Recently, iron oxide nanoparticles (IONPs) have gathered special attention in regenerative medicine. Owing to their magnetic and bioactive properties, IONPs are utilized in the fabrication of novel biomaterials. Yet, there was no report regarding thermoplastic polyurethane (TPU) and poly(lactic acid) (PLA) polymer doped with IONPs on osteogenic differentiation of mesenchymal stem cells. Thus the objectives of presented study was to: (a) fabricate magnetic TPU + PLA sponges doped with iron (III) oxide Fe2O3 nanoparticles; (b) investigate the effects of biomaterial and its exposition to static magnetic field (MF) on osteogenic differentiation, proliferation, and apoptosis in adipose‐derived mesenchymal stem cells (ASCs). TPU + PLA sponges were prepared using solvent casting technique while incorporation of the Fe2O3 nanoparticles was performed with solution cast method. RT‐PCR was applied to evaluate expression of osteogenic‐related genes and integrin's in cells cultured on fabricated materials with or without the stimulation of static MF. MF stimulation enhanced the expression of osteopontin and collagen type I while decreased expression of bone morphogenetic protein 2 in tested magnetic materials—TPU + PLA/1% Fe2O3 and TPU + PLA/5% Fe2O3. Therefore, TPU + PLA sponges doped with IONPs and exposure to MF resulted in improved osteogenic differentiation of ASC.
Bismuth layer-structured compounds in the Bi-Ti-Fe-O system known as Aurivillius phases are single phase multiferroics. It was stated that substitution of some rare earth elements for bismuth ions in such structure can modified its magnetic properties. Powders of Bi7Fe3Ti3O21 and Bi6.3Sm0.7Fe3Ti3O21 were prepared by co-precipitation – calcination method and then were sintered to dense polycrystalline materials. Low field DC susceptibility was measured in the zero field cooled (ZFC) and field cooled (FC) modes at 10÷350 K. For selected temperatures magnetisation curves and hysteresis loops were also measured. The FC and ZFC curves of both samples diverge at temperatures below 250 K indicating a spin glass-like behaviour. The compound with samarium exhibits magnetic hysteresis already at room temperature with the coercive field increasing to 870 Oe at 10 K. The low temperature hysteresis loops of the samarium containing compound are shift with respect to zero field which can be attributed to a magneto-electrical coupling of the samarium sublattice "exchange biased" by the iron one, which orders anti-ferromagnetically at a higher temperature than the samarium sublattice.
The multiferroic Aurivillius phases in the Bi-Fe-Ti-O system are built from alternate (Bi2O2)2+ and (Bin-1XnO3n+1)2 layers, where X = Fe3+, Ti4+ and “n” refers to the number of perovskite-like layers between Bi2O2 layers. Detailed magnetic studies should be done to understand electromagnetic interactions and multiferroic coupling effects. In the present paper, a powder composed of the Aurivillius phase with n = 5, Bi6Fe2Ti3O18, was successfully prepared by the hydrothermal method. The powder was sintered, obtaining dense polycrystalline materials. It was stated that both powder and sintered bodies were paramagnets with a possible antiferromagnetic ordering or a spin-glass state at the liquid helium temperatures.
A series of high-purity Er 0.05 Y 1.95 O 3 nanopowders with different lanthanum content was prepared by modification of the Pechini sol-gel method using citric acid and ethylene glycol as the chelating agent. The microstructure of the powders was studied by means of X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy. In order to evaluate the structural characteristics of the obtained gel, XRD measurements were carried out with calcination gels in selected temperatures. Simultaneous differential thermal analysis with thermal gravimeters indicates a decrease of calcination temperature with an increasing content of lanthanum ions. Morphological properties of the nano-sized powders were examined by scanning electron microscopy. Strong luminescence in near IR region was observed under 980 nm excitation at room temperature. By varying the concentration of La 3? ion, various intensities of upconversion luminescence can be easily achieved.
The Aurivillius phases in the Bi-Fe-Ti-O system showing multiferroic properties arouse an increasing interest due to their wide potential applications in electronics. These compounds were usually prepared by high temperature solid-state reaction method using respective oxide powders mixed in required stoichiometry. An excess of bismuth oxide was often added due to its evaporation during heat treatment. The mixture of the oxide powders were calcined in air between 700 and 900°C for several or even for several dozen hours. In the present paper the Bi6Fe2Ti3O18 Aurivillius phase was prepared by direct solid state reaction between respective oxides and by co-precipitation – calcination method. Mixture of the oxides and co-precipitated gels were calcined at different temperatures and X-ray diffraction analysis was used for identification of phase composition of the products.
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