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The fish intestine is an important barrier for environmental toxicants, including metals and metal nanoparticles. Tracking chemical transformation at the interface between the intestinal epithelium and the intestinal lumen can inform us about chemicals' bio-reactivity and toxicity but is challenging due to the lack of appropriate models. To allow for such investigations, a model of the fish intestine derived from rainbow trout ( Oncorhynchus mykiss ), the RTgutGC cell line, was used. Cells were exposed to silver nitrate (AgNO 3 ) or citrate coated silver nanoparticles (cit-AgNPs) in Leibovitz's L-15 medium without amino acids and vitamins (L-15/ex), which allowed the determination of the extracellular silver species using a chemical equilibrium model. X-ray absorption spectroscopy (XAS) was used to track intracellular silver speciation. Cellular toxicity, silver accumulation, and metallothionein (MT) mRNA levels were also measured. Cells accumulated the same concentrations of silver when exposed to equimolar amounts ( i.e. 1, 5 and 10 μM) of AgNO 3 or cit-AgNPs. However, AgNO 3 was shown to be more toxic than cit-AgNPs. Intracellular silver speciation changed over time in both exposure series. After 1 hour, intracellular silver speciation was dominated by chloride complexation in both exposures. After 24 and 72 hours of exposure to cit-AgNPs, ∼7% of silver was complexed to cysteine, whereas the remaining silver was AgNPs. In cells exposed to AgNO 3 for 72 hours, 97% of Ag was complexed to cysteine. A significant increase, compared to controls, in metallothionein mRNA levels at 24 and 72 hours of exposure to AgNO 3 and cit-AgNPs can explain the formation of Ag–cysteine complexes. In summary, these data show that silver chloride species are bioavailable and that complexation to cysteine scavenges intracellular dissolved silver ions, thus preventing toxicity. Silver nanoparticles present a similar but attenuated toxic response to AgNO 3 . Thus, at least in acute exposures, existing risk assessment for dissolved silver species could be protective for nanosilver.
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Simulation and synthesis of silver dendritic nanostructures for surface-enhanced Raman scattering
Silver dendritic nanostructures (AgD) is investigated for surface-enhanced Raman scattering (SERS) with simulation and experiments, the simulations showed that there is a significant absorbance over a broad spectrum from the AgD, this indicated that AgD is a good candidate for SERS. The simulations helped to study the parameters of the AgD that affects the SERS and we applied these simulation results for experimental designs, in which our experimental results of synthesis and characterization results of Raman spectrum showed consistence with the simulation results. These simulation results are very helpful in deciding the experimental parameters for efficient and effective synthesizing and reproduction of hierarchical silver dendritic nanostructure. The AgD were produced using displacement redox reaction between AgNO 3 solution and Copper foil. We found that the concentration of AgNO 3 played major role on the rate of reaction, and the rapid growth of the silver nanostructures was observed as the reaction time increases. The structural and morphological evolution of silver dendrites was examined with Scanning Electron Microscope (SEM). The Raman enhancement of AgDs was evaluated using Elman's reagent (DTNB) and Rhodamine 6G (R6G). The silver dendrites have great potential for diverse sensing applications ranging from food safety control, environmental monitoring and assessment, forensic investigation, and to medical diagnosis.
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- Award ID(s):
- 1829245
- PAR ID:
- 10178105
- Date Published:
- Journal Name:
- Materials Express
- Volume:
- 9
- Issue:
- 9
- ISSN:
- 2158-5849
- Page Range / eLocation ID:
- 1082 to 1086
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1166/mex.2019.1603
