PEG-copolymer-coated iron oxide nanoparticles that avoid the reticuloendothelial system and act as kidney MRI contrast agents.

In vitro experiments have shown the great potential of magnetic nanocarriers for multimodal imaging diagnosis and non-invasive therapies. However, their extensive clinical application is still jeopardized by a fast retention in the reticuloendothelial system (RES). The other issue that restrains their potential performance is slow degradation and excretion, which increases their risks of toxicity. We report a promising case in which multicore iron oxide nanoparticles coated with a poly(4-vinylpyridine) polyethylene glycol copolymer show low RES retention and high urinary excretion, as confirmed by single photon emission computerized tomography (SPECT), gamma counting, magnetic resonance imaging (MRI) and electron microscopy (EM) biodistribution studies. These iron oxide-copolymer nanoparticles have a high PEG density in their coating which may be responsible for this effect. Moreover, they show a clear negative contrast in the MR imaging of the kidneys. These nanoparticles with an average hydrodynamic diameter of approximately 20 nm were nevertheless able to cross the glomerulus wall which has an effective pore size of approximately 6 nm. A transmission electron microscopy inspection of kidney tissue revealed the presence of iron containing nanoparticle clusters in proximal tubule cells. This therefore makes them exceptionally useful as magnetic nanocarriers and as new MRI contrast agents for the kidneys.

Contributions to the application of the transferability principle and the multipolar modeling of H atoms: electron-density study of L-histidinium dihydrogen orthophosphate orthophosphoric acid. I.

The electron density of L-histidinium dihydrogen orthophosphate orthophosphoric acid has been determined from X-ray and neutron diffraction data at low temperature (120 K). Topological analysis of the electron density has been used to analyse the effect of the multipolar refinement strategy on the electron-density model in the hydrogen-bonding regions. The electron density at low temperature has also been used to acquire high-quality experimental thermal parameters at room temperature using the transferability principle. Molecular vibrations, TLS and normal mode analysis are discussed and studied at both temperatures.

The endocytic penetration mechanism of iron oxide magnetic nanoparticles with positively charged cover: a morphological approach.

In this study we present a morphological approach in observing the interaction of cationic magnetic nanoparticles with A-549 cells (human lung adenocarcinoma). Under our experimental conditions, nanoparticles easily penetrated cells and were observed in vivo, using bright light microscopy. In fixed cells, nanoparticles remained inside cells, showing quantity and distribution patterns similar to those in unfixed cells. The presence of nanoparticles did not affect cell viability or the morphologic parameters assessed. We determined the potential internalization mechanism of nanoparticles into cells using endocytosis inhibitors. The results suggest that nanoparticles used in this study penetrate A-549 cells mainly through a macropinocytosis process.