Cyclodextrin-Based Organic Radical Contrast Agents for in†vivo Imaging of Gliomas.

Cyclodextrins (CDs), a class of cyclic oligosaccharides formed by α-(1,4) linked glucopyranose units, were functionalized with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) radicals to prepare water soluble supramolecular organic radical contrast agents (ORCAs) for the in vivo detection of glioma tumor in animal models. A first set of molecules (CDn1, n=6,7,8 is the number of both TEMPO and glucopyranose units) was studied by superconducting quantum interference devices (SQUID) magnetometry in order to define the role of the CD macrocycle on the effective magnetic moment (µeff ). The µeff value increased from 3.982 µB (CD61) to 4.522 µB (CD81) but was limited by intramolecular antiferromagnetic (AF) interactions. A set of water-soluble ORCAs (CDn8, n=6,7,8) was prepared by a sequence of thiol-ene and Cu(I)-catalyzed alkyne-azide "click" reactions. Their 1 H water relaxivities r1 of these ORCAs were between 0.739 mM-1 s-1 (CD68) to 1.047 mM-1 s-1 (CD88) in D2 O/H2 O 9 : 1 (v : v) at 300 K. One of them (CD78) was tested on glioma-bearing rats with reduced side effects and good relaxivity in vivo.

Magnetic calcium phosphates nanocomposites for the intracellular hyperthermia of cancers of bone and brain.

Aim: Magnetic hyperthermia is limited by the low selective susceptibility of neoplastic cells interspersed within healthy tissues, which we aim to improve on. Materials & methods: Two superparamagnetic calcium phosphates nanocomposites, that is, iron-doped hydroxyapatite and iron oxide (Mag) nanoparticles coated with amorphous calcium phosphate (Mag@CaP), were synthesized and tested for selective activity against brain and bone cancers. Results: Nanoparticle uptake and intracellular localization were prerequisites for reduction of cancer viability in alternate magnetic fields of extremely low power. Sheer adsorption onto the outer membrane was not sufficient to produce this effect, which was extremely significant for Mag@CaP and iron-doped hydroxyapatite, but negligible for Mag, demonstrating benefits of combining magnetic iron with calcium phosphates. Conclusion: Such selective effects are important in the global effort to rejuvenate clinical prospects of magnetic hyperthermia.

Theoretical and experimental investigation of magnetotransport in iron chalcogenides.

We explore the electronic, transport and thermoelectric properties of Fe1+y Se x Te1-x compounds to clarify the mechanisms of superconductivity in Fe-based compounds. We carry out first-principles density functional theory (DFT) calculations of structural, electronic, magnetic and transport properties and measure resistivity, Hall resistance and Seebeck effect curves. All the transport properties exhibit signatures of the structural/magnetic transitions, such as discontinuities and sign changes of the Seebeck coefficient and of the Hall resistance. These features are reproduced by calculations provided that antiferromagnetic correlations are taken into account and experimental values of lattice constants are considered in DFT calculations. On the other hand, the temperature dependences of the transport properties can not be fully reproduced, and to improve the agreement between experiment and DFT calculations it is necessary to go beyond the constant relaxation time approximation and take into account correlation effects.