No abstract

No abstract

The present study reveals the potential of magnetic nanoparticles based on the La 0.75 Sr 0.25 MnO 3 perovskite manganite for magnetic resonance imaging (MRI). Moreover, it describes the development of the dual imaging probe where the magnetic cores are combined with a fluorescent moiety while the improved colloidal stability is achieved by a two-ply silica shell. At first, the magnetic cores of La 0.75 Sr 0.25 MnO 3 are coated with a hybrid silica layer, comprising a covalently attached fluorescein moiety that is subsequently covered by a pure silica layer providing the enhanced stability. The detailed characterization of the intermediate and the final product reveals the importance of the complex twoply shell. Viability tests show that the complete particles are suitable for biological studies. Internalization of the particles and their presence in intracellular vesicles are observed by fluorescence microscopy in different cell types. Further experiments prove no fatal interference with the vitality and insulin releasing ability of labeled pancreatic islets. Relaxometric measurements confirm high spin-spin relaxivities at magnetic fields of B 0 ¼ 0.5-3 T, while visualisation of in vitro labeled pancreatic islets by MRI is successfully tested.

A new preparation method for the synthesis of TiO 2 microrods in aqueous media starting with solid hydrated titanyl sulfate crystals with defined morphology is presented. The method is based on the extraction of sulfate ions from the crystals and their replacement with hydroxyl groups in aqueous ammonia solution leaving the Ti−O framework intact. The particle size and morphology of the starting hydrated titanyl sulfate is closely preserved in the pseudomorphs of amorphous metatitanic acid including such details like the layered structure of the original hydrated titanyl sulfate crystals. When annealed up to 1200 °C, the rod-like morphology of particles is retained, while the phase composition changes to anatase/rutile. The rod-like particles of metatitanic acid possess excellent sorption properties toward radionuclides. The mechanism of pseudomorph formation is discussed based on the structures of the precursors, including the hitherto unknown structure of titanyl sulfate dihydrate determined by electron diffraction tomography.

No abstract