Silver-gold nanotubes containing hot spots on their surface: facile synthesis and surface-enhanced Raman scattering investigations

We report the synthesis of silver-gold nanotubes containing hot spots along their surface. The Ag-Au nanotubes exhibited exceptional SERS properties compared to silver nanowires, enabling the detection of crystal violet in the 10(-10) M regime, as well as 9-nitroanthracene and benzo[a] pyrene at 3.3 x 10(-7) M.

Ventilatory responses to skin extract in catfish

The ventilation rate (VR) of an ostariophysan fish, the speckled catfish Pseudoplaty - stoma coruscans, exposed to a chemical alarm cue was measured in the present study in multiple contexts. The influence of the extraction techniques, skin donor food intake and quantity of the alarm cue (skin extract) on this autonomic response was considered. Overall, the catfish VR decreased significantly when exposed to the skin extract (chemical alarm cue) compared with exposure to distilled water (control). No effect of the extraction technique was found. Increasing doses of the skin extract induced a VR reduction of similar magnitude. However, extract obtained from daily-fed fish induced a significant decrease in the VR, whereas extract obtained from foodrestricted fish did not induce any change in the VR. Thus, food intake was associated with the production of a more easily recognizable alarm cue in the speckled catfish. Interestingly, this effect was not related to differences in the number of club cells in the donor catfish epidermis. Dashing, or rapid swimming, a normal component of the alarm response in fish, including this catfish species, was not observed here, and hypoventilation was always associated with no swimming reaction. Together, these results suggest that hypoventilation is a reaction to a chemical alarm cue, likely resulting in improved crypsis, causing the fish to become less easily perceived by a potential predator that usually strikes prey in response to movement.

Development of cellulose-based bactericidal nanocomposites containing silver nanoparticles and their use as active food packaging

The use of nanomaterials, including metallic as active fillers in polymeric nanocomposites for food packaging has been extensively investigated. Silver nanoparticles (AgNPs), in particular, have been exploited for technological applications as bactericidal agents. In this paper, AgNPs were incorporated into a hydroxypropyl methylcellulose (HPMC) matrix for applications as food packaging materials. The average sizes of the silver nanoparticles were 41 nm and 100 nm, respectively. Mechanical analyses and water vapor barrier properties of the HPMC/AgNPs nanocomposites were analysed. The best results were observed for films containing smaller (41 nm) AgNPs. The antibacterial properties of HPMC/AgNPs thin films were evaluated based on the diameter of inhibition zone in a disk diffusion test against Escherichia coli (E. coil) and Staphylococcus aureus (S. aureus). The disk diffusion studies revealed a greater bactericidal effectiveness for nanocomposites films containing 41 nm Ag nanoparticles. (C) 2011 Elsevier Ltd. All rights reserved.

Antimicrobial effectiveness of silver nanoparticles co-stabilized by the bioactive copolymer pluronic F68

Abstract Background Silver nanoparticles (AgNps) have attracted much interest in biomedical engineering, since they have excellent antimicrobial properties. Therefore, AgNps have often been considered for incorporation into medical products for skin pathologies to reduce the risk of contamination. This study aims at evaluating the antimicrobial effectiveness of AgNps stabilized by pluronic™ F68 associated with other polymers such as polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP). Methods AgNps antimicrobial activity was evaluated using the minimum inhibitory concentration (MIC) method. The action spectrum was evaluated for different polymers associated with pluronic™ F68 against the gram negative bacteria P. aeuroginosa and E. coli and the gram positive bacteria S. Aureus. Results AgNps stabilized with PVP or PVA and co-stabilized with pluronic™ F68 are effective against E. coli and P. aeruginosa microorganisms, with MIC values as low as 0.78% of the concentration of the original AgNps dispersion. The antimicrobial action against S. aureus is poor, with MIC values not lower than 25%. Conclusions AgNps stabilized by different polymeric systems have shown improved antimicrobial activity against gram-negative microorganisms in comparison to unstabilized AgNps. Co-stabilization with the bioactive copolymer pluronic™ F68 has further enhanced the antimicrobial effectiveness against both microorganisms. A poor effectiveness has been found against the gram-positive S. aureus microorganism. Future assays are being delineated targeting possible therapeutic applications.

Processamento auditivo, leitura e escrita na síndrome de Silver-Russell: relato de caso

O objetivo deste trabalho foi descrever os aspectos fonoaudiológicos de processamento auditivo, leitura e escrita de um paciente do gênero masculino com diagnóstico de síndrome de Silver-Russell. Aos dois meses de idade o paciente apresentava déficit pôndero-estatural; frontal amplo; orelhas pequenas, proeminentes e com baixa implantação; palato ogival; discreta micrognatia; esclera azulada; manchas café-com-leite; sobreposição do primeiro e segundo artelhos à direita; refluxo gastroesofágico; voz e choro agudos; atraso leve no desenvolvimento neuropsicomotor; e dificuldade de ganhar peso, recebendo o diagnóstico da síndrome. Na avaliação psicológica, realizada aos 8 anos de idade, o paciente apresentou nível intelectual normal, com dificuldades cognitivas envolvendo atenção sustentada, concentração, memória verbal imediata e processos emocionais e comportamentais. Para avaliação da leitura e escrita e de seus processos subjacentes, realizada aos 9 anos de idade foram utilizados os testes de Compreensão Leitora de Textos Expositivos, Perfil das Habilidades Fonológicas, Teste de Discriminação Auditiva, escrita espontânea, Teste de Desempenho Escolar (TDE), teste de Nomeação Automática Rápida e prova de memória de trabalho fonológica. Apresentou dificuldades em todos os testes, estando as pontuações abaixo do esperado para sua idade. Na avaliação do processamento auditivo foram realizados testes monóticos, dióticos e dicóticos. Foram encontradas alterações nas habilidades de atenção auditiva sustentada e seletiva, memória sequencial para sons verbais e não-verbais, e resolução temporal. Conclui-se que o paciente apresenta alterações na aprendizagem da leitura e escrita que podem ser secundários a síndrome de Silver-Russell, porém tais dificuldades também podem ser decorrentes das alterações em habilidades do processamento auditivo.

Life history of three catfish species (Siluriformes: Ariidae) from southeastern Brazil

This study evaluated the spatio-temporal distribution, reproduction and diet of the catfishes Genidens genidens, G. barbus and Aspistor luniscutis in Caraguatatuba Bay. Their sizes were recorded and the sex and reproductive stage identified. The abundance was compared between areas (South and North) and among months (August 2003 - October 2004). The species had different spatial distributions, allowing them to coexist. The temporal distribution reflected their tendencies to migrate in the reproductive period, as evidenced by the dominance of small immature individuals in the bay. G. genidens tended to reproduce in winter, and A. luniscutis in spring. The diet of G. genidens consisted of crustaceans, mollusks (shells), fish scales, ostracods, and bivalve siphons. G. barbus consumed a high proportion of mysids, followed by fish (bones and scales). For A. luniscutis, the diet was based on fish scales and crustaceans. High quantities of particulate organic matter were observed in the diet of all three species, as previously known for estuarine catfishes. The consumption of fish scales may reflect a lepidophagic habit. A small overlap was observed among the diets, reflecting differences in their environments as well as in the proportions of each item ingested.

A new armored catfish species of the genus Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae) from the upper rio Xingu basin, Brazil

A new armored catfish species of the genus Hypostomus is described from the upper rio Xingu basin, Mato Grosso State, Brazil. The new species is diagnosed from congeners by having high number of teeth (58 to 101, mean 77 on premaxilla, and 58 to 105, mean 80 on dentary), dark spots over body and fins, and abdomen mostly naked. The new species is known from the rapids of the rio Culuene, where it is sympatric with Hypostomus faveolus.

Nuclear abnormalities in erythrocytes and morphometric indexes in the catfish Cathorops spixii (Ariidae) from different sites on the southeastern Brazilian coast

Nuclear abnormalities in erythrocytes (NAE) were taken as biomarkers in the catfish Cathorops spixii (Ariidae) sampled in an estuary little affected by human activity (Cananéia) and in three regions (Santos Channel: SC, Santos Bay: SB and São Vicente Channel: SVC) of the Santos-São Vicente estuary impacted by various anthropogenic activities. Increases in NAE were observed in fish from SC and SVC sampled in the summer period as compared with specimens from the Cananéia estuary. These results suggest the presence of genotoxic compounds in these regions. However, the absence of significant differences in micronuclei frequency reflects slight mutagenic effects in these individuals. It is possible that the lower NAE frequency in specimens from SB might be associated with the greater remobilization and dilution of chemicals in this region. The low frequency of NAE in C. spixii from the Cananéia estuary is in accordance with the slight anthropogenic influence in this system, and may be suggestive of the absence of genotoxic and mutagenic effects in these organisms.

N-Heterocyclic carbene complexes of silver, rhodium and iron: structures, dynamics and catalysis

The research performed in the framework of this Master Thesis has been directly inspired by the recent work of an organometallic research group led by Professor Maria Cristina Cassani on a topic related to the structures, dynamics and catalytic activity of N-heterocyclic carbene-amide rhodium(I) complexes1. A series of [BocNHCH2CH2ImR]X (R = Me, X = I, 1a’; R = Bz, X = Br, 1b’; R = trityl, X = Cl, 1c’) amide-functionalized imidazolium salts bearing increasingly bulky N-alkyl substituents were synthetized and characterized. Subsequently, these organic precursors were employed in the synthesis of silver(I) complexes as intermediate compounds on a way to rhodium(I) complexes [Rh(NBD)X(NHC)] (NHC = 1-(2-NHBoc-ethyl)-3-R-imidazolin-2-ylidene; X = Cl, R = Me (3a’), R = Bz (3b’), R = trityl (3c’); X = I, R = Me (4a’)). VT NMR studies of these complexes revealed a restricted rotation barriers about the metal-carbene bond. However, while the rotation barriers calculated for the complexes in which R = Me, Bz (3a’,b’ and 4a) matched the experimental values, this was not true in the trityl case 3c’, where the experimental value was very similar to that obtained for compound 3b’ and much smaller with respect to the calculated one. In addition, the energy barrier derived for 3c’ from line shape simulation showed a strong dependence on the temperature, while the barriers measured for 3a’,b’ did not show this effect. In view of these results and in order to establish the reasons for the previously found inconsistency between calculated and experimental thermodynamic data, the first objective of this master thesis was the preparation of a series of rhodium(I) complexes [Rh(NBD)X(NHC)] (NHC = 1-benzyl-3-R-imidazolin-2-ylidene; X = Cl, R = Me, Bz, trityl, tBu), containing the benzyl substituent as a chiral probe, followed by full characterization. The second objective of this work was to investigate the catalytic activity of the new rhodium compounds in the hydrosilylation of terminal alkynes for comparison purposes with the reported complexes. Another purpose of this work was to employ the prepared N-heterocyclic ligands in the synthesis of iron(II)-NHC complexes.

Evaluation of Silver European EEL (anguilla anguilla) for the implementation of an Effective EEL Management plan in Mediterranean Coastal Lagoons

This thesis presents SEELF (Sustainable EEL fishery) Index, a methodology for evaluation of European eel (Anguilla anguilla) for the implementation of an effective Eel Management Plan, as defined by EU Regulation No.1100/2007. SEELF uses internal and external indices, age and blood parameters, and selects suitable specimen for restocking; it is also a reliable tool for eel stock management. In fact, SEELF Index, was developed in two versions: SEELF A, to be used in field operations (catch&release, eel status monitoring) and SEELF B to be used for quality control (food production) and research (eel status monitoring). Health status was evaluated also by biomarker analysis (ChE), and data were compared with age of eel. Age determination was performed with otolith reading and fish scale reading and a calibration between the two methods was possible. The study area was the Comacchio lagoon, a brackish coastal lagoon in Italy, well known as an example of suitable environment for eel fishery, where the capability to use the local natural resources has long been a key factor for a successful fishery management. Comacchio lagoon is proposed as an area where an effective EMP can be performed, in agreement with the main features (management of basins, reduction of mortality due to predators,etc.) highlighted for designation of European Restocking Area (ERA). The ERA is a new concept, proposed as a pillar of a new strategy on eel management and conservation. Furthermore, the features of ERAs can be useful in the framework of European Scale Eel Management Plan (ESEMP), proposed as a European scale implementation of EMP, providing a more effectiveness of conservation measures for eel management.

Synthesis and surface modification of silver and gold nanoparticles. Nanomedicine applications against Glioblastoma Multiforme.

In the last decades noble metal nanoparticles (NPs) arose as one of the most powerful tools for applications in nanomedicine field and cancer treatment. Glioblastoma multiforme (GBM), in particular, is one of the most aggressive malignant brain tumors that nowadays still presents a dramatic scenario concerning median survival. Gold nanorods (GNRs) and silver nanoparticles (AgNPs) could find applications such as diagnostic imaging, hyperthermia and glioblastoma therapy. During these three years, both GNRs and AgNPs were synthesized with the “salt reduction” method and, through a novel double phase transfer process, using specifically designed thiol-based ligands, lipophilic GNRs and AgNPs were obtained and separately entrapped into biocompatible and biodegradable PEG-based polymeric nanoparticles (PNPs) suitable for drug delivery within the body. Moreover, a synergistic effect of AgNPs with the Alisertib drug, were investigated thanks to the simultaneous entrapment of these two moieties into PNPs. In addition, Chlorotoxin (Cltx), a peptide that specifically recognize brain cancer cells, was conjugated onto the external surface of PNPs. The so-obtained novel nanosystems were evaluated for in vitro and in vivo applications against glioblastoma multiforme. In particular, for GNRs-PNPs, their safety, their suitability as optoacoustic contrast agents, their selective laser-induced cells death and finally, a high tumor retention were all demonstrated. Concerning AgNPs-PNPs, promising tumor toxicity and a strong synergistic effect with Alisertib was observed (IC50 10 nM), as well as good in vivo biodistribution, high tumor uptake and significative tumor reduction in tumor bearing mice. Finally, the two nanostructures were linked together, through an organic framework, exploiting the click chemistry azido-alkyne Huisgen cycloaddition, between two ligands previously attached to the NPs surface; this multifunctional complex nanosystem was successfully entrapped into PNPs with nanoparticles’ properties maintenance, obtaining in this way a powerful and promising tool for cancer fight and defeat.

Efficacy of silver-bearing external ventricular drainage catheters: a retrospective analysis

Catheter-related infection of CSF is a potentially life-threatening complication of external ventricular drainage (EVD). When using EVD catheters, contact between the ventricular system and skin surface occurs and CSF infection is possible. The aim of this analysis was to compare the efficacy of silver-bearing EVD catheters for reducing the incidence of infection with standard nonimpregnated EVD catheters in neurosurgical patients with acute hydrocephalus.

In vitro cytotoxicity of silver nanoparticles on osteoblasts and osteoclasts at antibacterial concentrations

Abstract Nanoparticulate silver coatings for orthopaedic implants promise to decrease postoperative infection rates. However, silver-induced cytotoxicity on bone cells has not been investigated in detail. This study investigated the cytotoxic effects of silver nano- and microparticles and Ag(+) on osteoblasts (OBs) and osteoclasts (OCs) and correlated their effects with the antibacterial efficacy on Staphylococcus epidermidis. Silver nanoparticles (50 nm) exhibited strong cytotoxic effects on OBs and OCs. Weak cytotoxic effects were observed for silver microparticles (3 μm). The cytotoxicity was primarily mediated by a size-dependent release of Ag(+). Antibacterial effects occurred at Ag(+) concentrations that were 2-4 times higher than those inducing cytotoxic effects. Such adverse effects on OB and OC survival may have deleterious effects on the biocompatibility of orthopaedic implants. Our study represents an important step toward the detailed investigation of orthopaedic implant with nanoparticulate silver coatings prior to their widespread clinical usage.

Acid, Silver, and Solvent-Free Gold-Catalyzed Hydrophenoxylation of Internal Alkynes

A range of arylgold compounds have been synthesized and investigated as single-component catalysts for the hydrophenoxylation of unactivated internal alkynes. Both carbene and phosphine-ligated compounds were screened as part of this work, and the most efficient catalysts contained either JohnPhos or IPr/SIPr. Phenols bearing either electron-withdrawing or electron-donating groups were efficiently added using these catalysts. No silver salts, acids, or solvents were needed for the catalysis, and either microwave or conventional heating afforded moderate to excellent yields of the vinyl ethers.