2 research outputs found
Raman Signal Enhancement Dependence on the Gel Strength of Ag/Hydrogels Used as SERS Substrates
A series
of hydrogel samples composed of Ag nanoparticles dispersed
in carrageenan gels have been prepared and used in SERS studies. These
studies demonstrate the dependence of the enhancement of the SERS
signal on the strength of the Ag/polysaccharide hydrogel. 2,2′-Dithiodipyridine
was used as the analyte probe. Several strategies were employed in
order to vary the gel strength. These include the increase of the
polysaccharide content in the gel, the addition of KCl as cross-linker,
and the variation of the type of carrageenan (κ, ι, λ)
network. An increase in the gel strength originates an increase in
the SERS enhancement observed. The results have been interpreted considering
hot spots increase due to the formation of Ag particles nanojunctions
as the biopolymer matrix tends to rearrange into stronger gels. This
is the first report showing that there is a direct correlation between
the gel strength of a hydrogel composite used as substrate and its
analytical SERS sensitivity
Metabolomics of silver nanoparticles toxicity in HaCaT cells: structure–activity relationships and role of ionic silver and oxidative stress
<p>The widespread use of silver nanoparticles (AgNPs) is accompanied by a growing concern regarding their potential risks to human health, thus calling for an increased understanding of their biological effects. The aim of this work was to systematically study the extent to which changes in cellular metabolism were dependent on the properties of AgNPs, using NMR metabolomics. Human skin keratinocytes (HaCaT cells) were exposed to citrate-coated AgNPs of 10, 30 or 60 nm diameter and to 30 nm AgNPs coated either with citrate (CIT), polyethylene glycol (PEG) or bovine serum albumin (BSA), to assess the influence of NP size and surface chemistry. Overall, CIT-coated 60 nm and PEG-coated 30 nm AgNPs had the least impact on cell viability and metabolism. The role of ionic silver and reactive oxygen species (ROS)-mediated effects was also studied, in comparison to CIT-coated 30 nm particles. At concentrations causing an equivalent decrease in cell viability, Ag<sup>+ </sup>ions produced a change in the metabolic profile that was remarkably similar to that seen for AgNPs, the main difference being the lesser impact on the Krebs cycle and energy metabolism. Finally, this study newly reported that while down-regulated glycolysis and disruption of energy production were common to AgNPs and H<sub>2</sub>O<sub>2</sub>, the impact on some metabolic pathways (GSH synthesis, glutaminolysis and the Krebs cycle) was independent of ROS-mediated mechanisms. In conclusion, this study shows the ability of NMR metabolomics to define subtle biochemical changes induced by AgNPs and demonstrates the potential of this approach for rapid, untargeted screening of pre-clinical toxicity of nanomaterials in general.</p