Comparison of dispersion and actuation properties of vortex and synthetic antiferromagnetic particles for biotechnological applications

International audienceMagnetic nanoparticles are receiving an increasing interest for various biotechnological applications due to the capability that they offer to exert actuation on biological species via external magnetic fields. In this study, two types of magnetic particles recently proposed for cancer cells treatment were compared. Both are prepared by top-down approaches and imitate the properties of superparamagnetic particles. One type is made of a single magnetic layer and has a magnetic vortex configuration. The second type has a multilayered structure called synthetic antiferromagnet. Once released in solution, the agglomeration/dispersion of these particles due to their magnetostatic interactions was compared as well as the mechanical torque that they can generate when submitted to an external magnetic fiel

Tissue-specific effects of exercise as NAD + -boosting strategy: Current knowledge and future perspectives.

Nicotinamide adenine dinucleotide (NAD + ) is an evolutionarily highly conserved coenzyme with multi-faceted cell functions, including energy metabolism, molecular signaling processes, epigenetic regulation, and DNA repair. Since the discovery that lower NAD + levels are a shared characteristic of various diseases and aging per se, several NAD + -boosting strategies have emerged. Other than pharmacological and nutritional approaches, exercise is thought to restore NAD + homeostasis through metabolic adaption to chronically recurring states of increased energy demand. In this review we discuss the impact of acute exercise and exercise training on tissue-specific NAD + metabolism of rodents and humans to highlight the potential value as NAD + -boosting strategy. By interconnecting results from different investigations, we aim to draw attention to tissue-specific alterations in NAD + metabolism and the associated implications for whole-body NAD + homeostasis. Acute exercise led to profound alterations of intracellular NAD + metabolism in various investigations, with the magnitude and direction of changes being strongly dependent on the applied exercise modality, cell type, and investigated animal model or human population. Exercise training elevated NAD + levels and NAD + metabolism enzymes in various tissues. Based on these results, we discuss molecular mechanisms that might connect acute exercise-induced disruptions of NAD + /NADH homeostasis to chronic exercise adaptions in NAD + metabolism. Taking this hypothesis-driven approach, we hope to inspire future research on the molecular mechanisms of exercise as NAD + -modifying lifestyle intervention, thereby elucidating the potential therapeutic value in NAD + -related pathologies

Magneto-mechanical treatment of human glioblastoma cells with engineered iron oxide powder microparticles for triggering apoptosis

International audienceIn nanomedicine, treatments based on physical mechanisms are more and more investigated and are promising alternatives for challenging tumor therapy. One of these approaches, called magneto-mechanical treatment, consists in triggering cell death via the vibration of anisotropic magnetic particles, under a low frequency magnetic field. In this work, we introduce a new type of easily accessible magnetic microparticles (MMPs) and study the influence of their surface functionalization on their ability to induce such an effect, and its mechanism. We prepared anisotropic magnetite microparticles by liquid-phase ball milling of a magnetite powder. These particles are completely different from the often-used SPIONs: they are micron-size, ferromagnetic, with a closed-flux magnetic structure reminiscent of that of vortex particles. The magnetic particles were covered with a silica shell, and grafted with PEGylated ligands with various physicochemical properties. We investigated both bare and coated particles' in vitro cytotoxicity, and compared their efficiency to induce U87-MG human glioblastoma cell apoptosis under a low frequency rotating magnetic field (RMF). Our results indicated that (1) the magneto-mechanical treatment with bare MMPs induces a rapid decrease in cell viability whereas the effect is slower with PEGylated particles; (2) the number of apoptotic cells after magneto-mechanical treatment is higher with PEGylated particles; (3) a lower frequency of RMF (down to 2 Hz) favors the apoptosis. These results highlight a difference in the cell death mechanism according to the properties of particles used – the rapid cell death observed with the bare MMPs indicates a death pathway via necrosis, while PEGylated particles seem to favor apoptosis

Réalisation de couches minces magnétiques d'hexaferrite de baryum en vue de concevoir un isolateur coplanaire passif

National audienc

Elaboration de couches minces YIG par pulvérisation cathodique RF pour la réalisation de composants hyperfréquences intégrés

International audienc

Réalisation de couches minces magnétiques d'hexaferrite de baryum en vue de concevoir un isolateur coplanaire passif

Le développement des dispositifs intégrés employant un ferrite est un objectif majeur pour des applications électroniques dans la gamme hyperfréquence (circulateurs et isolateurs). Les ferrites hexagonaux, tel que l'hexaferrite de baryum (BaFe$_{12}$O$_{19}$ ou BaM), présentent un grand intérêt pour de tels dispositifs en raison de leurs grandes résistivités et de leurs perméabilités élevées aux hautes fréquences. Dans cette étude, les couches minces de BaM, sont déposées et optimisées par pulvérisation cathodique RF sur des substrats d'alumine et de silicium. Après dépôt, les films sont amorphes et un recuit thermique à 800$^{\circ}$C est nécessaire pour que les couches de BaM cristallisent et présentent des propriétés magnétiques. Les propriétés magnétiques des couches minces de BaM ont été déterminées par VSM, et on constate que le champ coercitif et l'aimantation à saturation atteignent respectivement 330 kA/m et 500 mT. Des isolateurs sont réalisés par dépôt d'une couche conductrice d'or en utilisant la technique du lift-off qui permet la mise en place du ruban signal ainsi que des plans de masse. Les premiers résultats de mesure en transmission ont montré un effet non réciproque qui atteint 8 dB/cm à 50 GHz

Fabrication of magnetic micro/nanotweezers functionalized and dispersed in solution for bio

International audienc

Fabrication of nanotweezers and their remote actuation by magnetic fields

International audienceA new kind of nanodevice that acts like tweezers through remote actuation by an external magneticfield is designed. Such device is meant to mechanically grab micrometric objects. The nanotweezersare built by using a top-down approach and are made of two parallelepipedic microelements, at leastone of them being magnetic, bound by a flexible nanohinge. The presence of an external magneticfield induces a torque on the magnetic elements that competes with the elastic torque provided by thenanohinge. A model is established in order to evaluate the values of the balanced torques as a functionof the tweezers opening angles. The results of the calculations are confronted to the expected valuesand validate the overall working principle of the magnetic nanotweezers