Iron-related toxicity effects of single-walled carbon nanotubes in human placental cells (BeWo) investigated by X-ray fluorescence microscopy

As the prospect of human beings exposed to new nanomaterials increases, there are growing concerns about the foetal exposure and effects of such nanomaterials during pregnancy. Among others, due to their ample usage, it becomes urgent to address the vulnerability of the human placental barrier to carbon nanotubes (CNTs). Recently, by applying a combination of advanced synchrotron-based X-ray microscopy and X-ray fluorescence (XRF) techniques, we demonstrated that raw single-walled CNTs (SWCNTs) may cause an asbestos-like iron-related toxicity in mesothelial (MeT5A) cells. This work shows the results obtained with the same approach and experimental conditions in human choriocarcinoma (BeWo) cells as a placental model. XRF microscopy in mild and soft X-ray regimes was used to map the distribution of P, S, Ca, and Fe in exposed and control cells, whereas absorption and phase-contrast imaging (soft X-ray microscopy) provided simultaneous morphological information. The findings show that exposure to SWCNTs affects cell viability and causes a small increase in intracellular iron content, further confirmed by the stimulation of the ferritin protein. It is interesting to note that the iron changes are negligible when highly purified SWCNTs are used. In all tested conditions, including exposure to iron sulfate, the iron accumulation or ferritin increase was much lower in BeWo cells than in MeT5A ones, suggesting a different iron metabolism and possibly a lower vulnerability of the placental barrier to iron-rich nanomaterials.     

Kinetically Stable Nonequilibrium Gold-Cobalt Alloy Nanoparticles with Magnetic and Plasmonic Properties Obtained by Laser Ablation in Liquid

Nonequilibrium nanoalloys are metastable solids obtained at the nanoscale under nonequilibrium conditions that allow the study of kinetically frozen atoms and the discovery of new physical and chemical properties. However, the stabilization of metastable phases in the nanometric size regime is challenging and the synthetic route should be easy and sustainable, for the nonequilibrium nanoalloys to be practically available. Here we report on the one-step laser ablation synthesis in solution (LASiS) of nonequilibrium Au−Co alloy nanoparticles (NPs) and their characterization on ensembles and at the single nanoparticle level. The NPs are obtained as a polycrystalline solid solution stable in air and water, although surface cobalt atoms undergo oxidation to Co(II). Since gold is a renowned plasmonic material and metallic cobalt is ferromagnetic at room temperature, these properties are both found in the NPs. Besides, surface conjugation with thiolated molecules is possible and it was exploited to obtain colloidally stable solutions in water. Taking advantage of these features, an array of magnetic-plasmonic dots was obtained and used for surface-enhanced Raman scattering experiments. Overall, this study confirms that LASiS is an effective method for the formation of kinetically stable nonequilibrium nanoalloys and shows that Au−Co alloy NPs are appealing magnetically responsive plasmonic building blocks for several nanotechnological applications.     

Structural characterization of electrodeposited copper hexacyanoferrate films by using a spectroscopic multi-technique approach

A deep structural investigation predominantly by X-ray spectroscopic techniques is conducted on films of copper hexacyanoferrate (CuHCF) deposited under different conditions, aimed at establishing structure-properties relationships. We show that the potentiodynamic electrosynthesis of CuHCF on carbon-based surfaces produces a highly disordered material, with a variable amount of Prussian Blue (PB). The subsequent Cu(2+) intercalation induces the partial conversion of PB into CuHCF, which explains the improved electrocatalytic properties after the intercalation process. Both Cu and Fe K-edge data have been recorded. For the sample with the lower amount of PB, we could perform a multiple edge data analysis to determine the local atomic environment around both metal centres using the same set of structural parameters. The presence of high multiplicity Cu-N-C-Fe linear chains has allowed us to determine accurately the local environment of Fe while fitting the Cu K-edge data only. Using this approach we have retrieved structural information around Fe for those samples in which the concomitant presence of PB would have made impossible the analysis of the Fe K-edge. The Fe-C, C-N and Cu-N bond distances have been found in agreement with those of the bulk structures, but higher values of [Fe(CN)(6)] vacancies for the building blocks have been evidenced, reaching a value of ~45% in one sample. XANES, Raman and SEM data agree with the model proposed for each studied electrode.     

XRF mapping and TEM analysis of coated and uncoated silica nanoparticles in A549 cells and human monocytes

The evaluation of nanomaterials intracellular distribution still remains a challenge in nanomedicine applications and toxicological studies. Synchrotron radiation X-ray microscopy combined with X-ray fluorescence (XRF) microspectroscopy provides unique information that has pushed the frontiers of biological research, particularly when investigating intracellular mechanisms. In this work, the presence of silica nanoparticles in in vitro cultured human lung epithelial cell line and freshly extract human monocytes has been investigated. For the uptake and intracellular distribution of NPs, cells were cultured on polymeric substrates (Mylar). The SiO₂–NPs have been synthesized at JRC and characterized by dynamic light scattering, centrifugal liquid sedimentation, and transmission electron microscopy (TEM), whereas their interaction with cells was investigated with TEM and XRF. For the latter, we used TwinMic in scanning transmission mode coupled with low-energy XRF spectroscopy, paying particular attention to the distribution of different elements, namely, Fe, O, C, Si, and Mg. Si XRF signals recorded on cells exposed to uncoated silica and epoxy-coated silica nanoparticles are comparable, indicating low difference in cellular uptake and suggesting a similar interaction between nanoparticles and cells. However, the TEM analysis indicates a better affinity of the coated nanoparticles for the cell membrane. Moreover, the TEM analysis shows also the presence of nanoparticles in endosomes.     

2-Naphthol-phosphatidylethanolamine: A fluorescent phospholipid analogue for excited-state proton transfer studies in membranes

The fluorescence properties of the phospholipid derivative,N-[1-(2-naphthol)]-phosphatidylethanolamine (NAPH-PE), have been studied by steady-state and time-resolved fluorescence techniques. The new probe is a naphthol adduct of phosphatidylethanolamine. The emission spectrum of the fluorescent phospholipid depends on the pH and on the proton acceptor concentration as expected for a typical two-state excited-state proton transfer reaction. In ethanol solutions at an apparent pH of 6.7 and in the presence of acetate anion (0.14M), a biexponential decay is obtained from global analysis of the data. The lifetimes, ₁=3.9 ns and ₂=6.2 ns. are constant across the spectral region 350–460 nm. The decay-associated spectra and the species-associated spectra reproduce well the profiles reported for a two-state excited-state proton transfer reaction. The fluorescent phospholipid has been incorporated into dimyristoyllecithin and dipalmitoyllecithin vesicles. Although lower proton transfer is found, the reaction appears to be dependent on the gel-to-liquid-crystalline phase transition of the lipid membrane. In addition, the steady-state anisotropy of NAPH-PE measured as a function of temperature trace the phase transition of the two vesicle systems. Thus, it is shown that the physical state of the bilayer affects a reaction which takes place at the membrane surface. In the presence of acetate ions (0.3M), global analysis, performed in terms of fluorescence decay parameters, recovers preexponential coefficients that are consistent with an excited-state proton transfer reaction. The short lifetime drops from 3.9 to 0.44 ns without significant changes of the longer-lifetime component.     

Interacting physical states of the bosonic string. II

The Diff anomaly for the standard sigma model lagrangian is considered, and some puzzling aspects of the dilation coupling are clarified. It is shown how the central charge is related to the Diff anomaly and some of its properties are illustrated. The consistency of the BRST invariance requirement with the existence of different vacua for the string is discussed.     

Polycyclic compounds from aminopolyols and alpha-dicarbonyls: structure and application in the synthesis of exoditopic ligands

The structure and stereochemistry of the crystalline 2 : 2 condensation product ("glytham") of glyoxal and tris(hydroxymethyl)aminomethane was conclusively determined by X-ray diffractometric analysis. The singular disposition of the heteroatoms suggests the employment of glytham as starting material for the synthesis of ditopic ligands for metal ions. Some derivatives of glytham were prepared and their binding properties towards alkaline metal ions were preliminarily investigated by ESI-MS and NMR.