silver nanoparticle to the microbes, which are beneficial to humans as well as environment. The available literature suggests the harmful effects of physically and chemically synthesised silver nanoparticles. The toxicity of biogenically synthesized nanoparticles has been less studied than physically and chemically synthesised nanoparticles. Hence, there is a greater need to study the toxic effects of biologically synthesised silver nanoparticles in general and mycosynthesized nanoparticles in particular. In the present study, attempts have been made to assess the risk associated with the exposure of mycosynthesized silver nanoparticles on a beneficial soil microbe Pseudomonas putida. KT2440. The study demonstrates mycosynthesis of silver nanoparticles and their characterisation by UV-vis spectrophotometry, FTIR, X-ray diffraction, nanosight LM20--a particle size distribution analyzer and TEM. Silver nanoparticles obtained herein were found to exert the hazardous effect at the concentration of 0.4 μg/ml, which warrants further detailed investigations concerning toxicity. Copyright © 2014 Elsevier B.V. All rights reserved.

Silver nanoparticle assisted urine sugar determination using thermal lens spectroscopy

NASA Astrophysics Data System (ADS)

Thomas, Lincy; John, Jisha; George, Nibu A.; Kurian, Achamma

2014-11-01

Nanotechnology plays a vital role in the development of biosensors by enhancing their sensitivity and performance. In this paper, we report a novel urine sugar sensing method that makes use of the unique properties of silver-nanofluids in combination with the laser induced photothermal lens technique. The thermal lens signal decreases with increase in sugar levels in urine samples, which may be attributed to the enhanced interaction of glucose and conduction electrons of silver-nanoparticles, thereby changing the surface plasmon energy.

Xylary pH and Reduction Potential Levels of Iron-stressed Silver Maple (Acer saccharinum L.) 1

PubMed Central

Morris, Robert L.; Swanson, Bert T.

1980-01-01

Xylary fluid pH and reduction potentials were measured on silver maple (Acer saccharinum L.) grown under Fe and pH stress. Although pH and reduction potential (millivolt/59.2) varied significantly in the nutrient solution, xylary pH and reduction potential remained constant. It was concluded that changes in the pH and reduction potential in the xylary fluid of silver maple are not responsible for iron chlorosis. PMID:16661196

Determination of silver, bismuth, cadmium, copper, lead, and zinc in geologic materials by atomic absorption spectrometry with tricaprylylmethylammonium chloride

USGS Publications Warehouse

Viets, J.G.

1978-01-01

Interferences commonly encountered in the determination of silver, bismuth, cadmium, copper, lead, and zinc at crustal abundance levels are effectively eliminated using a rapid, sensitive, organic extraction technique. A potassium chlorate-hydrochloric acid digestion solubilizes the metals not tightly bound in the silicate lattice of rocks, soils, and stream sediments. The six metals are selectively extracted into a 10% Aliquat 336-MIBK organic phase in the presence of ascorbic acid and potassium iodide. Metals in the organic extract are determined by flame atomic absorption spectrometry to the 0.02-ppm level for silver, cadmium, copper, and zinc and to the 0.2-ppm level for bismuth and lead with a maximum relative standard deviation of 18.8% for known reference samples. An additional hydrofluoric acid digestion may be used to determine metals substituted in the silicate lattice.

Sexually disrupting effects of nonylphenol and diethylstilbestrol on male silver carp (Carassius auratus) in aquatic microcosms.

PubMed

Yang, Lihua; Lin, Li; Weng, Shaoping; Feng, Zhiqin; Luan, Tiangang

2008-10-01

Based on detected nonylphenol (NP) levels in aquaculture water, this study investigated sexually disrupting effects in mature male silver carp (Carassius auratus) exposed to NP and a positive control diethylstilbestrol (DES). The combined evidences of steroid hormone (17beta-estradiol, estrone and testosterone) levels and hispathological pictures showed that NP (10 microg/L) and DES could exert estrogenic effects through indirect mechanisms [i.e. increased estrogens levels (up to two times) and decreased androgen level in serum (down to 20-30%)], which might subsequently induce vitellogenin synthesis in liver. Environmental realistic concentrations of NP might be on the verge of inducing significant estrogenic effects in male silver carps. High amounts of NP and DES might be accumulated in fish serum, and the uptake by fish was possibly responsible for their quick attenuation in experimental tank water. NP and DES might have different metabolic mechanisms, the estrogenic effects of DES were more significant than those of NP.

A case of generalized argyria after ingestion of colloidal silver solution.

PubMed

Kim, Yangho; Suh, Ho Seok; Cha, Hee Jeong; Kim, Suk Hwan; Jeong, Kyoung Sook; Kim, Dong Hoon

2009-03-01

A 58-year-old woman was referred to our hospital due to progressive skin darkening, which began 5 months previously. The patient had strikingly diffuse blue-gray discoloration of the skin, most prominent in sun-exposed areas, especially her face and hands. The oral mucosa, tongue, gums, eye conjunctiva, ears, nail beds, and trunk were also involved. Bluish-gray discoloration of all nails was aggravated by cold weather. She had ingested 1 L of colloidal silver solution daily for approximately 16 months as a traditional remedy. Her serum silver concentration was 381 ng/ml which was a very high (reference level: <15 ng/ml). Light microscopic examination of a punch biopsy specimen from her nose revealed fine, minute, round, and brown-black granules deposited in the basement membrane of hair follicular epithelium. Scanning electron microscopic examination showed electron-dense granules deposited in the intercellular space of sweat glands. Energy disperse X-ray spectrometry analysis demonstrated peaks for silver and sulfur in the dense black deposits. The ingestion of colloidal silver appears to be an increasing practice among patients using alternative health practices. All silver-containing products including colloidal silver should be labeled with a clear warning to prevent argyria, especially in alternative health practices.

Point-of-Use Removal of Cryptosporidium parvum from Water: Independent Effects of Disinfection by Silver Nanoparticles and Silver Ions and by Physical Filtration in Ceramic Porous Media.

PubMed

Abebe, Lydia S; Su, Yi-Hsuan; Guerrant, Richard L; Swami, Nathan S; Smith, James A

2015-11-03

Ceramic water filters (CWFs) impregnated with silver nanoparticles are a means of household-level water treatment. CWFs remove/deactivate microbial pathogens by employing two mechanisms: metallic disinfection and physical filtration. Herein we report on the independent effects of silver salt and nanoparticles on Cryptosporidium parvum and the removal of C. parvum by physical filtration in porous ceramic filter media. Using a murine (mouse) model, we observed that treatment of oocysts with silver nitrate and proteinate-capped silver nanoparticles resulted in decreased infection relative to untreated oocysts. Microscopy and excystation experiments were conducted to support the disinfection investigation. Heat and proteinate-capped silver-nanoparticle treatment of oocysts resulted in morphological modifications and decreased excystation rates of sporozoites. Subsequently, disk-shaped ceramic filters were produced to investigate the transport of C. parvum. Two factors were varied: sawdust size and clay-to-sawdust ratio. Five disks were prepared with combinations of 10, 16, and 20 mesh sawdust and sawdust percentage that ranged from 9 to 11%. C. parvum removal efficiencies ranged from 1.5 log (96.4%) to 2.1 log (99.2%). The 16-mesh/10% sawdust had the greatest mean reduction of 2.1-log (99.2%), though there was no statistically significant difference in removal efficiency. Based on our findings, physical filtration and silver nanoparticle disinfection likely contribute to treatment of C. parvum for silver impregnated ceramic water filters, although the contribution of physical filtration is likely greater than silver disinfection.

Molecular responses differ between sensitive silver carp and tolerant bighead carp and bigmouth buffalo exposed to rotenone

USGS Publications Warehouse

Amberg, Jon J.; Schreier, Theresa M.; Gaikowski, Mark P.

2012-01-01

Some species of fish are more tolerant of rotenone, a commonly used non-specific piscicide, than others. This species-specific tolerance to rotenone has been thought to be associated with the uptake and the efficiency at which the chemical is detoxified. However, rotenone stimulates oxidative stress and superoxides, which are also toxic. Understanding the modes in which fish physiologically respond to rotenone is important in developing improved protocols for its application in controlling aquatic nuisance species. Using a molecular approach, we investigated the physiological and molecular mechanisms of rotenone resistance. Species-specific responses were observed when rotenone-sensitive silver, Hypophthalmichthys molitrix, and both rotenone-resistant bighead carp, Hypophthalmichthys nobilis, and bigmouth buffalo, Ictiobus cyprinellus, were exposed to rotenone. Rotenone levels in plasma were highest 90 min after exposure in both silver carp and bigmouth buffalo, but bigmouth buffalo tolerated over twice the burden (ng mL-1 g-1) than silver carp. Expression of genes related with detoxification (cyp1a and gst) increased in silver carp, but either decreased or remained the same in bighead carp. Genes linked with oxidative stress in the cytosol (gpx, cat and sod1) and hsp70 increased only in silver carp after a 6-h exposure. Expression of genes associated with oxidative stress in the mitochondria (sod2 and ucp2) differed between silver carp and bighead carp. Expression of sod2 changed minimally in bighead carp, but expression of ucp2 linearly increased to nearly 85-fold of the level prior to exposure. Expression of sod2 and ucp2 did not change until 6 h in silver carp. Use of sod1 and sod2 to combat oxidative stress results in hydrogen peroxide production, while use of ucp2 produces nitric oxide, a chemical known to inhibit apoptosis. We conclude that the mechanism at which a fish handles oxidative stress plays an important role in the tolerance to rotenone.

Estimating historical atmospheric mercury concentrations from silver mining and their legacies in present-day surface soil in Potosí, Bolivia

NASA Astrophysics Data System (ADS)

Hagan, Nicole; Robins, Nicholas; Hsu-Kim, Heileen; Halabi, Susan; Morris, Mark; Woodall, George; Zhang, Tong; Bacon, Allan; Richter, Daniel De B.; Vandenberg, John

2011-12-01

Detailed Spanish records of mercury use and silver production during the colonial period in Potosí, Bolivia were evaluated to estimate atmospheric emissions of mercury from silver smelting. Mercury was used in the silver production process in Potosí and nearly 32,000 metric tons of mercury were released to the environment. AERMOD was used in combination with the estimated emissions to approximate historical air concentrations of mercury from colonial mining operations during 1715, a year of relatively low silver production. Source characteristics were selected from archival documents, colonial maps and images of silver smelters in Potosí and a base case of input parameters was selected. Input parameters were varied to understand the sensitivity of the model to each parameter. Modeled maximum 1-h concentrations were most sensitive to stack height and diameter, whereas an index of community exposure was relatively insensitive to uncertainty in input parameters. Modeled 1-h and long-term concentrations were compared to inhalation reference values for elemental mercury vapor. Estimated 1-h maximum concentrations within 500 m of the silver smelters consistently exceeded present-day occupational inhalation reference values. Additionally, the entire community was estimated to have been exposed to levels of mercury vapor that exceed present-day acute inhalation reference values for the general public. Estimated long-term maximum concentrations of mercury were predicted to substantially exceed the EPA Reference Concentration for areas within 600 m of the silver smelters. A concentration gradient predicted by AERMOD was used to select soil sampling locations along transects in Potosí. Total mercury in soils ranged from 0.105 to 155 mg kg-1, among the highest levels reported for surface soils in the scientific literature. The correlation between estimated air concentrations and measured soil concentrations will guide future research to determine the extent to which the current community of Potosí and vicinity is at risk of adverse health effects from historical mercury contamination.

[Silver Hills Junior High School Talent Pool].

ERIC Educational Resources Information Center

Wallace School District 393, ID.

The paper describes the Silver Hills (Idaho) Junior High School Talent Pool, a program designed to advance thinking skills through enrichment activities. The Talent Pool concept was established as an alternate means of identifying students eligible for gifted/talented services and programs. Students participate in three levels of enrichment…

Method for the recovery of silver from waste photographic fixer solutions

DOEpatents

Posey, F.A.; Palko, A.A.

The method of the present invention is directed to the recovery of silver from spent photographic fixer solutions and for providing an effluent essentially silver-free that is suitable for discharge into commercial sewage systems. The present method involves the steps of introducing the spent photographic fixer solution into an alkaline hypochlorite solution. The oxidizing conditions of the alkaline hypochlorite solution are maintained during the addition of the fixer solution so that the silver ion complexing agents of thiosulfate and sulfite ions are effectively destroyed. Hydrazine monohydrate is then added to the oxidizing solution to form a reducing solution to effect the formation of a precipitate of silver which can be readily removed by filtration of decanting. Experimental tests indicate that greater than 99.99% of the original silver in the spent photographic fixer can be efficiently removed by practicing the present method. Also, the chemical and biological oxygen demand of the remaining effluent is significantly reduced so as to permit the discharge thereof into sewage systems at levels in compliance with federal and state environmental standards.

Method for the recovery of silver from waste photographic fixer solutions

DOEpatents

Posey, Franz A.; Palko, Aloysius A.

1984-01-01

The method of the present invention is directed to the recovery of silver from spent photographic fixer solutions and for providing an effluent essentially silver-free that is suitable for discharge into commercial sewage systems. The present method involves the steps of introducing the spent photographic fixer solution into an alkaline hypochlorite solution. The oxidizing conditions of the alkaline hypochlorite solution are maintained during the addition of the fixer solution so that the silver ion complexing agents of thiosulfate and sulfite ions are effectively destroyed. Hydrazine monohydrate is then added to the oxidizing solution to form a reducing solution to effect the formation of a precipitate of silver which can be readily removed by filtration or decanting. Experimental tests indicate that greater than 99.99% of the original silver in the spent photographic fixer can be efficiently removed by practicing the present method. Also, the chemical and biological oxygen demand of the remaining effluent is significantly reduced so as to permit the discharge thereof into sewage systems at levels in compliance with federal and state environmental standards.

Bioconcentration factors (BCF) of silver in wild Agaricus campestris

DOE Office of Scientific and Technical Information (OSTI.GOV)

Falandysz, J.; Danisiewicz, D.

Silver is an element naturally occurring in small concentrations in different environmental sites. However, many anthropogenic sources of silver led to contamination of this element in soil surfaces, pastures, and coastal marine areas in different parts of the world. Estimates are that 40% of the 1.15x10{sup 4}t of silver produced annually worldwide, will escape into the environment. Due to municipal waste discharge and/or industrial effluents with high silver concentrations, 100 x above the background level have been reported in invertebrate species from polluted marine areas. The meta-stabile radioisotope, {sup 110m}Ag, is a main component of the liquid effluents from nuclearmore » facilities under normal operating conditions. The presence of {sup 111}Ag and {sup 110m}Ag also has been widely found throughout Europe in the 1986 Chernobyl fallout. Silver ions are environmentally harmful. High toxic effects have been observed at low concentrations, especially in aquatic species. Species of lower fungi as well as the mushroom Agaricus bisporus are know to bioaccumulate high concentrations of silver when grown on an artificially enriched substrate. This study looks at the relationship between the silver content of soil and bioconcentration potential of wild Agaricus campestris from sites under different use and with different concentrations of heavy metals. 28 refs., 2 figs., 2 tabs.« less

In situ fabrication of silver nanoparticle-filled hydrogen titanate nanotube layer on metallic titanium surface for bacteriostatic and biocompatible implantation

PubMed Central

Wang, Zheng; Sun, Yan; Wang, Dongzhou; Liu, Hong; Boughton, Robert I

2013-01-01

A silver nanoparticle (AgNP)-filled hydrogen titanate nanotube layer was synthesized in situ on a metallic titanium substrate. In the synthesis approach, a layer of sodium titanate nanotubes is first prepared on the titanium surface by using a hydrothermal method. Silver nitrate solution is absorbed into the nanotube channels by immersing a dried nanotube layer in silver nitrate solution. Finally, silver ions are reduced by glucose, leading to the in situ growth of AgNPs in the hydrogen titanate nanotube channels. Long-term silver release and bactericidal experiments demonstrated that the effective silver release and effective antibacterial period of the titanium foil with a AgNP-filled hydrogen titanate nanotube layer on the surface can extend to more than 15 days. This steady and prolonged release characteristic is helpful to promote a long-lasting antibacterial capability for the prevention of severe infection after surgery. A series of antimicrobial and biocompatible tests have shown that the sandwich nanostructure with a low level of silver loading exhibits a bacteriostatic rate as high as 99.99%, while retaining low toxicity for cells and possessing high osteogenic potential. Titanium foil with a AgNP-filled hydrogen titanate nanotube layer on the surface that is fabricated with low-cost surface modification methods is a promising implantable material that will find applications in artificial bones, joints, and dental implants. PMID:23966780

Dose of radiation enhancement, using silver nanoparticles in a human tissue equivalent gel dosimeter.

PubMed

Hassan, Muhammad; Waheed, Muhammad Mohsin; Anjum, Muhammad Naeem

2016-01-01

To quantify the radiation dose enhancement in a human tissue-equivalent polymer gel impregnated with silver nanoparticles. The case-control study was conducted at the Bahawalpur Institute of Nuclear Medicine and Oncology, Bahawalpur, Pakistan, in January 2014. Silver nanoparticles used in this study were prepared by wet chemical method. Polymer gel was prepared by known quantity of gelatine, methacrylic acid, ascorbic acid, copper sulphate pentahydrate, hydroquinone and water. Different concentrations of silver nanoparticles were added to the gel during its cooling process. The gel was cooled in six plastic vials of 50ml each. Two vials were used as a control sample while four vials were impregnated with silver nanoparticles. After 22 hours, the vials were irradiated with gamma rays by aCobalt-60 unit. Radiation enhancement was assessed by taking magnetic resonance images of the vials. The images were analysed using Image J software. The dose enhancement factor was 24.17% and 40.49% for 5Gy and 10Gy dose respectively. The dose enhancement factor for the gel impregnated with 0.10mM silver nanoparticles was 32.88% and 51.98% for 5Gy and 10Gy dose respectively. The impregnation of a tissue-equivalent gel with silver nanoparticles resulted in dose enhancement and this effect was magnified up to a certain level with the increase in concentration of silver nanoparticles.

Toxicological studies on silver nanoparticles: challenges and opportunities in assessment, monitoring and imaging

PubMed Central

Stensberg, Matthew Charles; Wei, Qingshan; McLamore, Eric Scott; Porterfield, David Marshall; Wei, Alexander; Sepúlveda, Marĺa Soledad

2012-01-01

Silver nanoparticles (Ag NPs) are becoming increasingly prevalent in consumer products as antibacterial agents. The increased use of Ag NP-enhanced products may lead to an increase in toxic levels of environmental silver, but regulatory control over the use or disposal of such products is lagging due to insufficient assessment on the toxicology of Ag NPs and their rate of release into the environment. In this article we discuss recent research on the transport, activity and fate of Ag NPs at the cellular and organismic level, in conjunction with traditional and recently established methods of nanoparticle characterization. We include several proposed mechanisms of cytotoxicity based on such studies, as well as new opportunities for investigating the uptake and fate of Ag NPs in living systems. PMID:21793678

Effects of particle size and coating on toxicologic parameters, fecal elimination kinetics and tissue distribution of acutely ingested silver nanoparticles in a mouse model

PubMed Central

Bergin, Ingrid L.; Wilding, Laura A.; Morishita, Masako; Walacavage, Kim; Ault, Andrew P.; Axson, Jessica L.; Stark, Diana I.; Hashway, Sara A.; Capracotta, Sonja S.; Leroueil, Pascale R.; Maynard, Andrew D.; Philbert, Martin A.

2015-01-01

Consumer exposure to silver nanoparticles (AgNP) via ingestion can occur due to incorporation of AgNP into products such as food containers and dietary supplements. AgNP variations in size and coating may affect toxicity, elimination kinetics or tissue distribution. Here, we directly compared acute administration of AgNP of two differing coatings and sizes to mice, using doses of 0.1, 1 and 10 mg/kg body weight/day administered by oral gavage for 3 days. The maximal dose is equivalent to 2000× the EPA oral reference dose. Silver acetate at the same doses was used as ionic silver control. We found no toxicity and no significant tissue accumulation. Additionally, no toxicity was seen when AgNP were dosed concurrently with a broad-spectrum antibiotic. Between 70.5% and 98.6% of the administered silver dose was recovered in feces and particle size and coating differences did not significantly influence fecal silver. Peak fecal silver was detected between 6- and 9-h post-administration and <0.5% of the administered dose was cumulatively detected in liver, spleen, intestines or urine at 48 h. Although particle size and coating did not affect tissue accumulation, silver was detected in liver, spleen and kidney of mice administered ionic silver at marginally higher levels than those administered AgNP, suggesting that silver ion may be more bioavailable. Our results suggest that, irrespective of particle size and coating, acute oral exposure to AgNP at doses relevant to potential human exposure is associated with predominantly fecal elimination and is not associated with accumulation in tissue or toxicity. PMID:26305411

A physiologically based pharmacokinetic model for ionic silver and silver nanoparticles

PubMed Central

Bachler, Gerald; von Goetz, Natalie; Hungerbühler, Konrad

2013-01-01

Silver is a strong antibiotic that is increasingly incorporated into consumer products as a bulk, salt, or nanosilver, thus potentially causing side-effects related to human exposure. However, the fate and behavior of (nano)silver in the human body is presently not well understood. In order to aggregate the existing experimental information, a physiologically based pharmacokinetic model (PBPK) was developed in this study for ionic silver and nanosilver. The structure of the model was established on the basis of toxicokinetic data from intravenous studies. The number of calibrated parameters was minimized in order to enhance the predictive capability of the model. We validated the model structure for both silver forms by reproducing exposure conditions (dermal, oral, and inhalation) of in vivo experiments and comparing simulated and experimentally assessed organ concentrations. Therefore, the percutaneous, intestinal, or pulmonary absorption fraction was estimated based on the blood silver concentration of the respective experimental data set. In all of the cases examined, the model could successfully predict the biodistribution of ionic silver and 15–150 nm silver nanoparticles, which were not coated with substances designed to prolong the circulatory time (eg, polyethylene glycol). Furthermore, the results of our model indicate that: (1) within the application domain of our model, the particle size and coating had a minor influence on the biodistribution; (2) in vivo, it is more likely that silver nanoparticles are directly stored as insoluble salt particles than dissolve into Ag+; and (3) compartments of the mononuclear phagocytic system play a minor role in exposure levels that are relevant for human consumers. We also give an example of how the model can be used in exposure and risk assessments based on five different exposure scenarios, namely dietary intake, use of three separate consumer products, and occupational exposure. PMID:24039420

Silver Nanowire Exposure Results in Internalization and Toxicity to Daphnia Magna

PubMed Central

Scanlan, Leona D.; Reed, Robert B.; Loguinov, Alexandre V.; Antczak, Philipp; Tagmount, Abderrahmane; Aloni, Shaul; Nowinski, Daniel Thomas; Luong, Pauline; Tran, Christine; Karunaratne, Nadeeka; Pham, Don; Lin, Xin Xin; Falciani, Francesco; Higgins, Chris P.; Ranville, James F.; Vulpe, Chris D.; Gilbert, Benjamin

2013-01-01

Nanowires (NWs), high-aspect-ratio nanomaterials, are increasingly used in technological materials and consumer products and may have toxicological characteristics distinct from nanoparticles. We carried out a comprehensive evaluation of the physico-chemical stability of four silver nanowires (AgNWs) of two sizes and coatings and their toxicity to Daphnia magna. Inorganic aluminum-doped silica coatings were less effective than organic poly(vinyl pyrrolidone) coatings at preventing silver oxidation or Ag+ release and underwent a significant morphological transformation within one-hour following addition to low ionic strength Daphnia growth media. All AgNWs were highly toxic to D. magna but less toxic than ionic silver. Toxicity varied as a function of AgNW dimension, coating and solution chemistry. Ag+ release in the media could not account for observed AgNW toxicity. Single-particle inductively coupled plasma mass spectrometry (spICPMS) distinguished and quantified dissolved and nanoparticulate silver in microliter-scale volumes of Daphnia magna hemolymph with a limit of detection of approximately 10 ppb. The silver levels within the hemolymph of Daphnia exposed to both Ag+ and AgNW met or exceeded the initial concentration in the growth medium, indicating effective accumulation during filter feeding. Silver-rich particles were the predominant form of silver in hemolymph following exposure to both AgNWs and Ag+. Scanning electron microscopy (SEM) imaging of dried hemolymph found both AgNWs and silver precipitates that were not present in the AgNW stock or the growth medium. Both organic and inorganic coatings on the AgNW were transformed during ingestion or absorption. Pathway, gene ontology and clustering analyses of gene expression response indicated effects of AgNWs distinct from ionic silver on Daphnia magna. PMID:24099093

Water Quality and Hydrology of Silver Lake, Barron County, Wisconsin, With Special Emphasis on Responses of a Terminal Lake to Changes in Phosphorus Loading and Water Level

USGS Publications Warehouse

Robertson, Dale M.; Rose, William J.; Fitzpatrick, Faith A.

2009-01-01

Silver Lake is typically an oligotrophic-to-mesotrophic, soft-water, terminal lake in northwestern Wisconsin. A terminal lake is a closed-basin lake with surface-water inflows but no surface-water outflows to other water bodies. After several years with above-normal precipitation, very high water levels caused flooding of several buildings near the lake and erosion of soil around much of the shoreline, which has been associated with a degradation in water quality (increased phosphorus and chlorophyll a concentrations and decreased water clarity). To gain a better understanding of what caused the very high water levels and degradation in water quality and collect information to better understand the lake and protect it from future degradation, the U.S. Geological Survey did a detailed study from 2004 to 2008. This report describes results of the study; specifically, lake-water quality, historical changes in water level, water and phosphorus budgets for the two years monitored in the study, results of model simulations that demonstrate how changes in phosphorus inputs affect lake-water quality, and the relative importance of changes in hydrology and changes in the watershed to the water quality of the lake. From 1987 to about 1996, water quality in Silver Lake was relatively stable. Since 1996, however, summer average total phosphorus concentrations increased from about 0.008 milligrams per liter (mg/L) to 0.018 mg/L in 2003, before decreasing to 0.011 mg/L in 2008. From 1996 to 2003, Secchi depths decreased from about 14 to 7.4 feet, before increasing to about 19 feet in 2008. Therefore, Silver Lake is typically classified as oligotrophic to mesotrophic; however, during 2002-4, the lake was classified as mesotrophic to eutrophic. Because productivity in Silver Lake is limited by phosphorus, phosphorus budgets for the lake were constructed for monitoring years 2005 and 2006. The average annual input of phosphorus was 216 pounds: 78 percent from tributary and nearshore runoff and 22 percent from atmospheric deposition. Because Silver Lake is hydraulically mounded above the local groundwater system, little or no input of phosphorus to the lake is from groundwater and septic systems. Silver Lake had previously been incorrectly described as a groundwater flowthrough lake. Phosphorus budgets were constructed for a series of dry years (low water levels) and a series of wet years (high water levels). About 6 times more phosphorus was input to the lake during wet years with high water levels than during the dry years. Phosphorus from erosion represented 13-20 percent of the phosphorus input during years with very high water levels. Results from the Canfield and Bachman eutrophication model and Carlson trophic state index equations demonstrated that water quality in Silver Lake directly responds to changes in external phosphorus input, with the percent change in chlorophyll a being about 80 percent of the percent change in total phosphorus input and the change in Secchi depth and total phosphorus concentrations being about 40 and 50 percent of the percent change in input, respectively. Therefore, changes in phosphorus input should impact water quality. Specific scenarios were simulated with the models to describe the effects of natural (climate-driven) and anthropogenic (human-induced) changes. Results of these scenarios demonstrated that several years of above-normal precipitation cause sustained high water levels and a degradation in water quality, part of which is due to erosion of the shoreline. Results also demonstrated that 1) changes in tributary and nearshore runoff have a dramatic effect on lake-water quality, 2) diverting water into the lake to increase the water level is expected to degrade the water quality, and 3) removal of water to decrease the water level of the lake is expected to have little effect on water quality. Fluctuations in water levels since 1967, when records began for the lake, are representative

Disinfection effects of undoped and silver-doped ceria powders of nanometer crystallite size

PubMed Central

Tsai, Dah-Shyang; Yang, Tzu-Sen; Huang, Yu-Sheng; Peng, Pei-Wen; Ou, Keng-Liang

2016-01-01

Being endowed with an ability of capturing and releasing oxygen, the ceria surface conventionally assumes the role of catalyzing redox reactions in chemistry. This catalytic effect also makes possible its cytotoxicity toward microorganisms at room temperature. To study this cytotoxicity, we synthesized the doped and undoped ceria particles of 8–9 nm in size using an inexpensive precipitation method and evaluated their disinfecting aptitudes with the turbidimetric and plate count methods. Among the samples being analyzed, the silver-doped ceria exhibits the highest sterilization ability, yet the undoped ceria is the most intriguing. The disinfection effect of undoped ceria is moderate in magnitude, demanding a physical contact between the ceria surface and bacteria cell wall, or the redox catalysis that can damage the cell wall and result in the cell killing. Evidently, this effect is short-range and depends strongly on dispersion of the nanoparticles. In contrast, the disinfection effects of silver-doped ceria reach out several millimeters since it releases silver ions to poison the surrounding microorganisms. Additionally, the aliovalent silver substitution creates more ceria defects. The synergetic combination, silver poisoning and heterogeneous redox catalysis, lifts and extends the disinfecting capability of silver-doped ceria to a superior level. PMID:27330294

Silver and Nitrate Oppositely Modulate Antimony Susceptibility through Aquaglyceroporin 1 in Leishmania (Viannia) Species

PubMed Central

Andrade, Juvana M.; Baba, Elio H.; Machado-de-Avila, Ricardo A.; Chavez-Olortegui, Carlos; Demicheli, Cynthia P.; Frézard, Frédéric

2016-01-01

Antimony (Sb) resistance in leishmaniasis chemotherapy has become one of the major challenges to the control of this spreading worldwide public health problem. Since the plasma membrane pore-forming protein aquaglyceroporin 1 (AQP1) is the major route of Sb uptake in Leishmania, functional studies are relevant to characterize drug transport pathways in the parasite. We generated AQP1-overexpressing Leishmania guyanensis and L. braziliensis mutants and investigated their susceptibility to the trivalent form of Sb (SbIII) in the presence of silver and nitrate salts. Both AQP1-overexpressing lines presented 3- to 4-fold increased AQP1 expression levels compared with those of their untransfected counterparts, leading to an increased SbIII susceptibility of about 2-fold. Competition assays using silver nitrate, silver sulfadiazine, or silver acetate prior to SbIII exposure increased parasite growth, especially in AQP1-overexpressing mutants. Surprisingly, SbIII-sodium nitrate or SbIII-potassium nitrate combinations showed significantly enhanced antileishmanial activities compared to those of SbIII alone, especially against AQP1-overexpressing mutants, suggesting a putative nitrate-dependent modulation of AQP1 activity. The intracellular level of antimony quantified by graphite furnace atomic absorption spectrometry showed that the concomitant exposure to SbIII and nitrate favors antimony accumulation in the parasite, increasing the toxicity of the drug and culminating with parasite death. This is the first report showing evidence of AQP1-mediated SbIII susceptibility modulation by silver in Leishmania and suggests the potential antileishmanial activity of the combination of nitrate salts and SbIII. PMID:27161624

Silver and Nitrate Oppositely Modulate Antimony Susceptibility through Aquaglyceroporin 1 in Leishmania (Viannia) Species.

PubMed

Andrade, Juvana M; Baba, Elio H; Machado-de-Avila, Ricardo A; Chavez-Olortegui, Carlos; Demicheli, Cynthia P; Frézard, Frédéric; Monte-Neto, Rubens L; Murta, Silvane M F

2016-08-01

Antimony (Sb) resistance in leishmaniasis chemotherapy has become one of the major challenges to the control of this spreading worldwide public health problem. Since the plasma membrane pore-forming protein aquaglyceroporin 1 (AQP1) is the major route of Sb uptake in Leishmania, functional studies are relevant to characterize drug transport pathways in the parasite. We generated AQP1-overexpressing Leishmania guyanensis and L. braziliensis mutants and investigated their susceptibility to the trivalent form of Sb (Sb(III)) in the presence of silver and nitrate salts. Both AQP1-overexpressing lines presented 3- to 4-fold increased AQP1 expression levels compared with those of their untransfected counterparts, leading to an increased Sb(III) susceptibility of about 2-fold. Competition assays using silver nitrate, silver sulfadiazine, or silver acetate prior to Sb(III) exposure increased parasite growth, especially in AQP1-overexpressing mutants. Surprisingly, Sb(III)-sodium nitrate or Sb(III)-potassium nitrate combinations showed significantly enhanced antileishmanial activities compared to those of Sb(III) alone, especially against AQP1-overexpressing mutants, suggesting a putative nitrate-dependent modulation of AQP1 activity. The intracellular level of antimony quantified by graphite furnace atomic absorption spectrometry showed that the concomitant exposure to Sb(III) and nitrate favors antimony accumulation in the parasite, increasing the toxicity of the drug and culminating with parasite death. This is the first report showing evidence of AQP1-mediated Sb(III) susceptibility modulation by silver in Leishmania and suggests the potential antileishmanial activity of the combination of nitrate salts and Sb(III). Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Reactivity and Catalytic Activity of Hydrogen Atom Chemisorbed Silver Clusters.

PubMed

Manzoor, Dar; Pal, Sourav

2015-06-18

Metal clusters of silver have attracted recent interest of researchers as a result of their potential in different catalytic applications and low cost. However, due to the completely filled d orbital and very high first ionization potential of the silver atom, the silver-based catalysts interact very weakly with the reacting molecules. In the current work, density functional theory calculations were carried out to investigate the effect of hydrogen atom chemisorption on the reactivity and catalytic properties of inert silver clusters. Our results affirm that the hydrogen atom chemisorption leads to enhancement in the binding energy of the adsorbed O2 molecule on the inert silver clusters. The increase in the binding energy is also characterized by the decrease in the Ag-O and increase in the O-O bond lengths in the case of the AgnH silver clusters. Pertinent to the increase in the O-O bond length, a significant red shift in the O-O stretching frequency is also noted in the case of the AgnH silver clusters. Moreover, the hydrogen atom chemisorbed silver clusters show low reaction barriers and high heat of formation of the final products for the environmentally important CO oxidation reaction as compared to the parent catalytically inactive clusters. The obtained results were compared with those of the corresponding gold and hydrogen atom chemisorbed gold clusters obtained at the same level of theory. It is expected the current computational study will provide key insights for future advances in the design of efficient nanosilver-based catalysts through the adsorption of a small atom or a ligand.

Synthesis and Characterization of BSA Conjugated Silver Nanoparticles (Ag/BSA Nanoparticles) and Evaluation of Biological Properties of Ag/BSA Nanoparticles and Ag/BSA Nanoparticles Loaded Poly(hydroxy butyrate valerate) PHBV Films

NASA Astrophysics Data System (ADS)

Ambaye, Almaz

Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa are the etiological agents of several infectious diseases. Antibiotic resistance by these three microbes has emerged as a prevalent problem due in part to the misuse of existing antibiotics and the lack of novel antibiotics. Nanoparticles have emerged as an alternative antibacterial agents to conventional antibiotics owing to their high surface area to volume ratio and their unique chemical and physical properties. Among the nanoparticles, silver nanoparticles have gained increasing attention because silver nanoparticles exhibit antibacterial activity against a range of gram positive and gram negative bacteria. Nanoparticles of well-defined chemistry and morphology can be used in broad biomedical applications, especially in bone tissue engineering applications, where bone infection by bacteria can be acute and lethal. It is commonly noted in the literature that the activity of nanoparticles against microorganisms is dependent upon the size and concentration of the nanoparticles as well as the chemistry of stabilizing agent. To the best of our knowledge, a comprehensive study that evaluates the antibacterial activity of well characterized silver nanoparticles in particular Bovine Serum Albumin (BSA) stabilized against S. aureus and E. coli and cytotoxicity level of BSA stabilized silver nanoparticles towards osteoblast cells (MC3T3-E1) is currently lacking. Therefore, the primary objective of this study was to characterize protein conjugated silver nanoparticles prepared by chemical reduction of AgNO3 and BSA mixture. The formation of Ag/BSA nanoparticles was studied by UV-Vis spectroscopy. The molar ratio of silver to BSA in the Ag/BSA nanoparticles was established to be 27+/- 3: 1, based on Thermogravimetric Analysis and Atomic Absorption Spectroscopy. Based on atomic force microscopy, dynamic light scattering,and transmission electron microscopy(TEM) measurements, the particle size (diameter) of Ag/BSA nanoparticles was found to be in a range of 9-13 nm. X-ray photo electron spectroscopy measurements of argon sputtered Ag/BSA nanoparticles provided evidence that the outer and inner region of nanoparticles are mainly composed of BSA and silver, respectively. Having characterized the nanoparticles, the next phase of the study was to evaluate the antibacterial activity and cytotoxicity level of BSA stabilized silver nanoparticles. The antibacterial efficacy of Ag/BSA nanoparticles against E. coli and S. aureus was evaluated, and minimum lethal concentration was found to be 2ppm and 7ppm, respectively. E. coli showed a higher susceptibility to silver nanoparticles than S. aureus, which could be attributed to the difference in the cell wall structure. We have also investigated the cytotoxicity level of Ag/BSA nanoparticles towards MC3T3-E1 osteoblast cells. The minimum bactericidal concentration found for both strains is lower than the silver nanoparticles concentration that was toxic to the osteoblast cells. Preliminary studies of Ag/BSA nanoparticles loaded collagen immobilized PHBV film showed that the Ag/BSA nanoparticles loaded PHBV film inhibit bacterial growth. The findings of our study can be extremely useful in the design of novel scaffold to address the critical needs of bone tissue engineering community.

Effects of Disinfectants in Water on Mir- and Earth-Grown Wheat

NASA Technical Reports Server (NTRS)

Campbell, William .F.; Bubenheim, D. L.; Bugbee, B.; Salisbury, F. B.; Bingham, G. E.; Levinskikh, M.; Sytchev, V. N.; Ivanova, I.; Chernova, L.; Podolsky, I.

2002-01-01

Iodine and silver fluoride are used to purify water onboard U. S. Shuttles and the Russian Space Station, Mir, respectively. In 1995, iodine-treated water, which ranged from 1.0-4.0 mg x kg(exp -1) with a mean of 2.9 mg x kg(exp -1), was applied to Super Dwarf wheat (Triticum aestivum L.) plants when Mir water (grey or tech grade) became scarce. The potential phytotoxicity of iodine on Super Dwarf wheat is an unknown. Since use of iodine-treated water was not part of the experiment, we sought to determine whether it accounted for the subsequent poor wheat seedling growth and floral development onboard the Mir. Super Dwarf wheat seeds were imbibed in iodine or silver fluoride concentrations of 0.0, 1.0, 2.0, 4.0, 8.0 or 16.0 mg x kg(exp -1) for 96 h at 4 C. Five seeds were then planted per 13.3 cm x 13.3 cm pots containing a granular clinoptilolite (Cp) zeolite (1 -2 mm dia.) and placed in Percival(TM) growth chambers programmed for 20/15 C and 18/6 h d/n regime. Plants were irrigated with distilled water, and Iodine- or silver fluoride-treated distilled water. In separate experiments, seeds were treated as above and germination and early seedling growth were determined by examining seedling responses to disinfectants in rolled paper towels. Silver fluoride had very little effect on wheat seed germination. By contrast, iodine reduced germination at all treatment levels. Seedlings exposed to 1.0, 2.0, and 4.0 mg x kg(exp -1) of iodine or silver fluoride levels exhibited a slight stimulation in shoot and root growth. Both disinfectants at 8 and 16 mg x kg(exp -1) showed significantly (p is less than or equal to 0.01) reduced seedling shoot and root lengths and fresh biomasses compared to the control and lower disinfectant levels. The number of spikelets per spike, florets per spikelet, seeds per spike and seed weight were also significantly reduced at the 8 and 16 mg x kg(exp -1) compared to the control and lower levels of disinfectant. Based on these ground-based post-flight analyses, the levels of iodine- and/or silver fluoride-treated water used on Mir-grown plants onboard the Mir did not cause the poor growth and development of the wheat plants.

Species- and size-specific variability of mercury concentrations in four commercially important finfish and their prey from the northwest Atlantic.

PubMed

Staudinger, Michelle D

2011-04-01

Total mercury was analyzed as a function of body length, season, and diet in four commercially and recreationally important marine fish, bluefish (Pomatomus saltatrix), goosefish (Lophius americanus), silver hake (Merluccius bilinearis), and summer flounder (Paralichthys dentatus), collected from continental shelf waters of the northwest Atlantic Ocean. Mercury levels in the dorsal muscle tissue of 115 individuals ranged from 0.006 to 1.217 μg/g (wet weight) and varied significantly among species. The relationship between predator length and mercury concentration was linear for bluefish and summer flounder, while mercury levels increased with size at an exponential rate for silver hake and goosefish. Mercury burdens were the highest overall in bluefish, but increased with size at the greatest rate in silver hake. Seasonal differences were detected for bluefish and goosefish with mercury levels peaking during summer and spring, respectively. Prey mercury burdens and predator foraging habits are discussed as the primary factors influencing mercury accumulation. Copyright © 2011 Elsevier Ltd. All rights reserved.

Laser Processed Silver Nanowire Network Transparent Electrodes for Novel Electronic Devices

NASA Astrophysics Data System (ADS)

Spechler, Joshua Allen

Silver nanowire network transparent conducting layers are poised to make headway into a space previously dominated by transparent conducting oxides due to the promise of a flexible, scaleable, lab-atmosphere processable alternative. However, there are many challenges standing in the way between research scale use and consumer technology scale adaptation of this technology. In this thesis we will explore many, and overcome a few of these challenges. We will address the poor conductivity at the narrow nanowire-nanowire junction points in the network by developing a laser based process to weld nanowires together on a microscopic scale. We address the need for a comparative metric for transparent conductors in general, by taking a device level rather than a component level view of these layers. We also address the mechanical, physical, and thermal limitations to the silver nanowire networks by making composites from materials including a colorless polyimide and titania sol-gel. Additionally, we verify our findings by integrating these processes into devices. Studying a hybrid organic/inorganic heterojunction photovoltaic device we show the benefits of a laser processed electrode. Green phosphorescent organic light emitting diodes fabricated on a solution phase processed silver nanowire based electrode show favorable device metrics compared to a conductive oxide electrode based control. The work in this thesis is intended to push the adoption of silver nanowire networks to further allow new device architectures, and thereby new device applications.

Deliberately Designed Atomic-Level Silver-Containing Interface Results in Improved Rate Capability and Utilization of Silver Hollandite for Lithium-Ion Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Paul F.; Brady, Alexander B.; Lee, Seung-Yong

α-MnO 2-structured materials are generally classified as semiconductors, thus we present a strategy to increase electrochemical utilization through design of a conductive material interface. Surface treatment of silver hollandite (Ag xMn 8O 16) with Ag + (Ag 2O) provides significant benefit to the resultant electrochemistry, including a decreased charge transfer resistance, and a 2-fold increase in deliverable energy density at high rate. The improved function of this designed interface relative to conventional electrode fabrication strategies is further highlighted.

Deliberately Designed Atomic-Level Silver-Containing Interface Results in Improved Rate Capability and Utilization of Silver Hollandite for Lithium-Ion Storage

DOE PAGES

Smith, Paul F.; Brady, Alexander B.; Lee, Seung-Yong; ...

2017-12-11

α-MnO 2-structured materials are generally classified as semiconductors, thus we present a strategy to increase electrochemical utilization through design of a conductive material interface. Surface treatment of silver hollandite (Ag xMn 8O 16) with Ag + (Ag 2O) provides significant benefit to the resultant electrochemistry, including a decreased charge transfer resistance, and a 2-fold increase in deliverable energy density at high rate. The improved function of this designed interface relative to conventional electrode fabrication strategies is further highlighted.

Glass-(nAg, nCu) biocide coatings on ceramic oxide substrates.

PubMed

Esteban-Tejeda, Leticia; Malpartida, Francisco; Díaz, Luis Antonio; Torrecillas, Ramón; Rojo, Fernando; Moya, José Serafín

2012-01-01

The present work was focused on obtaining biocide coatings constituted by a glassy soda-lime matrix containing silver or copper nanoparticles on ceramic (alumina and zirconia based) substrates. Both glassy coatings showed a high biocide activity against Gram-, Gram+ bacteria and yeast, reducing cell numbers more than three logarithms. Silver nanoparticles had a significantly higher biocide activity than copper nanoparticles, since the lixiviation levels required to reduce cell numbers more than 3 logarithms was of almost 1-2 µg/cm(2) in the case of silver nanoparticles, and 10-15 µg/cm(2) for the copper nanoparticles.

Analysis of metals with luster: Roman brass and silver

NASA Astrophysics Data System (ADS)

Fajfar, H.; Rupnik, Z.; Šmit, Ž.

2015-11-01

Non-destructive PIXE analysis using in-air proton beam was used for the studies of earliest brass coins issued during the 1st century BC by Greek cities in Asia Minor, Romans and Celts, and for the studies of plated low grade silver coins of the 3rd century AD. The analysis determined the levels of zinc and important trace elements, notably selenium, which confirms spread of selenium-marked copper from the east. For plating, combined tinning and silvering was identified by the mapping technique for the mid 3rd century AD, which evolved into mere plating by 270 AD.

SDT: The Brazilian Standardization of the Silver Drawing Test of Cognition and Emotion.

ERIC Educational Resources Information Center

Allessandrini, Cristina Dias; Duarte, Jose Luclano Miranda; Bianco, Marisa Fernandes; Dupas, Margarida Azevedo

1998-01-01

The Silver Drawing Test of Cognition and Emotion was standardized for Brazilian children (N=2,000). ANOVA results are presented for age and education groups from early grades on, including distinguishing adult education levels; results are compared for U.S. and Brazilian populations. Growth in test scores, emotional content responses, and…

Height diameter relations of maple street trees

Treesearch

David J. Nowak

1990-01-01

Height and diameter measurements were taken for silver, sugar and Norway maple street trees in Rochester and Syracuse, New York. Mature silver maples proved to be the tallest of the three species. Average sugar maple height was consistently taller than Norway maple height until diameters reached 28 inches. Average mature tree height for all three species level off in...

Disinfection of Escherichia coli Gram negative bacteria using surface modified TiO2: optimization of Ag metallization and depiction of charge transfer mechanism.

PubMed

Gomathi Devi, LakshmipathiNaik; Nagaraj, Basavalingaiah

2014-01-01

The antibacterial activity of silver deposited TiO2 (Ag-TiO2 ) against Gram negative Escherichia coli bacteria was investigated by varying the Ag metal content from 0.10 to 0.50% on the surface of TiO2 . Ag depositions by the photoreduction method were found to be stable. Surface silver metallization was confirmed by EDAX and XPS studies. Photoluminescence studies show that the charge carrier recombination is less for 0.1% Ag-TiO2 and this catalyst shows superior bactericidal activity under solar light irradiation compared to Sol gel TiO2 (SG-TiO2 ) due to the surface plasmon effect. The energy levels of deposited Ag are dependent on the Ag content and it varies from -4.64 eV to -1.30 eV with respect to the vacuum energy level based on atomic silver to bulk silver deposits. The ability of electron transfer from Ag deposit to O2 depends on the position of the energy levels. The 0.25% and 0.50% Ag depositions showed detrimental effect on bactericidal activity due to the mismatch of energy levels. The effect of the EROS (External generation of the Reactive Oxygen Species by 0.1% Ag-TiO2 ) and IROS (Interior generation of Reactive Oxygen Species within the bacteria) on the bactericidal inactivation is discussed in detail. © 2014 The American Society of Photobiology.

Electrochemical synthesis, characterisation and phytogenic properties of silver nanoparticles

NASA Astrophysics Data System (ADS)

Singaravelan, R.; Bangaru Sudarsan Alwar, S.

2015-12-01

This work exemplifies a simple and rapid method for the synthesis of silver nanodendrite with a novel electrochemical technique. The antibacterial activity of these silver nanoparticles (Ag NPs) against pathogenic bacteria was investigated along with the routine study of optical and spectral characterisation. The optical properties of the silver nanoparticles were characterised by diffuse reflectance spectroscopy. The optical band gap energy of the electrodeposited Ag NPs was determined from the diffuse reflectance using Kubelka-Munk formula. X-ray diffraction (XRD) studies were carried out to determine the crystalline nature of the silver nanoparticles which confirmed the formation of silver nanocrystals. The XRD pattern revealed that the electrodeposited Ag NPs were in the cubic geometry with dendrite preponderance. The average particle size and the peak broadening were deliberated using Debye-Scherrer equation and lattice strain due to the peak broadening was studied using Williamson-Hall method. Surface morphology of the Ag NPs was characterised by high-resolution scanning electron microscope and the results showed the high degree of aggregation in the particles. The antibacterial activity of the Ag NPs was evaluated and showed unprecedented level antibacterial activity against multidrug resistant strains such as Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumonia and Escherichia coli in combination with Streptomycin.

EPG waveform library for Graphocephala atropunctata (Hemiptera: Cicadellidae): Effect of adhesive, input resistor, and voltage levels on waveform appearance and stylet probing behaviors.

PubMed

Cervantes, Felix A; Backus, Elaine A

2018-05-31

Blue-green sharpshooter, Graphocephala atropunctata, is a native California vector of Xylella fastidiosa (Xf), a foregut-borne bacterium that is the causal agent of Pierce's disease in grapevines. A 3rd-generation, AC-DC electropenetrograph (EPG monitor) was used to record stylet probing and ingestion behaviors of adult G. atropunctata on healthy grapevines. This study presents for the first time a complete, updated waveform library for this species, as well as effects of different electropenetrograph settings and adhesives on waveform appearances. Both AC and DC applied signals were used with input resistor (Ri) levels (amplifier sensitivities) of 10 6 , 10 7 , 10 8 and 10 9  Ohms, as well as two type of adhesives, conducting silver paint and handmade silver glue. Waveform description, characterization of electrical origins (R versus emf components), and proposed biological meanings of waveforms are reported, as well as qualitative differences in waveform appearances observed with different electropenetrograph settings and adhesives. In addition, a quantitative study with AC signal, using two applied voltage levels (50 and 200 mV) and two Ri levels (10 7 and 10 9  Ohms) was performed. Intermediate Ri levels 10 7 and 10 8  Ohms provided EPG waveforms with the greatest amount of information, because both levels captured similar proportions of R and emf components, as supported by appearance, clarity, and definition of waveforms. Similarly, use of a gold wire loop plus handmade silver glue provided more definition of waveforms than a gold wire loop plus commercial conducting silver paint. Qualitative/observational evidence suggested that AC applied signal caused fewer aberrant behaviors/waveforms than DC applied signal. In the quantitative study, behavioral components of the sharpshooter X wave were the most affected by changes in Ri and voltage level. Because the X wave probably represents X. fastidiosa inoculation behavior, future studies of X. fastidiosa inoculation via EPG will require carefully determined instrument settings. An intermediate Ri level such as 10 8  Ohms with low voltage, AC applied signal, and gold wire loop plus silver glue is recommended as the best electropenetrograph methods to conduct future EPG studies of sharpshooter inoculation behaviors on Xf-resistant and -susceptible grapevine. Copyright © 2018. Published by Elsevier Ltd.

Silver ions are responsible for memory impairment induced by oral administration of silver nanoparticles.

PubMed

Węsierska, M; Dziendzikowska, K; Gromadzka-Ostrowska, J; Dudek, J; Polkowska-Motrenko, H; Audinot, J N; Gutleb, A C; Lankoff, A; Kruszewski, M

2018-06-15

Increasing use of silver nanoparticles (AgNPs) results in increased human exposure. AgNPs are able to cross brain-blood barrier and are a risk factor for the brain. Thus, we hypothesized that AgNPs exposure might affect hippocampal dependent memory, which required cognitive coordination processes. To verify the assumption, in this study we evaluated the effects of orally administered bovine serum albumin (BSA)-coated AgNPs on spatial memory, which engage cognitive coordination processes for on-going stimuli segregation. Rats following 28 days of oral administration with 1 mg/kg (n = 10) or 30 mg/kg (n = 10) BSA-AgNPs or saline, a control groups (n = 10, n = 8), were tested with an active place avoidance task in the Carousel Maze test. The study revealed significant impairment of long- and short-term memory, irrespectively of dose of AgNPs, whereas non-cognitive activity was on a similar level. We found significantly higher content of silver in the hippocampus in comparison to the lateral cortex. No silver was found in the cerebellum and the frontal cortex. The nanoSIMS analysis reveal a weak signal of silver in the hippocampus of AgNPs treated animals that should be attributed to the presence of silver in ionic form rather than AgNPs. Our findings indicate that oral exposure to a low dose AgNPs induces detrimental effect on memory and cognitive coordination processes. The presence of silver ions rather than AgNPs in different brain regions, in particular the hippocampus, suggests crucial role of silver ions in AgNPs-induced impairment of the higher brain functions. Copyright © 2018 Elsevier B.V. All rights reserved.

Assessment of Heavy Metals in Municipal Sewage Sludge: A Case Study of Limpopo Province, South Africa

PubMed Central

Shamuyarira, Kudakwashe K.; Gumbo, Jabulani R.

2014-01-01

Heavy metals in high concentrations can cause health and environmental damage. Nanosilver is an emerging heavy metal which has a bright future of use in many applications. Here we report on the levels of silver and other heavy metals in municipal sewage sludge. Five towns in Limpopo province of South Africa were selected and the sludge from their wastewater treatment plants (WWTPs) was collected and analysed. The acid digested sewage sludge samples were analysed using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) methods. The concentrations of silver found were low, but significant, in the range 0.22 to 21.93 mg/kg dry mass. The highest concentration of silver was found in Louis Trichardt town with a concentration of 21.93 ± 0.38 mg/kg dry mass while the lowest was Thohoyandou with a concentration of 6.13 ± 0.12 mg/kg dry mass. A control sludge sample from a pit latrine had trace levels of silver at 0.22 ± 0.01 mg/kg dry mass. The result showed that silver was indeed present in the wastewater sewage sludge and at present there is no DWAF guideline standard. The average Cd concentration was 3.10 mg/kg dry mass for Polokwane municipality. Polokwane and Louis Trichardt municipalities exhibited high levels of Pb, in excess DWAF guidelines, in sludge at 102.83 and 171.87 mg/kg respectfully. In all the WWTPs the zinc and copper concentrations were in excess of DWAF guidelines. The presence of heavy metals in the sewage sludge in excess of DWAF guidelines presents environmental hazards should the sludge be applied as a soil ameliorant. PMID:24595211

Fiber-optic microsensor array based on fluorescent bulk optode microspheres for the trace analysis of silver ions.

PubMed

Wygladacz, Katarzyna; Radu, Aleksandar; Xu, Chao; Qin, Yu; Bakker, Eric

2005-08-01

An optical microsensor array is described for the rapid analysis of silver ions at low parts per trillion levels. Because the ionophore o-xylylenebis(N,N-diisobutyldithiocarbamate) (Cu-I) was reevaluated and shown to exhibit excellent selectivity for silver ions, ion-selective electrode (ISE) membranes were optimized and found to exhibit the lowest reported detection limit so far (3 x 10(-10) M). A corresponding Ag+-selective fluorescent optical microsensor array for the rapid sensing of trace level Ag+ was then developed. It was fabricated using plasticized PVC-based micrometer-scale fluorescent microspheres that were produced via a sonic particle casting device. They contained 156 mmol/kg Cu-I, 10 mmol/kg 9-(diethylamino)-5-[4-(15-butyl-1,13-dioxo-2,14-dioxanodecyl) phenylimino]benzo[a]phenoxazine (chromoionophore VII, ETH 5418), 2.3 mmol/kg 1,1' '-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (internal reference dye), and 14 mmol/kg sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate and were deposited onto the etched distal end of a 3200-microm-diameter optical fiber bundle. The microarray was characterized by fluorescence spectroscopy in samples containing 10(-12)-10(-8) M AgNO3 at pH 7.4, with selectivity characteristics comparable to the corresponding ISEs. The response time of the microsensor array was found to be less than 15 min for 10(-9) M AgNO3, which is drastically shorter than earlier data on optode films (8 h) and corresponding ISEs (30 min). A detection limit of 4 x 10(-11) M for Ag+ was observed, lower than any previously reported optode or silver-selective ISE. The microsensor array was applied for measurement of free silver levels in buffered pond water samples.

Uptake route and resulting toxicity of silver nanoparticles in Eisenia fetida earthworm exposed through Standard OECD Tests.

PubMed

Garcia-Velasco, Nerea; Gandariasbeitia, Maite; Irizar, Amaia; Soto, Manuel

2016-10-01

Despite the increasing interest in silver nanoparticles toxicity still few works dealt with the hazards of nanosized Ag in soils (either dissolved in pore water or coupled to colloids) although disposal of biosolids in landfills has been reported as the major source of silver nanoparticles in terrestrial environments. Presently, Eisenia fetida was used to assess the toxicity of 5 nm sized PVP-PEI coated silver nanoparticles in soil through the implementation of different exposure media Standard Toxicity Tests (Paper Contact and Artificial Soil -OECD-207- and Reproduction -OECD-222- Tests) together with cellular biomarkers measured in extruded coelomocytes. In order to decipher the mode of action of silver nanoparticles in soil and the uptake routes in earthworms, special attention was given to the Ag accumulation and distribution in tissues. High Ag accumulation rates, weight loss, and mortality due to the disruption of the tegument could be the result of a dermal absorption of Ag ions released from silver nanoparticles (Paper Contact Test). However, autometallography showed metals mainly localized in the digestive tract after Artificial Soil Test, suggesting that Ag uptake occurred mostly through soil ingestion. That is, silver nanoparticles attached to soil colloids seemed to be internalized in earthworms after ingestion of soil and transferred to the digestive gut epithelium where at high doses they have triggered severe effects at different levels of biological complexity.

Water treatment with exceptional virus inactivation using activated carbon modified with silver (Ag) and copper oxide (CuO) nanoparticles.

PubMed

Shimabuku, Quelen Letícia; Arakawa, Flávia Sayuri; Fernandes Silva, Marcela; Ferri Coldebella, Priscila; Ueda-Nakamura, Tânia; Fagundes-Klen, Márcia Regina; Bergamasco, Rosangela

2017-08-01

Continuous flow experiments (450 mL min -1 ) were performed in household filter in order to investigate the removal and/or inactivation of T4 bacteriophage, using granular activated carbon (GAC) modified with silver and/or copper oxide nanoparticles at different concentrations. GAC and modified GAC were characterized by X-ray diffractometry, specific surface area, pore size and volume, pore average diameter, scanning electron microscopy, transmission electron microscopy, zeta potential and atomic absorption spectroscopy. The antiviral activity of the produced porous media was evaluated by passing suspensions of T4 bacteriophage (∼10 5  UFP/mL) through filters. The filtered water was analyzed for the presence of the bacteriophage and the release of silver and copper oxide. The porous media containing silver and copper oxide nanoparticles showed high inactivation capacity, even reaching reductions higher than 3 log. GAC6 (GAC/Ag0.5%Cu1.0%) was effective in the bacteriophage inactivation, reaching 5.53 log reduction. The levels of silver and copper released in filtered water were below the recommended limits (100 ppb for silver and 1000 ppb for copper) in drinking water. From this study, it is possible to conclude that activated carbon modified with silver and copper oxide nanoparticles can be used as a filter for virus removal in the treatment of drinking water.

SERS encoded silver pyramids for attomolar detection of multiplexed disease biomarkers.

PubMed

Xu, Liguang; Yan, Wenjing; Ma, Wei; Kuang, Hua; Wu, Xiaoling; Liu, Liqaing; Zhao, Yuan; Wang, Libing; Xu, Chuanlai

2015-03-11

Three disease biomarkers can simultaneously be detected at the attomolar level because of a novel surface-enhanced Raman scattering (SERS) encoded silver pyramid sensing system. This newly designed pyramidal sensor with well-controlled geometry exhibits highly sensitive, selective, and reproducible SERS signals, and holds promising potential for biodetection applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Silver Coordination Polymers for Prevention of Implant Infection: Thiol Interaction, Impact on Respiratory Chain Enzymes, and Hydroxyl Radical Induction▿ †

PubMed Central

Gordon, Oliver; Vig Slenters, Tünde; Brunetto, Priscilla S.; Villaruz, Amer E.; Sturdevant, Daniel E.; Otto, Michael; Landmann, Regine; Fromm, Katharina M.

2010-01-01

Prosthetic joint replacements are used increasingly to alleviate pain and improve mobility of the progressively older and more obese population. Implant infection occurs in about 5% of patients and entails significant morbidity and high social costs. It is most often caused by staphylococci, which are introduced perioperatively. They are a source of prolonged seeding and difficult to treat due to antibiotic resistance; therefore, infection prevention by prosthesis coating with nonantibiotic-type anti-infective substances is indicated. A renewed interest in topically used silver has fostered development of silver nanoparticles, which, however, present a potential health hazard. Here we present new silver coordination polymer networks with tailored physical and chemical properties as nanostructured coatings on metallic implant substrates. These compounds exhibited strong biofilm sugar-independent bactericidal activity on in vitro-grown biofilms and prevented murine Staphylococcus epidermidis implant infection in vivo with slow release of silver ions and limited transient leukocyte cytotoxicity. Furthermore, we describe the biochemical and molecular mechanisms of silver ion action by gene screening and by targeting cell metabolism of S. epidermidis at different levels. We demonstrate that silver ions inactivate enzymes by binding sulfhydryl (thiol) groups in amino acids and promote the release of iron with subsequent hydroxyl radical formation by an indirect mechanism likely mediated by reactive oxygen species. This is the first report investigating the global metabolic effects of silver in the context of a therapeutic application. We anticipate that the compounds presented here open a new treatment field with a high medical impact. PMID:20660682

Silver coated aluminium microrods as highly colloidal stable SERS platforms.

PubMed

Pazos-Perez, Nicolas; Borke, Tina; Andreeva, Daria V; Alvarez-Puebla, Ramon A

2011-08-01

We report on the fabrication of a novel material with the ability to remain in solution even under the very demanding conditions required for structural and dynamic characterization of biomacromolecule assays. This stability is provided by the increase in surface area of a low density material (aluminium) natively coated with a very hydrophilic surface composed of aluminium oxide (Al(2)O(3)) and metallic silver nanoparticles. Additionally, due to the dense collection of active hot spots on their surface, this material offers higher levels of SERS intensity as compared with the same free and aggregated silver nanoparticles. This journal is © The Royal Society of Chemistry 2011

Strong plasmonic enhancement of single molecule photostability in silver dimer optical antennas

NASA Astrophysics Data System (ADS)

Kaminska, Izabela; Vietz, Carolin; Cuartero-González, Álvaro; Tinnefeld, Philip; Fernández-Domínguez, Antonio I.; Acuna, Guillermo P.

2018-02-01

Photobleaching is an effect terminating the photon output of fluorophores, limiting the duration of fluorescence-based experiments. Plasmonic nanoparticles (NPs) can increase the overall fluorophore photostability through an enhancement of the radiative rate. In this work, we use the DNA origami technique to arrange a single fluorophore in the 12-nm gap of a silver NP dimer and study the number of emitted photons at the single molecule level. Our findings yielded a 30× enhancement in the average number of photons emitted before photobleaching. Numerical simulations are employed to rationalize our results. They reveal the effect of silver oxidation on decreasing the radiative rate enhancement.

Adsorption mechanism of physiologically active L-phenylalanine phosphonodipeptide analogues: Comparison of colloidal silver and macroscopic silver substrates

NASA Astrophysics Data System (ADS)

Podstawka, E.; Kudelski, A.; Proniewicz, L. M.

2007-11-01

Here we present SERS spectra of several L-phenylalanine (Phe) phosphonodipeptides, i.e., L-Phe- L-Ala-PO 3H 2 ( MD1), L-Phe- L-Va L-PO 3H 2 ( MD2), L-Phe-β-Ala-CH(OH)-PO 3H 2 ( MD3), L-Phe- L-Ala-CH(OH)-PO 3H 2 ( MD4), L-Ala-(3,4-dimethoxy)- L-Phe-PO 3H 2 ( MD5), and L-Ala-(3,4-dimethoxy)-(des-CH 2)- L-Phe-PO 3H 2 ( MD6), immobilized on electrochemically roughened silver electrodes. These spectra are analyzed by theoretical calculations using density functional theory (DFT) at the B3LYP level with 6-31++G∗∗ basis set. In addition, these spectra are compared with SERS spectra of these species adsorbed on a colloidal silver surface. We showed that on the macroscopic silver substrate, the Phe aromatic ring of MD3 and MD4 is oriented vertically, while for MD1 it almost "stands up" on this surface. In the other three cases, the Phe ring adopts a tilted orientation in regard to the substrate. We also find that the phosphonate (-PO32-), methyl/methane, or dimethoxy groups of MD1, MD2, MD3, MD5, and MD6 are involved in the interaction of these phosphonodipeptides with the electrochemically roughened surface. This phenomenon is clearly seen for -CH 2-/-CH 3/-OCH 3 moieties as well as for the PO32- group that adsorbs on the macroscopic silver substrates mainly via the P dbnd O fragment. We also showed that MD4 binds to the macroscopic silver substrate through the hydroxyl, amine, and phosphonate groups, while the methylene/methane moieties are remote from this surface. We found that studied phosphonodipeptides often adsorb differently on the macroscopic silver substrate and on the colloidal silver nanoparticles. For example, MD1 adopts an almost vertical orientation on the electrochemically roughened silver substrate and is tilted or close to flat on the silver nanoparticles.

Non-hazardous anticancerous and antibacterial colloidal 'green' silver nanoparticles.

PubMed

Barua, Shaswat; Konwarh, Rocktotpal; Bhattacharya, Satya Sundar; Das, Pallabi; Devi, K Sanjana P; Maiti, Tapas K; Mandal, Manabendra; Karak, Niranjan

2013-05-01

Poly(ethylene glycol) stabilized colloidal silver nanoparticles were prepared using the reductive potency of the aqueous extract of Thuja occidentalis leaves under ambient conditions. The nanoparticles were well dispersed within a narrow size spectrum (7-14 nm) and displayed characteristic surface plasmon resonance peak at around 420 nm and Bragg's reflection planes of fcc structure. MTT assay revealed the dose-dependent cytocompatibility and toxicity of the nanoparticles with the L929 normal cell line. On the other hand, the antiproliferative action of the nanoparticles was evaluated on HeLa cell (cancerous cells) line. Fluorescence and phase contrast microscopic imaging indicated the appearance of multinucleate stages with aggregation and nuclear membrane disruption of the HeLa cells post treatment with the nanoparticles. The interaction at the prokaryotic level was also assessed via differential antibacterial efficacy against Staphylococcus aureus (MTCC 3160) and Escherichia coli (MTCC 40). Under these perspectives, it is also necessary to observe the environmental impact of the prepared silver nanoparticles. Hence, the dose dependent toxicity of silver nanoparticles was evaluated upon the earthworm species Eisenia fetida. Neither the survival nor the reproduction was affected by the addition of silver nanoparticles up to 1000 ppm. Thus these 'green' silver nanoparticles have promising potential as future materials. Copyright © 2012 Elsevier B.V. All rights reserved.

Mycosynthesis of silver nanoparticles using extract of endophytic fungi, Penicillium species of Glycosmis mauritiana, and its antioxidant, antimicrobial, anti-inflammatory and tyrokinase inhibitory activity

NASA Astrophysics Data System (ADS)

Govindappa, M.; Farheen, H.; Chandrappa, C. P.; Channabasava; Rai, Ravishankar V.; Raghavendra, Vinay B.

2016-09-01

Silver nanoparticles were synthesized using endophytic fungal species, Penicillium species from Glycosmis mautitiana. Phytochemicals, namely tannins, saponins, terpenoids and flavonoids, were identified in Penicillium species extracts, and act as agents of reducing and capping in the conversion of silver nanoparticles into nanoparticles. Using SEM, UV-spectroscopy and XRD, the Penicillium species silver nanoparticles (PsAgNPs) were characterized. The PsAgNPs are shown to be strong antioxidants (DDPH and FRAP), have demonstrated anti-inflammatory properties by three different methods in vitro and strongly inhibited the activity of xanthine oxidase, lipoxygenase and tyrosine kinase. E. coli and P. aeruginosa bacterial species were strongly inhibited by PsAgNPs activity at maximum levels and SEM picture of P. aeruginosa confirms these effects and that they were shrunken due to the toxic effect of PsAgNPs.

Antifungal Effects of Silver Nanoparticles (AgNPs) against Various Plant Pathogenic Fungi.

PubMed

Kim, Sang Woo; Jung, Jin Hee; Lamsal, Kabir; Kim, Yun Seok; Min, Ji Seon; Lee, Youn Su

2012-03-01

This research is concerned with the fungicidal properties of nano-size silver colloidal solution used as an agent for antifungal treatment of various plant pathogens. We used WA-CV-WA13B, WA-AT-WB13R, and WA-PR-WB13R silver nanoparticles (AgNPs) at concentrations of 10, 25, 50, and 100 ppm. Eighteen different plant pathogenic fungi were treated with these AgNPs on potato dextrose agar (PDA), malt extract agar, and corn meal agar plates. We calculated fungal inhibition in order to evaluate the antifungal efficacy of silver nanoparticles against pathogens. The results indicated that AgNPs possess antifungal properties against these plant pathogens at various levels. Treatment with WA-CV-WB13R AgNPs resulted in maximum inhibition of most fungi. Results also showed that the most significant inhibition of plant pathogenic fungi was observed on PDA and 100 ppm of AgNPs.

SERS-active silver nanoparticle aggregates produced in high-iron float glass by ion exchange process

NASA Astrophysics Data System (ADS)

Karvonen, L.; Chen, Y.; Säynätjoki, A.; Taiviola, K.; Tervonen, A.; Honkanen, S.

2011-11-01

Silver nanoparticles were produced in iron containing float glasses by silver-sodium ion exchange and post-annealing. In particular, the effect of the concentration and the oxidation state of iron in the host glass on the nanoparticle formation was studied. After the nanoparticle fabrication process, the samples were characterized by optical absorption measurements. The samples were etched to expose nanoparticle aggregates on the surface, which were studied by optical microscopy and scanning electron microscopy. The SERS-activity of these glass samples was demonstrated and compared using a dye molecule Rhodamine 6G (R6G) as an analyte. The importance of the iron oxidation level for reduction process is discussed. The glass with high concentration of Fe 2+ ions was found to be superior in SERS applications of silver nanoparticles. The optimal surface features in terms of SERS enhancement are also discussed.

Antibacterial Activity of Silver-Graphene Quantum Dots Nanocomposites Against Gram-Positive and Gram-Negative Bacteria

NASA Technical Reports Server (NTRS)

Makarov, Vladimir (Inventor); Habiba, Khaled (Inventor); Weiner, Brad R (Inventor); Morell, Gerardo (Inventor)

2018-01-01

The invention provides a composite of silver nanoparticles decorated with graphene quantum dots (Ag-GQDs) using pulsed laser synthesis. The nanocomposites were functionalized with polyethylene glycol (PEG). A concentration of 150 .mu.g/mL of Ag-GQDs, a non-toxic level for human cells, exhibits strong antibacterial activity against both Gram-Positive and Gram-Negative Bacteria.

Silver nanoparticles administered to chicken affect VEGFA and FGF2 gene expression in breast muscle and heart

NASA Astrophysics Data System (ADS)

Hotowy, Anna; Sawosz, Ewa; Pineda, Lane; Sawosz, Filip; Grodzik, Marta; Chwalibog, André

2012-07-01

Nanoparticles of colloidal silver (AgNano) can influence gene expression. Concerning trials of AgNano application in poultry nutrition, it is useful to reveal whether they affect the expression of genes crucial for bird development. AgNano were administered to broiler chickens as a water solution in two concentrations (10 and 20 ppm). After dissection of the birds, breast muscles and hearts were collected. Gene expression of FGF2 and VEGFA on the mRNA and protein levels were evaluated using quantitative polymerase chain reaction and enzyme-linked immunosorbent assay methods. The results for gene expression in the breast muscle revealed changes on the mRNA level ( FGF2 was up-regulated, P < 0.05) but not on the protein level. In the heart, 20 ppm of silver nanoparticles in drinking water increased the expression of VEGFA ( P < 0.05), at the same time decreasing FGF2 expression both on the transcriptional and translational levels. Changes in the expression of these genes may lead to histological changes, but this needs to be proven using histological and immunohistochemical examination of tissues. In general, we showed that AgNano application in poultry feeding influences the expression of FGF2 and VEGFA genes on the mRNA and protein levels in growing chicken.

Effects of water hardness on the physiological responses to chronic waterborne silver exposure in early life stages of rainbow trout (Oncorhynchus mykiss).

PubMed

Morgan, T P; Guadagnolo, C M; Grosell, M; Wood, C M

2005-09-30

Early life stages of rainbow trout were exposed to 0, 0.1 and 1 microg/L Ag (as AgNO(3)) in very soft water (2mg/L CaCO(3)), moderately hard water (150 mg/L CaCO(3)) and hard water (400mg/L CaCO(3)) of low dissolved organic carbon concentration (0.5mg C/L) from fertilization to swim-up (64 days) under flow-through conditions, and monitored for whole embryo/larval silver accumulation, Na(+) and Cl(-) concentrations, Na(+) uptake and Na(+)K(+)-ATPase activity. The objective of the study was to investigate potential protective effects of water hardness on the physiological responses to chronic silver exposure. In the absence of silver, there was little effect of hardness on the ionoregulatory parameters studied, though higher hardness did improve survival post-hatch. At all three water hardness levels, whole embryo/larval Na(+) uptake was low and relatively constant prior to 50% hatch, but dramatically increased following 50% hatch, whereas Na(+)K(+)-ATPase activity steadily increased over development. Whole embryo/larval Na(+) and Cl(-) concentrations were low and constant prior to 50% hatch, but following 50% hatch Na(+) concentration increased, while Cl(-) concentration decreased. Following 50% hatch, exposure to 0.1 and 1 microg/L Ag resulted in a decrease in whole embryo/larval Na(+) concentration, Cl(-) concentration, Na(+) uptake and Na(+)K(+)-ATPase activity, indicating that the mechanism of chronic silver toxicity involves an ionoregulatory disturbance, and is similar to the mechanism of acute silver toxicity. An increase in water hardness reduced or eliminated the effect of silver on these parameters while enhancing survival, suggesting that the nature of the protective effect of hardness involves effects on the ionoregulatory disturbance associated with silver exposure. An increase in water hardness did not fully protect against the accumulation of silver associated with silver exposure. These results suggest that it may be possible to model chronic silver toxicity using a biotic ligand type model, and that a physiologically based model may be more appropriate because Na(+)K(+)-ATPase activity or Na(+) uptake is an endpoint for prediction rather than whole embryo or larval silver accumulation.

Geochemical results of a hydrothermally altered area at Baker Creek, Blaine County, Idaho

USGS Publications Warehouse

Erdman, James A.; Moye, Falma J.; Theobald, Paul K.; McCafferty, Anne E.; Larsen, Richard K.

2001-01-01

The area immediately east of Baker Creek, Blaine County, Idaho, is underlain by a thick section of mafic to intermediate lava flows of the Eocene Challis Volcanic Group. Widespread propylitic alteration surrounds a zone of argillic alteration and an inner core of phyllic alteration. Silicified breccia is present along an east-trending fault within the zone of phyllic alteration. As part of a reconnaissance geochemical survey, soils and plants were sampled. Several species of plants (Douglas-fir [ Pseudotsuga menziesii ], mountain big sagebrush [ Artemisia tridentata ssp. vaseyana ], and elk sedge [ Carex geyerii ]) were collected from 10 upland localities and stream sediments, panned concentrates, and aquatic mosses were collected from 16 drainage basin localities all of which were generally within the area of alteration. Geochemical results yielded anomalous concentrations of molybenum, zinc, silver, and lead in at least half of the seven different sample media and of gold, thallium, arsenic, antimony, manganese, boron, cadmium, bismuth, copper, and beryllium in from one to four of the various media. Part of this suite of elements? silver, gold, arsenic, antimony, thallium, and manganese? suggests that the mineralization in the area is epithermal. Barite and pyrite (commonly botryoidal-framboidal) are widespread throughout the area sampled. Visible gold and pyromorphite (a secondary lead mineral) were identified in only one small drainage basin, but high levels of gold were detected in aquatic mosses over a larger area. Data from the upland and stream sampling indicate two possible mineralized areas. The first mineralized area was identified by a grab sample from an outcrop of quartz stockwork that contained 50 ppb Au, 1.5 ppm Ag, and 50 ppm Mo. Although the soil and plant species that were sampled in the area indicated mineralized bedrock, the Douglas-fir samples were the best indicators of the silver anomaly. The second possible mineralized area centers on the fault-controlled silicified breccia that is most likely the source of anomalous silver and molybdenum levels identified in the soils; silver, molybdenum, and manganese in stream sediments; thallium in Douglas-fir; bismuth and silver in concentrates; and gold, silver, arsenic, antimony, and molybdenum and lead in aquatic mosses. An interpretation of regional aeromagnetic data delineated the subsurface extent of shallow, steeply dipping magnetic sources inferred to be shallower parts of an Eocene batholith thought to underlie much of the Baker Creek area. The Eocene intrusive event(s) may have served as the heat source(s) that caused the hydrothermal alteration. Examination of core from a 1,530-ft-deep (466 m) hole drilled in 1982 confirmed a bedrock source for the anomalous silver and base-metal suite at the quartz stockwork location, and indicated subeconomic levels of molybdenum.

Antibacterial activity of plastics coated with silver-doped organic-inorganic hybrid coatings prepared by sol-gel processes.

PubMed

Marini, M; De Niederhausern, S; Iseppi, R; Bondi, M; Sabia, C; Toselli, M; Pilati, F

2007-04-01

Silver-doped organic-inorganic hybrid coatings were prepared starting from tetraethoxysilane- and triethoxysilane-terminated poly(ethylene glycol)-block-polyethylene by the sol-gel process. They were applied as a thin layer (0.6-1.1 microm) to polyethylene (PE) and poly(vinyl chloride) (PVC) films and the antibacterial activity of the coated films was tested against Gram-negative (Escherichia coli ATCC 25922) and Gram-positive (Staphylococcus aureus ATCC 6538) bacteria. The effect of several factors (such as organic-inorganic ratio, type of catalyst, time of post-curing, silver ion concentration, etc.) was investigated. Measurements at different contact times showed a rapid decrease of the viable count for both tested strains. The highest antibacterial activity [more than 6 log reduction within 6 h starting from 106 colony-forming units (cfu) mL-1] was obtained for samples with an organic-inorganic weight ratio of 80:20 and 5 wt % silver salt with respect to the coating. For the coatings prepared by an acid-catalyzed process, a high level of permanence of the antibacterial activity of the coated films was demonstrated by repeatedly washing the samples in warm water or by immersion in physiological saline solution at 37 degrees C for 3 days. The release of silver ions per square meter of coating is very similar to that previously observed for polyamides filled with metallic silver nanoparticles; however, when compared on the basis of Ag content, the concentration of silver ions released from the coating is much higher than that released from 1 mm thick specimens of polyamide (PA) filled with silver nanoparticles. Transparency and good adhesion of the coating to PE and PVC plastic substrates without any previous surface treatment are further interesting features.

Synthesis and applications of novel silver nanoparticle structures

NASA Astrophysics Data System (ADS)

Dukes, Kyle

The field of nanotechnology is rapidly expanding across disciplines as each new development is realized. New exciting technologies are being driven by advances in the application of nanotechnology; including biochemical, optical, and semiconductors research. This thesis will focus on the use of silver nanoparticles as optical labels on cells, methods of forming different small structures of silver nanoparticles, as well as the use of silver nanoparticles in the development of a photovoltaic cell. Silver nanoparticles have been modified with self-assembled monolayers of hydroxyl-terminated long chain thiols and encapsulated with a silica shell. The resulting core-shell nanoparticles were used as optical labels for cell analysis using flow cytometry and microscopy. The excitation of plasmon resonances in nanoparticles results in strong depolarized scattering of visible light permitting detection at the single nanoparticle level. The nanoparticles were modified with neutravidin via epoxide-azide coupling chemistry and biotinylated antibodies targeting cell surface receptors were bound to the nanoparticle surface. The nanoparticle labels exhibited long-term stability under physiological conditions without aggregation or silver ion leaching. Labeled cells exhibited two orders of magnitude enhancement of the scattering intensity compared to unlabeled cells. Dimers of silver nanoparticles have been fabricated by first immobilizing a monolayer of single silver nanoparticles onto poly(4-vinylpyridine) covered glass slides. The monolayer was then exposed to adenine, which has two amines which will bind to silver. The nanoparticle monolayer, now modified with adenine, is exposed to a second suspension of nanoparticles which will bind with the amine modified monolayer. Finally, a thin silica shell is formed about the structure via solgel chemistry to prevent dissolution or aggregation upon sonication/striping. Circular arrays of silver nanoparticels are developed using a template base self assembly. A 1.5 micron silica sphere is bound to poly(4-vinylpyridine) coated glass and used as a template. a mask of silica monoxide is vacuum deposited atop the spheres/glass leaving a ring just below the sphere untouched and able to bind silver nanoparticles. Optical microscopy reveal interesting results under depolarized light conditions, but ultimate structural analysis has proven elusive. Semiconducting p-type cuprous oxide was electrochemically deposited on both silver and indium tin oxide electrodes. Silver nanoparticles were incorporated into the architecture either atop the cuprous oxide or sandwiched between cuprous oxide and n-type material. Increases in photocurrent were observed in both cases and further work must be conducted to optimize a solid state device for photovoltaic applications.

Phytotoxicity, accumulation and transport of silver nanoparticles by Arabidopsis thaliana.

PubMed

Geisler-Lee, Jane; Wang, Qiang; Yao, Ying; Zhang, Wen; Geisler, Matt; Li, Kungang; Huang, Ying; Chen, Yongsheng; Kolmakov, Andrei; Ma, Xingmao

2013-05-01

The widespread availability of nano-enabled products in the global market may lead to the release of a substantial amount of engineered nanoparticles in the environment, which frequently display drastically different physiochemical properties than their bulk counterparts. The purpose of the study was to evaluate the impact of citrate-stabilised silver nanoparticles (AgNPs) on the plant Arabidopsis thaliana at three levels, physiological phytotoxicity, cellular accumulation and subcellular transport of AgNPs. The monodisperse AgNPs of three different sizes (20, 40 and 80 nm) aggregated into much larger sizes after mixing with quarter-strength Hoagland solution and became polydisperse. Immersion in AgNP suspension inhibited seedling root elongation and demonstrated a linear dose-response relationship within the tested concentration range. The phytotoxic effect of AgNPs could not be fully explained by the released silver ions. Plants exposed to AgNP suspensions bioaccumulated higher silver content than plants exposed to AgNO3 solutions (Ag(+) representative), indicating AgNP uptake by plants. AgNP toxicity was size and concentration dependent. AgNPs accumulated progressively in this sequence: border cells, root cap, columella and columella initials. AgNPs were apoplastically transported in the cell wall and found aggregated at plasmodesmata. In all the three levels studied, AgNP impacts differed from equivalent dosages of AgNO3.

Effect of Kimchi Fermentation on Oxalate Levels in Silver Beet (Beta vulgaris var. cicla)

PubMed Central

Wadamori, Yukiko; Vanhanen, Leo; Savage, Geoffrey P.

2014-01-01

Total, soluble and insoluble oxalates were extracted and analyzed by high performance liquid chromatography (HPLC) following the preparation of kimchi using silver beet (Beta vulgaris var. cicla) stems and leaves. As silver beet contains high oxalate concentrations and consumption of high levels can cause the development of kidney stones in some people, the reduction of oxalate during preparation and fermentation of kimchi was investigated. The silver beet stems and leaves were soaked in a 10% brine solution for 11 h and then washed in cold tap water. The total, soluble and insoluble oxalate contents of the silver beet leaves were reduced by soaking in brine, from 4275.81 ± 165.48 mg/100 g to 3709.49 ± 216.51 mg/100 g fresh weight (FW). Fermenting the kimchi for 5 days at 19.3 ± 0.8 °C in 5 L ceramic jars with a water airtight seal resulted in a mean 38.50% reduction in total oxalate content and a mean 22.86% reduction in soluble oxalates. The total calcium content was essentially the same before and after the fermentation of the kimchi (mean 296.1 mg/100 g FW). The study showed that fermentation of kimchi significantly (p < 0.05) reduced the total oxalate concentration in the initial mix from 609.32 ± 15.69 to 374.71 ± 7.94 mg/100 g FW in the final mix which led to a 72.3% reduction in the amount of calcium bound to insoluble oxalate. PMID:28234318

Responsiveness of cats (Felidae) to silver vine (Actinidia polygama), Tatarian honeysuckle (Lonicera tatarica), valerian (Valeriana officinalis) and catnip (Nepeta cataria).

PubMed

Bol, Sebastiaan; Caspers, Jana; Buckingham, Lauren; Anderson-Shelton, Gail Denise; Ridgway, Carrie; Buffington, C A Tony; Schulz, Stefan; Bunnik, Evelien M

2017-03-16

Olfactory stimulation is an often overlooked method of environmental enrichment for cats in captivity. The best known example of olfactory enrichment is the use of catnip, a plant that can cause an apparently euphoric reaction in domestic cats and most of the Pantherinae. It has long been known that some domestic cats and most tigers do not respond to catnip. Although many anecdotes exist of other plants with similar effects, data are lacking about the number of cats that respond to these plants, and if cats that do not respond to catnip respond to any of them. Furthermore, much is still unknown about which chemicals in these plants cause this response. We tested catnip, silver vine, Tatarian honeysuckle and valerian root on 100 domestic cats and observed their response. Each cat was offered all four plant materials and a control, multiple times. Catnip and silver vine also were offered to nine tigers. The plant materials were analyzed by gas chromatography coupled with mass spectrometry to quantify concentrations of compounds believed to exert stimulating effects on cats. Nearly all domestic cats responded positively to olfactory enrichment. In agreement with previous studies, one out of every three cats did not respond to catnip. Almost 80% of the domestic cats responded to silver vine and about 50% to Tatarian honeysuckle and valerian root. Although cats predominantly responded to fruit galls of the silver vine plant, some also responded positively to its wood. Of the cats that did not respond to catnip, almost 75% did respond to silver vine and about one out of three to Tatarian honeysuckle. Unlike domestic cats, tigers were either not interested in silver vine or responded disapprovingly. The amount of nepetalactone was highest in catnip and only present at marginal levels in the other plants. Silver vine contained the highest concentrations of all other compounds tested. Olfactory enrichment for cats may have great potential. Silver vine powder from dried fruit galls and catnip were most popular among domestic cats. Silver vine and Tatarian honeysuckle appear to be good alternatives to catnip for domestic cats that do not respond to catnip.

Tailoring Plasmonic Enhanced Upconversion in Single NaYF4:Yb3+/Er3+ Nanocrystals

NASA Astrophysics Data System (ADS)

Wang, Ya-Lan; Mohammadi Estakhri, Nasim; Johnson, Amber; Li, Hai-Yang; Xu, Li-Xiang; Zhang, Zhenyu; Alù, Andrea; Wang, Qu-Quan; Shih, Chih-Kang (Ken)

2015-05-01

By using silver nanoplatelets with a widely tunable localized surface plasmon resonance (LSPR), and their corresponding local field enhancement, here we show large manipulation of plasmonic enhanced upconversion in NaYF4:Yb3+/Er3+ nanocrystals at the single particle level. In particular, we show that when the plasmonic resonance of silver nanolplatelets is tuned to 656 nm, matching the emission wavelength, an upconversion enhancement factor ~5 is obtained. However, when the plasmonic resonance is tuned to 980 nm, matching the nanocrystal absorption wavelength, we achieve an enhancement factor of ~22 folds. The precise geometric arrangement between fluorescent nanoparticles and silver nanoplatelets allows us to make, for the first time, a comparative analysis between experimental results and numerical simulations, yielding a quantitative agreement at the single particle level. Such a comparison lays the foundations for a rational design of hybrid metal-fluorescent nanocrystals to harness the upconversion enhancement for biosensing and light harvesting applications.

Colloidal complexed silver and silver nanoparticles in extrapallial fluid of Mytilus edulis.

PubMed

Zuykov, Michael; Pelletier, Emilien; Demers, Serge

2011-02-01

Metal transport in mollusk extrapallial fluid (EPF) that acts as a "bridge" between soft tissues and shell has surprisingly received little attention until now. Using ultrafiltration and radiotracer techniques we determined silver concentrations and speciation in the EPF of the blue mussel Mytilus edulis after short-term uptake and depuration laboratory experiments. Radiolabelled silver ((¹¹⁰m)Ag) was used in dissolved or nanoparticulate phases (AgNPs < 40 nm), with a similar low Ag concentration (total radioactive and cold Ag ~0.7 μg/L) in a way that mussels could uptake radiotracers only from seawater. Our results indicated that silver nanoparticles were transported to the EPF of blue mussels at a level similar to the Ag ionic form. Bulk activity of radiolabelled silver in the EPF represented only up to 7% of the bulk activity measured in the whole mussels. The EPF extracted from mussels exposed to both treatments exhibited an Ag colloidal complexed form based on EPF ultrafiltration through a 3 kDa filter. This original study brings new insights to internal circulation of nanoparticles in living organisms and contributes to the international effort in studying the potential impacts of engineered nanomaterials on marine bivalves which play an essential role in coastal ecosystems, and are important contributors to human food supply from the sea. © 2010 Elsevier Ltd. All rights reserved.

Determination of acetylsalicylic acid in commercial tablets by SERS using silver nanoparticle-coated filter paper

NASA Astrophysics Data System (ADS)

Sallum, Loriz Francisco; Soares, Frederico Luis Felipe; Ardila, Jorge Armando; Carneiro, Renato Lajarim

2014-12-01

In this work, filter paper was used as a low cost substrate for silver nanoparticles in order to perform the detection and quantification of acetylsalicylic acid by SERS in a commercial tablet. The reaction conditions were 150 mM of ammonium hydroxide, 50 mM of silver nitrate, 500 mM of glucose, 12 min of the reaction time, 45 °C temperature, pretreatment with ammonium hydroxide and quantitative filter paper (1-2 μm). The average size of silver nanoparticles deposited on the paper substrate was 180 nm. Adsorption time of acetylsalicylic acid on the surface of the silver-coated filter paper was studied and an adsorption time of 80 min was used to build the analytical curve. It was possible to obtain a calibration curve with good precision with a coefficient of determination of 0.933. The method proposed in this work was capable to quantify acetylsalicylic acid in commercial tablets, at low concentration levels, with relative error of 2.06% compared to the HPLC. The preparation of filter paper coated with silver nanoparticles using Tollen's reagent presents several advantages such as low cost of synthesis, support and reagents; minimum amount of residuals, which are easily treated, despite the SERS spectroscopy presenting fast analysis, with low sample preparation and low amount of reactants as in HPLC analysis.

Biodirected synthesis of Miconazole-conjugated bacterial silver nanoparticles and their application as antifungal agents and drug delivery vehicles.

PubMed

Kumar, C Ganesh; Poornachandra, Y

2015-01-01

The recent strategy to improve the efficacy of drugs is to combine them with metal nanoparticles for the control of microbial infections. Considering this fact, we developed a low cost and eco-friendly method for silver nanoparticles synthesis using the cell free supernatant of Delftia sp. strain KCM-006 and their application as antifungal agents and as a drug carrier. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis revealed the formation of spherical and monodispersed silver nanoparticles with an average size of 9.8 nm. The synthesized nanoparticles were found to be photoluminescent, highly stable and crystalline in nature having a zeta potential of -31 mV. The silver nanoparticles exhibited very good antifungal activity against various pathogenic Candida strains. Furthermore, the efficacy of nanoparticles was increased by conjugating the antifungal drug Miconazole to silver nanoparticles which exhibited significant fungicidal activity, inhibition of ergosterol biosynthesis and biofilm inhibition by increasing ROS levels. In addition, the cell viability and immunocytochemistry analysis against different normal cell lines including Chinese hamster ovary cells (CHO), human lung cell line (MRC5) and human vascular endothelial cells (HUVEC) demonstrated that these nanoparticles were non-toxic up to a concentration of 20 μM. In conclusion, these results suggest that the synthesized nanoparticles find application as both antifungal agents and drug delivery vehicles. This is a first report on the preparation of silver nanoparticles using culture supernatant from Delftia sp. and also on the conjugation of Miconazole, an antifungal drug, to the bacterial silver nanoparticles. Copyright © 2014 Elsevier B.V. All rights reserved.

Silver fir and Douglas fir are more tolerant to extreme droughts than Norway spruce in south-western Germany.

PubMed

Vitali, Valentina; Büntgen, Ulf; Bauhus, Jürgen

2017-12-01

Improving our understanding of the potential of forest adaptation is an urgent task in the light of predicted climate change. Long-term alternatives for susceptible yet economically important tree species such as Norway spruce (Picea abies) are required, if the frequency and intensity of summer droughts will continue to increase. Although Silver fir (Abies alba) and Douglas fir (Pseudotsuga menziesii) have both been described as drought-tolerant species, our understanding of their growth responses to drought extremes is still limited. Here, we use a dendroecological approach to assess the resistance, resilience, and recovery of these important central Europe to conifer species the exceptional droughts in 1976 and 2003. A total of 270 trees per species were sampled in 18 managed mixed-species stands along an altitudinal gradient (400-1200 m a.s.l.) at the western slopes of the southern and central Black Forest in southwest Germany. While radial growth in all species responded similarly to the 1976 drought, Norway spruce was least resistant and resilient to the 2003 summer drought. Silver fir showed the overall highest resistance to drought, similarly to Douglas fir, which exhibited the widest growth rings. Silver fir trees from lower elevations were more drought prone than trees at higher elevations. Douglas fir and Norway spruce, however, revealed lower drought resilience at higher altitudes. Although the 1976 and 2003 drought extremes were quite different, Douglas fir maintained consistently the highest radial growth. Although our study did not examine population-level responses, it clearly indicates that Silver fir and Douglas fir are generally more resistant and resilient to previous drought extremes and are therefore suitable alternatives to Norway spruce; Silver fir more so at higher altitudes. Cultivating these species instead of Norway spruce will contribute to maintaining a high level of productivity across many Central European mountain forests under future climate change. © 2017 John Wiley & Sons Ltd.

Sorption, Solubility, Bond Strength and Hardness of Denture Soft Lining Incorporated with Silver Nanoparticles

PubMed Central

Chladek, Grzegorz; Kasperski, Jacek; Barszczewska-Rybarek, Izabela; Żmudzki, Jarosław

2013-01-01

The colonization of denture soft lining material by oral fungi can result in infections and stomatitis of oral tissues. In this study, 0 ppm to 200 ppm of silver nanoparticles was incorporated as an antimicrobial agent into composites to reduce the microbial colonization of lining materials. The effect of silver nanoparticle incorporation into a soft lining material on the sorption, solubility, hardness (on the Shore A scale) and tensile bond strength of the composites was investigated. The data were statistically analyzed using two-way ANOVA and Newman-Keuls post hoc tests or the chi-square Pearson test at the p < 0.05 level. An increase in the nanosilver concentration resulted in a decrease in hardness, an increase in sorption and solubility, a decrease in bond strength and a change in the failure type of the samples. The best combination of bond strength, sorption, solubility and hardness with antifungal efficacy was achieved for silver nanoparticle concentrations ranging from 20 ppm to 40 ppm. These composites did not show properties worse than those of the material without silver nanoparticles and exhibited enhanced in vitro antifungal efficiency. PMID:23271371

Flow injection method for the determination of silver concentration in drinking water for spacecrafts.

PubMed

Bruzzoniti, Maria Concetta; Kobylinska, Dorota Korte; Franko, Mladen; Sarzanini, Corrado

2010-04-14

A flow injection method has been developed for determination of silver. The method is based on a reduction reaction with sodium borohydride which leads to the formation of a colloidal species which is monitored at a wavelength of 390 nm. The reaction variables flow rate, sodium borohydride concentration and pH, which affect sensitivity, were investigated and their effects were established using a two-levels, three-factor experimental design. Further optimization of manifold variables (reaction coil and injection volume) allowed us to determine silver in the range 0.050-5.0 mg L(-1) with a minimum detectable concentration of 0.050 mg L(-1). Silver is added, as biocide, to drinking water for spacecrafts. The chemical species of silver, present in this kind of sample, were characterized by a procedure based on the selective retention of Ag(+) onto a 2.2.2. cryptand based substrate followed by determination of the non-bound and bound (after elution) Ag(+) by the FIA method. The method optimized was applied to a drinking water sample provided for the launch with the Automated Transfer Vehicle (ATV) module Jule Verne to the International Space Station (March 9, 2008). Copyright 2010 Elsevier B.V. All rights reserved.

Complexes of DNA bases and Watson-Crick base pairs interaction with neutral silver Agn (n = 8, 10, 12) clusters: a DFT and TDDFT study.

PubMed

Srivastava, Ruby

2018-03-01

We study the binding of the neutral Ag n (n = 8, 10, 12) to the DNA base-adenine (A), guanine (G) and Watson-Crick -adenine-thymine, guanine-cytosine pairs. Geometries of complexes were optimized at the DFT level using the hybrid B3LYP functional. LANL2DZ effective core potential was used for silver and 6-31 + G ** was used for all other atoms. NBO charges were analyzed using the Natural population analysis. The absorption properties of Ag n -A,G/WC complexes were also studied using time-dependent density functional theory. The absorption spectra for these complexes show wavelength in the visible region. It was revealed that silver clusters interact more strongly with WC pairs than with isolated DNA complexes. Furthermore, it was found that the electronic charge transferred from silver to isolated DNA clusters are less than the electronic charge transferred from silver to the Ag n -WC complexes. The vertical ionization potential, vertical electron affinity, hardness, and electrophilicity index of Ag n -DNA/WC complexes have also been discussed.

Sensing the facet orientation in silver nano-plates using scanning Kelvin probe microscopy in air

NASA Astrophysics Data System (ADS)

Abdellatif, M. H.; Salerno, M.; Polovitsyn, Anatolii; Marras, Sergio; De Angelis, Francesco

2017-05-01

The work function of nano-materials is important for a full characterization of their electronic properties. Because the band alignment, band bending and electronic noise are very sensitive to work function fluctuations, the dependence of the work function of nano-scale crystals on facet orientation can be a critical issue in optimizing optoelectronic devices based on these materials. We used scanning Kelvin probe microscopy to assess the local work function on samples of silver nano-plates at sub-micrometric spatial resolution. With the appropriate choice of the substrate and based on statistical analysis, it was possible to distinguish the surface potential of the different facets of silver nano-plates even if the measurements were done in ambient conditions without the use of vacuum. A phenomenological model was used to calculate the differences of facet work function of the silver nano-plates and the corresponding shift in Fermi level. This theoretical prediction and the experimentally observed difference in surface potential on the silver nano-plates were in good agreement. Our results show the possibility to sense the nano-crystal facets by appropriate choice of the substrate in ambient conditions.

Unraveling the molecular mechanism of photosynthetic toxicity of highly fluorescent silver nanoclusters to Scenedesmus obliquus.

PubMed

Zhang, Li; Goswami, Nirmal; Xie, Jianping; Zhang, Bo; He, Yiliang

2017-11-27

While the discovery of numerous attractive properties of silver at the nanoscale has increased their demand in many sectors including medicine, optics, sensing, painting and cosmetics, it has also raised wide public concerns about their effect on living organisms in aquatic environment. Despite the continuous effort to understand the various aspects of the toxicity of silver nanomaterials, the molecular level understanding on their cytotoxicity mechanism to biological organisms has remained unclear. Herein, we demonstrated the underlying mechanism of the photosynthetic toxicity against green algae namely, Scenedesmus obliquus by using an emerging silver nanomaterial, called silver nanoclusters (defined as r-Ag NCs). By exploiting the unique fluorescence properties of r-Ag NCs along with various other analytical/biological tools, we proposed that the photosynthetic toxicity of r-Ag NCs was largely attributed to the "joint-toxicity" effect of particulate form of r-Ag NCs and its released Ag + , which resulted in the disruption of the electron transport chain of light reaction and affected the content of key enzymes (RuBP carboxylase/ oxygenase) of Calvin cycle of algae cells. We believe that the present study can also be applied to the assessment of the ecological risk derived from other metal nanoparticles.

Toxicity of silver nanoparticles in biological systems: Does the complexity of biological systems matter?

PubMed

Vazquez-Muñoz, Roberto; Borrego, Belen; Juárez-Moreno, Karla; García-García, Maritza; Mota Morales, Josué D; Bogdanchikova, Nina; Huerta-Saquero, Alejandro

2017-07-05

Currently, nanomaterials are more frequently in our daily life, specifically in biomedicine, electronics, food, textiles and catalysis just to name a few. Although nanomaterials provide many benefits, recently their toxicity profiles have begun to be explored. In this work, the toxic effects of silver nanoparticles (35nm-average diameter and Polyvinyl-Pyrrolidone-coated) on biological systems of different levels of complexity was assessed in a comprehensive and comparatively way, through a variety of viability and toxicological assays. The studied organisms included viruses, bacteria, microalgae, fungi, animal and human cells (including cancer cell lines). It was found that biological systems of different taxonomical groups are inhibited at concentrations of silver nanoparticles within the same order of magnitude. Thus, the toxicity of nanomaterials on biological/living systems, constrained by their complexity, e.g. taxonomic groups, resulted contrary to the expected. The fact that cells and virus are inhibited with a concentration of silver nanoparticles within the same order of magnitude could be explained considering that silver nanoparticles affects very primitive cellular mechanisms by interacting with fundamental structures for cells and virus alike. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of silver nanoparticles on human mesenchymal stem cell differentiation

PubMed Central

Diendorf, Jörg; Epple, Matthias; Schildhauer, Thomas A; Köller, Manfred

2014-01-01

Summary Background: Silver nanoparticles (Ag-NP) are one of the fastest growing products in nano-medicine due to their enhanced antibacterial activity at the nanoscale level. In biomedicine, hundreds of products have been coated with Ag-NP. For example, various medical devices include silver, such as surgical instruments, bone implants and wound dressings. After the degradation of these materials, or depending on the coating technique, silver in nanoparticle or ion form can be released and may come into close contact with tissues and cells. Despite incorporation of Ag-NP as an antibacterial agent in different products, the toxicological and biological effects of silver in the human body after long-term and low-concentration exposure are not well understood. In the current study, we investigated the effects of both ionic and nanoparticulate silver on the differentiation of human mesenchymal stem cells (hMSCs) into adipogenic, osteogenic and chondrogenic lineages and on the secretion of the respective differentiation markers adiponectin, osteocalcin and aggrecan. Results: As shown through laser scanning microscopy, Ag-NP with a size of 80 nm (hydrodynamic diameter) were taken up into hMSCs as nanoparticulate material. After 24 h of incubation, these Ag-NP were mainly found in the endo-lysosomal cell compartment as agglomerated material. Cytotoxicity was observed for differentiated or undifferentiated hMSCs treated with high silver concentrations (≥20 µg·mL−1 Ag-NP; ≥1.5 µg·mL−1 Ag+ ions) but not with low-concentration treatments (≤10 µg·mL−1 Ag-NP; ≤1.0 µg·mL−1 Ag+ ions). Subtoxic concentrations of Ag-NP and Ag+ ions impaired the adipogenic and osteogenic differentiation of hMSCs in a concentration-dependent manner, whereas chondrogenic differentiation was unaffected after 21 d of incubation. In contrast to aggrecan, the inhibitory effect of adipogenic and osteogenic differentiation was confirmed by a decrease in the secretion of specific biomarkers, including adiponectin (adipocytes) and osteocalcin (osteoblasts). Conclusion: Aside from the well-studied antibacterial effect of silver, little is known about the influence of nano-silver on cell differentiation processes. Our results demonstrate that ionic or nanoparticulate silver attenuates the adipogenic and osteogenic differentiation of hMSCs even at non-toxic concentrations. Therefore, more studies are needed to investigate the effects of silver species on cells at low concentrations during long-term treatment. PMID:25551033

Towards ultrasensitive malaria diagnosis using surface enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Chen, Keren; Yuen, Clement; Aniweh, Yaw; Preiser, Peter; Liu, Quan

2016-02-01

We report two methods of surface enhanced Raman spectroscopy (SERS) for hemozoin detection in malaria infected human blood. In the first method, silver nanoparticles were synthesized separately and then mixed with lysed blood; while in the second method, silver nanoparticles were synthesized directly inside the parasites of Plasmodium falciparum. It was observed that the first method yields a smaller variation in SERS measurements and stronger correlation between the estimated contribution of hemozoin and the parasitemia level, which is preferred for the quantification of the parasitemia level. In contrast, the second method yields a higher sensitivity to a low parasitemia level thus could be more effective in the early malaria diagnosis to determine whether a given blood sample is positive.

Housing system and laying hen strain impacts on egg microbiology.

PubMed

Jones, D R; Anderson, K E

2013-08-01

Alternative hen housing is becoming more commonplace in the egg market. However, a complete understanding of the implications for alternative housing systems on egg safety has not been achieved. The current study examines the impact of housing Hy-Line Brown, Hy-Line Silver Brown, and Barred Plymouth Rock hens in conventional cage, cage-free, and free range egg production systems on shell microbiology. Eggs were collected at 4 sampling periods. Egg shell emulsion pools were formed and enumerated for total aerobic organisms, Enterobacteriaceae, and yeast and mold counts. Hy-Line Brown and Hy-Line Silver Brown hens produced eggs with significantly (P < 0.05 and 0.001, respectively) different levels of aerobic organisms dependent on housing system. Eggs from conventional cages had significantly different (P < 0.05) levels of aerobic contamination in relation to hen strain with Hy-Line Silver Brown having the greatest (4.57 log cfu/mL). Hy-Line Brown and Barred Plymouth Rock hens produced eggs with significantly different (P < 0.01) levels of Enterobacteriaceae among housing systems with conventional caged eggs having the lowest level of contamination for the hen strains. There were no differences within each strain among housing systems for yeast and mold contamination. The study shows that hen strain has an effect on egg microbial levels for various housing systems, and egg safety should be considered when making hen strain selections for each housing system.

Early use of negative pressure therapy in combination with silver dressings in a difficult breast abscess.

PubMed

Richards, Alastair J; Hagelstein, Sue M; Patel, Girish K; Ivins, Nicola M; Sweetland, Helen M; Harding, Keith G

2011-12-01

Combining silver-based dressings with negative pressure therapy after radical excision of chronically infected breast disease is a novel application of two technologies. One patient with complex, chronic, infected breast disease underwent radical excision of the affected area and was treated early with a combination of silver-based dressings and topical negative pressure therapy. The wound was then assessed sequentially using clinical measurements of wound area and depth, pain severity scores and level of exudation. It is possible to combine accepted techniques with modern dressing technologies that result in a positive outcome. In this case, the combination of a silver-based dressing with negative pressure therapy following radical excision proved safe and was well tolerated by the patient. Full epithelisation of the wound was achieved and there was no recurrence of the infection for the duration of the treatment. © 2011 The Authors. © 2011 Blackwell Publishing Ltd and Medicalhelplines.com Inc.

Enhancement of elemental mercury adsorption by silver supported material.

PubMed

Khunphonoi, Rattabal; Khamdahsag, Pummarin; Chiarakorn, Siriluk; Grisdanurak, Nurak; Paerungruang, Adjana; Predapitakkun, Somrudee

2015-06-01

Mercury, generally found in natural gas, is extremely hazardous. Although average mercury levels are relatively low, they are further reduced to comply with future mercury regulations, which are stringent in order to avoid releasing to the environment. Herein, vapor mercury adsorption was therefore investigated using two kinds of supports, granular activated carbon (GAC) and titanium dioxide (TiO2). Both supports were impregnated by silver (5 and 15 wt.%), before testing against a commercial adsorbent (sulfur-impregnated activated carbon, SAC). The adsorption isotherm, kinetics, and its thermodynamics of mercury adsorption were reported. The results revealed that Langmuir isotherm provided a better fit to the experimental data. Pseudo second-order was applicable to describe adsorption kinetics. The higher uniform Ag dispersion was a key factor for the higher mercury uptake. TiO2 supported silver adsorbent showed higher mercury adsorption than the commercial one by approximately 2 times. Chemisorption of mercury onto silver active sites was confirmed by an amalgam formation found in the spent adsorbents. Copyright © 2015. Published by Elsevier B.V.

A new medium for Caenorhabditis elegans toxicology and nanotoxicology studies designed to better reflect natural soil solution conditions.

PubMed

Tyne, William; Lofts, Stephen; Spurgeon, David J; Jurkschat, Kerstin; Svendsen, Claus

2013-08-01

A new toxicity test medium for Caenorhabditis elegans is presented. The test solution is designed to provide a better representation of natural soil pore water conditions than currently available test media. The medium has a composition that can readily be modified to allow for studies of the influences of a range of environmentally relevant parameters on nematode biology and toxicology. Tests conducted in the new medium confirmed that nematodes' reproduction was possible at a range of solution pH levels, offering the potential to conduct toxicity studies under a variety of conditions. A test to establish silver nanoparticle and dissolved silver nitrate toxicity, a study type not feasible in M9 or agar media due to precipitation and nanoparticle agglomeration, indicated lower silver nanoparticle (median effective concentration [EC50] of 6.5 mg Ag/L) than silver nitrate (EC50 0.28 mg Ag/L) toxicity. Characterization identified stable nanoparticle behavior in the new test medium. Copyright © 2013 SETAC.

Microtitrimetry by differential electrolytic potentiometry using metallic electrodes and nanomaterials modified metallic electrodes

NASA Astrophysics Data System (ADS)

Amro, Abdulaziz Nabil

For the first time silver wire electrodes have been coated with carbon nanotubes using floating catalyst chemical vapor deposition (CVD) method. The production of CNTs has been conducted in a horizontal tubular reactor. Acetylene gas was used as a carbon source. Ferrocene has been used as a catalyst precursor for the growth of CNT. Different parameters have been optimized to get a high yield of CNTs and ensure their growth on the silver electrodes using univariate method. The parameters studied include the hydrogen flow rate, acetylene flow rate, temperature of the furnace, time of the reaction and the location of the electrodes in the reactor tube. The optimum conditions for those parameters were: for hydrogen and acetylene, the flow rates were 25 mL /min and 75 mL / min respectively. The furnace temperature was found to be 700 °C and the reaction time was 15 minutes. Regarding the location of the silver wires it should be located in the first 10 cm of the front side of the tube. Scanning electron microscopy (SEM) and transition electron microscopy (TEM) have been used to characterize carbon on silver electrodes. According to the experimental results, TEM figures show that CNT produced on Silver wire is multiwall carbon nanotubes MWCNT. Silver electrodes either pure or coated with CNT were used as indicating systems in micro titration using both dc differential electrolytic potentiometry (DEP) and mark-space bias DEP techniques. All types of titrimetric reactions were investigated using different types of electrodes like Pt and gold for oxidation reduction titrations, antimony electrodes for acid base titrations, silver electrodes for precipitation titrations in addition to Ag-CNT electrodes. End points at volumes of 1 microL were determined. Different parameters were optimized like the current density, the percentage bias, the volume of the sample and the concentrations of the reactants. Microtitrimetry has been applied on several types of analytes; Ferrous, Ascorbic acid, chloride, Cyanide, Sodium Bicarbonate and Ketoconazole in aqueous and non- aqueous medium. The performance of Ag-CNT electrodes was found to be much better than the normal silver electrodes. The differential titration curves obtained were symmetrical with significant heights. For silver electrodes coated with CNT the first derivative of the potential was found to give better curves than the normal differential curves, hence the end point location was successfully achieved. A micro liter injector that can deliver volumes at a micro liter level was designed and fabricated. Microtitrimetry which requires volumes of reagents at the micro liter level can offer a solution to the large consumption of reagents in all classical titrimetric processes. Hence, large savings in reagents as well as less waste will reach the environment.

45 CFR 156.20 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Affordable Care Act; and (3) A bronze, silver, gold, or platinum level of coverage as described in section....103 of this subtitle. Level of coverage means one of four standardized actuarial values as defined by...

Swimming Performance of Bighead Carp and Silver Carp: Methodology, Metrics, and Management Applications

DTIC Science & Technology

2012-08-01

upstream. “Accelerated Water Velocity” is under consideration as a control for aquatic nuisance species in the Great Lakes-Mississippi River Interbasin...2009. Oxygen consumption rates for bighead and silver carp in relation to life-stage and water temperature. J. Freshwater Ecology 24(4): 535-543...19.5 SD) are displaced by water velocities averaging only 25 cm/s + 3.8 SD (Layher and Ralston 1997). High activity levels of two enzymes

Particulate and colloidal silver in sewage effluent and sludge discharged from British wastewater treatment plants.

PubMed

Johnson, Andrew C; Jürgens, Monika D; Lawlor, Alan J; Cisowska, Iwona; Williams, Richard J

2014-10-01

Differential filtration was used to measure silver (>2 nm) entering and leaving nine sewage treatment plants (STPs). The mean concentration of colloidal (2-450 nm) silver, which includes nanosilver, was found to be 12 ng L(-1) in the influent and 6 ng L(-1) in the effluent. For particulate silver (>450 nm) the mean values were 3.3 μg L(-1) for influent and 0.08 μg L(-1) for effluent. Thus, removal was around 50% and 98% for colloidal and particulate silver respectively. There was no significant difference in performance between the different types of STP investigated (three examples each of activated sludge, biological filter and biological filter with tertiary treatment located across England, UK). In addition, treated sewage sludge samples (biosolids) were taken from several STPs to measure the total silver likely to be discharged to soils. Total silver was 3-14 mg kg(-1) DW in the sludge (median 3.6), which if the sludge were added at the recommended rate to soil, would add 11 μg kg(-1) yr(-1) to the top 20 cm soil layer. Predicted concentrations using the LF2000-WQX model for all the rivers of England and Wales for nanosilver were typically in the 0-1 ng L(-1) range but levels up to 4 ng L(-1) are possible in a high discharge and low flow scenario. Predicted concentrations for the total particulate forms were mostly below 50 ng L(-1) except for a high discharge and low flow scenario where concentrations could reach 135 ng L(-1). Copyright © 2014 Elsevier Ltd. All rights reserved.

Pre-heating mitigates composite degradation

PubMed Central

da SILVA, Jessika Calixto; Rogério Vieira, REGES; REGE, Inara Carneiro Costa; CRUZ, Carlos Alberto dos Santos; VAZ, Luís Geraldo; ESTRELA, Carlos; de CASTRO, Fabrício Luscino Alves

2015-01-01

ABSTRACT Dental composites cured at high temperatures show improved properties and higher degrees of conversion; however, there is no information available about the effect of pre-heating on material degradation. Objectives This study evaluated the effect of pre-heating on the degradation of composites, based on the analysis of radiopacity and silver penetration using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Material and Methods Thirty specimens were fabricated using a metallic matrix (2x8 mm) and the composites Durafill VS (Heraeus Kulzer), Z-250 (3M/ESPE), and Z-350 (3M/ESPE), cured at 25°C (no pre-heating) or 60°C (pre-heating). Specimens were stored sequentially in the following solutions: 1) water for 7 days (60°C), plus 0.1 N sodium hydroxide (NaOH) for 14 days (60°C); 2) 50% silver nitrate (AgNO3) for 10 days (60°C). Specimens were radiographed at baseline and after each storage time, and the images were evaluated in gray scale. After the storage protocol, samples were analyzed using SEM/EDS to check the depth of silver penetration. Radiopacity and silver penetration data were analyzed using ANOVA and Tukey’s tests (α=5%). Results Radiopacity levels were as follows: Durafill VSZ-350>Z-250 (p<0.05). After storage in water/NaOH, pre-heated specimens presented higher radiopacity values than non-pre-heated specimens (p<0.05). There was a lower penetration of silver in pre-heated specimens (p<0.05). Conclusions Pre-heating at 60°C mitigated the degradation of composites based on analysis of radiopacity and silver penetration depth. PMID:26814459

The biological effects and possible modes of action of nanosilver.

PubMed

Völker, Carolin; Oetken, Matthias; Oehlmann, Jörg

2013-01-01

Novel physicochemical and biological properties have led to a versatile spectrum of applications for nanosized silver particles. Silver nanoparticles are applied primarily for their antimicrobial effects, and may variety of commercially available products have emerged. To better predict and prevent possible environmental impacts from silver nanoparticles that are derived from increasing production volumes and environmental release, more data on the biological effects are needed on appropriate model organisms. We examined the literature that addressed the adverse effects of silver nanoparticles on different levels of biological integration, including in vitro and in vivo test systems. Results of in vitro studies indicate a dose-dependent programmed cell death included by oxidative stress as main possible pathway of toxicity. Furthermore, silver nanoparticles may affect cellular enzymes by interference with free thiol groups and mimicry of endogenous ions. Similar mechanisms may apply for antibacterial effects produced by nonasilver. These effects are primary from the interference nanosilver has with bacterial cell membranes. Few in vivo studies have been performed to evaluated the toxic mode of action of nanosilver or to provide evidence for oxidative stress as an important mechanism of nanosilver toxicity. Organisms that are most acutely sensitive to nanosilver toxicity are the freshwater filter-freeding organisms. Both in vitro and in vivo studies have demonstrated tha silver ions released from nanoparticle surface contribute to the toxicity, and, indeed, some findings indicated a unique nanoparticles effect. For an adequate evaluation of the environmental impact of nanosilver, greater emphasis should be placed on combining mechanistic investigations that are performed in vitro, with results obtained in in vivo test systems. Future in vivo test system studies should emphasize long-term exposure scenarios. Moreover, the dietary uptake of silver nanoparticles and the potential to bioaccumulate through the food web should be examined in detail.

Fabrication of biogenic antimicrobial silver nanoparticles by Streptomyces aegyptia NEAE 102 as eco-friendly nanofactory.

PubMed

El-Naggar, Noura El-Ahmady; Abdelwahed, Nayera A M; Darwesh, Osama M M

2014-04-01

The current research was focused on the extracellular biosynthesis of bactericidal silver nanoparticles (AgNPs) using cell-free supernatant of a local isolate previously identified as a novel Streptomyces aegyptia NEAE 102. The biosynthesis of silver nanoparticles by Streptomyces aegyptia NEAE 102 was quite fast and required far less time than previously published strains. The produced particles showed a single surface plasmon resonance peak at 400 nm by UV-Vis spectroscopy, which confirmed the presence of AgNPs. Response surface methodology was chosen to evaluate the effects of four process variables (AgNO3 concentration, incubation period, pH levels, and inoculum size) on the biosynthesis of silver nanoparticles by Streptomyces aegyptia NEAE 102. Statistical analysis of the results showed that the linear and quadratic effects of incubation period, initial pH, and inoculum size had a significant effect (p < 0.05) on the biosynthesis of silver nanoparticles by Streptomyces aegyptia NEAE 102. The maximum silver nanoparticles biosynthesis (2.5 OD, at 400 nm ) was achieved in runs number 5 and 14 under the conditions of 1 mM AgNO3 (1-1.5% (v/v)), incubation period (72-96 h), initial pH (9-10), and inoculum size (2-4% (v/v)). An overall 4-fold increase in AgNPs biosynthesis was obtained as compared with that of unoptimized conditions. The biosynthesized silver nanoparticles were characterized using UV-VIS spectrophotometer and Fourier transform infrared spectroscopy analysis, in addition to antimicrobial properties. The biosynthesized AgNPs significantly inhibited the growth of medically important pathogenic gram-positive (Staphylococcus aureus) and gram-negative bacteria (Pseudomonas aeruginosa) and yeast (Candida albicans).

Effect of media composition on bioavailability and toxicity of silver and silver nanoparticles in fish intestinal cells (RTgutGC).

PubMed

Minghetti, Matteo; Schirmer, Kristin

2016-12-01

To understand conditions affecting bioavailability and toxicity of citrate-coated silver nanoparticles (cit-AgNP) and dissolved silver at the luminal enterocyte interface, we exposed rainbow trout (Oncorhynchus mykiss) gut cells (RTgutGC) in media of contrasting composition: two amino acid-containing media, one of which was supplemented with proteins, as can be expected during digestion; and two protein and amino acid-free media contrasting low and high chloride content, as can be expected in the lumen of fish adapting to freshwater or seawater, respectively. Dose-response curves were generated measuring cell metabolic activity, membrane and lysosome integrity over a period of 72 hours. Then, nontoxic doses were applied and total silver accumulation, metallothionein and glutathione reductase mRNA levels were determined. The presence of proteins stabilized cit-AgNP keeping them in suspension. Conversely, in protein-free media, cit-AgNP agglomerated and settled, resulting in higher cellular accumulation of silver and toxicity. Chloride concentrations in exposure media modulated the toxicity of AgNO 3 but not of cit-AgNP. Moreover, while amino acid-containing media are protective against AgNO 3 , likely due to the formation of thiolate complexes, they are only partially protective against cit-AgNP. Viability assays indicated that lysosomes are targets of cit-AgNP, supporting the hypothesis that cit-AgNP exert toxicity intracellularly. Metallothionein, a sensor of metal bioavailability, was induced by cit-AgNP in high chloride medium but not in low chloride medium, indicating that chloride might have a role in mobilizing silver from intercellular vesicles. Overall, this study shows that AgNP bioavailability and toxicity in the intestine is linked to its luminal content.

Optimization of silver-dielectric-silver nanoshell for sensing applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shirzaditabar, Farzad; Saliminasab, Maryam

2013-08-15

In this paper, resonance light scattering (RLS) properties of a silver-dielectric-silver nanoshell, based on quasi-static approach and plasmon hybridization theory, are investigated. Scattering spectrum of silver-dielectric-silver nanoshell has two intense and clearly separated RLS peaks and provides a potential for biosensing based on surface plasmon resonance and surface-enhanced Raman scattering. The two RLS peaks in silver-dielectric-silver nanoshell are optimized by tuning the geometrical dimensions. In addition, the optimal geometry is discussed to obtain the high sensitivity of silver-dielectric-silver nanoshell. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness increases the sensitivitymore » of silver-dielectric-silver nanoshell.« less

Metal ion release from silver soldering and laser welding caused by different types of mouthwash.

PubMed

Erdogan, Ayse Tuygun; Nalbantgil, Didem; Ulkur, Feyza; Sahin, Fikrettin

2015-07-01

To compare metal ion release from samples welded with silver soldering and laser welding when immersed into mouthwashes with different ingredients. A total of 72 samples were prepared: 36 laser welded and 36 silver soldered. Four samples were chosen from each subgroup to study the morphologic changes on their surfaces via scanning electron microscopy (SEM). Each group was further divided into four groups where the samples were submerged into mouthwash containing sodium fluoride (NaF), mouthwash containing sodium fluoride + alcohol (NaF + alcohol), mouthwash containing chlorhexidine (CHX), or artificial saliva (AS) for 24 hours and removed thereafter. Subsequently, the metal ion release from the samples was measured with inductively coupled plasma mass spectrometry (ICP-MS). The metal ion release among the solutions and the welding methods were compared. The Kruskal-Wallis and analysis of variance (ANOVA) tests were used for the group comparisons, and post hoc Dunn multiple comparison test was utilized for the two group comparisons. The level of metal ion release from samples of silver soldering was higher than from samples of laser welding. Furthermore, greater amounts of nickel, chrome, and iron were released from silver soldering. With regard to the mouthwash solutions, the lowest amounts of metal ions were released in CHX, and the highest amounts of metal ions were released in NaF + alcohol. SEM images were in accord with these findings. The laser welding should be preferred over silver soldering. CHX can be recommended for patients who have welded appliances for orthodontic reasons.

Antibacterial silver nanocluster/silica composite coatings on stainless steel

NASA Astrophysics Data System (ADS)

Ferraris, M.; Perero, S.; Ferraris, S.; Miola, M.; Vernè, E.; Skoglund, S.; Blomberg, E.; Odnevall Wallinder, I.

2017-02-01

A coating made of silver nanocluster/silica composites has been deposited, via a radio frequency (RF) co-sputtering technique, for the first time onto stainless steel (AISI 304L) with the aim to improve its antibacterial properties. Different thermal treatments after coating deposition have been applied in order to optimize the coating adhesion, cohesion and its antibacterial properties. Its applicability has been investigated at realistic conditions in a cheese production plant. The physico-chemical characteristics of the coatings have been analyzed by means of different bulk and surface analytical techniques. Field emission scanning electron microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS), contact angle measurements and atomic force microscopy (AFM) were employed to assess coating morphology, composition, surface roughness, wetting properties, size and local distribution of the nanoparticles within the coating. Tape tests were used to determine the adhesion/cohesion properties of the coating. The amount and time-dependence of released silver in solutions of acetic acid, artificial water, artificial tap water and artificial milk were determined by means of Atomic Absorption Spectroscopy (AAS). The antibacterial effect of the coating was evaluated at different experimental conditions using a standard bacterial strain of Staphylococcus aureus in compliance with National Committee for Clinical Laboratory Standards (NCCLS) and AATCC 147 standards. The Ahearn test was performed to measure the adhesion of bacteria to the coated stainless steel surface compared with a control surface. The antibacterial coating retained its antibacterial activity after thermal treatment up to 450 °C and after soaking in common cleaning products for stainless steel surfaces used for e.g. food applications. The antibacterial capacity of the coating remained at high levels for 1-5 days, and showed a good capacity to reduce the adhesion of bacteria up to 30 days. Only a few percent of silver in the coating was released into acetic acid, even after 10 days of exposure at 40 °C. Most silver (> 90%) remained also in the coating even after 240 h of continuous exposure. Similar observations were made after repeated exposure at 100 °C. Very low levels of released silver in solution were observed in artificial milk. No release of silver nanoparticles was observed either in synthetic tap water or in artificial milk at given conditions. The coating further displayed good antibacterial properties also when tested during working conditions in a cheese production plant.

Comparison of DNA Damage and Apoptosis Induced By Silver Nanoparticle-containing Dressing Materials During Wound Healing.

PubMed

Choi, Young Suk; Gwak, Heui-Chul; Park, Jae Keun; Lim, Ji Yun; Yeo, Eui Dong; Park, Eunseok; Kim, Junyong; Lee, Young Koo

2018-04-13

Silver nanoparticle (AgNP)-containing dressings are used worldwide for the treatment of wounds; however, many studies have indicated that AgNPs are toxic to humans and cause cell death, primarily via apoptosis. In this study, the investigators compare the apoptotic effects of various AgNP dressing materials, with the hypothesis that nanosilver would be less toxic than ionic silver. For the in vivo experiments, Sprague-Dawley (SD) and streptozotocin (STZ)-induced diabetic rats were treated with 5 dressing materials: Aquacel Ag (product A, silver ion; ConvaTec, Berkshire, UK), Acticoat (product B, AgNP; Smith & Nephew, Fort Worth, TX), Medifoam Silver (product C, silver ion; Genewel Science Co Ltd, Seongnam, South Korea), PolyMem Silver (product D, AgNP; Ferris Mfg Corp, Fort Worth, TX), and Vaseline-impregnated dressing gauze (control; Unilever, London, UK). All treatments were applied 3 times per week. After 14 days of treatment, the SD and STZ rats were euthanized, and wound samples were examined for apoptosis. The analysis included immunohistochemistry, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, Western blotting, and reverse transcription polymerase chain reaction for a semiquantitative evaluation of apoptosis. The AgNP-containing dressing materials were more cytotoxic than the silver dressings. Compared with the AgNP dressing materials, no significant levels of apoptotic factors were observed in the silver dressing-treated wounds. The TUNEL staining showed that product C-dressed wounds contained the most apoptotic cells, while some apoptotic cells were observed in product B-dressed wounds. Moreover, apoptotic gene expression was altered, including a decline in B-cell lymphoma-2 and activation of caspase-3. This was most evident in wounds treated with product C. Interestingly, apoptotic gene expression was not induced in product A-treated wounds. Finally, product D had a relatively lower silver concentration and was less toxic than products A-C. Dressing materials containing AgNP have an antimicrobial effect. However, the authors observed that some AgNP dressings induced DNA damage and apoptosis. Although AgNP dressings did not cause significant acute apoptotic effects, they should be examined for cytotoxic effects in chronic wounds and should be used with caution when treating chronic wounds and those with low bacteria counts.

Green synthesis of silver nanoparticles using methanolic root extracts of Diospyros paniculata and their antimicrobial activities.

PubMed

Rao, N Hanumanta; N, Lakshmidevi; Pammi, S V N; Kollu, Pratap; S, Ganapaty; P, Lakshmi

2016-05-01

Since the discovery and subsequent widespread use of antibiotics, a variety of bacterial species of human and animal origin have developed numerous mechanisms that render bacteria resistant to some, and in certain cases to nearly all antibiotics, thereby limiting the treatment options and compromising effective therapy. In the present study, the green synthesis of nanoparticles is carried out by the reduction of silver acetate in the presence of crude methanolic root extracts of Diospyros paniculata, a member of family Ebenaceae. The UV-Vis absorption spectrum of the biologically reduced reaction mixture showed the surface plasmon peak at 428 nm, a characteristic peak of silver nanoparticles. X-ray diffraction (XRD) analysis confirmed the face-centered cubic crystalline structure of metallic silver. The average diameter of Ag NPs is about 17 nm from Transmission Electron Microscopy (TEM) which is in good agreement with the average crystallite size (19 nm) calculated from XRD analysis. Further the study has been extended to the antimicrobial activity against test pathogenic Gram (+), Gram (-) bacterial and fungal strains. The biologically synthesized silver nanoparticles showed promising activity against all the tested pathogenic strains and the activity has been enhanced with the increased dose levels. Copyright © 2016 Elsevier B.V. All rights reserved.

Silver nanoparticles: synthesis and application in mineralization of pesticides using membrane support

NASA Astrophysics Data System (ADS)

Manimegalai, G.; Shanthakumar, S.; Sharma, Chandan

2014-05-01

Pesticides are deliberately used for controlling the pests in agriculture and public health, due to which, a part of it is present in the drinking water. Due to their widespread use, they are present in both surface and ground water. Most of the pesticides are resistant to biodegradation and are found to be carcinogenic in nature even at trace levels. Conventional methods of pesticide removal are disadvantageous due to their inherent time consumption or expensiveness. Nanoparticles alleviate both of these drawbacks and hence, they can be effectively utilized for the mineralization of pesticides. To prevent the presence of nanoparticles in the purified water after mineralization of pesticides, they need to be incorporated on a support. In earlier studies, researchers employed activated carbon and alumina as support for silver nanoparticles in pesticide mineralization. However, not many studies have been carried out on polymeric membranes as support for silver nanoparticles in the mineralization of pesticides (chlorpyrifos and malathion). With this in view, a detailed study has been carried out to estimate the mineralization potential of silver nanoparticles (synthesized using glucose) supported on cellulose acetate membrane. It is observed that the silver nanoparticles can effectively mineralize the pesticides, and the concentration of nanoparticles enhances the rate of mineralization.

Silver nanoparticle-doped zirconia capillaries for enhanced bacterial filtration.

PubMed

Wehling, Julia; Köser, Jan; Lindner, Patrick; Lüder, Christian; Beutel, Sascha; Kroll, Stephen; Rezwan, Kurosch

2015-03-01

Membrane clogging and biofilm formation are the most serious problems during water filtration. Silver nanoparticle (Agnano) coatings on filtration membranes can prevent bacterial adhesion and the initiation of biofilm formation. In this study, Agnano are immobilized via direct reduction on porous zirconia capillary membranes to generate a nanocomposite material combining the advantages of ceramics being chemically, thermally and mechanically stable with nanosilver, an efficient broadband bactericide for water decontamination. The filtration of bacterial suspensions of the fecal contaminant Escherichia coli reveals highly efficient bacterial retention capacities of the capillaries of 8 log reduction values, fulfilling the requirements on safe drinking water according to the U.S. Environmental Protection Agency. Maximum bacterial loading capacities of the capillary membranes are determined to be 3×10(9)bacterialcells/750mm(2) capillary surface until back flushing is recommendable. The immobilized Agnano remain accessible and exhibit strong bactericidal properties by killing retained bacteria up to maximum bacterial loads of 6×10(8)bacterialcells/750mm(2) capillary surface and the regenerated membranes regain filtration efficiencies of 95-100%. Silver release is moderate as only 0.8% of the initial silver loading is leached during a three-day filtration experiment leading to average silver contaminant levels of 100μg/L. Copyright © 2014 Elsevier B.V. All rights reserved.

Explaining reaction mechanisms using the dual descriptor: a complementary tool to the molecular electrostatic potential.

PubMed

Martínez-Araya, Jorge Ignacio

2013-07-01

The intrinsic reactivity of cyanide when interacting with a silver cation was rationalized using the dual descriptor (DD) as a complement to the molecular electrostatic potential (MEP) in order to predict interactions at the local level. It was found that DD accurately explains covalent interactions that cannot be explained by MEP, which focuses on essentially ionic interactions. This allowed the rationalization of the reaction mechanism that yields silver cyanide in the gas phase. Other similar reaction mechanisms involving a silver cation interacting with water, ammonia, and thiosulfate were also explained by the combination of MEP and DD. This analysis provides another example of the usefulness of DD as a tool for gaining a deeper understanding of any reaction mechanism that is mainly governed by covalent interactions.

Adaptation of the ammoniacal silver reaction to cytochemical demonstration of myelin basic protein.

PubMed

Staykova, M; Jordanov, J; Goranov, I

1978-01-01

A modification of Black and Ansley's ammoniacal silver reaction (ASR) for histones is proposed for visualizing myelin basic protien (MBP) in the nervous system. The reaction is performed on histological sections of tissues fixed in neutralized formalin-alcohol and delipidized in the course of the routine paraffin embedding. The deparaffinized sections are again treated with formalin in order to make the "unmasked" by the delipidization basic groups of MBP reactive to ammoniacal silver. After treatment with this reagent MBP of the myelin sheaths of the nerve fibres is impregnated brownish-black. Deparaffinized sections subjected to an extraction of MBP with hydrochloric acid exhibit a negative reaction at the level of the myelin sheaths the same reaction being preserved at the level of the nuclear histones. The reaction is positive in paper spots of nervous tissue extracts obtained with the same acid. These assays indicate the specificity of the modified ASR. The method can be used for studies on the processes of myelination and demylination in normal histogenesis and in pathology of the nervous tissue.

Silver nanoparticles and dissolved silver activate contrasting immune responses and stress-induced heat shock protein expression in sea urchin.

PubMed

Magesky, Adriano; de Oliveira Ribeiro, Ciro A; Beaulieu, Lucie; Pelletier, Émilien

2017-07-01

Using immune cells of sea urchin Strongylocentrotus droebachiensis in early development as a model, the cellular protective mechanisms against ionic and poly(allylamine)-coated silver nanoparticle (AgNPs; 14 ± 6 nm) treatments at 100 μg L -1 were investigated. Oxidative stress, heat shock protein expression, and pigment production by spherulocytes were determined as well as AgNP translocation pathways and their multiple effects on circulating coelomocytes. Sea urchins showed an increasing resilience to Ag over time because ionic Ag is accumulated in a steady way, although nanoAg levels dropped between 48 h and 96 h. A clotting reaction emerged on tissues injured by dissolved Ag (present as chloro-complexes in seawater) between 12 h and 48 h. Silver contamination and nutritional state influenced the production of reactive oxygen species. After passing through coelomic sinuses and gut, AgNPs were found in coelomocytes. Inside blood vessels, apoptosis-like processes appeared in coelomocytes highly contaminated by poly(allylamine)-coated AgNPs. Increasing levels of Ag accumulated by urchins once exposed to AgNPs pointed to a Trojan-horse mechanism operating over 12-d exposure. However, under short-term treatments, physical interactions of poly(allylamine)-coated AgNPs with cell structures might be, at some point, predominant and responsible for the highest levels of stress-related proteins detected. The present study is the first report detailing nano-translocation in a marine organism and multiple mechanisms by which sea urchin cells can deal with toxic AgNPs. Environ Toxicol Chem 2017;36:1872-1886. © 2016 SETAC. © 2016 SETAC.

Comparison of three different dressings for partial thickness burns in children: study protocol for a randomised controlled trial.

PubMed

Gee Kee, Emma; Kimble, Roy M; Cuttle, Leila; Stockton, Kellie

2013-11-25

In the paediatric population, pain and distress associated with burn injuries during wound care procedures remain a constant challenge. Although silver dressings are the gold standard for burn care in Australasia, very few high-level trials have been conducted that compare silver dressings to determine which will provide the best level of care clinically. Therefore, for paediatric patients in particular, identifying silver dressings that are associated with lower levels of pain and rapid wound re-epithelialisation is imperative. This study will determine whether there is a difference in time to re-epithelialisation and pain and distress experienced during wound care procedures among Acticoat™, Acticoat™ combined with Mepitel™ and Mepilex Ag™ dressings for acute, paediatric partial thickness burns. Children aged 0 to 15 years with an acute partial thickness (superficial partial to deep partial thickness inclusive) burn injury and a burn total body surface area of ≤ 10% will be eligible for the trial. Patients will be randomised to one of the three dressing groups: (1) Acticoat™ or (2) Acticoat™ combined with Mepitel™ or (3) Mepilex Ag™. A minimum of 28 participants will be recruited for each treatment group. Primary measures of pain, distress and healing will be repeated at each dressing change until complete wound re-epithelialisation occurs or skin grafting is required. Additional data collected will include infection status at each dressing change, physical function, scar outcome and scar management requirements, cost effectiveness of each dressing and staff perspectives of the dressings. The results of this study will determine the effects of three commonly used silver and silicone burn dressing combinations on the rate of wound re-epithelialisation and pain experienced during dressing procedures in acute, paediatric partial thickness burn injuries. Australian New Zealand Clinical Trials Registry ACTRN12613000105741.

Safety and efficacy of composite collagen-silver nanoparticle hydrogels as tissue engineering scaffolds

NASA Astrophysics Data System (ADS)

Alarcon, Emilio I.; Udekwu, Klas I.; Noel, Christopher W.; Gagnon, Luke B.-P.; Taylor, Patrick K.; Vulesevic, Branka; Simpson, Madeline J.; Gkotzis, Spyridon; Islam, M. Mirazul; Lee, Chyan-Jang; Richter-Dahlfors, Agneta; Mah, Thien-Fah; Suuronen, Erik J.; Scaiano, Juan C.; Griffith, May

2015-11-01

The increasing number of multidrug resistant bacteria has revitalized interest in seeking alternative sources for controlling bacterial infection. Silver nanoparticles (AgNPs), are amongst the most promising candidates due to their wide microbial spectrum of action. In this work, we report on the safety and efficacy of the incorporation of collagen coated AgNPs into collagen hydrogels for tissue engineering. The resulting hybrid materials at [AgNPs] < 0.4 μM retained the mechanical properties and biocompatibility for primary human skin fibroblasts and keratinocytes of collagen hydrogels; they also displayed remarkable anti-infective properties against S. aureus, S. epidermidis, E. coli and P. aeruginosa at considerably lower concentrations than silver nitrate. Further, subcutaneous implants of materials containing 0.2 μM AgNPs in mice showed a reduction in the levels of IL-6 and other inflammation markers (CCL24, sTNFR-2, and TIMP1). Finally, an analysis of silver contents in implanted mice showed that silver accumulation primarily occurred within the tissue surrounding the implant.The increasing number of multidrug resistant bacteria has revitalized interest in seeking alternative sources for controlling bacterial infection. Silver nanoparticles (AgNPs), are amongst the most promising candidates due to their wide microbial spectrum of action. In this work, we report on the safety and efficacy of the incorporation of collagen coated AgNPs into collagen hydrogels for tissue engineering. The resulting hybrid materials at [AgNPs] < 0.4 μM retained the mechanical properties and biocompatibility for primary human skin fibroblasts and keratinocytes of collagen hydrogels; they also displayed remarkable anti-infective properties against S. aureus, S. epidermidis, E. coli and P. aeruginosa at considerably lower concentrations than silver nitrate. Further, subcutaneous implants of materials containing 0.2 μM AgNPs in mice showed a reduction in the levels of IL-6 and other inflammation markers (CCL24, sTNFR-2, and TIMP1). Finally, an analysis of silver contents in implanted mice showed that silver accumulation primarily occurred within the tissue surrounding the implant. Electronic supplementary information (ESI) available: Representative absorption spectra of AgNP@collagen nanoparticles before and after lyophilization. Absorption spectra for the washes obtained from a 1.0 μM AgNP hydrogel over the course of 5 days. Area under the curve (AUC) calculated from the absorption spectra of 500 μm thickness collagen hydrogels prepared using different concentrations of AgNP@collagen. Selected Cryo-SEM images of BDDGE type I collagen-based hydrogels in the absence or presence of 1.0 μM AgNP. An image of a selected area of a collagen-based hydrogel prepared using AgNO3 instead of AgNP@collagen nanoparticles and Live/Dead staining of human skin fibroblasts taken for 24 hours. Growth inhibition profile for E. coli, S. aureus, S. epidermidis and P. aeruginosa in the presence of hydrogels containing AgNPs. See DOI: 10.1039/c5nr03826j

[Toxicological evaluation of nanosized colloidal silver, stabilized with polyvinylpyrrolidone. I. Characterization of nanomaterial, integral, hematological parameters, level of thiol compounds and liver cell apoptosis].

PubMed

Shumakova, A A; Shipelin, V A; Sidorova, Yu S; Trushina, E N; Mustafina, O K; Pridvorova, S M; Gmoshinsky, I V; Khotimchenko, S A

2015-01-01

Nano-sized colloidal silver (NCS) is currently one of the most widely used nanomaterials in medicine and consumer’s products. Nanoparticles (NPs) of silver, in addition to the direct exposition through products may expose human via various environmental objects. The aim of the study is to assess the safe doses of silver NP received orally. The investigated NCS contained silver NPs with diameter of 10–60 nm, predominantly with a nearly spherical form stabilized with polyvinylpyrrolidone (PVP). The experiment was performed during 92 days in 5 groups of male Wistar rats (n=15 in each group), receiving a balanced semisynthetic diet. Animal of group 1 (control) received vehicle (deionized water) intragastrically for 30 days and then with food, groups from 2nd to 4th – PVP and groups from 3rd to 5th NCS, in doses respectively, 0.1; 1.0 and 10 mg/kg body weight (b.w.) in terms of silver. The dose of PVP in groups from 2nd to 5th did not differ, amounting to 200 mg/kg b.w. During the experiment, the weight gain, skin condition, activity, stool, cognitive function were assessed. At the end of the feeding period weight of internal organs, intestinal wall permeability to protein macromolecules, liver thiols, standard values of blood erythrocytes, leukocytes and platelets, hepatocyte apoptosis by flow cytometry were studied. These results suggest that in terms of weight gain, lung relative mass, average erythrocyte volume, hemoglobin content and concentration in erythrocytes, the relative proportion of lymphocytes and neutrophils adverse changes have been observed at a dose of 10 mg NPs per kg of b.w. At lower levels of exposure (0.1 and 1.0 mg/kg b.w.) some specific changes were also observed (in terms of thiols pool in liver, cognitive function, relative abundance of monocytes, the number of dead hepatocytes), which, however, did not possess an unambiguous dependence on the dose. Possible mechanisms of the toxic action of the NCS have been discussed.

Vg mRNA induction in an endangered fish species (Anguilla anguilla) from the Loire estuary (France).

PubMed

Blanchet-Letrouvé, Isabelle; Lafont, Anne-Gaëlle; Poirier, Laurence; Baloche, Sylvie; Zalouk-Vergnoux, Aurore; Dufour, Sylvie; Mouneyrac, Catherine

2013-11-01

Estuarine zones are extremely fragile due to increasing stress from anthropogenic activities. Among those, the Loire estuary (France) is potentially exposed to various contaminants including Endocrine Disruptors Compounds (EDCs) able to impact the reproduction physiology of fish. The European eel (Anguilla anguilla), endangered fish species, is apparently not relevant, in its yellow stage, to monitor the effects of endocrine disruption. Despite this weakly responsiveness, this study aimed to investigate whether European eel from the Loire estuary may still be the subject of estrogenic disruption quantifying the hepatic Vg gene expression according to gender and sexual stage. Vitellogenin (Vg) appears as a valuable biomarker of EDCs, as well as for exposure and effects. Quantitative real-time Reverse Transcription Polymerase Chain Reaction (q RT PCR) was used in this study to amplify responses of hepatic Vg transcripts. European eels were sampled in May 2009 (N=57) and November 2010 (during the downstream migration, N=10) in two sites of the Loire estuary with different ecological conditions and contamination pressures (upstream: Varades; downstream: Nantes). Reproductive (gender, sexual maturity stage) and biometric parameters of collected eels were determined. A laboratory exposure of silver male to steroid hormones (Testosterone (T), 11-KetoTestosterone (11-KT), Estradiol (E2)) was conducted in parallel to validate the q RT PCR approach on hepatic Vg mRNA. Results demonstrated the responsiveness of exposed silver male eels, since hepatic mRNA Vg induction was observed in E2 treated males compared to control specimens. In the field, results of female silver eels reflected large inter-individual differences in the activation of hepatic Vg at silvering. However, while only female silver eels should express hepatic Vg mRNA, quantifiable levels were also detected in a proportion of 38% of the other individuals sampled, normally not inclined to express it, those being undifferentiated eels, yellow females, yellow and silver males. According to each sexual stage, no difference of expression was observed between eels from the two sampling sites. Histological results as well as low Vg mRNA levels detected do not permit a conclusion as to a potential effect of endocrine disruption. © 2013 Published by Elsevier Inc.

Interdisciplinary Research to Elucidate Mechanisms Governing Silver Nanoparticle Fate and Transport in Porous Media

NASA Astrophysics Data System (ADS)

Pennell, K. D.; Mittleman, A.; Taghavy, A.; Fortner, J.; Lantagne, D.; Abriola, L. M.

2014-12-01

Interdisciplinary Research to Elucidate Mechanisms Governing Silver Nanoparticle Fate and Transport in Porous Media Anjuliee M. Mittelman, Amir Taghavy, Yonggang Wang, John D. Fortner, Daniele S. Lantagne, Linda M. Abriola and Kurt D. Pennell* Detailed knowledge of the processes governing nanoparticle transport and reactivity in porous media is essential for accurate predictions of environmental fate, water and wastewater treatment system performance, and assessment of potential risks to ecosystems and water supplies. To address these issues, an interdisciplinary research team combined experimental and mathematical modeling studies to investigate the mobility, dissolution, and aging of silver nanoparticles (nAg) in representative aquifer materials and ceramic filters. Results of one-dimensional column studies, conducted with water-saturated sands maintained at pH 4 or 7 and three levels of dissolved oxygen (DO), revealed that fraction of silver mass eluted as Ag+ increased with increasing DO level, and that the dissolution of attached nAg decreased over time as a result of surface oxidation. A hybrid Eulerain-Lagragian nanoparticle transport model, which incorporates DO-dependent dissolution kinetics and particle aging, was able to accurately simulate nAg mobility and Ag+ release measured in the column experiments. Model sensitivity analysis indicated that as the flow velocity and particle size decrease, nAg dissolution and Ag+ transport processes increasingly govern silver mobility. Consistent results were obtained in studies of ceramic water filters treated with nAg, where silver elution was shown to be governed by nAg dissolution to form Ag+ and subsequent cation exchange reactions. Recent studies explored the effects of surface coating aging on nAg aggregation, mobility and dissolution. Following ultraviolet light, nAg retention in water saturated sand increased by 25-50%, while up to 50% of the applied mass eluted as Ag+ compared to less than 1% for un-aged nAg. In batch experiments, the addition of tert-butyl alcohol, a reactive oxygen species scavenger, reduced nAg aggregation and dissolution by up to 50%, indicating that free radical activity played an important role in the surface coating aging. Taken in concert, these findings demonstrate the value of undertaking

Interdisciplinary Research to Elucidate Mechanisms Governing Silver Nanoparticle Fate and Transport in Porous Media

NASA Astrophysics Data System (ADS)

Pennell, K. D.; Mittleman, A.; Taghavy, A.; Fortner, J.; Lantagne, D.; Abriola, L. M.

2015-12-01

Interdisciplinary Research to Elucidate Mechanisms Governing Silver Nanoparticle Fate and Transport in Porous Media Anjuliee M. Mittelman, Amir Taghavy, Yonggang Wang, John D. Fortner, Daniele S. Lantagne, Linda M. Abriola and Kurt D. Pennell* Detailed knowledge of the processes governing nanoparticle transport and reactivity in porous media is essential for accurate predictions of environmental fate, water and wastewater treatment system performance, and assessment of potential risks to ecosystems and water supplies. To address these issues, an interdisciplinary research team combined experimental and mathematical modeling studies to investigate the mobility, dissolution, and aging of silver nanoparticles (nAg) in representative aquifer materials and ceramic filters. Results of one-dimensional column studies, conducted with water-saturated sands maintained at pH 4 or 7 and three levels of dissolved oxygen (DO), revealed that fraction of silver mass eluted as Ag+ increased with increasing DO level, and that the dissolution of attached nAg decreased over time as a result of surface oxidation. A hybrid Eulerain-Lagragian nanoparticle transport model, which incorporates DO-dependent dissolution kinetics and particle aging, was able to accurately simulate nAg mobility and Ag+ release measured in the column experiments. Model sensitivity analysis indicated that as the flow velocity and particle size decrease, nAg dissolution and Ag+ transport processes increasingly govern silver mobility. Consistent results were obtained in studies of ceramic water filters treated with nAg, where silver elution was shown to be governed by nAg dissolution to form Ag+ and subsequent cation exchange reactions. Recent studies explored the effects of surface coating aging on nAg aggregation, mobility and dissolution. Following ultraviolet light, nAg retention in water saturated sand increased by 25-50%, while up to 50% of the applied mass eluted as Ag+ compared to less than 1% for un-aged nAg. In batch experiments, the addition of tert-butyl alcohol, a reactive oxygen species scavenger, reduced nAg aggregation and dissolution by up to 50%, indicating that free radical activity played an important role in the surface coating aging. Taken in concert, these findings demonstrate the value of undertaking

Evaluating the potential of gold, silver, and silica nanoparticles to saturate mononuclear phagocytic system tissues under repeat dosing conditions.

PubMed

Weaver, James L; Tobin, Grainne A; Ingle, Taylor; Bancos, Simona; Stevens, David; Rouse, Rodney; Howard, Kristina E; Goodwin, David; Knapton, Alan; Li, Xiaohong; Shea, Katherine; Stewart, Sharron; Xu, Lin; Goering, Peter L; Zhang, Qin; Howard, Paul C; Collins, Jessie; Khan, Saeed; Sung, Kidon; Tyner, Katherine M

2017-07-17

As nanoparticles (NPs) become more prevalent in the pharmaceutical industry, questions have arisen from both industry and regulatory stakeholders about the long term effects of these materials. This study was designed to evaluate whether gold (10 nm), silver (50 nm), or silica (10 nm) nanoparticles administered intravenously to mice for up to 8 weeks at doses known to be sub-toxic (non-toxic at single acute or repeat dosing levels) and clinically relevant could produce significant bioaccumulation in liver and spleen macrophages. Repeated dosing with gold, silver, and silica nanoparticles did not saturate bioaccumulation in liver or spleen macrophages. While no toxicity was observed with gold and silver nanoparticles throughout the 8 week experiment, some effects including histopathological and serum chemistry changes were observed with silica nanoparticles starting at week 3. No major changes in the splenocyte population were observed during the study for any of the nanoparticles tested. The clinical impact of these changes is unclear but suggests that the mononuclear phagocytic system is able to handle repeated doses of nanoparticles.

An evaluation of silver-stage American Eel conspecific chemical cueing during outmigration

USGS Publications Warehouse

Schmucker, Andrew K.; Johnson, Nicholas S.; Galbraith, Heather S.; Li, Weiming

2017-01-01

American Eel Anguilla rostrata abundance has declined in recent decades, in part because sexually maturing, silver-stage adults, outmigrating from freshwater to oceanic spawning grounds, encounter migratory blockades or perish when passing through active hydroelectric turbines. To help improve downstream passage effectiveness and increase survival rates, the role of silver-stage American Eel conspecific chemical cueing during outmigration was investigated using a new type of bioassay. Inside a laboratory flume, downstream-swimming eels were exposed to both live (putative attractant) and dead (putative repellent) conspecific washings to determine whether their trajectory of downstream movement, level of activity, or time spent inside targeted areas of the arena changed after exposure. Silver eels were not attracted to or repulsed by either odor, as none of five scoring metrics indicated a behavioral response. Results did not support the hypothesis that conspecific chemical cueing is a mechanism for downstream migration coordination or danger avoidance; however responses may not have been readily apparent in this type of assay. Fisheries managers may opt to focus future research on more feasible restoration efforts using alternate experimental designs to remedy this ecological issue.

Extraordinarily high conductivity of flexible adhesive films by hybrids of silver nanoparticle-nanowires

NASA Astrophysics Data System (ADS)

Muhammed Ajmal, C.; Mol Menamparambath, Mini; Ryeol Choi, Hyouk; Baik, Seunghyun

2016-06-01

Highly conductive flexible adhesive (CFA) film was developed using micro-sized silver flakes (primary fillers), hybrids of silver nanoparticle-nanowires (secondary fillers) and nitrile butadiene rubber. The hybrids of silver nanoparticle-nanowires were synthesized by decorating silver nanowires with silver nanoparticle clusters using bifunctional cysteamine as a linker. The dispersion in ethanol was excellent for several months. Silver nanowires constructed electrical networks between the micro-scale silver flakes. The low-temperature surface sintering of silver nanoparticles enabled effective joining of silver nanowires to silver flakes. The hybrids of silver nanoparticle-nanowires provided a greater maximum conductivity (54 390 S cm-1) than pure silver nanowires, pure multiwalled carbon nanotubes, and multiwalled carbon nanotubes decorated with silver nanoparticles in nitrile butadiene rubber matrix. The resistance change was smallest upon bending when the hybrids of silver nanoparticle-nanowires were employed. The adhesion of the film on polyethylene terephthalate substrate was excellent. Light emitting diodes were successfully wired to the CFA circuit patterned by the screen printing method for application demonstration.

Catalytic potential of bio-synthesized silver nanoparticles using Convolvulus arvensis extract for the degradation of environmental pollutants.

PubMed

Rasheed, Tahir; Bilal, Muhammad; Li, Chuanlong; Nabeel, Faran; Khalid, Muhammad; Iqbal, Hafiz M N

2018-04-01

Herein, we reported a facile, green and environmental friendlier biosynthesis of silver nanoparticles using the Convolvulus arvensis extract. The influences of various physicochemical factors such as the concentration of the plant extract, reaction time, and different pH levels were investigated by UV-Vis spectroscopy. The UV-Visible absorption spectrum of biogenic silver nanoparticles at λ max around ~400 nm suggested the biosynthesis of silver nanoparticles. Fourier transform infrared spectroscopy was employed to confirm the chemical transformation and role of various phyto-reductants in the conversion of Ag + to Ag 0 . The surface morphology, topography, and elemental composition were analyzed by scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy, respectively. X-ray diffraction corroborated the face-centered cubic crystalline structure. The dynamic light scattering and zeta potential demonstrate the size distribution (90.9 nm) and surface charge (-18.5). Finally, the newly developed C. arvensis based silver nanoparticles were exploited as a catalyst for the catalytic reduction of azo dyes in the presence of NaBH 4 as a reducing agent, and reducing the activity of C. arvensis based silver nanoparticles was evaluated by a decrease in optical density using UV-Vis spectrophotometer. The nanoparticles developed herein displayed potential efficiency for the degradation of all the tested dye pollutants. Conclusively, plant-based synthesis of nanoparticles provides an environmentally-responsive option for the reduction of highly environmental-polluted organic compounds including toxic azo dyes as compared to chemical and physical methods. Copyright © 2018 Elsevier B.V. All rights reserved.

Silver-nanoparticle-coated biliary stent inhibits bacterial adhesion in bacterial cholangitis in swine.

PubMed

Wen, Wei; Ma, Li-Mei; He, Wei; Tang, Xiao-Wei; Zhang, Yin; Wang, Xiang; Liu, Li; Fan, Zhi-Ning

2016-02-01

One of the major limitations of biliary stents is the stent occlusion, which is closely related to the over-growth of bacteria. This study aimed to evaluate the feasibility of a novel silver-nanoparticle-coated polyurethane (Ag/PU) stent in bacterial cholangitis model in swine. Ag/PU was designed by coating silver nanoparticles on polyurethane (PU) stent. Twenty-four healthy pigs with bacterial cholangitis using Ag/PU and PU stents were randomly divided into an Ag/PU stent group (n=12) and a PU stent group (n=12), respectively. The stents were inserted by standard endoscopic retrograde cholangiopancreatography. Laboratory assay was performed for white blood cell (WBC) count, alanine aminotransferase (ALT), interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha) at baseline time, 8 hours, 1, 2, 3, and 7 days after stent placements. The segment of bile duct containing the stent was examined histologically ex vivo. Implanted biliary stents were examined by a scan electron microscope. The amount of silver release was also measured in vitro. The number of inflammatory cells and level of ALT, IL-1beta and TNF-alpha were significantly lower in the Ag/PU stent group than in the PU stent group. Hyperplasia of the mucosa was more severe in the PU stent group than in the Ag/PU stent group. In contrast to the biofilm of bacteria on the PU stent, fewer bacteria adhered to the Ag/PU stent. PU biliary stents modified with silver nanoparticles are able to alleviate the inflammation of pigs with bacterial cholangitis. Silver-nanoparticle-coated stents are resistant to bacterial adhesion.

Citrate coated silver nanoparticles with modulatory effects on aflatoxin biosynthesis in Aspergillus parasiticus

NASA Astrophysics Data System (ADS)

Mitra, Chandrani

The manufacture and usage of silver nanoparticles has drastically increased in recent years (Fabrega et al. 2011a). Hence, the levels of nanoparticles released into the environment through various routes have measurably increased and therefore are concern to the environment and to public health (Panyala, Pena-Mendez and Havel 2008). Previous studies have shown that silver nanoparticles are toxic to various organisms such as bacteria (Kim et al. 2007), fungi (Kim et al. 2008), aquatic plants (He, Dorantes-Aranda and Waite 2012a), arthropods (Khan et al. 2015), and mammalian cells (Asharani, Hande and Valiyaveettil 2009) etc. Most of the toxicity studies are carried out using higher concentrations or lethal doses of silver nanoparticles. However, there is no information available on how the fungal community reacts to the silver nanoparticles at nontoxic concentrations. In this study, we have investigated the effect of citrate coated silver nanoparticles (AgNp-cit) at a size of 20nm on Aspergillus parasiticus, a popular plant pathogen and well-studied model for secondary metabolism (natural product synthesis). A. parasiticus produces 4 major types of aflatoxins. Among other aflatoxins, aflatoxin B1 is considered to be one of most potent naturally occurring liver carcinogen, and is associated with an estimated 155,000 liver cancer cases globally (Liu and Wu 2010); therefore, contaminated food and feed are a significant risk factor for liver cancer in humans and animals (CAST 2003; Liu and Wu 2010). In this study, we have demonstrated the uptake of AgNp-cit (20nm) by A. parasiticus cells from the growth medium using a time course ICP-OES experiment. It was observed that the uptake of AgNp-cit had no effect on fungal growth and significantly decreased intracellular oxidative stress. It also down-regulated aflatoxin biosynthesis at the level of gene expression of aflatoxin pathway genes and the global regulatory genes of secondary metabolism. We also observed that the fungus successfully reverts its aflatoxin biosynthesis to normal levels once the level of AgNp-cit decreased significantly in the growth medium. A stability study of AgNp-cit in the fungal growth medium, along with mycelia, was conducted using UV-vis spectroscopy. The result showed that the distinctive peak (at 395nm wavelength) of silver nanoparticles, size of 20nm, shifted to a higher wavelength (400nm-500nm), broadened, and decreased over time. At 30-hour post inoculation the UV-vis peak at 395 nm wavelength was not observed at all. The peak shifts may occur due to organic molecules from the medium replacing the citrate surface coating. Another possible explanation for the peak shift are the interactions between the surface coating and other inorganic components in the medium. Peak broadening may suggest possible aggregation or formation of corona on the surface of AgNp due to particle-protein interactions (leading to AgNp aggregation in the growth medium). Reduction of peak height may suggest nanoparticle uptake by the mycelia, dissolution of nanoparticles into charged ions as well as possible interaction with other ions in the growth medium or the formation of precipitate of silver salt. We have investigated effects of different sizes (15 nm, 20 nm, and 30 nm) of AgNp-cit and pvp coated silver nanoparticles (AgNp-pvp (20 nm)) on growth and aflatoxin B1 biosynthesis in A. parasiticus. AgNp-cit size of 15nm showed maximum aflatoxin inhibition at 25ng/mL. For 20nm and 30nm AgNp-cit the strongest aflatoxin inhibition was observed at 50ng/mL concentration. The aflatoxin inhibitory effect was also found to be AgNp coating dependent. For 20nm AgNp-cit the strongest aflatoxin inhibition was seen at 50ng/mL (calculated) while for 20nm AgNp-pvp, the maximum aflatoxin inhibition was observed at 60ng/mL (calculated) concentration. Acute toxicity of silver nanoparticles on various organisms are well-studied but large knowledge gap still exist on the assessment of its chronic toxicity at low concentrations. Our study suggested that at low concentrations (ng/mL) AgNp still can produce biological effects on fungal cells. Further understanding of AgNp induced biological effects at low concentrations/environmentally relevant concentrations is necessary in investigating the environmental health effects.

Photochemical Study of Silver Nanoparticles Formed from the Reduction of Silver Ions by Humic Acid

NASA Astrophysics Data System (ADS)

Leslie, Renee M.

This study focuses on the ability of silver ions and humic acid to form silver nanoparticles in the presence of UV and visible light. Silver nanoparticles have a number of industrial applications due primarily to their antimicrobial properties, but these properties pose an environmental threat. Silver nanoparticles can directly disrupt sensitive ecosystems by harming bacteria. Consumption of silver nanoparticles results in silver ions and silver nanoparticles entering waterways; the presence of silver ions raises the question of whether nanoparticles can reform in environmental waters. As our data show, silver nanoparticles can form from the reduction of silver ions by humic acid after irradiation with UV and visible light. In order to better understand the mechanism of these naturally synthesized silver nanoparticles, we investigated the effects of reactant concentration, experimental conditions and presence of ions/reactive species. We monitored silver nanoparticle growth with UV-visible spectroscopy. The evolution in time of nanoparticle size was monitored by dynamic light scattering (DLS).

Noble metal superparticles and methods of preparation thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yugang; Hu, Yongxing

A method comprises heating an aqueous solution of colloidal silver particles. A soluble noble metal halide salt is added to the aqueous solution which undergoes a redox reaction on a surface of the silver particles to form noble metal/silver halide SPs, noble metal halide/silver halide SPs or noble metal oxide/silver halide SPs on the surface of the silver particles. The heat is maintained for a predetermined time to consume the silver particles and release the noble metal/silver halide SPs, the noble metal halide/silver halide SPs or the noble metal oxide/silver halide SPs into the aqueous solution. The aqueous solution ismore » cooled. The noble metal/silver halide SPs, the noble metal halide/silver halide SPs or noble metal oxide/silver halide SPs are separated from the aqueous solution. The method optionally includes adding a soluble halide salt to the aqueous solution.« less

Immunocytolocalization of extensin in developing soybean seed coats by immunogold-silver staining and by tissue printing on nitrocellulose paper

PubMed Central

1987-01-01

In soybean seed coats the accumulation of the hydroxyproline-rich glycoprotein extensin is regulated in a developmental and tissue- specific manner. The time course of appearance of extensin during seed development was studied by Western blot analysis and by immunogold- silver localization. Using these techniques extensin was first detected at 16-18 d after anthesis, increasing during development to high levels at 24 d after anthesis. Immunogold-silver localization of extensin in the seed coat showed marked deposition of the glycoprotein in the walls of palisade epidermal cells and hourglass cells. The immunolocalization of extensin in developing soybean seeds was also made by a new technique--tissue printing on nitrocellulose paper. It was found that extensin is primarily localized in the seed coat, hilum, and vascular elements of the seed. PMID:3693394

Acute and Subacute Toxicity In Vivo of Thermal-Sprayed Silver Containing Hydroxyapatite Coating in Rat Tibia

PubMed Central

Tsukamoto, Masatsugu; Miyamoto, Hiroshi; Ando, Yoshiki; Eto, Shuichi; Akiyama, Takayuki; Yonekura, Yutaka; Mawatari, Masaaki

2014-01-01

To reduce the incidence of implant-associated infection, we previously developed a novel coating technology using hydroxyapatite (HA) containing silver (Ag). This study examined in vivo acute and subacute toxicity associated with the Ag-HA coating in rat tibiae. Ten-week-old rats received implantation of HA-, 2% Ag-HA-, or 50% Ag-HA-coated titanium rods. Concentrations of silver in serum, brain, liver, kidneys, and spleen were measured in the acute phase (2–4 days after treatment) and subacute phase (4–12 weeks after treatment). Biochemical and histological examinations of those organs were also performed. Mean serum silver concentration peaked in the acute phase and then gradually decreased. Mean silver concentrations in all examined organs from the 2% Ag-HA coating groups showed no significant differences compared with the HA coating group. No significant differences in mean levels of glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, lactate dehydrogenase, creatinine, or blood urea nitrogen were seen between the three groups and controls. Histological examinations of all organs revealed no abnormal pathologic findings. No acute or subacute toxicity was seen in vivo for 2% Ag-HA coating or HA coating. Ag-HA coatings on implants may represent biologically safe antibacterial biomaterials and may be of value for reducing surgical-site infections related to implantation. PMID:24779019

Silver nanoparticles embedded in zeolite membranes: release of silver ions and mechanism of antibacterial action

PubMed Central

Nagy, Amber; Harrison, Alistair; Sabbani, Supriya; Munson, Robert S; Dutta, Prabir K; Waldman, W James

2011-01-01

Background The focus of this study is on the antibacterial properties of silver nanoparticles embedded within a zeolite membrane (AgNP-ZM). Methods and Results These membranes were effective in killing Escherichia coli and were bacteriostatic against methicillin-resistant Staphylococcus aureus. E. coli suspended in Luria Bertani (LB) broth and isolated from physical contact with the membrane were also killed. Elemental analysis indicated slow release of Ag+ from the AgNP-ZM into the LB broth. The E. coli killing efficiency of AgNP-ZM was found to decrease with repeated use, and this was correlated with decreased release of silver ions with each use of the support. Gene expression microarrays revealed upregulation of several antioxidant genes as well as genes coding for metal transport, metal reduction, and ATPase pumps in response to silver ions released from AgNP-ZM. Gene expression of iron transporters was reduced, and increased expression of ferrochelatase was observed. In addition, upregulation of multiple antibiotic resistance genes was demonstrated. The expression levels of multicopper oxidase, glutaredoxin, and thioredoxin decreased with each support use, reflecting the lower amounts of Ag+ released from the membrane. The antibacterial mechanism of AgNP-ZM is proposed to be related to the exhaustion of antioxidant capacity. Conclusion These results indicate that AgNP-ZM provide a novel matrix for gradual release of Ag+. PMID:21931480

Effect of gelatin sponge with colloid silver on bone healing in infected cranial defects.

PubMed

Dong, Yuliang; Liu, Weiqing; Lei, Yiling; Wu, Tingxi; Zhang, Shiwen; Guo, Yuchen; Liu, Yuan; Chen, Demeng; Yuan, Quan; Wang, Yongyue

2017-01-01

Oral infectious diseases may lead to bone loss, which makes it difficult to achieve satisfactory restoration. The rise of multidrug resistant bacteria has put forward severe challenges to the use of antibiotics. Silver (Ag) has long been known as a strong antibacterial agent. In clinic, gelatin sponge with colloid silver is used to reduce tooth extraction complication. To investigate how this material affect infected bone defects, methicillin-resistant Staphylococcus aureus (MRSA) infected 3-mm-diameter cranial defects were created in adult female Sprague-Dawley rats. One week after infection, the defects were debrided of all nonviable tissue and then implanted with gelatin sponge with colloid silver (gelatin/Ag group) or gelatin alone (gelatin group). At 2 and 3days after debridement, significantly lower mRNA expression levels of IL-6 and TNF-α and lower plate colony count value were detected in gelatin/Ag group than control. Micro-CT analysis showed a significant increase of newly formed bone volume fraction (BV/TV) in gelatin/Ag treated defects. The HE stained cranium sections also showed a faster rate of defect closure in gelatin/Ag group than control. These findings demonstrated that gelatin sponge with colloid silver can effectively reduce the infection caused by MRSA in cranial defects and accelerate bone healing process. Copyright © 2016. Published by Elsevier B.V.

Silver-loaded seaweed-based cellulosic fiber improves epidermal skin physiology in atopic dermatitis: safety assessment, mode of action and controlled, randomized single-blinded exploratory in vivo study.

PubMed

Fluhr, Joachim W; Breternitz, Maria; Kowatzki, Doreen; Bauer, Andrea; Bossert, Joerg; Elsner, Peter; Hipler, Uta-Christina

2010-08-01

The epidermal part of the skin is the major interface between the internal body and the external environment. The skin has a specific physiology and is to different degrees adapted for protection against multiple exogenous stress factors. Clothing is the material with the longest and most intensive contact to human skin. It plays a critical role especially in inflammatory dermatoses or skin conditions with an increased susceptibility of bacterial and fungal infections like atopic dermatitis. Previously, we have shown a dose-dependent antibacterial and antifungal activity of silver-loaded seaweed-based cellulosic fibres. We studied the mode of action of silver-loaded seaweed-based cellulosic fiber and performed a broad safety assessment. The principal aim was to analyse the effects of wearing the textile on epidermal skin physiology in 37 patients with atopic dermatitis in a controlled, randomized single-blinded in vivo study. Furthermore, the sensitization potential was tested in a patch test in 111 panellists. We could demonstrate in vitro a dose-dependent scavenging of induced reactive oxygen species by silver-loaded seaweed-based cellulosic fibers. Safety assessment of these fibres showed no detectable release of silver ions. Furthermore, ex vivo assessment after 24 h application both in healthy volunteers and patients with atopic dermatitis by sequential tape stripping and subsequently raster electron microscopy and energy dispersive microanalysis analysis revealed no detectable amounts of silver in any of stratum corneum layers. Serum analysis of silver showed no detectable levels. The in vivo patch testing of 111 volunteers revealed no sensitization against different SeaCell Active (SeaCell GmbH, Rudolstadt, Germany) containing fabrics. The in vivo study on 37 patients with known atopic dermatitis and mild-to-moderate eczema on their arms were randomly assigned to either silver-loaded seaweed fibre T-shirts or to cotton T-shirts for 8 weeks. A significant reduction in Staphylococcus aureus colonization was detectable for the silver T-shirts compared with cotton T-shirts without any changes in non-pathogenic surface bacteria colonization. Furthermore, a more pronounced improvement in barrier function (transepidermal water loss) was observed in mildly involved eczema areas during the first 4 weeks of the study. Stratum corneum hydration and surface pH improved in both treatment groups over time. The tested silver-loaded seaweed fibre can be regarded as safe and seams to be suited for application in bio-active textiles in atopic dermatitis based on its positive in vivo activity.

Low molecular weight chitosan-coated silver nanoparticles are effective for the treatment of MRSA-infected wounds.

PubMed

Peng, Yinbo; Song, Chenlu; Yang, Chuanfeng; Guo, Qige; Yao, Min

2017-01-01

Silver nanoparticles (AgNPs) are being widely applied as topical wound materials; however, accumulated deposition of silver in the liver, spleen, and other main organs may lead to organ damage and dysfunction. We report here that low molecular weight chitosan-coated silver nanoparticles (LMWC-AgNPs) are effective against methicillin-resistant Staphylococcus aureus (MRSA), have better biocompatibility, and have lower body absorption characteristics when compared with polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) and silver nanoparticles without surface stabilizer (uncoated-AgNPs) in a dorsal MRSA wound infection mouse model. LMWC-AgNPs were synthesized by reducing silver nitrate with low molecular weight chitosan as a stabilizer and reducing agent, while PVP-AgNPs were synthesized using polyvinylpyrrolidone as a stabilizer and ethanol as a reducing agent. AgNPs with different surface stabilizers were identified by UV-visible absorption spectrometry, and particle size was determined by transmission electron microscopy. UV-visible absorption spectra of LMWC-AgNPs, PVP-AgNPs and uncoated-AgNPs were similar and their sizes were in the range of 10-30 nm. In vitro experiments showed that the three types of AgNPs had similar MRSA-killing effects, with obvious effect at 4 μg/mL and 100% effect at 8 μg/mL. Bacteriostatic annulus experiments also showed that all the three types of AgNPs had similar antibacterial inhibitory effect at 10 μg/mL. Cell counting kit-8 assay and Hoechst/propidium iodide (PI) staining showed that LMWC-AgNPs were significantly less toxic to human fibroblasts than PVP-AgNPs and uncoated-AgNPs. Treatment of mice with MRSA wound infection demonstrated that the three types of AgNPs effectively controlled MRSA wound infection and promoted wound healing. After continuous application for 14 days, LMWC-AgNPs-treated mice showed significantly reduced liver dysfunction as demonstrated by the reduced alanine aminotransferase and aspartate aminotransferase levels and liver deposition of silver, in comparison to mice treated with uncoated-AgNPs or PVP-AgNPs. Our results demonstrated that LMWC-AgNPs had good anti-MRSA effects, while harboring a better biocompatibility and lowering the body's absorption characteristics.

The Empirical Formula of Silver Sulfide: An Experiment for Introductory Chemistry

ERIC Educational Resources Information Center

Trujillo, Carlos Alexander

2007-01-01

An experiment is described that allows students to experimentally determine an empirical formula for silver sulfide. At elevated temperatures, silver sulfide reacts in air to form silver, silver sulfate, and sulfur dioxide. At higher temperatures (960 [degree]C) silver sulfate decomposes to produce metallic silver. (Contains 1 figure and 1 table.)

Factors influencing the preparation of silver-coated glass frit with polyvinyl-pyrrolidone

NASA Astrophysics Data System (ADS)

Xiang, Feng; Gan, Weiping

2018-01-01

In this work, a new electroless silver plating method for the synthesis of silver-coated glass frit composite powders with good morphology has been proposed and the polyvinyl-pyrrolidone (PVP) was used the activating agent. It was found that the weight ratio of PVP to glass frit affected the distribution and number of silver nanoparticles. Moreover, the loading capacity of the glass frit, the pH value and reaction temperature could influence the size of the silver nanoparticles and morphology of silver on the surface of glass frit. The as-prepared silver-coated glass frit was used to prepare a silver paste using an optimized process to form silver nanoparticles with uniform size and high density. The silver paste with silver-coated glass frit increased the photovoltaic conversion efficiency of silicon solar cells by 0.271% compared with the silver paste prepared with pure glass frit. The silver nanoparticles can promoted the precipitation of Ag crystallites on the silicon wafer. Therefore, the silver-coated glass frit can further optimize and enhance the electrical performance of solar cells.

Method for the recovery of silver from silver zeolite

DOEpatents

Reimann, G.A.

1985-03-05

High purity silver is recovered from silver exchanged zeolite used to capture radioactive iodine from nuclear reactor and nuclear fuel reprocessing environments. The silver exchanged zeolite is heated with slag formers to melt and fluidize the zeolite and release the silver, the radioactivity removing with the slag. The silver containing metallic impurities is remelted and treated with oxygen and a flux to remove the metal impurities. About 98% of the silver in the silver exchanged zeolite having a purity of 99% or better is recoverable by the method.

Method for the recovery of silver from silver zeolite

DOEpatents

Reimann, George A.

1986-01-01

High purity silver is recovered from silver exchanged zeolite used to capture radioactive iodine from nuclear reactor and nuclear fuel reprocessing environments. The silver exchanged zeolite is heated with slag formers to melt and fluidize the zeolite and release the silver, the radioactivity removing with the slag. The silver containing metallic impurities is remelted and treated with oxygen and a flux to remove the metal impurities. About 98% of the silver in the silver exchanged zeolite having a purity of 99% or better is recoverable by the method.

Glass frits coated with silver nanoparticles for silicon solar cells

NASA Astrophysics Data System (ADS)

Li, Yingfen; Gan, Weiping; Zhou, Jian; Li, Biyuan

2015-06-01

Glass frits coated with silver nanoparticles were prepared by electroless plating. Gum Arabic (GA) was used as the activating agent of glass frits without the assistance of stannous chloride or palladium chloride. The silver-coated glass frits prepared with different GA dosages were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermogravimetric analysis (TGA). The characterization results indicated that silver-coated glass frits had the structures of both glass and silver. Spherical silver nanoparticles were distributed on the glass frits evenly. The density and particle size of silver nanoparticles on the glass frits can be controlled by adjusting the GA dosage. The silver-coated glass frits were applied to silver pastes to act as both the densification promoter and silver crystallite formation aid in the silver electrodes. The prepared silver-coated glass frits can improve the photovoltaic performances of solar cells.

Silver(II) Oxide or Silver(I,III) Oxide?

ERIC Educational Resources Information Center

Tudela, David

2008-01-01

The often called silver peroxide and silver(II) oxide, AgO or Ag[subscript 2]O[subscript 2], is actually a mixed oxidation state silver(I,III) oxide. A thermochemical cycle, with lattice energies calculated within the "volume-based" thermodynamic approach, explain why the silver(I,III) oxide is more stable than the hypothetical silver(II) oxide.…

Use of a modified GreenScreen tool to conduct a screening-level comparative hazard assessment of conventional silver and two forms of nanosilver.

PubMed

Sass, Jennifer; Heine, Lauren; Hwang, Nina

2016-11-08

Increased concern for potential health and environmental impacts of chemicals, including nanomaterials, in consumer products is driving demand for greater transparency regarding potential risks. Chemical hazard assessment is a powerful tool to inform product design, development and procurement and has been integrated into alternative assessment frameworks. The extent to which assessment methods originally designed for conventionally-sized materials can be used for nanomaterials, which have size-dependent physical and chemical properties, have not been well established. We contracted with a certified GreenScreen profiler to conduct three GreenScreen hazard assessments, for conventional silver and two forms of nanosilver. The contractor summarized publicly available literature, and used defined GreenScreen hazard criteria and expert judgment to assign and report hazard classification levels, along with indications of confidence in those assignments. Where data were not available, a data gap (DG) was assigned. Using the individual endpoint scores, an aggregated benchmark score (BM) was applied. Conventional silver and low-soluble nanosilver were assigned the highest possible hazard score and a silica-silver nanocomposite called AGS-20 could not be scored due to data gaps. AGS-20 is approved for use as antimicrobials by the US Environmental Protection Agency. An existing method for chemical hazard assessment and communication can be used - with minor adaptations- to compare hazards across conventional and nano forms of a substance. The differences in data gaps and in hazard profiles support the argument that each silver form should be considered unique and subjected to hazard assessment to inform regulatory decisions and decisions about product design and development. A critical limitation of hazard assessments for nanomaterials is the lack of nano-specific hazard data - where data are available, we demonstrate that existing hazard assessment systems can work. The work is relevant for risk assessors and regulators. We recommend that regulatory agencies and others require more robust data sets on each novel nanomaterial before granting market approval.

Inkjet deposited circuit components

NASA Astrophysics Data System (ADS)

Bidoki, S. M.; Nouri, J.; Heidari, A. A.

2010-05-01

All-printed electronics as a means of achieving ultra-low-cost electronic circuits has attracted great interest in recent years. Inkjet printing is one of the most promising techniques by which the circuit components can be ultimately drawn (i.e. printed) onto the substrate in one step. Here, the inkjet printing technique was used to chemically deposit silver nanoparticles (10-200 nm) simply by ejection of silver nitrate and reducing solutions onto different substrates such as paper, PET plastic film and textile fabrics. The silver patterns were tested for their functionality to work as circuit components like conductor, resistor, capacitor and inductor. Different levels of conductivity were achieved simply by changing the printing sequence, inks ratio and concentration. The highest level of conductivity achieved by an office thermal inkjet printer (300 dpi) was 5.54 × 105 S m-1 on paper. Inkjet deposited capacitors could exhibit a capacitance of more than 1.5 nF (parallel plate 45 × 45 mm2) and induction coils displayed an inductance of around 400 µH (planar coil 10 cm in diameter). Comparison of electronic performance of inkjet deposited components to the performance of conventionally etched items makes the technique highly promising for fabricating different printed electronic devices.

Surface enhanced Raman scattering (SERS) spectra of trinitrotoluene in silver colloids prepared by microwave heating method.

PubMed

Zhang, Chunling; Wang, Kaijun; Han, Dejun; Pang, Qing

2014-03-25

Surface enhanced Raman spectroscopy (SERS) has been demonstrated for the detection of trace levels of explosives due to its high sensitivity, speed of detection and fingerprint feature. 2,4,6-Trinitrotoluene (TNT), a leading example of nitroaromatic explosives, is causing wide concern. In this study, SERS spectra of TNT solution in silver colloids have been successfully measured and a comparison was drawn with the normal Raman spectra of bulk TNT. The silver colloids were prepared by the microwave heating method and characterized by UV-Vis spectra and the scanning electron microscopy (SEM). NaCl and pH value have a great impact on SERS intensity of TNT, the corresponding experimental research results and theoretical interpretations were further illustrated to a certain extent. Moreover, the detection limit of TNT in aqueous solution was achieved as low as 10(-10) mol L(-1) and some preliminary experiments of detecting TNT vapor (about 10 μg/L) using SERS have been carried out. Our results demonstrated the potential of SERS for probing TNT with high sensitivity, and suggest SERS as a powerful method for detection of TNT and similar species at trace levels. Copyright © 2013 Elsevier B.V. All rights reserved.

Spatial and temporal influences on the physiological condition of invasive silver carp.

PubMed

Liss, Stephanie A; Sass, Greg G; Suski, Cory D

2013-01-01

We quantified nutritional and stress parameters (alkaline phosphatase, cholesterol, protein, triglycerides, cortisol, and glucose) in invasive silver carp (Hypophthalmichthys molitrix) inhabiting four large rivers throughout three distinct time periods in the Midwestern USA. Examining the basic biology and ecology of an invasive species is crucial to gain an understanding of the interaction between an organism and its environment. Analysis of the physiological condition of wild-caught silver carp across broad spatial and temporal scales is essential because stress and nutritional parameters can link individuals to their habitats and vary among populations across environments. During each time period, we collected blood samples from individual silver carp in the Illinois River and portions of the Mississippi, Ohio, and Wabash rivers in Illinois. We tested for relationships between silver carp nutrition and stress across rivers, reaches within rivers, and time periods. Principal component analyses separated physiological parameters into a stress component (cortisol and glucose) and two nutritional components representative of short-term feeding (alkaline phosphatase, protein, and triglycerides) and body energy reserves (cholesterol and protein). Akaike's information criterion suggested that time period had the greatest influence on stress. Stress levels were consistent in all four rivers, and declined across time periods. Akaike's information criterion also suggested that interactions of time period and river had the greatest influence on short-term feeding and body energy reserves. There was no specific pattern across time periods within each river, nor was there a pattern across rivers. Our results provide a better understanding of nutritional and stress conditions in invasive silver carp across a broad landscape and temporal scale, with implications for managing and predicting the spread of this species.

Cloning of cytochrome P450 3A137 complementary DNA in silver carp and expression induction by ionic liquid.

PubMed

Li, Xiaoyu; Ma, Junguo; Lei, Wenlong; Li, Jie; Zhang, Yaning; Li, Yuanlong

2013-08-01

Cytochrome P450 (CYP) enzymes, especially CYP 3A, are responsible for metabolizing of various kinds of endogenous and exogenous compounds in animals. In the present study, a full-length sequence of CYP 3A137 cDNA in silver carp was cloned and sequenced, and then a phylogenetic tree of CYP 3A was structured. Additionally, the acute toxicity of the ionic liquid 1-octyl-3-methylimidazolium bromide ([C8mim]Br) on silver carp and transcription and microsome enzyme activity of CYP 3A137 in the liver of silver fish after rifampicin or [C8mim]Br exposure were also determined in this study. The results show that the full length of CYP 3A137 cDNA is 1810 base pair (bp) long and contains an open reading frame of 1539bp encoding a protein of 513 amino acids. Sequence analysis reveals that CYP 3A137 is highly conserved in fish. Moreover, the results of quantitative real-time polymerase chain reaction reveal that CYP 3A137 in silver carp is constitutively expressed in all tissues examined and the sequence of expression rate is liver>intestine>kidney>spleen>brain>heart>muscle. Finally, the results of acute toxicity tests indicate that both rifampicin and [C8mim]Br significantly up-regulate the expression of CYP 3A137 at mRNA level and increase CYP 3A137 enzyme activity in fish liver, suggesting that CYP 3A137 be involved in metabolism of [C8mim]Br in silver carp. Copyright © 2013 Elsevier Ltd. All rights reserved.

Variations in anthropogenic silver in a large Patagonian lake correlate with global shifts in photographic processing technology.

PubMed

Juncos, Romina; Campbell, Linda; Arcagni, Marina; Daga, Romina; Rizzo, Andrea; Arribére, María; Ribeiro Guevara, Sergio

2017-04-01

At the beginning of the 21st century, digital imaging technology replaced the traditional silver-halide film photography which had implications in Ag contamination. Lake Nahuel Huapi is a popular Patagonia tourist destination impacted by municipal silver (Ag) contamination from photographic processing facilities since 1990's. Silver concentrations in a dated sediment core from the lake bottom showed a 10-fold increase above background levels in the second half of the 20th century, then a decrease. This trend corresponds well with published annual global photography industry demand for Ag, which clearly shows the evolution and replacement of the traditional silver-halide film photography by digital imaging technology. There were significant decreases in Ag concentrations in sediments, mussels and fish across the lake between 1998 and 2011. Lower trophic organisms had variable whole-body Ag concentrations, from 0.2-2.6 μg g -1 dry weight (DW) in plankton to 0.02-3.1 μg g -1 DW in benthic macroinvertebrates. Hepatic Ag concentrations in crayfish, mussels and predatory fish were significantly elevated relative to muscle which often have Ag concentrations below the detection limit (0.01-0.05 μg g -1 DW). Trophodynamic analyses using δ 15 N and whole-body invertebrate and muscle Ag concentrations indicated food web biodilution trends. High sedimentation rates in conjunction with the reduction of silver waste products discharged to the lake, as a result of the change to digital image processing technologies, are resulting in unplanned but welcome remediation of the Ag contamination in Lake Nahuel Huapi. Copyright © 2017 Elsevier Ltd. All rights reserved.

Acute toxicity, bioaccumulation and effects of dietary transfer of silver from brine shrimp exposed to PVP/PEI-coated silver nanoparticles to zebrafish.

PubMed

Lacave, José María; Fanjul, Álvaro; Bilbao, Eider; Gutierrez, Nerea; Barrio, Irantzu; Arostegui, Inmaculada; Cajaraville, Miren P; Orbea, Amaia

2017-09-01

The extensive use and release to the aquatic environment of silver nanoparticles (NPs) could lead to their incorporation into the food web. Brine shrimp larvae of 24h showed low sensitivity to the exposure to PVP/PEI-coated Ag NPs (5nm), with EC 50 values at 24h of 19.63mgAgL -1 , but they significantly accumulated silver after 24h of exposure to 100μgL -1 of Ag NPs. Thus, to assess bioaccumulation and effects of silver transferred by the diet in zebrafish, brine shrimp larvae were exposed to 100ngL -1 of Ag NPs as an environmentally relevant concentration or to 100μgL -1 as a potentially effective concentration and used to feed zebrafish for 21days. Autometallography revealed a dose- and time-dependent metal accumulation in the intestine and in the liver of zebrafish. Three-day feeding with brine shrimps exposed to 100ngL -1 of Ag NPs was enough to impair fish health as reflected by the significant reduction of lysosomal membrane stability and the presence of vacuolization and necrosis in the liver. However, dietary exposure to 100μgL -1 of Ag NPs for 3days did not significantly alter gene transcription levels, neither in the liver nor in the intestine. After 21days, biological processes such as lipid transport and localization, cellular response to chemical stimulus and response to xenobiotic stimulus were significantly altered in the liver. Overall, these results indicate an effective dietary transfer of silver and point out to liver as the main target organ for Ag NP toxicity in zebrafish after dietary exposure. Copyright © 2017 Elsevier Inc. All rights reserved.

Process for making silver metal filaments

DOEpatents

Bamberger, Carlos E.

1997-01-01

A process for making silver metal particles from silver salt particles having the same morphology. Precursor silver salt particles selected from the group consisting of silver acetate and silver sulfide having a selected morphology are contained in a reactor vessel having means for supporting the particles in an air suspension to prevent the agglomeration of the particles. Air is flowed through the reactor vessel at a flow rate sufficient to suspend the particles in the reactor vessel. The suspended precursor silver salt particles are heated to a processing temperature and at a heating rate below which the physical deterioration of the suspended precursor silver salt particles takes place. The suspended precursor silver salt particles are maintained at the processing temperature for a period of time sufficient to convert the particles into silver metal particles having the same morphology as the precursor silver salt particles.

Room temperature synthesis of silver nanowires from tabular silver bromide crystals in the presence of gelatin

NASA Astrophysics Data System (ADS)

Liu, Suwen; Wehmschulte, Rudolf J.; Lian, Guoda; Burba, Christopher M.

2006-03-01

Long silver nanowires were synthesized at room temperature by a simple and fast process derived from the development of photographic films. A film consisting of an emulsion of tabular silver bromide grains in gelatin was treated with a photographic developer (4-(methylamino)phenol sulfate (metol), citric acid) in the presence of additional aqueous silver nitrate. The silver nanowires have lengths of more than 50 μm, some even more than 100 μm, and average diameters of about 80 nm. Approximately, 70% of the metallic silver formed in the reduction consists of silver nanowires. Selected area electron diffraction (SAED) results indicate that the silver nanowires grow along the [111] direction. It was found that the presence of gelatin, tabular silver bromide crystals and silver ions in solution are essential for the formation of the silver nanowires. The nanowires appear to originate from the edges of the silver bromide crystals. They were characterized by transmission electron microscopy (TEM), SAED, scanning electron microscopy (SEM), and powder X-ray diffraction (XRD).

DNA-Templated Molecular Silver Fluorophores

PubMed Central

Petty, Jeffrey T.; Story, Sandra P.; Hsiang, Jung-Cheng; Dickson, Robert M.

2013-01-01

Conductive and plasmon-supporting noble metals exhibit an especially wide range of size-dependent properties, with discrete electronic levels, strong optical absorption, and efficient radiative relaxation dominating optical behavior at the ~10-atom cluster scale. In this Perspective, we describe the formation and stabilization of silver clusters using DNA templates and highlight the distinct spectroscopic and photophysical properties of the resulting hybrid fluorophores. Strong visible to near-IR emission from DNA-encapsulated silver clusters ranging in size from 5–11 atoms has been produced and characterized. Importantly, this strong Ag cluster fluorescence can be directly modulated and selectively recovered by optically controlling the dark state residence, even when faced with an overwhelming background. The strength and sequence sensitivity of the oligonucleotide-Ag interaction suggests strategies for fine tuning and stabilizing cluster-based emitters in a host of sensing and biolabeling applications that would benefit from brighter, more photostable, and quantifiable emitters in high background environments. PMID:23745165

Separation of silver ions and starch modified silver nanoparticles using high performance liquid chromatography with ultraviolet and inductively coupled mass spectrometric detection

NASA Astrophysics Data System (ADS)

Hanley, Traci A.; Saadawi, Ryan; Zhang, Peng; Caruso, Joseph A.; Landero-Figueroa, Julio

2014-10-01

The production of commercially available products marketed to contain silver nanoparticles is rapidly increasing. Species-specific toxicity is a phenomenon associated with many elements, including silver, making it imperative to develop a method to identify and quantify the various forms of silver (namely, silver ions vs. silver nanoparticles) possibly present in these products. In this study a method was developed using high performance liquid chromatography (HPLC) with ultraviolet (UV-VIS) and inductively coupled mass spectrometric (ICP-MS) detection to separate starch stabilized silver nanoparticles (AgNPs) and silver ions (Ag+) by cation exchange chromatography with 0.5 M nitric acid mobile phase. The silver nanoparticles and ions were baseline resolved with an ICP-MS response linear over four orders of magnitude, 0.04 mg kg- 1 detection limit, and 90% chromatographic recovery for silver solutions containing ions and starch stabilized silver nanoparticles smaller than 100 nm.

Exposure to sublethal concentrations of copper changes biochemistry parameters in silver catfish, Rhamdia quelen, Quoy & Gaimard.

PubMed

Pretto, Alexandra; Loro, Vania Lucia; Silva, Vera M Machado; Salbego, Joseânia; de Menezes, Charlene Cavalheiro; Souza, Carine de Freitas; Gioda, Carolina Rosa; Baldisserotto, Bernardo

2014-04-01

The effects of Cu exposure on catalase (CAT) and acetylcholinesterase (AChE) activity, formation of thiobarbituric acid-reactive species (TBARS) and metabolic parameters were evaluated in silver catfish (Rhamdia quelen). The fish were exposed for 45 days to 0, 16 and 29 μg/L Cu. The fish that were exposed to Cu exhibited lower TBARS levels in the muscle and higher TBARS levels in the liver. They also showed lower CAT activity in the liver and lower AChE activity in the brain and muscle. Higher glucose and lactate and lower protein plasma levels were observed in the fish exposed to Cu. The changes in the hepatic metabolic parameters were Cu concentration dependent. In the muscle, lower glycogen and higher lactate levels were observed in the fish exposed to Cu. Alterations in the metabolic parameters showed a preference for the anaerobic pathway of energy production and liver protein catabolism to supply the energy demand.

Green synthesis of biopolymer-silver nanoparticle nanocomposite: an optical sensor for ammonia detection.

PubMed

Pandey, Sadanand; Goswami, Gopal K; Nanda, Karuna K

2012-11-01

Biopolymer used for the production of nanoparticles (NPs) has attracted increasing attention. In the presence article we use aqueous solution of polysaccharide Cyamopsis tetragonaloba commonly known as guar gum (GG), from plants. GG acts as reductive preparation of silver nanoparticles which are found to be <10 nm in size. The uniformity of the NPs size was measured by the SEM and TEM, while a face centered cubic structure of crystalline silver nanoparticles was characterized using powder X-ray diffraction technique. Aqueous ammonia sensing study of polymer/silver nanoparticles nanocomposite (GG/AgNPs NC) was performed by optical method based on surface plasmon resonance (SPR). The performances of optical sensor were investigated which provide the excellent result. The response time of 2-3 s and the detection limit of ammonia solution, 1 ppm were found at room temperature. Thus, in future this room temperature optical ammonia sensor can be used for clinical and medical diagnosis for detecting low ammonia level in biological fluids, such as plasma, sweat, saliva, cerebrospinal liquid or biological samples in general for various biomedical applications in human. Copyright © 2012 Elsevier B.V. All rights reserved.

Silver nanoparticles with tunable work functions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Pangpang, E-mail: pangpang@molecular-device.kyushu-u.ac.jp; Tanaka, Daisuke; Ryuzaki, Sou

To improve the efficiencies of electronic devices, materials with variable work functions are required to decrease the energy level differences at the interfaces between working layers. Here, we report a method to obtain silver nanoparticles with tunable work functions, which have the same silver core of 5 nm in diameter and are capped by myristates and 1-octanethoilates self-assembled monolayers, respectively. The silver nanoparticles capped by organic molecules can form a uniform two-dimensional sheet at air-water interface, and the sheet can be transferred on various hydrophobic substrates. The surface potential of the two-dimensional nanoparticle sheet was measured in terms of Kelvin probemore » force microscopy, and the work function of the sheet was then calculated from the surface potential value by comparing with a reference material. The exchange of the capping molecules results in a work function change of approximately 150–250 meV without affecting their hydrophobicity. We systematically discussed the origin of the work function difference and found it should come mainly from the anchor groups of the ligand molecules. The organic molecule capped nanoparticles with tunable work functions have a potential for the applications in organic electronic devices.« less

Hybrid Nanoscale Architecture of Wound Dressing with Super Hydrophilic, Antimicrobial, and Ultralow Fouling Attributes.

PubMed

Depan, D; Misra, R D K

2015-02-01

Currently available wound dressings to heal thermal and chronic wounds are unable to respond to the challenges of resistance to bacterial infection, protein adsorption, and increased levels of wound exudates. To this end, we have conceived the fabrication of a new and ideal wound dressing with a number of key attributes. They include effective antimicrobial activity in a controlled manner, ultralow fouling property that provides resistance to protein adsorption and bacterial adhesion, maintain a moist but not saturated environment to promote healing, and is non-adherent and effective in the presence of heavy wound exudate. The novel approach to reduce infection and bacterial colonization involves incorporation of a unique silver-clay nanohybrid architecture in zwitterionic polymer, poly(sulfobetaine). The innovative concept of silver-clay hybrid structure enables us to obtain high, sustained, and diffusion-controlled antimicrobial activity of silver eluting polymer. The sustained and diffusion-controlled high antimicrobial efficiency is obtained through a process involving in situ precipitation of silver nanoparticles with large surface area on the surface of clay platelets. Furthermore, the use of recently developed zwitterionic polymer, poly(sulfobetaine) [poly(SB)] for wound dressing, provides antifouling property, which resists protein adsorption.

Ultra-small Ag clusters in zeolite A4: Antibacterial and thermochromic applications

NASA Astrophysics Data System (ADS)

Horta-Fraijo, P.; Cortez-Valadez, M.; Flores-Lopez, N. S.; Britto Hurtado, R.; Vargas-Ortiz, R. A.; Perez-Rodriguez, A.; Flores-Acosta, M.

2018-03-01

The physical and chemical properties of metal clusters depend on their atomic structure, therefore, it is important to determine the lowest-energy structures of the clusters in order to understand and utilize their properties. In this work, we use the Density Functional Theory (DFT) at the generalized gradient approximation level Becke's three-parameter and the gradient corrected functional of Lee, Yang and Puar (B3LYP) in combination with the basis set LANL2DZ (the effective core potentials and associated double-zeta valence) to determine some of the structural, electronic and vibrational properties of the planar silver clusters (Agn clusters n = 2-24). Additionally, the study reports the experimental synthesis of small silver clusters in synthetic zeolite A4. The synthesis was possible using the ion exchange method with some precursors like silver nitrate (AgNO3) and synthetic zeolite A4. The silver clusters in zeolite powder underwent thermal treatment at 450 °C to release the remaining water or humidity on it. The morphology of the particles was determined by Transmission Electron microscopy. The nanomaterials obtained show thermochromic properties. The structural parameters were correlated theoretically and experimentally.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mokhtari, Narges; Daneshpajouh, Shahram; Seyedbagheri, Seyedali

This study has investigated different visible-light irradiation's effect on the formation of silver nanoparticles from silver nitrate using the culture supernatant of Klebsiella pneumonia. Our study shows that visible-light emission can significantly prompt the synthesis of silver nanoparticles. Also, the study experimentally investigated the liquid mixing process effect on silver nanoparticle synthesis by visible-light irradiation. This study successfully synthesized uniformly dispersed silver nanoparticles with a uniform size and shape in the range of 1-6 nm with an average size of 3 nm. Furthermore, the study investigated the mechanism of the reduction of silver ions by culture supernatant of K. pneumonia,more » and used X-ray diffraction to characterize silver chloride as an intermediate compound. Silver chloride was prepared synthetically and used as a substrate for the synthesis of silver nanoparticles by culture supernatant of K. pneumonia. The silver nanoparticles have been prepared from silver chloride during this investigation for the first time.« less

Feasibility of Silver Doped TiO2/Glass Fiber Photocatalyst under Visible Irradiation as an Indoor Air Germicide

PubMed Central

Pham, Thanh-Dong; Lee, Byeong-Kyu

2014-01-01

This study investigated the feasibility of using Ag-TiO2 photocatalyst supported on glass fiber (Ag-TiO2/GF) prepared by a sol-gel method as an indoor air germicide. An experimental model was designed to investigate the bacterial disinfection efficiency of Staphylococcus (Staph), the most popular bacterium in hospitals in Korea, by the Ag-TiO2/GF photocatalyst. The silver content in Ag/TiO2 was altered from 1 to 10% to investigate the optimal ratio of Ag doped on TiO2/glass fiber (TiO2/GF) for photocatalytic disinfection of Staph. This study confirmed that Ag in Ag-TiO2/GF could work as an electron sink or donor to increase photocatalytic activity and promote the charge separation of electron-hole pairs generated from TiO2 after photon absorption. Ag also acts as an intermediate agent for the transfer of photo-generated electrons from the valence band of TiO2 to an acceptor (O2 gas) to promote photo-oxidation processes. The photocatalytic disinfection activity of Ag-TiO2/GF under visible light increased with the increase in silver content up to 7.5% and then slightly decreased with further increasing silver content. The highest disinfection efficiency and disinfection capacity of Staph using 7.5% Ag-TiO2/GF were 75.23% and 20 (CFU∙s−1∙cm−2) respectively. The medium level of humidity of 60% ± 5% showed better photocatalytic disinfection than the lower (40% ± 5%) or higher (80% ± 5%) levels. PMID:24658408

Silver deposition and tissue staining associated with wound dressings containing silver.

PubMed

Walker, Michael; Cochrane, Christine A; Bowler, Philip G; Parsons, David; Bradshaw, Peter

2006-01-01

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.

Preparation of starch-stabilized silver nanoparticles from amylose-sodium palmitate inclusion complexes

USDA-ARS?s Scientific Manuscript database

Starch-stabilized silver nanoparticles were prepared from amylose-sodium palmitate complexes by first converting sodium palmitate to silver palmitate by reaction with silver nitrate and then reducing the silver ion to metallic silver. This process produced water solutions that could be dried and the...

Cost-effectiveness Analysis of Silver Delivery Approaches in the Management of Partial-thickness Burns.

PubMed

Nherera, Leo; Trueman, Paul; Roberts, Christopher; Berg, Leena

2018-02-23

Burn injury is a common type of traumatic injury that causes considerable morbidity and mortality, resulting in about 30,000 admissions annually in specialist burn centers and costing around $1 billion per year in the United States. One percent silver sulfadiazine has been utilized widely in the management of burns and newer silver dressings are on the market, including nanocrystalline silver dressings, silver-impregnated hydrofiber dressings, and silver-impregnated foam dressings. This study sought to determine the cost effectiveness of the newer silver dressings using clinical data from an indirect treatment comparison using silver sulfadiazine as the baseline. A decision analytic model was developed from a US payer's perspective for burn patients with a total body surface area of < 20%. Outcomes were length of stay, infections and incidence of surgical procedures, quality adjusted life years (QALYs), and cost. The meta-analysis reported a statistically significant reduction in length of hospital stay and clinically important reductions in infections and incidence of surgical procedures in favor of the silver barrier dressing compared with other silver dressings. The estimated QALYs were 0.970 versus 0.969 versus 0.969 and mean cost per patient was $15,892, $23,799, and $24,269 for the nanocrystalline silver dressing, silver-impregnated hydrofiber dressing, and silver-impregnated foam dressing, respectively. The analysis showed the nanocrystalline silver dressing to be a dominant strategy (less costly with better outcomes). These findings were robust to a range of sensitivity analyses. According to data from an indirect treatment comparison, this analysis suggests that nanocrystalline silver dressing is the most cost-effective silver delivery system. Prospective head-to-head research on the costs and outcomes of these silver delivery systems in this patient population is necessary to validate the results of this economic evaluation.

Physicochemical properties of protein-modified silver nanoparticles in seawater

NASA Astrophysics Data System (ADS)

Zhong, Hangyue

2013-10-01

This study investigated the physicochemical properties of silver nanoparticles stabilized with casein protein in seawater. UV?vis spectrometry, dynamic light scattering (DLS), and transmission electron microscopy (TEM) were applied to measure the stability of silver nanoparticles in seawater samples. The obtained results show an increased aggregation tendency of silver nanoparticles in seawater, which could be attributed its relatively high cation concentration that could neutralize the negatively charges adsorbed on the surface of silver nanoparticles and reduce the electrostatic repulsion forces between nanoparticles. Similarly, due to the surface charge screening process, the zeta potential of silver nanoparticles in seawater decreased. This observation further supported the aggregation behavior of silver nanoparticles. This study also investigated the dissolution of silver nanoparticles in seawater. Result shows that the silver nanoparticle dissolution in DI water is lower than in seawater, which is attributed to the high Cl? concentration present in seawater. As Cl? can react with silver and form soluble AgCl complex, dissolution of silver nanoparticles was enhanced. Finally, this study demonstrated that silver nanoparticles are destabilized in seawater condition. These results may be helpful in understanding the environmental risk of discharged silver nanoparticles in seawater conditions.

Silver in medicine: a brief history BC 335 to present.

PubMed

Barillo, David J; Marx, David E

2014-12-01

Silver is a naturally occurring element. Similar to other metals, the ionized form of silver (Ag(+1)) has known antimicrobial properties. A number of wound dressings incorporating silver ion or silver compounds have recently been developed and marketed. In addition, the antimicrobial effects of silver are currently being promoted in consumer products such as clothing and household appliances. The present use of silver in medical and consumer products has prompted concerns for potential toxicity and ecological effects, including induction of microbial resistance to antibiotics. These concerns ignore the fact that silver has been used for medicinal purposes for several thousand years. A historical review of the uses of silver in medicine is presented.

The Electrodeposition of Silver from Supercritical Carbon Dioxide/Acetonitrile

PubMed Central

Bartlett, Philip N; Perdjon-Abel, Magdalena; Cook, David; Reid, Gillian; Levason, William; Cheng, Fei; Zhang, Wenjian; George, Michael W; Ke, Jie; Beanland, Richard; Sloan, Jeremy

2014-01-01

Cyclic voltammetry of silver coordination complexes in acetonitrile and in a single-phase supercritical carbon dioxide/acetonitrile (scCO2/CH3CN) system is reported. Five silver precursors are investigated: (1,5-cyclooctadiene)(hexafluoroacetylacetonato) silver(I) [Ag(hfac)(COD)], (hexafluoroacetylacetonato)(triphenylphosphine) silver(I) [Ag(hfac)(PPh3)], (perfluorooctanoato)bis(triphenylphosphine) silver(I) [Ag(CF3(CF2)6CO2)(PPh3)2], tetrakis(triphenylphosphine) silver(I) tetrafluoroborate [Ag(PPh3)4][BF4] and tetrakis(acetonitrile) silver(I) tetrafluoroborate [Ag(CH3CN)4][BF4]. Of these, [Ag(CH3CN)4][BF4] is found to be the most suitable for electrodeposition of silver from scCO2/CH3CN.

Analysis of silver nanoparticles in antimicrobial products using surface-enhanced Raman spectroscopy (SERS).

PubMed

Guo, Huiyuan; Zhang, Zhiyun; Xing, Baoshan; Mukherjee, Arnab; Musante, Craig; White, Jason C; He, Lili

2015-04-07

Silver nanoparticles (AgNPs) are the most commonly used nanoparticles in consumer products. Concerns over human exposure to and risk from these particles have resulted in increased interest in novel strategies to detect AgNPs. This study investigated the feasibility of surface-enhanced Raman spectroscopy (SERS) as a method for the detection and quantification of AgNPs in antimicrobial products. By using ferbam (ferric dimethyl-dithiocarbamate) as an indicator molecule that binds strongly onto the nanoparticles, AgNPs detection and discrimination were achieved based on the signature SERS response of AgNPs-ferbam complexes. SERS response with ferbam was distinct for silver ions, silver chloride, silver bulk particles, and AgNPs. Two types of AgNPs with different coatings, citrate and polyvinylpirrolidone (PVP), both showed strong interactions with ferbam and induced strong SERS signals. SERS was effectively applicable for detecting Ag particles ranging from 20 to 200 nm, with the highest signal intensity in the 60-100 nm range. A linear relationship (R(2) = 0.9804) between Raman intensity and citrate-AgNPs concentrations (60 nm; 0-20 mg/L) indicates the potential for particle quantification. We also evaluated SERS detection of AgNPs in four commercially available antimicrobial products. Combined with ICP-MS and TEM data, the results indicated that the SERS response is primarily dependent on size, but also affected by AgNPs concentration. The findings demonstrate that SERS is a promising analytical platform for studying environmentally relevant levels of AgNPs in consumer products and related matrices.

Two-stage DNA compaction induced by silver ions suggests a cooperative binding mechanism

NASA Astrophysics Data System (ADS)

Jiang, Wen-Yan; Ran, Shi-Yong

2018-05-01

The interaction between silver ions and DNA plays an important role in the therapeutic use of silver ions and in related technologies such as DNA sensors. However, the underlying mechanism has not been fully understood. In this study, the dynamics of Ag+-DNA interaction at a single-molecule level was studied using magnetic tweezers. AgNO3 solutions with concentrations ranging from 1 μM to 20 μM led to a 1.4-1.8 μm decrease in length of a single λ-DNA molecule, indicating that Ag+ has a strong binding with DNA, causing the DNA conformational change. The compaction process comprises one linear declining stage and another sigmoid-shaped stage, which can be attributed to the interaction mechanism. Considering the cooperative effect, the sigmoid trend was well explained using a phenomenological model. By contrast, addition of silver nanoparticle solution induced no detectable transition of DNA. The dependence of the interaction on ionic strength and DNA concentration was examined via morphology characterization and particle size distribution measurement. The size of the Ag+-DNA complex decreased with an increase in Ag+ ionic strength ranging from 1 μM to 1 mM. Morphology characterization confirmed that silver ions induced DNA to adopt a compacted globular conformation. At a fixed [AgNO3]:[DNA base pairs] ratio, increasing DNA concentration led to increased sizes of the complexes. Intermolecular interaction is believed to affect the Ag+-DNA complex formation to a large extent.

Silver oxide-containing hydroxyapatite coating supports osteoblast function and enhances implant anchorage strength in rat femur.

PubMed

Eto, Shuichi; Miyamoto, Hiroshi; Shobuike, Takeo; Noda, Iwao; Akiyama, Takayuki; Tsukamoto, Masatsugu; Ueno, Masaya; Someya, Shinsuke; Kawano, Shunsuke; Sonohata, Motoki; Mawatari, Masaaki

2015-09-01

Antibacterial silver with hydroxyapatite (Ag-HA) is a promising coating material for imparting antibacterial properties to implants. We previously reported that 3% (w/w) silver with HA (3% Ag-HA) has both antibacterial activity and osteoconductivity. In this study, we investigated the effects of Ag-HA on the in vitro osteoblast function and the in vivo anchorage strength and osteoconductivity of implants. Production of the osteoblast marker alkaline phosphatase, but not cytotoxicity, was observed in cells of the osteoblast cell line MC3T3-E1 cultured on the 3% Ag-HA-coated surface. These results were similar to those observed with silver-free HA coating. In contrast, a significant high level of cytotoxicity was observed when the cells were cultured on a 50% Ag-HA-coated surface. The anchorage strength of implants inserted into the femur of Sprague-Dawley (SD) rats was enhanced by coating the implants with 3% Ag-HA. On the 3% Ag-HA-coated surface, both metaphyseal and diaphyseal areas were largely covered with new bone and had adequate osteoconductivity. These results suggest that 3% Ag-HA, like conventional HA, promotes osteogenesis by supporting osteoblast viability and function and thereby contributes to sufficient anchorage strength of implants. Application of 3% Ag-HA, which combines the osteoconductivity of HA and the antibacterial activity of silver, to prosthetic joints will help prevent postoperative infections. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Enhanced broadband near-infrared luminescence from Pr3+-doped tellurite glass with silver nanoparticles

NASA Astrophysics Data System (ADS)

Cheng, Pan; Zhou, Yaxun; Zhou, Minghan; Su, Xiue; Zhou, Zizhong; Yang, Gaobo

2017-11-01

Pr3+-doped tellurite glasses containing metallic silver NPs were synthesized by the conventional melt-quenching technique. Structural, thermal and optical properties of the synthesized glass samples were characterized by X-Ray diffraction (XRD) curves, Raman spectra, differential scanning calorimeter (DSC) curves, transmission electron microscopy (TEM) images, UV/Vis/NIR absorption and near-infrared fluorescence emission spectra. The XRD curves confirmed the amorphous structural nature of the synthesized glasses, the Raman spectra identified the presence of different vibrational groups, the DSC curves verified the good thermal stability, and the TEM images revealed the nucleated silver NPs with average diameter about 10 nm dispersed in the glass matrix and its surface Plasmon resonance (SPR) absorption band was located at around 510 nm. Besides, Judd-Ofelt intensity parameters Ωt (t = 2, 4, 6) and other important spectroscopic parameters like transition probability, radiative lifetime, branching ratio were calculated to evaluate the radiative properties of Pr3+ levels from the measured optical absorption spectra. It was found that Pr3+-doped tellurite glasses could emit an ultra-broadband fluorescence extending from 1250 to 1650 nm under the 488 nm excitation, and this fluorescence emission increased further with the introduction of silver NPs. The enhanced fluorescence was mainly attributed to the increased local electric field around Pr3+ induced by silver NPs. The present results demonstrate that Pr3+-Ag codoped tellurite glass is a promising candidate for the near-infrared band ultra-broadband fiber amplifiers covering the expanded low-loss communication window.

Room temperature synthesis of silver nanowires from tabular silver bromide crystals in the presence of gelatin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Suwen; Wehmschulte, Rudolf J.; Lian Guoda

2006-03-15

Long silver nanowires were synthesized at room temperature by a simple and fast process derived from the development of photographic films. A film consisting of an emulsion of tabular silver bromide grains in gelatin was treated with a photographic developer (4-(methylamino)phenol sulfate (metol), citric acid) in the presence of additional aqueous silver nitrate. The silver nanowires have lengths of more than 50 {mu}m, some even more than 100 {mu}m, and average diameters of about 80 nm. Approximately, 70% of the metallic silver formed in the reduction consists of silver nanowires. Selected area electron diffraction (SAED) results indicate that the silvermore » nanowires grow along the [111] direction. It was found that the presence of gelatin, tabular silver bromide crystals and silver ions in solution are essential for the formation of the silver nanowires. The nanowires appear to originate from the edges of the silver bromide crystals. They were characterized by transmission electron microscopy (TEM), SAED, scanning electron microscopy (SEM), and powder X-ray diffraction (XRD)« less

A review of the antibacterial effects of silver nanomaterials and potential implications for human health and the environment

NASA Astrophysics Data System (ADS)

Marambio-Jones, Catalina; Hoek, Eric M. V.

2010-06-01

Here, we present a review of the antibacterial effects of silver nanomaterials, including proposed antibacterial mechanisms and possible toxicity to higher organisms. For purpose of this review, silver nanomaterials include silver nanoparticles, stabilized silver salts, silver-dendrimer, polymer and metal oxide composites, and silver-impregnated zeolite and activated carbon materials. While there is some evidence that silver nanoparticles can directly damage bacteria cell membranes, silver nanomaterials appear to exert bacteriocidal activity predominantly through release of silver ions followed (individually or in combination) by increased membrane permeability, loss of the proton motive force, inducing de-energization of the cells and efflux of phosphate, leakage of cellular content, and disruption DNA replication. Eukaryotic cells could be similarly impacted by most of these mechanisms and, indeed, a small but growing body of literature supports this concern. Most antimicrobial studies are performed in simple aquatic media or cell culture media without proper characterization of silver nanomaterial stability (aggregation, dissolution, and re-precipitation). Silver nanoparticle stability is governed by particle size, shape, and capping agents as well as solution pH, ionic strength, specific ions and ligands, and organic macromolecules—all of which influence silver nanoparticle stability and bioavailability. Although none of the studies reviewed definitively proved any immediate impacts to human health or the environment by a silver nanomaterial containing product, the entirety of the science reviewed suggests some caution and further research are warranted given the already widespread and rapidly growing use of silver nanomaterials.

Quantification of metal loading to Silver Creek through the Silver Maple Claims area, Park City, Utah, May 2002

USGS Publications Warehouse

Kimball, Briant A.; Johnson, Kevin K.; Runkel, Robert L.; Steiger, Judy I.

2004-01-01

The Silver Maple Claims area along Silver Creek, near Park City, Utah, is administered by the Bureau of Land Management. To quantify possible sources of elevated zinc concentrations in Silver Creek that exceed water-quality standards, the U.S. Geological Survey conducted a mass-loading study in May 2002 along a 1,400-meter reach of Silver Creek that included the Silver Maple Claims area. Additional samples were collected upstream and downstream from the injection reach to investigate other possible sources of zinc and other metals to the stream. Many metals were investigated in the study, but zinc is of particular concern for water-quality standards. The total loading of zinc along the study reach from Park City to Wanship, Utah, was about 49 kilograms per day. The Silver Maple Claims area contributed about 38 percent of this load. The Silver Creek tailings discharge pipe, which empties just inside the Silver Maple Claims area, contributed more than half the load of the Silver Maple Claims area. Substantial zinc loads also were added to Silver Creek downstream from the Silver Maple Claims area. Ground-water discharge upstream from the waste-water treatment plant contributed 20 percent of the total zinc load, and another 17 percent was contributed near the waste-water treatment plant. By identifying the specific areas where zinc and other metal loads are contributed to Silver Creek, it is possible to assess the needs of a remediation plan. For example, removing the tailings from the Silver Maple Claims area could contribute to lowering the zinc concentration in Silver Creek, but without also addressing the loading from the Silver Creek tailings discharge pipe and the ground-water discharge farther downstream, the zinc concentration could not be lowered enough to meet water-quality standards. Additional existing sources of zinc loading downstream from the Silver Maple Claims area could complicate the process of lowering zinc concentration to meet water-quality standards.

Plasmonic characterization of photo-induced silver nanoparticles extracted from silver halide based TEM film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sudheer,, E-mail: sudheer@rrcat.gov.in; Tiwari, P.; Rai, V. N.

The plasmonic responses of silver nanoparticles extracted from silver halide based electron microscope film are investigated. Photo-reduction process is carried out to convert the silver halide grains into the metallic silver. The centrifuge technique is used for separating the silver nanoparticles from the residual solution. Morphological study performed by field emission scanning electron microscope (FESEM) shows that all the nanoparticles have an average diameter of ~120 nm with a high degree of mono dispersion in size. The localized surface plasmon resonance (LSPR) absorption peak at ~537 nm confirms the presence of large size silver nanoparticles.

Silver ion-mediated killing of a food pathogen: Melting curve analysis data of silver resistance genes and growth curve data.

PubMed

Gokulan, Kuppan; Williams, Katherine; Khare, Sangeeta

2017-04-01

Limited antibacterial activity of silver ions leached from silver-impregnated food contact materials could be due to: 1) the presence of silver resistance genes in tested bacteria ; or 2) lack of susceptibility to silver ion-mediated killing in the bacterial strain (K. Williams, L. Valencia, K. Gokulan, R. Trbojevich, S. Khare, 2016 [1]). This study contains data to address the specificity of silver resistance genes in Salmonella Typhimurium during the real time PCR using melting curve analysis and an assessment of the minimum inhibitory concentration of silver ions for Salmonella .

Plasmonic particles of colloidal silver in high-resolution recording media

NASA Astrophysics Data System (ADS)

Andreeva, O. V.; Andreeva, N. V.; Kuzmina, T. B.

2017-01-01

The optical properties of colloidal silver particles formed photographically in high-resolution silver halide photographic materials have been considered. The conditions that allow one to obtain exposed and developed light-sensitive silver halide particles in the form of colloidal particles of metallic silver having the properties of localized plasmons have been described. The results of the studies of the developed silver particles in traditional photographic materials for image holography and in nanoporous silver halide photographic materials for volume holography have been presented. The perspectives of using plasmonic silver nanoparticles produced photographically have been discussed.

Rapid deposition of triangular silver nanoplates on planar surfaces: application to metal-enhanced fluorescence.

PubMed

Aslan, Kadir; Lakowicz, Joseph R; Geddes, Chris D

2005-04-07

A simple and rapid wet-chemical technique for the deposition of silver triangles on conventional glass substrates, which alleviates the need for lithography, has been developed. The technique is based on the seed-mediated cetyltrimethylammonium-bromide-directed growth of silver triangles on glass surfaces, where smaller spherical silver seeds that were attached to the surface were subsequently converted and grown into silver triangles in the presence of a cationic surfactant and silver ions. The size of the silver triangles was controlled by sequential immersion of silver seed-coated glass substrates into a growth solution and by the duration time of immersion. Atomic force microscopy studies revealed that the size of the silver triangles ranged between 100 and 500 nm. Interestingly, these new surfaces are a significant improvement over traditional silver island films for applications in metal-enhanced fluorescence. A routine 16-fold enhancement in emission intensity was typically observed, for protein-immobilized indocyanine green, with a relatively very low loading density of silver triangles on the glass surface.

High purity silver microcrystals recovered from silver wastes by eco-friendly process using hydrogen peroxide.

PubMed

Gatemala, Harnchana; Ekgasit, Sanong; Wongravee, Kanet

2017-07-01

A simple, rapid, and environmentally friendly process using hydrogen peroxide, was developed for recovering high purity silver directly from industry and laboratory wastes. Silver ammine complex, [Ag(NH 3 ) 2 ] + Cl - , derived from AgCl were generated and then directly reduced using H 2 O 2 to reliably turn into high purity microcrystalline silver (99.99%) examined by EDS and XRD. Morphology of the recovered silver microcrystals could be selectively tuned by an addition of poly(vinyl pyrrolidone). The main parameters in the recovering process including pH, concentration of Ag + and the mole ratio of H 2 O 2 :Ag + were carefully optimized though the central composite design (CCD). The optimized condition was employed for a trial recovery of 50 L silver ammine complex prepared from a collection of silver-wastes during 3-year research on industrial nanoparticle production. The recovered silver microcrystals >700 g could be recovered with 91.27%. The remaining solution after filtering of the recovered silver microcrystals can be used repeatedly (at least 8 cycles) without losing recovery efficiency. Matrix interferences including Pb 2+ and Cl - play a minimal role in our silver recovery process. Furthermore, the direct usage of the recovered silver microcrystals was demonstrated by using as a raw material of silver clay for creating a set of wearable silver jewelries. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparison of three different dressings for partial thickness burns in children: study protocol for a randomised controlled trial

PubMed Central

2013-01-01

Background In the paediatric population, pain and distress associated with burn injuries during wound care procedures remain a constant challenge. Although silver dressings are the gold standard for burn care in Australasia, very few high-level trials have been conducted that compare silver dressings to determine which will provide the best level of care clinically. Therefore, for paediatric patients in particular, identifying silver dressings that are associated with lower levels of pain and rapid wound re-epithelialisation is imperative. This study will determine whether there is a difference in time to re-epithelialisation and pain and distress experienced during wound care procedures among Acticoat™, Acticoat™ combined with Mepitel™ and Mepilex Ag™ dressings for acute, paediatric partial thickness burns. Methods/Design Children aged 0 to 15 years with an acute partial thickness (superficial partial to deep partial thickness inclusive) burn injury and a burn total body surface area of ≤10% will be eligible for the trial. Patients will be randomised to one of the three dressing groups: (1) Acticoat™ or (2) Acticoat™ combined with Mepitel™ or (3) Mepilex Ag™. A minimum of 28 participants will be recruited for each treatment group. Primary measures of pain, distress and healing will be repeated at each dressing change until complete wound re-epithelialisation occurs or skin grafting is required. Additional data collected will include infection status at each dressing change, physical function, scar outcome and scar management requirements, cost effectiveness of each dressing and staff perspectives of the dressings. Discussion The results of this study will determine the effects of three commonly used silver and silicone burn dressing combinations on the rate of wound re-epithelialisation and pain experienced during dressing procedures in acute, paediatric partial thickness burn injuries. Trial registration Australian New Zealand Clinical Trials Registry ACTRN12613000105741 PMID:24274190

Low concentrations of silver nanoparticles have a beneficial effect on wound healing in vitro

NASA Astrophysics Data System (ADS)

Ambrožová, Nikola; Zálešák, Bohumil; Ulrichová, Jitka; Čížková, Kateřina; Galandáková, Adéla

2017-03-01

Silver has been used in medical application for its antibacterial, antifungal, and anti-inflammatory effects. Silver nanoparticles (AgNPs) are currently in the spotlight. It was shown that their application can be useful in the management of wounds. Our study was conducted to determine whether AgNPs (average size 10.43 ± 4.74 nm) and ionic silver (Ag-I) could affect the wound healing in the in vitro model of normal human dermal fibroblasts (NHDF). We evaluated their effect on reactive oxygen species (ROS) generation and the expression of key transcription factors that coordinate the cellular response to oxidative stress [nuclear factor (erythroid-derived 2)-like 2 (Nrf2)] and inflammation [nuclear factor-κB (NF-κB)], expression of heme oxygenase-1 (HO-1), and interleukin-6 (IL-6) level. Isolated primary NHDF were scratched, heated (1 h; 42 °C), and cultured with AgNPs (0.25, 2.5, and 25 μg/ml) and Ag-I (0.025, 0.1, and 0.25 μg/ml) for 8 or 24 h. The ROS generation, Nrf2, NF-κB, and HO-1 protein expression and IL-6 protein level were then evaluated by standard methods. Non-cytotoxic concentrations of AgNPs (0.25 and 2.5 μg/ml) did not affect the ROS generation but activated the Nrf2/HO-1 pathway and decreased the NF-κB expression and IL-6 level in the in vitro wound healing model. AgNPs at concentrations of 0.25 and 2.5 μg/ml seem to be suitable for the intended application as a topical agent for wound healing, although the gene silencing technique, chemical inhibitors, and detailed time- and concentration-dependent experiments are needed for a comprehensive study of signaling pathway regulation. Further investigation is also necessary to exclude any possible adverse effects.

21 CFR 310.548 - Drug products containing colloidal silver ingredients or silver salts offered over-the-counter...

Code of Federal Regulations, 2011 CFR

2011-04-01

... ingredients or silver salts offered over-the-counter (OTC) for the treatment and/or prevention of disease. 310...) for the treatment and/or prevention of disease. (a) Colloidal silver ingredients and silver salts have... disease conditions. There are serious and complicating aspects to many of the diseases these silver...

21 CFR 310.548 - Drug products containing colloidal silver ingredients or silver salts offered over-the-counter...

Code of Federal Regulations, 2010 CFR

2010-04-01

... ingredients or silver salts offered over-the-counter (OTC) for the treatment and/or prevention of disease. 310...) for the treatment and/or prevention of disease. (a) Colloidal silver ingredients and silver salts have... disease conditions. There are serious and complicating aspects to many of the diseases these silver...

21 CFR 310.548 - Drug products containing colloidal silver ingredients or silver salts offered over-the-counter...

Code of Federal Regulations, 2013 CFR

2013-04-01

... ingredients or silver salts offered over-the-counter (OTC) for the treatment and/or prevention of disease. 310...) for the treatment and/or prevention of disease. (a) Colloidal silver ingredients and silver salts have... disease conditions. There are serious and complicating aspects to many of the diseases these silver...

21 CFR 310.548 - Drug products containing colloidal silver ingredients or silver salts offered over-the-counter...

Code of Federal Regulations, 2012 CFR

2012-04-01

... ingredients or silver salts offered over-the-counter (OTC) for the treatment and/or prevention of disease. 310...) for the treatment and/or prevention of disease. (a) Colloidal silver ingredients and silver salts have... disease conditions. There are serious and complicating aspects to many of the diseases these silver...

21 CFR 310.548 - Drug products containing colloidal silver ingredients or silver salts offered over-the-counter...

Code of Federal Regulations, 2014 CFR

2014-04-01

... ingredients or silver salts offered over-the-counter (OTC) for the treatment and/or prevention of disease. 310...) for the treatment and/or prevention of disease. (a) Colloidal silver ingredients and silver salts have... disease conditions. There are serious and complicating aspects to many of the diseases these silver...

77 FR 61661 - Price for the American Eagle Silver Proof and Uncirculated Coins and the America the Beautiful...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-10

... DEPARTMENT OF THE TREASURY United States Mint Price for the American Eagle Silver Proof and... price of silver, the United States Mint is raising the price of its American Eagle Silver Proof and... price 2012 American Eagle Silver Proof $59.95 2012 American Eagle Silver Uncirculated 50.95 2011...

Water Purification

NASA Technical Reports Server (NTRS)

1994-01-01

The Vision Catalyst Purifier employs the basic technology developed by NASA to purify water aboard the Apollo spacecraft. However, it also uses an "erosion" technique. The purifier kills bacteria, viruses, and algae by "catalytic corrosion." A cartridge contains a silver-impregnated alumina bed with a large surface area. The catalyst bed converts oxygen in a pool of water to its most oxidative state, killing over 99 percent of the bacteria within five seconds. The cartridge also releases into the pool low levels of ionic silver and copper through a controlled process of erosion. Because the water becomes electrochemically active, no electricity is required.

Hybrid microwave/conventionally heated calorimeter

NASA Astrophysics Data System (ADS)

Binner, Jon G. P.; Price, Duncan M.; Reading, Mike; Vaidhyanathan, Bala

2005-06-01

The design and construction of a calorimeter in which the specimen may be heated by microwave radiation and/or hot air is described. The apparatus was used to examine the effect of microwave radiation on the melting of benzil (89°C) and the solid-state phase transition of silver iodide (147°C). Reproducibility of transition temperature determinations were within ±1°C. No changes were observed for benzil but silver iodide exhibited an apparent reduction in transition temperature to around 120°C in the presence of microwaves, which increased with the level of microwave irradiation.

Comment on "A re-assessment of the safety of silver in household water treatment: rapid systematic review of mammalian in vivo genotoxicity studies".

PubMed

Lantagne, Daniele; Rayner, Justine; Mittelman, Anjuliee; Pennell, Kurt

2017-11-13

We wish to thank Fewtrell, Majuru, and Hunter for their article highlighting genotoxic risks associated with the use of particulate silver for primary drinking water treatment. The recent promotion of colloidal silver products for household water treatment in developing countries is problematic due to previously identified concerns regarding manufacturing quality and questionable advertising practices, as well as the low efficiency of silver nanoparticles to treat bacteria, viruses, and protozoa in source waters. However, in the conclusion statement of the manuscript, Fewtrell et al. state, "Before colloidal Ag or AgNP are used in filter matrices for drinking water treatment, consideration needs to be given to how much silver is likely to be released from the matrix during the life of the filter." Unfortunately, it appears Fewtrell et al. were unaware that studies of silver nanoparticle and silver ion elution from ceramic filters manufactured and used in developing countries have already been completed. These existing studies have found that: 1) silver ions, not silver nanoparticles, are eluted from ceramic filters treated with silver nanoparticles or silver nitrate; and, 2) silver ions have not been shown to be genotoxic. Thus, the existing recommendation of applying silver nanoparticles to ceramic filters to prevent biofilm formation within the filter and improve microbiological efficacy should still be adhered to, as there is no identified risk to people who drink water from ceramic filters treated with silver nanoparticles or silver nitrate. We note that efforts should continue to minimize exposure to silver nanoparticles (and silica) to employees in ceramic filter factories in collaboration with the organizations that provide technical assistance to ceramic filter factories.

New Paradigm Shift for the Green Synthesis of Antibacterial Silver Nanoparticles Utilizing Plant Extracts

PubMed Central

2014-01-01

This review covers general information regarding the green synthesis of antibacterial silver nanoparticles. Owing to their antibacterial properties, silver nanoparticles are widely used in many areas, especially biomedical applications. In green synthesis practices, the chemical reducing agents are eliminated, and biological entities are utilized to convert silver ions to silver nanoparticles. Among the various biological entities, natural plant extracts have emerged as green reducing agents, providing eco-friendly routes for the preparation of silver nanomaterials. The most obvious merits of green synthesis are the increased biocompatibility of the resulting silver nanoparticles and the ease with which the reaction can be carried out. This review summarizes some of the plant extracts that are used to produce antibacterial silver nanoparticles. Additionally, background information regarding the green synthesis and antibacterial activity of silver nanoparticles is provided. Finally, the toxicological aspects of silver nanoparticles are briefly mentioned. PMID:25343010

Silver Recycling in the United States in 2000

USGS Publications Warehouse

Hilliard, Henry E.

2003-01-01

In 2000, the global silver supply deficit (the difference between mine and scrap supply and silver demand) was more than 3,000 metric tons. U.S. silver demand for photographic applications alone was nearly equal to annual U.S. silver production. Until 1968, the U.S. silver deficit was filled by withdrawals from the U.S. Treasury reserves. In 2000, the deficit was filled by destocking, imports, and recycling. Photographic wastes, spent catalysts, and electronic scrap are the major sources of materials for silver recycling. Nearly 1,800 tons of silver contained in these materials were available for recycling in 2000. Other recyclable silver-bearing materials include dental alloys, jewelry, and silverware. In 2000, an estimated 1,700 tons of silver were recovered from secondary sources in the United States. The U.S. recycling efficiency for old scrap was calculated to have been 97 percent in 2000; the recycling rate was estimated to be 32 percent.

Silver recycling in the United States in 2000

USGS Publications Warehouse

Hilliard, Henry E.

2003-01-01

In 2000, the global silver supply deficit (the difference between mine and scrap supply and silver demand) was more than 3,000 metric tons. U.S. silver demand for photographic applications alone was nearly equal to annual U.S. silver production. Until 1968, the U.S. silver deficit was filled by withdrawals from the U.S. Treasury reserves. In 2000, the deficit was filled by destocking, imports, and recycling. Photographic wastes, spent catalysts, and electronic scrap are the major sources of materials for silver recycling. Nearly 1,800 metric tons of silver contained in these materials were available for recycling in 2000. Other recyclable silver-bearing materials include dental alloys, jewelry, and silverware. In 2000, an estimated 1,700 tons of silver were recovered from secondary sources in the United States. The U.S. recycling efficiency for old scrap was calculated to have been 97 percent in 2000; the recycling rate was estimated to be 32 percent.

Silver distribution and release from an antimicrobial denture base resin containing silver colloidal nanoparticles.

PubMed

Monteiro, Douglas Roberto; Gorup, Luiz Fernando; Takamiya, Aline Satie; de Camargo, Emerson Rodrigues; Filho, Adhemar Colla Ruvolo; Barbosa, Debora Barros

2012-01-01

The aim of this study was to evaluate a denture base resin containing silver colloidal nanoparticles through morphological analysis to check the distribution and dispersion of these particles in the polymer and by testing the silver release in deionized water at different time periods. A Lucitone 550 denture resin was used, and silver nanoparticles were synthesized by reduction of silver nitrate with sodium citrate. The acrylic resin was prepared in accordance with the manufacturers' instructions, and silver nanoparticle suspension was added to the acrylic resin monomer in different concentrations (0.05, 0.5, and 5 vol% silver colloidal). Controls devoid of silver nanoparticles were included. The specimens were stored in deionized water at 37°C for 7, 15, 30, 60, and 120 days, and each solution was analyzed using atomic absorption spectroscopy. Silver was not detected in deionized water regardless of the silver nanoparticles added to the resin and of the storage period. Micrographs showed that with lower concentrations, the distribution of silver nanoparticles was reduced, whereas their dispersion was improved in the polymer. Moreover, after 120 days of storage, nanoparticles were mainly located on the surface of the nanocomposite specimens. Incorporation of silver nanoparticles in the acrylic resin was evidenced. Moreover, silver was not detected by the detection limit of the atomic absorption spectrophotometer used in this study, even after 120 days of storage in deionized water. Silver nanoparticles are incorporated in the PMMA denture resin to attain an effective antimicrobial material to help control common infections involving oral mucosal tissues in complete denture wearers. © 2011 by the American College of Prosthodontists.

Similarities and Differences between Silver Ions and Silver in Nanoforms as Antibacterial Agents

PubMed Central

Kędziora, Anna; Speruda, Mateusz; Rybka, Jacek; Łukowiak, Anna; Bugla-Płoskońska, Gabriela

2018-01-01

Silver is considered as antibacterial agent with well-known mode of action and bacterial resistance against it is well described. The development of nanotechnology provided different methods for the modification of the chemical and physical structure of silver, which may increase its antibacterial potential. The physico-chemical properties of silver nanoparticles and their interaction with living cells differs substantially from those of silver ions. Moreover, the variety of the forms and characteristics of various silver nanoparticles are also responsible for differences in their antibacterial mode of action and probably bacterial mechanism of resistance. The paper discusses in details the aforementioned aspects of silver activity. PMID:29393866

The dual role of silver during silicon etching in HF solution.

PubMed

Abouda-Lachiheb, Manel; Nafie, Nesma; Bouaicha, Mongi

2012-08-13

It was reported that during silicon etching, silver was subjected to have a controversial role. Some researchers debate that silver protects silicon, and, at the same time, other ones confirm that silver catalyzes silicon underneath. In this paper, we give experimental results arguing the dual role that silver has during the formation of silicon nanostructures. We give a proof that the role of silver depends on the experimental details and the intrinsic properties of silver during its deposition on the silicon wafer. Through our investigations, we tracked the silver particles that indicated which mechanism is involved. Characterizations of the prepared samples were made using a scanning electron microscope.

Colored and semitransparent silver nanoparticle layers deposited by spin coating of silver nanoink

NASA Astrophysics Data System (ADS)

Yoon, Hoi Jin; Jo, Yejin; Jeong, Sunho; Lim, Jung Wook; Lee, Seung-Yun

2018-05-01

In this letter, we report on the fabrication and characterization of colored and semitransparent silver nanoparticle layers. A spin coating of silver nanoink is used to deposit silver nanoparticle layers onto substrates. The transmittance and color of the silver nanoparticle layers are significantly dependent on the spin speed and nanoink concentration, owing to variations in the size and distribution of the nanoparticles. Both color variation and efficiency improvement are achieved with the application of silver nanoparticles to semitransparent Si thin-film solar cells, which is associated with the excitation of the dipole or quadruple plasmon modes of the silver nanoparticles.

Silver nanoparticles: A new view on mechanistic aspects on antimicrobial activity.

PubMed

Durán, Nelson; Durán, Marcela; de Jesus, Marcelo Bispo; Seabra, Amedea B; Fávaro, Wagner J; Nakazato, Gerson

2016-04-01

Silver nanoparticles are well known potent antimicrobial agents. Although significant progresses have been achieved on the elucidation of antimicrobial mechanism of silver nanoparticles, the exact mechanism of action is still not completely known. This overview incorporates a retrospective of previous reviews published and recent original contributions on the progress of research on antimicrobial mechanisms of silver nanoparticles. The main topics discussed include release of silver nanoparticles and silver ions, cell membrane damage, DNA interaction, free radical generation, bacterial resistance and the relationship of resistance to silver ions versus resistance to silver nanoparticles. The focus of the overview is to summarize the current knowledge in the field of antibacterial activity of silver nanoparticles. The possibility that pathogenic microbes may develop resistance to silver nanoparticles is also discussed. Antibacterial effect of nanoscopic silver generated a lot of interest both in research projects and in practical applications. However, the exact mechanism is still will have to be elucidated. This overview incorporates a retrospective of previous reviews published from 2007 to 2013 and recent original contributions on the progress of research on antimicrobial mechanisms to summarize our current knowledge in the field of antibacterial activity of silver nanoparticles. Copyright © 2015 Elsevier Inc. All rights reserved.

In situ green synthesis and characterization of sericin-silver nanoparticle composite with effective antibacterial activity and good biocompatibility.

PubMed

He, Huawei; Tao, Gang; Wang, Yejing; Cai, Rui; Guo, Pengchao; Chen, Liqun; Zuo, Hua; Zhao, Ping; Xia, Qingyou

2017-11-01

Silver nanoparticle has been widely applied to a variety of fields for its outstanding antimicrobial activity. However, the stability of silver nanoparticle limits its application under certain conditions. Thus, improving the stability of silver nanoparticle via biosynthesis is a promising shortcut to expand its application. Sericin from silkworm cocoon has good hydrophilicity, reaction activity, biocompatibility and biodegradability. In this study, we developed a novel, simple, one-step biosynthesis method to prepare sericin-silver nanoparticle composite in situ in solution. Sericin served as the reductant of silver ion, the dispersant and stabilizer of the prepared sericin-silver nanoparticle composite. Natural light was the only power source used to catalyze the synthesis of silver nanoparticle in situ in solution. The novel sericin-silver nanoparticle composite was characterized by ultraviolet-visible and fluorescence spectroscopy, X-ray diffraction, transmission electron microscopy and fourier transform infrared spectroscopy. The results showed silver nanoparticle could be synthesized through the reduction of AgNO 3 by the phenolic hydroxyl group of tyrosine residues of sericin under the catalysis of natural light. The synthesized silver nanoparticle had good crystalline, size distribution and long-term stability at room temperature. Light irradiation was essential for the preparation of sericin-silver nanoparticle composite. The antibacterial activity assay showed 25mg/L and 100mg/L were the minimum concentrations of sericin-silver nanoparticle composite required to inhibit the growth of Staphylococcus aureus and kill this bacterium, respectively. The cytotoxicity assay showed cell viability and cell growth were almost not affected by sericin-silver nanoparticle composite under the concentration of 25mg/L. Our study suggested the preparation of sericin-silver nanoparticle composite was environmentally friendly and energy conservation, and the prepared sericin-silver nanoparticle composite had long-term stability, effective antibacterial activity and good biocompatibility. This novel sericin-silver nanoparticle composite has shown great potentials for biomedical application such as antibacterial agent and wound care. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterization of engineered nanoparticles in commercially available spray disinfectant products advertised to contain colloidal silver.

PubMed

Rogers, Kim R; Navratilova, Jana; Stefaniak, Aleksandr; Bowers, Lauren; Knepp, Alycia K; Al-Abed, Souhail R; Potter, Phillip; Gitipour, Alireza; Radwan, Islam; Nelson, Clay; Bradham, Karen D

2018-04-01

Given the potential for human exposure to silver nanoparticles from spray disinfectants and dietary supplements, we characterized the silver-containing nanoparticles in 22 commercial products that advertised the use of silver or colloidal silver as the active ingredient. Characterization parameters included: total silver, fractionated silver (particulate and dissolved), primary particle size distribution, hydrodynamic diameter, particle number, and plasmon resonance absorbance. A high degree of variability between claimed and measured values for total silver was observed. Only 7 of the products showed total silver concentrations within 20% of their nominally reported values. In addition, significant variations in the relative percentages of particulate vs. soluble silver were also measured in many of these products reporting to be colloidal. Primary silver particle size distributions by transmission electron microscopy (TEM) showed two populations of particles - smaller particles (<5nm) and larger particles between 20 and 40nm. Hydrodynamic diameter measurements using nanoparticle tracking analysis (NTA) correlated well with TEM analysis for the larger particles. Z-average (Z-Avg) values measured using dynamic light scattering (DLS); however, were typically larger than both NTA or TEM particle diameters. Plasmon resonance absorbance signatures (peak absorbance at around 400nm indicative of metallic silver nanoparticles) were only noted in 4 of the 9 yellow-brown colored suspensions. Although the total silver concentrations were variable among products, ranging from 0.54mg/L to 960mg/L, silver containing nanoparticles were identified in all of the product suspensions by TEM. Published by Elsevier B.V.

Silver Flakes and Silver Dendrites for Hybrid Electrically Conductive Adhesives with Enhanced Conductivity

NASA Astrophysics Data System (ADS)

Ma, Hongru; Li, Zhuo; Tian, Xun; Yan, Shaocun; Li, Zhe; Guo, Xuhong; Ma, Yanqing; Ma, Lei

2018-03-01

Silver dendrites were prepared by a facile replacement reaction between silver nitrate and zinc microparticles of 20 μm in size. The influence of reactant molar ratio, reaction solution volume, silver nitrate concentration, and reaction time on the morphology of dendrites was investigated systematically. It was found that uniform tree-like silver structures are synthesized under the optimal conditions. Their structure can be described as a trunk, symmetrical branches, and leaves, which length scales of 5-10, 1-2 μm, and 100-300 nm, respectively. All features were systematically characterized by scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and x-ray powder diffraction. A hybrid fillers system using silver flakes and dendrites as electrically conductive adhesives (ECAs) exhibited excellent overall performance. This good conductivity can be attributed mainly to the synergy between the silver microflakes (5-20 μm sized irregular sheet structures) and dendrites, allowing more conductive pathways to be formed between the fillers. In order to further optimize the overall electrical conductivity, various mixtures of silver microflakes and silver dendrites were tested in ECAs, with results indicating that the highest conductivity was shown when the amounts of silver microflakes, silver dendrites and the polymer matrix were 69.4 wt.% (20.82 vol.%), 0.6 wt.% (0.18 vol.%), and 30.0 wt.% (79.00 vol.%), respectively. The corresponding mass ratio of silver flakes to silver dendrites was 347:3. The resistivity of ECAs reached as low as 1.7 × 10-4 Ω cm.

Multilevel modeling of retention and disinfection efficacy of silver nanoparticles on ceramic water filters.

PubMed

Mikelonis, Anne M; Lawler, Desmond F; Passalacqua, Paola

2016-10-01

This research examined how variations in synthesis methods of silver nanoparticles affect both the release of silver from ceramic water filters (CWFs) and disinfection efficacy. The silver nanoparticles used were stabilized by four different molecules: citrate, polyvinylpyrrolidone, branched polyethylenimine, and casein. A multilevel statistical model was built to quantify if there was a significant difference in: a) extent of silver lost, b) initial amount of silver lost, c) silver lost for water of different quality, and d) total coliform removal. Experiments were performed on location at Pure Home Water, a CWF factory in Tamale, Ghana using stored rainwater and dugout water (a local surface water). The results indicated that using dugout vs. rainwater significantly affects the initial (p-value 0.0015) and sustained (p-value 0.0124) loss of silver, but that silver type does not have a significant effect. On average, dugout water removed 37.5μg/L more initial silver and had 1.1μg/L more silver in the filtrate than rainwater. Initially, filters achieved 1.9 log reduction values (LRVs) on average, but among different silver and water types this varied by as much as 2.5 LRV units. Overall, bacterial removal effectiveness was more challenging to evaluate, but some data suggest that the branched polyethylenimine silver nanoparticles provided improved initial bacterial removal over filters which were not painted with silver nanoparticles (p-value 0.038). Copyright © 2016 Elsevier B.V. All rights reserved.

Silver removal from aqueous solution by biochar produced from biosolids via microwave pyrolysis.

PubMed

Antunes, Elsa; Jacob, Mohan V; Brodie, Graham; Schneider, Philip A

2017-12-01

The contamination of water with silver has increased due to the widespread applications of products with silver employed as antimicrobial agent. Adsorption is a cost-effective method for silver removal from aqueous solution. In this study biochar, produced from the microwave assisted pyrolysis of biosolids, was used for silver removal from an aqueous solution. The adsorption kinetics, isotherms and thermodynamics were investigated to better understand the silver removal process by biochar. X-ray diffraction results demonstrated that silver removal was a combination two consecutive mechanisms, reduction and physical adsorption. The Langmuir model fitted the experimental data well, showing that silver removal was predominantly a surface mechanism. The thermodynamic investigation demonstrated that silver removal by biochar was an exothermic process. The final nanocomposite Ag-biochar (biochar plus silver) was used for methylene blue adsorption and photodegradation. This study showed the potential of using biochar produced from biosolids for silver removal as a promising solution to mitigate water pollution and an environmentally sustainable approach for biosolids management and re-use. Copyright © 2017 Elsevier Ltd. All rights reserved.

An investigation of in vivo wound healing activity of biologically synthesized silver nanoparticles

NASA Astrophysics Data System (ADS)

Kaler, Abhishek; Mittal, Amit Kumar; Katariya, Mahesh; Harde, Harshad; Agrawal, Ashish Kumar; Jain, Sanyog; Banerjee, Uttam Chand

2014-09-01

Therapeutic use of nano-silver is claimed to have reduced side effects and enhanced curative activity as compared to its ionic counterpart (silver ions). The present work aims to screen microbes for the synthesis of silver nanoparticles (AgNPs), to formulate the nano-silver-based Carbopol gel and evaluating its wound healing efficacy on rat model. The goal was to develop the topical formulation based on bio-nano-silver to control the infection and healing the wounds with higher efficacy. Procedure involved the use of Saccharomyces boulardii for the synthesis of silver nanoparticles in the size range of 3-10 nm and these nanoparticles were used for the preparation of Carbopol-based nano-silver gel. Highly stable Carbopol nanogel was developed with good rheological properties. The burn wound healing potential of this nano-silver gel was evaluated on SD rats via visual observation, transepidermal water loss and histology of skin. Excellent wound healing was observed with AgNPs. Biologically synthesized AgNPs-based nano-silver gel showed superior wound healing efficacy as compared to marketed formulations and silver ions.

Argyria secondary to ingestion of homemade silver solution.

PubMed

Brandt, Douglas; Park, Betty; Hoang, Mai; Jacobe, Heidi T

2005-08-01

Argyria is a rare skin disease caused by cutaneous deposition of silver granules in the skin as a result of exposure to silver substrate or ingestion of silver salt. This report describes a patient with generalized argyria caused by ingestion of homemade colloidal silver solution. The patient learned about the uses of the silver solution and its preparation at a convention for "natural medicine."

Biopersistence of silver nanoparticles in tissues from Sprague–Dawley rats

PubMed Central

2013-01-01

Silver nanoparticles are known to be distributed in many tissues after oral or inhalation exposure. Thus, understanding the tissue clearance of such distributed nanoparticles is very important to understand the behavior of silver nanoparticles in vivo. For risk assessment purposes, easy clearance indicates a lower overall cumulative toxicity. Accordingly, to investigate the clearance of tissue silver concentrations following oral silver nanoparticle exposure, Sprague–Dawley rats were assigned to 3 groups: control, low dose (100 mg/kg body weight), and high dose (500 mg/kg body weight), and exposed to two different sizes of silver nanoparticles (average diameter 10 and 25 nm) over 28 days. Thereafter, the rats were allowed to recover for 4 months. Regardless of the silver nanoparticle size, the silver content in most tissues gradually decreased during the 4-month recovery period, indicating tissue clearance of the accumulated silver. The exceptions were the silver concentrations in the brain and testes, which did not clear well, even after the 4-month recovery period, indicating an obstruction in transporting the accumulated silver out of these tissues. Therefore, the results showed that the size of the silver nanoparticles did not affect their tissue distribution. Furthermore, biological barriers, such as the blood–brain barrier and blood-testis barrier, seemed to play an important role in the silver clearance from these tissues. PMID:24059869

X-Ray Absorption Near-Edge Structure (XANES) Spectroscopy Study of the Interaction of Silver Ions with Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli

PubMed Central

Zanzen, Ulrike; Krishna, Katla Sai; Hormes, Josef

2013-01-01

Silver ions are widely used as antibacterial agents, but the basic molecular mechanism of this effect is still poorly understood. X-ray absorption near-edge structure (XANES) spectroscopy at the Ag LIII, S K, and P K edges reveals the chemical forms of silver in Staphylococcus aureus and Escherichia coli (Ag+ treated). The Ag LIII-edge XANES spectra of the bacteria are all slightly different and very different from the spectra of silver ions (silver nitrate and silver acetate), which confirms that a reaction occurs. Death or inactivation of bacteria was observed by plate counting and light microscopy. Silver bonding to sulfhydryl groups (Ag-S) in cysteine and Ag-N or Ag-O bonding in histidine, alanine, and dl-aspartic acid was detected by using synthesized silver-amino acids. Significantly lower silver-cysteine content, coupled with higher silver-histidine content, in Gram-positive S. aureus and Listeria monocytogenes cells indicates that the peptidoglycan multilayer could be buffering the biocidal effect of silver on Gram-positive bacteria, at least in part. Bonding of silver to phosphate groups was not detected. Interaction with DNA or proteins can occur through Ag-N bonding. The formation of silver-cysteine can be confirmed for both bacterial cell types, which supports the hypothesis that enzyme-catalyzed reactions and the electron transport chain within the cell are disrupted. PMID:23934494

Accuracy, precision, usability, and cost of portable silver test methods for ceramic filter factories.

PubMed

Meade, Rhiana D; Murray, Anna L; Mittelman, Anjuliee M; Rayner, Justine; Lantagne, Daniele S

2017-02-01

Locally manufactured ceramic water filters are one effective household drinking water treatment technology. During manufacturing, silver nanoparticles or silver nitrate are applied to prevent microbiological growth within the filter and increase bacterial removal efficacy. Currently, there is no recommendation for manufacturers to test silver concentrations of application solutions or filtered water. We identified six commercially available silver test strips, kits, and meters, and evaluated them by: (1) measuring in quintuplicate six samples from 100 to 1,000 mg/L (application range) and six samples from 0.0 to 1.0 mg/L (effluent range) of silver nanoparticles and silver nitrate to determine accuracy and precision; (2) conducting volunteer testing to assess ease-of-use; and (3) comparing costs. We found no method accurately detected silver nanoparticles, and accuracy ranged from 4 to 91% measurement error for silver nitrate samples. Most methods were precise, but only one method could test both application and effluent concentration ranges of silver nitrate. Volunteers considered test strip methods easiest. The cost for 100 tests ranged from 36 to 1,600 USD. We found no currently available method accurately and precisely measured both silver types at reasonable cost and ease-of-use, thus these methods are not recommended to manufacturers. We recommend development of field-appropriate methods that accurately and precisely measure silver nanoparticle and silver nitrate concentrations.

Preliminary flight prototype silver ion monitoring system

NASA Technical Reports Server (NTRS)

Brady, J.

1974-01-01

The design, fabrication, and testing of a preliminary flight prototype silver ion monitoring system based on potentiometric principles and utilizing a solid-state silver sulfide electrode paired with a pressurized double-junction reference electrode housing a replaceable electrolyte reservoir is described. The design provides automatic electronic calibration utilizing saturated silver bromide solution as a silver ion standard. The problem of loss of silver ion from recirculating fluid, its cause, and corrective procedures are reported. The instability of the silver sulfide electrode is discussed as well as difficulties met in implementing the autocalibration procedure.

Photochemical Synthesis of Silver Nanodecahedrons and Related Nanostructures for Plasmonic Field Enhancement Applications

NASA Astrophysics Data System (ADS)

Lu, Haifei

Noble-metal nanocrystals have received considerable attention in recent years for their size and shape dependent localized surface Plasmon resonances (LSPR). Various applications based on colloidal nanoparticles, such as surface enhanced Raman scattering (SERS), surface enhanced fluorescence (SEF), plasmonic sensing, photothermal therapy etc., have been broadly explored in the field of biomedicine, because of their extremely large optical scattering and absorption cross sections, as well as giant electric field enhancement on their surface. However, despite its high chemical stability, gold exhibits quite large losses and electric field enhancement is comparatively weaker than silver. Silver nanoparticles synthesized by the traditional technique only cover an LSPR ranged from 420~500 nm. On the other hand, the range of 500~660 nm, which is covered by several easily available commercial laser lines, very limited colloidal silver nanostructures with controllable size and shape have been reported, and realization of tuning the resonance to longer wavelengths is very important for the practical applications. In this thesis, a systematic study on photochemical synthesis of silver nanodecahedrons (NDs) and related nanostructures, and their plasmonic field enhancements are presented. First, the roles of chemicals and the light source during the formation of silver nanoparticles have been studied. We have also developed a preparation route for the production size-controlled silver nanodecahedrons (LSPR range 420 ~ 660 nm) in high purity. Indeed our experiments indicate that both the chemicals and the light sources can affect the shape and purity of final products. Adjusting the molar ratio between sodium citrate and silver nitrate can help to control the crystal structure following rapid reduction from sodium borohydride. Light from a blue LED (465 nm) can efficiently transform the polyvinylpyrrolidone stabilized small silver nanoparticles into silver NDs through photo excitation. These silver NDs acting as seeds can be re-grown into larger silver NDs with LSPR ranging from 490 nm to 590 nm, upon receiving LED irradiation with emission close to the LSPR of silver ND seeds, which are suspended in a precursor solution containing small silver nanoparticles. With the aid of centrifugation, silver NDs with high purity can be obtained. Furthermore, silver ND with a broad tuning range (LSPR 490 ~ 660 nm) can be synthesized from these seeds using irradiation from a 500 nm LED. Second, the optical properties of silver NDs and their SERS application for sensitive molecular detection are presented. Raman signal obtained from silver NDs show remarkable advantage over noble nanoparticles of other shaped, thus revealing their strong localized field enhancement. Experimental results demonstrate that average enhancement factor from individual silver ND may be as high as 106. In order to explore their application for biosensing and bioimaging, stable silica coated SERS tags based on silver ND producing high Raman intensity have been studied. Our experiment results indicate that 10-8 M 4-MBA in solution can be detected by silver NDs modified silicon chip through SERS. Simulation result on the geometry of silver ND/silica spacer/gold film/substrate shows that the Raman sensitivity of the NDs modified chip can be further improved with the insertion of a dielectric/conductor film between them. Finally, we present a photochemical method for the preparation of silver nanostructures preparation with the use of 633 nm laser. Silver nanostructures composed of silver nanoplates could be grown from small silver nanoparticles deposited on a glass substrate. The periodicity of the silver nanostructures is several micrometers, revealing that this photochemical method has the potential for "writing" silver pattern on a solid substrate. Raman spectroscopy has also been explored for real-time monitoring of silver nanostructure growth and SERS hotspots formation.

Antibacterial Effect of Silver Diamine Fluoride on Cariogenic Organisms.

PubMed

Lou, Yali; Darvell, Brain W; Botelho, Michael G

2018-05-01

To screen the possible antimicrobial activity of a range of clinically used, silver-based compounds on cariogenic organisms: silver diamine fluoride (SDF), silver fluoride, and silver nitrate. Preliminary screening disk-diffusion susceptibility tests were conducted on Mueller-Hinton agar plates inoculated with Streptococcus mutans, Lactobacillus acidophilus, and Actinomyces naeslundii, organisms known to be cariogenic. In order to identify which component of the silver compounds was responsible for any antibacterial (AB) effect, and to provide controls, the following were also investigated at high and low concentrations: sodium fluoride, ammonium fluoride, ammonium chloride, sodium fluoride, sodium chloride, and sodium nitrate, as well as deionized water as control. A volume of 10 pL of a test solution was dispensed onto a paper disk resting on the inoculated agar surface, and the plate incubated anaerobically at 37°C for 48 hours. The zones of inhibition were then measured. Silver diamine fluoride, silver fluoride, silver nitrate, and ammonium fluoride had significant AB effect (p < 0.05) on all three test organisms, although ammonium fluoride had no effect at low concentration; the remaining other compounds had no effect. Silver ions appear to be the principal AB agent at both high and low concentration; fluoride ions only have an AB effect at high concentration, while ammonium, nitrate, chloride and sodium ions have none. The anticaries effect of topical silver solutions appears restricted to that of the silver ions. Silver compounds, such as SDF, silver fluoride, and silver nitrate have AB effect against cariogenic organisms and these may have clinical impact in arresting or preventing dental decay. Sodium fluoride did not have AB effect under the conditions tested.

The concentration effect of capping agent for synthesis of silver nanowire by using the polyol method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Jian-Yang; Hsueh, Yu-Lee; Huang, Jung-Jie, E-mail: jjhuang@mdu.edu.tw

2014-06-01

Silver nanowires were synthesized by the polyol method employing ethylene glycol, Poly(N-vinylpyrrolidone) (PVP) and silver nitrate (AgNO{sub 3}) as the precursors. Most of the studies used metal salts (PtCl{sub 2}, NaCl) as seed precursor to synthesize the silver nanowires. In the study, the metal salts were not used and the concentration of capping agent was changed to observe the aspect ratio of silver nanowires. The experimental results showed that controlling synthesis temperature, Poly(N-vinylpyrrolidone) (PVP) molecular weight, reactant concentrations, and addition rates of AgNO{sub 3} affects the growth characteristics of silver nanowires. Field-emission scanning electron microscopy, UV–vis spectrophotometry, and X-ray diffractometrymore » were employed to characterize the silver nanowires. As increasing the concentration of PVP, the silver nanowire diameter widened and resulted in a smaller aspect ratio. We successfully prepared silver nanowires (diameter: 170 nm, length: 20 μm). The silver nanowire thin film suspension showed high transmittance, low sheet resistance, and may be used for transparent conductive film applications. - Graphical abstract: The FE-SEM image shows that nanostructures with considerable quantities of silver nanowires can also be produced when the PVP (Mw=360 K)/AgNO{sub 3} molar ratio was 2.5. - Highlights: • The polyol method was used to synthesize of silver nanowire. • The metal seed precursors were not used before synthesizing the silver nanowires. • The silver nanowire diameter and length was 170 nm and 20 μm, respectively. • Silver nanowire film with high transmittance (>85%) and low sheet resistance (<110 Ω/sq)« less

Bird Surveys at DARHT Before and During Operations: Comparison of Species Abundance and Composition and Trace Element Uptake

DOE Office of Scientific and Technical Information (OSTI.GOV)

P. R. Fresquez, D. C. Keller, C. D. Hathcock

2007-11-30

The Dual-Axis Radiographic Hydrodynamic Test (DARHT) Facility Mitigation Action Plan specifies the comparison of baseline conditions in biotic and abiotic media with those collected after operations have started. Operations at DARHT at Los Alamos National Laboratory started in 2000. In this study, the abundance and composition of birds collected near the DARHT facility from 2003 through 2006 were determined and compared to a preoperational period (1999). In addition, the levels of radionuclides and other inorganic chemicals in birds were compared to regional statistical reference levels (RSRLs). The number and diversity of bird species generally increased over preoperational levels with themore » greatest number of birds (412) and species (46) occurring in 2005. The most common bird species collected regardless of time periods were the chipping sparrow (Spizella passerina), the Virginia's warbler (Vermivora virginiae), the western bluebird (Sialia mexicana), the broad-tailed hummingbird (Selasphorus platycercus), the sage sparrow (Amphispiza belli), and the western tanager (Piranga ludoviciana). Most radionuclides, with the exception of uranium-234 and uranium-238, in (whole body) birds collected after operations began were either not detected or below RSRLs. Uranium-234 and uranium-238 concentrations in a few samples were far below screening levels and do not pose a potential unacceptable dose to the birds. In contrast, many inorganic chemicals, particularly arsenic and silver, in birds collected before and after operations began were in higher concentrations than RSRLs. Because birds (skin plus feathers) collected in the years before operations began contained higher levels of arsenic and silver than RSRLs and because there was no evidence of these metals in soil and sediment directly around the DARHT facility, the elevated levels of these metals in birds during early operations are probably not related to DARHT operations. Arsenic and silver in birds, however, have decreased over time to near background levels in 2007.« less

XPS characterization of silver exchanged ETS-10 and mordenite molecular sieves.

PubMed

Anson, A; Maham, Y; Lin, C C H; Kuznicki, T M; Kuznicki, S M

2009-05-01

Silver exchanged molecular sieves ETS-10 (Ag-ETS-10) and mordenite (Ag-mordenite) were dehydrated under vacuum at temperatures between 100 degrees C-350 degrees C. Changes in the state of the silver were studied using X-ray photoelectron spectroscopy (XPS). Silver cations in titanosilicate Ag-ETS-10 are fully reduced to Ag(0) at temperatures as low as 150 degrees C. The characteristic features of the XPS spectrum of silver in this Ag-ETS-10 species correspond to only metallic silver. The signal for metallic silver is not observed in the XPS spectrum of aluminosilicate Ag-mordenite, indicating that silver cations are not reduced, even after heating to 350 degrees C.

The dual role of silver during silicon etching in HF solution

PubMed Central

2012-01-01

It was reported that during silicon etching, silver was subjected to have a controversial role. Some researchers debate that silver protects silicon, and, at the same time, other ones confirm that silver catalyzes silicon underneath. In this paper, we give experimental results arguing the dual role that silver has during the formation of silicon nanostructures. We give a proof that the role of silver depends on the experimental details and the intrinsic properties of silver during its deposition on the silicon wafer. Through our investigations, we tracked the silver particles that indicated which mechanism is involved. Characterizations of the prepared samples were made using a scanning electron microscope. PMID:22888998

Determination of elemental distribution in green micro-algae using synchrotron radiation nano X-ray fluorescence (SR-nXRF) and electron microscopy techniques--subcellular localization and quantitative imaging of silver and cobalt uptake by Coccomyxa actinabiotis.

PubMed

Leonardo, T; Farhi, E; Boisson, A-M; Vial, J; Cloetens, P; Bohic, S; Rivasseau, C

2014-02-01

The newly discovered unicellular micro-alga Coccomyxa actinabiotis proves to be highly radio-tolerant and strongly concentrates radionuclides, as well as large amounts of toxic metals. This study helps in the understanding of the mechanisms involved in the accumulation and detoxification of silver and cobalt. Elemental distribution inside Coccomyxa actinabiotis cells was determined using synchrotron nano X-ray fluorescence spectroscopy at the ID22 nano fluorescence imaging beamline of the European Synchrotron Radiation Facility. The high resolution and high sensitivity of this technique enabled the assessment of elemental associations and exclusions in subcellular micro-algae compartments. A quantitative treatment of the scans was implemented to yield absolute concentrations of each endogenous and exogenous element with a spatial resolution of 100 nm and compared to the macroscopic content in cobalt and silver determined using inductively coupled plasma-mass spectrometry. The nano X-ray fluorescence imaging was complemented by transmission electron microscopy coupled to X-ray microanalysis (TEM-EDS), yielding differential silver distribution in the cell wall, cytosol, nucleus, chloroplast and mitochondria with unique resolution. The analysis of endogenous elements in control cells revealed that iron had a unique distribution; zinc, potassium, manganese, molybdenum, and phosphate had their maxima co-localized in the same area; and sulfur, copper and chlorine were almost homogeneously distributed among the whole cell. The subcellular distribution and quantification of cobalt and silver in micro-alga, assessed after controlled exposure to various concentrations, revealed that exogenous metals were mainly sequestered inside the cell rather than on mucilage or the cell wall, with preferential compartmentalization. Cobalt was homogeneously distributed outside of the chloroplast. Silver was localized in the cytosol at low concentration and in the whole cell excluding the nucleus at high concentration. Exposure to low concentrations of cobalt or silver did not alter the localization nor the concentration of endogenous elements within the cells. To our knowledge, this is the first report on element co-localization and segregation at the sub-cellular level in micro-algae by means of synchrotron nano X-ray fluorescence spectroscopy.

Coupling multielectrode array recordings with silver labeling of recording sites to study cervical spinal network connectivity.

PubMed

Streeter, K A; Sunshine, M D; Patel, S R; Liddell, S S; Denholtz, L E; Reier, P J; Fuller, D D; Baekey, D M

2017-03-01

Midcervical spinal interneurons form a complex and diffuse network and may be involved in modulating phrenic motor output. The intent of the current work was to enable a better understanding of midcervical "network-level" connectivity by pairing the neurophysiological multielectrode array (MEA) data with histological verification of the recording locations. We first developed a method to deliver 100-nA currents to electroplate silver onto and subsequently deposit silver from electrode tips after obtaining midcervical (C3-C5) recordings using an MEA in anesthetized and ventilated adult rats. Spinal tissue was then fixed, harvested, and histologically processed to "develop" the deposited silver. Histological studies verified that the silver deposition method discretely labeled (50-μm resolution) spinal recording locations between laminae IV and X in cervical segments C3-C5. Using correlative techniques, we next tested the hypothesis that midcervical neuronal discharge patterns are temporally linked. Cross-correlation histograms produced few positive peaks (5.3%) in the range of 0-0.4 ms, but 21.4% of neuronal pairs had correlogram peaks with a lag of ≥0.6 ms. These results are consistent with synchronous discharge involving mono- and polysynaptic connections among midcervical neurons. We conclude that there is a high degree of synaptic connectivity in the midcervical spinal cord and that the silver-labeling method can reliably mark metal electrode recording sites and "map" interneuron populations, thereby providing a low-cost and effective tool for use in MEA experiments. We suggest that this method will be useful for further exploration of midcervical network connectivity. NEW & NOTEWORTHY We describe a method that reliably identifies the locations of multielectrode array (MEA) recording sites while preserving the surrounding tissue for immunohistochemistry. To our knowledge, this is the first cost-effective method to identify the anatomic locations of neuronal ensembles recorded with a MEA during acute preparations without the requirement of specialized array electrodes. In addition, evaluation of activity recorded from silver-labeled sites revealed a previously unappreciated degree of connectivity between midcervical interneurons. Copyright © 2017 the American Physiological Society.

Escherichia coli under Ionic Silver Stress: An Integrative Approach to Explore Transcriptional, Physiological and Biochemical Responses

PubMed Central

Saulou-Bérion, Claire; Gonzalez, Ignacio; Enjalbert, Brice; Audinot, Jean-Nicolas; Fourquaux, Isabelle; Jamme, Frédéric; Cocaign-Bousquet, Muriel; Mercier-Bonin, Muriel; Girbal, Laurence

2015-01-01

For a better understanding of the systemic effect of sub-lethal micromolar concentrations of ionic silver on Escherichia coli, we performed a multi-level characterization of cells under Ag+-mediated stress using an integrative biology approach combining physiological, biochemical and transcriptomic data. Physiological parameters, namely bacterial growth and survival after Ag+ exposure, were first quantified and related to the accumulation of intracellular silver, probed for the first time by nano secondary ion mass spectroscopy at sub-micrometer lateral resolution. Modifications in E. coli biochemical composition were evaluated under Ag+-mediated stress by in situ synchrotron Fourier-transform infrared microspectroscopy and a comprehensive transcriptome response was also determined. Using multivariate statistics, correlations between the physiological parameters, the extracellular concentration of AgNO3 and the intracellular silver content, gene expression profiles and micro-spectroscopic data were investigated. We identified Ag+-dependent regulation of gene expression required for growth (e.g. transporter genes, transcriptional regulators, ribosomal proteins), for ionic silver transport and detoxification (e.g. copA, cueO, mgtA, nhaR) and for coping with various types of stress (dnaK, pspA, metA,R, oxidoreductase genes). The silver-induced shortening of the acyl chain of fatty acids, mostly encountered in cell membrane, was highlighted by microspectroscopy and correlated with the down-regulated expression of genes involved in fatty acid transport (fadL) and synthesis/modification of lipid A (lpxA and arnA). The increase in the disordered secondary structure of proteins in the presence of Ag+ was assessed through the conformational shift shown for amides I and II, and further correlated with the up-regulated expression of peptidase (hfq) and chaperone (dnaJ), and regulation of transpeptidase expression (ycfS and ycbB). Interestingly, as these transpeptidases act on the structural integrity of the cell wall, regulation of their expression may explain the morphological damage reported under Ag+-mediated stress. This result clearly demonstrates that the cell membrane is a key target of ionic silver. PMID:26696268

45 CFR 156.400 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... to the requirements of § 156.130(a). A standard plan at the bronze, silver, gold, or platinum level..., and a standard platinum plan, respectively. Zero cost sharing plan variation means, with respect to a...

Combining surface enhanced Raman scattering (SERS) and high-performance thin-layer chromatography (HPTLC)

NASA Astrophysics Data System (ADS)

Koglin, E.

A new method for preparing SERS active surfaces using silver colloidal spheres deposited on HPTLC plates, used for thin-layer chromatography, is discussed in detail. The sensitivity of these activated HPTLC plates is so high that in-situ vibrational investigations of chromatogram spots are possible at the nanogram level. The HPTLC/SERS spectra of purine, benzoic acid and 1-nitro-pyrene adsorbed on silver colloidal activated silica gel plates are measured in the nanogram region. In addition we also report in this paper on the results of a feasibility study performed to evaluate the analytical potential of micro-Raman spectroscopy (triple monochromator, multichannel detection system) in SERS/HPTLC spot characterization. It permits the acquisition of Raman spectra from HPTLC spots down to 1 μm in size or other forms of microsamples approaching the picogram level in mass.

Effect of silver-doping on the crystal structure, morphology and photocatalytic activity of TiO2 nanofibers

NASA Astrophysics Data System (ADS)

Barakat, N. A. M.; Kim, H. Y.

2012-09-01

In this study, effect of sliver-doping on the crystal structure, the nanofibrous morphology and the photocatalytic activity of titanium oxide nanofibers have been investigated. Silver-doped TiO2 nanofibers having different silver contents were prepared by calcination of electrospun nanofiber mats consisting of silver nitrate, titanium isopropoxide and poly(vinyl acetate) at 600 °C. The results affirmed formation of silver-doped TiO2 nanofibers composed of anatase and rutile when the silver nitrate content in the original electrospun solution was more than 3 wt%. The rutile phase content was directly proportional with the AgNO3 concentration in the electrospun solution. Negative impact of the silver-doping on the nanofibrous morphology was observed as increase the silver content caused to decrease the aspect ratio, i.e. producing nanorods rather nanofibers. However, silver-doping leads to modify the surface roughness. Study of the photocatalytic degradation of methylene blue dye clarified that increase the silver content strongly enhances the dye oxidation process.

Electrically Conductive Silver Paste Obtained by Use of Silver Neodecanoate as Precursor

NASA Astrophysics Data System (ADS)

Shen, Longguang; Liu, Jianguo; Zeng, Xiaoyan; Ren, Zhao

2015-02-01

An electrically conductive silver paste has been prepared from an organometallic compound, silver neodecanoate, as silver precursor. The precursor was highly soluble in organic solvents and decomposed into metallic silver at low sintering temperatures (<200°C). Thermogravimetric analysis showed the silver content of the paste was approximately 25 wt.%. Viscosity studies indicated the paste was a pseudoplastic liquid with viscosity in the range 6.5-9 Pa s. The paste was compatible with the micro-pen direct-writing process, enabling production of silver lines on a substrate. The electrical resistivity of the silver lines was 9 × 10-6 Ω cm after sintering at 115°C for 60 min, 5.8 × 10-6 Ω cm when sintered at 150°C for 60 min, and 3 × 10-6 Ω cm when sintered above 300°C, values which are similar to those of bulk silver. Hence, the prepared paste can be successfully used on flexible substrates such as polymers.

Development of an optofluidic SERS-based biomedical sensor

NASA Astrophysics Data System (ADS)

Walton, Brian; Huang, Po-Jung; Kameoka, Jun; Deutz, Nicolaas; Coté, Gerard L.

2016-03-01

Rapid assessment of radiation exposure to sensitive organs like the gut is extremely important for large populations exposed to ionized radiation, for instance during warfare. Recent results have shown that plasma citrulline levels appear to track gut function after irradiation levels in mice and humans. The current ways to monitor blood citrulline levels are bulky, laborious, time-consuming and expensive methods. Therefore, an optofludic point-of-care (POC) system using surface enhanced Raman spectroscopy to measure plasma citrulline as a marker for radiation exposure that overcomes the above issues is being developed. As a first step toward development of this system four colloidal nanoparticles, spherical gold, silver cubes, silica-gold nanoshells, and silver-gold nanocages have been analyzed for use in the POC system. Transmission electron microscopy (TEM) images have been taken of each nanoparticle to visualize the morphology of the nanoparticles, which is vital for SERS. Ultraviolet-visible (UV/Vis) spectroscopy was also collected to verify the extinction spectra for each nanoparticle was in resonance with the excitation wavelength. The nanoparticles were functionalized with mercaptobenzoic acid (MBA), a Raman reporter molecule, and SERS spectra were collected to determine which has better utility in a novel micro-to-nanochannel. The data showed that the silver nanocubes have a larger enhancement factor than the gold nanospheres, nanoshells, or nanocages. Currently, these nanocubes are being functionalized with the citulline for assessing the concentration sensitivity and dynamic range for ultimate use as a marker for radiation.

Magnetically assisted surface-enhanced raman scattering selective determination of dopamine in an artificial cerebrospinal fluid and a mouse striatum using Fe(3)O(4)/Ag nanocomposite.

PubMed

Ranc, Vaclav; Markova, Zdenka; Hajduch, Marian; Prucek, Robert; Kvitek, Libor; Kaslik, Josef; Safarova, Klara; Zboril, Radek

2014-03-18

The dopaminergic neural system is a crucial part of the brain responsible for many of its functions including mood, arousal, and other roles. Dopamine is the key neurotransmitter of this system, and a determination of its level presents a demanding task needed for a deeper understanding of the processes, even pathological, involving this brain part. In this work, we present a method for a fast analysis of dopamine levels in samples of cerebrospinal fluid and mouse striatum. The method is based on a nanocomposite composed of magnetite and silver nanoparticles, whose surface is modified with iron nitriloacetic acid (Fe-NTA)-a dopamine-selective compound. The magnetic properties of this nanocomposite enable simple separation of targeted molecules from a complex matrix while the silver acts as a platform for surface-enhanced Raman scattering (SERS). Silver and magnetite nanoparticles are joined by carboxymethyl chitosan, useful in biological environments and enhancing the sensitivity due to the presence of carboxyl groups. This system reveals a good stability and reproducibility. Moreover, rapid and simple quantitative experiments show an improvement in the detection of dopamine levels in biological assays at low femtomolar concentrations. The comparative data performed with clinical samples of mouse striatum show that the developed magnetic SERS is a strong alternative to conventional high-performance liquid chromatography-mass spectrometry (HPLC-MS) with even several superior aspects including faster and cheaper analysis and no necessity of sample preconcentration or derivatization.

Antibacterial activity of silver and zinc nanoparticles against Vibrio cholerae and enterotoxic Escherichia coli

PubMed Central

Salem, Wesam; Leitner, Deborah R.; Zingl, Franz G.; Schratter, Gebhart; Prassl, Ruth; Goessler, Walter; Reidl, Joachim; Schild, Stefan

2015-01-01

Vibrio cholerae and enterotoxic Escherichia coli (ETEC) remain two dominant bacterial causes of severe secretory diarrhea and still a significant cause of death, especially in developing countries. In order to investigate new effective and inexpensive therapeutic approaches, we analyzed nanoparticles synthesized by a green approach using corresponding salt (silver or zinc nitrate) with aqueous extract of Caltropis procera fruit or leaves. We characterized the quantity and quality of nanoparticles by UV–visible wavelength scans and nanoparticle tracking analysis. Nanoparticles could be synthesized in reproducible yields of approximately 108 particles/ml with mode particles sizes of approx. 90–100 nm. Antibacterial activity against two pathogens was assessed by minimal inhibitory concentration assays and survival curves. Both pathogens exhibited similar resistance profiles with minimal inhibitory concentrations ranging between 5 × 105 and 107 particles/ml. Interestingly, zinc nanoparticles showed a slightly higher efficacy, but sublethal concentrations caused adverse effects and resulted in increased biofilm formation of V. cholerae. Using the expression levels of the outer membrane porin OmpT as an indicator for cAMP levels, our results suggest that zinc nanoparticles inhibit adenylyl cyclase activity. This consequently deceases the levels of this second messenger, which is a known inhibitor of biofilm formation. Finally, we demonstrated that a single oral administration of silver nanoparticles to infant mice colonized with V. cholerae or ETEC significantly reduces the colonization rates of the pathogens by 75- or 100-fold, respectively. PMID:25466205

Atomic-absorption determination of mercury in geological materials by flame and carbon-rod atomisation after solvent extraction and using co-extracted silver as a matrix modifier

USGS Publications Warehouse

Sanzolone, R.F.; Chao, T.T.

1983-01-01

Based on modifications and expansion of the original Tindall's solvent extraction flame atomic-absorption procedure, an atomic-absorption spectrophotometric method has been developed for the determination of mercury in geological materials. The sample is digested with nitric and hydrochloric acids in a boiling water-bath. The solution is made ammoniacal and potassium iodide and silver nitrate are added. The mercury is extracted into isobutyl methyl ketone as the tetraiodomercurate(ll). Added silver is co-extracted with mercury and serves as a matrix modifier in the carbon-rod atomiser. The mercury in the isobutyl methyl ketone extract may be determined by either the flame- or the carbon-rod atomisation method, depending on the concentration level. The limits of determination are 0.05-10 p.p.m. of mercury for the carbon-rod atomisation and 1 -200 p.p.m. of mercury for the flame atomisation. Mercury values for reference samples obtained by replicate analyses are in good agreement with those reported by other workers, with relative standard deviations ranging from 2.3 to 0.9%. Recoveries of mercury spiked at two levels were 93-106%. Major and trace elements commonly found in geological materials do not interfere.

Aeromonas caviae alters the cytosolic and mitochondrial creatine kinase activities in experimentally infected silver catfish: Impairment on renal bioenergetics.

PubMed

Baldissera, Matheus D; Souza, Carine F; Júnior, Guerino B; Verdi, Camila Marina; Moreira, Karen L S; da Rocha, Maria Izabel U M; da Veiga, Marcelo L; Santos, Roberto C V; Vizzotto, Bruno S; Baldisserotto, Bernardo

2017-09-01

Cytosolic and mitochondrial creatine kinases (CK), through the creatine kinase-phosphocreatine (CK/PCr) system, provide a temporal and spatial energy buffer to maintain cellular energy homeostasis. However, the effects of bacterial infections on the kidney remain poorly understood and are limited only to histopathological analyses. Thus, the aim of this study was to investigate the involvement of cytosolic and mitochondrial CK activities in renal energetic homeostasis in silver catfish experimentally infected with Aeromonas caviae. Cytosolic CK activity decreased in infected animals, while mitochondrial CK activity increased compared to uninfected animals. Moreover, the activity of the sodium-potassium pump (Na + , K + -ATPase) decreased in infected animals compared to uninfected animals. Based on this evidence, it can be concluded that the inhibition of cytosolic CK activity by A. caviae causes an impairment on renal energy homeostasis through the depletion of adenosine triphosphate (ATP) levels. This contributes to the inhibition of Na + , K + -ATPase activity, although the mitochondrial CK activity acted in an attempt to restore the cytosolic ATP levels through a feedback mechanism. In summary, A. caviae infection causes a severe energetic imbalance in infected silver catfish, which may contribute to disease pathogenesis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Facile fabrication of rice husk based silicon dioxide nanospheres loaded with silver nanoparticles as a rice antibacterial agent

PubMed Central

Cui, Jianghu; Liang, You; Yang, Desong; Liu, Yingliang

2016-01-01

Bacterial leaf blight of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major disease of rice, leading to reduction in production by 10–50%. In order to control this disease, various chemical bactericides have been used. Wide and prolonged application of chemical bactericides resulted in the resistant strain of Xoo that was isolated from rice. To address this problem, we were searching for an environmentally friendly alternative to the commonly used chemical bactericides. In this work, we demonstrate that silicon dioxide nanospheres loaded with silver nanoparticles (SiO2-Ag) can be prepared by using rice husk as base material precursor. The results of the antibacterial tests showed that SiO2-Ag composites displayed antibacterial activity against Xoo. At cellular level, the cell wall/membrane was damaged and intercellular contents were leaked out by slow-releasing of silver ions from SiO2-Ag composites. At molecular level, this composite induced reactive oxygen species production and inhibited DNA replication. Based on the results above, we proposed the potential antibacterial mechanism of SiO2-Ag composites. Moreover, the cytotoxicity assay indicated that the composites showed mild toxicity with rice cells. Thus, this work provided a new strategy to develop biocide derived from residual biomass. PMID:26888152

3-D printed 2.4 GHz rectifying antenna for wireless power transfer applications

NASA Astrophysics Data System (ADS)

Skinner, Matthew

In this work, a 3D printed rectifying antenna that operates at the 2.4GHz WiFi band was designed and manufactured. The printed material did not have the same properties of bulk material, so the printed materials needed to be characterized. The antenna and rectifying circuit was printed out of Acrylonitrile Butadiene Styrene (ABS) filament and a conductive silver paste, with electrical components integrated into the circuit. Before printing the full rectifying antenna, each component was printed and evaluated. The printed antenna operated at the desired frequency with a return loss of -16 dBm with a bandwidth of 70MHz. The radiation pattern was measured in an anechoic chamber with good matching to the model. The rectifying circuit was designed in Ansys Circuit Simulation using Schottky diodes to enable the circuit to operate at lower input power levels. Two rectifying circuits were manufactured, one by printing the conductive traces with silver ink, and one with traces made from copper. The printed silver ink is less conductive than the bulk copper and therefore the output voltage of the printed rectifier was lower than the copper circuit. The copper circuit had an efficiency of 60% at 0dBm and the printed silver circuit had an efficiency of 28.6% at 0dBm. The antenna and rectifying circuits were then connected to each other and the performance was compared to a fully printed integrated rectifying antenna. The rectifying antennas were placed in front of a horn antenna while changing the power levels at the antenna. The efficiency of the whole system was lower than the individual components but an efficiency of 11% at 10dBm was measured.

A sandwich-type electrochemical immunosensor based on in situ silver deposition for determination of serum level of HER2 in breast cancer patients.

PubMed

Shamsipur, Mojtaba; Emami, Mahdi; Farzin, Leila; Saber, Reza

2018-04-30

The sensitive quantification of Human Epidermal growth factor Receptor 2 (HER2), as a key prognostic tumor marker, plays a critical role in screening, early diagnosis and management of breast cancer. This paper describes a sandwich-type immunoassay with silver signal enhancement strategy for highly sensitive detection of HER2. For this purpose, the target capturing step was designed by functionalization of 3-aminopropyltrimethoxysilane coated magnetite nanoparticles with antibody (antiHER2/APTMS-Fe 3 O 4 ), as a platform bioconjugate (PB), and immobilized at a bare GCE. Then, in the presence of label-free immunosensor, the PB was covered by magnetic gold nanoparticles self-assembled with thiolated antibodies (antiHER2/Hyd@AuNPs-APTMS-Fe 3 O 4 ) containing chemically reduced silver ions, as a label bioconjugate (LB). Under optimum conditions, a linear relationship between the differential pulse voltammetric (DPV) stripping signal of silver and the logarithm of HER2 concentrations was obtained in the range of 5.0 × 10 -4 -50.0ngmL -1 (R 2 = 0.9906) with a detection limit of 2.0 × 10 -5 ngmL -1 . The effectiveness of this protocol was evaluated experimentally through employing of designed immunosensor for detection of the serum level of tumor marker. The good consistency of the results with those obtained by the enzyme-linked immunosorbent assay (ELISA) conventional method (p-value of < 0.05) showed that this immunosensor can be applied for the testing of HER2 in clinical samples of breast cancer patients. Copyright © 2017 Elsevier B.V. All rights reserved.

A long-term study examining the antibacterial effectiveness of Agion silver zeolite technology on door handles within a college campus.

PubMed

Potter, B A; Lob, M; Mercaldo, R; Hetzler, A; Kaistha, V; Khan, H; Kingston, N; Knoll, M; Maloy-Franklin, B; Melvin, K; Ruiz-Pelet, P; Ozsoy, N; Schmitt, E; Wheeler, L; Potter, M; Rutter, M A; Yahn, G; Parente, D H

2015-02-01

Laboratory studies have shown that small concentrations of silver are effective at inhibiting the growth micro-organisms through the disruption of important cell structures and processes. The additional ability to incorporate silver into surfaces has increased the usage of silver in the medical field and expanded its use into the consumer market. To understand the impact of increased silver-containing antimicrobial use, it is important to determine whether silver-based consumer goods are effective at reducing bacterial populations. Our study examined the antibacterial effectiveness of Agion silver zeolite technology applied to 25 silver- and control-coated door handles across a college campus. Door handles were sampled for 6 week periods in both the fall and spring semester, and bacteria were cultured and enumerated on tryptic soy agar (TSA), MacConkey agar (MAC) and mannitol salt agar (MSA). A significant difference was observed between the bacterial populations isolated from silver- and control-coated door handles after 3 years. However, bacteria were consistently isolated from silver-coated door handles suggesting that the silver zeolite was only effective against a portion of the bacterial populations, and further studies are necessary to determine the identities of the isolated bacteria and the prevalence of silver resistance. © 2014 The Society for Applied Microbiology.

Synthesis and characterization of silver nanowires with zigzag morphology in N, N-dimethylformamide

NASA Astrophysics Data System (ADS)

He, Xin; Zhao, Xiujian; Chen, Yunxia; Feng, Jinyang; Sun, Zhenya

2007-08-01

Zigzag silver nanowires with a uniform diameter of 20±5 nm were prepared by reducing silver nitrate (AgNO 3) with N, N-dimethylformamide (DMF) in the presence of tetrabutyl titanate (TBT) and acetylacetone (AcAc) at 373 K for 18 h. X-ray and selected area electron diffraction (XRD and SAED) patterns reveal that the prepared product is made of pure silver with face centered cubic structure. Transmission electron microscopy (TEM) investigations suggest that the amount of silver nanowires is enhanced with increase in reaction time, and the end-to-end assemblies of silver nanorods are observed during the reaction process. After 18 h reaction, silver nanowires with zigzag morphology are obtained. In this paper, a possible growth process of silver nanowires with this interesting shape is described. Silver nanoparticles with small sizes were obtained by reducing Ag + ions with DMF, providing seeds for homogeneous growth of silver nanorods. With the extending reaction time, the synthesized silver nanorods were connected in an end-to-end manner, and the interface between the connections of two nanorods gradually disappeared. The final product shows zigzag morphology with various angles. The angles between two connecting straight parts of zigzag nanowires exhibit an alterable range of 74-151°. These silver nanowires show tremendous potential applications in future nanoscale electronic circuits.

Exposure-related health effects of silver and silver compounds: a review.

PubMed

Drake, Pamela L; Hazelwood, Kyle J

2005-10-01

A critical review of studies examining exposures to the various forms of silver was conducted to determine if some silver species are more toxic than others. The impetus behind conducting this review is that several occupational exposure limits and guidelines exist for silver, but the values for each depend on the form of silver as well as the individual agency making the recommendations. For instance, the American Conference of Governmental Industrial Hygienists has established separate threshold limit values for metallic silver (0.1 mg/m3) and soluble compounds of silver (0.01 mg/m3). On the other hand, the permissible exposure limit (PEL) recommended by the Occupational Safety and Health Administration and the Mine Safety and Health Administration and the recommended exposure limit set by the National Institute for Occupational Safety and Health is 0.01 mg/m3 for all forms of silver. The adverse effects of chronic exposure to silver are a permanent bluish-gray discoloration of the skin (argyria) or eyes (argyrosis). Most studies discuss cases of argyria and argyrosis that have resulted primarily from exposure to the soluble forms of silver. Besides argyria and argyrosis, exposure to soluble silver compounds may produce other toxic effects, including liver and kidney damage, irritation of the eyes, skin, respiratory, and intestinal tract, and changes in blood cells. Metallic silver appears to pose minimal risk to health. The current occupational exposure limits do not reflect the apparent difference in toxicities between soluble and metallic silver; thus, many researchers have recommended that separate PELs be established.

A perspective on the hemolytic activity of chemical and green-synthesized silver and silver oxide nanoparticles

NASA Astrophysics Data System (ADS)

Ashokraja, C.; Sakar, M.; Balakumar, S.

2017-10-01

We report the hemolysis properties of silver and silver oxide nanoparticles (NPs) prepared by chemical and green-synthesis methods. The prepared silver and silver oxide NPs were analyzed using UV-vis spectroscopy to confirm their formation by characterizing their surface plasmon resonance (SPR) and absorption band peaks respectively. The Fourier transmission infrared (FTIR) spectra of the materials showed the characteristic functional groups corresponding to the molecules present in leaf extracts, which is proposed to be acted as reducing and capping agents that are also found on the surface of silver and silver oxide nanoparticles that synthesized via green-synthesis method. Zeta potential analysis revealed the surface charge and stability of the prepared NPs. HRTEM images showed almost spherical shape nanoparticles with an average size of 15.2 and 31.5 nm for wet chemical synthesized silver and silver oxide nanoparticles respectively. In the case of green synthesized silver and silver oxide nanoparticles, it was observed to be 19.4 and 30.4 nm respectively. The order of hemolysis efficacy of the materials is found to be as follows: chemically synthesized Ag2O>  chemically synthesized Ag NPs followed by green-synthesized Ag2O and green-synthesized Ag NPs which showed almost similar hemolysis with respect to concentration. The relatively stable nature of the silver NPs could be attributed to their lower hemolysis efficacy, while the increased lysis properties of silver oxide could be attributed due to reductive/oxidative processes that give rise to the hemolysis through interfacial charge interactions with RBCs.

Range estimates and habitat use of invasive Silver Carp (Hypophthalmichthys molitrix): Evidence of sedentary and mobile individuals

USGS Publications Warehouse

Prechtel, Austin R.; Coulter, Alison A.; Etchison, Luke; Jackson, P. Ryan; Goforth, Reuben R.

2018-01-01

Unregulated rivers provide unobstructed corridors for the dispersal of both native and invasive species. We sought to evaluate range size and habitat use of an invasive species (Silver Carp, Hypophthalmichthys molitrix) in an unimpounded river reach (Wabash River, IN), to provide insights into the dispersal of invasive species and their potential overlap with native species. We hypothesized that range size would increase with fish length, be similar among sexes, and vary annually while habitats used would be deeper, warmer, lower velocity, and of finer substrate. Silver Carp habitat use supported our hypotheses but range size did not vary with sex or length. 75% home range varied annually, suggesting that core areas occupied by individuals may change relative to climate-based factors (e.g., water levels), whereas broader estimates of range size remained constant across years. Ranges were often centered on landscape features such as tributaries and backwaters. Results of this study indicate habitat and landscape features as potential areas where Silver Carp impacts on native ecosystems may be the greatest. Observed distribution of range sizes indicates the presence of sedentary and mobile individuals within the population. Mobile individuals may be of particular importance as they drive the spread of the invasive species into new habitats.

Novel regenerable sorbent for mercury capture from flue gases of coal-fired power plant.

PubMed

Liu, Yan; Kelly, David J A; Yang, Hongqun; Lin, Christopher C H; Kuznicki, Steve M; Xu, Zhenghe

2008-08-15

A natural chabazite-based silver nanocomposite (AgMC) was synthesized to capture mercury from flue gases of coal-fired power plants. Silver nanoparticles were engineered on zeolite through ion-exchange of sodium ions with silver ions, followed by thermal annealing. Mercury sorption test using AgMC was performed at various temperatures by exposing it to either pulse injection of mercury or continuous mercury flow. A complete capture of mercury by AgMC was achieved up to a capture temperature of 250 degrees C. Nano silver particles were shown to be the main active component for mercury capture by amalgamation mechanism. Compared with activated carbon-based sorbents, the sorbent prepared in this study showed a much higher mercury capture capacity and upper temperature limit for mercury capture. More importantly, the mercury captured by the spent AgMC could be easily released for safe disposal and the sorbent regenerated by simple heating at 400 degrees C. Mercury capture tests performed in real flue gas environment showed a much higher level of mercury capture by AgMC than by other potential mercury sorbents tested. In our mercury capture tests, the AgMC exposed to real flue gases showed an increased mercury capture efficiency than the fresh AgMC.

Relationship between interphasic nucleolar organizer regions and growth rate in two neuroblastoma cell lines.

PubMed Central

Derenzini, M.; Pession, A.; Farabegoli, F.; Trerè, D.; Badiali, M.; Dehan, P.

1989-01-01

The relationship between the quantity of silver-stained interphasic nucleolar organizer regions (NORs) and nuclear synthetic activity, caryotype, and growth rate was studied in two established neuroblastoma cell lines (CHP 212 and HTB 10). Statistical analysis of silver-stained NORs revealed four times as many in CHP 212 cells compared with HTB 10 cells. No difference was observed in the ribosomal RNA synthesis between the two cell lines. The caryotype index was 1.2 for CHP 212 and 1.0 for HTB 10 cells. The number of chromosomes carrying NORs and the quantity of ribosomal genes was found to be the same for the two cell lines. Doubling time of CHP 212 cells was 20 hours compared with 54 hours for HTB 10 cells. In CHP 212 cells bindering of cell duplication by serum deprivation induced a progressive lowering (calculated at 48, 72, and 96 hours) of the quantity of silver-stained interphasic NORs. Recovery of duplication by new serum addition induced, after 24 hours, an increase of the quantity of silver-stained interphasic NORs up to control levels. In the light of available data, these results indicate that the quantity of interphasic NORs is strictly correlated only to the growth rate of the cell. Images Figure 2 Figure 3 Figure 4 PMID:2705511

Characterization of engineered nanoparticles in commercially available spray disinfectant products advertised to contain colloidal silver

EPA Science Inventory

Given the potential for human exposure to silver nanoparticles from spray disinfectants and dietary supplements, we characterized the silver-containing nanoparticles in 22 commercial products that advertised the use of silver or colloidal silver as the active ingredient. Characte...

Protective Gel Composition for Treating White Phosphorus Burn Wounds.

DTIC Science & Technology

Water soluble hydrogels of alkali metal alginate and glycerin containing 0.01% to 1% cupric ( copper ) sulfate pentahydrate or silver salts such as...burns. Cupric sulfate pentahydrate of silver salts such as silver acetate, silver lactate monohydrate and silver nitrate in the gel reacts with the

Synergy of Silver Nanoparticles and Aztreonam against Pseudomonas aeruginosa PAO1 Biofilms

PubMed Central

Park, Amber J.; Vis, Emily C.; Harris, Robert J.

2014-01-01

Pathogenic bacterial biofilms, such as those found in the lungs of patients with cystic fibrosis (CF), exhibit increased antimicrobial resistance, due in part to the inherent architecture of the biofilm community. The protection provided by the biofilm limits antimicrobial dispersion and penetration and reduces the efficacy of antibiotics that normally inhibit planktonic cell growth. Thus, alternative antimicrobial strategies are required to combat persistent infections. The antimicrobial properties of silver have been known for decades, but silver and silver-containing compounds have recently seen renewed interest as antimicrobial agents for treating bacterial infections. The goal of this study was to assess the efficacy of citrate-capped silver nanoparticles (AgNPs) of various sizes, alone and in combination with the monobactam antibiotic aztreonam, to inhibit Pseudomonas aeruginosa PAO1 biofilms. Among the different sizes of AgNPs examined, 10-nm nanoparticles were most effective in inhibiting the recovery of P. aeruginosa biofilm cultures and showed synergy of inhibition when combined with sub-MIC levels of aztreonam. Visualization of biofilms treated with combinations of 10-nm AgNPs and aztreonam indicated that the synergistic bactericidal effects are likely caused by better penetration of the small AgNPs into the biofilm matrix, which enhances the deleterious effects of aztreonam against the cell envelope of P. aeruginosa within the biofilms. These data suggest that small AgNPs synergistically enhance the antimicrobial effects of aztreonam against P. aeruginosa in vitro, and they reveal a potential role for combinations of small AgNPs and antibiotics in treating patients with chronic infections. PMID:25049240

Factors affecting the silver corrosion performance of jet fuel from the Merox process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Viljoen, C.L.; Hietkamp, S.; Marais, B.

1995-05-01

The Natref refinery at Sasolburg, South Africa, which is 63,6% owned by Sasol and 36,5% by Total, is producing Jet A-1 fuel at a rate of 80 m{sup 3}/h by means of a UOP Merox process. A substantial part of the crude oil slate is made up from crudes which have been stored for considerable times in underground mines. Since the 1970`s, Natref has experienced sporadic non-conformance of its treated jet fuel to the silver corrosion (IP 227) test. Various causes and explanations for the sporadic silver corrosion occurrence have been put forward but a direct causal link has remainedmore » obscure. The paper addresses these possible causes for silver corrosion and some of the process changes which have been made to alleviate the problem. Emphasis is placed on the most recent approaches which were taken to identify the origin of the sporadic silver corrosion. An inventory of all the potential causes was made, such a bacterial action, elemental sulphur formation in storage, etc. and experiments designed to test the validity of these causes, are discussed. A statistical evaluation which was done of the historical process data over a 2 year period, failed to link the use of mine crudes directly to Ag-corrosion occurrence. However, a correlation between elemental sulphur and H{sub 2}S levels in the feed to the Merox reactor and Ag-corrosion was observed. Finally, the outcome of the experiments are discussed, as well as the conclusions which were reached from the observed results.« less

Mycorrhizal fungi influence on silver uptake and membrane protein gene expression following silver nanoparticle exposure

NASA Astrophysics Data System (ADS)

Noori, Azam; White, Jason C.; Newman, Lee A.

2017-02-01

The rapid growth of nanotechnology and the high demand for nanomaterial use have greatly increased the risk of particle release into the environment. Understanding nanomaterial interactions with crop species and their associated microorganisms is critical to food safety and security. In the current study, tomato was inoculated with mycorrhizal fungi and subsequently exposed to 12, 24, or 36 mg/kg of 2- or 15-nm silver nanoparticles (Ag-NPs). Mycorrhizal (M) and non-mycorrhizal (NM) tomatoes exposed to 36 mg/kg of 2-nm Ag-NPs accumulated 1300 and 1600 μg/g silver in their tissues, respectively. Mycorrhizal plants accumulated 14% less silver compared to non-mycorrhizal plants. To begin to understand the mechanisms by which plants accumulate NPs, the expression of two aquaporin channel genes, the plasma membrane intrinsic protein (PIP) and the tonoplast membrane intrinsic protein (TIP), and one potassium channel (KC) gene were studied. In non-mycorrhizal plants, the expression of KC, PIP, and TIP was eight, five, and nine times higher than the control, respectively. These expressions for mycorrhizal plants were 5.8, 3.5, and 2 times higher than controls, respectively. The expression of KC and PIP, which are located on the plasma membrane, was 3.5 and 2.5, respectively, times higher than TIP, which is located on the tonoplast. PIP expression was significantly higher in NM tomatoes exposed to 12 mg/kg of 2-nm Ag-NPs compared to M plants. These results show that mycorrhizal colonization decreases Ag accumulation in NP-exposed plants and also moderates changes in expression level of membrane transport proteins.

Stable silver/biopolymer hybrid plasmonic nanostructures for high performance surface enhanced raman scattering (SERS)

USDA-ARS?s Scientific Manuscript database

Silver/biopolymer nanoparticles were prepared by adding 100 mg silver nitrate to 2% polyvinyl alcohol solution and reduced the silver nitrate into silver ion using 2 % trisodium citrate for high performance Surface Enhanced Raman Scattering (SERS) substrates. Optical properties of nanoparticle were ...

Synthesis and characterization of bactericidal silver nanoparticles using cultural filtrate of simulated microgravity grown Klebsiella pneumoniae.

PubMed

Kalpana, Duraisamy; Lee, Yang Soo

2013-03-05

Silver nanoparticles were synthesized by biological method using cultural filtrate of Klebsiella pneumoniae cultured under simulated microgravity and silver nitrate solution as precursor. The nanoparticles exhibited typical plasmon absorption maximum of silver nanoparticles between 405 and 407 nm. Spherical silver nanoparticles were found to have size between 15 and 37 nm by TEM analysis. XRD pattern corresponding to planes (111), (200), (220) (311) revealed the crystalline nature of the biosynthesized silver nanoparticles. FTIR spectrum proposed stabilization of silver nanoparticles by the protein molecules present in the cultural filtrate. The silver nanoparticles exhibited high bactericidal activity against Salmonella enterica, Escherichia coli and moderate bactericidal activity against Streptococcus pyogenes. Copyright © 2012 Elsevier Inc. All rights reserved.

Antibacterial properties of Ag-doped hydroxyapatite layers prepared by PLD method

NASA Astrophysics Data System (ADS)

Jelínek, Miroslav; Kocourek, Tomáš; Jurek, Karel; Remsa, Jan; Mikšovský, Jan; Weiserová, Marie; Strnad, Jakub; Luxbacher, Thomas

2010-12-01

Thin hydroxyapatite (HA), silver-doped HA and silver layers were prepared using a pulsed laser deposition method. Doped layers were ablated from silver/HA targets. Amorphous and crystalline films of silver concentrations of 0.06 at.%, 1.2 at.%, 4.4 at.%, 8.3 at.% and 13.7 at.% were synthesized. Topology was studied using scanning electron microscopy and atomic force microscopy. Contact angle and zeta potential measurements were conducted to determine the wettability, surface free energy and electric surface properties. In vivo measurement (using Escherichia coli cells) of antibacterial properties of the HA, silver-doped HA and silver layers was carried out. The best antibacterial results were achieved for silver-doped HA layers of silver concentration higher than 1.2 at.%.

Sunlight-assisted synthesis of colloidal silver nanoparticles using chitosan as reducing agent

NASA Astrophysics Data System (ADS)

Susilowati, E.; Maryani; Ashadi

2018-04-01

The present study we explore an environmentally friendly colloidal silver nanoparticles preparation using chitosan as reducing agent and stabilizer. It develops a new strategy on preparation of silver nanoparticles through the gel phase using sodium hydroxide (NaOH) as accelerator reagent. Sunlight irradiation was employed to assisted reducing process of silver ions to silver nanoparticles. Localized surface plasmon resonance (LSPR) phenomenon of silver nanoparticles was investigated using UV-Vis spectrophotometer. The shape and size of silver particles were analyzed using TEM. The formation of silver nanoparticles was confirmed by the appearance of LSPR absorption peak at 396.0–412.0 nm. The absorption peak of LSPR were affected by NaOH amount, time of sulight irradiation and concentration of AgNO3. The produced silver nanoparticles were spherical with dominant size range of 5 to 8 nm as shown by TEM images. All colloidals were stable without any aggregation for 30 days after preparation.

Sintered silver joints via controlled topography of electronic packaging subcomponents

DOEpatents

Wereszczak, Andrew A.

2014-09-02

Disclosed are sintered silver bonded electronic package subcomponents and methods for making the same. Embodiments of the sintered silver bonded EPSs include topography modification of one or more metal surfaces of semiconductor devices bonded together by the sintered silver joint. The sintered silver bonded EPSs include a first semiconductor device having a first metal surface, the first metal surface having a modified topography that has been chemically etched, grit blasted, uniaxial ground and/or grid sliced connected to a second semiconductor device which may also include a first metal surface with a modified topography, a silver plating layer on the first metal surface of the first semiconductor device and a silver plating layer on the first metal surface of the second semiconductor device and a sintered silver joint between the silver plating layers of the first and second semiconductor devices which bonds the first semiconductor device to the second semiconductor device.

Ink composition for making a conductive silver structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, Steven B.; Lewis, Jennifer A.

An ink composition for making a conductive silver structure comprises a silver salt and a complex of (a) a complexing agent and a short chain carboxylic acid or (b) a complexing agent and a salt of a short chain carboxylic acid, according to one embodiment. A method for making a silver structure entails combining a silver salt and a complexing agent, and then adding a short chain carboxylic acid or a salt of the short chain carboxylic acid to the combined silver salt and a complexing agent to form an ink composition. A concentration of the complexing agent in themore » ink composition is reduced to form a concentrated formulation, and the silver salt is reduced to form a conductive silver structure, where the concentrated formulation and the conductive silver structure are formed at a temperature of about 120.degree. C. or less.« less

Green synthesis of silver nanoparticle and silver based chitosan bionanocomposite using stem extract of Saccharum officinarum and assessment of its antibacterial activity

NASA Astrophysics Data System (ADS)

Paulkumar, Kanniah; Gnanajobitha, Gnanadhas; Vanaja, Mahendran; Pavunraj, Manickam; Annadurai, Gurusamy

2017-09-01

Synthesis of nanoparticles and nanocomposites using green route is a major focus of modern nanotechnology. Herein we demonstrate the synthesis of silver nanoparticle and silver based chitosan bionanocomposite using the stem extract of Saccharum officinarum. The absorbance peak at 460 nm in the UV-Vis spectrum reveals the synthesis of silver nanoparticles using the stem extract of Saccharum officinarum. The size of the synthesized silver nanoparticle was in the range of 10-60 nm obtained from transmission electron microscope (TEM) analysis. The presence of silver nanoparticles on the chitosan suspension was identified by scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDS). The presence of possible functional group involved in the reduction of silver metal ions into silver nanoparticles was identified by Fourier transform infrared spectroscopy (FTIR) analysis. The antibacterial activity of the synthesized silver based chitosan bionanocomposite was evaluated against Bacillus subtilis (MTCC 3053), Klebsiella planticola (MTCC 2277), Streptococcus faecalis (ATCC 8043), Pseudomonas aeruginosa (ATCC 9027) and Escherichia coli (ATCC 8739). The antibacterial activity of silver based chitosan bionanocomposite has remarkable scope in medicine, food packaging, textile and pharmaceuticals.

Silver Film Surface Modification by Ion Bombardment Decreases Surface Plasmon Resonance Absorption.

PubMed

Fryauf, David M; Diaz Leon, Juan J; Phillips, Andrew C; Kobayashi, Nobuhiko P

2017-05-10

Silver thin films covered with dielectric films serving as protective coatings are desired for telescope mirrors, but durable coatings have proved elusive. As part of an effort to develop long-lived protected-silver mirrors, silver thin films were deposited by electron beam evaporation using a physical vapor deposition system at the University of California Observatories Astronomical Coatings Lab. The silver films were later covered with a stack of dielectric films utilizing silicon nitride and titanium dioxide deposited by ion-assisted electron beam evaporation to fabricate protected mirrors. In-situ argon ion bombardment was introduced after silver deposition and prior to the deposition of dielectric films to assess its effects on the performance of the mirrors. We found that ion bombardment of the silver influenced surface morphology and reflectivity, and these effects correlated with time between silver deposition and ion bombardment. The overall reflectivity at wavelengths in the range of 350-800 nm was found to improve due to ion bombardment, which was qualitatively interpreted as a result of decreased surface plasmon resonance coupling. We suggest that the observed decrease in coupling is caused by silver grain boundary pinning due to ion bombardment suppressing silver surface diffusion, forming smoother silver-dielectric interfaces.

Comparison on Bactericidal and Cytotoxic Effect of Silver Nanoparticles Synthesized by Different Methods

NASA Astrophysics Data System (ADS)

Mala, R.; Celsia, A. S. Ruby; Malathi Devi, S.; Geerthika, S.

2017-08-01

Biologically synthesized silver nanoparticle are biocompatible for medical applications. The present work is aimed to synthesize silver nanoparticle using the fruit pulp of Tamarindusindica and to evaluate its antibacterial and anticancer activity against lung cancercell lines. Antibacterial activity was assessed by well diffusion method. Cytotoxicity was evaluated using MTT assay. GC-MS of fruit pulp extract showed the presence of levoglucosenone, n-hexadecanoic acid, 9,12-octadecadienoic acid etc. Antioxidant activity of the fruit pulp was determined by DPPH assay, hydrogen peroxide scavenging assay and lipid peroxidation. The size of biologically synthesized silver nanoparticle varied from 50 nm to 76 nm. It was 59 nm to 98 nm for chemically synthesized silver nanoparticle. Biologically synthesized silver nanoparticle showed 26 mm inhibition zone against E. coli and chemically synthesized silver nanoparticle showed 20 mm. Antioxidant activity of fruit extract by DPPH showed 84 % reduction. The IC 50 of biologically synthesized silver nanoparticle against lung cancer cell lines was 48 µg/ml. It was 95 µg/ml for chemically synthesized silver nanoparticle. The increased activity of biologically synthesized silver nanoparticle was due to its smaller size, stability and the bioactive compounds capping the silver nanoparticle extracted from the fruit extract.

Selective recovery of silver from waste low-temperature co-fired ceramic and valorization through silver nanoparticle synthesis.

PubMed

Swain, Basudev; Shin, Dongyoon; Joo, So Yeong; Ahn, Nak Kyoon; Lee, Chan Gi; Yoon, Jin-Ho

2017-11-01

Considering the value of silver metal and silver nanoparticles, the waste generated during manufacturing of low temperature co-fired ceramic (LTCC) were recycled through the simple yet cost effective process by chemical-metallurgy. Followed by leaching optimization, silver was selectively recovered through precipitation. The precipitated silver chloride was valorized though silver nanoparticle synthesis by a simple one-pot greener synthesis route. Through leaching-precipitation optimization, quantitative selective recovery of silver chloride was achieved, followed by homogeneous pure silver nanoparticle about 100nm size were synthesized. The reported recycling process is a simple process, versatile, easy to implement, requires minimum facilities and no specialty chemicals, through which semiconductor manufacturing industry can treat the waste generated during manufacturing of LTCC and reutilize the valorized silver nanoparticles in manufacturing in a close loop process. Our reported process can address issues like; (i) waste disposal, as well as value-added silver recovery, (ii) brings back the material to production stream and address the circular economy, and (iii) can be part of lower the futuristic carbon economy and cradle-to-cradle technology management, simultaneously. Copyright © 2017 Elsevier Ltd. All rights reserved.

Percutaneous penetration of silver from a silver containing garment in healthy volunteers and patients with atopic dermatitis.

PubMed

Pluut, Olivier A; Bianco, Carlotta; Jakasa, Ivone; Visser, Maaike J; Krystek, Petra; Larese-Filon, Francesca; Rustemeyer, Thomas; Kezic, Sanja

2015-06-01

Human data on dermal absorption of silver under "in use" scenario are scarce which hampers health risk assessment. The main objective of the present study was to determine percutaneous penetration of silver after dermal exposure to silver containing garment in healthy individuals and atopic dermatitis (AD) patients. Next to assess pro-inflammatory effect of silver in the skin. Healthy subjects (n=15) and patients with AD (n=15) wore a sleeve containing 3.6% (w/w) silver on their lower arms for 8h during 5 consecutive days. The percutaneous penetration parameters were deduced from the silver concentration-depth profiles in the stratum corneum (SC) collected by adhesive tapes. Furthermore, silver was measured in urine samples collected before and after exposure. Inflammatory response was assessed by measuring IL-1α and IL-1RA in the exposed and non-exposed skin sites. Dermal flux of silver in healthy subjects and AD patients was respectively 0.23 and 0.20 ng/cm(2)/h. The urine silver concentrations showed no increase after exposure. Furthermore, exposure to silver did not lead to the changes in the profiles of IL-1α and IL-1RA. Dermal absorption of silver under "real life scenario" was lower than the current reference dose. Furthermore, dermal exposure did not lead to altered expression of inflammatory IL-1 cytokines in the skin. Copyright © 2015. Published by Elsevier Ireland Ltd.

Synthesis of water soluble glycine capped silver nanoparticles and their surface selective interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agasti, Nityananda, E-mail: nnagasti@gmail.com; Singh, Vinay K.; Kaushik, N.K.

Highlights: • Synthesis of water soluble silver nanoparticles at ambient reaction conditions. • Glycine as stabilizing agent for silver nanoparticles. • Surface selective interaction of glycine with silver nanoparticles. • Glycine concentration influences crystalinity and optical property of silver nanoparticles. - Abstract: Synthesis of biocompatible metal nanoparticles has been an area of significant interest because of their wide range of applications. In the present study, we have successfully synthesized water soluble silver nanoparticles assisted by small amino acid glycine. The method is primarily based on reduction of AgNO{sub 3} with NaBH{sub 4} in aqueous solution under atmospheric air in themore » presence of glycine. UV–vis spectroscopy, transmission electron microscopy (TEM), X–ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG) and differential thermal analysis (DTA) techniques used for characterization of resulting silver nanoparticles demonstrated that, glycine is an effective capping agent to stabilize silver nanoparticles. Surface selective interaction of glycine on (1 1 1) face of silver nanoparticles has been investigated. The optical property and crystalline behavior of silver nanoparticles were found to be sensitive to concentration of glycine. X–ray diffraction studies ascertained the phase specific interaction of glycine on silver nanoparticles. Silver nanoparticles synthesized were of diameter 60 nm. We thus demonstrated an efficient synthetic method for synthesis of water soluble silver nanoparticles capped by amino acid under mild reaction conditions with excellent reproducibility.« less

Engineered Escherichia coli Silver-Binding Periplasmic Protein That Promotes Silver Tolerance

PubMed Central

Hall Sedlak, Ruth; Hnilova, Marketa; Grosh, Carolynn; Fong, Hanson; Baneyx, Francois; Schwartz, Dan; Sarikaya, Mehmet; Tamerler, Candan

2012-01-01

Silver toxicity is a problem that microorganisms face in medical and environmental settings. Through exposure to silver compounds, some bacteria have adapted to growth in high concentrations of silver ions. Such adapted microbes may be dangerous as pathogens but, alternatively, could be potentially useful in nanomaterial-manufacturing applications. While naturally adapted isolates typically utilize efflux pumps to achieve metal resistance, we have engineered a silver-tolerant Escherichia coli strain by the use of a simple silver-binding peptide motif. A silver-binding peptide, AgBP2, was identified from a combinatorial display library and fused to the C terminus of the E. coli maltose-binding protein (MBP) to yield a silver-binding protein exhibiting nanomolar affinity for the metal. Growth experiments performed in the presence of silver nitrate showed that cells secreting MBP-AgBP2 into the periplasm exhibited silver tolerance in a batch culture, while those expressing a cytoplasmic version of the fusion protein or MBP alone did not. Transmission electron microscopy analysis of silver-tolerant cells revealed the presence of electron-dense silver nanoparticles. This is the first report of a specifically engineered metal-binding peptide exhibiting a strong in vivo phenotype, pointing toward a novel ability to manipulate bacterial interactions with heavy metals by the use of short and simple peptide motifs. Engineered metal-ion-tolerant microorganisms such as this E. coli strain could potentially be used in applications ranging from remediation to interrogation of biomolecule-metal interactions in vivo. PMID:22286990

Development of single cell protectors for sealed silver-zinc cells, phase 1

NASA Technical Reports Server (NTRS)

Imamura, M. S.; Donovan, R. L.; Lear, J. W.; Murray, B.

1976-01-01

A single cell protector (SCP) assembly capable of protecting a single silver-zinc (Ag Zn) battery cell was designed, fabricated, and tested. The SCP provides cell-level protection against overcharge and overdischarge by a bypass circuit. The bypass circuit consists of a magnetic-latching relay that is controlled by the high and low-voltage limit comparators. Although designed specifically for secondary Ag-Zn cells, the SCP is flexible enough to be adapted to other rechargeable cells. Eighteen SCPs were used in life testing of an 18-cell battery. The cells were sealed Ag-Zn system with inorganic separators. For comparison, another 18-cell battery was subjected to identical life test conditions, but with battery-level protection rather than cell-level. An alternative approach to the SCP design in the form of a microprocessor-based system was conceptually designed. The comparison of SCP and microprocessor approaches is also presented and a preferred approach for Ag-Zn battery protection is discussed.

EGFR-specific nanoprobe biodistribution in mouse models

NASA Astrophysics Data System (ADS)

Fashir, Samia A.; Castilho, Maiara L.; Hupman, Michael A.; Lee, Christopher L. D.; Raniero, Leandro J.; Alwayn, Ian; Hewitt, Kevin C.

2015-06-01

Nanotechnology offers a targeted approach to both imaging and treatment of cancer, the leading cause of death worldwide. Previous studies have found nanoparticles with a wide variety of coatings initiate an immune response leading to sequestration in the liver and spleen. In an effort to find a nanoparticle platform which does not elicit an immune response we created 43/44 nm gold or silver nanoparticles coated with biomolecules normally produced by the body, α-lipoic acid and the Epidermal Growth Factor (EGF), and have used mass spectroscopy to determine their biodistribution in mouse models, 24 hours following tail vein injection. Relative to controls, mouse EGF (mEGF) coated silver and gold nanoprobes are found at reduced levels in the liver and spleen. mEGF coated gold nanoprobes on the other hand do not appear to elicit any immune response, as they are found at background levels in these organs. As a result they should remain in circulation for longer and accumulate at high levels in tumors by the enhanced permeability retention (EPR) effect.

Electrochemical deposition of silver crystals aboard Skylab 4

NASA Technical Reports Server (NTRS)

Grodzka, P. G.; Facemire, B. R.; Johnston, M. H.; Gates, D. W.

1976-01-01

Silver crystals were grown aboard Skylab 4 by an electro-chemical reaction and subsequently returned to earth for comparison with crystals grown at 1- and 5-g. Both the Skylab and earth-grown crystals show a variety of structures. Certain tendencies in structure dependency on gravity level, however, can be discerned. In addition, downward growing dendrite streamers; upward growing chunky crystal streamers; growth along an air/liquid interface; and ribbon, film, and fiber crystal habits were observed in experiments conducted on the ground with solutions of varying concentrations. It was also observed that the crystal structures of space and ground electro-deposited silver crystals were very similar to the structures of germanium selenide and germanium telluride crystals grown in space and on the ground by a vapor transport technique. Consideration of the data leads to the conclusions that: (1) the rate of electrochemical displacement of silver ions from a 5 percent aqueous solution by copper is predominantly diffussion controlled in space and kinetically controlled in 1- and higher-g because of augmentation of mass transport by convection; (2) downward and upward crystal streamers are the result of gravity-driven convection, the flow patterns of which can be delineated. Lateral growths along an air/liquid interface are the result of surface-tension-driven convection, the pattern of which also can be delineated; (3) electrolysis in space or low-g environments can produce either dendritic crystals with more perfect microcrystalline structures or massive, single crystals with fewer defects than those grown on ground or at higher g-levels. Ribbons or films of space-grown silicon crystals would find a ready market for electronic substrate and photocell applications. Space-grown dendritic, metal crystals present the possibility of unique catalysts. Large perfect crystals of various materials are desired for a number of electronic and optical applications; and (4) vapor transport growth of germanium selenide and germanium telluride is affected by convection mechanisms similar to the mechanisms hypothesized for the electrochemical deposition of silver crystals. Evidence and considerations leading to the preceding summaries and conclusions are presented. The implications of the findings and conclusions for technological applications are discussed, and recommendations for further experiments are presented.

Density functional theoretical modeling, electrostatic surface potential and surface enhanced Raman spectroscopic studies on biosynthesized silver nanoparticles: observation of 400 PM sensitivity to explosives.

PubMed

Sil, Sanchita; Chaturvedi, Deepika; Krishnappa, Keerthi B; Kumar, Srividya; Asthana, S N; Umapathy, Siva

2014-04-24

Interaction of adsorbate on charged surfaces, orientation of the analyte on the surface, and surface enhancement aspects have been studied. These aspects have been explored in details to explain the surface-enhanced Raman spectroscopic (SERS) spectra of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW or CL-20), a well-known explosive, and 2,4,6-trinitrotoluene (TNT) using one-pot synthesis of silver nanoparticles via biosynthetic route using natural precursor extracts of clove and pepper. The biosynthesized silver nanoparticles (bio Ag Nps) have been characterized using UV-vis spectroscopy, scanning electron microscopy and atomic force microscopy. SERS studies conducted using bio Ag Nps on different water insoluble analytes, such as CL-20 and TNT, lead to SERS signals at concentration levels of 400 pM. The experimental findings have been corroborated with density functional computational results, electrostatic surface potential calculations, Fukui functions and ζ potential measurements.

Antimicrobial polyethyleneimine-silver nanoparticles in a stable colloidal dispersion.

PubMed

Lee, Hyun Ju; Lee, Se Guen; Oh, Eun Jung; Chung, Ho Yun; Han, Sang Ik; Kim, Eun Jung; Seo, Song Yi; Ghim, Han Do; Yeum, Jeong Hyun; Choi, Jin Hyun

2011-11-01

Excellent colloidal stability and antimicrobial activity are important parameters for silver nanoparticles (AgNPs) in a range of biomedical applications. In this study, polyethyleneimine (PEI)-capped silver nanoparticles (PEI-AgNPs) were synthesized in the presence of sodium borohydride (NaBH(4)) and PEI at room temperature. The PEI-AgNPs had a positive zeta potential of approximately +49 mV, and formed a stable nanocolloid against agglomeration due to electrostatic repulsion. The particle size and hydrodynamic cluster size showed significant correlations with the amount of PEI and NaBH(4). PEI-AgNPs and even PEI showed excellent antimicrobial activity against Staphylococus aureus and Klebsiella pneumoniae. The cytotoxic effects of PEI and PEI-AgNPs were confirmed by an evaluation of the cell viability. The results suggest that the amount of PEI should be minimized to the level that maintains the stability of PEI-AgNPs in a colloidal dispersion. Copyright © 2011 Elsevier B.V. All rights reserved.

UV laser deposition of metal films by photogenerated free radicals

NASA Technical Reports Server (NTRS)

Montgomery, R. K.; Mantei, T. D.

1986-01-01

A novel photochemical method for liquid-phase deposition of metal films is described. In the liquid phase deposition scheme, a metal containing compound and a metal-metal bonded carbonyl complex are dissolved together in a polar solvent and the mixture is irradiated using a UV laser. The optical arrangement consists of a HeCd laser which provides 7 mW of power at a wavelength of 325 nm in the TEM(OO) mode. The beam is attenuated and may be expanded to a diameter of 5-20 mm. Experiments with photochemical deposition of silver films onto glass and quartz substrates are described in detail. Mass spectrometric analysis of deposited silver films indicated a deposition rate of about 1 A/s at incident power levels of 0.01 W/sq cm. UV laser-induced copper and palladium films have also been obtained. A black and white photograph showing the silver Van Der Pauw pattern of a solution-deposited film is provided.

A novel management of streptococcal pharyngotonsillar infections by laser-activated silver nanoparticles and methylene blue conjugate, in vitro study.

PubMed

Kassab, Ahmed; Dabous, Ola; Morsy, Mona

2017-09-01

Species of Streptococcus are classified based on their hemolytic properties into alpha and beta types. And, since antimicrobial drug resistance is an increasingly problematic issue, the efforts to develop modalities that would overcome this obstacle and avoid antibiotic side effects is an ongoing challenge. 20 patients from both sexes were selected. The isolated organisms were identified according to standard laboratory methods. Bacterial Cultures were subjected to the low-level diode laser (660 nm), methylene blue (MB) as a photosensitizing agent and for silver nanoparticles. All the experimental groups showed statistically lower values of CFU/ml than the positive control group. The photoactivated MB, silver nanoparticles conjugate showed the maximum inhibitory effect on Streptococci, which opens a gate to further investigation of such a promising protocol to establish a safe and efficient method of management for resistant cases of streptococcal tonsillar infections. Copyright © 2017 Elsevier B.V. All rights reserved.

Polyvinylpyrrolidone- (PVP-) coated silver aggregates for high performance surface-enhanced Raman scattering in living cells.

PubMed

Tan, Xuebin; Wang, Zhuyuan; Yang, Jing; Song, Chunyuan; Zhang, Ruohu; Cui, Yiping

2009-11-04

A biocompatible and stable surface-enhanced Raman scattering (SERS) probe has been successfully synthesized through a simple route with silver aggregates. Polyvinylpyrrolidone (PVP), a biocompatible polymer, was utilized to control the aggregation process and improve the chemical stability of the aggregates. Extinction spectroscopy and TEM results show the aggregation degree and core-shell structure of the probe. It is found that when we employ 4-mercaptobenzoic acid (4MBA), crystal violet (CV), Rhodamine 6G (R6G) or 4,4'-bipyridine molecules as Raman reporters, the SERS signal from the proposed probe can remain at a high level under aggressive chemical environments, even after being incorporated into living cells. In comparison with the traditional probes without the PVP shell, the new ones exhibit strong surface-enhanced effects and low toxicity towards living cells. We demonstrate that the PVP-coated silver aggregates are highly SERS effective, for which the fabrication protocol is advantageous in its simplicity and reproducibility.

Manganese oxides and associated minerals as constituents of dispersed mineralization of metasomatic rocks in the Dukat ore field

NASA Astrophysics Data System (ADS)

Filimonova, L. G.; Sivtsov, A. V.; Trubkin, N. V.

2010-08-01

Lithiophorite and coronadite—varieties of vernadite and todorokite—make up finely dispersed colloform mixtures along with minor grains and nanoparticles of aluminosilicates and ore minerals in metasomatic rocks of the Dukat ore field, which were formed in local areas of fluid and hydrothermal-solution discharge at the upper level of the ore-forming system. Fe-vernadite associates with feroxyhyte, magnetite, apatite, K-feldspar, native silver, and acanthite in greisenized granitoids and with epidote, cerianite, plattnerite, and Fe-chlorite in quartz-garnet-chlorite propylites. Todorokite with high Pb, Tl, and Sn contents associates with epidote, albite, bitumen, and native silver in quartz-epidote-chlorite propylites. Al-vernadite, coronadite, and lithiophorite associate with opal, kaolinite, Fe-chlorite, zincite, uraninite, native silver, and acanthite in argillisites. These data allowed us to estimate the conditions of manganese accumulation in the epithermal ore-forming system and deposition conditions of Mn-rich, finely dispersed mineral mixtures in mineralized zones hosted in metasomatic rocks of the ore field.

Determination of colloidal and dissolved silver in water samples using colorimetric solid-phase extraction.

PubMed

Hill, April A; Lipert, Robert J; Porter, Marc D

2010-03-15

The increase in bacterial resistance to antibiotics has led to resurgence in the use of silver as a biocidal agent in applications ranging from washing machine additives to the drinking water treatment system on the International Space Station (ISS). However, growing concerns about the possible toxicity of colloidal silver to bacteria, aquatic organisms and humans have led to recently issued regulations by the US EPA and FDA regarding the usage of silver. As part of an ongoing project, we have developed a rapid, simple method for determining total silver, both ionic (silver(I)) and colloidal, in 0.1-1mg/L aqueous samples, which spans the ISS potable water target of 0.3-0.5mg/L (total silver) and meets the US EPA limit of 0.1mg/L in drinking water. The method is based on colorimetric solid-phase extraction (C-SPE) and involves the extraction of silver(I) from water samples by passage through a solid-phase membrane impregnated with the colorimetric reagent DMABR (5-[4-(dimethylamino)benzylidene]rhodanine). Silver(I) exhaustively reacts with impregnated DMABR to form a colored compound, which is quantified using a handheld diffuse reflectance spectrophotometer. Total silver is determined by first passing the sample through a cartridge containing Oxone, which exhaustively oxidizes colloidal silver to dissolved silver(I). The method, which takes less than 2 min to complete and requires only approximately 1 mL of sample, has been validated through a series of tests, including a comparison with the ICP-MS analysis of a water sample from ISS that contained both silver(I) and colloidal silver. Potential earth-bound applications are also briefly discussed. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Oxidative stress mediated cytotoxicity of biologically synthesized silver nanoparticles in human lung epithelial adenocarcinoma cell line

NASA Astrophysics Data System (ADS)

Han, Jae Woong; Gurunathan, Sangiliyandi; Jeong, Jae-Kyo; Choi, Yun-Jung; Kwon, Deug-Nam; Park, Jin-Ki; Kim, Jin-Hoi

2014-09-01

The goal of the present study was to investigate the toxicity of biologically prepared small size of silver nanoparticles in human lung epithelial adenocarcinoma cells A549. Herein, we describe a facile method for the synthesis of silver nanoparticles by treating the supernatant from a culture of Escherichia coli with silver nitrate . The formation of silver nanoparticles was characterized using various analytical techniques. The results from UV-visible (UV-vis) spectroscopy and X-ray diffraction analysis show a characteristic strong resonance centered at 420 nm and a single crystalline nature, respectively. Fourier transform infrared spectroscopy confirmed the possible bio-molecules responsible for the reduction of silver from silver nitrate into nanoparticles. The particle size analyzer and transmission electron microscopy results suggest that silver nanoparticles are spherical in shape with an average diameter of 15 nm. The results derived from in vitro studies showed a concentration-dependent decrease in cell viability when A549 cells were exposed to silver nanoparticles. This decrease in cell viability corresponded to increased leakage of lactate dehydrogenase (LDH), increased intracellular reactive oxygen species generation (ROS), and decreased mitochondrial transmembrane potential (MTP). Furthermore, uptake and intracellular localization of silver nanoparticles were observed and were accompanied by accumulation of autophagosomes and autolysosomes in A549 cells. The results indicate that silver nanoparticles play a significant role in apoptosis. Interestingly, biologically synthesized silver nanoparticles showed more potent cytotoxicity at the concentrations tested compared to that shown by chemically synthesized silver nanoparticles. Therefore, our results demonstrated that human lung epithelial A549 cells could provide a valuable model to assess the cytotoxicity of silver nanoparticles.

Evaluation of bactericidal efficacy of silver ions on Escherichia coli for drinking water disinfection.

PubMed

Pathak, Satya P; Gopal, K

2012-07-01

The purpose of this study is the development of a suitable process for the disinfection of drinking water by evaluating bactericidal efficacy of silver ions from silver electrodes. A prototype of a silver ioniser with silver electrodes and control unit has been fabricated. Silver ions from silver electrodes in water samples were estimated with an atomic absorption spectrophotometer. A fresh culture of Escherichia coli (1.75 × 10(3) c.f.u./ml) was exposed to 1, 2, 5, 10 and 20 ppb of silver ions in 100 ml of autoclaved tap water for 60 min. The effect of different pH and temperatures on bactericidal efficacy was observed at constant silver ion concentration (5 ppb) and contact time of 30 min. The maximum bactericidal activity (100%) was observed at 20 ppb of silver ion concentration indicating total disinfection after 20 min while minimum bactericidal activity (25%) was observed after 10 min at 01 ppb of silver ions. Likewise, 100% bactericidal activity was noticed with 2, 5 and 10 ppb of silver ions after 60, 50 and 40 min, respectively. Bactericidal activity at pH 5, 6, 7, 8 and 9 was observed at 79.9%, 79.8%, 80.5%, 100% and 100%, respectively, whereas it was 80.4%, 88.3%, 100%, 100% and 100% at 10°C, 20°C, 30°C, 40°C and 50°C, respectively. The findings of this study revealed that very low concentrations of silver ions at pH 8-9 and temperature >20°C have bactericidal efficacy for total disinfection of drinking water. Silver ionisation is suitable for water disinfection and an appropriate alternative to chlorination which forms carcinogenic disinfection by-products.

Oxidative stress mediated cytotoxicity of biologically synthesized silver nanoparticles in human lung epithelial adenocarcinoma cell line

PubMed Central

2014-01-01

The goal of the present study was to investigate the toxicity of biologically prepared small size of silver nanoparticles in human lung epithelial adenocarcinoma cells A549. Herein, we describe a facile method for the synthesis of silver nanoparticles by treating the supernatant from a culture of Escherichia coli with silver nitrate. The formation of silver nanoparticles was characterized using various analytical techniques. The results from UV-visible (UV-vis) spectroscopy and X-ray diffraction analysis show a characteristic strong resonance centered at 420 nm and a single crystalline nature, respectively. Fourier transform infrared spectroscopy confirmed the possible bio-molecules responsible for the reduction of silver from silver nitrate into nanoparticles. The particle size analyzer and transmission electron microscopy results suggest that silver nanoparticles are spherical in shape with an average diameter of 15 nm. The results derived from in vitro studies showed a concentration-dependent decrease in cell viability when A549 cells were exposed to silver nanoparticles. This decrease in cell viability corresponded to increased leakage of lactate dehydrogenase (LDH), increased intracellular reactive oxygen species generation (ROS), and decreased mitochondrial transmembrane potential (MTP). Furthermore, uptake and intracellular localization of silver nanoparticles were observed and were accompanied by accumulation of autophagosomes and autolysosomes in A549 cells. The results indicate that silver nanoparticles play a significant role in apoptosis. Interestingly, biologically synthesized silver nanoparticles showed more potent cytotoxicity at the concentrations tested compared to that shown by chemically synthesized silver nanoparticles. Therefore, our results demonstrated that human lung epithelial A549 cells could provide a valuable model to assess the cytotoxicity of silver nanoparticles. PMID:25242904

[The comparison of efficacy of female sterilization by modified Uchida technique and silver clips in China].

PubMed

Qiu, Hong-yan; Zou, Yan; Li, Li; Liang, Hong; Zhang, Hong-yan; Wu, Shang-chun

2011-02-01

To compare efficacy of female sterilization by modified Uchida technique and silver clips and to evaluate the influence on operation procedure and clinical effect with or without surgery training of service providers. A comparative, multicenter clinical trial was performed in 18 county and township-level service centers. Totally 2198 women underwent sterilization from these 18 study center were divided into 1116 women sterilized by modified Uchida technique and 1082 women by silver clips. Those 18 centers were classified into 9 training groups which provide surgical skills of sterilization and other contents and 9 non training groups. Clinical documents of sterilization were recorded. All women were follow-up at 3, 6 and 12 months after surgery. There were no complications during surgery by both sterilization. The failure rate was 2.03% (22/1082) in silver clip method and the mean operative time were (12.4 ± 6.4) minutes in training group and (14.4 ± 8.1) minutes in non training group. In modified Uchida method, the failure rate was 0.18% (2/1116) and the mean operative time were (16.2 ± 4.9) minutes in training group and (19.0 ± 8.6) minutes in non training group. The mean operative time between two groups reached statistical difference (all P < 0.05). Total ended rate in modified Uchida technique were 2.2/hundred women year in training group and 2.5/hundred women year in non training group, and the rate of silver slips were 3.9/hundred women year and 4.8/hundred women year, which did not show significant difference (all P > 0.05). There was no significant difference in acceptability and side effects of all women between two methods (P > 0.05). The training of service providers could influence acceptability of women (P < 0.05). Clinical efficacy was not influenced by those two methods. The operative time and acceptability were improved by training surgeons in silver clips method.

Leaching of Silver from Silver-Impregnated Food Storage Containers

ERIC Educational Resources Information Center

Hauri, James F.; Niece, Brian K.

2011-01-01

The use of silver in commercial products has proliferated in recent years owing to its antibacterial properties. Food containers impregnated with micro-sized silver promise long food life, but there is some concern because silver can leach out of the plastic and into the stored food. This laboratory experiment gives students the opportunity to…

Rethinking Schools and the Power of Silver

ERIC Educational Resources Information Center

Sleeter, Christine

2011-01-01

This 25th anniversary of "Rethinking Schools" can be thought of as its silver anniversary. Silver itself must be considered through contrasting lenses. On the one hand, as lessons in "Rethinking Globalization" teach, silver and gold were the basis of Europe's horrendous exploitation of Latin America. On the other hand, silver is often associated…

Biomimetics of silver nanoparticles by white rot fungus, Phaenerochaete chrysosporium.

PubMed

Vigneshwaran, Nadanathangam; Kathe, Arati A; Varadarajan, P V; Nachane, Rajan P; Balasubramanya, R H

2006-11-01

Extracellular synthesis of silver nanoparticles by a white rot fungus, Phaenerochaete chrysosporium is reported in this paper. Incubation of P. chrysosporium mycelium with silver nitrate solution produced silver nanoparticles in 24h. These silver nanoparticles were characterized by means of UV-vis spectroscopy, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy. The synthesized silver nanoparticles absorbed maximum at 470 nm in the visible region. XRD spectrum of the silver nanoparticles confirmed the formation of metallic silver. The SEM characterization of the fungus reacted on the Ag+ indicated that the protein might be responsible for the stabilization of silver nanoparticles. This result was further supported by the TEM examination. Though shape variation was noticed, majority of the nanoparticles were found to be of pyramidal shape as seen under TEM. Photoluminescence spectrum showed a broad emission peak of silver nanoparticles at 423 nm when excited at 350 nm. Apart from eco-friendliness, fungus as bio-manufacturing unit will give us an added advantage in ease of handling when compared to other classes of microorganisms.

Procedure optimization for green synthesis of silver nanoparticles by aqueous extract of Eucalyptus oleosa.

PubMed

Pourmortazavi, Seied Mahdi; Taghdiri, Mehdi; Makari, Vajihe; Rahimi-Nasrabadi, Mehdi

2015-02-05

The present study is dealing with the green synthesis of silver nanoparticles using the aqueous extract of Eucalyptus oleosa as a green synthesis procedure without any catalyst, template or surfactant. Colloidal silver nanoparticles were synthesized by reacting aqueous AgNO3 with E. oleosa leaf extract at non-photomediated conditions. The significance of some synthesis conditions such as: silver nitrate concentration, concentration of the plant extract, time of synthesis reaction and temperature of plant extraction procedure on the particle size of synthesized silver particles was investigated and optimized. The participations of the studied factors in controlling the particle size of reduced silver were quantitatively evaluated via analysis of variance (ANOVA). The results of this investigation showed that silver nanoparticles could be synthesized by tuning significant parameters, while performing the synthesis procedure at optimum conditions leads to form silver nanoparticles with 21nm as averaged size. Ultraviolet-visible spectroscopy was used to monitor the development of silver nanoparticles formation. Meanwhile, produced silver nanoparticles were characterized by scanning electron microscopy, energy-dispersive X-ray, and FT-IR techniques. Copyright © 2014 Elsevier B.V. All rights reserved.

Capsaicin-capped silver nanoparticles: its kinetics, characterization and biocompatibility assay

NASA Astrophysics Data System (ADS)

Amruthraj, Nagoth Joseph; Preetam Raj, John Poonga; Lebel, Antoine

2015-04-01

Capsaicin was used as a bio-reductant for the reduction of silver nitrate to form silver nanoparticles. The formation of the silver nanoparticles was initially confirmed by color change and Tyndall effect of light scattering. It was characterized with UV-visible spectroscopy, FTIR and TEM. Hemagglutination (H) test and H-inhibition assay were performed in the presence of AgNPs-capsaicin conjugates. The silver colloid solution after complete reduction turned into pale gray color. The characteristic surface plasmon resonance of silver nanoparticles (SNPs) was observed at 450 nm. Time taken for complete bio-reduction of silver nitrate and capping was found to be 16 hours. The amount of capsaicin required to reduce 20 ml of 1 mM silver nitrate solution was found to be 40 μg approximately. The FTIR results confirmed the capping of capsaicin on the silver metal. The particle size was within the range of 20-30 nm. The hemagglutination and H-inhibition test was negative for all the blood groups. The capsaicin-capped silver nanoparticles were compatible with blood cells in hemagglutination test implying biocompatibility as future therapeutic drug.

The antifungal effect of silver nanoparticles on Trichosporon asahii.

PubMed

Xia, Zhi-Kuan; Ma, Qiu-Hua; Li, Shu-Yi; Zhang, De-Quan; Cong, Lin; Tian, Yan-Li; Yang, Rong-Ya

2016-04-01

Silver nanoparticles are receiving increasing attention in biomedical applications. This study aims at evaluating the antifungal properties of silver nanoparticles against the pathogenic fungus Trichosporon asahii. The growth of T. asahii on potato dextrose agar medium containing different concentrations of silver nanoparticles was examined and the antifungal effect was evaluated using minimum inhibitory concentration. Scanning and transmission electron microscopy were also used to investigate the antifungal effect of silver nanoparticles on T. asahii. Silver nanoparticles had a significant inhibitory effect on the growth of T. asahii. The minimum inhibitory concentration of silver nanoparticles against T. asahii was 0.5 μg/mL, which was lower than amphotericin B, 5-flucytosine, caspofungin, terbinafine, fluconazole, and itraconazole and higher than voriconazole. Silver nanoparticles obviously damaged the cell wall, cell membrane, mitochondria, chromatin, and ribosome. Our results demonstrate that silver nanoparticles have good antifungal activity against T. asahii. Based on our electron microscopy observations, silver nanoparticles may inhibit the growth of T. asahii by permeating the fungal cell and damaging the cell wall and cellular components. Copyright © 2014. Published by Elsevier B.V.

An analysis of LDEF-exposed silvered FEP teflon thermal blanket material

NASA Technical Reports Server (NTRS)

Young, Philip R.; Slemp, Wayne S.

1991-01-01

The characterization of selected silvered fluorinated ethylene propylene (FEP) teflon thermal blanket material which received 5 years and 9 months of exposure to the LEO environment on the Long Duration Exposure Facility is reported. X-ray photoelectron spectroscopy, infrared, and thermal analyses did not detect a significant change at the molecular level as the result of this exposure. However, various microscopic analyses revealed a roughening of the coating surface due to atomic oxygen erosion which resulted in some materials changing from specular reflectors of visible radiation to diffuse reflectors. The potential effect of silicon-containing molecular contamination on these materials is addressed.

Synthesis and characterization of monodispersed silver nanoparticles

NASA Astrophysics Data System (ADS)

Jegatha Christy, A.; Umadevi, M.

2012-09-01

Synthesis of silver nanoparticles (NPs) has become a fascinating and important field of applied chemical research. In this paper silver NPs were prepared using silver nitrate (AgNO3), gelatin, and cetyl trimethyl ammonium bromide (CTAB). The prepared silver NPs were exposed under the laser ablation. In our photochemical procedure, gelatin acts as a biopolymer and CTAB acts as a reducing agent. The appearance of surface plasmon band around 410 nm indicates the formation of silver NPs. The nature of the prepared silver NPs in the face-centered cubic (fcc) structure are confirmed by the peaks in the x-ray diffraction (XRD) pattern corresponding to (111), (200), (220) and (311) planes. Monodispersed, stable, spherical silver NPs with diameter about 10 nm were obtained and confirmed by high-resolution transmission electron microscope (HRTEM).

Synthesis of Silver Polymer Nanocomposites and Their Antibacterial Activity

NASA Astrophysics Data System (ADS)

Gavade, Chaitali; Shah, Sunil; Singh, N. L.

2011-07-01

PVA (Polyvinyl Alcohol) silver nanocomposites of different sizes were prepared by chemical reduction method. Silver nitrate was taken as the metal precursor and amine hydrazine as a reducing agent. The formation of the silver nanoparticles was noticed using UV- visible absorption spectroscopy. The UV-visible spectroscopy revealed the formation of silver nanoparticles by exhibiting the surface plasmon resonance. The bactericidal activity due to silver release from the surface was determined by the modification of conventional diffusion method. Salmonella typhimurium, Serratia sps and Shigella sps were used as test bacteria which are gram-negative type bacteria. Effect of the different sizes of silver nano particles on antibacterial efficiency was discussed. Zones of inhibition were measured after 24 hours of incubation at 37 °C which gave 20 mm radius for high concentration of silver nanoparticles.

Characterization of silver nanoparticles synthesized using an endophytic fungus, Penicillium oxalicum having potential antimicrobial activity

NASA Astrophysics Data System (ADS)

Bhattacharjee, Sukla; Debnath, Gopal; Das, Aparajita Roy; Krishna Saha, Ajay; Das, Panna

2017-12-01

The aim of the present study was to test the efficacy of the extracellular mycelium extract of Penicillium oxalicum isolated from Phlogacanthus thyrsiflorus to biosynthesize silver nanoparticles. It was characterized using ultraviolet-visible absorption spectroscopy, atomic force microscopy, transmission electron microscopy and Fourier transforms infrared spectroscopy. The silver nanoparticles were evaluated for antimicrobial activity. The characterization confirms the synthesis of silver nanoparticles. Both silver nanoparticles and combination of silver nanoparticles with streptomycin showed activity against the four bacteria. The results suggested that P. oxalicum offers eco-friendly production of silver nanoparticles and the antibacterial activity may find application in biomedicine.

Determination of traces of silver in waters by anion exchange and atomic absorption spectrophotometry

USGS Publications Warehouse

Chao, T.T.; Fishman, M. J.; Ball, J.W.

1969-01-01

A method has been developed for the accurate determination of 0.1-1 ??g of silver per liter of water. The method permits stabilization of silver in water without loss to container walls. Optimum conditions have been established for the complete recovery of silver from water with an anion-exchange column, for quantitative elution of silver from the resin, and for measurement of silver by atomic absorption spectrophotometry after chelation with ammonium pyrrolidine dithiocarbamate and extraction of the chelate with MIBK. Silver in the 1-10 ??g 1 range can be determined by extraction without pre-concentration on an ion-exchange resin. ?? 1969.

Mineral commodity profiles: Silver

USGS Publications Warehouse

Butterman, W.C.; Hilliard, Henry E.

2005-01-01

Overview -- Silver is one of the eight precious, or noble, metals; the others are gold and the six platinum-group metals (PGM). World mine production in 2001 was 18,700 metric tons (t) and came from mines in 60 countries; the 10 leading producing countries accounted for 86 percent of the total. The largest producer was Mexico, followed by Peru, Australia, and the United States. About 25 percent of the silver mined in the world in 2001 came from silver ores; 15 percent, from gold ores and the remaining 60 percent, from copper, lead, and zinc ores. In the United States, 14 percent of the silver mined in 2001 came from silver ores; 39 percent, from gold ores; 10 percent, from copper and copper-molybdenum ores; and 37 percent, from lead, zinc, and lead-zinc ores. The precious metal ores (gold and silver) came from 30 lode mines and 10 placer mines; the base-metal ores (copper, lead, molybdenum, and zinc) came from 24 lode mines. Placer mines yielded less than 1 percent of the national silver production. Silver was mined in 12 States, of which Nevada was by far the largest producer; it accounted for nearly one-third of the national total. The production of silver at domestic mines generated employment for about 1,100 mine and mill workers. The value of mined domestic silver was estimated to be $290 million. Of the nearly 27,000 t of world silver that was fabricated in 2001, about one-third went into jewelry and silverware, one-fourth into the light-sensitive compounds used in photography, and nearly all the remainder went for industrial uses, of which there were 7 substantial uses and many other small-volume uses. By comparison, 85 percent of the silver used in the United States went to photography and industrial uses, 8 percent to jewelry and silverware, and 7 percent to coins and medals. The United States was the largest consumer of silver followed by India, Japan, and Italy; the 13 largest consuming countries accounted for nearly 90 percent of the world total. In the United States, about 30 companies accounted for more than 90 percent of the silver fabricated. The consumption of silver for all fabrication uses is expected to grow slowly through the decade ending in 2010 at about 1.3 percent per year for the world and 2.4 percent per year for the United States. World and U.S. reserves and reserve bases are more than adequate to satisfy the demand for newly mined silver through 2010. The other components of supply will be silver recovered from scrap, silver from industrial stocks, and silver bullion that is sold into the market from commodity exchange and private stocks.

Effect of preconditioning on silver leaching and bromide removal properties of silver-impregnated activated carbon (SIAC).

PubMed

Rajaeian, Babak; Allard, Sébastien; Joll, Cynthia; Heitz, Anna

2018-07-01

Silver impregnated activated carbon (SIAC) has been found to be effective in mitigating the formation of brominated-disinfection by products during drinking water treatment. However, there are still uncertainties regarding its silver leaching properties, and strategies for the prevention of silver leaching have remained elusive. This study focused on the evaluation of one type of commercially available SIAC for its ability to remove bromide while minimising silver leaching from the material. Both synthetic and real water matrices were tested. Depending on solution pH, it was found that changing the surface charge properties of SIAC, as measured by the point of zero charge pH, can result in additional bromide removal while minimising the extent of silver leaching. To better understand the mechanism of silver leaching from the SIAC, eight preconditioning environments, i.e. variable pH and ionic strength were tested for a fixed amount of SIAC and two preconditioning environments were selected for a more detailed investigation. Experiments carried out in synthetic water showed that preconditioning at pH 10.4 did not deteriorate the capacity of SIAC to remove bromide, but significantly decreased the release of silver in the form of ionic silver (Ag + ), silver bromide (AgBr) and silver chloride (AgCl) from 40% for the pristine to 3% for the treated SIAC. This was confirmed using a groundwater sample. These results suggest that preconditioned SIAC has the potential to be an effective method for bromide removal with minimised silver leaching in a long-term field application for drinking water production. Copyright © 2018 Elsevier Ltd. All rights reserved.

A re-assessment of the safety of silver in household water treatment: rapid systematic review of mammalian in vivo genotoxicity studies.

PubMed

Fewtrell, Lorna; Majuru, Batsirai; Hunter, Paul R

2017-06-20

Despite poor evidence of their effectiveness, colloidal silver and silver nanoparticles are increasingly being promoted for treating potentially contaminated drinking water in low income countries. Recently, however, concerns have been raised about the possible genotoxicity of particulate silver. The goal of this paper was to review the published mammalian in vivo genotoxicity studies using silver micro and nanoparticles. SCOPUS and Medline were searched using the following search string: ("DNA damage" OR genotox* OR Cytotox* OR Embryotox*) AND (silver OR AgNP). Included papers were any mammalian in vivo experimental studies investigating genotoxicity of silver particles. Studies were quality assessed using the ToxRTool. 16 relevant papers were identified. There were substantial variations in study design including the size of silver particles, animal species, target organs, silver dose, route of administration and the method used to detect genotoxicity. Thus, it was not possible to produce a definitive pooled result. Nevertheless, most studies showed evidence of genotoxicity unless using very low doses. We also identified one human study reporting evidence of "severe DNA damage" in silver jewellery workers occupationally exposed to silver particles. With the available evidence it is not possible to be definitive about risks to human health from oral exposure to silver particulates. However, the balance of evidence suggests that there should be concerns especially when considering the evidence from jewellery workers. There is an urgent need to determine whether people exposed to particulate silver as part of drinking water treatment have evidence of DNA damage.

Development of the rectal dosage form with silver-coated glass beads for local-action applications in lower sections of the gastrointestinal tract.

PubMed

Siczek, Krzysztof; Fichna, Jakub; Zatorski, Hubert; Karolewicz, Bożena; Klimek, Leszek; Owczarek, Artur

2018-03-01

Recent findings indicating the anti-inflammatory action of silver preparations through modulation of the gut microbiota and apoptosis of inflammatory cells predestine silver use in inflammatory bowel disease (IBD). The aim of our study was to validate the possibility of effective silver release from silver-coated glass beads for anti-inflammatory local application in the lower sections of the gastrointestinal (GI) tract. Silver-coated glass beads were prepared using magnetron method. Release of silver from the silver-coated glass bead surface was carried out in BIO-DIS reciprocating cylinder apparatus. Erosion of silver coating and indirect estimation of the silver release dynamics was assessed using scanning electron microscope. Rectal suppositories containing silver-coated glass beads were prepared using five different methods (M1-M5) and X-ray scanned for their composition. The XR microanalysis and the chemical composition analysis evidenced for a rapid (within 30 min) release of nearly 50% of silver from the coating of the glass beads, which remained stable up to 24 h of incubation. The most homogeneous distribution of beads in the entire volume of the suppository was obtained for formulation M5, where the molten base was poured into mold placed in an ice bath, and the beads were added after 10 s. Our study is the first to present the concept of enclosing silver-coated glass beads in the lipophilic suppository base to attenuate inflammation in the lower GI tract and promises efficient treatment with reduced side effects.

Evolution of silver nanoparticles in the rat lung investigated by X-ray absorption spectroscopy

DOE PAGES

Davidson, R. Andrew; Anderson, Donald S.; Van Winkle, Laura S.; ...

2014-12-16

Following a 6-h inhalation exposure to aerosolized 20 and 110 nm diameter silver nanoparticles, lung tissues from rats were investigated with X-ray absorption spectroscopy, which can identify the chemical state of silver species. Lung tissues were processed immediately after sacrifice of the animals at 0, 1, 3, and 7 days post exposure and the samples were stored in an inert and low-temperature environment until measured. We found that it is critical to follow a proper processing, storage and measurement protocol; otherwise only silver oxides are detected after inhalation even for the larger nanoparticles. The results of X-ray absorption spectroscopy measurementsmore » taken in air at 85 K suggest that the dominating silver species in all the postexposure lung tissues were metallic silver, not silver oxide, or solvated silver cations. The results further indicate that the silver nanoparticles in the tissues were transformed from the original nanoparticles to other forms of metallic silver nanomaterials and the rate of this transformation depended on the size of the original nanoparticles. Furthermore, we found that 20 nm diameter silver nanoparticles were significantly modified after aerosolization and 6-h inhalation/deposition, whereas larger, 110 nm diameter nanoparticles were largely unchanged. Over the seven-day postexposure period the smaller 20 nm silver nanoparticles underwent less change in the lung tissue than the larger 110 nm silver nanoparticles. In contrast, silica-coated gold nanoparticles did not undergo any modification processes and remained as the initial nanoparticles throughout the 7-day study period.« less

Evolution of silver nanoparticles in the rat lung investigated by X-ray absorption spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davidson, R. Andrew; Anderson, Donald S.; Van Winkle, Laura S.

Following a 6-h inhalation exposure to aerosolized 20 and 110 nm diameter silver nanoparticles, lung tissues from rats were investigated with X-ray absorption spectroscopy, which can identify the chemical state of silver species. Lung tissues were processed immediately after sacrifice of the animals at 0, 1, 3, and 7 days post exposure and the samples were stored in an inert and low-temperature environment until measured. We found that it is critical to follow a proper processing, storage and measurement protocol; otherwise only silver oxides are detected after inhalation even for the larger nanoparticles. The results of X-ray absorption spectroscopy measurementsmore » taken in air at 85 K suggest that the dominating silver species in all the postexposure lung tissues were metallic silver, not silver oxide, or solvated silver cations. The results further indicate that the silver nanoparticles in the tissues were transformed from the original nanoparticles to other forms of metallic silver nanomaterials and the rate of this transformation depended on the size of the original nanoparticles. Furthermore, we found that 20 nm diameter silver nanoparticles were significantly modified after aerosolization and 6-h inhalation/deposition, whereas larger, 110 nm diameter nanoparticles were largely unchanged. Over the seven-day postexposure period the smaller 20 nm silver nanoparticles underwent less change in the lung tissue than the larger 110 nm silver nanoparticles. In contrast, silica-coated gold nanoparticles did not undergo any modification processes and remained as the initial nanoparticles throughout the 7-day study period.« less

In vitro percutaneous penetration and characterization of silver from silver-containing textiles

PubMed Central

Bianco, Carlotta; Kezic, Sanja; Crosera, Matteo; Svetličić, Vesna; Šegota, Suzana; Maina, Giovanni; Romano, Canzio; Larese, Francesca; Adami, Gianpiero

2015-01-01

The objective of this study was to determine the in vitro percutaneous penetration of silver and characterize the silver species released from textiles in different layers of full thickness human skin. For this purpose, two different wound dressings and a garment soaked in artificial sweat were placed in the donor compartments of Franz cells for 24 hours. The concentration of silver in the donor phase and in the skin was determined by an electrothermal atomic absorption spectrometer (ET-AAS) and by inductively coupled plasma mass spectrometer (ICP-MS). The characterization of silver species in the textiles and in the skin layers was made by scanning electron microscopy with integrated energy dispersive X-ray spectroscopy (SEM-EDX). Additionally, the size distribution of silver nanoparticles in the textiles was performed by atomic force microscopy (AFM). On the surface of all investigated materials, silver nanoparticles of different size and morphology were found. Released silver concentrations in the soaking solutions (ie, exposure concentration) ranged from 0.7 to 4.7 μg/mL (0.6–4.0 μg/cm2), fitting the bactericidal range. Silver and silver chloride aggregates at sizes of up to 1 μm were identified both in the epidermis and dermis. The large size of these particles suggests that the aggregation occurred in the skin. The formation of these aggregates likely slowed down the systemic absorption of silver. Conversely, these aggregates may form a reservoir enabling prolonged release of silver ions, which might lead to local effects. PMID:25792824

Effect of silver nanoparticles on concentration of silver heavy element and growth indexes in cucumber ( Cucumis sativus L . negeen)

NASA Astrophysics Data System (ADS)

Shams, Gholamabbas; Ranjbar, Morteza; Amiri, Aliasghar

2013-05-01

The tremendous progress on nanoparticle research area has been made significant effects on the economy, society, and the environment. Silver nanoparticle is one of the most important particles in these categories. Silver nanoparticles can be converted to the heavy silver metal in water by oxidation. Moreover, in the high amounts of silver concentration, they will be accumulated in different parts of the plant. However, by changing the morphology of the plant, the production will be harmful for human consumptions. In this study, nano-powders with average 50 nm silver particles are mixed with deionized distilled water in a completely randomized design. Seven treatments with various concentrations of suspension silver nanoparticles were prepared and repeated in four different parts of the plant in a regular program of spraying. Samples were analyzed to study the growth indexes and concentration of silver in different parts of the plant. It was observed that with increasing concentration of silver nanoparticles on cucumber, the growth indexes (except pH fruit), and the concentration of silver heavy metal are increased significantly. The incremental concentration had the linear relationship with correlation coefficient 0.95 and an average of 0.617 PPM by increasing of each unit in one thousand concentration of nanosilver. Although, by increasing concentration of silver nanoparticles as spraying form, the plant morphological characteristics were improved, the concentration of silver heavy metal in various plant organs was increased. These results open a new pathway to consider the effect of nanoparticles on plant's productions for human consumptions.

Trace elements in early phase type 2 diabetes mellitus-A population-based study. The HUNT study in Norway.

PubMed

Hansen, Ailin Falkmo; Simić, Anica; Åsvold, Bjørn Olav; Romundstad, Pål Richard; Midthjell, Kristian; Syversen, Tore; Flaten, Trond Peder

2017-03-01

Differences in trace elements levels between individuals with type 2 diabetes and controls have been reported in several studies in various body fluids and tissues, but results have been inconsistent. In order to examine trace element levels in the early phase of type 2 diabetes, we investigated the association between whole blood levels of 26 trace elements and the prevalence of previously undiagnosed, screening-detected type 2 diabetes. The study was conducted as a case-control study nested within the third survey of the population-based Nord-Trøndelag Health Study (HUNT3 Survey). Among participants without previously known diabetes, 128 cases of type 2 diabetes were diagnosed in people with a high diabetes risk score (FINDRISC≥15), and frequency-matched for age and sex with 755 controls. Blood samples were analyzed by high resolution inductively coupled plasma mass spectrometry. Associations between trace element levels and the prevalence of previously undiagnosed type 2 diabetes were evaluated with multivariable conditional logistic regression controlling for age, sex, body mass index, waist-to-hip ratio, education, income, smoking and family history of diabetes. The prevalence of previously undiagnosed type 2 diabetes increased across tertiles/quartiles for cadmium, chromium, iron, nickel, silver and zinc, and decreased with increasing quartiles of bromine (P trend <0.05). After corrections for multiple testing, associations for chromium remained significant (Q trend <0.05), while associations for iron and silver were borderline significant. No associations were found for arsenic, boron, calcium, cesium, copper, gallium, gold, indium, lead, magnesium, manganese, mercury, molybdenum, rubidium, selenium, strontium, tantalum, thallium and tin. Our results suggest a possible role of bromine, cadmium, chromium, iron, nickel, silver and zinc in the development of type 2 diabetes. Copyright © 2016 Elsevier GmbH. All rights reserved.

Silver Clusters in Zeolites: From Self-Assembly to Ground-Breaking Luminescent Properties.

PubMed

Coutiño-Gonzalez, Eduardo; Baekelant, Wouter; Steele, Julian A; Kim, Cheol Woong; Roeffaers, Maarten B J; Hofkens, Johan

2017-09-19

Interest for functional silver clusters (Ag-CLs) has rapidly grown over years due to large advances in the field of nanoscale fabrication and materials science. The continuous development of strategies to fabricate small-scale silver clusters, together with their interesting physicochemical properties (molecule-like discrete energy levels, for example), make them very attractive for a wide variety of applied research fields, from biotechnology and the environmental sciences to fundamental chemistry and physics. Apart from useful catalytic properties, silver clusters (Ag n , n < 10) were recently shown to also exhibit exceptional optical properties. The optical properties and performance of Ag-CLs offer strong potential for their integration into appealing micro(nano)-optoelectronic devices. To date, however, the rational design and directed synthesis of Ag-CLs with specific functionalities has remained elusive. The inability for rational design stems mainly from a lack of understanding of their novel atomic-scale phenomena. This is because accurately studying silver cluster systems at such a scale is hindered by the perturbations introduced during exposure to various experimental probes. For instance, silver possesses a strong tendency to cluster and form ever-larger Ag aggregates while probed with high-energy electron beams and X-ray irradiation. As well, there exists a need to provide a stabilizing environment for which Ag n δ+ clusters can persist, setting up a complex interacting guest-host system, as isolated silver clusters are confined within a suitable hosting medium. Fundamental research into Ag n δ+ formation mechanisms and their important optical properties is paramount to establishing truly informed synthesis protocols. Over recent years, we have developed several protocols for the ship-in-a-bottle synthesis of highly luminescent Ag-CLs within the microporous interiors of zeolite frameworks. This approach has yielded materials displaying a wide variety of optical properties, offering a spectrum of possible applications, from nano(micro)photonic devices to smart luminescent labels and sensors. The versatility of the Ag-zeolite multicomponent system is directly related to the intrinsic and complex tunability of the system as a whole. There are several key zeolite parameters that confer properties to the clusters, namely, the framework Si/Al ratio, choice of counterbalancing ions, silver loading, and zeolite topology, and cannot be overlooked. This Account is intended to shed light on the current state-of-the-art of luminescent Ag-CLs confined in zeolitic matrices, emphasizing the use of combinatorial approaches to overcome problems associated with the correct characterization and correlation of their structural, electronic, and photoluminescence properties, all to establish the important design principles for developing functional silver-zeolite-based materials. Additionally, examples of emerging applications and future perspectives for functional luminescent Ag-zeolite materials are addressed in this Account.

Reduction of silver (I) using defatted cashew nut shell starch and its structural comparison with commercial product.

PubMed

Velmurugan, Palanivel; Park, Jung-Hee; Lee, Sang-Myeong; Jang, Jum-Suk; Yi, Young-Joo; Han, Sang-Sub; Lee, Sang-Hyun; Cho, Kwang-Min; Cho, Min; Oh, Byung-Taek

2015-11-20

In this current study, we report on the reduction of noble metal silver into silver nanoparticles using defatted cashew nut shell (CNS) starch as both the reducing and capping agents. Furthermore, it was compared with commercially available silver nanopowder for the first time. Color changes, ultraviolet-visible spectra (433.76nm), X-ray diffraction peaks (2θ=37.8, 46.3, 66.2, and 77.92) revealed the face-centered cubic (fcc) geometry of silver nanoparticles, scanning electron microscopy-energy dispersive spectroscopy confirmed the presence of elemental silver nanoparticles and the defatted CNS starch silver nanoparticle structures was in accordance to commercial silver nanopowder. The size of both the nanoparticles was found to be similar in the range of 10-50nm as analyzed using high resolution-transmission electron micrographs. The FT-IR spectroscopy revealed the shifting of NH and OH of defatted CNS starch, starch based silver nanoparticle and commercial silver nanopowder has parallel functional groups. The use of environmentally benign and renewable materials like defatted CNS starch offers an alternative to large scale synthesis of silver nanoparticle and includes numerous benefits like eco-friendly and compatibility for pharmaceutical and biomedical applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

Reduction in Wound Bioburden using a Silver-Loaded Dissolvable Microfilm Construct

PubMed Central

Herron, Maggie; Agarwal, Ankit; Kierski, Patricia R.; Calderon, Diego F.; Teixeira, Leandro B. C.; Schurr, Michael J.; Murphy, Christopher J.

2014-01-01

Silver is a widely used antimicrobial agent, yet when impregnated in macroscopic dressings, it stains wounds, can lead to tissue toxicity and can inhibit healing. Recently, we reported that polymeric nanofilms containing silver nanoparticles exhibit antimicrobial activity at loadings and release rates of silver that are 100x lower than conventional dressings. Here we report fabrication of composite microfilm constructs that provide a facile way to transfer the silver-loaded polymeric nanofilms onto wounds in vivo. The construct is fabricated from a silver nanoparticle-loaded polymeric nanofilm that is laminated with a micrometer-thick soluble film of polyvinylalcohol (PVA). When placed on a moist wound, the PVA dissolves, leaving the silver-loaded nanofilm immobilized on the wound-bed. In vitro, the immobilized nanofilms release <1 μg cm−2/day of silver over 30 days from skin-dermis and they kill 5 log10 CFUs of Staphylococcus aureus in 24 h. In mice, wounds inoculated with 105 CFU S. aureus presented up to 3 log10 less bacterial burden when treated with silver/nanofilms for 3 days, as compared to unmodified wounds. In uncontaminated wounds, silver/nanofilms allow normal and complete wound closure by re-epithelialization. We conclude that dissolvable microfilm constructs may overcome key limitations associated with current uses of silver in wound healing. PMID:24523027

Electroless growth of silver nanoparticles into mesostructured silica block copolymer films.

PubMed

Bois, Laurence; Chassagneux, Fernand; Desroches, Cédric; Battie, Yann; Destouches, Nathalie; Gilon, Nicole; Parola, Stéphane; Stéphan, Olivier

2010-06-01

Silver nanoparticles and silver nanowires have been grown inside mesostructured silica films obtained from block copolymers using two successive reduction steps: the first one involves a sodium borohydride reduction or a photoreduction of silver nitrate contained in the film, and the second one consists of a silver deposit on the primary nanoparticles, carried out by silver ion solution reduction with hydroxylamine chloride. We have demonstrated that the F127 block copolymer ((PEO)(106)(PPO)(70)(PEO)(106)), "F type", mesostructured silica film is a suitable "soft" template for the fabrication of spherical silver nanoparticles arrays. Silver spheres grow from 7 to 11 nm upon the second reduction step. As a consequence, a red shift of the surface plasmon resonance associated with metallic silver has been observed and attributed to plasmonic coupling between particles. Using a P123 block copolymer ((PEO)(20)(PPO)(70)(PEO)(20)), "P type", mesostructured silica film, we have obtained silver nanowires with typical dimension of 10 nm x 100 nm. The corresponding surface plasmon resonance is blue-shifted. The hydroxylamine chloride treatment appears to be efficient only when a previous chemical reduction is performed, assuming that the first sodium borohydride reduction induces a high concentration of silver nuclei in the first layer of the porous silica (film/air interface), which explains their reactivity for further growth.

Intravenous Exposure of Pregnant Mice to Silver Nanoparticles: Silver Tissue Distribution and Effects in Maternal and Extra-Embryonic Tissues and Embryos

NASA Astrophysics Data System (ADS)

Austin, Carlye Anne

This research explores the tissue distribution of silver, as well as adverse effects in pregnant mice and embryos, following prenatal silver nanoparticle (AgNP) exposure. Chapter one of this dissertation is a survey of the published literature on the reproductive and/or developmental toxicity of AgNPs. The available data indicate that AgNPs adversely affect sperm count, viability, and/or motility both in vivo and in vitro, and cause apoptosis and necrosis in spermatogonial stem cells and testicular cells. Additionally, AgNP exposure results in mortality and morphological deformities in fish embryos, but produces no adverse effects in chicken embryos. The current published research on in vivo AgNP exposure to mammals during gestation consists of only three studies, one of which is described in chapter two of this dissertation. These studies report results that may suggest a potential for adverse effects on fetal development (e.g. , decreased viability and fetal and placental weights, increased incidence of developmentally young embryos), but additional research is needed. Chapter two of this dissertation investigates the distribution of silver in tissues of pregnant mice and gestation day (GD) 10 embryos following intravenous maternal exposure to 50 nm AgNPs during early organogenesis (GDs 7-9). Examinations of embryo morphology and histology were also performed. Results demonstrated the presence of silver in all organs and tissues examined. Silver concentrations were highest in liver, spleen, and visceral yolk sac, and lowest in embryos. Groups of mice were also treated with soluble silver nitrate, and the pattern of silver tissue distribution following silver nitrate exposure was similar to that which followed AgNP treatment. Transmission electron microscopy-energy dispersive x-ray spectroscopy (TEM-EDS) confirmed the presence of vesicle-bound nanoparticulate silver in visceral yolk sac endoderm, but not mesoderm. This finding, along with the high silver concentration in visceral yolk sac and low silver concentration in embryos, suggests that visceral yolk sac tissue mitigates AgNP transfer to embryos. No significant treatment-related effects on embryo morphology or tissue histology were detected. Chapter three constitutes an expanded study of silver distribution in pregnant mice and developing embryos, with the addition of 10 nm AgNP treatment groups and examination of fetuses at GD16. Very low concentrations of silver were measured in GD10 embryos and GD16 fetuses following 10 nm AgNP treatment or in GD16 fetuses following 50 nm AgNP treatment. Highest silver concentrations were measured in maternal liver, spleen, and visceral yolk sac. AgNP particle size (10 or 50 nm) did not consistently affect silver tissue distribution. At GD10, 50 nm AgNP treatment resulted in significantly higher silver concentrations than 10 nm AgNP treatment for liver, spleen, and visceral yolk sac only; at GD16, in visceral yolk sac only, 10 nm AgNP treatment resulted in a significantly higher silver concentration than 50 nm AgNP treatment. In liver, spleen, visceral yolk sac, and uterus, absolute silver concentrations following 10 nm AgNP treatment were significantly lower at GD16 compared to GD10; the patterns of silver tissue distribution were similar at both time points. Silver nitrate and 10 nm AgNP treatments resulted in similar tissue concentrations in GD10 tissues with the exception of visceral yolk sac, for which the silver concentration was significantly higher after silver nitrate treatment. Silver distribution patterns were generally similar between 10 nm AgNP and silver nitrate treatments. No histological abnormalities were noted in maternal tissues, extra-embryonic tissues, or embryos. A significantly increased incidence of developmentally young (for gestational age) GD10 embryos was seen following 10 nm AgNP treatment; no significant morphological effects were observed in embryos or maternal tissues. Further research will be needed to fully evaluate potential effects of prenatal AgNP exposure on embryos. (Abstract shortened by UMI.)

31 CFR 56.1 - Conditions upon which silver will be sold.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Conditions upon which silver will be sold. 56.1 Section 56.1 Money and Finance: Treasury Regulations Relating to Money and Finance DOMESTIC GOLD AND SILVER OPERATIONS SALE OF SILVER § 56.1 Conditions upon which silver will be sold. The General...

Hepatoprotective effect of engineered silver nanoparticles coated bioactive compounds against diethylnitrosamine induced hepatocarcinogenesis in experimental mice.

PubMed

Prasannaraj, Govindaraj; Venkatachalam, Perumal

2017-02-01

Nanoparticle based drug delivery can rapidly improves the therapeutic potential of anti-cancer agents. The present study focused to evaluate the hepatoprotective activity of silver nanoparticles (AgNPs) synthesized using aqueous extracts of Andrographis paniculata leaves (ApAgNPs) and Semecarpus anacardium nuts (SaAgNPs) against diethylnitrosamine (DEN) induced liver cancer in mice model. The physico-chemical properties of synthesized AgNPs were characterized by Fourier transform infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), X-ray Diffraction (XRD), Energy Dispersive X-ray (EDX) spectrum, Zeta potential and Dynamic Light Scattering (DLS) analysis. The surface plasmon resonance (SPR) absorption spectrum revealed a strong peak at 420nm for both SaAgNPs and ApAgNPs. FTIR results exhibited the presence of possible functional groups in the synthesized AgNPs. TEM analysis determined the hexagonal, and spherical shape of the synthesized silver nanoparticles. The XRD and SAED pattern confirmed the crystalline nature and crystalline size of the AgNPs. EDX result clearly showed strong silver signals in the range between 2 and 4keV. Zeta potential measurements indicated a sharp peak at -3.93 and -13.8mV for ApAgNPs and SaAgNPs, respectively. DLS measurement expressed the particle size distribution was 70 and 60nm for ApAgNPs and SaAgNPs, respectively. DEN (20mg/kg b.wt.) was subjected to induce liver cancer in mice for 8weeks and treated with biosynthesized silver nanoparticles. Interestingly, ApAgNPs and SaAgNPs treated DEN induced animal groups show a decreased level of aspartate amino transferase (AST), alanine amino transferase (ALT), serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT) activity and elevated level of catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST) and superoxide dismutase (SOD) activity over untreated DEN control animals group. Histopathological investigation reveals decreased fat accumulation, appearance of binucleated cells in nanoparticle treated animals and showed mere normal cells induced by DEN. Argyrophilic nucleolar organiser region (AgNORs) had a significant decrease in number of acidic proteins and mast cells assay showed decrease of metachromatic cells in nanoparticles treated animal groups over control. Present results strongly suggest that biomolecule coated silver nanoparticles exposure showed potential hepatoprotective effect against DEN induced liver cancer and could be used as an effective anticancer nanodrug. Copyright © 2017. Published by Elsevier B.V.

Utilization of hydroxypropyl carboxymethyl cellulose in synthesis of silver nanoparticles.

PubMed

Abdel-Halim, E S; Alanazi, Humaid H; Al-Deyab, Salem S

2015-04-01

Hydroxypropyl carboxymethyl cellulose samples having varying degrees of substitution and varying degrees of polymerization were used to reduce silver nitrate to silver nanoparticles. UV spectral analysis of silver nanoparticles colloidal solution reveal that increasing the pH of the reduction solution leads to improvement in the intensity of the absorption band for silver nanoparticles, to be maximum at pH 11. The absorption peak intensity also enhanced upon prolonging the reaction duration up to 60 min. The conversion of silver ions to metallic silver nanoparticles was found to be temperature-dependent and maximum transformation occurs at 60 °C. The reduction efficiency of hydroxypropyl carboxymethyl cellulose was found to be affected by its degree of polymerization. Colloidal solutions of silver nanoparticles having concentration up to 1000 ppm can be prepared upon fixing the ratio between silver nitrate and hydroxypropyl carboxymethyl cellulose at 0.017-0.3g per each 100ml of the reduction solution. Copyright © 2015 Elsevier B.V. All rights reserved.

Facile synthesis and characterization of silver nanoparticle/bis(o-phenolpropyl)silicone composites using a gold catalyst.

PubMed

Roh, Sung-Hee; Cheong, Hyeonsook; Kim, Do-Heyoung; Woo, Hee-Gweon; Lee, Byeong-Gweon; Yang, Kap-Seung; Kim, Bo-Hye; Sohn, Honglae

2013-01-01

The generation of silver nanoparticle/bis(o-phenolpropyl)silicone composites have been facilitated by the addition of sodium tetrachloroaurate or gold(Ill) chloride (< 1 wt% of NaAuCl4 or AuCl3) to the reaction of silver nitrate (AgNO3) with bis(o-phenolpropyl)silicone [BPPS, (o-phenolpropyl)2(SiMe2O)n, n = 2,3,8,236]. TEM and FE-SEM data showed that the silver nanoparticles having the size of < 20 nm are well dispersed throughout the BPPS silicone matrix in the composites. XRD patterns are consistent with those for polycrystalline silver. The size of silver nanoparticles augmented with increasing the relative molar concentration of AgNO3 added with respect to BPPS. The addition of gold complexes (1-3 wt%) did not affect the size distribution of silver nanoparticles appreciably. In the absence of BPPS, the macroscopic precipitation of silver by agglomeration, indicating that BPPS is necessary to stabilize the silver nanoparticles surrounded by coordination.

Electrochemical Study and Applications of Selective Electrodeposition of Silver on Quantum Dots.

PubMed

Martín-Yerga, Daniel; Rama, Estefanía Costa; Costa-García, Agustín

2016-04-05

In this work, selective electrodeposition of silver on quantum dots is described. The particular characteristics of the nanostructured silver thus obtained are studied by electrochemical and microscopic techniques. On one hand, quantum dots were found to catalyze the silver electrodeposition, and on the other hand, a strong adsorption between electrodeposited silver and quantum dots was observed, indicated by two silver stripping processes. Nucleation of silver nanoparticles followed different mechanisms depending on the surface (carbon or quantum dots). Voltammetric and confocal microscopy studies showed the great influence of electrodeposition time on surface coating, and high-resolution transmission electron microscopy (HRTEM) imaging confirmed the initial formation of Janus-like Ag@QD nanoparticles in this process. By use of moderate electrodeposition conditions such as 50 μM silver, -0.1 V, and 60 s, the silver was deposited only on quantum dots, allowing the generation of localized nanostructured electrode surfaces. This methodology can also be employed for sensing applications, showing a promising ultrasensitive electrochemical method for quantum dot detection.

Evaluation of dose dependent antimicrobial activity of self-assembled chitosan, nano silver and chitosan-nano silver composite against several pathogens.

PubMed

Tareq, Foysal Kabir; Fayzunnesa, Mst; Kabir, Md Shahariar; Nuzat, Musrat

2018-01-01

The aim of this investigation to preparation of silver nanoparticles organized chitosan nano polymer, which effective against microbial and pathogens, when apply to liquid medium and edible food products surface, will rescue the growth of microbes. Self-assembly approach used to synthesis of silver nanoparticles and silver nanoparticles organized chitosan nano polymer. Silver nanoparticles and silver nanoparticles organized chitosan nano polymer and film characterized using Ultra-violate visible spectrometer (UV-vis), X-ray diffraction (X-ray), and Scanning electronic microscope (SEM). The crystalline structured protein capped nano silver successfully synthesized at range of 12 nm-29 nm and organized into chitosan nano polymer. Antimicrobial ingredient in liquid medium and food product surface provide to rescue oxidative change and growth of microorganism to provide higher safety. The silver nanoparticles organized chitosan nano polymer caused the death of microorganism. The materials in nano scale synthesized successfully using self-assembly method, which showed good antimicrobial properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

An environmentally benign antimicrobial nanoparticle based on a silver-infused lignin core.

PubMed

Richter, Alexander P; Brown, Joseph S; Bharti, Bhuvnesh; Wang, Amy; Gangwal, Sumit; Houck, Keith; Cohen Hubal, Elaine A; Paunov, Vesselin N; Stoyanov, Simeon D; Velev, Orlin D

2015-09-01

Silver nanoparticles have antibacterial properties, but their use has been a cause for concern because they persist in the environment. Here, we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and, together with silver ions, can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies have shown that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles.

Physicochemical fabrication of antibacterial calcium phosphate submicrospheres with dispersed silver nanoparticles via coprecipitation and photoreduction under laser irradiation.

PubMed

Nakamura, Maki; Oyane, Ayako; Shimizu, Yoshiki; Miyata, Saori; Saeki, Ayumi; Miyaji, Hirofumi

2016-12-01

We achieved rapid, surfactant-free, and one-pot fabrication of antibacterial calcium phosphate (CaP) submicrospheres containing silver nanoparticles by combining physical laser and chemical coprecipitation processes. In this physicochemical process, weak pulsed laser irradiation (20min) was performed on a labile CaP reaction mixture supplemented with silver ions as a light-absorbing agent. The silver content in the submicrospheres was controlled for a wide range (Ag/P elemental ratio varied from 0.60 to 62.0) by tuning the initial concentration of silver ions (from 5 to 20mM) in the CaP reaction mixture. At the silver concentration of 5mM, we obtained unique nanocomposite particles: CaP submicrospheres (average diameter of approximately 500nm) containing metallic silver nanoparticles dispersed throughout, as a result of CaP and silver coprecipitation with simultaneous photoreduction of silver ions and spheroidization of the coprecipitates. These CaP submicrospheres containing silver nanoparticles (ca. 0.3mg silver per 1mg submicrospheres) exhibited antibacterial activity against major pathogenic oral bacteria, i.e., Streptococcus mutans, Aggregatibacter actinomycetemcomitans, and Porphyromonas gingivalis. Moreover, the CaP submicrospheres dissolved and neutralized the acidic environment generated by Streptococcus mutans, demonstrating their potential as acid-neutralizing and remineralizing agents. The present process and resulting antibacterial CaP-based submicrospheres are expected to be useful in dental healthcare and infection control. Nano- and microsized spheres of calcium phosphate (CaP) containing silver nanoparticles have great potential in dental applications. Conventional fabrication processes were time-consuming or weak regarding the size/shape control of the spheres. In this study, we achieved a simple (one-pot), rapid (20-min irradiation), and surfactant-free fabrication of CaP submicrospheres containing silver nanoparticles by pulsed laser irradiation to a mixture of calcium, phosphate, and silver ion solutions. The resulting CaP submicrospheres contained metallic silver nanoparticles dispersed throughout in a sequence of reactions: CaP and silver coprecipitation, laser-induced melting and spheroidization of the coprecipitates, and photoreduction of silver ions. These submicrospheres showed antibacterial activity against oral bacteria and acid-neutralizing property in the bacterial suspension, and hence are worth considering for dental applications. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Nucleic acid nanomaterials: Silver-wired DNA

NASA Astrophysics Data System (ADS)

Auffinger, Pascal; Ennifar, Eric

2017-10-01

DNA double helical structures are supramolecular assemblies that are typically held together by classical Watson-Crick pairing. Now, nucleotide chelation of silver ions supports an extended silver-DNA hybrid duplex featuring an uninterrupted silver array.

Genetics Home Reference: Russell-Silver syndrome

MedlinePlus

... Facebook Twitter Home Health Conditions Russell-Silver syndrome Russell-Silver syndrome Printable PDF Open All Close All ... Javascript to view the expand/collapse boxes. Description Russell-Silver syndrome is a growth disorder characterized by ...

Formation Regularities of Plasmonic Silver Nanostructures on Porous Silicon for Effective Surface-Enhanced Raman Scattering

NASA Astrophysics Data System (ADS)

Bandarenka, Hanna V.; Girel, Kseniya V.; Bondarenko, Vitaly P.; Khodasevich, Inna A.; Panarin, Andrei Yu.; Terekhov, Sergei N.

2016-05-01

Plasmonic nanostructures demonstrating an activity in the surface-enhanced Raman scattering (SERS) spectroscopy have been fabricated by an immersion deposition of silver nanoparticles from silver salt solution on mesoporous silicon (meso-PS). The SERS signal intensity has been found to follow the periodical repacking of the silver nanoparticles, which grow according to the Volmer-Weber mechanism. The ratio of silver salt concentration and immersion time substantially manages the SERS intensity. It has been established that optimal conditions of nanostructured silver layers formation for a maximal Raman enhancement can be chosen taking into account a special parameter called effective time: a product of the silver salt concentration on the immersion deposition time. The detection limit for porphyrin molecules CuTMPyP4 adsorbed on the silvered PS has been evaluated as 10-11 M.

A new chemical route to a hybrid nanostructure: room-temperature solid-state reaction synthesis of Ag@AgCl with efficient photocatalysis.

PubMed

Hu, Pengfei; Cao, Yali

2012-08-07

The room-temperature solid-state chemical reaction technique has been used to synthesize the silver nanoparticle-loaded semiconductor silver@silver chloride for the first time. It has the advantages of convenient operation, lower cost, less pollution, and mass production. This simple technique created a wide array of nanosized silver particles which had a strong surface plasmon resonance effect in the visible region, and built up an excellent composite structure of silver@silver chloride hybrid which exhibited high photocatalytic activity and stability towards decomposition of organic methyl orange under visible-light illumination. Moreover, this work achieved the control of composition of the silver@silver chloride composite simply by adjusting the feed ratio of reactants. It offers an alternative method for synthesising metal@semiconductor composites.

Formation of hybrid nanocomposites polymethylolacrylamide/silver

NASA Astrophysics Data System (ADS)

Kolzunova, L. G.; Shchitovskaya, E. V.; Rodzik, I. G.

2018-05-01

In this study, polymethylolacrylamide/silver composites have been formed by incorporating silver nanoparticles into the pre-electrosynthesized polymer film. The composites were formed in a two-step process involving the sorption of silver nitrate by a polymer matrix followed by chemical reduction of Ag-ions. The presence of crystalline silver phase in the polymer was confirmed by X-ray phase analysis (XRD), plasmon resonance and scanning electron microscopy (SEM). The small-angle X-ray scattering (SAXS) method has obtained the distribution functions of silver particles over radii. It is established that the content of silver in composites without chitosan is 10-15 times higher than with its additive. The dependences of cyclic voltammetry in pure phosphate buffer (pH 6.86) and in the presence of hydrogen peroxide were obtained. It has been shown that polymer/silver composites exhibit selectivity to hydrogen peroxide.

Silver, gold, and alloyed silver-gold nanoparticles: characterization and comparative cell-biologic action

NASA Astrophysics Data System (ADS)

Mahl, Dirk; Diendorf, Jörg; Ristig, Simon; Greulich, Christina; Li, Zi-An; Farle, Michael; Köller, Manfred; Epple, Matthias

2012-10-01

Silver, gold, and silver-gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly( N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15-25 nm), gold (5-6 nm), and silver-gold (50:50; 10-12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver-gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver-gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver-gold nanoparticles in the concentration range of 5-20 μg mL-1 induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8.

Occurrence of silver minerals in a silver-rich pocket in the massive sulfide zinc-lead ores in the Edwards mine, New York

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serviss, C.R.; Grout, C.M.; Hagni, R.D.

1985-01-01

Ore microscopic examination of uncommon silver-rich ores from the Edwards mine has detected three silver minerals, native silver, freibergite, and argentite, that were previously unreported in the literature from the Balmat-Edwards district. The zinc-lead ore deposits of the Balmat-Edwards District in northern New York are composed of very coarse-grained massive sulfides, principally sphalerite, galena, and pyrite. The typical ores contain small amounts of silver in solid solution galena. Galena concentrates produced from those ores have contained an average of 15 ounces of silver per ton of 60% lead concentrates. In contrast to the typical ore a silver-rich pocket, that measuredmore » three feet by three feet on the vertical mine face and was the subject of this study, contained nearly 1% silver in a zinc ore. Ore microscopic study shows that this ore is especially characterized by abundant, relatively fine-grained chalcopyrite with anhedral pyrite inclusions. Fine-grained sphalerite, native silver, argentite, freibergite and arsenopyrite occur in association with the chalcopyrite and as fracture-fillings in gangue minerals. Geochemically anomalous amounts of tin, barium, chromium, and nickel also are present in the silver-rich pocket. The silver-rich pocket may mark the locus of an early feeder vent or alternatively it may record a hydrothermal event that was superimposed upon the event responsible for the metamorphic ore textures.« less

Metal tissue levels in Steller sea lion (Eumetopias jubatus) pups.

PubMed

Holmes, Amie L; Wise, Sandra S; Goertz, Caroline E C; Dunn, J Lawrence; Gulland, Frances M D; Gelatt, Tom; Beckmen, Kimberlee B; Burek, Kathy; Atkinson, Shannon; Bozza, Mary; Taylor, Robert; Zheng, Tongzhang; Zhang, Yawei; Aboueissa, Abouel-Makarim; Wise, John Pierce

2008-08-01

The endangered Western population of the Steller sea lion declined for three decades for uncertain reasons. We present baseline data of metal concentrations in pups as a first step towards investigating the potential threat of developmental exposures to contaminants. Seven metals were investigated: arsenic, cadmium, silver, aluminum, mercury, lead and vanadium. Vanadium was detected in only a single blubber sample. Mercury appears to be the most toxicologically significant metal with concentrations in the liver well above the current action level for mercury in fish. The concentrations of aluminum, arsenic, silver, cadmium and lead were present in one-fourth to two-thirds of all samples and were at either comparable or below concentrations previously reported. Neither gender nor region had a significant effect on metal burdens. Future work should consider metal concentrations in juveniles and adults and toxicological studies need to be performed to begin to assess the toxicity of these metals.

Quantifying substrate uptake by individual cells of marine bacterioplankton by catalyzed reporter deposition fluorescence in situ hybridization combined with microautoradiography.

PubMed

Sintes, Eva; Herndl, Gerhard J

2006-11-01

Catalyzed reporter deposition fluorescence in situ hybridization combined with microautoradiography (MICRO-CARD-FISH) is increasingly being used to obtain qualitative information on substrate uptake by individual members of specific prokaryotic communities. Here we evaluated the potential for using this approach quantitatively by relating the measured silver grain area around cells taking up (3)H-labeled leucine to bulk leucine uptake measurements. The increase in the silver grain area over time around leucine-assimilating cells of coastal bacterial assemblages was linear during 4 to 6 h of incubation. By establishing standardized conditions for specific activity levels and concomitantly performing uptake measurements with the bulk community, MICRO-CARD-FISH can be used quantitatively to determine uptake rates on a single-cell level. Therefore, this approach allows comparisons of single-cell activities for bacterial communities obtained from different sites or growing under different ecological conditions.

Quantifying Substrate Uptake by Individual Cells of Marine Bacterioplankton by Catalyzed Reporter Deposition Fluorescence In Situ Hybridization Combined with Microautoradiography▿

PubMed Central

Sintes, Eva; Herndl, Gerhard J.

2006-01-01

Catalyzed reporter deposition fluorescence in situ hybridization combined with microautoradiography (MICRO-CARD-FISH) is increasingly being used to obtain qualitative information on substrate uptake by individual members of specific prokaryotic communities. Here we evaluated the potential for using this approach quantitatively by relating the measured silver grain area around cells taking up 3H-labeled leucine to bulk leucine uptake measurements. The increase in the silver grain area over time around leucine-assimilating cells of coastal bacterial assemblages was linear during 4 to 6 h of incubation. By establishing standardized conditions for specific activity levels and concomitantly performing uptake measurements with the bulk community, MICRO-CARD-FISH can be used quantitatively to determine uptake rates on a single-cell level. Therefore, this approach allows comparisons of single-cell activities for bacterial communities obtained from different sites or growing under different ecological conditions. PMID:16950912

Specific composition of native silver from the Rogovik Au-Ag deposit, Northeastern Russia

NASA Astrophysics Data System (ADS)

Kravtsova, R. G.; Tauson, V. L.; Palyanova, G. A.; Makshakov, A. S.; Pavlova, L. A.

2017-09-01

The first data on native silver from the Rogovik Au-Ag deposit in northeastern Russia are presented. The deposit is situated in central part of the Okhotsk-Chukchi Volcanic Belt (OCVB) in the territory of the Omsukchan Trough, unique in its silver resources. Native silver in the studied ore makes up finely dispersed inclusions no larger than 50 μm in size, which are hosted in quartz; fills microfractures and interstices in association with küstelite, electrum, acanthite, silver sulfosalts and selenides, argyrodite, and pyrite. It has been shown that the chemical composition of native silver, along with its typomorphic features, is a stable indication of the various stages of deposit formation and types of mineralization: gold-silver (Au-Ag), silver-base metal (Ag-Pb), and gold-silver-base metal (Au-Ag-Pb). The specificity of native silver is expressed in the amount of trace elements and their concentrations. In Au-Ag ore, the following trace elements have been established in native silver (wt %): up to 2.72 S, up to 1.86 Au, up to 1.70 Hg, up to 1.75 Sb, and up to 1.01 Se. Native silver in Ag-Pb ore is characterized by the absence of Au, high Hg concentrations (up to 12.62 wt %), and an increase in Sb, Se, and S contents; the appearance of Te, Cu, Zn, and Fe is notable. All previously established trace elements—Hg, Au, Sb, Se, Te, Cu, Zn, Fe, and S—are contained in native silver of Au-Ag-Pb ore. In addition, Pb appears, and silver and gold amalgams are widespread, as well as up to 24.61 wt % Hg and 11.02 wt % Au. Comparison of trace element concentrations in native silver at the Rogovik deposit with the literature data, based on their solubility in solid silver, shows that the content of chalcogenides (S, Se, Te) exceeds saturated concentrations. Possible mechanisms by which elevated concentrations of these elements are achieved in native silver are discussed. It is suggested that the appearance of silver amalgams, which is unusual for Au-Ag mineralization not only in the Omsukchan Trough, but also in OCVB as a whole, is caused by superposition of the younger Dogda-Erikit Hg-bearing belt on the older Ag-bearing Omsukchan Trough. In practice, the results can be used to determine the general line of prospecting and geological exploration at objects of this type.

17 CFR 31.3 - Fraud in connection with certain transactions in silver or gold bullion or bulk coins, or other...

Code of Federal Regulations, 2014 CFR

2014-04-01

... certain transactions in silver or gold bullion or bulk coins, or other commodities. 31.3 Section 31.3... in connection with certain transactions in silver or gold bullion or bulk coins, or other commodities... transaction for the purchase, sale or delivery of silver bullion, gold bullion, bulk silver coins, bulk gold...

17 CFR 31.3 - Fraud in connection with certain transactions in silver or gold bullion or bulk coins, or other...

Code of Federal Regulations, 2011 CFR

2011-04-01

... certain transactions in silver or gold bullion or bulk coins, or other commodities. 31.3 Section 31.3... in connection with certain transactions in silver or gold bullion or bulk coins, or other commodities... transaction for the purchase, sale or delivery of silver bullion, gold bullion, bulk silver coins, bulk gold...

17 CFR 31.3 - Fraud in connection with certain transactions in silver or gold bullion or bulk coins, or other...

Code of Federal Regulations, 2013 CFR

2013-04-01

... certain transactions in silver or gold bullion or bulk coins, or other commodities. 31.3 Section 31.3... in connection with certain transactions in silver or gold bullion or bulk coins, or other commodities... transaction for the purchase, sale or delivery of silver bullion, gold bullion, bulk silver coins, bulk gold...

17 CFR 31.3 - Fraud in connection with certain transactions in silver or gold bullion or bulk coins, or other...

Code of Federal Regulations, 2012 CFR

2012-04-01

... certain transactions in silver or gold bullion or bulk coins, or other commodities. 31.3 Section 31.3... in connection with certain transactions in silver or gold bullion or bulk coins, or other commodities... transaction for the purchase, sale or delivery of silver bullion, gold bullion, bulk silver coins, bulk gold...

36 CFR § 1238.30 - What must agencies do when transferring permanent microform records to the National Archives of...

Code of Federal Regulations, 2013 CFR

2013-07-01

... information specified in § 1232.14(c) of this subchapter. (c) Transfer the silver gelatin original (or duplicate silver gelatin microform created in accordance with § 1238.14) plus one microform copy. (d) Ensure... non-silver copies separately from the silver gelatin original or silver duplicate microform copy and...

Development and Optimization of Silver Nanoparticle Formulation for Fabrication

DTIC Science & Technology

2015-08-14

Development and Optimization of Silver Nanoparticle Formulation for Fabrication Publication Type: DJournal/ Paper D Book Chapter ~ Tech Report D...leofPublicationorPresentation: Deve l opment and Optimization of Silver Nanoparticle Formulation for Fabrication 3. Author(s): (List authors starting...fabrication process of silver nanoparticl es could improve future silver containing products , which is i mpor tant to l owering toxicity and improving

Piper nigrum leaf and stem assisted green synthesis of silver nanoparticles and evaluation of its antibacterial activity against agricultural plant pathogens.

PubMed

Paulkumar, Kanniah; Gnanajobitha, Gnanadhas; Vanaja, Mahendran; Rajeshkumar, Shanmugam; Malarkodi, Chelladurai; Pandian, Kannaiyan; Annadurai, Gurusamy

2014-01-01

Utilization of biological materials in synthesis of nanoparticles is one of the hottest topics in modern nanoscience and nanotechnology. In the present investigation, the silver nanoparticles were synthesized by using the leaf and stem extract of Piper nigrum. The synthesized nanoparticle was characterized by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray analysis (EDAX), and Fourier Transform Infrared Spectroscopy (FTIR). The observation of the peak at 460 nm in the UV-vis spectra for leaf- and stem-synthesized silver nanoparticles reveals the reduction of silver metal ions into silver nanoparticles. Further, XRD analysis has been carried out to confirm the crystalline nature of the synthesized silver nanoparticles. The TEM images show that the leaf- and stem-synthesized silver nanoparticles were within the size of about 7-50 nm and 9-30 nm, respectively. The FTIR analysis was performed to identify the possible functional groups involved in the synthesis of silver nanoparticles. Further, the antibacterial activity of the green-synthesized silver nanoparticles was examined against agricultural plant pathogens. The antibacterial property of silver nanoparticles is a beneficial application in the field of agricultural nanotechnology.

The effect and safety of dressing composed by nylon threads covered with metallic silver in wound treatment.

PubMed

Brogliato, Ariane R; Borges, Paula A; Barros, Janaina F; Lanzetti, Manuela; Valença, Samuel; Oliveira, Nesser C; Izário-Filho, Hélcio J; Benjamim, Claudia F

2014-04-01

Silver is used worldwide in dressings for wound management. Silver has demonstrated great efficacy against a broad range of microorganisms, but there is very little data about the systemic absorption and toxicity of silver in vivo. In this study, the antimicrobial effect of the silver-coated dressing (SilverCoat(®)) was evaluated in vitro against the most common microorganisms found in wounds, including Pseudomonas aeruginosa, Candida albicans, Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus and Klebsiella pneumoniae. We also performed an excisional skin lesion assay in mice to evaluate wound healing after 14 days of treatment with a silver-coated dressing, and we measured the amount of silver in the blood, the kidneys and the liver after treatment. Our data demonstrated that the nylon threads coated with metallic silver have a satisfactory antimicrobial effect in vitro, and the prolonged use of these threads did not lead to systemic silver absorption, did not induce toxicity in the kidneys and the liver and were not detrimental to the normal wound-healing process. © 2012 The Authors. International Wound Journal © 2012 Medicalhelplines.com Inc and John Wiley & Sons Ltd.

Powerful colloidal silver nanoparticles for the prevention of gastrointestinal bacterial infections

NASA Astrophysics Data System (ADS)

Le, Anh-Tuan; Tam Le, Thi; Quy Nguyen, Van; Hoang Tran, Huy; Dang, Duc Anh; Tran, Quang Huy; Vu, Dinh Lam

2012-12-01

In this work we have demonstrated a powerful disinfectant ability of colloidal silver nanoparticles (NPs) for the prevention of gastrointestinal bacterial infections. The silver NPs colloid was synthesized by a UV-enhanced chemical precipitation. Two gastrointestinal bacterial strains of Escherichia coli (ATCC 43888-O157:k-:H7) and Vibrio cholerae (O1) were used to verify the antibacterial activity of the as-prepared silver NPs colloid by means of surface disinfection assay in agar plates and turbidity assay in liquid media. Transmission electron microscopy was also employed to analyze the ultrastructural changes of bacterial cells caused by silver NPs. Noticeably, our silver NPs colloid displayed a highly effective bactericidal effect against two tested gastrointestinal bacterial strains at a silver concentration as low as ˜3 mg l-1. More importantly, the silver NPs colloid showed an enhancement of antibacterial activity and long-lasting disinfectant effect as compared to conventional chloramin B (5%) disinfection agent. These advantages of the as-prepared colloidal silver NPs make them very promising for environmental treatments contaminated with gastrointestinal bacteria and other infectious pathogens. Moreover, the powerful disinfectant activity of silver-containing materials can also help in controlling and preventing further outbreak of diseases.

Residence of silver in mineral deposits of the Thunder Mountain caldera complex, Central Idaho, U.S.A.

USGS Publications Warehouse

Leonard, B.F.; Christian, R.P.

1987-01-01

Silver is an accessory element in gold, antimony, and tungsten deposits of the caldera complex. Most of the deposits are economically of low grade and genetically of xenothermal or epithermal character. Their gold- and silver-bearing minerals are usually disseminated, fine grained, and difficult to study. Sparsely disseminated pyrite and arsenoprite are common associates. Identified silver minerals are: native silver and electrum; the sulfides acanthite, argentite (the latter always inverted to acanthite), and members of the Silberkies group; the sulfosalts matildite, miargyrite, pyrargyrite, argentian tetrahedrite, and unnamed Ag-Sb-S and Ag-Fe-Sb-S minerals; the telluride hessite and the selenide naumannite; halides of the cerargyrite group; and the antimonate stetefeldtite. Suspected silver minerals include the sulfide uytenbogaardtite and the sulfosalts andorite, diaphorite, and polybasite. Electrum, acanthite, and argentian tetrahedrite are common, though nowhere abundant. The other silver minerals are rare. Silver is present as a minor element in the structure of some varieties of other minerals. These include arsenopyrite, chalcopyrite, chalcostibite, covelline, digenite, galena, sphalerite, and stibnite. The search for adventitious Ag in most of these minerals has been cursory. The results merely indicate that elemental silver is not confined to discrete silver minerals and is, therefore, an additional complication for the recovery of silver-bearing material from some deposits. Silver occurs cryptically in some plants of the region. At Red Mountain, for example, the ashed sapwood of Douglas-fir (Pseudotsuga menziesii) contains 2 to 300 ppm Ag. Silver in the ashed wood is roughly 100 times as abundant as it is in soil. The phenomenon, useful in biogeochemical exploration, deserves the attention of mineralogists. ?? 1987 Springer-Verlag.

In Vitro Assessment of the Antibacterial Potential of Silver Nano-Coatings on Cotton Gauzes for Prevention of Wound Infections

PubMed Central

Paladini, Federica; Di Franco, Cinzia; Panico, Angelica; Scamarcio, Gaetano; Sannino, Alessandro; Pollini, Mauro

2016-01-01

Multidrug-resistant organisms are increasingly implicated in acute and chronic wound infections, thus compromising the chance of therapeutic options. The resistance to conventional antibiotics demonstrated by some bacterial strains has encouraged new approaches for the prevention of infections in wounds and burns, among them the use of silver compounds and nanocrystalline silver. Recently, silver wound dressings have become widely accepted in wound healing centers and are commercially available. In this work, novel antibacterial wound dressings have been developed through a silver deposition technology based on the photochemical synthesis of silver nanoparticles. The devices obtained are completely natural and the silver coatings are characterized by an excellent adhesion without the use of any binder. The silver-treated cotton gauzes were characterized through scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA) in order to verify the distribution and the dimension of the silver particles on the cotton fibers. The effectiveness of the silver-treated gauzes in reducing the bacterial growth and biofilm proliferation has been demonstrated through agar diffusion tests, bacterial enumeration test, biofilm quantification tests, fluorescence and SEM microscopy. Moreover, potential cytotoxicity of the silver coating was evaluated through 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide colorimetric assay (MTT) and the extract method on fibroblasts and keratinocytes. Inductively coupled plasma mass spectrometry (ICP-MS) was performed in order to determine the silver release in different media and to relate the results to the biological characterization. All the results obtained were compared with plain gauzes as a negative control, as well as gauzes treated with a higher silver percentage as a positive control. PMID:28773531

Mineral resource of the month: silver

USGS Publications Warehouse

Brooks, William E.

2007-01-01

Silver has been used for thousands of years as ornaments and utensils, for trade and as the basis of many monetary systems. The metal has played an important part in world history. Silver from the mines at Laurion, Greece, for example, financed the Greek victory over the Persians in 480 B.C. Silver from Potosi, Bolivia, helped Spain become a world power in the 16th and 17th centuries. And silver from the gold-silver ores at the Comstock Lode in Virginia City, Nev., helped keep the Union solvent during the Civil War.

Do physico-chemical properties of silver nanoparticles decide their interaction with biological media and bactericidal action? A review.

PubMed

Pareek, Vikram; Gupta, Rinki; Panwar, Jitendra

2018-09-01

The unprecedented increase in antibiotic resistance in this era has resuscitated the attention of scientific community to exploit silver and its various species as antimicrobial agents. Plenty of studies have been done to measure the antimicrobial potential of silver species (cationic silver, metallic Ag 0 or silver nanoparticles, silver oxide particulates etc.) and indicated that membrane damage, oxidative stress, protein dysfunction and DNA damage to be the possible cause of injury to the microbial cell. However, the precise molecular mechanism of their mode of action has remained unclear, which makes an obstacle towards the generation of potential antibacterial agent against various pathogenic and multidrug resistant (MDR) bacteria. In order to endeavor this issue, one should first have the complete understanding about the resistance mechanisms present in bacteria that can be a therapeutic target for the silver-based drug formulations. Apart from this, in-depth understanding of the interactions of various silver species (with the biological media) is a probable deciding factor for the synthesis of silver-based drug formulations because the particular form and physico-chemical properties of silver can ultimately decide their antimicrobial action. In context to above mentioned serious concerns, the present article aims to discuss the mechanisms behind the confrontation of bacteria against various drugs and the effect of physico-chemical properties of silver species on their bactericidal action as well as critically evaluates the available reports on bacterial transcriptomic and proteomic profiles upon the exposure of various silver species. Further, this review state the mechanism of action that needs to be followed for the complete understanding of toxic potential of silver nanoparticles, which will open a possibility to synthesize new silver nanoparticle based antimicrobial systems with desired properties to ensure their safe use, exposure over extended period and fate in human body and environment. Copyright © 2018 Elsevier B.V. All rights reserved.

Three-body wear of a hand-consolidated silver alternative to amalgam.

PubMed

Xu, H H; Eichmiller, F C; Giuseppetti, A A; Ives, L K; Parry, E E; Schumacher, G E

1999-09-01

Recent studies have investigated a mercury-free silver alternative to amalgam, but the silver powders required a relatively high compaction pressure to consolidate. The aim of the present study was to consolidate a precipitated silver powder into a cohesive solid using an air-driven pneumatic condenser fitted with an amalgam plugger at a clinically realistic load, and to study the mechanisms and rates of three-body wear of the consolidated silver in comparison with that of an amalgam. The silver powder was annealed, rinsed with a dilute acid, and consolidated either in a prepared tooth cavity or in a specimen mold at a load of 15 N. A four-station wear machine was used where each specimen was immersed in a slurry containing polymethyl methacrylate beads, then a steel pin was loaded and rotated against the specimen at a maximum load of 76 N. The flexural strength in MPa (mean +/- SD; n = 10) was 86 +/- 20 for amalgam, 181 +/- 45 for silver with a polished surface, and 202 +/- 21 for silver with a burnished surface. After 4 x 10(5) wear cycles, the wear scar depth in microm was 134 +/- 54 for amalgam, 143 +/- 8 for polished silver, and 131 +/- 9 for burnished silver, which were not significantly different (Tukey's multiple comparison test; family confidence coefficient = 0.95). SEM examination revealed cracks and fracture pits in the worn surface of amalgam, in contrast to a smooth surface in silver. Wear and material removal in amalgam occurred by microfracture and dislodgement of cracked segments, while wear in the silver occurred by ductile deformation and flow of materials. To conclude, the consolidated silver possesses a three-body wear resistance similar to that of amalgam, and a higher resistance to wear-induced damage and cracking than amalgam. The mechanism of wear in amalgam is microfracture and material dislodgement, while that in consolidated silver is ductile deformation and flow of material.

Synthesis and characterization of silver nanoparticles from (bis)alkylamine silver carboxylate precursors.

PubMed

Uznanski, Pawel; Zakrzewska, Joanna; Favier, Frederic; Kazmierski, Slawomir; Bryszewska, Ewa

2017-01-01

A comparative study of amine and silver carboxylate adducts [R 1 COOAg-2(R 2 NH 2 )] (R 1  = 1, 7, 11; R 2  = 8, 12) as a key intermediate in NPs synthesis is carried out via differential scanning calorimetry, solid-state FT-infrared spectroscopy, 13 C CP MAS NMR, powder X-ray diffraction and X-ray photoelectron spectroscopy, and various solution NMR spectroscopies ( 1 H and 13 C NMR, pulsed field gradient spin-echo NMR, and ROESY). It is proposed that carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination as opposed to bridging bidentate coordination of pure silver carboxylates resulting from the formation of dimeric units. All complexes are packed as lamellar bilayer structures. Silver carboxylate/amine complexes show one first-order melting transition. The evidence presented in this study shows that phase behavior of monovalent metal carboxylates are controlled, mainly, by head group bonding. In solution, insoluble silver salt is stabilized by amine molecules which exist in dynamic equilibrium. Using (bis)amine-silver carboxylate complex as precursor, silver nanoparticles were fabricated. During high-temperature thermolysis, the (bis)amine-carboxylate adduct decomposes to produce silver nanoparticles of small size. NPs are stabilized by strongly interacting carboxylate and trace amounts of amine derived from the silver precursor interacting with carboxylic acid. A corresponding aliphatic amide obtained from silver precursor at high-temperature reaction conditions is not taking part in the stabilization. Combining NMR techniques with FTIR, it was possible to follow an original stabilization mechanism. Graphical abstractThe synthesis of a series (bis)alkylamine silver(I) carboxylate complexes in nonpolar solvents were carried out and fully characterized both in the solid and solution. Carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination. The complexes form layered structures which thermally decompose forming nanoparticles stabilized only by aliphatic carboxylates.

Determination of silver nanoparticle release from antibacterial fabrics into artificial sweat

PubMed Central

2010-01-01

Silver nanoparticles have been used in numerous commercial products, including textiles, to prevent bacterial growth. Meanwhile, there is increasing concern that exposure to these nanoparticles may cause potential adverse effects on humans as well as the environment. This study determined the quantity of silver released from commercially claimed nanosilver and laboratory-prepared silver coated fabrics into various formulations of artificial sweat, each made according to AATCC, ISO and EN standards. For each fabric sample, the initial amount of silver and the antibacterial properties against the model Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria on each fabric was investigated. The results showed that silver was not detected in some commercial fabrics. Furthermore, antibacterial properties of the fabrics varied, ranging from 0% to greater than 99%. After incubation of the fabrics in artificial sweat, silver was released from the different fabrics to varying extents, ranging from 0 mg/kg to about 322 mg/kg of fabric weight. The quantity of silver released from the different fabrics was likely to be dependent on the amount of silver coating, the fabric quality and the artificial sweat formulations including its pH. This study is the unprecedented report on the release of silver nanoparticles from antibacterial fabrics into artificial sweat. This information might be useful to evaluate the potential human risk associated with the use of textiles containing silver nanoparticles. PMID:20359338

Gold and silver nanoparticles from Trianthema decandra: synthesis, characterization, and antimicrobial properties

PubMed Central

Geethalakshmi, R; Sarada, DVL

2012-01-01

Background There is an increasing commercial demand for nanoparticles due to their wide applicability in various markets, including medicine, catalysis, electronics, chemistry, and energy. In this report, a simple and ecofriendly chemical reaction for the synthesis of gold and silver nanoparticles from Trianthema decandra (Aizoaceae) has been developed. Methods and results On treatment of aqueous solutions containing chloroauric acid or silver nitrate with root extract of T. decandra, stable gold or silver nanoparticles were rapidly formed. The kinetics of reduction of gold and silver ions during the reaction was analyzed by ultraviolet-visible spectroscopy. Field emission-scanning electron microscopy showed formation of gold nanoparticles in various shapes, including spherical, cubical, triangular, and hexagonal, while silver nanoparticles were spherical. The size of the gold nanoparticles was 33–65 nm and that of the silver nanoparticles was 36–74 nm. Energy dispersive x-ray and Fourier transform infrared spectroscopy confirmed the presence of metallic gold and metallic silver in the respective nanoparticles. The antimicrobial properties of the synthesized nanoparticles were analyzed using the Kirby-Bauer method. The results show varied susceptibility of microorganisms to the gold and silver nanoparticles. Conclusion It is believed that phytochemicals present in T. decandra extract reduce the silver and gold ions into metallic nanoparticles. This strategy reduces the cost of production and the environmental impact. The silver and gold nanoparticles formed showed strong activity against all microorganisms tested. PMID:23091381

Effect of Silver Flakes in Silver Paste on the Joining Process and Properties of Sandwich Power Modules (IGBTs Chip/Silver Paste/Bare Cu)

NASA Astrophysics Data System (ADS)

Zhao, Su-Yan; Li, Xin; Mei, Yun-Hui; Lu, Guo-Quan

2016-11-01

In this study, a silver paste has been introduced for attaching chips onto bare Cu substrates (without coating) without applying pressure. Small nano-thickness Ag flakes, measuring 1 μm-5 μm length, were embedded uniformly in Ag nanoparticles for improving the density of the material. The presence of silver flakes in the silver paste affected the joining process and its microstructure. Microstructure characterization revealed that densification of the silver layer was affected by the presence of silver flakes as the flakes coarsened and formed reactive in situ nanoparticles, which facilitated the sintering between the flakes and the incorporated nanoparticles. Coarsening of silver flakes depended on the sintering temperature, time, and the atmosphere, which affected the decomposition and burning out of organics presented on the surface of the flakes. A high-density silver layer was obtained due to the presence of compact silver flakes. With an increase in the microstructure density, a higher bonding strength and a lower thermal impedance of the sintered joints were achieved. On performing pressureless sintering at 270°C for 30 min under 99.99% N2 or 4% H2/N2, the bonding strength and thermal impedance for 11 × 11 mm2 chips were excellent, measuring approximately 21.9 MPa and 0.077°C/W, respectively.

Synthesis and characterization of colloidal fluorescent silver nanoclusters.

PubMed

Huang, Sherry; Pfeiffer, Christian; Hollmann, Jana; Friede, Sebastian; Chen, Justin Jin-Ching; Beyer, Andreas; Haas, Benedikt; Volz, Kerstin; Heimbrodt, Wolfram; Montenegro Martos, Jose Maria; Chang, Walter; Parak, Wolfgang J

2012-06-19

Ultrasmall water-soluble silver nanoclusters are synthesized, and their properties are investigated. The silver nanoclusters have high colloidal stability and show fluorescence in the red. This demonstrates that like gold nanoclusters also silver nanoclusters can be fluorescent.

Synthesis, characterization and catalytic activity of silver nanoparticles using Tribulus terrestris leaf extract.

PubMed

Ashokkumar, S; Ravi, S; Kathiravan, V; Velmurugan, S

2014-01-01

Biomediated silver nanoparticles were synthesized with the aid of an eco-friendly biomaterial, namely, aqueous Tribulus terrestris extract. Silver nanoparticles were synthesized using a rapid, single step, and completely green biosynthetic method employing aqueous T. terrestris leaf extracts as both the reducing and capping agent. Silver ions were rapidly reduced by aqueous T. terrestris leaf extracts, leading to the formation of highly crystalline silver nanoparticles. An attempt has been made and formation of the silver nanoparticles was verified by surface plasmon spectra using an UV-vis (Ultra violet), spectrophotometer. Morphology and crystalline structure of the prepared silver nanoparticles were characterized by TEM (Transmission Electron Microscope) and XRD (X-ray Diffraction), techniques, respectively. FT-IR (Fourier Transform Infrared), analysis suggests that the obtained silver nanoparticles might be stabilized through the interactions of carboxylic groups, carbonyl groups and the flavonoids present in the T. terrestris extract. Copyright © 2013 Elsevier B.V. All rights reserved.

Green synthesis and characterization of silver nanoparticles using alcoholic flower extract of Nyctanthes arbortristis and in vitro investigation of their antibacterial and cytotoxic activities.

PubMed

Gogoi, Nayanmoni; Babu, Punuri Jayasekhar; Mahanta, Chandan; Bora, Utpal

2015-01-01

Here we report the synthesis of silver nanoparticles using ethanolic flower extract of Nyctanthes arbortristis, UVvisible spectra and TEM indicated the successful formation of silver nanoparticles. Crystalline nature of the silver nanoparticles was confirmed by X-ray diffraction. Fourier Transform Infra-Red Spectroscopy analysis established the capping of the synthesized silver nanoparticles with phytochemicals naturally occurring in the ethanolic flower extract of N. arbortristis. The synthesized silver nanoparticles showed antibacterial activity against the pathogenic strain of Escherichia coli MTCC 443. Furthermore, cytotoxicity of the silver nanoparticles was tested on mouse fibroblastic cell line (L929) and found to be non-toxic, which thus proved their biocompatibility. Antibacterial activity and cytotoxicity assay carried out in this study open up an important perspective of the synthesized silver nanoparticles. Copyright © 2014 Elsevier B.V. All rights reserved.

Interaction of DNA bases with silver nanoparticles: assembly quantified through SPRS and SERS.

PubMed

Basu, Soumen; Jana, Subhra; Pande, Surojit; Pal, Tarasankar

2008-05-15

Colloidal silver nanoparticles were prepared by reducing silver nitrate with sodium borohydride. The synthesized silver particles show an intense surface plasmon band in the visible region. The work reported here describes the interaction between nanoscale silver particles and various DNA bases (adenine, guanine, cytosine, and thymine), which are used as molecular linkers because of their biological significance. In colloidal solutions, the color of silver nanoparticles may range from red to purple to orange to blue, depending on the degree of aggregation as well as the orientation of the individual particles within the aggregates. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and absorption spectroscopy were used to characterize the assemblies. DNA base-induced differential silver nanoparticle aggregation was quantified from the peak separation (relates to color) of surface plasmon resonance spectroscopy (SPRS) and the signal intensity of surface-enhanced Raman scattering (SERS), which rationalize the extent of silver-nucleobase interactions.

Facile chemical routes to mesoporous silver substrates for SERS analysis

PubMed Central

Tastekova, Elina A; Polyakov, Alexander Yu; Goldt, Anastasia E; Sidorov, Alexander V; Oshmyanskaya, Alexandra A; Sukhorukova, Irina V; Shtansky, Dmitry V; Grünert, Wolgang

2018-01-01

Mesoporous silver nanoparticles were easily synthesized through the bulk reduction of crystalline silver(I) oxide and used for the preparation of highly porous surface-enhanced Raman scattering (SERS)-active substrates. An analogous procedure was successfully performed for the production of mesoporous silver films by chemical reduction of oxidized silver films. The sponge-like silver blocks with high surface area and the in-situ-prepared mesoporous silver films are efficient as both analyte adsorbents and Raman signal enhancement mediators. The efficiency of silver reduction was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The developed substrates were applied for SERS detection of rhodamine 6G (enhancement factor of about 1–5 × 105) and an anti-ischemic mildronate drug (meldonium; enhancement factor of ≈102) that is known for its ability to increase the endurance performance of athletes. PMID:29600149

Preparation and characterization of silver nanoparticles homogenous thin films

NASA Astrophysics Data System (ADS)

Hegazy, Maroof A.; Borham, E.

2018-06-01

The wet chemical method by metal salt reduction has been widely used to synthesize nanoparticles. Accordingly the silver nitrate used as silver precursor and sodium borohydrate as reduction agent. The silver nanoparticles were characterized by different characterization techniques including UV-VIS spectrometry, Transmission electron microscope (TEM), and Zeta potential technique. Thin films of the colloidal solution were fabricated using direct precipitation technique on ITO glass, silicon substrate and commercial glass substrate and characterized by imaging technique. The absorption peak of the silver nanoparticles colloidal solution was around 400 nm. The TEM images indicate that the silver nanoparticles had spherical shape and their sizes were from 10 to 17 nm. The particle size of the silver nanoparticles was confirmed by Zeta potential technique. The imaging technique indicated that the homogeneous distribution of the colloidal silver solution thin film on the silicon substrate was stronger than the ITO glass and inhomogeneous film was emerged on the commercial glass.

Synthesis of silver nanoparticles in melts of amphiphilic polyesters

NASA Astrophysics Data System (ADS)

Vasylyev, S.; Damm, C.; Segets, D.; Hanisch, M.; Taccardi, N.; Wasserscheid, P.; Peukert, W.

2013-03-01

The current work presents a one-step procedure for the synthesis of amphiphilic silver nanoparticles suitable for production of silver-filled polymeric materials. This solvent free synthesis via reduction of Tollens’ reagent as silver precursor in melts of amphiphilic polyesters consisting of hydrophilic poly(ethylene glycol) blocks and hydrophobic alkyl chains allows the production of silver nanoparticles without any by-product formation. This makes them especially interesting for the production of medical devices with antimicrobial properties. In this article the influences of the chain length of the hydrophobic block in the amphiphilic polyesters and the process temperature on the particle size distribution (PSD) and the stability of the particles against agglomeration are discussed. According to the results of spectroscopic and viscosimetric investigations the silver precursor is reduced to elemental silver nanoparticles by a single electron transfer process from the poly(ethylene glycol) chain to the silver ion.

Extracellular biosynthesis of silver nanoparticles using the fungus Fusarium semitectum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Basavaraja, S.; Balaji, S.D.; Department of Chemistry, Gulbarga University, Gulbarga 585106, Karnataka

2008-05-06

Development of environmental friendly procedures for the synthesis of metal nanoparticles through biological processes is evolving into an important branch of nanobiotechnology. In this paper, we report on the use of fungus 'Fusarium semitectum' for the extracellular synthesis of silver nanoparticles from silver nitrate solution (i.e. through the reduction of Ag{sup +} to Ag{sup 0}). Highly stable and crystalline silver nanoparticles are produced in solution by treating the filtrate of the fungus F. semitectum with the aqueous silver nitrate solution. The formations of nanoparticles are understood from the UV-vis and X-ray diffraction studies. Transmission electron microscopy of the silver particlesmore » indicated that they ranged in size from 10 to 60 nm and are mostly spherical in shape. Interestingly the colloidal suspensions of silver nanoparticles are stable for many weeks. Possible medicinal applications of these silver nanoparticles are envisaged.« less

Potential environmental impacts of light-emitting diodes (LEDs): metallic resources, toxicity, and hazardous waste classification.

PubMed

Lim, Seong-Rin; Kang, Daniel; Ogunseitan, Oladele A; Schoenung, Julie M

2011-01-01

Light-emitting diodes (LEDs) are advertised as environmentally friendly because they are energy efficient and mercury-free. This study aimed to determine if LEDs engender other forms of environmental and human health impacts, and to characterize variation across different LEDs based on color and intensity. The objectives are as follows: (i) to use standardized leachability tests to examine whether LEDs are to be categorized as hazardous waste under existing United States federal and California state regulations; and (ii) to use material life cycle impact and hazard assessment methods to evaluate resource depletion and toxicity potentials of LEDs based on their metallic constituents. According to federal standards, LEDs are not hazardous except for low-intensity red LEDs, which leached Pb at levels exceeding regulatory limits (186 mg/L; regulatory limit: 5). However, according to California regulations, excessive levels of copper (up to 3892 mg/kg; limit: 2500), Pb (up to 8103 mg/kg; limit: 1000), nickel (up to 4797 mg/kg; limit: 2000), or silver (up to 721 mg/kg; limit: 500) render all except low-intensity yellow LEDs hazardous. The environmental burden associated with resource depletion potentials derives primarily from gold and silver, whereas the burden from toxicity potentials is associated primarily with arsenic, copper, nickel, lead, iron, and silver. Establishing benchmark levels of these substances can help manufacturers implement design for environment through informed materials substitution, can motivate recyclers and waste management teams to recognize resource value and occupational hazards, and can inform policymakers who establish waste management policies for LEDs.

Antibacterial activity of silver and zinc nanoparticles against Vibrio cholerae and enterotoxic Escherichia coli.

PubMed

Salem, Wesam; Leitner, Deborah R; Zingl, Franz G; Schratter, Gebhart; Prassl, Ruth; Goessler, Walter; Reidl, Joachim; Schild, Stefan

2015-01-01

Vibrio cholerae and enterotoxic Escherichia coli (ETEC) remain two dominant bacterial causes of severe secretory diarrhea and still a significant cause of death, especially in developing countries. In order to investigate new effective and inexpensive therapeutic approaches, we analyzed nanoparticles synthesized by a green approach using corresponding salt (silver or zinc nitrate) with aqueous extract of Caltropis procera fruit or leaves. We characterized the quantity and quality of nanoparticles by UV-visible wavelength scans and nanoparticle tracking analysis. Nanoparticles could be synthesized in reproducible yields of approximately 10(8) particles/ml with mode particles sizes of approx. 90-100 nm. Antibacterial activity against two pathogens was assessed by minimal inhibitory concentration assays and survival curves. Both pathogens exhibited similar resistance profiles with minimal inhibitory concentrations ranging between 5×10(5) and 10(7) particles/ml. Interestingly, zinc nanoparticles showed a slightly higher efficacy, but sublethal concentrations caused adverse effects and resulted in increased biofilm formation of V. cholerae. Using the expression levels of the outer membrane porin OmpT as an indicator for cAMP levels, our results suggest that zinc nanoparticles inhibit adenylyl cyclase activity. This consequently deceases the levels of this second messenger, which is a known inhibitor of biofilm formation. Finally, we demonstrated that a single oral administration of silver nanoparticles to infant mice colonized with V. cholerae or ETEC significantly reduces the colonization rates of the pathogens by 75- or 100-fold, respectively. Copyright © 2014 The Authors. Published by Elsevier GmbH.. All rights reserved.

Silver Nanoparticle Storage Stability in Aqueous and Biological Media

DTIC Science & Technology

2015-06-22

silver nanoparticle stability from the point of synthesis to the point of testing. The recommended conditions of water storage at 4°C protected from... silver nanoparticle formulation for fabrication. (Report No. 2014-73). 13 Métraux, G. S. & Mirkin, C. A. Rapid thermal synthesis of silver ...NAVAL MEDICAL RESEARCH UNIT SAN ANTONIO SILVER NANOPARTICLE STORAGE STABILITY IN AQUEOUS AND BIOLOGICAL MEDIA NATALIE A

MX Siting Investigation. Mineral Resources Survey, Seven Additional Valleys, Nevada/Utah Siting Area. Volume IV.

DTIC Science & Technology

1981-06-23

Lead, copper , silver In brecciated Devonian (?) limestone at the contact with altered grane* Porphyry (507). Silver, lead, copper , gold. Silver, lead...rhyolite and latite. Molybdenum- quartz yamns and disseminated in quartz monaonilte porphyry ( 402) Silveir, gold, lead, Silver, gold, lead, copper ...in parentheses ) Canyon) Tfungsten, gold. silver Tungsten -irregular pipelike bodies in brocaiated and silicified copper , lead. flourspar liniestone

Long-term TEM analysis of the nanoleakage patterns in resin-dentin interfaces produced by different bonding strategies.

PubMed

Reis, Andre F; Giannini, Marcelo; Pereira, Patricia N R

2007-09-01

The aim of this study was to evaluate the ability of etch-and-rinse and self-etching adhesive systems to prevent time- and water-induced nanoleakage in resin-dentin interfaces over a 6-month storage period. Five commercial adhesives were tested, which comprise three different strategies of bonding resins to tooth hard tissues: one single-step self-etching adhesive (One-up Bond F (OB), Tokuyama); two two-step self-etching primers (Clearfil SE Bond (SE) and an antibacterial fluoride-containing system, Clearfil Protect Bond (CP), Kuraray Inc.); two two-step etch-and-rinse adhesives (Single Bond (SB), 3M ESPE and Prime&Bond NT (PB), Dentsply). Restored teeth were sectioned into 0.9 mm thick slabs and stored in water or mineral oil for 24 h, 3 or 6 months. A silver tracer solution was used to reveal nanometer-sized water-filled spaces and changes that occurred over time within resin-dentin interfaces. Characterization of interfaces was performed with the TEM. The two two-step self-etching primers showed little silver uptake during the 6-month experiment. Etch-and-rinse adhesives exhibited silver deposits predominantly within the hybrid layer (HL), which significantly increased for SB after water-storage. The one-step self-etching adhesive OB presented massive silver accumulation within the HL and water-trees protruding into the adhesive layer, which increased in size and quantity after water-storage. After storage in oil, reduced silver deposition was observed at the interfaces for all groups. Different levels of water-induced nanoleakage were observed for the different bonding strategies. The two-step self-etching primers, especially the antibacterial fluoride-containing system CP, showed the least nanoleakage after 6 months of storage in water.

Electrical conductivity modification using silver nano particles of Jatropha Multifida L. and Pterocarpus Indicus w. extracts films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diantoro, Markus, E-mail: markus.diantoro.fmipa@um.ac.id; Hidayati, Nisfi Nahari Sani; Latifah, Rodatul

Natural polymers can be extracted from leaf or stem of plants. Pterocarpus Indicus W. (PIW) and Jatropha Multifida L. (JIL) plants are good candidate as natural polymer sources. PIW and JIW polymers contain chemical compound so-called flavonoids which has C{sub 6}-C{sub 3}-C{sub 6} carbons conjugated configuration. The renewable type of polymer as well as their abundancy of flavonoid provide us to explore their physical properties. A number of research have been reported related to broad synthesis method and mechanical properties. So far there is no specific report of electrical conductivity associated to PIW and JIL natural polymers. In order tomore » obtain electrical conductivity and its crystallinity of the extracted polymer films, it was induced on them a various fraction of silver nano particles. The film has been prepared by means of spin coating method on nickel substrate. It was revealed that FTIR spectra confirm the existing of rutine flavonoid. The crystallinity of the samples increase from 0.66%, to 4.11% associated to the respective various of silver fractions of 0.1 M to 0.5 M. SEM images show that there are some grains of silver in the film. The nature of electric conductivity increases a long with the addition of silver. The electrical conductivity increase significantly from 3.22 S/cm, to 542.85 S/cm. On the other hand, PIW films also shows similar trends that increase of Ag induce the increase its crystallinity as well as its electrical conductivity at semiconducting level. This result opens a prospective research and application of the green renewable polymer as optoelectronic materials.« less

Electrical conductivity modification using silver nano particles of Jatropha Multifida L. and Pterocarpus Indicus w. extracts films

NASA Astrophysics Data System (ADS)

Diantoro, Markus; Hidayati, Nisfi Nahari Sani; Latifah, Rodatul; Fuad, Abdulloh; Nasikhudin, Sujito, Hidayat, Arif

2016-03-01

Natural polymers can be extracted from leaf or stem of plants. Pterocarpus Indicus W. (PIW) and Jatropha Multifida L. (JIL) plants are good candidate as natural polymer sources. PIW and JIW polymers contain chemical compound so-called flavonoids which has C6-C3-C6 carbons conjugated configuration. The renewable type of polymer as well as their abundancy of flavonoid provide us to explore their physical properties. A number of research have been reported related to broad synthesis method and mechanical properties. So far there is no specific report of electrical conductivity associated to PIW and JIL natural polymers. In order to obtain electrical conductivity and its crystallinity of the extracted polymer films, it was induced on them a various fraction of silver nano particles. The film has been prepared by means of spin coating method on nickel substrate. It was revealed that FTIR spectra confirm the existing of rutine flavonoid. The crystallinity of the samples increase from 0.66%, to 4.11% associated to the respective various of silver fractions of 0.1 M to 0.5 M. SEM images show that there are some grains of silver in the film. The nature of electric conductivity increases a long with the addition of silver. The electrical conductivity increase significantly from 3.22 S/cm, to 542.85 S/cm. On the other hand, PIW films also shows similar trends that increase of Ag induce the increase its crystallinity as well as its electrical conductivity at semiconducting level. This result opens a prospective research and application of the green renewable polymer as optoelectronic materials.

Low-Temperature Preparation of Ag-Doped ZnO Nanowire Arrays, DFT Study, and Application to Light-Emitting Diode.

PubMed

Pauporté, Thierry; Lupan, Oleg; Zhang, Jie; Tugsuz, Tugba; Ciofini, Ilaria; Labat, Frédéric; Viana, Bruno

2015-06-10

Doping ZnO nanowires (NWs) by group IB elements is an important challenge for integrating nanostructures into functional devices with better and tuned performances. The growth of Ag-doped ZnO NWs by electrodeposition at 90 °C using a chloride bath and molecular oxygen precursor is reported. Ag acts as an electrocatalyst for the deposition and influences the nucleation and growth of the structures. The silver atomic concentration in the wires is controlled by the additive concentration in the deposition bath and a content up to 3.7 atomic % is reported. XRD analysis shows that the integration of silver enlarges the lattice parameters of ZnO. The optical measurements also show that the direct optical bandgap of ZnO is reduced by silver doping. The bandgap shift and lattice expansion are explained by first principle calculations using the density functional theory (DFT) on the silver impurity integration as an interstitial (Ag(i)) and as a substitute of zinc atom (Ag(Zn)) in the crystal lattice. They notably indicate that Ag(Zn) doping forms an impurity band because of Ag 4d and O 2p orbital interactions, shifting the Fermi level toward the valence band. At least, Ag-doped ZnO vertically aligned nanowire arrays have been epitaxially grown on GaN(001) substrate. The heterostructure has been inserted in a light emitting device. UV-blue light emission has been achieved with a low emission threshold of 5 V and a tunable red-shifted emission spectrum related to the bandgap reduction induced by silver doping of the ZnO emitter material.

The Kongsberg silver deposits, Norway: Ag-Hg-Sb mineralization and constraints for the formation of the deposits

NASA Astrophysics Data System (ADS)

Kotková, Jana; Kullerud, Kåre; Šrein, Vladimír; Drábek, Milan; Škoda, Radek

2018-04-01

The Kongsberg silver district has been investigated by microscopy and electron microprobe analysis, focusing primarily on the Ag-Hg-Sb mineralization within the context of the updated mineral paragenesis. The earliest mineralization stage is represented by sulfides, including acanthite, and sulfosalts. Native silver formed initially through breakdown of early Ag-bearing phases and later through influx of additional Ag-bearing fluids and silver remobilization. The first two generations of native silver were separated in time by the formation of Ni-Co-Fe sulfarsenides and the monoarsenide niccolite along rims of silver crystals. The presence of As-free sulfosalts and the absence of di- and tri-arsenides suggest a lower arsenic/sulfur activity ratio for the Kongsberg deposits compared to other five-element deposits. Native silver shows binary Ag-Hg and Ag-Sb solid solutions, in contrast to the ternary Ag-Hg-Sb compositions typical for other deposits of similar type. Antimonial silver together with allargentum, dyscrasite, and pyrargyrite was documented exclusively from the northern area of the district. Elsewhere, the only Sb-bearing minerals are polybasite and tetrahedrite/freibergite. Hg-rich silver (up to 21 wt% Hg) has been documented only in the central-western area. Myrmekite of freibergite and chalcopyrite reflects exsolution from an original Ag-poor tetrahedrite upon cooling, while myrmekite of pyrite and silver, forming through breakdown of low-temperature phases (argentopyrite or lenaite) upon heating, characterizes the Kongsberg silver district. Based on the stabilities of minerals and mineral assemblages, the formation of the silver mineralization can be constrained to temperatures between 180 and 250 °C.

In vitro cytotoxity of silver: implication for clinical wound care.

PubMed

Poon, Vincent K M; Burd, Andrew

2004-03-01

In this study, we look at the cytotoxic effects of silver on keratinocytes and fibroblasts. We have assessed the viability of monolayer cultures using the MTT and BrdU assays. The composition of the culture medium and also the culture technique were modified to assess the effects of culture 'environment' on the susceptibility of the cells to the toxic action of silver. Further in vitro, experiments were performed using tissue culture models to allow cellular behavior in three dimensional planes which more closely simulated in vivo behavior. The silver source was both silver released from silver nitrate solution but also nanocrystalline silver released from a commercially available dressing. The results show that silver is highly toxic to both keratinocytes and fibroblasts in monolayer culture. When using optimized and individualized culture the fibroblasts appear to be more sensitive to silver than keratinocytes. However, when both cell types were grown in the same medium their viability was the same. Using tissue culture models again indicated an 'environmental effect' with decreased sensitivity of the cells to the cytotoxic effects of the silver. Nevertheless in these studies the toxic dose of skin cells ranging from 7 x 10(-4) to 55 x 10(-4)% was similar to that of bacteria. These results suggest that consideration of the cytotoxic effects of silver and silver-based products should be taken when deciding on dressings for specific wound care strategies. This is important when using keratinocyte culture, in situ, which is playing an increasing role in contemporary wound and burn care.

Synthesis and characterization of silver nanoparticles from (bis)alkylamine silver carboxylate precursors

NASA Astrophysics Data System (ADS)

Uznanski, Pawel; Zakrzewska, Joanna; Favier, Frederic; Kazmierski, Slawomir; Bryszewska, Ewa

2017-03-01

A comparative study of amine and silver carboxylate adducts [R1COOAg-2(R2NH2)] (R1 = 1, 7, 11; R2 = 8, 12) as a key intermediate in NPs synthesis is carried out via differential scanning calorimetry, solid-state FT-infrared spectroscopy, 13C CP MAS NMR, powder X-ray diffraction and X-ray photoelectron spectroscopy, and various solution NMR spectroscopies (1H and 13C NMR, pulsed field gradient spin-echo NMR, and ROESY). It is proposed that carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination as opposed to bridging bidentate coordination of pure silver carboxylates resulting from the formation of dimeric units. All complexes are packed as lamellar bilayer structures. Silver carboxylate/amine complexes show one first-order melting transition. The evidence presented in this study shows that phase behavior of monovalent metal carboxylates are controlled, mainly, by head group bonding. In solution, insoluble silver salt is stabilized by amine molecules which exist in dynamic equilibrium. Using (bis)amine-silver carboxylate complex as precursor, silver nanoparticles were fabricated. During high-temperature thermolysis, the (bis)amine-carboxylate adduct decomposes to produce silver nanoparticles of small size. NPs are stabilized by strongly interacting carboxylate and trace amounts of amine derived from the silver precursor interacting with carboxylic acid. A corresponding aliphatic amide obtained from silver precursor at high-temperature reaction conditions is not taking part in the stabilization. Combining NMR techniques with FTIR, it was possible to follow an original stabilization mechanism.

Step-reduced synthesis of starch-silver nanoparticles.

PubMed

Raghavendra, Gownolla Malegowd; Jung, Jeyoung; Kim, Dowan; Seo, Jongchul

2016-05-01

In the present process, silver nanoparticles were directly synthesized in a single step by microwave irradiation of a mixture of starch, silver nitrate, and deionized water. This is different from the commonly adopted procedure for starch-silver nanoparticle synthesis in which silver nanoparticles are synthesized by preparing a starch solution as a reaction medium first. Thus, the additional step associated with the preparation of the starch solution was eliminated. In addition, no additional reducing agent was utilized. The adopted method was facile and straight forward, affording spherical silver nanoparticles with diameter below 10nm that exhibited good antibacterial activity. Further, influence of starch on the size of the silver nanoparticles was noticed. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation of silver nanoparticles at low temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Mini, E-mail: mishramini5@gmail.com; Chauhan, Pratima, E-mail: mangu167@yahoo.co.in

Silver from ancient time is used as antimicrobial agent in the bulk form but now with the advancement in nanotechnology silver in the form of nanoparticles shown potential effect against microbes which make us easy to fight with many diseases plants and animals. In this work silver nanoparticles were synthesized by chemical routes using sodium borohydride as reducing agent at low temperature. The particles were characterized through UV-Visible spectroscopy as well as X-Ray Diffraction. The UV-visible spectra of silver nanoparticles exhibited absorption at 425 cm; the crystallite size of the particles is between 19nm to 39nm. EDAX graph shows two peaksmore » of silver and oxygen. Water absorbed by silver nanoparticles was removed by the calcinations.« less

Preparation of silver-activated zinc sulfide thin films

NASA Technical Reports Server (NTRS)

Feldman, C.; Swindells, F. E.

1968-01-01

Silver improves luminescence and reduces contamination of zinc sulfide phosphors. The silver is added after the zinc sulfide phosphors are deposited in thin films by vapor evaporation, but before calcining, by immersion in a solution of silver salt.

76 FR 19188 - Joint Biomedical Laboratory Research and Development and Clinical Science Research and...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-06

.../Silver Spring. Neurobiology-E June 3, 2011 Crowne Plaza DC/Silver Spring. Pulmonary Medicine June 3, 2011 Crowne Plaza DC/Silver Spring. Cellular & Molecular Medicine........ June 6, 2011 Crowne Plaza DC/Silver...

Recent development in deciphering the structure of luminescent silver nanodots

NASA Astrophysics Data System (ADS)

Choi, Sungmoon; Yu, Junhua

2017-05-01

Matrix-stabilized silver clusters and stable luminescent few-atom silver clusters, referred to as silver nanodots, show notable difference in their photophysical properties. We present recent research on deciphering the nature of silver clusters and nanodots and understanding the factors that lead to variations in luminescent mechanisms. Due to their relatively simple structure, the matrix-stabilized clusters have been well studied. However, the single-stranded DNA (ssDNA)-stabilized silver nanodots that show the most diverse emission wavelengths and the best photophysical properties remain mysterious species. It is clear that their photophysical properties highly depend on their protection scaffolds. Analyses from combinations of high-performance liquid chromatography, inductively coupled plasma-atomic emission spectroscopy, electrophoresis, and mass spectrometry indicate that about 10 to 20 silver atoms form emissive complexes with ssDNA. However, it is possible that not all of the silver atoms in the complex form effective emission centers. Investigation of the nanodot structure will help us understand why luminescent silver nanodots are stable in aqueous solution and how to further improve their chemical and photophysical properties.

Stability of colloidal silver nanoparticles trapped in lipid bilayer: effect of lecithin concentration and applied temperature.

PubMed

Barani, Hossein; Montazer, Majid; Braun, Hans-Georg; Dutschk, Victoria

2014-12-01

The use of silver nanoparticle on various substrates has been widespread because of its good antibacterial properties that directly depend on the stability of the silver nanoparticles in a colloidal suspension. In this study, the colloidal solutions of the silver nanoparticles were synthesised by a simple and safe method by using lecithin as a stabilising agent and their stability was examined at various temperatures. The effect of the lecithin concentrations on the stability of the synthesised silver nanoparticles was examined from 25 to 80°C at 5°C intervals, by recording the changes in the UV-vis absorption spectra, the hydrodynamic diameter and the light scattering intensity of the silver nanoparticles. In addition, the morphology of the synthesised silver nanoparticles was investigated with the low-voltage scanning electron microscopy and transmission electron microscopy. The results indicated that increasing temperature caused different changes in the size of the stabilised and the unstabilised silver nanoparticles. The size of the stabilised silver nanoparticles reduced from 38 to 36 nm during increasing temperature, which confirmed good stability.

An environmentally benign antimicrobial nanoparticle based ...

EPA Pesticide Factsheets

Silver nanoparticles have antibacterial properties but their use has been a cause for concern because they persist in the environment. Here we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and together with silver ions can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies showed that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles

Synthesis and Characterization of Composite Hydroxyapatite-Silver Nanoparticles

NASA Astrophysics Data System (ADS)

Charlena; Nuzulia, N. A.; Handika

2017-03-01

Hydroxyapatite (HAp) is commonly used as bone implant coating recently; however, the material has disadvantage such as lack of antibacterial properties, that can cause an bacterial infection. Addition of silver nanoparticles is expected to be able to provide antibacterial properties. Silver nanoparticles was obtained by reduction of AgNO3 using glucose monohydrate with microwave heating at 100p for 4 minutes. The composite of hydroxyapatite-silver nanoparticles was synthesized using chemical methods by coprecipitation suspension of Ca(OH)2 with (NH4)HPO4, followed by adding silver nanoparticles solution. The size of the synthesized silver nanoparticles was 30-50 nm and exhibited good antibacterial activity. Nevertheless, when it was composited with HAp to form HAp-AgNPs, there was no antibacterial activity due to very low concentration of silver nanoparticles. This was indicated by the absence of silver nanoparticles diffraction patterns. Infrared spectra indicated the presence of chemical shift and the results of scanning electron microscope showed size of the HAp-AgNPs composite was smaller than that of the HAp. This showed the interaction between HAp and the silver nanoparticles.

Green Synthesis of Silver Nanoparticles by using Eucalyptus Globulus Leaf Extract

NASA Astrophysics Data System (ADS)

Balamurugan, Madheswaran; Saravanan, Shanmugam

2017-12-01

A single step eco-friendly, energy efficient and economically scalable green method was employed to synthesize silver nanoparticles. In this work, the synthesis of silver nanoparticles using Eucalyptus globulus leaf extract as reducing and capping agent along with water as solvent at normal room temperature is described. Silver nanoparticles were prepared from aqueous silver nitrate solution by adding the leaf extract. The prepared nanoparticles were characterized by using UV-visible Spectrophotometer, X-ray diffractometer, High Resolution Transmission Electron Microscope (HR-TEM) and Fourier Transform Infrared Spectroscope (FTIS). X-ray diffraction studies brought to light the crystalline nature and the face centered cubic structure of the silver nanoparticles. Using HR-TEM. the nano sizes and morphology of the particles were studied. The mean sizes of the prepared silver nanoparticles ranged from 30 to 36 nm. The density of the particles was tuned by varying the molar ratio of silver nitrate. FTIS studies showed the functional group of organic molecules which were located on the surface of the silver nanoparticles. Originating from the leaf extracts, these organic molecules reduced and capped the particles.

Silver recovery aqueous techniques from diverse sources: Hydrometallurgy in recycling.

PubMed

Syed, S

2016-04-01

The demand of silver is ever increasing with the advance of the industrialized world, whereas worldwide reserves of high grade silver ores are retreating. However, there exist large stashes of low and lean grade silver ores that are yet to be exploited. The main impression of this work was to draw attention to the most advance technologies in silver recovery and recycling from various sources. The state of the art in recovery of silver from different sources by hydrometallurgical and bio-metallurgical processing and varieties of leaching, cementing, reducing agents, peeling, electro-coagulants, adsorbents, electro-dialysis, solvent extraction, ion exchange resins and bio sorbents are highlighted in this article. It is shown that the major economic driver for recycling of depleted sources is for the recovery of silver. In order to develop an nature-friendly technique for the recovery of silver from diverse sources, a critical comparison of existing technologies is analyzed for both economic viability and environmental impact was made in this amendment and silver ion toxicity is highlighted. Copyright © 2016 Elsevier Ltd. All rights reserved.

Preparing high-adhesion silver coating on APTMS modified polyethylene with excellent anti-bacterial performance

NASA Astrophysics Data System (ADS)

Li, Wenfei; Chen, Yunxiang; Wu, Song; Zhang, Jian; Wang, Hao; Zeng, Dawen; Xie, Changsheng

2018-04-01

Silver coating as a broad-spectrum antimicrobial agent was considered to alleviate the inflammation caused by intrauterine device (IUD) in endometrium. In this work, to avoid the damage of silver coating and ensure its antibacterial properties, 3-aminopropyltrimethoxysilane (APTMS) was introduced to modify the polyethylene (PE) substrate for the purpose of improving the adhesion of the silver coating. From the 90° peel test, it could be found that the adhesive strength of silver coating on the APTMS modified PE substrate was nearly 23 times stronger than the silver coating on substrate without surface modification. The dramatically enhanced adhesive strength could be attributed to the formation of continuous chemical bonds between the silver coatings and substrates after surface modification, which had been confirmed by the XPS. Moreover, the standard antibacterial test revealed that the silver coated samples against Staphylococcus aureus (S. aureus) exhibit excellent antibacterial efficacy. Considering the largely enhanced adhesion and the effective antibacterial property, it is reasonable to believe that the silver coating could be considered as a potential candidate for the antibacterial agent in IUD.

The effectiveness of heparin, platelet-rich plasma (PRP), and silver nanoparticles on prevention of postoperative peritoneal adhesion formation in rats.

PubMed

Makarchian, Hamid Reza; Kasraianfard, Amir; Ghaderzadeh, Pezhman; Javadi, Seyed Mohammad Reza; Ghorbanpoor, Manoochehr

2017-01-01

To assess the effectiveness of heparin, platelet-rich plasma (PRP), and silver nanoparticles on prevention of postoperative adhesion in animal models. Sixty males Albino Wistar rats aged 5 to 6 weeks were classified into five groups receiving none, heparin, PRP, silver nanoparticles, PRP plus silver nanoparticles intraperitoneally. After 2 weeks, the animals underwent laparotomy and the damaged site was assessed for peritoneal adhesions severity. The mean severity scores were 2.5 ± 0.9, 2.16 ± 0.7, 1.5 ± 0.5, 2.66 ± 0.88, and 2.25 ± 0.62 in the control, heparin, PRP, silver and PRP plus silver groups, respectively with significant intergroup difference (p = 0.004). The highest effective material for preventing adhesion formation was PRP followed by heparin and PRP plus silver. Moreover, compared to the controls, only use of PRP was significantly effective, in terms of adhesion severity (p = 0.01) . Platelet-rich plasma alone may have the highest efficacy for preventing postoperative peritoneal adhesions in comparison with heparin, silver nanoparticles and PRP plus silver nanoparticles.

Green chemistry focus on optimization of silver nanoparticles using response surface methodology (RSM) and mosquitocidal activity: Anopheles stephensi (Diptera: Culicidae).

PubMed

Ondari Nyakundi, Erick; Padmanabhan, M Nalini

2015-01-01

There is an exigent necessity for development of environmental friendly bio-control agent(s) for elimination of mosquito due to increased resistance resurgence against synthetic control agents. Mosquito control strategy will lay a strong foundation to malaria exclusion or it can be curbed to certain level especially in the developing nations. In this study, silver nanoparticles were synthesized by green chemistry approach using Tridax procumbens leaf extract as a reducing agent. The reaction medium involved in the synthesis process was optimized by statistical experimental design using response surface methodology to obtain better yield, uniform size, shape and stability. Further, these synthesized nanoparticles were confirmed through UV-Visible, FT-IR spectroscopy, PSA and SEM Subsequently, the bioefficacy of these particles were investigated on Anopheles stephensi for larvicidal and pupicidal activity. Interestingly, time period of 90 min, temperature of 76±2 °C, pH 7.2±2, 2 mM silver nitrate (AgNO3), 3mM PEG and 2mM PVP showed excellent parameters for bioprocess design for large scale production of stabilized nanoparticles. A concentration of 5 ppm of PVP stabilized nanoparticles exhibited 100% mortality. Thus, the obtained results clearly suggest that silver nanoparticles stabilized by PEG and PVP may have important function as stabilizers, dispersants as well as larvicides for mosquito control. Copyright © 2015 Elsevier B.V. All rights reserved.

One stone, two birds: silica nanospheres significantly increase photocatalytic activity and colloidal stability of photocatalysts

NASA Astrophysics Data System (ADS)

Rasamani, Kowsalya D.; Foley, Jonathan J., IV; Sun, Yugang

2018-03-01

Silver-doped silver chloride [AgCl(Ag)] nanoparticles represent a unique class of visible-light-driven photocatalysts, in which the silver dopants introduce electron-abundant mid-gap energy levels to lower the bandgap of AgCl. However, free-standing AgCl(Ag) nanoparticles, particularly those with small sizes and large surface areas, exhibit low colloidal stability and low compositional stability upon exposure to light irradiation, leading to easy aggregation and conversion to metallic silver and thus a loss of photocatalytic activity. These problems could be eliminated by attaching the small AgCl(Ag) nanoparticles to the surfaces of spherical dielectric silica particles with submicrometer sizes. The high optical transparency in the visible spectral region (400-800 nm), colloidal stability, and chemical/electronic inertness displayed by the silica spheres make them ideal for supporting photocatalysts and significantly improving their stability. The spherical morphology of the dielectric silica particles can support light scattering resonances to generate significantly enhanced electric fields near the silica particle surfaces, on which the optical absorption cross-section of the AgCl(Ag) nanoparticles is dramatically increased to promote their photocatalytic activity. The hybrid silica/AgCl(Ag) structures exhibit superior photocatalytic activity and stability, suitable for supporting photocatalysis sustainably; for instance, their efficiency in the photocatalytic decomposition of methylene blue decreases by only ˜9% even after ten cycles of operation.

Mechanism of Particle Formation in Silver/Epoxy Nanocomposites Obtained through a Visible-Light-Assisted in Situ Synthesis.

PubMed

dell'Erba, Ignacio E; Martínez, Francisco D; Hoppe, Cristina E; Eliçabe, Guillermo E; Ceolín, Marcelo; Zucchi, Ileana A; Schroeder, Walter F

2017-10-03

A detailed understanding of the processes taking place during the in situ synthesis of metal/polymer nanocomposites is crucial to manipulate the shape and size of nanoparticles (NPs) with a high level of control. In this paper, we report an in-depth time-resolved analysis of the particle formation process in silver/epoxy nanocomposites obtained through a visible-light-assisted in situ synthesis. The selected epoxy monomer was based on diglycidyl ether of bisphenol A, which undergoes relatively slow cationic ring-opening polymerization. This feature allowed us to access a full description of the formation process of silver NPs before this was arrested by the curing of the epoxy matrix. In situ time-resolved small-angle X-ray scattering investigation was carried out to follow the evolution of the number and size of the silver NPs as a function of irradiation time, whereas rheological experiments combined with near-infrared and ultraviolet-visible spectroscopies were performed to interpret how changes in the rheological properties of the matrix affect the nucleation and growth of particles. The analysis of the obtained results allowed us to propose consistent mechanisms for the formation of metal/polymer nanocomposites obtained by light-assisted one-pot synthesis. Finally, the effect of a thermal postcuring treatment of the epoxy matrix on the particle size in the nanocomposite was investigated.

Electrochemical determination of paraquat in citric fruit based on electrodeposition of silver particles onto carbon paste electrode.

PubMed

Farahi, Abdelfettah; Achak, Mounia; El Gaini, Laila; El Mhammedi, Moulay Abderrahim; Bakasse, Mina

2015-09-01

Carbon paste electrodes (CPEs) modified with silver particles present an interesting tool in the determination of paraquat (PQ) using square wave voltammetry. Metallic silver particle deposits have been obtained via electrochemical deposition in acidic media using cyclic voltammetry. Scanning electron microscopy and X-ray diffraction measurements show that the silver particles are deposited onto carbon surfaces in aggregate form. The response of PQ with modified electrode (Ag-CPE) related to Ag/CP loading, preconcentration time, and measuring solution pH was investigated. The result shows that the increase in the two cathodic peak currents (Peak 1 and Peak 2), under optimized conditions, was linear with the increase in PQ concentration in the range 1.0 × 10 -7  mol/L to 1.0 × 10 -3  mol/L. The detection limit and quantification limit were 2.01 × 10 -8  mol/L and 6.073 × 10 -8  mol/L, respectively for Peak 1. The precision expressed as relative standard deviation for the concentration level 1.0 × 10 -5  mol/L (n = 8) was found to be 1.45%. The methodology was satisfactorily applied for the determination of PQ in citric fruit cultures. Copyright © 2015. Published by Elsevier B.V.

Assessment of toxicity in fresh water fish Labeo rohita treated with silver nanoparticles

NASA Astrophysics Data System (ADS)

Khan, Muhammad Saleem; Qureshi, Naureen Aziz; Jabeen, Farhat

2017-06-01

Silver nanoparticles (17.78 ± 12.12 nm) were synthesized by the reduction of 0.5 M silver nitrate using formaldehyde as reducing and triethylamine as promoting and stabilizing agent. The particles were grain like agglomerates with spherical, centered-face cubic and crystalline in nature. The sample was highly pure with amine (NH) as associated and capping molecules. Further, the genotoxicity and oxidative stress of these particles were evaluated using Labeo rohita ( L. rohita) as genetic model exposed (10-55 mg L-1 dose) through aquatic medium for 28 days. The cells were produced with micronuclei, fragmented, lobed and buds nuclei in dose dependent manner. The highest incidence of comet was recoded (27.34 ± 5.68) at 55 mg L-1 Ag-NPs and 14 days treatment. Then frequency was decreased to 22.65 ± 6.66% after 28 days due to complex repair mechanism. Moreover, the treatment also produces the oxidative stress and disturbs the level of GST in gill and liver tissue. There was a sharp decline in the activities of GST and this decrease of activity increase the MDA content. Further, the elevated level of GSH represents that the liver has started defensive mechanism against oxyraidcals. This study concluded, Ag-NPs are genotoxic in nature and produce micronuclei, comet cells and also induces oxidative stress in aquatic organisms.

Toxicity profiling of water contextual zinc oxide, silver, and titanium dioxide nanoparticles in human oral and gastrointestinal cell systems.

PubMed

Giovanni, Marcella; Tay, Chor Yong; Setyawati, Magdiel Inggrid; Xie, Jianping; Ong, Choon Nam; Fan, Rongli; Yue, Junqi; Zhang, Lifeng; Leong, David Tai

2015-12-01

Engineered nanoparticles (ENPs) are increasingly detected in water supply due to environmental release of ENPs as the by-products contained within the effluent of domestic and industrial run-off. The partial recycling of water laden with ENPs, albeit at ultra-low concentrations, may pose an uncharacterized threat to human health. In this study, we investigated the toxicity of three prevalent ENPs: zinc oxide, silver, and titanium dioxide over a wide range of concentrations that encompasses drinking water-relevant concentrations, to cellular systems representing oral and gastrointestinal tissues. Based on published in silico-predicted water-relevant ENPs concentration range from 100 pg/L to 100 µg/L, we detected no cytotoxicity to all the cellular systems. Significant cytotoxicity due to the NPs set in around 100 mg/L with decreasing extent of toxicity from zinc oxide to silver to titanium dioxide NPs. We also found that noncytotoxic zinc oxide NPs level of 10 mg/L could elevate the intracellular oxidative stress. The threshold concentrations of NPs that induced cytotoxic effect are at least two to five orders of magnitude higher than the permissible concentrations of the respective metals and metal oxides in drinking water. Based on these findings, the current estimated levels of NPs in potable water pose little cytotoxic threat to the human oral and gastrointestinal systems within our experimental boundaries. © 2014 Wiley Periodicals, Inc.

Distribution of silver in rats following 28 days of repeated oral exposure to silver nanoparticles or silver acetate

PubMed Central

2011-01-01

Background The study investigated the distribution of silver after 28 days repeated oral administration of silver nanoparticles (AgNPs) and silver acetate (AgAc) to rats. Oral administration is a relevant route of exposure because of the use of silver nanoparticles in products related to food and food contact materials. Results AgNPs were synthesized with a size distribution of 14 ± 4 nm in diameter (90% of the nanoparticle volume) and stabilized in aqueous suspension by the polymer polyvinylpyrrolidone (PVP). The AgNPs remained stable throughout the duration of the 28-day oral toxicity study in rats. The organ distribution pattern of silver following administration of AgNPs and AgAc was similar. However the absolute silver concentrations in tissues were lower following oral exposure to AgNPs. This was in agreement with an indication of a higher fecal excretion following administration of AgNPs. Besides the intestinal system, the largest silver concentrations were detected in the liver and kidneys. Silver was also found in the lungs and brain. Autometallographic (AMG) staining revealed a similar cellular localization of silver in ileum, liver, and kidney tissue in rats exposed to AgNPs or AgAc. Using transmission electron microscopy (TEM), nanosized granules were detected in the ileum of animals exposed to AgNPs or AgAc and were mainly located in the basal lamina of the ileal epithelium and in lysosomes of macrophages within the lamina propria. Using energy dispersive x-ray spectroscopy it was shown that the granules in lysosomes consisted of silver, selenium, and sulfur for both AgNP and AgAc exposed rats. The diameter of the deposited granules was in the same size range as that of the administered AgNPs. No silver granules were detected by TEM in the liver. Conclusions The results of the present study demonstrate that the organ distribution of silver was similar when AgNPs or AgAc were administered orally to rats. The presence of silver granules containing selenium and sulfur in the intestinal wall of rats exposed to either of the silver forms suggests a common mechanism of their formation. Additional studies however, are needed to gain further insight into the underlying mechanisms of the granule formation, and to clarify whether AgNPs dissolve in the gastrointestinal system and/or become absorbed and translocate as intact nanoparticles to organs and tissues. PMID:21631937

Polyimides Containing Silver Trifluoroacetylacetonate

NASA Technical Reports Server (NTRS)

Stoakley, Diane M.; St. Clair, Anne K.; Rancourt, James D.; Taylor, Larry T.; Caplan, Maggie L.

1994-01-01

Mechanically strong, flexible, thermally stable, electrically conductive films and coatings suitable for use in electronics industry made by incorporating silver trifluoroacetylacetonate into linear aromatic condensation polyimides. In experimental films, most successful combinations of flexibility and conductivity obtained by use of 1:1, 1:1.74, and 1:2 mole ratios of silver trifluoroacetylacetonate per polyimide repeat unit. Other concentrations of silver trifluoroacetylacetonate used with different heat-treatment schedules to obtain conductive silver-impregnated films.

Measurements of the optical properties of thin films of silver and silver oxide

NASA Technical Reports Server (NTRS)

Peters, Palmer N.; Sisk, Robert C.; Brown, Yolanda; Gregory, John C.; Nag, Pallob K.; Christl, Ligia

1995-01-01

The optical properties of silver films and their oxides are measured to better characterize such films for use as sensors for atomic oxygen. Good agreement between properties of measured pure silver films and reported optical constants is observed. Similar comparisons for silver oxide have not been possible because of a lack of reported constants, but self-consistencies and discrepancies in our measured results are described.

Silver ion bactericide system. [for Space Shuttle Orbiter potable water

NASA Technical Reports Server (NTRS)

Jasionowski, W. J.; Allen, E. T.

1974-01-01

Description of a preliminary flight prototype system which uses silver ions as the bactericide to preserve sterility of the water used for human consumption and hygiene in the Space Shuttle Orbiter. The performance of silver halide columns for passively dosing fuel cell water with silver ions is evaluated. Tests under simulated Orbiter mission conditions show that silver ion doses of 0.05 ppm are bactericidal for Pseudomonas aeruginosa and Type IIIa, the two bacteria found in Apollo potable water systems. The design of the Advance Prototype Silver Ion Water Bactericide System now under development is discussed.

Biomedical properties of laser prepared silver-doped hydroxyapatite

NASA Astrophysics Data System (ADS)

Jelínek, M.; Weiserová, M.; Kocourek, T.; Zezulová, M.; Strnad, J.

2011-07-01

Thin films of hydroxyapatite (HA) and silver-doped HA were synthesized using KrF excimer laser deposition. Material was ablated from one target composed from silver and HA segments. Layers properties as silver content, structure, color, FTIR spectra and antibacterial properties (Gram-positive Bacillus subtilis) were measured. Silver concentration in HA layers of 0.06, 0.3, 1.2, 4.4, 8.3, and 13.7 at % was detected. The antibacterial efficacy changed with silver dopation from 71.0 to 99.9%. The focus is on investigation of minimum Ag concentration needed to reach a high antibacterial efficacy.

Silver Hazards to Fish, Wildlife, and Invertebrates: A Synoptic Review

USGS Publications Warehouse

Eisler, R.

1996-01-01

Ecological and toxicological aspects of silver (Ag) in the environment are briefly summarized with an emphasis on natural resources. Elevated silver concentrations in biota occur in the vicinities of sewage outfalls, electroplating plants, mine waste sites, and silver-iodide seeded areas; in the United States, the photography industry is the major source of anthropogenic silver discharges into the biosphere. Silver and its compounds are not known to be mutagenic, teratogenic, or carcinogenic. Under normal routes of exposure, silver does not pose serious environmental health problems to humans at less than 50.0 ug total Ag/L drinking water or 10.0 ug per cubic meter air. Free silver ion, however, was lethal to representative species of sensitive aquatic plants, invertebrates, and teleosts at nominal water concentrations of 1.2 to 4.9 ug/L; sublethal effects were significant between 0.17 and 0.6 ug/L. Silver was harmful to poultry at concentrations as low as 1.8 mg total Ag/kg whole egg fresh weight by way of injection, 100.0 mg total Ag/L in drinking water, or 200.0 mg total Ag/kg in diets; sensitive mammals were adversely affected at total silver concentrations as low as 250.0 ug/L in drinking water, 6.0 mg/kg in diets, or 13.9 mg/kg whole body.

Comparative activity of silver based antimicrobial composites for urinary catheters.

PubMed

Thokala, Nikhil; Kealey, Carmel; Kennedy, James; Brady, Damien B; Farrell, Joseph

2018-04-04

Biomedical polymers are an integral component in a wide range of medical device designs due to their range of desirable properties. However, extensive use of polymer materials in medical devices have also been associated with an increasing incidence of patient infections. Efforts to address this issue have included the incorporation of antimicrobial additives for developing novel antimicrobial polymeric materials. Silver with its high toxicity towards bacteria, oligodynamic effect and good thermal stability has been employed as an additive for polymeric medical devices. In the present study, commercially available elemental (Biogate) and ionic (Ultrafresh 16) silver additives were incorporated into a Polyamide 11 (PA 11) matrix using a compression press. These polymer composites were evaluated for their antimicrobial and ion release properties. Elemental silver composites were determined to retain their antimicrobial properties for extended periods and actively release silver ions for 84 days; whereas the ionic silver composites lost their ion release activity and therefore antibacterial activity after 56 days. Bacterial log reduction units of 3.87 for ionic silver and 2.41 for elemental silver was identified within 24 hr, when tested in accordance with ISO 22196 test standard; indicating that ionic silver is more efficient for short-term applications compared to elemental silver. Copyright © 2018 Elsevier Ltd. All rights reserved.

Piper nigrum Leaf and Stem Assisted Green Synthesis of Silver Nanoparticles and Evaluation of Its Antibacterial Activity Against Agricultural Plant Pathogens

PubMed Central

Paulkumar, Kanniah; Gnanajobitha, Gnanadhas; Vanaja, Mahendran; Rajeshkumar, Shanmugam; Malarkodi, Chelladurai; Pandian, Kannaiyan; Annadurai, Gurusamy

2014-01-01

Utilization of biological materials in synthesis of nanoparticles is one of the hottest topics in modern nanoscience and nanotechnology. In the present investigation, the silver nanoparticles were synthesized by using the leaf and stem extract of Piper nigrum. The synthesized nanoparticle was characterized by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray analysis (EDAX), and Fourier Transform Infrared Spectroscopy (FTIR). The observation of the peak at 460 nm in the UV-vis spectra for leaf- and stem-synthesized silver nanoparticles reveals the reduction of silver metal ions into silver nanoparticles. Further, XRD analysis has been carried out to confirm the crystalline nature of the synthesized silver nanoparticles. The TEM images show that the leaf- and stem-synthesized silver nanoparticles were within the size of about 7–50 nm and 9–30 nm, respectively. The FTIR analysis was performed to identify the possible functional groups involved in the synthesis of silver nanoparticles. Further, the antibacterial activity of the green-synthesized silver nanoparticles was examined against agricultural plant pathogens. The antibacterial property of silver nanoparticles is a beneficial application in the field of agricultural nanotechnology. PMID:24558336

Silver Recovery and Power Generation from Ammonia Chelated Silver Solution in a Bio-Electrochemical Reactor

NASA Astrophysics Data System (ADS)

Ho, N. A. D.; Babel, S.

2017-06-01

Silver has valuable features and limited availability, and thus recovery from wastewater or aqueous solutions plays an important role in environmental protection and economic profits. In this study, silver recovery along with power generation and COD removal were investigated in a bio-electrochemical system (BES). The BES comprised of an anode and a cathode chamber which were separated by a cation exchange membrane to prevent the cross-over of electrolytes. During the biological oxidation of acetate as an electron donor in the anode chamber, the reduction of ammonia chelated silver ions as electron acceptors in the cathode side occurred spontaneously. Results showed that a silver recovery of 99% and COD removal efficiency of 60% were achieved at the initial silver concentration of 1,000 mg/L after 48 hours of operation. The power generation improved 4.66%, from 3,618 to 3,795 mW/m3, by adding NaNO3 of 850 mg/L to the catholyte containing 2,000 mg/L of silver ions. Deposits on the cathode surface were characterized using scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Metallic silver with dendritic structures and high purity were detected. This study demonstrated that BES technology can be employed to recover silver from complex chelating solution, produce electricity, and treat wastewater.

Concurrent In Vitro Release of Silver Sulfadiazine and Bupivacaine From Semi-Interpenetrating Networks for Wound Management

PubMed Central

Kleinbeck, Kyle R.; Bader, Rebecca A.; Kao, Weiyuan John

2013-01-01

In situ photopolymerized semi-interpenetrating networks (sIPNs) composed of poly(ethylene glycol) and gelatin are promising multifunctional matrices for a regenerative medicine approach to dermal wound treatment. In addition to previously demonstrated efficacy in critical defects, sIPNs also function as drug delivery matrices for compounds loaded as either soluble or covalently linked components. Simultaneous release of silver sulfadiazine and bupivacaine from the sIPN would provide multiple-hit management of dermal wounds that minimizes infection, and manages pain along with sIPN absorption of exudates and facilitation of epidermal regrowth. We characterized the release of soluble silver sulfadiazine and bupivacaine and compared it with an established release model. Efficacy of released silver sulfadiazine was confirmed in vitro on Staphylococcus aureus, methicillin resistant S. aureus, and Pseudomonas aeruginosa. Bupivacaine loaded without silver sulfadiazine showed incomplete release, whereas simultaneous loading with silver sulfadiazine facilitated 100% bupivacaine release. Silver sulfadiazine released at 98% without bupivacaine and 96% with bupivacaine. Silver sulfadiazine released onto bacterial cultures inhibited all three strains dose dependently. sIPNs effectively release bupivacaine and silver sulfadiazine while maintaining the antimicrobial activity of silver sulfadiazine. Drug loaded sIPNs have potential to improve wound management by providing multi-drug delivery along with an effective wound treatment. PMID:19060724

Surface-independent antibacterial coating using silver nanoparticle-generating engineered mussel glue.

PubMed

Jo, Yun Kee; Seo, Jeong Hyun; Choi, Bong-Hyuk; Kim, Bum Jin; Shin, Hwa Hui; Hwang, Byeong Hee; Cha, Hyung Joon

2014-11-26

During implant surgeries, antibacterial agents are needed to prevent bacterial infections, which can cause the formation of biofilms between implanted materials and tissue. Mussel adhesive proteins (MAPs) derived from marine mussels are bioadhesives that show strong adhesion and coating ability on various surfaces even in wet environment. Here, we proposed a novel surface-independent antibacterial coating strategy based on the fusion of MAP to a silver-binding peptide, which can synthesize silver nanoparticles having broad antibacterial activity. This sticky recombinant fusion protein enabled the efficient coating on target surface and the easy generation of silver nanoparticles on the coated-surface under mild condition. The biosynthesized silver nanoparticles showed excellent antibacterial efficacy against both Gram-positive and Gram-negative bacteria and also revealed good cytocompatibility with mammalian cells. In this coating strategy, MAP-silver binding peptide fusion proteins provide hybrid environment incorporating inorganic silver nanoparticle and simultaneously mediate the interaction of silver nanoparticle with surroundings. Moreover, the silver nanoparticles were fully synthesized on various surfaces including metal, plastic, and glass by a simple, surface-independent coating manner, and they were also successfully synthesized on a nanofiber surface fabricated by electrospinning of the fusion protein. Thus, this facile surface-independent silver nanoparticle-generating antibacterial coating has great potential to be used for the prevention of bacterial infection in diverse biomedical fields.

Multi-functional nano silver: A novel disruptive and theranostic agent for pathogenic organisms in real-time

PubMed Central

Gopinath, Ponnusamy Manogaran; Ranjani, Anandan; Dhanasekaran, Dharumadurai; Thajuddin, Nooruddin; Archunan, Govindaraju; Akbarsha, Mohammad Abdulkader; Gulyás, Balázs; Padmanabhan, Parasuraman

2016-01-01

The present study was aimed at evaluating the fluorescence property, sporicidal potency against Bacillus and Clostridium endospores, and surface disinfecting ability of biogenic nano silver. The nano silver was synthesized using an actinobacterial cell-filtrate. The fluorescence property as well as imaging facilitator potency of this nano silver was verified adopting spectrofluorometer along with fluorescent and confocal laser scanning microscope wherein strong emission and bright green fluorescence, respectively, on the entire spore surface was observed. Subsequently, the endospores of B. subtilis, B. cereus, B. amyloliquefaciens, C. perfringens and C. difficile were treated with physical sporicides, chemical sporicides and nano silver, in which the nano silver brought about pronounced inhibition even at a very low concentration. Finally, the environmental surface-sanitizing potency of nano silver was investigated adopting cage co-contamination assay, wherein vital organs of mice exposed to the nano silver-treated cage did not show any signs of pathological lesions, thus signifying the ability of nano silver to completely disinfect the spore or reduce the count required for infection. Taken these observations together, we have shown the multi-functional biological properties of the nano silver, synthesized using an actinobacterial cell-filtrate, which could be of application in advanced diagnostics, biomedical engineering and therapeutics in the near future. PMID:27666290

Evaluation of Osseous Integration of PVD-Silver-Coated Hip Prostheses in a Canine Model

PubMed Central

Hauschild, Gregor; Hardes, Jendrik; Gosheger, Georg; Blaske, Franziska; Wehe, Christoph; Karst, Uwe; Höll, Steffen

2015-01-01

Infection associated with biomaterials used for orthopedic prostheses remains a serious complication in orthopedics, especially tumor surgery. Silver-coating of orthopedic (mega)prostheses proved its efficiency in reducing infections but has been limited to surface areas exposed to soft tissues due to concerns of silver inhibiting osseous integration of cementless stems. To close this gap in the bactericidal capacity of silver-coated orthopedic prostheses extension of the silver-coating on surface areas intended for osseous integration seems to be inevitable. Our study reports about a PVD- (physical-vapor-deposition-) silver-coated cementless stem in a canine model for the first time and showed osseous integration of a silver-coated titanium surface in vivo. Radiological, histological, and biomechanical analysis revealed a stable osseous integration of four of nine stems implanted. Silver trace elemental concentrations in serum did not exceed 1.82 parts per billion (ppb) and can be considered as nontoxic. Changes in liver and kidney functions associated with the silver-coating could be excluded by blood chemistry analysis. This was in accordance with very limited metal displacement from coated surfaces observed by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) 12 months after implantation. In conclusion our results represent a step towards complete bactericidal silver-coating of orthopedic prostheses. PMID:25695057

Understanding long-term silver release from surface modified porous titanium implants.

PubMed

Shivaram, Anish; Bose, Susmita; Bandyopadhyay, Amit

2017-08-01

Prevention of orthopedic device related infection (ODRI) using antibiotics has met with limited amount of success and is still a big concern during post-surgery. As an alternative, use of silver as an antibiotic treatment to prevent surgical infections is being used due to the well-established antimicrobial properties of silver. However, in most cases silver is used in particulate form with wound dressings or with short-term devices such as catheters but not with load-bearing implants. We hypothesize that strongly adherent silver to load-bearing implants can offer longer term solution to infection in vivo. Keeping that in mind, the focus of this study was to understand the long term release study of silver ions for a period of minimum 6months from silver coated surface modified porous titanium implants. Implants were fabricated using a LENS™ system, a powder based additive manufacturing technique, with at least 25% volume porosity, with and without TiO 2 nanotubes in phosphate buffer saline (pH 7.4) to see if the total release of silver ions is within the toxic limit for human cells. Considering the fact that infection sites may reduce the local pH, silver release was also studied in acetate buffer (pH 5.0) for a period of 4weeks. Along with that, the osseointegrative properties as well as cytotoxicity of porous titanium implants were assessed in vivo for a period of 12weeks using a rat distal femur model. In vivo results indicate that porous titanium implants with silver coating show comparable, if not better, biocompatibility and bonding at the bone-implant interface negating any concerns related to toxicity related to silver to normal cells. The current research is based on our recently patented technology, however focused on understanding longer-term silver release to mitigate infection related problems in load-bearing implants that can even arise several months after the surgery. Prevention of orthopedic device related infection using antibiotics has met with limited success and is still a big concern during post-surgery. Use of silver as an antibiotic treatment to prevent surgical infections is being explored due to the well-established antimicrobial properties of silver. However, in most cases silver is used in particulate form with wound dressings or with short-term devices such as catheters but not with load-bearing implants. We hypothesize that strongly adherent silver to load-bearing implants can offer longer-term solution towards infection in vivo. Keeping that in mind, the focus of this study was to understand the long-term release of silver ions, for a period of minimum 6months, from silver coated surface modified porous titanium implants. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Comparative toxicity of silver nanoparticles and silver ions to Escherichia coli.

PubMed

Choi, Yoojin; Kim, Hyun-A; Kim, Kyoung-Woong; Lee, Byung-Tae

2018-04-01

With the increase in silver (Ag)-based products in our lives, it is essential to test the potential toxicity of silver nanoparticles (AgNPs) and silver ions (Ag ions) on living organisms under various conditions. Here, we investigated the toxicity of AgNPs with Ag ions to Escherichia coli K-12 strain under various conditions. We observed that both AgNPs and Ag ions display antibacterial activities, and that Ag ions had higher toxicity to E. coli K-12 strain than AgNPs under the same concentrations. To understand the toxicity of AgNPs at a cellular level, reactive oxygen species (ROS) enzymes were detected for use as antioxidant enzymatic biomarkers. We have also studied the toxicity of AgNPs and Ag ions under various coexistence conditions including: fixed total concentration, with a varied the ratio of AgNPs to Ag ions; fixed the AgNPs concentration and then increased the Ag ions concentration; fixed Ag ions concentration and then increasing the AgNPs concentration. Exposure to AgNPs and Ag ions clearly had synergistic toxicity; however, decreased toxicity (for a fixed AgNPs concentration of 5mg/L, after increasing the Ag ions concentration) to E. coli K-12 strain. AgNPs and Ag ions in the presence of L-cysteine accelerated the bacterial cell growth rate, thereby reducing the bioavailability of Ag ions released from AgNPs under the single and coexistence conditions. Further works are needed to consider this potential for AgNPs and Ag ions toxicity across a range of environmental conditions. As silver nanoparticles (AgNPs)-based products are being broadly used in commercial industries, an ecotoxicological understanding of the AgNPs being released into the environment should be further considered. Here, we investigate the comparative toxicity of AgNPs and silver ions (Ag ions) to Escherichia coli K-12 strain, a representative ecotoxicological bioreporter. This study showed that toxicities of AgNPs and Ag ions to E. coli K-12 strain display different relationships when existing individually or when coexisting, and in the presence of L-cysteine materials. These findings suggest that the toxicology research of nanomaterials should consider conditions when NPs coexist with and without their bioavailable ions. Copyright © 2017. Published by Elsevier B.V.

Highly surface-roughened quasi-spherical silver powders in back electrode paste for silicon solar cells

NASA Astrophysics Data System (ADS)

Yin, Peng; Liu, Shouchao; Li, Qiuying; Chen, Xiaolei; Guo, Weihong; Wu, Chifei

2017-08-01

In our work, highly surface-roughened quasi-spherical silver powders with controllable size and superior dispersibility, which have narrow size distribution and relatively high tap density, were successfully prepared by reducing silver nitrate with ascorbic acid in aqueous solutions. Gum arabic (AG) was selected as dispersant to prevent the agglomeration of silver particles. Furthermore, the effects of preparation conditions on the characteristics of the powders were systematically investigated. By varying the concentration of the reactants, dosage of dispersant, the feeding modes, synthesis temperature and the pH value of the mixture solution of silver nitrate and AG, the resulted silver particles displayed controllable size, different morphologies and surface roughness. The spherical silver powder with mean particle size of 1.20 µm, tap density of 4.1 g cm-3 and specific area value of 0.46 m2 g-1 was prepared by adjusting preparation conditions. The AG absorbed on the surface preventing the silver particles from diffusion and aggregation was proved by the ultraviolet spectra. Observations of SEM images showed that the as-prepared silver powders were relatively monodisperse silver spheres with highly roughened surface and the particle size was controllable from 1 µm to 5 µm, specific surface area value from approximately 0.2 m2 g-1 to 0.8 m2 g-1. X-ray diffraction (XRD) patterns, energy dispersive spectroscopy (EDS), x-ray photoelectron spectra (XPS) and thermal gravity analysis (TGA) demonstrated high crystallinity and purity of the obtained silver powders.

Characterization of Electrochemically Generated Silver

NASA Technical Reports Server (NTRS)

Adam, Niklas; Martinez, James; Carrier, Chris

2014-01-01

Silver biocide offers a potential advantage over iodine, the current state of the art in US spacecraft disinfection technology, in that silver can be safely consumed by the crew. Low concentrations of silver (<500 ppb) have been shown to kill bacteria in water systems and keep it safe for potability. Silver does not require hardware to remove it from a water system, and therefore can provide a simpler means for disinfecting water. The Russian segment of the International Space Station has utilized an electrochemically generated silver solution, which is colloidal in nature. To be able to reliably provide a silver biocide to drinking water by electrochemical means would reduce mass required for removing another biocide such as iodine from the water. This would also aid in crew time required to replace iodine removal cartridges. Future long term missions would benefit from electrochemically produced silver as the biocide could be produced on demand and requires only a small concentration to be effective. Since it can also be consumed safely, there is less mass in removal hardware and little consumables required for production. The goal of this project initially is to understand the nature of the electrochemically produced silver, the particle sizes produced by the electrochemical cell and the effect that voltage adjustment has on the particle size. In literature, it has been documented that dissolved oxygen and pH have an effect on the ionization of the electrochemical silver so those parameters would be measured and possibly adjusted to understand their effect on the silver.

Printing Silver Nanogrids on Glass

ERIC Educational Resources Information Center

Sanders, Wesley C.; Valcarce, Ron; Iles, Peter; Smith, James S.; Glass, Gabe; Gomez, Jesus; Johnson, Glen; Johnston, Dan; Morham, Maclaine; Befus, Elliot; Oz, Aimee; Tomaraei, Mohammad

2017-01-01

This manuscript describes a laboratory experiment that provides students with an opportunity to create conductive silver nanogrids using polymeric templates. A microcontact-printed polyvinylpyrrolidone grid directs the citrate-induced reduction of silver ions for the fabrication of silver nanogrids on glass substrates. In addition to…

Absorbent silver (I) antimicrobial fabrics

USDA-ARS?s Scientific Manuscript database

In recent years, silver in form of silver ions, has been gaining importance in the wound management as an effective broad-spectrum antimicrobial agent. Silver has a long history as an antimicrobial agent, especially in the treatment of wounds. Alginates and carboxymethyl (CM) cotton contain carboxyl...

A comparative study of plaque mutans streptococci levels in children receiving glass ionomer cement and amalgam restorations.

PubMed

Ertuğrul, Fahinur; Eltem, Rengin; Eronat, Cemal

2003-01-01

The restorative materials amalgam (Standalloy F) and glass ionomer cements (Chelon Silver) were comparatively investigated to determine the number of mutans streptococci Saliva and plaque were collected from patients before and 40 days after the insertion of their restorations. Total bateria and mutans streptococci counts were found to be statistically significantly reduced when compared with the prerestoration counts in the saliva samples (P<0.001). Microbiological analysis of the dental plaque showed that the number of mutans streptococci in the glass ionomer cements was significantly lower than in the amalgam restorations (P<0.001). This study showed that silver glass ionomer cements inhibited the growth of mutans streptococci.

Ultrafast coherence transfer in DNA-templated silver nanoclusters

PubMed Central

Thyrhaug, Erling; Bogh, Sidsel Ammitzbøll; Carro-Temboury, Miguel R; Madsen, Charlotte Stahl; Vosch, Tom; Zigmantas, Donatas

2017-01-01

DNA-templated silver nanoclusters of a few tens of atoms or less have come into prominence over the last several years due to very strong absorption and efficient emission. Applications in microscopy and sensing have already been realized, however little is known about the excited-state structure and dynamics in these clusters. Here we report on a multidimensional spectroscopy investigation of the energy-level structure and the early-time relaxation cascade, which eventually results in the population of an emitting state. We find that the ultrafast intramolecular relaxation is strongly coupled to a specific vibrational mode, resulting in the concerted transfer of population and coherence between excited states on a sub-100 fs timescale. PMID:28548085

Ultralight Conductive Silver Nanowire Aerogels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, Fang; Lan, Pui Ching; Freyman, Megan C.

Low-density metal foams have many potential applications in electronics, energy storage, catalytic supports, fuel cells, sensors, and medical devices. Here in this work, we report a new method for fabricating ultralight, conductive silver aerogel monoliths with predictable densities using silver nanowires. Silver nanowire building blocks were prepared by polyol synthesis and purified by selective precipitation. Silver aerogels were produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to weld the nanowire junctions. As-prepared silver aerogels have unique anisotropic microporous structures, with density precisely controlled by the nanowire concentration, down to 4.8 mg/cm 3 and an electrical conductivity up tomore » 51 000 S/m. Lastly, mechanical studies show that silver nanowire aerogels exhibit “elastic stiffening” behavior with a Young’s modulus up to 16 800 Pa.« less

In situ reduction of antibacterial silver ions to metallic silver nanoparticles on bioactive glasses functionalized with polyphenols

NASA Astrophysics Data System (ADS)

Ferraris, S.; Miola, M.; Cochis, A.; Azzimonti, B.; Rimondini, L.; Prenesti, E.; Vernè, E.

2017-02-01

The realization of surfaces with antibacterial properties due to silver nanoparticles loaded through a green approach is a promising research challenge of the biomaterial field. In this research work, two bioactive glasses have been doubly surface functionalized with polyphenols (gallic acid or natural polyphenols extracted from red grape skins and green tea leaves) and silver nanoparticles deposited by in situ reduction from a silver nitrate aqueous solution. The presence of biomolecules - showing reducing ability to directly obtain in situ metallic silver - and silver nanoparticles was investigated by means of UV-vis spectroscopy, X-Ray Photoelectron Spectroscopy (XPS) and Field Emission Scanning Electron Microscopy (FESEM). The antibacterial activity of the modified surfaces was tested against a multidrug resistant Staphylococcus aureus bacterial strain.

Enhanced photoluminescence of Alq3 via patterned array silver dendritic nanostructures

NASA Astrophysics Data System (ADS)

Hsu, Wei-Hsiu; Hsieh, Ming-Hao; Lo, Shih-Shou

2012-04-01

Various silver nanostructures, semi-ball, jungle, and dendritic, are demonstrated by an electrical deposition process. The formation of silver nanostructures with various morphologies is studied by the mechanism of the diffusion limited aggregation (DLA) model. A array pattern of silver nanostructures can be obtained when the conductive substrate was used in a uniform electrical filed. A thickness 500 nm of Alq3 thin-film was covered on the silver nanostructure by thermal evaporation method. The strongest intensity of Alq3 green emission was observed when the pattern-array dendritic silver nanostructure was covered by Alq3. It can be explained with the plasmonic coupling due to the Alq3 and dendritic nanostructure. The result can help us to further application the patterned-array silver dendritic nanostructure for advanced opto-electronic device.

Ultralight Conductive Silver Nanowire Aerogels

DOE PAGES

Qian, Fang; Lan, Pui Ching; Freyman, Megan C.; ...

2017-09-05

Low-density metal foams have many potential applications in electronics, energy storage, catalytic supports, fuel cells, sensors, and medical devices. Here in this work, we report a new method for fabricating ultralight, conductive silver aerogel monoliths with predictable densities using silver nanowires. Silver nanowire building blocks were prepared by polyol synthesis and purified by selective precipitation. Silver aerogels were produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to weld the nanowire junctions. As-prepared silver aerogels have unique anisotropic microporous structures, with density precisely controlled by the nanowire concentration, down to 4.8 mg/cm 3 and an electrical conductivity up tomore » 51 000 S/m. Lastly, mechanical studies show that silver nanowire aerogels exhibit “elastic stiffening” behavior with a Young’s modulus up to 16 800 Pa.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mendoza-Lopez, M.L.; Centro de Fisica Aplicada y Tecnologia Avanzada, Departamento de Nanotecnologia, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Apdo. Postal 1-1010, Queretaro Qro. C.P. 76230; Perez-Bueno, J.J.

This paper presents a complete methodology for the characterization of silver alloys used in modern coin production. Mexican coins with a nominal silver concentration from 10% to 99.99% were used in this study. Calibrated Glow Discharge Optical Emission Spectrometers were used to determine the chemical composition of the alloys as a function of the depth, while inductively coupled plasma was used to determine the total element composition in bulk. Scanning Electron Microscope was used to study the phase distributions in the different silver coins. According to Glow Discharge Optical Emission Spectrometers and inductively coupled plasma, the silver content found inmore » the studied samples was consistently greater than that of the nominal silver content reported by the Mexican mint. This may lead to a review of the new methods of analysis used nowadays in contemporary coin minting. This result is very important because silver is increasing in value as metal and, considering the volume of production of silver coins, this may increase further as a consequence of a growing popular confidence in silver currency. In the case of silver studies, an advantage of the absence of silver detector in the Glow Discharge Optical Emission Spectrometers system is that it allows for the recalibration to have a better range of detection of other metals present in the alloys. A calibration curve using the copper content obtained by inductively coupled plasma (bulk) and Glow Discharge Optical Emission Spectrometers (depth profile) was performed. The relevance of control in modern silver coin minting was clarified, especially in minimizing the discrepancy between the nominal and the core fineness. The physical and chemical properties of the alloys studied are defined, revealing important variations in silver and copper contents. A new methodology and metrology for the control of coinage are suggested.« less

Simulation of the shallow aquifer in the vicinity of Silver Lake, Washington County, Wisconsin, using analytic elements

USGS Publications Warehouse

Dunning, C.P.; Thomas, Judith Coffman; Lin, Yu-Feng

2003-01-01

A Silver Lake water budget was defined using both published hydrologic data and simulations using the calibrated model. Model simulations show that 1.08 cubic feet per second of ground water enters Silver Lake on the upgradient (primarily western) side and 0.08 cubic feet per second recharges to ground water on the downgradient (primarily eastern) side. Net precipitation (precipitation minus evaporation) on the lake is 0.04 cubic feet per second. Collectively, these water-budget terms provide a residual value of 1.04 cubic feet per second flow to Silver Creek at the north end of Silver Lake, which is a very good match to the range of measured flow (0.7 to 5.2 cubic feet per second). Ground-water recharge areas for Silver Lake are largely on the western side of the lake. The recharge area for the northern two-thirds of Silver Lake is west toward Big Cedar Lake. Assuming a porosity of 20 percent, model results indicate that the 50-year time-of-travel for recharge to Silver Lake does not extend to Big Cedar Lake. The recharge area for the southern one-third of Silver Lake is west toward Little Cedar Lake. Model results indicate that time of travel for recharge to Silver Lake from Little Cedar Lake is about 15 to 20 years. For travel times greater than 15 or 20 years, the ground-water recharge area for Little Cedar Lake and inflow from Big Cedar Lake also should be considered recharge affecting Silver Lake. Solute flux toward Silver Lake was calculated based on simulated ground-water flux and measured concentrations in the upgradient piezometers and observation wells.

High frequency of silver resistance genes in invasive isolates of Enterobacter and Klebsiella species.

PubMed

Sütterlin, S; Dahlö, M; Tellgren-Roth, C; Schaal, W; Melhus, Å

2017-07-01

Silver-based products have been marketed as an alternative to antibiotics, and their consumption has increased. Bacteria may, however, develop resistance to silver. To study the presence of genes encoding silver resistance (silE, silP, silS) over time in three clinically important Enterobacteriaceae genera. Using polymerase chain reaction (PCR), 752 bloodstream isolates from the years 1990-2010 were investigated. Age, gender, and ward of patients were registered, and the susceptibility to antibiotics and silver nitrate was tested. Clonality and single nucleotide polymorphism were assessed with repetitive element sequence-based PCR, multi-locus sequence typing, and whole-genome sequencing. Genes encoding silver resistance were detected most frequently in Enterobacter spp. (48%), followed by Klebsiella spp. (41%) and Escherichia coli 4%. Phenotypical resistance to silver nitrate was found in Enterobacter (13%) and Klebsiella (3%) isolates. The lowest carriage rate of sil genes was observed in blood isolates from the neonatology ward (24%), and the highest in blood isolates from the oncology/haematology wards (66%). Presence of sil genes was observed in international high-risk clones. Sequences of the sil and pco clusters indicated that a single mutational event in the silS gene could have caused the phenotypic resistance. Despite a restricted consumption of silver-based products in Swedish health care, silver resistance genes are widely represented in clinical isolates of Enterobacter and Klebsiella species. To avoid further selection and spread of silver-resistant bacteria with a high potential for healthcare-associated infections, the use of silver-based products needs to be controlled and the silver resistance monitored. Copyright © 2017 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

Ageing of plasma-mediated coatings with embedded silver nanoparticles on stainless steel: An XPS and ToF-SIMS investigation

NASA Astrophysics Data System (ADS)

Zanna, S.; Saulou, C.; Mercier-Bonin, M.; Despax, B.; Raynaud, P.; Seyeux, A.; Marcus, P.

2010-09-01

Nanocomposite thin films (˜170 nm), composed of silver nanoparticles enclosed in an organosilicon matrix, were deposited onto stainless steel, with the aim of preventing biofilm formation. The film deposition was carried out under cold plasma conditions, combining radiofrequency (RF) glow discharge fed with argon and hexamethyldisiloxane and simultaneous silver sputtering. XPS and ToF-SIMS were used to characterize Ag-organosilicon films in native form and after ageing in saline solution (NaCl 0.15 M), in order to further correlate their lifetime with their anti-fouling properties. Two coatings with significantly different silver contents (7.5% and 20.3%) were tested. Surface analysis confirmed the presence of metallic silver in the pristine coating and revealed significant modifications after immersion in the saline solution. Two different ageing mechanisms were observed, depending on the initial silver concentration in the film. For the sample exhibiting the low silver content (7.5%), the metal amount decreased at the surface in contact with the solution, due to the release of silver from the coating. As a result, after a 2-day exposure, silver nanoparticles located at the extreme surface were entirely released, whereas silver is still present in the inner part of the film. The coating thickness was not modified during ageing. In contrast, for the high silver content film (20.3%), the thickness decreased with immersion time, due to significant silver release and matrix erosion, assigned to a percolation-like effect. However, after 18 days of immersion, the delamination process stopped and a thin strongly bounded layer remained on the stainless steel surface.

Ethylene Receptor 1 (ETR1) Is Sufficient and Has the Predominant Role in Mediating Inhibition of Ethylene Responses by Silver in Arabidopsis thaliana*

PubMed Central

McDaniel, Brittany K.; Binder, Brad M.

2012-01-01

Ethylene influences many processes in Arabidopsis thaliana through the action of five receptor isoforms. All five isoforms use copper as a cofactor for binding ethylene. Previous research showed that silver can substitute for copper as a cofactor for ethylene binding activity in the ETR1 ethylene receptor yet also inhibit ethylene responses in plants. End-point and rapid kinetic analyses of dark-grown seedling growth revealed that the effects of silver are mostly dependent upon ETR1, and ETR1 alone is sufficient for the effects of silver. Ethylene responses in etr1-6 etr2-3 ein4-4 triple mutants were not blocked by silver. Transformation of these triple mutants with cDNA for each receptor isoform under the promoter control of ETR1 revealed that the cETR1 transgene completely rescued responses to silver while the cETR2 transgene failed to rescue these responses. The other three isoforms partially rescued responses to silver. Ethylene binding assays on the binding domains of the five receptor isoforms expressed in yeast showed that silver supports ethylene binding to ETR1 and ERS1 but not the other isoforms. Thus, silver may have an effect on ethylene signaling outside of the ethylene binding pocket of the receptors. Ethylene binding to ETR1 with silver was ∼30% of binding with copper. However, alterations in the Kd for ethylene binding to ETR1 and the half-time of ethylene dissociation from ETR1 do not underlie this lower binding. Thus, it is likely that the lower ethylene binding activity of ETR1 with silver is due to fewer ethylene binding sites generated with silver versus copper. PMID:22692214

Influence of Particle Size on Persistence and Clearance of Aerosolized Silver Nanoparticles in the Rat Lung

PubMed Central

Anderson, Donald S.; Patchin, Esther S.; Silva, Rona M.; Uyeminami, Dale L.; Sharmah, Arjun; Guo, Ting; Das, Gautom K.; Brown, Jared M.; Shannahan, Jonathan; Gordon, Terry; Chen, Lung Chi; Pinkerton, Kent E.; Van Winkle, Laura S.

2015-01-01

The growing use of silver nanoparticles (AgNPs) in consumer products raises concerns about potential health effects. This study investigated the persistence and clearance of 2 different size AgNPs (20 and 110 nm) delivered to rats by single nose-only aerosol exposures (6 h) of 7.2 and 5.4 mg/m3, respectively. Rat lung tissue was assessed for silver accumulations using inductively-coupled plasma mass spectrometry (ICP-MS), autometallography, and enhanced dark field microscopy. Involvement of tissue macrophages was assessed by scoring of silver staining in bronchoalveolar lavage fluid (BALF). Silver was abundant in most macrophages at 1 day post-exposure. The group exposed to 20 nm AgNP had the greatest number of silver positive BALF macrophages at 56 days post-exposure. While there was a significant decrease in the amount of silver in lung tissue at 56 days post-exposure compared with 1 day following exposure, at least 33% of the initial delivered dose was still present for both AgNPs. Regardless of particle size, silver was predominantly localized within the terminal bronchial/alveolar duct junction region of the lung associated with extracellular matrix and within epithelial cells. Inhalation of both 20 and 110 nm AgNPs resulted in a persistence of silver in the lung at 56 days post-exposure and local deposition as well as accumulation of silver at the terminal bronchiole alveolar duct junction. Further the smaller particles, 20 nm AgNP, produced a greater silver burden in BALF macrophages as well as greater persistence of silver positive macrophages at later timepoints (21 and 56 days). PMID:25577195

Preparation and in vitro antimicrobial activity of silver-bearing degradable polymeric nanoparticles of polyphosphoester-block-poly(L-lactide).

PubMed

Lim, Young H; Tiemann, Kristin M; Heo, Gyu Seong; Wagers, Patrick O; Rezenom, Yohannes H; Zhang, Shiyi; Zhang, Fuwu; Youngs, Wiley J; Hunstad, David A; Wooley, Karen L

2015-02-24

The development of well-defined polymeric nanoparticles (NPs) as delivery carriers for antimicrobials targeting human infectious diseases requires rational design of the polymer template, an efficient synthetic approach, and fundamental understanding of the developed NPs, e.g., drug loading/release, particle stability, and other characteristics. Herein, we developed and evaluated the in vitro antimicrobial activity of silver-bearing, fully biodegradable and functional polymeric NPs. A series of degradable polymeric nanoparticles (dNPs), composed of phosphoester and L-lactide and designed specifically for silver loading into the hydrophilic shell and/or the hydrophobic core, were prepared as potential delivery carriers for three different types of silver-based antimicrobials-silver acetate or one of two silver carbene complexes (SCCs). Silver-loading capacities of the dNPs were not influenced by the hydrophilic block chain length, loading site (i.e., core or shell), or type of silver compound, but optimization of the silver feed ratio was crucial to maximize the silver loading capacity of dNPs, up to ca. 12% (w/w). The release kinetics of silver-bearing dNPs revealed 50% release at ca. 2.5-5.5 h depending on the type of silver compound. In addition, we undertook a comprehensive evaluation of the rates of hydrolytic or enzymatic degradability and performed structural characterization of the degradation products. Interestingly, packaging of the SCCs in the dNP-based delivery system improved minimum inhibitory concentrations up to 70%, compared with the SCCs alone, as measured in vitro against 10 contemporary epidemic strains of Staphylococcus aureus and eight uropathogenic strains of Escherichia coli. We conclude that these dNP-based delivery systems may be beneficial for direct epithelial treatment and/or prevention of ubiquitous bacterial infections, including those of the skin and urinary tract.

Potentiometric titration of thiols, cationic surfactants and halides using a solid-state silver-silver sulphide electrode.

PubMed

Pinzauti, S; Papeschi, G; La Porta, E

1983-01-01

A rugged, low resistance silver-silver sulphide solid-state electrode for determining pharmaceuticals as authentic samples or in dosage forms by potentiometric titration is described. Sodium tetraphenylborate, mercury(II) acetate and silver nitrate (0.01) M were employed as titrants in the analysis of cationic surfactants (cetylpyridinium chloride, benzethonium chloride, benzalkonium chloride and chlorhexidine salts), antithyroid drugs (methimazole and propylthiouracil) or sodium halides respectively.

Cytotoxic effects of nanosilver are highly dependent on the chloride concentration and the presence of organic compounds in the cell culture media.

PubMed

Kaiser, Jean-Pierre; Roesslein, Matthias; Diener, Liliane; Wichser, Adrian; Nowack, Bernd; Wick, Peter

2017-01-06

Nanosilver shows great promise for use in industrial, consumer or medical products because of its antimicrobial properties. However, the underlying mechanisms of the effects of silver nanoparticles on human cells are still controversial. Therefore, in the present study the influence of the chloride concentration and different serum content of culture media on the cytotoxic effects of nanosilver was systematically evaluated. Our results show that nanosilver toxicity was strongly affected by the composition of the culture media. The chloride concentration, as well as the carbon content affected the silver agglomeration and the complex formation. But also the dissolution of nanosilver and the availability of free silver ions (Ag + ) were severely affected by the compositions of the culture media. Cells, only exposed to silver particles in suspension and dissolved silver complexes, did not show any effects under all conditions. Nanosilver agglomerates and silver complexes were not very soluble. Thus, cells growing on the bottom of the culture dishes were exposed to sedimented nanosilver agglomerates and precipitated silver complexes. Locally, the concentration of silver on the cell surface was very high, much higher compared the silver concentration in the bulk solution. The cytotoxic effects of nanosilver are therefore a combination of precipitated silver complexes and organic silver compounds rather than free silver ions. Silver coatings are used in health care products due to their bacteriostatic or antibacterial properties. The assessment of the toxicity of a certain compound is mostly done using in vitro assays. Therefore, cytotoxicity studies of nanosilver using human cell cultures have to be undertaken under well controlled and understood cultivations conditions in order to improve the compatibility of different studies. Especially when eukaryotic versus prokaryotic systems are compared for the evaluation of the use of nanosilver as antibacterial coatings for implants in order to prevent bacterial colonization.

The effect of nano-silver packaging in increasing the shelf life of nuts: An in vitro model

PubMed Central

Tavakoli, Hamidreza; Rastegar, Hossein; Taherian, Mahdi; Samadi, Mohammad; Rostami, Hossein

2017-01-01

Nano packaging is currently one of the most important topics in food packaging technologies. The aim of the application of this technology in food packaging is increasing shelf life of foods by preventing internal and external corruption and microbial contaminations. Use of silver nanoparticles in food packaging has recently attracted much attention. The aim of this study was to investigate the effect of nano-silver packaging in increasing the shelf life packages of nuts in an In vitro model. In this experimental study, the effects of different nano-silver concentrations (0, 1, 2 and 3 percent) on biological and chemical properties of 432 samples of nuts including walnuts, hazelnuts, almonds and pistachios were evaluated during 0, 3, 6, 9, 12, 15, 18, 21 and 24 months. In most samples, different concentrations of nano-silver (1, 2 and 3 %) significantly reduced total microbial count, mold and coliform counts compared to control group and the 3% nano-silver concentration was more effective than other concentrations (P<0.05). Moreover, using this packaging yielded an antioxidant effect especially when 2% and 3% nano-silver concentrations were used. Nano-silver also prevented growth of mold and so prevented aflatoxin production in all treatment groups. Results of chemical and biological tests showed that the silver nanoparticles had a significant effect on increasing the shelf life of nuts. The highest shelf life belonged to pistachios, almonds, hazelnuts and walnuts with 20, 19, 18 and 18 months, respectively. The shelf life was associated with amount of silver nanoparticles. The highest antimicrobial activity was observed when 3% nano-silver concentration was used in pistachios. The shelf life of control groups in similar storage conditions were calculated for an average of 13 months. In conclusion, the results of this study demonstrate the efficacy of nano-silver packing in increasing shelf life of nuts. Hence, use of nano-silver packaging in food industry, especially in food packaging is recommended. PMID:29564232

The effect of nano-silver packaging in increasing the shelf life of nuts: An in vitro model.

PubMed

Tavakoli, Hamidreza; Rastegar, Hossein; Taherian, Mahdi; Samadi, Mohammad; Rostami, Hossein

2017-10-20

Nano packaging is currently one of the most important topics in food packaging technologies. The aim of the application of this technology in food packaging is increasing shelf life of foods by preventing internal and external corruption and microbial contaminations. Use of silver nanoparticles in food packaging has recently attracted much attention. The aim of this study was to investigate the effect of nano-silver packaging in increasing the shelf life packages of nuts in an In vitro model. In this experimental study, the effects of different nano-silver concentrations (0, 1, 2 and 3 percent) on biological and chemical properties of 432 samples of nuts including walnuts, hazelnuts, almonds and pistachios were evaluated during 0, 3, 6, 9, 12, 15, 18, 21 and 24 months. In most samples, different concentrations of nano-silver (1, 2 and 3 %) significantly reduced total microbial count, mold and coliform counts compared to control group and the 3% nano-silver concentration was more effective than other concentrations (P<0.05). Moreover, using this packaging yielded an antioxidant effect especially when 2% and 3% nano-silver concentrations were used. Nano-silver also prevented growth of mold and so prevented aflatoxin production in all treatment groups. Results of chemical and biological tests showed that the silver nanoparticles had a significant effect on increasing the shelf life of nuts. The highest shelf life belonged to pistachios, almonds, hazelnuts and walnuts with 20, 19, 18 and 18 months, respectively. The shelf life was associated with amount of silver nanoparticles. The highest antimicrobial activity was observed when 3% nano-silver concentration was used in pistachios. The shelf life of control groups in similar storage conditions were calculated for an average of 13 months. In conclusion, the results of this study demonstrate the efficacy of nano-silver packing in increasing shelf life of nuts. Hence, use of nano-silver packaging in food industry, especially in food packaging is recommended.

Toxicogenomic responses of nanotoxicity in Daphnia magna exposed to silver nitrate and coated silver nanoparticles

EPA Science Inventory

Applications for silver nanomaterials in consumer products are rapidly expanding, creating an urgent need for toxicological examination of the exposure potential and ecological effects of silver nanoparticles (AgNPs). The integration of genomic techniques into environmental toxic...

Green synthesis of silver nanoparticles using a Melissa officinalis leaf extract with antibacterial properties

NASA Astrophysics Data System (ADS)

de Jesús Ruíz-Baltazar, Álvaro; Reyes-López, Simón Yobbany; Larrañaga, Daniel; Estévez, Miriam; Pérez, Ramiro

The exceptional properties of the silver nanoparticles offer several applications in the biomedicine field. The development of antibiotics which are clinically useful against bacteria and drug resistant microorganisms, it is one of the main approaches of silver nanoparticles. However, it is necessary to develop environmentally friendly methods for their synthesis. In this sense, the main objective of this work is focused on to propose a simplified and efficient green synthesis of silver nanoparticles with proven antibacterial properties. The green synthesis route is based on the use of the Melissa officinalis as reducing agent of the silver ions in aqueous solution at room temperature. Complementary, the antibacterial activity of the silver nanoparticles against Staphylococcus aureus and Escherichia coli was confirmed. The silver nanoparticles obtained were characterized by transmission electron microscopy, X-ray diffraction, UV-vis, Raman and FT-IR spectroscopy. The observed results suggested that using Melissa officinalis, it is possible to performed silver nanoparticles with controlled characteristics and with significant inhibitory activity against the Staphylococcus aureus and Escherichia coli.

Spectroscopic study of surface enhanced Raman scattering of caffeine on borohydride-reduced silver colloids

NASA Astrophysics Data System (ADS)

Chen, Xiaomin; Gu, Huaimin; Shen, Gaoshan; Dong, Xiao; Kang, Jian

2010-06-01

The surface enhanced Raman scattering (SERS) of caffeine on borohydride-reduced silver colloids system under different aqueous solution environment has been studied in this paper. The relative intensity of SERS of caffeine significantly varies with different concentrations of sodium chloride and silver particles. However, at too high or too low concentration of sodium chloride and silver particle, the enhancement of SERS spectra is not evident. The SERS spectra of caffeine suggest that the contribution of the charge transfer mechanism to SERS may be dominant. The chloride ions can significantly enhance the efficiency of SERS, while the enhancement is selective, as the efficiency in charge transfer enhancement is higher than in electromagnetic enhancement. Therefore, it can be concluded that the active site of chloride ion locates on the bond between the caffeine and the silver surface. In addition, the SERS spectra of caffeine on borohydride-reduced and citrate-reduced silver colloids are different, which may be due to different states caffeine adsorbed on silver surface under different silver colloids.

Enhancement of the stability of silver nanoparticles synthesized using aqueous extract of Diospyros discolor Willd. leaves using polyvinyl alcohol

NASA Astrophysics Data System (ADS)

Ardani, H. K.; Imawan, C.; Handayani, W.; Djuhana, D.; Harmoko, A.; Fauzia, V.

2017-04-01

Biosynthesis of silver nanoparticles is recently attracting considerable attention because of it reduces the environmental impact and already used in numerous applications. However, the disadvantages such as easy aggregation and instability properties, prevent its’ application. In this papers, biosynthesis of silver nanoparticles using aqueous extract of Diospyros discolor Willd. leaves have been prepared. The effect of biosynthesis variables, like ratio of reactants and reduction time on the particle size distribution, stability, and morphology of the silver nanoparticles were investigated. The resulted silver nanoparticles were characterized using UV spectroscopy, Transmission Electron Microscopy, and Particles Size Analyzer. Polyvinyl alcohol (PVA) was used to enhance the stability of the silver nanoparticles. Silver nanoparticles modification with 1% PVA concentration has produced a better characteristic of particle size distribution compared to the original silver nanoparticles, from highly polydisperse into moderately disperse. The results of the Zetta potential measurement also confirmed the increase stability of cluster distribution in the colloidal Ag/PVA compared to the original Ag.

Electroless silver coating of rod-like glass particles.

PubMed

Moon, Jee Hyun; Kim, Kyung Hwan; Choi, Hyung Wook; Lee, Sang Wha; Park, Sang Joon

2008-09-01

An electroless silver coating of rod-like glass particles was performed and silver glass composite powders were prepared to impart electrical conductivity to these non-conducting glass particles. The low density Ag-coated glass particles may be utilized for manufacturing conducting inorganic materials for electromagnetic interference (EMI) shielding applications and the techniques for controlling the uniform thickness of silver coating can be employed in preparation of biosensor materials. For the surface pretreatment, Sn sensitization was performed and the coating powders were characterized by scanning electron microscopy (SEM), focused ion beam microscopy (FIB), and atomic force microscopy (AFM) along with the surface resistant measurements. In particular, the use of FIB technique for determining directly the Ag-coating thickness was very effective on obtaining the optimum conditions for coating. The surface sensitization and initial silver loading for electroless silver coating could be found and the uniform and smooth silver-coated layer with thickness of 46 nm was prepared at 2 mol/l of Sn and 20% silver loading.

A study of silver species on silver-exchanged ETS-10 and mordenite by XRD, SEM and solid-state 109Ag, 29Si and 27AI NMR spectroscopy.

PubMed

Liu, Yan; Chen, Fu; Wasylishen, Roderick E; Xu, Zhenghe; Sawada, James; Kuznicki, Steven M

2012-08-01

Silver zeolites, especially Ag-ETS-10 and Ag-mordenite, actively bind xenon and iodine, two prime contaminants common to nuclear accidents. The evolution of silver species on silver exchanged ETS-10 (Ag/ETS-10) and mordenite (Ag/Mor) has been investigated by exposing the materials to a series of activation conditions in Ar, air and H2. The samples were characterized by XRD, SEM and solid-state 109Ag, 29Si and 27AI MAS NMR. The silver reduction and structural evolution have been illustrated by those techniques. The effectiveness of one sample of each type of sieve was tested for its ability to trap mercury from a gas stream. However, the results from this study demonstrate that the adsorption characteristics of silver-loaded sieves cannot necessarily be predicted using a full complement of structural characterization techniques, which highlights the importance of understanding the formation and nature of silver species on molecular sieves.

Biosynthesis of silver nanoparticles using lemon leaves extract and its application for antimicrobial finish on fabric

NASA Astrophysics Data System (ADS)

Vankar, Padma S.; Shukla, Dhara

2012-06-01

Preparation of silver nanoparticles have been carried out using aqueous extract of lemon leaves ( Citrus limon) which acts as reducing agent and encapsulating cage for the silver nanoparticles. These silver nanoparticles have been used for durable textile finish on cotton and silk fabrics. Remarkable antifungal activity has been observed in the treated fabrics. The antimicrobial activity of silver nanoparticles derived from lemon leaves showed enhancement in activity due to synergistic effect of silver and essential oil components of lemon leaves. The present investigation shows the extracellular synthesis of highly stable silver nanoparticles by biotransformation using the extract of lemon leaves by controlled reduction of the Ag+ ion to Ag0. Further the silver nanoparticles were used for antifungal treatment of fabrics which was tested by antifungal activity assessment of textile material by Agar diffusion method against Fusarium oxysporum and Alternaria brassicicola. Formation of the metallic nanoparticles was established by FT-IR, UV-Visible spectroscopy, transmission electron microscopy, scanning electron microscopy, atomic force microscopy.

Electrodeposition as an alternate method for preparation of environmental samples for iodide by AMS

DOE PAGES

Adamic, M. L.; Lister, T. E.; Dufek, E. J.; ...

2015-03-25

This paper presents an evaluation of an alternate method for preparing environmental samples for 129I analysis by accelerator mass spectrometry (AMS) at Idaho National Laboratory. The optimal sample preparation method is characterized by ease of preparation, capability of processing very small quantities of iodide, and ease of loading into a cathode. Electrodeposition of iodide on a silver wire was evaluated using these criteria. This study indicates that the electrochemically-formed silver iodide deposits produce ion currents similar to those from precipitated silver iodide for the same sample mass. Furthermore, precipitated silver iodide samples are usually mixed with niobium or silver powdermore » prior to loading in a cathode. Using electrodeposition, the silver is already mixed with the sample and can simply be picked up with tweezers, placed in the sample die, and pressed into a cathode. The major advantage of this method is that the silver wire/electrodeposited silver iodide is much easier to load into a cathode.« less

Ultra-low temperature curable nano-silver conductive adhesive for piezoelectric composite material

NASA Astrophysics Data System (ADS)

Yan, Chao; Liao, Qingwei; Zhou, Xingli; Wang, Likun; Zhong, Chao; Zhang, Di

2018-01-01

Limited by the low thermal resistance of composite material, ultra-low temperature curable conductive silver adhesive with curing temperature less than 100 °C needed urgently for the surface conduction treatment of piezoelectric composite material. An ultra-low temperature curable nano-silver conductive adhesive with high adhesion strength for the applications of piezoelectric composite material was investigated. The crystal structure of cured adhesive, SEM/EDS analysis, thermal analysis, adhesive properties and conductive properties of different content of nano-silver filler or micron-silver doping samples were studied. The results show that with 60 wt.% nano-silver filler the ultra-low temperature curable conductive silver adhesive had the relatively good conductivity as volume resistivity of 2.37 × 10-4 Ω cm, and good adhesion strength of 5.13 MPa. Minor micron-doping (below 15 wt.%) could improve conductivity, but would decrease other properties. The ultra-low temperature curable nano-silver conductive adhesive could successfully applied to piezoelectric composite material.

Laser-Direct Writing of Silver Metal Electrodes on Transparent Flexible Substrates with High-Bonding Strength.

PubMed

Zhou, Weiping; Bai, Shi; Ma, Ying; Ma, Delong; Hou, Tingxiu; Shi, Xiaomin; Hu, Anming

2016-09-21

We demonstrate a novel approach to rapidly fabricate conductive silver electrodes on transparent flexible substrates with high-bonding strength by laser-direct writing. A new type of silver ink composed of silver nitrate, sodium citrate, and polyvinylpyrrolidone (PVP) was prepared in this work. The role of PVP was elucidated for improving the quality of silver electrodes. Silver nanoparticles and sintered microstructures were simultaneously synthesized and patterned on a substrate using a focused 405 nm continuous wave laser. The writing was completed through the transparent flexible substrate with a programmed 2D scanning sample stage. Silver electrodes fabricated by this approach exhibit a remarkable bonding strength, which can withstand an adhesive tape test at least 50 times. After a 1500 time bending test, the resistance only increased 5.2%. With laser-induced in-situ synthesis, sintering, and simultaneous patterning of silver nanoparticles, this technology is promising for the facile fabrication of conducting electronic devices on flexible substrates.

Recovery of Silver and Gold from Copper Anode Slimes

NASA Astrophysics Data System (ADS)

Chen, Ailiang; Peng, Zhiwei; Hwang, Jiann-Yang; Ma, Yutian; Liu, Xuheng; Chen, Xingyu

2015-02-01

Copper anode slimes, produced from copper electrolytic refining, are important industrial by-products containing several valuable metals, particularly silver and gold. This article provides a comprehensive overview of the development of the extraction processes for recovering silver and gold from conventional copper anode slimes. Existing processes, namely pyrometallurgical processes, hydrometallurgical processes, and hybrid processes involving the combination of pyrometallurgical and hydrometallurgical technologies, are discussed based in part on a review of the form and characteristics of silver and gold in copper anode slimes. The recovery of silver and gold in pyrometallurgical processes is influenced in part by the slag and matte/metal chemistry and related characteristics, whereas the extraction of these metals in hydrometallurgical processes depends on the leaching reagents used to break the structure of the silver- and gold-bearing phases, such as selenides. By taking advantage of both pyrometallurgical and hydrometallurgical techniques, high extraction yields of silver and gold can be obtained using such combined approaches that appear promising for efficient extraction of silver and gold from copper anode slimes.

Synthesis, characterization and antimicrobial activity of dextran stabilized silver nanoparticles in aqueous medium.

PubMed

Bankura, K P; Maity, D; Mollick, M M R; Mondal, D; Bhowmick, B; Bain, M K; Chakraborty, A; Sarkar, J; Acharya, K; Chattopadhyay, D

2012-08-01

A simple one-step rapid synthetic route is described for the preparation of silver nanoparticles by reduction of silver nitrate (AgNO3) using aqueous dextran solution which acts as both reducing and capping agent. The formation of silver nanoparticles is assured by characterization with UV-vis spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The absorbance of the silver nanoparticles is observed at 423 nm. The AFM image clearly shows the surface morphology of the well-dispersed silver nanoparticles with size range of 10-60 nm. TEM images show that the nanoparticles are spherical in shape with ∼5-10 nm dimensions. The crystallinity of Ag nanoparticles is assured by XRD analysis. The antimicrobial activity of as synthesized silver nanoparticles is tested against the bacteria, Bacillus subtilis, Bacillus cereus, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The bacterial growth is inhibited by gradual reduction of the concentration of the silver nanoparticles. Copyright © 2012 Elsevier Ltd. All rights reserved.

Synthesis and characterization of silver nanoparticles using Caesalpinia pulcherrima flower extract and assessment of their in vitro antimicrobial, antioxidant, cytotoxic, and genotoxic activities.

PubMed

Moteriya, Pooja; Chanda, Sumitra

2017-12-01

Caesalpinia pulcherrima flower extract mediated synthesis of silver nanoparticles was attempted in the present work including optimization of some procedure parameters. Characterization of synthesized silver nanoparticles was done by various spectral analyses. The size of synthesized silver nanoparticles was 12 nm and they were spherical in shape. The green synthesized silver nanoparticles were further evaluated for antimicrobial, antioxidant, cytotoxic, and genotoxic activities; they showed good antimicrobial, antioxidant, and cytotoxic effects. Genotoxic study revealed non-toxic nature at lower concentration. Overall results suggest that the synthesized silver nanoparticles have pronounced applicability in pharmaceutical and biomedical field.

Extraction of three-dimensional silver nanostructures with supercritical fluid

NASA Astrophysics Data System (ADS)

Taguchi, Natsuo; Takeyasu, Nobuyuki; Kawata, Satoshi

2018-02-01

In a previous report, a self-growing approach was proposed for fabricating complex silver nanostructures, where silver dendrites were grown at silver nanoseeds in silver ion solution owing to plasmonic heating with ultraviolet light. Structures were deformed or destroyed when they were extracted with acetone and dried in air. In this Letter, we discuss the use of supercritical carbon dioxide fluid for the nondestructive extraction of nanostructures. We show the experimental results and discuss the laser power dependence of resultant structures. Another experiment was performed for nanostructure growth inside an agarose gel as a matrix. Silver nanostructures were immobilized without damage in an agarose skeleton network.

Synthesis of silver nanoparticles from Melia dubia leaf extract and their in vitro anticancer activity

NASA Astrophysics Data System (ADS)

Kathiravan, V.; Ravi, S.; Ashokkumar, S.

2014-09-01

Silver nanoparticles have a significant role in the pharmaceutical science. Especially, silver nanoparticles synthesized by the plant extracts lead a significant role in biological activities such as antimicrobial, antioxidant and anticancer. Keeping this in mind, the present work investigation has been taken up with the synthesized silver nanoparticles using the plant extract of Melia dubia and it characterizes by using UV-visible, XRD and SEM-EDS. The effect of the silver nanoparticles on human breast cancer (KB) cell line has been tested. Silver nanoparticles showed remarkable cytotoxicity activity against KB cell line with evidence of high therapeutic index value are the results are discussed.

One-Pot Silver Nanoring Synthesis

NASA Astrophysics Data System (ADS)

Drogat, Nicolas; Granet, Robert; Sol, Vincent; Krausz, Pierre

2010-03-01

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV-vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation.

One-pot silver nanoring synthesis.

PubMed

Drogat, Nicolas; Granet, Robert; Sol, Vincent; Krausz, Pierre

2009-12-16

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV-vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation.

One-Pot Silver Nanoring Synthesis

PubMed Central

2010-01-01

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV–vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation. PMID:20672109

Dermal exposure potential from textiles that contain silver nanoparticles

PubMed Central

Stefaniak, Aleksandr B; Duling, Mathew G; Lawrence, Robert B; Thomas, Treye A; LeBouf, Ryan F; Wade, Eleanor E; Abbas Virji, M

2014-01-01

Background: Factors that influence exposure to silver particles from the use of textiles are not well understood. Objectives: The aim of this study was to evaluate the influence of product treatment and physiological factors on silver release from two textiles. Methods: Atomic and absorbance spectroscopy, electron microscopy, and dynamic light scattering (DLS) were applied to characterize the chemical and physical properties of the textiles and evaluate silver release in artificial sweat and saliva under varying physiological conditions. One textile had silver incorporated into fiber threads (masterbatch process) and the other had silver nanoparticles coated on fiber surfaces (finishing process). Results: Several complementary and confirmatory analytical techniques (spectroscopy, microscopy, etc.) were required to properly assess silver release. Silver released into artificial sweat or saliva was primarily in ionic form. In a simulated “use” and laundering experiment, the total cumulative amount of silver ion released was greater for the finishing process textile (0.51±0.04%) than the masterbatch process textile (0.21±0.01%); P<0.01. Conclusions: We found that the process (masterbatch vs finishing) used to treat textile fibers was a more influential exposure factor than physiological properties of artificial sweat or saliva. PMID:25000110

A microcantilever-based silver ion sensor using DNA-functionalized gold nanoparticles as a mass amplifier

NASA Astrophysics Data System (ADS)

You, Juneseok; Song, Yeongjin; Park, Chanho; Jang, Kuewhan; Na, Sungsoo

2017-06-01

Silver ions have been used to sterilize many products, however, it has recently been demonstrated that silver ions can be toxic. This toxicity has been studied over many years with the lethal concentration at 10 μM. Silver ions can accumulate through the food chain, causing serious health problems in many species. Hence, there is a need for a commercially available silver ion sensor, with high detection sensitivity. In this work, we develop an ultra-sensitive silver ion sensor platform, using cytosine based DNA and gold nanoparticles as the mass amplifier. We achieve a lower detection limit for silver ions of 10 pM; this detection limit is one million times lower than the toxic concentration. Using our sensor platform we examine highly selective characteristics of other typical ions in water from natural sources. Furthermore, our sensor platform is able to detect silver ions in a real practical sample of commercially available drinking water. Our sensor platform, which we have termed a ‘MAIS’ (mass amplifier ion sensor), with a simple detection procedure, high sensitivity, selectivity and real practical applicability has shown potential as an early toxicity assessment of silver ions in the environment.

Preparation of solid silver nanoparticles for inkjet printed flexible electronics with high conductivity.

PubMed

Shen, Wenfeng; Zhang, Xianpeng; Huang, Qijin; Xu, Qingsong; Song, Weijie

2014-01-01

Silver nanoparticles (NPs) which could be kept in solid form and were easily stored without degeneration or oxidation at room temperature for a long period of time were synthesized by a simple and environmentally friendly wet chemistry method in an aqueous phase. Highly stable dispersions of aqueous silver NP inks, sintered at room temperature, for printing highly conductive tracks (∼8.0 μΩ cm) were prepared simply by dispersing the synthesized silver NP powder in water. These inks are stable, fairly homogeneous and suitable for a wide range of patterning techniques. The inks were successfully printed on paper and polyethylene terephthalate (PET) substrates using a common color printer. Upon annealing at 180 °C, the resistivity of the printed silver patterns decreased to 3.7 μΩ cm, which is close to twice that of bulk silver. Various factors affecting the resistivity of the printed silver patterns, such as annealing temperature and the number of printing cycles, were investigated. The resulting high conductivity of the printed silver patterns reached over 20% of the bulk silver value under ambient conditions, which enabled the fabrication of flexible electronic devices, as demonstrated by the inkjet printing of conductive circuits of LED devices.

Dermal exposure potential from textiles that contain silver nanoparticles.

PubMed

Stefaniak, Aleksandr B; Duling, Mathew G; Lawrence, Robert B; Thomas, Treye A; LeBouf, Ryan F; Wade, Eleanor E; Virji, M Abbas

2014-01-01

Factors that influence exposure to silver particles from the use of textiles are not well understood. The aim of this study was to evaluate the influence of product treatment and physiological factors on silver release from two textiles. Atomic and absorbance spectroscopy, electron microscopy, and dynamic light scattering (DLS) were applied to characterize the chemical and physical properties of the textiles and evaluate silver release in artificial sweat and saliva under varying physiological conditions. One textile had silver incorporated into fiber threads (masterbatch process) and the other had silver nanoparticles coated on fiber surfaces (finishing process). Several complementary and confirmatory analytical techniques (spectroscopy, microscopy, etc.) were required to properly assess silver release. Silver released into artificial sweat or saliva was primarily in ionic form. In a simulated "use" and laundering experiment, the total cumulative amount of silver ion released was greater for the finishing process textile (0·51±0·04%) than the masterbatch process textile (0·21±0·01%); P<0·01. We found that the process (masterbatch vs finishing) used to treat textile fibers was a more influential exposure factor than physiological properties of artificial sweat or saliva.

Feasibility of the silver-UV process for drinking water disinfection.

PubMed

Butkus, Michael A; Talbot, Mark; Labare, Michael P

2005-12-01

A synergistic effect between cationic silver and UV radiation (silver-UV disinfection) has been observed that can appreciably enhance inactivation of viruses. The purpose of this work was to assess the feasibility of this technique for drinking water disinfection and evaluate the effects of selected impurities, found in fresh water, and common parameters on inactivation of the coliphage MS-2 with the silver-UV process. Turbidity (kaolin), calcium hardness, carbonate alkalinity, and pH did not significantly degrade inactivation. Inactivation was reduced in the presence of chloride, at concentrations greater than 30 mg/L, and in water samples with UV-254 absorbance values greater than ca. 0.1 cm(-1). Inactivation of MS-2 with silver-UV disinfection was also reduced at high phosphate concentrations (above ca. 5 mM). Silver-UV inactivation of MS-2 increased with increases in temperature between 10 and 20 degrees C. Silver-UV inactivation of MS-2 was increased by greater than 1-log over UV alone, in two untreated fresh water sources, which indicates that silver-UV may be a viable treatment technology. An assessment of operation and management costs suggests that an increase in inactivation of MS-2 with silver-UV disinfection could be economically beneficial.

The sorption of silver by poorly crystallized manganese oxides

USGS Publications Warehouse

Anderson, B.J.; Jenne, E.A.; Chao, T.T.

1973-01-01

The sorption of silver by poorly crystallized manganese oxides was studied using synthesized samples of three members of the manganous manganite (birnessite) group, of different chemical composition and crystallinity, and a poorly organized ??-MnO2. All four oxides sorbed significant quantities of silver. The manganous manganites showed the greatest sorption (up to 0.5 moles silver/mole MnOx at pH 7) while the ??-MnO2 showed the least (0.3 moles silver/ mole MnOx at pH 7). Sorption of silver was adequately described by the Langmuir equation over a considerable concentration range. The relationship failed at low pH values and high equilibrium silver concentrations. The sorption capacity showed a direct relationship with pH. However, the rate of increase of sorption capacity decreased at the higher pH values. Silver sorption maxima. were not directly related to surface area but appeared to vary with the amount of occluded sodium and potassium present in the manganese oxide. The important processes involved in the uptake of silver by the four poorly crystallized manganese oxides ara considered to be surface exchange for manganese, potassium and sodium as well as exchange for structural manganese, potassium and sodium. ?? 1973.

Laser cladding of stainless steel with a copper-silver alloy to generate surfaces of high antimicrobial activity

NASA Astrophysics Data System (ADS)

Hans, Michael; Támara, Juan Carlos; Mathews, Salima; Bax, Benjamin; Hegetschweiler, Andreas; Kautenburger, Ralf; Solioz, Marc; Mücklich, Frank

2014-11-01

Copper and silver are used as antimicrobial agents in the healthcare sector in an effort to curb infections caused by bacteria resistant to multiple antibiotics. While the bactericidal potential of copper and silver alone are well documented, not much is known about the antimicrobial properties of copper-silver alloys. This study focuses on the antibacterial activity and material aspects of a copper-silver model alloy with 10 wt% Ag. The alloy was generated as a coating with controlled intermixing of copper and silver on stainless steel by a laser cladding process. The microstructure of the clad was found to be two-phased and in thermal equilibrium with minor Cu2O inclusions. Ion release and killing of Escherichia coli under wet conditions were assessed with the alloy, pure silver, pure copper and stainless steel. It was found that the copper-silver alloy, compared to the pure elements, exhibited enhanced killing of E. coli, which correlated with an up to 28-fold increased release of copper ions. The results show that laser cladding with copper and silver allows the generation of surfaces with enhanced antimicrobial properties. The process is particularly attractive since it can be applied to existing surfaces.

Developmental toxicity and DNA damaging properties of silver nanoparticles in the catfish (Clarias gariepinus).

PubMed

Sayed, Alaa El-Din H; Soliman, Hamdy A M

2017-10-01

Although, silver nanoparticles (AgNPs) are used in many different products, little information is known about their toxicity in tropical fish embryos. Therefore, this study evaluated the developmental toxicity of waterborne silver nanoparticles in embryos of Clarias gariepinus. Embryos were treated with (0, 25, 50, 75ng/L silver nanoparticles) in water up to 144h postfertilization stage (PFS). Results revealed various morphological malformations including notochord curvature and edema. The mortality rate, malformations, and DNA fragmentation in embryos exposed to silver nanoparticles increased in a dose- and embryonic stage-dependent manner. The total antioxidant capacity and the activity of catalase in embryos exposed to 25ng/L silver nanoparticles were decreased significantly while the total antioxidant capacity and the activity of catalase were insignificantly increased with increasing concentrations in the embryos from 24 to 144 h-PFS exposed to 50 and 75ng/L silver nanoparticles. Lipid peroxidation values showed fluctuations with doses of silver nanoparticles. Histopathological lesions including severely distorted and wrinkled notochord were observed. The current data propose that the toxicity of silver nanoparticles in C. gariepinus embryos is caused by oxidative stress and genotoxicity. Copyright © 2017 Elsevier B.V. All rights reserved.

PVP-coated, negatively charged silver nanoparticles: A multi-center study of their physicochemical characteristics, cell culture and in vivo experiments

PubMed Central

Ahlberg, Sebastian; Antonopulos, Alexandra; Diendorf, Jörg; Dringen, Ralf; Flöck, Rebekka; Goedecke, Wolfgang; Graf, Christina; Haberl, Nadine; Helmlinger, Jens; Herzog, Fabian; Heuer, Frederike; Hirn, Stephanie; Johannes, Christian; Kittler, Stefanie; Köller, Manfred; Korn, Katrin; Kreyling, Wolfgang G; Krombach, Fritz; Lademann, Jürgen; Loza, Kateryna; Luther, Eva M; Malissek, Marcelina; Meinke, Martina C; Nordmeyer, Daniel; Pailliart, Anne; Raabe, Jörg; Rancan, Fiorenza; Rothen-Rutishauser, Barbara; Rühl, Eckart; Schleh, Carsten; Seibel, Andreas; Sengstock, Christina; Treuel, Lennart; Vogt, Annika; Weber, Katrin; Zellner, Reinhard

2014-01-01

Summary PVP-capped silver nanoparticles with a diameter of the metallic core of 70 nm, a hydrodynamic diameter of 120 nm and a zeta potential of −20 mV were prepared and investigated with regard to their biological activity. This review summarizes the physicochemical properties (dissolution, protein adsorption, dispersability) of these nanoparticles and the cellular consequences of the exposure of a broad range of biological test systems to this defined type of silver nanoparticles. Silver nanoparticles dissolve in water in the presence of oxygen. In addition, in biological media (i.e., in the presence of proteins) the surface of silver nanoparticles is rapidly coated by a protein corona that influences their physicochemical and biological properties including cellular uptake. Silver nanoparticles are taken up by cell-type specific endocytosis pathways as demonstrated for hMSC, primary T-cells, primary monocytes, and astrocytes. A visualization of particles inside cells is possible by X-ray microscopy, fluorescence microscopy, and combined FIB/SEM analysis. By staining organelles, their localization inside the cell can be additionally determined. While primary brain astrocytes are shown to be fairly tolerant toward silver nanoparticles, silver nanoparticles induce the formation of DNA double-strand-breaks (DSB) and lead to chromosomal aberrations and sister-chromatid exchanges in Chinese hamster fibroblast cell lines (CHO9, K1, V79B). An exposure of rats to silver nanoparticles in vivo induced a moderate pulmonary toxicity, however, only at rather high concentrations. The same was found in precision-cut lung slices of rats in which silver nanoparticles remained mainly at the tissue surface. In a human 3D triple-cell culture model consisting of three cell types (alveolar epithelial cells, macrophages, and dendritic cells), adverse effects were also only found at high silver concentrations. The silver ions that are released from silver nanoparticles may be harmful to skin with disrupted barrier (e.g., wounds) and induce oxidative stress in skin cells (HaCaT). In conclusion, the data obtained on the effects of this well-defined type of silver nanoparticles on various biological systems clearly demonstrate that cell-type specific properties as well as experimental conditions determine the biocompatibility of and the cellular responses to an exposure with silver nanoparticles. PMID:25383306

The 20 kilovolt rocket borne electron accelerator. [equipment specifications

NASA Technical Reports Server (NTRS)

Harrison, R.

1973-01-01

The accelerator system is a preprogrammed multi-voltage system capable of operating at a current level of 1/2 ampere at the 20 kilovolt level. The five major functional areas which comprise this system are: (1) Silver zinc battery packs; (2) the electron gun assembly; (3) gun control and opening circuits; (4) the telemetry conditioning section; and (5) the power conversion section.

Species- and tissue-specific mercury bioaccumulation in five fish species from Laizhou Bay in the Bohai Sea of China

NASA Astrophysics Data System (ADS)

Liu, Jinhu; Cao, Liang; Huang, Wei; Dou, Shuozeng

2013-05-01

Mercury (Hg) concentrations in the tissues (muscle, stomach, liver, gills, skin, and gonads) of five fish species (mullet Liza ha em atocheil us, flathead fish Platycephalus indicus, sea bass Lateolabrax japonic u s, mackerel Scomberomorus niphonius and silver pomfret Pampus argenteus) collected from Laizhou Bay in the Bohai Sea of China were investigated. The results indicate that Hg bioaccumulation in the five fish was tissue-specific, with the highest levels in the muscle and liver, followed by the stomach and gonads. The lowest levels were found in the gills and skin. Fish at higher trophic levels (flathead fish and sea bass) exhibited higher Hg concentrations than consumers at lower trophic levels. Mercury bioaccumulation tended to be positively correlated with fish length in mullet, silver pomfret, mackerel, and flathead fish, but was negatively correlated with fish length in sea bass. The Hg concentrations in the muscles of all fish species in Laizhou Bay were within the permissible limits of food safety set by national and international criteria. However, the suggesting maximum consumption of sea bass is 263 g per week for human health.

Pilot study on control of phytoplankton by zooplankton coupling with filter-feeding fish in surface water.

PubMed

Ma, Hua; Cui, Fuyi; Liu, Zhiquan; Fan, Zhenqiang

2009-01-01

A pilot-scale facility was originally designed to control phytoplankton in algae-laden reservoir water characterized by summer cyanobacteria blooms (mainly Microcystis flos-aquae). The system made good use of the different food habits of Daphnia magna and silver carp. Zooplankton (Daphnia magna), filter-feeding fish (silver carp), and zooplankton (Daphnia magna) were stocked in three separated tanks in sequence, respectively. Thus, single-cell phytoplankton and some Microcystis flos-aquae in small size were first grazed by Daphnia magna in the first tank, and in the second tank phytoplankton larger than 10 microm were filtered by silver carp, and the concentration of the remaining phytoplankton was further reduced to a rather low level by Daphnia magna in the third tank. The results showed that the system had good removal efficiencies of phytoplankton and chlorophyll a, 86.85% and 59.41%, respectively, and permanganate consumption (COD(Mn)) and turbidity were lowered as well. A high phytoplankton removal efficiency and low cost indicated that the system had a good advantage in pre-treating algae-laden source water in drinking water works.

Nanostructured Ag-zeolite Composites as Luminescence-based Humidity Sensors.

PubMed

Coutino-Gonzalez, Eduardo; Baekelant, Wouter; Dieu, Bjorn; Roeffaers, Maarten B J; Hofkens, Johan

2016-11-15

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high external quantum efficiencies (EQE) and spans the whole visible spectrum. It has been recently reported that the UV excited luminescence of partially Li-exchanged sodium Linde type A zeolites [LTA(Na)] containing luminescent silver clusters can be controlled by adjusting the water content of the zeolite. These samples showed a dynamic change in their emission color from blue to green and yellow upon an increase of the hydration level of the zeolite, showing the great potential that these materials can have as luminescence-based humidity sensors at the macro and micro scale. Here, we describe the detailed procedure to fabricate a humidity sensor prototype using silver-exchanged zeolite composites. The sensor is produced by suspending the luminescent Ag-zeolites in an aqueous solution of polyethylenimine (PEI) to subsequently deposit a film of the material onto a quartz plate. The coated plate is subjected to several hydration/dehydration cycles to show the functionality of the sensing film.

Nanostructured Ag-zeolite Composites as Luminescence-based Humidity Sensors

PubMed Central

Dieu, Bjorn; Roeffaers, Maarten B.J.; Hofkens, Johan

2016-01-01

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high external quantum efficiencies (EQE) and spans the whole visible spectrum. It has been recently reported that the UV excited luminescence of partially Li-exchanged sodium Linde type A zeolites [LTA(Na)] containing luminescent silver clusters can be controlled by adjusting the water content of the zeolite. These samples showed a dynamic change in their emission color from blue to green and yellow upon an increase of the hydration level of the zeolite, showing the great potential that these materials can have as luminescence-based humidity sensors at the macro and micro scale. Here, we describe the detailed procedure to fabricate a humidity sensor prototype using silver-exchanged zeolite composites. The sensor is produced by suspending the luminescent Ag-zeolites in an aqueous solution of polyethylenimine (PEI) to subsequently deposit a film of the material onto a quartz plate. The coated plate is subjected to several hydration/dehydration cycles to show the functionality of the sensing film. PMID:27911397

The effect of the new Massachusetts Bay sewage outfall on the concentrations of metals and bacterial spores in nearby bottom and suspended sediments

USGS Publications Warehouse

Bothner, Michael H.; Casso, M.A.; Rendigs, R. R.; Lamothe, P.J.

2002-01-01

Since the new outfall for Boston's treated sewage effluent began operation on September 6, 2000, no change has been observed in concentrations of silver or Clostridium perfringens spores (an ecologically benign tracer of sewage), in bottom sediments at a site 2.5 km west of the outfall. In suspended sediment samples collected with a time-series sediment trap located 1.3 km south of the outfall, silver and C. perfringens spores increased by 38% and 103%, respectively, in post-outfall samples while chromium, copper, and zinc showed no change. All metal concentrations in sediments are <50% of warning levels established by the Massachusetts Water Resources Authority. An 11-year data set of bottom sediment characteristics collected three times per year prior to outfall startup provides perspective for the interpretation of post-outfall data. A greater than twofold increase in concentrations of sewage tracers (silver and C. perfringens) was observed in muddy sediments following the exceptional storm of December 11-16, 1992 that presumably moved contaminated inshore sediment offshore. ?? 2002 Elsevier Science Ltd. All rights reserved.

Synthesis and characterization of antimicrobial nanosilver/diatomite nanocomposites and its water treatment application

NASA Astrophysics Data System (ADS)

Xia, Yijie; Jiang, Xiaoyu; Zhang, Jing; Lin, Ming; Tang, Xiaosheng; Zhang, Jie; Liu, Hongjun

2017-02-01

Nanotechnology for water disinfection application gains increasing attention. Diatomite is one kind of safe natural material, which has been widely used as absorbent, filtration agents, mineral fillers, especially in water treatment industry. Nanosilver/diatomite nanocomposites were developed in this publication with a facile, effective in-situ reduction method. The as-prepared nanosilver/diatomite nanocomposites demonstrated amazing antibacterial properties to gram-positive and gram-negative bacteria. The corresponding property has been characterized by UV-vis absorbance, Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX) and X-ray Photoelectron Spectroscopy (XPS). Moreover, the detailed bacteria killing experiments further displayed that 0.5 g of the nanosilver diatomite could kill >99.999% of E. Coli within half an hour time. And the silver leaching test demonstrated that the concentrations of silver in the filtered water under varies pH environment were below the limit for silver level of WHO standard. Considering the low price of natural diatomite, it is believed that the nanosilver/diatomite nanocomposites have potential application in water purification industry due to its excellent antimicrobial property.

Three-dimensional hybrid silicon nanostructures for surface enhanced Raman spectroscopy based molecular detection

NASA Astrophysics Data System (ADS)

Vendamani, V. S.; Nageswara Rao, S. V. S.; Venugopal Rao, S.; Kanjilal, D.; Pathak, A. P.

2018-01-01

Three-dimensional silver nanoparticles decorated vertically aligned Si nanowires (Si NWs) are effective surface-enhanced Raman spectroscopy (SERS) substrates for molecular detection at low concentration levels. The length of Si NWs prepared by silver assisted electroless etching is increased with an increase in etching time, which resulted in the reduced optical reflection in the visible region. These substrates were tested and optimized by measuring the Raman spectrum of standard dye Rhodamine 6G (R6G) of 10 nM concentration. Further, effective SERS enhancements of ˜105 and ˜104 were observed for the cytosine protein (concentration of 50 μM) and ammonium perchlorate (oxidizer used in explosives composition with a concentration of 10 μM), respectively. It is established that these three-dimensional SERS substrates yielded considerably higher enhancement factors for the detection of R6G when compared to previous reports. The sensitivity can further be increased and optimized since the Raman enhancement was found to increase with an increase in the density of silver nanoparticles decorated on the walls of Si NWs.

40 CFR 415.530 - Applicability; description of the silver nitrate production subcategory.

Code of Federal Regulations, 2013 CFR

2013-07-01

... silver nitrate production subcategory. 415.530 Section 415.530 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Silver Nitrate Production Subcategory § 415.530 Applicability; description of the silver nitrate production subcategory. The provisions of this subpart are applicable to discharges and to the...

40 CFR 415.530 - Applicability; description of the silver nitrate production subcategory.

Code of Federal Regulations, 2011 CFR

2011-07-01

... silver nitrate production subcategory. 415.530 Section 415.530 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Silver Nitrate Production Subcategory § 415.530 Applicability; description of the silver nitrate production subcategory. The provisions of this subpart are applicable to discharges and to the...

40 CFR 415.530 - Applicability; description of the silver nitrate production subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... silver nitrate production subcategory. 415.530 Section 415.530 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Silver Nitrate Production Subcategory § 415.530 Applicability; description of the silver nitrate production subcategory. The provisions of this subpart are applicable to discharges and to the...

40 CFR 415.530 - Applicability; description of the silver nitrate production subcategory.

Code of Federal Regulations, 2014 CFR

2014-07-01

... silver nitrate production subcategory. 415.530 Section 415.530 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Silver Nitrate Production Subcategory § 415.530 Applicability; description of the silver nitrate production subcategory. The provisions of this subpart are applicable to discharges and to the...