Effects of mycogenic silver nanoparticles on organisms of different trophic levels.

Biogenic silver nanoparticles (AgNPs) are considered a promising alternative to their synthetic versions. However, the environmental impact of such nanomaterials is still scarcely understood. Thus, the present study aims at assessing the antimicrobial action and ecotoxicity of AgNPs biosynthesized by the fungus Aspergillus niger IBCLP20 towards three freshwater organisms: Chlorella vulgaris, Daphnia similis, and Danio rerio (zebrafish). AgNPs IBCLP20 showed antibacterial action against Klebsiella pneumoniae between 5 and 100 µg mL-1, and antifungal action against Trichophyton mentagrophytes in concentrations ranging from 20 to 100 µg mL-1. The cell density of the microalgae Chlorella vulgaris decreased 40% after 96 h of exposure to AgNPs IBCLP20, at the highest concentration analysed (100 µg L-1). The 48 h median lethal concentration for Daphnia similis was estimated as 4.06 µg L-1 (2.29-6.42 µg L-1). AgNPs IBCLP20 and silver nitrate (AgNO3) caused no acute toxicity on adult zebrafish, although they did induce several physiological changes. Mycosynthetized AgNPs caused a significant increase (p < 0.05) in oxygen consumption at the highest concentration studied (75 µg L-1) and an increase in the excretion of ammonia at the lower concentrations, followed by a reduction at the higher concentrations. Such findings are comparable with AgNO3, which increased the oxygen consumption on low exposure concentrations, followed by a decrease at the high tested concentrations, while impairing the excretion of ammonia in all tested concentrations. The present results show that AgNPs IBCLP20 have biocidal properties. Mycogenic AgNPs induce adverse effects on organisms of different trophic levels and understanding their impact is detrimental to developing countermeasures aimed at preventing any negative environmental effects of such novel materials.

Exogenous pigmentation by silver nitrate: Dermatological and toxicological aspects, case report / [Pigmentación exógena por nitrato de plata: aspectos dermatológicos y toxicológicos, a propósito de un caso].

Exogenous pigmentation by silver nitrate is a rare disease whose clinical manifestations appear even years after the contact, making its diagnosis difficult on occasions. It is characterized by the presence of blue-gray macules or plaques on the skin or mucosa in the contact area, sometimes very similar to melanocytic lesions and melanoma, which constitute the main differential diagnosis. We report the case of a male patient from Medellín, Colombia, with a family history of melanoma and the presence of these lesions throughout his body.

La pigmentación exógena por nitrato de plata es una enfermedad poco frecuente, cuyas manifestaciones clínicas pueden aparecer años después del contacto, lo que en ocasiones dificulta su diagnóstico. Se caracteriza por la presencia de máculas o placas azul-grisáceas en la piel o las mucosas de la zona de contacto que, en ocasiones, son muy similares a las lesiones melanocíticas y al melanoma, sus principales diagnósticos diferenciales. Se reporta el caso de un paciente de Medellín, Colombia, con antecedentes familiares de melanoma y presencia de estas lesiones en todo el cuerpo.

Nanosilver and Silver Nitrate Toxicity in Ex Vivo-Exposed Gills of Fish and Mitigation by Humic Acids.

Silver nanoparticles (AgNP) are unique because of their biocide properties. Once released to environment, AgNP interact with the natural organic matter which impact on their fate, dispersion, and ultimate toxicity. We carried out an ex vivo exposure of gill of Corydoras paleatus fish to 100 µg L-1 of AgNP or AgNO3, alone and in combination with 10 mg L-1 of humic acids (HA), with the aim to evaluate the potential mitigation of HA on AgNP toxic effects. We analyzed Ag accumulation and oxidative stress biomarkers. The results showed high bioaccumulation after the AgNO3+HA exposure. An inhibition of glutathione-S-transferase enzymatic activity and depletion of reduced glutathione levels were registered after the AgNO3 exposure, and increased lipid peroxidation levels in the case of AgNP one. Oxidative responses were mitigated when the HA were present in the media. Overall, the knowledge about the fate of this emergent pollutant was deepened through this study.

Silver serum levels in burned patients treated with silver sulfadiazine and its toxicity on inflammatory cells.

BACKGROUND: Silver sulfadiazine (SSD) has been widely used in burned patients for the prevention of local infections. To be biologically active and exert antimicrobial properties, silver needs to be present in the form of silver ions (Ag1+) that bind to negatively charged proteins, namely, the RNA and DNA in microorganisms. However, previous published studies conducted with SSD in the 1990s reported a high level of silver absorption through damaged skin and noted the potential cytotoxicity of Ag1+ to human cells. SSD toxicity, however, had been described in cell cultures using arbitrary silver concentrations. In the present study, we determined the serum silver levels in burned patients treated with SSD and, taking into account the molar Ag1+ concentrations found in these patients, we evaluated the Ag1+ toxicity effects on inflammatory cells (ROS and cytokine production) in vitro. METHODS: Twenty patients with an average burned body surface area of 27.68% were included in this study. RESULTS: Patients' Ag1+ serum levels reached up to 558 times those of the unexposed controls. Ag1+ was then added to inflammatory cells in vitro at levels up to 2000 times the level of the control, and there was no effect on the viability of the cells nor on the rate of apoptosis. We observed a decrease in reactive oxygen species production by mononuclear (MN) and polymorphonuclear (PMN) cells, as well as a substantial decrease in cytokines IL-1ß, IL-6, IL-8, IL-10, and TNF-α production by leukocytes (MN and PNM). CONCLUSION: These findings suggest that Ag1+ may contribute to negative outcomes after burns, decreasing the primary defense mechanism (respiratory burst) and altering cytokine production.

Antibacterial Activity of combinatorial treatments composed of transition-metal/antibiotics against Mycobacterium tuberculosis.

Notwithstanding evidence that tuberculosis (TB) is declining, one of the greatest concerns to public health is the emergence and spread of multi-drug resistant strains of Mycobacterium tuberculosis (MDR-TB). MDR-TB are defined as strains which are resistant to at least isoniazid (INH) and rifampicin, the two most potent TB drugs, and their increasing incidence is a serious concern. Recently, notable efforts have been spent on research to pursue novel treatments against MDR-TB, especially on synergistic drug combinations as they have the potential to improve TB treatment. Our research group has previously reported promising synergistic antimicrobial effects between transition-metal compounds and antibiotics in Gram-negative and Gram-positive bacteria. In this work, we evaluated antimycobacterial activity of transition-metals/antibiotics combinatorial treatments against first-line drug resistant strains of Mycobacterium tuberculosis. Our data showed that INH/AgNO3 combinatorial treatment had an additive effect (bactericidal activity) in an isoniazid-resistant clinical strain of Mycobacterium tuberculosis. Moreover, in vitro evaluation of cytotoxicity induced by both, the individual tratments of AgNO3 and INH and the combinatorial treatment of INH/AgNO3 in murine RAW 264.7 macrophages and human A549 lung cells; showed no toxic effects. Together, this data suggests that the INH/AgNO3 combinatorial treatment could be used in the development of new strategies to treat resistant strains of Mycobacterium tuberculosis.

Knowledge and practice of nursing professionals about prophylaxis of ophthalmia neonatorum / Conocimiento y la práctica de profesionales de enfermería sobre profilaxis de la oftalmía neonatal / Conhecimento e prática de profissionais de enfermagem sobre profilaxia da oftalmia neonatal

Abstract Objective: To analyze the knowledge and practice of nursing professionals about the prophylaxis of ophthalmia neonatorum. Method: Descriptive study, of qualitative approach, carried out in the first semester of 2018, in a city hall hospital located in the lake area of the Rio de Janeiro's state, through semi-structured interviews with 14 Nursing professionals participating in the care of the newborn, whose data were submitted to the Thematic Analysis. Results: From the three emerging thematic categories, there are gaps in knowledge related to ophthalmia neonatorum, silver nitrate and the instillation procedure of this prophylactic solution, as well as differences in care practice regarding care before, during and after the procedure. Conclusion and implications for practice: The data point to the importance of training the Nursing team in the prophylaxis of ophthalmia neonatorum, the revision of guidelines and procedures aimed at standardizing the procedure, as well as emphasizing the need for adequate follow-up of pregnant women in prenatal care.

Resumen Objetivo: Analizar el conocimiento y la práctica de los profesionales de Enfermería sobre la profilaxis de la oftalmía neonatal. Método: Estudio descriptivo, de naturaleza cualitativa, realizado en el primer semestre de 2018, en un hospital municipal ubicado en la bajada costera del estado de Río de Janeiro, a través de entrevistas semiestructuradas desarrolladas con 14 profesionales de Enfermería, que participan en la asistencia al recién nacido, cuyos datos se sometieron al análisis temático. Resultados: A partir de las tres categorías temáticas emergentes se evidencian lagunas en el conocimiento relacionadas a la oftalmía neonatal, al nitrato de plata y al procedimiento de instilación de esa solución profiláctica, además de divergencias en la práctica asistencial en cuanto a los cuidados antes, durante y después de la realización del procedimiento. Conclusión y las implicaciones para la práctica: Los datos apuntan a la importancia de la capacitación del equipo de Enfermería para la realización de la profilaxis de la oftalmia neonatal, de la revisión de directrices y conductas que visen la estandarización del procedimiento, además de resaltar la necesidad de un acompañamiento adecuado de las gestantes en el prenatal.

Resumo Objetivo: Analisar o conhecimento e a prática de profissionais de Enfermagem sobre profilaxia da oftalmia neonatal. Método: Estudo descritivo, de natureza qualitativa, realizado no primeiro semestre de 2018, em um hospital municipal localizado na baixada litorânea do estado do Rio de Janeiro, por meio de entrevistas semiestruturadas com 14 profissionais de Enfermagem, que participam da assistência ao recém-nascido, cujos dados foram submetidos à Análise Temática. Resultados: A partir das três categorias temáticas emergentes evidenciaram-se lacunas no conhecimento relacionadas à oftalmia neonatal, ao nitrato de prata e ao procedimento de instilação dessa solução profilática, além de divergências na prática assistencial quanto aos cuidados antes, durante e após a realização do procedimento. Conclusão e implicações para a prática: Os dados apontam para a importância da capacitação da equipe de Enfermagem para a realização da profilaxia da oftalmia neonatal, da revisão de diretrizes e condutas que visem a padronização do procedimento, além de ressaltar a necessidade de um acompanhamento adequado das gestantes no pré-natal.

Responses to silver nanoparticles and silver nitrate in a battery of biomarkers measured in coelomocytes and in target tissues of Eisenia fetida earthworms.

The current use and development of applications with silver nanoparticles (Ag NPs) could lead to potential inputs of these NPs to soils. Consequently, it is crucial to understand the ecotoxicological risks posed by Ag NPs in the terrestrial compartment. In the present investigation, the effects produced by PVP-PEI coated Ag NPs were assessed in Eisenia fetida earthworms in comparison with the soluble form (AgNO3). Earthworms were exposed for 1, 3 and 14 days to a range of sublethal concentrations of Ag (0, 0.05 and 50mg/kg) and at each exposure time, apart from mortality and weight loss of individuals, metallothionein (MT) protein concentration and catalase (CAT) activity were quantified in earthworm tissues. In addition, cellular and molecular level endpoints (cell viability, absolute and relative trophic indices and transcription levels of catalase-cat- and metallothionein-mt-) were measured in coelomocytes extruded from exposed earthworms. Despite the lack of effects in traditional endpoints (mortality and weight loss), Ag NPs and AgNO3 posed changes at lower levels of biological complexity (biochemical, cellular and molecular levels). Both Ag forms induced similar changes in the metal detoxification mechanism (MT, mt) and in the antioxidant response system (CAT, cat) of E. fetida. In contrast, Ag form dependant cytotoxicity and subpopulation ratio alterations (eleocytes/amoebocytes) were recorded in extruded coelomocytes. Complementarily, the use of coelomocytes to assess molecular level endpoints represented a relevant alternative for development of non-invasive biomarkers.

Acute silver toxicity to Cnesterodon decemmaculatus (Pisces: Poeciliidae) in a river with extreme water-quality characteristics / Toxicidad aguda de la plata sobre Cnesterodon decemmaculatus (Pisces: Poeciliidae) en un río con características extremas de calidad de agua

Abstract. A 96 h acute silver toxicity test was performed in order to determine silver toxicity (LC50) to a local fish species (Cnesterodon decemmaculatus) in a river with extreme water-quality characteristics (Pilcomayo River, South America) and evaluate a cross-fish-species extrapolation of the Biotic Ligand Model. The dissolved silver concentrations tested were 0.095, 0.148, 0.175 and 0.285 mg Ag L−1. The 96 h Ag LC50 calculated for C. decemmaculatus was 0.14 mg L−1 (0.18 - 0.10) and the value predicted by BLM for Pimephales promelas was 0.051 mg Ag L−1. Test water elevated hardness may have exerted some protective effect. High mean water pH may have exerted a major protective effect by reducing silver free ion form and causing silver precipitation. The mortality pattern observed in this toxicity test may lend some support to a relationship between gill silver accumulation and mortality. A cross-fish-species extrapolation of Ag BLM for P. promelas was not valid in Pilcomayo River water and experimental conditions of this toxicity test.

Con el objeto de determinar la toxicidad de la plata en un pez nativo (Cnesterodon decemmaculatus), se llevó a cabo un ensayo estático de toxicidad aguda a 96 horas en un agua natural con características de calidad de agua, extremas (río Pilcomayo, Sudamérica). Asimismo, se evaluó una posible extrapolación inter-especie del Modelo del Ligando Biótico en el agua experimental. La concentración inicial de plata en solución en los distintos tratamientos fue de 0,095; 0,148; 0,175 y 0,285 mg Ag L −1 . La CL50 a las 96 horas calculada para C. decemmaculatus fue de 0,14 (0.18 - 0.10) mg Ag L−1 y el valor predicho por el BLM para Pimephales promelas fue de 0,051 mg Ag L−1. La elevada dureza del agua experimental pudo haber tenido algún efecto protector frente a la toxicidad de la plata. El valor medio de pH del ensayo fue elevado y posiblemente tuvo un gran efecto protector por reducción de la forma iónica libre y precipitación del metal. El patrón de mortalidad observado en este ensayo de toxicidad apoyaría la relación causa-efecto entre acumulación de plata en las branquias y mortalidad. La extrapolación inter-especie del BLM para P. promelas no resultó válida en el agua del río Pilcomayo y en las condiciones experimentales de este ensayo.

Mechanism of acute silver toxicity in Daphnia magna.

Daphnids (Daphnia magna) were exposed to AgNO3 at 0.303 +/- 0.017 microg silver/L (46.9% as Ag+), in the absence of food, in moderately hard synthetic water under static conditions for up to 48 h. Results from accumulation experiments demonstrated that silver body burden was inversely related to body mass. Daphnids exposed to silver exhibited ionoregulatory disturbance, which was characterized by decreases in whole-body sodium concentration. This ionoregulatory disturbance was explained, at least in part, by a competitive inhibition of the whole-body sodium uptake (six- to sevenfold increase in the Michaelis constant with no change in maximal velocity), which was complete by 1 h of exposure, and resulted in approximately 40% inhibition of sodium influx from the water. A rapidly developing inhibition of whole-body Na+,K(+)-dependent adenosine triphosphatase (Na+,K(+)-ATPase) activity, significant by 2 h and complete at 90% blockade by 12 h, also was observed during exposure to AgNO3. Therefore, these findings clearly demonstrate that the key mechanism involved in acute Ag+ toxicity in D. magna, the most sensitive freshwater organism tested to date, resembles that described for freshwater fish--that is, inhibition of active sodium uptake by blockade of Na+,K(+)-ATPase. Furthermore, the results showed that Na+,K(+)-ATPase inhibition was directly related to silver accumulation in the whole body of D. magna. However, the nature of the sodium uptake inhibition (competitive vs noncompetitive in fish) and the fact that whole-body chloride concentration was not disturbed in daphnids was different from fish. With regard to the biotic ligand model (BLM) for silver, our results yielded a log K value of about 8.9. However, the current version of the BLM uses a rainbow trout log K value (7.3) but achieves the correct sensitivity of the model for daphnids by reducing the saturation of toxic sites needed to cause toxicity. An alternative way may be to use the log K value derived from the present results.

Comparison of silver nitrate and tetracycline as pleural sclerosing agents in rabbits.

The ideal agent to produce pleurodesis has not been identified. Tetracycline, the drug used most commonly in the 1980s, is no longer available. Talc either aerosolized or in a slurry is the agent used just most commonly at the present time, but there are concerns about its safety. Another possibility is silver nitrate, which was widely used in the past, but was abandoned on account of side effects. We hypothesized that lower concentrations of silver nitrate than had been used in the past would be effective in creating a pleurodesis in rabbits. The following medications in a total volume of 2 mL were instilled intrapleurally in three groups of ten anesthetized rabbits: 0.25% or 0.50% silver nitrate and 35 mg/kg tetracycline. Twenty-eight days after the injection, the animals were sacrificed and the pleural spaces were assessed grossly for evidence of pleurodesis and microscopically for evidence of fibrosis and inflammation. The intrapleural injection of 0.50% silver nitrate produced an effective pleurodesis. The mean degree of gross pleurodesis in the rabbits that received 0.50% silver nitrate (3.4 +/- 1.2) did not differ significantly from that of the rabbits that received tetracycline (3.5 +/- 0.7) (scale 0 to 4). The mean degree of microscopic pleural fibrosis in the rabbits that received 0.50% silver nitrate (3.4 +/- 0.7) did not differ significantly from that of the rabbits that received tetracycline (3.9 +/- 0.3). However, 0.25% silver nitrate was ineffective in creating pleural fibrosis, either grossly or microscopically. No rabbits died after the intrapleural injection of the drugs. There were no observed side effects after the injection of silver nitrate. The present study demonstrates that 0.50% silver nitrate instilled into the pleural space is an effective agent for producing pleurodesis in the rabbit; its effect is comparable to tetracycline 35 mg/kg. This agent should be compared with tetracycline derivatives and talc in studies in humans.