Enhanced antitumor efficacy of biocompatible magnetosomes for the magnetic hyperthermia treatment of glioblastoma

In this study, biologically synthesized iron oxide nanoparticles, called magnetosomes, are made fully biocompatible by removing potentially toxic organic bacterial residues such as endotoxins at magnetosome mineral core surfaces and by coating such surface with poly-L-lysine, leading to magnetosomes-poly-L-lysine (M-PLL). M-PLL antitumor efficacy is compared with that of chemically synthesized iron oxide nanoparticles (IONPs) currently used for magnetic hyperthermia. M-PLL and IONPs are tested for the treatment of glioblastoma, a dreadful cancer, in which intratumor nanoparticle administration is clinically relevant, using a mouse allograft model of murine glioma (GL-261 cell line). A magnetic hyperthermia treatment protocol is proposed, in which 25 µg in iron of nanoparticles per mm3 of tumor are administered and exposed to 11 to 15 magnetic sessions during which an alternating magnetic field of 198 kHz and 11 to 31 mT is applied for 30 minutes to attempt reaching temperatures of 43-46 °C. M-PLL are characterized by a larger specific absorption rate (SAR of 40 W/gFe compared to 26 W/gFe for IONPs as measured during the first magnetic session), a lower strength of the applied magnetic field required for reaching a target temperature of 43-46 °C (11 to 27 mT compared with 22 to 31 mT for IONPs), a lower number of mice re-administered (4 compared to 6 for IONPs), a longer residence time within tumours (5 days compared to 1 day for IONPs), and a less scattered distribution in the tumour. M-PLL lead to higher antitumor efficacy with full tumor disappearances achieved in 50% of mice compared to 20% for IONPs. This is ascribed to better ability of M-PLL, at equal iron concentrations, to maintain tumor temperatures at 43-46°C over a longer period of times

Magnetic and structural properties of biogenic magnetic nanoparticles along their production process for use in magnetic hyperthermia

International audienceIron-oxide nanoparticles synthesized by magnetotactic bacteria can be used in cancer treatment by means of magnetic hyperthermia. In order to study the structural properties of samples through the successive steps of their production from cultivated magnetotactic bacteria to coated magnetosomes, and their effect on magnetic properties, we performed a combination of (cryo-)Transmission Electron Microscopy observations and magnetic hysteresis as well as First-Order Reversal Curve diagrams at low temperature. The anisotropy of magnetic interactions was investigated by recording field-cooled FORC diagrams with a measuring field either parallel or perpendicular to the field-cooling direction. The results from the various techniques are in very good agreement. We found that magnetosomes in magnetotactic bacteria are arranged in chains and have magnetic properties typical of stable single-domain aligned particles. Extracted magnetosomes form clusters of interacting maghemite particles with some remaining chains, while purified magnetosomes are solely arranged in clusters. Finally, magnetosomes coated with 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) are still organized in clusters but with less magnetostatic interactions than in purified magnetosomes, while magnetosomes coated with citric acid tend to recover a chained structure forming loops. The main features observed on the FORC diagrams are consistent with the various arrangement observed. Lastly, hyperthermia properties were measured for the two coated samples and we found that magnetosomes coated with citric acid display a higher Specific Absorption Rate and therefore hold a better potential for biomedical applications

The CFHTLS strong lensing legacy survey. I. Survey overview and T0002 release sample

International audienceAims:We present data from the CFHTLS Strong Lensing Legacy Survey (SL2S). Due to the unsurpassed combined depth, area and image quality of the Canada-France-Hawaii Legacy Survey it is becoming possible to uncover a large, statistically well-defined sample of strong gravitational lenses which spans the dark halo mass spectrum predicted by the concordance model from galaxy to cluster haloes. Methods: We describe the development of several automated procedures to find strong lenses of various mass regimes in CFHTLS images. Results: The preliminary sample of about 40 strong lensing candidates discovered in the CFHTLS T0002 release, covering an effective field of view of 28 deg2 is presented. These strong lensing systems were discovered using an automated search and consist mainly of gravitational arc systems with splitting angles between 2 and 15 arcsec. This sample shows for the first time that it is possible to uncover a large population of strong lenses from galaxy groups with typical halo masses of about 1013~h-1~M_&sun;. We discuss the future evolution of the SL2S project and its main scientific aims for the next 3 years, in particular our observational strategy to extract the hundreds of gravitational rings also present in these fields

Visualizing Giant Ferroelectric Gating Effects in Large-Scale WSe₂/BiFeO₃ Heterostructures

International audienceMultilayers based on quantum materials (complex oxides, topological insulators, transition-metal dichalcogenides, etc.) have enabled the design of devices that could revolutionize microelectronics and optoelectronics. However, heterostructures incorporating quantum materials from different families remain scarce, while they would immensely broaden the range of possible applications. Here we demonstrate the large-scale integration of compounds from two highly multifunctional families: perovskite oxides and transition-metal dichalcogenides (TMDs). We couple BiFeO 3 , a room-temperature multiferroic oxide, and WSe 2 , a semiconducting two-dimensional material with potential for photovoltaics and photonics. WSe 2 is grown by molecular beam epitaxy and transferred on a centimeter-scale onto BiFeO 3 films. Using angle-resolved photoemission spectroscopy, we visualize the electronic structure of 1 to 3 monolayers of WSe 2 and evidence a giant energy shift as large as 0.75 eV induced by the ferroelectric polarization direction in the underlying BiFeO 3. Such a strong shift opens new perspectives in the efficient manipulation of TMD properties by proximity effects

Spin–Charge Interconversion in KTaO 3 2D Electron Gases

International audienceOxide interfaces exhibit a broad range of physical effects stemming from broken inversion symmetry. In particular, they can display non-reciprocal phenomena when time reversal symmetry is also broken, e.g., by the application of a magnetic field. Examples include the direct and inverse Edelstein effects (DEE, IEE) that allow the interconversion between spin currents and charge currents. The DEE and IEE have been investigated in interfaces based on the perovskite SrTiO$_3$ (STO), albeit in separate studies focusing on one or the other. The demonstration of these effects remains mostly elusive in other oxide interface systems despite their blossoming in the last decade. Here, we report the observation of both the DEE and IEE in a new interfacial two-dimensional electron gas (2DEG) based on the perovskite oxide KTaO$_3$. We generate 2DEGs by the simple deposition of Al metal onto KTaO$_3$ single crystals, characterize them by angle-resolved photoemission spectroscopy and magnetotransport, and demonstrate the DEE through unidirectional magnetoresistance and the IEE by spin-pumping experiments. We compare the spin-charge interconversion efficiency with that of STO-based interfaces, relate it to the 2DEG electronic structure, and give perspectives for the implementation of KTaO$_3$ 2DEGs into spin-orbitronic devices