Superparamagnetic iron oxide nanoparticles induce persistent large foci of DNA damage in human melanoma cells post-irradiation.

The synergy of superparamagnetic iron oxide nanoparticles (SPIONs) and ionizing radiation (IR), attributed to reactive oxygen species (ROS) and DNA double-strand breaks (DSBs) increase, was widely investigated in different cancers, but scarcely in melanoma. Herein, SPIONs were evaluated as radiosensitizers in A-375 human melanoma cells. Moreover, the effect of the combined treatment of SPIONs and gamma irradiation (SPIONs-IR) was assessed at the DNA level, where DSBs induction and their repair capacity were studied. SPIONs were synthesized, stabilized by poly(ethylene glycol) methyl ether and physicochemically characterized by high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction and magnetometry and dynamic light scattering. The obtained nanoparticles showing superparamagnetic behavior and low dispersion in shape and sizes were tested in A-375 cells. The intracellular internalization of SPIONs was verified by HR-TEM and quantified by inductively coupled plasma atomic emission spectroscopy. Cells treated with SPIONs exhibited high ROS levels without associated cytotoxicity. Next, a significant radiosensitization in SPIONs-IR vs. control (IR) cells was demonstrated at 1 Gy of gamma radiation. Furthermore, a decreased DSBs repair capacity in SPIONs-IR vs. IR-treated cells was evidenced by the size increase of persistent phosphorylated H2AX foci at 24 h post-irradiation. In conclusion, these nanoparticles show the potential to radiosensitize melanoma cells by the induction of unrepairable DNA damage.

Pressure Induced Stability Enhancement of Cubic Nanostructured CeO2 †.

Ceria (CeO2)-based materials are widely used in applications such as catalysis, fuel cells and oxygen sensors. Its cubic fluorite structure with a cell parameter similar to that of silicon makes it a candidate for implementation in electronic devices. This structure is stable in a wide temperature and pressure range, with a reported structural phase transition to an orthorhombic phase. In this work, we study the structure of CeO2 under hydrostatic pressures up to 110 GPa simultaneously for the nanometer- and micrometer-sized powders as well as for a single crystal, using He as the pressure-transmitting medium. The first-order transition is clearly present for the micrometer-sized and single-crystal samples, while, for the nanometer grain size powder, it is suppressed up to at least 110 GPa. We show that the stacking fault density increases by two orders of magnitude in the studied pressure range and could act as an internal constraint, avoiding the nucleation of the high-pressure phase.

Iron-based nanoparticles prepared from yerba mate extract. Synthesis, characterization and use on chromium removal.

Iron-based nanoparticles were synthesized by a rapid method at room temperature using yerba mate (YM) extracts with FeCl3 in different proportions. Materials prepared from green tea (GT) extracts were also synthesized for comparison. These materials were thoroughly characterized by chemical analyses, XRD, magnetization, SEM-EDS, TEM-SAED, FTIR, UV-Vis, Raman, Mössbauer and XANES spectroscopies, and BET area analysis. It was concluded that the products are nonmagnetic iron complexes of the components of the extracts. The applicability of the materials for Cr(VI) (300 µM) removal from aqueous solutions at pH 3 using two Cr(VI):Fe molar ratios (MR), 1:3 and 1:0.5, has been tested. At Cr(VI):Fe MR = 1:3, the best YM materials gave complete Cr(VI) removal after two minutes of contact, similar to that obtained with commercial nanoscale zerovalent iron (N25), with dissolved Fe(II), and with a likewise prepared GT material. At a lower Cr(VI):Fe MR (1:0.5), although Cr(VI) removal was not complete after 20 min of reaction, the YM nanoparticles were more efficient than N25, GT nanoparticles and Fe(II) in solution. The results suggest that an optimal Cr(VI):Fe MR ratio could be reached when using the new YM nanoparticles, able to achieve a complete Cr(VI) reduction, and leaving very low Cr and Fe concentrations in the treated solutions. The rapid preparation of the nanoparticles would allow their use in removal of pollutants in soils and groundwater by direct injection of the mixture of precursors.