Nanoparticules de fer de taille contrôlée pour l’hyperthermie : synthèse par voie organométallique, caractérisations magnétiques et mesures de puissance dissipée

Les nanoparticules magnétiques présentent un fort potentiel pour le traitement de tumeurs par hyperthermie ; leur efficacité dépend de la taille, de l’état de surface et de la nature du matériau. Nous avons réalisé une étude fondamentale de la synthèse par voie organométallique de nanoparticules de fer métallique, de leurs propriétés magnétiques intrinsèques et de leur réponse en hyperthermie. Des particules de taille contrôlée (entre 1.5 à et 90 nm ont été obtenues par décomposition du dimère (Fe{N[Si(CH3)3]2}2)2. Leur croissance a été suivie par TEM, Mössbauer et SQuID et a révélé les rôles clés de mésophases lamellaires et de l’acide. Une méthode innovante de synthèse par mûrissement de germes est développée. La surface des nanoparticules n’est pas oxydée (Ms = 220 Am2.kg-1), mais une exaltation de la constante d’anisotropie (Keff) a été mesurée pour de petites particules (x10 pour 1.5 nm et x3 pour 5.5 nm). Holographie électronique et calculs micromagnétiques ont permis d’étudier quantitativement une configuration vortex dans un cube de 30 nm. Un banc de mesure d’hyperthermie ajustable en fréquence a été mis en place et a permis de caractériser des particules superparamagnétiques de fer (de 5.5 et 7.5 nm). Des particules de FeCo de 14.2nm ont également été testées.--------------------------------------------------------------------------------Magnetic nanoparticles are of great interest for hyperthermia treatment of tumours. Their efficiency depends on their size, their surface state and the material used. We realised a fundamental study of the iron nanoparticles synthesis, of their specific magnetic properties and of their hyperthermia response. A detailed analysis of theoretical models could enlighten the optimised properties (superparamagnetism/ferromagnetism transition, high saturation magnetisation MS ). Monodisperse iron nanoparticles are synthesized by the decomposition of the organometallic precursor (Fe{N[Si(CH3)3]2}2)2. The growth mechanism was studied by kinetic studies using electronic microscopy, Mössbauer spectrometry and SQuID measurements. The key role of lamellar structures and acid concentration was described. A new approach, never reported so far, based on the ripening of small iron germs was used for the first time. Particle with tuneable sizes ranging from 1.5 to 11.2 nm were obtained with Ms = 220 Am2.kg-1. An increase of the anisotropic constant was reported for small particles regarding bulk iron (x10 for 1.5 nm and x3 for 5.5 nm). Magnetic configurations have been directly imaged in 30 nm nanocubes thanks to the electronic holography technique. Micromagnetic simulations coupled with holography permit to quantitatively analyse a vortex structure in an isolated cube. A frequency adjustable electromagnet was designed. The first hyperthermia measurements are reported for superparamagnetic iron (of 5.5 and 7.5 nm). A ferromagnetic behaviour corresponding to Stoner-Wohlfarth model was for the first time observed for 14.2 nm FeCo nanoparticle

Skin Microvascular Thrombosis in Fusarium Infection in Two Early Biopsied Cases

Fusarium species cause rare and severe infections. Their incidence is increasing in immunocompromised patients but they are also observed in healthy hosts. Because of the rapid dissemination of infection and the frequent resistance of Fusarium species to antifungal drugs, histopathologic evidence of hyphae is very helpful to obtain the diagnosis rapidly. We report the clinical and pathological features of two patients with initial cutaneous lesions. Cutaneous early biopsies showed microvessel involvement with hyphae and thrombosis. Fusarium infection was confirmed by skin culture. Hyphae within a microvessel thrombus in the skin were highly suggestive of disseminated fungal infection. These pathological features enabled to establish an early diagnosis and to start efficient antifungal treatment. In early cutaneous biopsies of immunocompromised patients, the presence of cutaneous vessel thrombosis can suggest a fungal infection and may help to start specific therapy without delay for these life-threatening infections

Chemical ordering in bimetallic FeCo nanoparticles: From a direct chemical synthesis to application as efficient high-frequency magnetic material

Single-crystalline FeCo nanoparticles with tunable size and shape were prepared by co-decomposing two metal-amide precursors under mild conditions. The nature of the ligands introduced in this organometallic synthesis drastically affects the reactivity of the precursors and, thus, the chemical distribution within the nanoparticles. The presence of the B2 short-range order was evidenced in FeCo nanoparticles prepared in the presence of HDAHCl ligands, combining 57Fe Mössbauer, zero-field 59Co ferromagnetic nuclear resonance (FNR), and X-ray diffraction studies. This is the first time that the B2 structure is directly formed during synthesis without the need of any annealing step. The as-prepared nanoparticles exhibit magnetic properties comparable with the ones for the bulk (Ms = 226 Am2·kg¿1). Composite magnetic materials prepared from these FeCo nanoparticles led to a successful proof-of-concept of the integration on inductor-based filters (27% enhancement of the inductance value at 100 MHz).This work was performed in the frame of TOURS 2015, and the project was supported by the French “Programme de l’économie numérique des Investissements d’Avenir”. We gratefully acknowledge the International Associated Laboratory (LIA)-M2OZART for financial support. Some of the HR-STEM and EELS studies were conducted at the Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragon, Universidad de Zaragoza, Spain. R.A. gratefully acknowledges the support from the Spanish Ministry of Economy and Competitiveness (MINECO) through project MAT2016-79776-P (AEF/FEDER. UE). In IPCMS Strasbourg, the work was supported by the CNRS LIA “NANOFUNC” and the LABEX NIE (no. ANR-11-LABX-0058_NIE)

Stoichiometry-controlled FeP nanoparticles synthesized from a single source precursor

Phase-pure FeP nanoparticles (NPs) have been synthesized through low temperature thermolysis of the single source precursor [(CO)4Fe(PH3)]. Examination of the mechanism demonstrates the central role of the labile CO ligands and the weak P–H bonds to yield stoichiometry controlled FeP materials

Le Forum, Vol. 42 No. 3

https://digitalcommons.library.umaine.edu/francoamericain_forum/1096/thumbnail.jp

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

Habilitation à Diriger des Recherches

The fabrication and integration of sub-millimeter magnetic materials into predefined circuits is ofmajor importance for portable magnetic devices for the telecommunications, automotive, biomedicaland space applications, but remains highly challenging. The present state-of the-art is not satisfactorygiven either the poor magnetic properties of the components (e.g. low magnetization of ferrites) ortheir societal drawbacks (e.g. rarity, toxicity, environmental costs or geopolitical dependence of therare-earth based magnets).There is therefore a need and an opportunity for a process to prepare magnets in the sub-millimeterrange for new developments in microelectronics, nanobiotechnology, energy conversion

Habilitation à Diriger des Recherches

The fabrication and integration of sub-millimeter magnetic materials into predefined circuits is ofmajor importance for portable magnetic devices for the telecommunications, automotive, biomedicaland space applications, but remains highly challenging. The present state-of the-art is not satisfactorygiven either the poor magnetic properties of the components (e.g. low magnetization of ferrites) ortheir societal drawbacks (e.g. rarity, toxicity, environmental costs or geopolitical dependence of therare-earth based magnets).There is therefore a need and an opportunity for a process to prepare magnets in the sub-millimeterrange for new developments in microelectronics, nanobiotechnology, energy conversion

Stable Single-Crystalline Body Centered Cubic Fe Nanoparticles

International audienc

Habilitation à Diriger des Recherches

The fabrication and integration of sub-millimeter magnetic materials into predefined circuits is ofmajor importance for portable magnetic devices for the telecommunications, automotive, biomedicaland space applications, but remains highly challenging. The present state-of the-art is not satisfactorygiven either the poor magnetic properties of the components (e.g. low magnetization of ferrites) ortheir societal drawbacks (e.g. rarity, toxicity, environmental costs or geopolitical dependence of therare-earth based magnets).There is therefore a need and an opportunity for a process to prepare magnets in the sub-millimeterrange for new developments in microelectronics, nanobiotechnology, energy conversion