Nanosilver Concentration Research Articles

Comparison of Molecular and Histological Changes in Zebrafish Gills Exposed to Metallic Nanoparticles

Research has demonstrated that metallic nanoparticles produce toxicity in aquatic organisms that is due largely to effects of particulates as opposed to release of dissolved ions. The present research examined the interplay of nanoparticle composition and dissolution on response of the zebrafish gill following exposure to toxic (nanocopper or nanosilver) or nontoxic (nano-TiO2) nanometals. Female zebrafish were exposed to 48-h no observable effects concentration of nanocopper and nanosilver or to soluble Cu and Ag that matched the concentration of dissolved metals released during nanoparticle exposure. Both nanocopper and nanosilver exposures increased metal content associated with gill tissue, though silver concentrations were much higher following nanosilver exposures suggesting that intact silver nanoparticles are associated with the gill. Morphological and transcriptional responses of the gills differed among various nanomaterials and between nanoparticulate and soluble species. Nanocopper increased mean gill filament width by three to fourfold between 24 and 48 h, whereas nanosilver did not alter gill filament width at either time point. Global gene expression analysis demonstrates that the exposure to each nanometal or soluble metal produces a distinct gene expression profile at both 24 and 48 h, suggesting that each exposure is producing biological response by a different mechanism. The differences in responses among the exposures indicates that each particle is having a distinct biological effect that does not appear to be driven solely by release of soluble metal ions into the water column. Based on these results, care should be taken when inferring toxicity of nanomaterials from data on a different material.

Physicochemical Characterization and Antimicrobial Activity of Nanosilver Containing Hydrogels

Silver ion has been used for centuries to prevent and treat a variety of diseases and infections. In recent years, extensive studies have been undertaken on the use of antimicrobial properties of silver, incorporated within medical devices. The aim of this study was to prepare a formulation containing silver ion, which could be applied for wound dressing. The purity of nanosilver was measured by atomic absorption spectrophotometer. The purity was determined to be 96.80 % ±0.01. The serial dilution method was used to determine the Minimum Inhibitory Concentration (MIC) of nanosilver, on microorganisms such as staphylococcus aureus, and Pseudomonas aeruginosa. The MIC of nanosilver solution was 15.12 µg/ml. In order to design a hydrogel formulation, different formulations, using HPMC K15M, were made. Next, the best formulation (at 2% w/w) was selected, based on attractiveness, homogeneity and flexibility. This formulation was used for the preparation of the next formulations, containing various percentages of two types of plasticizer. Again, the best formulation was chosen. In order to increase the thickness and resistance of the film, another polymer (HPMC K100 or agar), was added to the formulation. For evaluation of the prepared films, different tests including determination of thickness and tensile strength, swelling and water vapor transition were performed. Finally, the best formulation containing 2% w/w HPMC K15M, 0.5% w/w HPMC K100 and 0.2% triacetin (as plasticizer)was selected. Then, various concentrations of nanosilver solution were added to the selected formulation. In this manner, the most suitable concentration of nanosilver (4 mg in an area of 100 cm 2 or almost 1.5 g weight), which had the best antimicrobial effect in the hydrogel films was detected. In the final stage, the amount of silver in the final film was determined by atomic absorption spectrophotometer. The obtained result confirmed the amount of silver in the final film.