Effects of Silver Nanoparticles on Hematological Parameters and Hepatorenal Functions in Laying Japanese Quails

Silver nanoparticles (AgNPs) have recently emerged as a powerful agents for disinfection in the poultry industry. AgNPs are capable of epithelial barriers passing from the route of exposure to the vital organs and cells. This study evaluated the effects of AgNPs on organs weights, blood biochemical, hematological, and coagulation parameters, antioxidant enzyme activities, and histopathological changes and silver concentrations of liver and kidney tissues in laying Japanese quails after exposure to the nanoparticles. The layer quails were randomly assigned to 4 groups, consisting of six replicates, three quails each. The treatments included 0, 4, 8, and 12 mg/L of AgNPs in daily drinking water for 30 weeks. AgNPs decreased the relative weight of liver, ileum and large intestine (P < 0.05). Administration of AgNPs elevated plasma fibrinogen while decreased serum aspartate aminotransferase activity (P < 0.05). The antioxidant status of the liver showed that malondialdehyde level, an end product of lipid peroxidation, was higher (P < 0.05) and catalase activity was lower (P < 0.05) in the quails exposed to AgNPs. The accumulation of silver in the liver and kidney tissues were increased in a dose-dependent manner after exposure to AgNPs (P < 0.05). Histopathological findings showed reduced lipid vacuolization of hepatocytes in the 12 mg/L AgNPs treatment. In conclusion, the results indicated that AgNPs administration to drinking water can lead to oxidative stress and liver damage in laying quails which may be a predisposing for liver dysfunction.

Silver absorption and toxicity evaluation of silver wound dressings in 40 patients with chronic wounds

BACKGROUND

Silver-containing dressings are considered to be safe even though there have been some reports of complications, including argyria and various organ system dysfunctions. Despite the widespread use of silver dressings, little research has been done regarding the absorption and toxicity of silver.

OBJECTIVE

We aimed to study the systemic absorption of silver in patients with chronic inflammatory wounds and to determine associated factors of systemic silver absorption and evaluated its association with silver toxicity.

PATIENTS AND METHOD

Prospective, longitudinal, observational, multicentre, open-label pilot study. Patients from the Dermatology Departments of Lorraine (France) with the following inclusion criteria: (i) a chronic wound of more than 6 weeks and (ii) an ulcer needing silver-containing dressing were included. Before and after 28 days of treatment, clinical characteristics of the wound were recorded; hemogram, hepatic and renal functions, albumin sera and serum silver level were measured.

RESULTS

Half of the cases displayed raised levels of silver after 1 month of treatment. Predictive factors for systemic silver absorption were wound area, anaemia and malnutrition with anaemia and malnutrition confirmed on multivariate analysis. Wound vascularization may also play a role, as a higher absorption was observed in cases of wound granulation without arterial components. No toxicity was detected. This work has also emphasized the slow elimination of silver from the body.

CONCLUSION

Both long-term application and iterative treatments with silver dressings should be discouraged, especially in the elderly, who often suffer from malnutrition and anaemia to avoid potential cumulative toxicity.

Tissue distribution and acute toxicity of silver after single intravenous administration in mice: nano-specific and size-dependent effects

BACKGROUND

Silver nanoparticles (AgNPs) are an important class of nanomaterials used as antimicrobial agents for a wide range of medical and industrial applications. However toxicity of AgNPs and impact of their physicochemical characteristics in in vivo models still need to be comprehensively characterized. The aim of this study was to investigate the effect of size and coating on tissue distribution and toxicity of AgNPs after intravenous administration in mice, and compare the results with those obtained after silver acetate administration.

METHODS

Male CD-1(ICR) mice were intravenously injected with AgNPs of different sizes (10 nm, 40 nm, 100 nm), citrate-or polyvinylpyrrolidone-coated, at a single dose of 10 mg/kg bw. An equivalent dose of silver ions was administered as silver acetate. Mice were euthanized 24 h after the treatment, and silver quantification by ICP-MS and histopathology were performed on spleen, liver, lungs, kidneys, brain, and blood.

RESULTS

For all particle sizes, regardless of their coating, the highest silver concentrations were found in the spleen and liver, followed by lung, kidney, and brain. Silver concentrations were significantly higher in the spleen, lung, kidney, brain, and blood of mice treated with 10 nm AgNPs than those treated with larger particles. Relevant toxic effects (midzonal hepatocellular necrosis, gall bladder hemorrhage) were found in mice treated with 10 nm AgNPs, while in mice treated with 40 nm and 100 nm AgNPs lesions were milder or negligible, respectively. In mice treated with silver acetate, silver concentrations were significantly lower in the spleen and lung, and higher in the kidney than in mice treated with 10 nm AgNPs, and a different target organ of toxicity was identified (kidney).

CONCLUSIONS

Administration of the smallest (10 nm) nanoparticles resulted in enhanced silver tissue distribution and overt hepatobiliary toxicity compared to larger ones (40 and 100 nm), while coating had no relevant impact. Distinct patterns of tissue distribution and toxicity were observed after silver acetate administration. It is concluded that if AgNPs become systemically available, they behave differently from ionic silver, exerting distinct and size-dependent effects, strictly related to the nanoparticulate form.

Neurotoxicity of Silver Nanoparticles in Rat Brain After Intragastric Exposure

It is known that the biological half-life of silver in the central nervous system is longer than in other organs. However, the potential toxicity of silver nanoparticles (NPs) on brain tissue and the underlying mechanism(s) of action are not well understood. In this study, neurotoxicity of silver NPs was examined in rat after intragastric administration. After a two-week exposure to low-dose (1 mg/kg, body weight) or high-dose (10 mg/kg) silver NPs, the pathological and ultrastructural changes in brain tissue were evaluated with H&E staining and transmission electron microscopy. The mRNA expression levels of key tight junction proteins of the blood-brain barrier (BBB) were analyzed by real-time RT-PCR, and several inflammatory factors were assessed in blood using ELISA assay. We observed neuron shrinkage, cytoplasmic or foot swelling of astrocytes, and extra-vascular lymphocytes in silver NP exposure groups. The cadherin 1 (2(-ΔΔCt): 1.45-fold/control) and Claudin-1 (2(-ΔΔCt): 2.77-fold/control) were slightly increase in mRNA expression levels, and IL-4 significantly increased after silver NP exposure. It was suggest that silver NP can induce neuronal degeneration and astrocyte swelling, even with a low-dose (1 mg/kg) oral exposure. One potential mechanism for the effects of silver NPs to the nervous cells is involved in inflammatory effects.

Trace elements in obese Turkish children

The quality of the diet of obese children is poor. Eating habits may alter micronutrient status in obese patients. In this study, we determined the serum levels of selenium, zinc, vanadium, molybdenum, iron, copper, beryllium, boron, chromium, manganese, cobalt, silver, barium, aluminum, nickel, cadmium, mercury, and lead in obese Turkish children. Thirty-four obese and 33 healthy control subjects were enrolled in the study. Serum vanadium and cobalt levels of obese children were significantly lower than those of the control group (0.244 ± 0.0179 vs. 0.261 ± 0.012 μg/l, p < 0.001, and 0.14 ± 0.13 vs. 0.24 ± 0.15 μg/l, p = 0.011, respectively). There was no significant difference between groups regarding the other serum trace element levels. In conclusion, there may be alterations in the serum levels of trace elements in obese children and these alterations may have a role in the pathogenesis of obesity.

The interaction between Ag+ and bovine serum albumin: a spectroscopic investigation

By using spectroscopic methods, we probed the interaction of Ag(+) with bovine serum albumin (BSA) in an aqueous environment. Fluorescence of BSA quenched by Ag(+) is a dynamic quenching process. Two binding modes-a strong one at low concentration of Ag(+) and a weak one at high concentration were found. The association constant (K(A)) and the number of binding sites (n) were 4.88×10(3)M(-1) and 1.17 for strong binding, and 17.6M(-1) and 0.547 for weak binding at 293K. The results of thermodynamic parameters ΔH(θ), ΔG(θ) and ΔS(θ) for instinct binding modes at different temperatures indicated that the hydrogen bonding and van der Waals interaction play a major role for low Ag(+)/BSA ratio while electrostatic association for high Ag(+)/BSA ratio. Data of UV-Vis and Circular dichroism (CD) suggested that with the increasing amount of Ag(+), the secondary structure undergoes a decrease in α-helix and an increase in β content and the backbone of BSA experiences a micro-environmental alteration. Furthermore, the distance r between donor (Trp-212) and acceptor (Ag(+)) was evaluated to be 10nm according to nonradiative energy transfer theory.

Conservative management of exomphalos major with silver dressings: are they safe?

Historically, some dressings used in exomphalos major were associated with toxicity. These have been abandoned in favor of safer dressings. Silver toxicity has not been described following the use of silver dressings in infants. We, however, found disconcerting serum silver levels in 2 consecutive patients during treatment with silver salt containing dressings.

Blue lunulae: argyria and hypercopprecaemia

A 42-year-old woman presented with blue lunulae in association with argyria and hypercopprecaemia. The argyria was caused by the regular ingestion of colloidal silver in water over an extended period of time. The raised copper may have contributed to the nail discolouration, and was believed to be due either to ingestion of copper-containing multivitamin tablets or as an acute-phase reactant. We believe that the ease of access to, and lack of stringent regulatory controls over, food supplements and alternative medicines may cause similar cases in the future. We therefore recommend that all patients should be routinely questioned on their use of over-the-counter preparations and alternative medicines.

Argyria attributed to silvadene application in a patient with dystrophic epidermolysis bullosa

Argyria is most commonly reported in association with prolonged ingestion of silver-containing medicaments. This case illustrates the rather unique case of development of argyria following application of silver sulfadiazine in a patient with epidermolysis bullosa.

Lack of toxicological side-effects in silver-coated megaprostheses in humans

Deep infection of megaprostheses remains a serious complication in orthopedic tumor surgery. Furthermore, reinfection gets a raising problem in revision surgery of patients suffering from infections associated with primary endoprosthetic replacement of the knee and hip joint. These patients will need many revision surgeries and in some cases even an amputation is inevitable. Silver-coated medical devices proved their effectiveness on reducing infections, but toxic side-effects concerning some silver applications have been described as well. Our study reports about a silver-coated megaprosthesis for the first time and can exclude side-effects of silver-coated orthopedic implants in humans. The silver-levels in the blood did not exceed 56.4 parts per billion (ppb) and can be considered as non-toxic. Additionally we could exclude significant changes in liver and kidney functions measured by laboratory values. Histopathologic examination of the periprosthetic environment in two patients showed no signs of foreign body granulomas or chronic inflammation, despite distant effective silver concentrations up to 1626 ppb directly related to the prosthetic surface. In conclusion the silver-coated megaprosthesis allowed a release of silver without showing any local or systemic side-effects.

Evaluation of the silver iontophoretic catheter in an animal model

Silver iontophoretic catheters (SIC) were shown to be highly efficacious in preventing catheter infections in vitro and in a rabbit model (J. Infect. Dis. 173 (1996) 495). Furthermore, we sought to determine the safety and durability of SIC prior to use in humans. A total of 30 New Zealand white rabbits (3-4 kg) were randomly assigned to one of three groups whereby SIC or Arrow Guard (AG) catheters were tunneled and inserted in the jugular vein. All animals were followed for 2-12 weeks after catheter implantation. Blood was collected from each rabbit for assessment of toxicity and determination of silver levels. The electrical current generated by each SIC was measured once daily. At the end of the follow-up period, tissue samples were collected from the skin surrounding the catheter, the lungs, spleen, and liver. Microscopically, none of the tissues examined from any of the animals showed evidence of silver deposits, silver toxicity, thermal or electrical injury. The silver levels in the animals that received the SIC ranged from 0.1 to 2.23 microg/l with a mean of 0.62 (+/-0.44 SD). In conclusion SIC were safe with normal serum silver levels and were not associated with any local or systemic toxicity.

Incidence of embolism and paravalvar leak after St Jude Silzone valve implantation: experience from the Cardiff Embolic Risk Factor Study

BACKGROUND

Silver coating of the sewing ring (Silzone) was introduced as a modification of the St Jude Medical standard valve to provide antibacterial protection, but the valve has recently been withdrawn.

OBJECTIVE

To study patients with these prostheses to assess possible adverse effects, and to guide their follow up.

DESIGN

Prospective observational study of risk factors for stroke after valve replacement.

SETTING

Cardiology and cardiac surgery departments in a tertiary centre.

PATIENTS

There were 51 patients with Silzone and 116 with St Jude Medical standard valves. Patients undergoing aortic valve replacement were well matched for stroke risk factors. Silzone patients with mitral valve replacement were younger (mean (SD) age 61 (10) v 66 (7) years), more likely to be female (95% v 65%), and had more pulmonary arterial hypertension (100% v 78%), but fewer coronary artery bypass grafts (5% v 33%) than patients with standard mitral valve replacements (all p < 0.05).

RESULTS

Follow up was 100% in the Silzone group (mean duration 3.0 (0.9) years) and 97.4% in the standard group (4.7 (1.4) years). Survival, morbidity, and anticoagulant control were documented over 682 follow up years (153 for Silzone and 529 for standard). There were six embolic strokes and one peripheral embolism in the Silzone group, all within three months after operation, and five embolic strokes and one peripheral embolism in the standard group. Freedom from major thromboembolism at three months was 65% in the Silzone mitral valve replacement group and 100% in the standard mitral valve replacement group (difference 35%, 95% confidence interval 8% to 62%). There was one reoperation for paravalvar leak in the standard group, but none in the Silzone group (NS). Anticoagulant control in the two groups was similar.

CONCLUSIONS

Patients with Silzone mitral valves had a high rate of early postoperative embolism but no excess paravalvar leak.

The distribution kinetics of waterborne silver-110m in juvenile rainbow trout

Juvenile rainbow trout (Oncorhynchus mykiss) were subjected to a 2-day radioactive pulse of 110mAg at 11.9 microg/l (as AgNO3), followed by a 19-day post-tracer exposure to non-radioactive Ag(I) (3.8 microg/l). The distribution of 110mAg in the gills, liver, intestine, kidney, brain and remaining carcass was investigated over a 19-day post-tracer period. Initially, the intestine contained the highest proportion of the 110mAg burden (34%), however, by day 8, less than 5% of the total radioactivity remained in this tissue. The majority of the 110mAg eliminated from the intestine appeared to distribute to the liver. Eventually, the 110mAg content in the liver accounted for as much as 65% of the total radioactivity in the fish. Apart from the liver and intestine, only the gills and carcass contained any appreciable amount (>5%) of the total body 110mAg content. Liver and gill samples were fractionated using differential centrifugation techniques to discern the subcellular distribution of 110mAg in these tissues. In the liver, the 110mAg levels in the cytosolic fraction increased from 35% to 72% of the total cellular burden between days 8 and 19, respectively. The radioactive pulse in the gills was predominantly found in a membrane compartment termed the nuclear fraction ( approximately 60% of the total). Little change was observed over time (day 8 to day 19) to the subcellular distribution of Ag in the gills. Using size-exclusion chromatography, most ( approximately 70%) of the 110mAg content in the liver cytosol eluted at a molecular weight characteristic of metallothionein. The cytosolic distribution of 110mAg in gills was quite diffuse, occurring primarily in the heavy molecular weight fractions.

[Increased serum and urinary levels of silver during treatment with topical silver sulfadiazine]

BACKGROUND

Argyria, induced by prolonged absorption, is often of professional or medical origin. We report two cases of per cutaneous intoxication with topical silver sulfadiazine.

CASE REPORTS

A 64 year-old hypertensive, diabetic woman presented bilateral venous ulcers on the legs. She had applied 100 g of silver sulfadiazine 1 p. 100 cream per week for the past 18 months. Silver concentration in blood high: 38 microgram/l (N<0.5) and led to renal dysfunction, without ocular or hepatic abnormality. A 19 year-old woman was treated with topical silver sulfadiazine for thermic cutaneous burns on legs. Renal and hepatic function was normal but silver concentration in blood was high at 440 microgram/l (N<0) with urinary excretion of silver at 12 microgram/l (N=0).

DISCUSSION

Silver, from prolonged and excessive use of topical silver sulfadiazine, deposits in large amounts throughout the body: skin, labial mucosa, gingiva, kidney, liver and cornea. Monitoring concentration of silver in blood and/or urine is necessary, especially in patients treated with silver sulfadiazine cream for cutaneous burns. Indeed, silver is rapidly absorbed through the burn wound. It provokes hepatic, renal and neurologic tissue toxicity. Renal and hepatic function tests are not correlated with serum silver levels.

CONCLUSION

The potential for silver toxicity is a direct consequence of applying silver sulfadiazine to extensive burn wounds. Hence monitoring concentrations of silver in blood and/or urine of patients receiving this treatment is recommended.

The physiological effects of a biologically incorporated silver diet on rainbow trout (Oncorhynchus mykiss)

Silver was biologically incorporated into a diet by exposing rainbow trout for 7 days to 100 mg/l of waterborne silver as silver thiosulphate. These fish were processed into a fine powder (trout meal) and pelleted to form a nutritionally balanced feed which was then fed to juvenile rainbow trout (Oncorhynchus mykiss). Fish were fed either a diet containing 3.1 microg/g biologically incorporated silver (an environmentally relevant concentration), or one of three control diets containing approximately 0.05 microg/g Ag for 128 days. All dietary treatments were fed to satiation once daily. Dietary silver did not significantly affect mortality, growth, food consumption, or food conversion efficiency. Furthermore, ion regulation (plasma Na(+) levels and Na(+) influx rates), hematological parameters (hematocrit, plasma protein, hemoglobin levels), plasma glucose, metabolism (oxygen consumption, ammonia and urea excretion rates) and intestinal Na/K-ATPase and amylase activities were all unaffected. Based on the physiological parameters investigated here, this dietary silver exposure appeared to be physiologically benign to rainbow trout. However, silver concentrations in the livers of the silver-fed fish were significantly elevated at day 16, and reached a steady-state level of approximately 20 microg/g Ag by day 36. The concentration specific accumulation rate in the livers of fish fed biologically incorporated silver was about 4.6 orders of magnitude greater than when fed dietary silver sulfide, indicating much greater bioavailability. Despite this increase, hepatic metallothionein concentrations remained unchanged, in contrast to waterborne exposures, indicating that bioaccumulated silver behaves differently depending on whether it is taken up from the diet or from the water. Apart from a significant reduction in hepatic Cu at day 16, liver concentrations of Cu and Zn were not affected by dietary silver. Silver concentrations were also significantly elevated (relative to control fish) in the kidneys of the silver-treated fish on days 88 and 126, and in the gills and plasma at day 126.

Pulmonary and systemic distribution of inhaled ultrafine silver particles in rats

The cardiovascular system is currently considered a target for particulate matter, especially for ultrafine particles. In addition to autonomic or cytokine mediated effects, the direct interaction of inhaled materials with the target tissue must be examined to understand the underlying mechanisms. In the first approach, pulmonary and systemic distribution of inhaled ultrafine elemental silver (EAg) particles was investigated on the basis of morphology and inductively coupled plasma mass spectrometry (ICP-MS) analysis. Rats were exposed for 6 hr at a concentration of 133 microg EAg m(3) (3 x 10(6) cm(3), 15 nm modal diameter) and were sacrificed on days 0, 1, 4, and 7. ICP-MS analysis showed that 1.7 microg Ag was found in the lungs immediately after the end of exposure. Amounts of Ag in the lungs decreased rapidly with time, and by day 7 only 4% of the initial burden remained. In the blood, significant amounts of Ag were detected on day 0 and thereafter decreased rapidly. In the liver, kidney, spleen, brain, and heart, low concentrations of Ag were observed. Nasal cavities, especially the posterior portion, and lung-associated lymph nodes showed relatively high concentrations of Ag. For comparison, rats received by intratracheal instillation either 150 microL aqueous solution of 7 microg silver nitrate (AgNO(3) (4.4 microg Ag) or 150 microL aqueous suspension of 50 microg agglomerated ultrafine EAg particles. A portion of the agglomerates remained undissolved in the alveolar macrophages and in the septum for at least 7 days. In contrast, rapid clearance of instilled water-soluble AgNO(3) from the lung was observed. These findings show that although instilled agglomerates of ultrafine EAg particles were retained in the lung, Ag was rapidly cleared from the lung after inhalation of ultrafine EAg particles, as well as after instillation of AgNO(3), and entered systemic pathways.

Argyria following the use of dietary supplements containing colloidal silver protein

The onset of argyria following the use of dietary supplements containing colloidal silver protein is presented. The patient was using a silver-containing product for cold and allergy prophylaxis. We review the past and present medicinal roles of silver and include a differential diagnosis for argyria. The hyperpigmentation of argyria is usually permanent, and it follows a sun-exposed distribution. This case report highlights the potential for toxicity following the use of dietary supplements and demonstrates the importance of physician inquiry regarding alternative medicines. Finally, we examine the limited role of the Food and Drug Administration (FDA) in regulating alternative medicines marketed as dietary supplements.

Prevention of pin track infection in external fixation with silver coated pins: clinical and microbiological results

Pin tract infection is a frequent complication of external fixation; according to literature its frequency ranges from 2-30%. The recent introduction of silver coating of polymeric materials was found to decrease bacterial adhesion; its clinical use with Foley catheters and central venous catheters led to significant results. To verify the ability of the same silver coating to decrease the bacterial colonization on external fixation screws, a prospective randomized study was carried out on 24 male patients; a total of 106 screws were implanted in the lower limb to fix femoral or tibial diaphyseal fractures: 50 were coated with silver and 56 were commercially available stainless steel screws. Although the coated screws resulted in a lower rate of positive cultures (30.0%) than the uncoated screws (42.9%), this difference was not statistically significant (p = 0.243). The clinical behavior of the coated screws did not differ from that of the uncoated ones. Furthermore, the implant of silver-coated screws resulted in a significant increase in the silver serum level. These results led us to consider it ethically unacceptable to continue this investigation.

Competition between copper and silver in Fischer rats with a normal copper metabolism and in Long-Evans Cinnamon rats with an abnormal copper metabolism

Long-Evans Cinnamon (LEC) rats inherently lacking in serum ceruloplasmin (CP) activity and biliary Cu excretion were established from a closed colony of Long-Evans rats. These deficiencies, linked to a dysfunction of P-type ATPase, stimulate deposition of Cu and then of Cu metallothionein (MT) in the liver. Male LEC and Fischer rats were injected subcutaneously with Ag (AgNO3), which is an antagonist to Cu. They were operated on 24 h after the injection while under anesthesia. Total uptake of Ag into the liver was not stimulated, but its uptake into the MT fraction increased significantly in the LEC rats. Ag injection notably decreased the activity of serum CP in the Fischer rats, but not in the LEC rats. The decrease was accompanied by a reduction of serum Cu. In Fischer rat serum treated with Ag, Ag was detected mainly in the albumin region and partly in the CP fraction. In LEC rat serum, however, the Ag concentration was about 1/20 of that in the Fischer rats, and Ag was not detected in the CP fraction. Ag injection decreased the biliary excretion of Cu in the Fischer rats (0.183-0.052 microg Cu/20 min sampling), but not in the LEC rats (0.014-0.014 microg Cu/20 min sampling). On the other hand, biliary excretion of Ag was much greater in the Fischer rats (1.25 microg Ag/20 min) than in the LEC rats (0.04 microg Ag/20 min). Our results suggest that uptake of Ag into the liver is not dependent on the hepatic Cu content and status, but that biliary excretion of Ag from the liver is affected by these. Hepatic MT is not a transporter of hepatobiliary excretion of Cu and Ag. It seems likely that, unlike Cu excretion, Ag is excreted by not only the CP route but also by another route into the serum. Ag may compete with Cu in the uptake into CP (conversion of apo-CP to holo-CP).

First clinical experience with a mechanical valve with silver coating

BACKGROUND AND AIM OF THE STUDY

The interface between the annulus and sewing cuff is the infectious center of prosthetic valve endocarditis (PVE). To decrease the incidence of PVE, the sewing cuff of the St. Jude Medical (SJM) mechanical heart valve was permanently coated with elemental silver (Silzone coating). In vitro data have supported the antimicrobial efficacy of this coating.

METHODS

To study any adverse effects of the silver coating in humans, serum silver levels were determined (by graphite furnace atomic absorption spectrometry) before (baseline) and at five intervals after operation: day 1, day 3, discharge, one month, and two months. Between January and August 1997, 38 patients (71% males) underwent surgical implant of a SJM Masters Series valve with Silzone coating for the aortic valve (n = 29), mitral valve (n = 6), or both valves (n = 3). Five patients (13%) underwent concomitant procedures. Two patients (5%) presented with native active valve endocarditis.

RESULTS

There was no hospital mortality or valve-related hospital morbidity. Blood silver concentrations peaked shortly after surgery and then decreased during the postoperative period. Average levels were consistently below 4 parts per billion (ppb). Levels below 10 ppb are considered normal. Follow up was 95% complete. There were no recurrent or new cases of endocarditis.

CONCLUSION

These clinical data indicate that the SJM Masters Series valve with Silzone coating performs well. No adverse effects of the silver coating could be detected, and there were no valve-related complications.

Longitudinal medical surveillance showing lack of progression of argyrosis in a silver refiner

Silver is a recognized cause of argyrosis and argyria. This case report describes blood silver levels and longitudinal ophthalmological examination in a previously reported case of argyrosis over a 5-year period.

Argyremia in septal cauterization with silver nitrate

OBJECTIVE

The purpose of this study was to demonstrate silver absorption in blood and hair specimens after septal cauterization with silver nitrate and to discuss the potential toxicity of silver.

METHOD

A prospective study of 11 volunteers without any known occupational exposure to silver products or past history of septal cauterization with silver nitrate was undertaken. Subjects were recruited in an academic tertiary care centre from October 1996 to September 1997. The study population consisted of five patients with anterior epistaxis and six healthy volunteers without any bleeding problem. Cauterization was done with one or two silver nitrate applicators directly on the bleeding vessel or Kiesselbach's area. Blood was sampled before cauterization and at specified times after application, while hair strands were sampled only 3 months later. Measurements of silver concentration in whole blood and in hair segments were obtained by inductively coupled plasma mass spectrometry.

RESULTS

Silver concentrations in whole blood increased significantly after cauterization (p = .02). The measured peak level seemed to correlate with the number of applicators used. No significant increase in silver concentration was observed in hair samples.

CONCLUSIONS

Effective silver absorption occurs with only one or two silver nitrate applicators. Hair has not been as reliable as whole blood to document an acute and fragmentary exposure. The indiscriminate use of silver nitrate is a potential source of silver intoxication.

A swine model for the evaluation of efficacy of anti-microbial catheter coatings

A swine model was developed to investigate the efficacy of percutaneous venous catheters with anti-microbial coatings. The catheters used in the study consisted of silver-coated and uncoated catheters, both designed for percutaneous venous access. Five commercial pigs were each implanted with three venous catheters and followed for a period of 90 days. Two of the three catheters were coated and one was uncoated. To evaluate the percutaneous aspects of the catheters in the model, two venous access catheters were implanted percutaneously, parallel to the dorsal midline. These catheters were just caudal to the region that is dorsal to the scapula in each animal. In each case, the catheter to the left of the dorsal midline was silver-coated while the catheter to the right of the dorsal midline was uncoated. A silver-coated catheter was also implanted in the left external jugular vein of each animal and buried subcutaneously in order to evaluate the elution of the coating through the body under venous contact. Over the 90 day period, the concentration of silver in the blood rose to a mean peak level of 23.2 ppb following implantation of the catheters and then decreased after the second post-surgery week. The histological evaluation and macroscopic inspection at necropsy revealed minimal tissue response to both coated and uncoated materials. Data on bacterial growth indicated that bacteria were present at the terminal subcutaneous end of two of the uncoated percutaneous catheters. Based upon serum silver levels, exudate formation, histological examination, and bacterial growth information, the swine model was deemed to be suitable for testing the efficacy of catheters containing anti-microbial coatings.

Biological interaction between transition metals (Ag, Cd and Hg), selenide/sulfide and selenoprotein P

The interaction between transition metals (Ag+, Cd2+ and Hg2+) and selenium (Se) in the bloodstream was studied in vitro by means of the HPLC--inductively coupled argon plasma-mass spectrometry (ICP MS) method. Transition metal ions and selenide (produced in vitro from selenite in the presence of glutathione) or sulfide (Na2S) formed a (metal-Se/S) complex, which then bound to a plasma protein, selenoprotein P (Sel P), to form a ternary complex, (metal-Se/S)-Sel P. The molar ratios of metals to Se were 1:1 for Hg/Se and Cd/Se, but either 1:1 or 2:1 for Ag/Se, depending on the ratio of their doses. The results indicate that the interaction between transition metals and Se occurs through the general mechanism, i.e., transition metal ions and selenide form the unit complex (metal-Se)n, and then the complex binds to selenoprotein P to form the ternary complex ¿(metal-Se)n¿m--seleno-protein P in the bloodstream.

Silver modification of polyethylene terephthalate textiles for antimicrobial protection

The safety and in vitro effectiveness of applying silver to polyethylene terephthalate fabric mechanical heart valve (MHV) sewing cuffs for the prevention of prosthetic valve endocarditis (PVE) were evaluated. PVE is an infrequent but grave complication of cardiac surgery associated with mortality rates potentially exceeding 50%. A poor response to antibiotic therapy is partly responsible for the high mortality rates. Silver is a well known antimicrobial agent with broad effectiveness. Preliminary in vitro microbial challenge studies of the coated fabric using the New York State 63 bacteriostatic test and Dow Corning Shake Flask test showed a > or = 97% reduction for most organisms tested. Sheep mitral valve replacement studies suggest comparable tissue ingrowth of uncoated and coated fabric with a more organized, thinner pannus formed on silver coated fabric. Low levels of silver were present in the serum at all time periods. These results indicate MHVs with silver coated cuffs may provide additional protection against PVE.

[General argyria caused by administration of tobacco-withdrawal tablets containing silver acetate]

In a 49-year-old man generalised argyria was diagnosed, a systemic dissemination and tissue deposition of silver in the body. The clinical picture was brought about by use of a silver acetate-containing lozenge as a deterrent to smoking. Argyria is characterised by a slate blue-gray discolouration of the skin, particularly in areas exposed to light. Generally, it causes patients a great deal of anguish and embarrassment. Present understanding is that it does not entail non-cutaneous, systemic effects. There is no effective treatment--the discolouration is permanent. Currently, prevention is the only possible measure. Efforts should be made to eliminate the uncontrolled use of silver-containing preparations.

Absence of symptoms in silver refiners with raised blood silver levels

Silver has been implicated as a cause of ill health, related largely to its use in the medical setting as a treatment for burns and in prosthetic cements. This report discusses occupational silver exposure in two workers with blood silver levels of 49 micrograms/l and 74 micrograms/l who were asymptomatic and showed no signs of argyric neuropathy which has previously been described at blood silver levels as low as 10 micrograms/l. One of the men showed non-characteristic clinical signs of argyrosis. The clinical findings, results of environmental monitoring and effects of environmental improvements on blood silver levels are discussed.

Solubility of silver sulfadiazine in physiological media and relevance to treatment of thermal burns with silver sulfadiazine cream

Silver sulfadiazine cream has been a standard treatment for burns over the past two decades. Although many studies have described the phenomenon of silver absorption from burn wounds treated with silver sulfadiazine, they failed to examine the chemistry underlying the absorption process: Silver chloride was assumed to form at the burn wound and absorption of silver was believed to be negligible. Here we have developed chemical model systems to investigate the interactions of silver sulfadiazine and silver chloride in direct contact with synthetic serum electrolyte solution (SSES), with SSES plus endogenous ligands or beef blood plasma, and with human serum. The results indicate that silver absorption from an acute burn site can be significant, because human serum is capable of solubilizing silver. This finding is of concern, given the potential for silver toxicity as a direct consequence of applying silver sulfadiazine to extensive burn wounds.

Determination of silver in blood, urine, and tissues of volunteers and burn patients

Silver sulfadiazine cream (SSD) has been used successfully in the management of burn wound sepsis. Silver deposition has been found in the skin, gingiva, cornea, liver, and kidney of patients treated with this cream, causing argyria, ocular injury, leukopenia, and toxicity in kidney, liver, and neurologic tissues. Monitoring concentrations of silver in blood and urine of patients receiving this treatment has become necessary, but sensitive and suitable methods adaptable to a clinical laboratory are still needed. We have developed a flameless thermal atomic absorption spectrophotometric method to measure silver concentrations in blood, urine, and other tissues. The detection limit is 0.4 microgram/L; the within-run precisions (CV) are 5.16%, 3.83%, and 2.79% for concentrations of 5, 13.5, and 42 micrograms/L, respectively; and the between-run precisions are 4.3% and 3.2% for concentrations of 13.5 and 42 micrograms/L. The concentrations of silver in blood, urine, liver, and kidney of subjects without industrial or medicinal exposure are less than 2.3 micrograms/L, 2 micrograms/day, 0.05 microgram/g wet tissue, and 0.05 microgram/g wet tissue, respectively. In SSD cream-treated burn patients, plasma concentrations may be as great as 50 micrograms/L within 6 h of treatment and can reach a maximum of 310 micrograms/L. Silver in urine is detectable after one day of treatment and may reach a maximum of 400 micrograms/day. After absorption, silver was found to be deposited in various tissues. Tissue silver concentrations in one burn patient who died of renal failure after eight days of treatment were 970, 14, and 0.2 micrograms/g wet tissue in cornea, liver, and kidney, respectively.

Serum sulfate concentration and the anion gap in hemodialysis patients

First-of-the-month predialysis serum sulfate (SO4) and other blood chemistry values were measured prospectively for 5 to 7 months in 14 patients undergoing single pass chronic tri-weekly maintenance hemodialysis with bicarbonate dialysate. Blood was also obtained predialysis and again immediately postdialysis from seven patients (five of whom also participated in the chronic study). As expected, the patients manifested a high anion gap (AG) metabolic acidosis. Serum SO4 was only moderately stable from month to month (the average coefficient of variation was 0.30; correlation between the serum SO4 value of month one and months two and five were r = 0.59, p = 0.026; and r = 0.38, p = 0.182, respectively). The ratio of mean serum SO4 to mean AG (5.0 +/- 0.4 [SE] mEq/L divided by 19.1 +/- 0.5 mEq/L) was 0.26. Although there was a statistically significant correlation between the serum SO4 and the blood urea nitrogen (BUN), there was no such correlation between SO4 and AG. A single hemodialysis reduced serum SO4 by 54% (from 3.5 +/- 0.5 mEq/L to 1.6 +/- 0.1 mEq/L), but there was no correlation between the change in SO4 and the change in AG. The authors concluded that SO4 contributes importantly to the elevated AG in patients receiving chronic hemodialysis. Single pass bicarbonate hemodialysis temporarily reduces, but does not normalize, both the serum SO4 and the AG of such patients.

[Serum and tissue silver levels after burns treated with silver compounds]

This study was performed in order to investigate serum and tissue silver levels in burns which were used 10 percent silver nitrate as a topical agent. We formed four groups of animals and pulverized 10 percent silver nitrate solution to the first group (GI) that included ten rabbits of which backs were burned by boiling water and silver sulphadiazine cream to second group (GII) with nine rabbits. We carried out 10 percent silver nitrate solution to the first control group (GIII) and silver sulphadiazine cream to the second control group (GIV) each of which had seven animals with unburned skin. We obtained blood samples from every animal before and after application of topical agent on the 1st, 3rd, 7th, 15th, 21st and 28th. We determined serum and tissue silver levels by atomic absorption spectrophotometer in kidney and liver of the animals which were sacrificed on the 28th day. In first and second groups we found that serum silver values reached on 3rd day to the maximum level and then the values decreased gradually. We also determined that diminution of the serum silver levels were prominent following on 15th day. It was shown that there was no silver in the serum on 28th day except four animals. The silver deposition in the liver was much more than in the kidney. Between these two groups there was significant difference neither in the serum on the same days nor the tissue silver levels. According to these data it was concluded that serum and tissue silver levels with 10 percent silver nitrate used in burns produced no difference from that of 1 percent silver sulphadiazine cream.

Results of a multicenter outpatient burn study on the safety and efficacy of Dimac-SSD, a new delivery system for silver sulfadiazine

Dimac with silver sulfadiazine (Dimac-SSD), a new silver sulfadiazine delivery system, was evaluated prospectively in a multicenter study for the treatment of outpatient burn injuries. The goal of this study was to evaluate the effect of Dimac-SSD on the microbiology of the burn wounds and to quantitate its clinical safety and efficacy. A total of 197 patients were evaluated. Eight (4%) of these patients did not complete the study. Six patients withdrew because of local discomfort caused by the Dimac-SSD and two patients were terminated because of technical problems. The mean +/- SD duration of treatment with Dimac-SSD was 12 +/- 8.5 days, during which time the mean number of dressing changes was 2.9 per patient. During treatment with Dimac-SSD, the burn wound bacterial flora remained stable and overgrowth with Pseudomonas species or Gram-negative bacilli did not occur. Only four (2%) patients developed clinical infections; thus the Dimac-SSD appeared to have good antimicrobial effectiveness. This dressing was not associated with any organ system or metabolic side-effects and patient discomfort during application and removal was minimal. Thus this new delivery system for silver sulfadiazine was associated with excellent wound healing, a low incidence of wound infections, reduced frequency for dressing changes, and excellent patient compliance.

Serum concentrations and accumulation of silver in skin during three months treatment with an anti-smoking chewing gum containing silver acetate

Silver acetate chewing gum was used for 12 weeks as a smoking deterrent in 21 adults. The effect of silver on serum concentrations, its accumulation in the skin and the risk of developing clinically evident argyria were investigated. Serum concentrations of silver clearly rose after chewing gum use had started, and concentrations quickly returned to normal after use had ceased. In most cases the number of silver granules in skin biopsies, observed by autometallography, increased after the gum had been used for 12 weeks. No one developed clinical signs of argyria. Silver acetate containing remedies can be used as an aid to stop smoking, but the consumption must be monitored to avoid accumulation of larger amounts of silver in the body.

[Argyria. A clinical, chemical analytic and micromorphologic study]

A 62-year-old male patient developed generalized argyria following the intake of silver-proteinacetyltannate (Targesin; approx. 60 g in 10 years) as treatment for gastric discomfort. On histological and ultrastructural examination of the skin, silver particles were found not only in the usual locations but also in the Schwann cell, the mast cell, and in smooth muscle cells. This corresponded to chemical analysis, proving the presence of this metal in the skin. In the blood, a level of 0.26 +/- 0.04 ppm silver was found. By means of an equation, attempts were made to demonstrate the reaction process involved in the formation of Ag2S as subjected to the photochemical effect of sunlight.

Relationship between ceruloplasmin and Cu status involving metallothionein induced by several heavy metals in the mouse

ICR male mice aged 5 weeks were injected subcutaneously with CdCl2, Pb(CH3COO)2, AgNO3, CuCl2, a combination of Cd and Ag compounds, or a combination of Cu and Ag compounds. These injections were carried out 3 times. Twenty-four hours after the last injection, they were sacrificed. Cd injection significantly stimulated serum ceruloplasmin (Cp) activity and Cu concentration, accompanied by an increase in hepatic Cu. Pb injection also slightly increased the Cp level. In contrast, Ag injection markedly decreased both Cp activity and Cu concentration in the serum. Hepatic Cu increased slightly after Ag injection. Using a combination of Cd and Ag, only the Ag effect on the Cp activity appeared. The Cu injection stimulated Cu binding to metallothionein (MT) and bile excretion of Cu, but not Cp release. With a Cu and Ag combination, the effect of Ag on Cp was lost, with a concomitant disappearance of Ag from the Cp fraction in the serum. Our results suggest that in the mouse, Cd and Ag, Cu antagonistic metals, influence different sites of Cp metabolism. Excess hepatic Cu is partly eliminated by excretion of bile and is partly detoxified by MT induction.

Determination of silver in biological samples using graphite furnace atomic absorption spectrometry based on Zeeman effect background correction and matrix modification

A method for the determination of silver in human body fluids and biological material is described. The silver in an acid digest of biological samples and diluted body fluids is quantified using Zeeman graphite furnace atomic absorption spectrometry (ZGFAAS). The effects of NH4H2PO4 as matrix modifier and standard addition are discussed. Atomization from the graphite tube wall and from the pyrolytical tube with platform is also discussed and the peak height and the peak area are compared. The best results were achieved by using matrix modification, stabilized temperature platform furnace, integrated absorbance and standard addition technique. The calibration was linear up to 15 micrograms X L-1; the between-run precision was 5.9% at 40 micrograms X kg-1 of silver.

Comparative study of effect of acute administration of cadmium and silver on ceruloplasmin and metallothionein: involvement of disposition of copper, iron, and zinc

Male ICR mice were subcutaneously injected with either aqueous Ag (1.5 or 5.0 mg/kg) or Cd (1.5 or 2.5 mg/kg) for 2 consecutive days. Body fluids and livers were collected 24 hr after the second dose. In the hepatic supernatant, Ag and Cd were recovered at 2 and 36-46% of the total dose, respectively. Ag-metallothionein (MT), which is associated with Ag, Cu, and Zn, and Cd-MT, which is associated with Cd, Cu, and Zn, were induced in the liver by the injection of Ag and Cd, respectively. The supernatant Ag and Cd existed in the MT fraction at 34-61 and 97% levels, respectively. Cu concentration in the hepatic supernatant was increased by the Ag and Cd injections. The increased Cu was due to the appearance of Ag-MT and Cd-MT, respectively. Microsomal concentrations of Cu increased in the Cd groups, but decreased in the Ag groups. Serum ceruloplasmin (Cp) activity was remarkably increased by the injection of Cd, but severely decreased by the injection of Ag. These opposing changes in Cp activity induced by Cd and Ag may be due not to the sequestering of Cu in MT, but to the alteration of microsomal Cu concentration and/or the difference in affinity of the induction metals to MT. Hepatic Fe concentration was increased by the Ag injection, but was decreased by the Cd injection. These changes may not be related to induction of MT, but to Cp synthesis in the liver.

Evidence for carriage of silver by sulphadimidine: haemolysis of human erythrocytes

1 Human erythrocytes suspended in isotonic saline haemolyse in the presence of both Ag+ ions and sulphadimidine. 2 Neither Ag+ ions nor sulphadimidine on their own will haemolyse erythrocytes suspended in isotonic saline. 3 At constant Ag+ ion concentration the degree of haemolysis of saline-suspended erythrocytes depends upon the concentration of sulphadimidine. 4 Human erythrocytes suspended in isotonic sucrose (chloride-free) haemolyse in the presence of Ag+ ions. 5 Sulphadimidine in chloride-free sucrose competes with erythrocytes for Ag+ ions resulting in stoichiometric protection of the erythrocytes from the haemolytic action of Ag+ ions. 6 Haemolysis occurs when each erythrocyte receives approximately 1.2 X 10(9) Ag+ ions whether suspended in saline or sucrose. 7 Sulphadimidine acts as a carrier for Ag+ ions and so prevents their precipitation as AgCl when erythrocytes are suspended in saline.

Evidence for the carriage of silver by sulphadimidine: inhibition of proteolytic enzymes

1 Trypsin in free solution and trypsin-sepharose were shown to be inhibited by Ag+ in the absence of Cl-. 2 In the presence of Cl- and absence of a suitable carrier, Ag+ has no inhibitory action on trypsin or chymotrypsin. 3 Sulphadimidine bound Ag+ in the presence of Cl-, and carried the Ag+ to both trypsin and chymotrypsin in free solution as well as to trypsin-sepharose leading to the inhibition of all these enzyme systems. 4 The neutral protease of tumour cell surfaces was inhibited by Ag+ transported by sulphadimidine in the presence of Cl-. 5 Kinetic data demonstrated the requirements for both Ag+ and carrier to effect inhibition, the degree of inhibition being directly related to the molarity of each of these reagents. 6 The known inhibition of trypsin by Ag+ binding to histidine in the active site has been defined in mechanistic terms employing the sulphonamide drug, sulphadimidine, to illustrate this exchange mechanism.

Serum levels of certain trace elements (Ag, Co, Cr) in healthy subjects (part II)

In 95 healthy subjects including 55 women and 40 men the serum levels of Ag, Co and Cr were determined by means of neutron activation analysis using the method of gamma spectrometry without separation of different elements from the sample. It was found that people aged over 60 years had higher serum silver levels than younger subjects. In women a statistically significantly higher serum cobalt level was demonstrated in relation to men. Men and women aged over 60 years had serum chromium levels very similar while women aged below 60 years had lower serum chromium levels.

Control of experimental burn wound infections: comparative delivery of the antimicrobial agent (silver sulfadiazine) either from a cream base or from a solid synthetic dressing

This report demonstrates prolonged effective release of silver sulfadiazine (AgSD) to experimental burns in rats from a solid dressing by mixtures of polyethylene glycol-400 and poly-2-hydroxyethyl methacrylate. The synthetic dressing, incorporating the antimicrobial drug, may be formed either directly on the burn wound or prepared as a preformed sheet and applied to the wound after it was contaminated with bacteria. The level of silver in the blood following treatment of the burn wound with topical AgSD (Silvadene, Marion Labs) is significantly less when the drug is presented in the dressing than when the drug is applied in a cream base; the concentration of the sulfadiazine moiety in the blood is similar for the two drug preparations. Improved survival of the burned and contaminated rats and reduced nursing care were observed in the burned animals when the synthetic dressing was used to deliver the drug relative to the results when the AgSD was applied in a cream base by standard procedures.

The ocular manifestations and functional effects of occupational argyrosis

Thirty employees of an industrial plant involved in the manufacture of silver nitrate and silver oxide underwent ophthalmologic evaluation in an effort to evaluate the frequency and extent of ocular argyrosis. The most frequently noted ocular abnormality was pigmentation of the conjunctiva, present in 20 workers; corneal pigmentation occurred in 15 workers. A direct relationship existed between the levels of pigmentation and duration of employment. Ocular pigmentation was seen more frequently than cutaneous pigmentation. Ten workers noted decreased night vision, but electrophysiologic and psychophysiologic studies of seven of these ten workers demonstrated no functional deficits.

Elemental composition of platelets. Part III. Determination of Ag, Au, Cd, Co, Cr, Cs, Mo, Rb, Sb, and Se in normal human platelets by neutron activation analysis

The elements Ag, Au, Cd, Co, Cr, Cs, Mo, Rb, Sb, and Se were determined in platelets from seven normal donors. The results, in ng/g wet weight, for plasma-free platelets follow: "Pure" platelets: Ag = 29 +/- (18), au = 0.22 +/- (0.22), Cd = 6.2 +/- 3.4, Cs = 54.8 +/- 19.2, Cr = 6.1 +/- 2.5, Co = 7.5 +/- (5.0), Mo = 3.4 +/- 1.3, Rb = 10400 +/- 3000, Sb = 18 +/- (26), and Se = 782 +/- 127. "Impure" platelets: Au = 0.23 +/- (0.28), Cd = 6.4 +/- 2.6, Cs = 35.2 +/- 13.8, Cr = 8.2 +/- 2.9, Co = 2.9 +/- (3.0), Mo = 3.2 +/- 0.8, Rb = 8700 +/- 1700, Sb = 13.2 +/- (8.7), and Se = 679 +/- 57. To our knowledge, none of these 10 trace elements has been determined in platelets before. The selenium concentration in platelets exceeds that in other tissues (e.g., liver). We suggest that glutathione peroxidase or other unknown selenoenzymes are particularly important in platelet metabolism. Platelets are crucial for triggering thrombosis, and so may be involved as links between selenium deficiency and the concomitant increased death rate from cardiovascular disease.