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

In 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.

Optical response of magnetically actuated biocompatible membranes

Biocompatible suspended magneto-elastic membranes were prepared. They consist of PDMS (polydimethylsiloxane) films, with embedded arrays of micrometric magnetic pillars made with lithography techniques. For visible light wavelengths, our membranes constitute magnetically tunable optical diffraction gratings, in transmission and reflection. The optical response has been quantitatively correlated with membrane structure and deformation, through optical and magneto-mechanical models. In contrast to the case of planar membranes, the diffraction patterns measured in reflection and transmission vary very differently upon magnetic field application. Indeed, the reflected beam is largely affected by the membrane bending, whereas the transmitted beam remains almost unchanged. In reflection, even weak membrane deformation can produce significant changes of the diffraction patterns. This field-controlled optical response may be used in adaptive optical applications, photonic devices, and for biological applications.

Bistable coupling states measured on single Co nanoclusters deposited on CoO(111)

We describe novel features of the induced magnetic anisotropy in Co nanoclusters coupled with a CoO(111) layer. Individual cluster magnetism was studied using new microbridge superconducting quantum interference devices. Intrinsically, the Co clusters are single domains with an effective anisotropy constant K(F)≈1.5×10(6) erg·cm(-3). A bistable state of the ferromagnetic-antiferromagnetic coupling is revealed, with a maximum bias systematically observed along CoO[10 ̅1] and an interfacial coupling energy of 0.9 erg·cm(-2). The small bias observed in cluster assembly results from an averaging over the two opposite stable states.

A versatile nanotechnology to connect individual nano-objects for the fabrication of hybrid single-electron devices

We report on the high yield connection of single nano-objects as small as a few nanometres in diameter to separately elaborated metallic electrodes, using a 'table-top' nanotechnology. Single-electron transport measurements validate that transport occurs through a single nano-object. The vertical geometry of the device natively allows an independent choice of materials for each electrode and the nano-object. In addition ferromagnetic materials can be used without encountering oxidation problems. The possibility of elaborating such hybrid nanodevices opens new routes for the democratization of spintronic studies in low dimensions.

Effects of raising lambs in a cold or a warm environment on animal performance and carcass traits

A 2 x 2 x 2 factorial arrangement was conducted over two consecutive winters to compare growth and carcass traits of ram and ewe lambs in a cold or warm environment (noninsulated, unheated vs. an insulated and heated barn with minimum inside temperature (T) between 5 and 10°C). Each winter, 14 pairs of lambs of each sex were randomly allocated to either a cold or warm environment (average weight of 23.8 kg ± 0.6 and 22.4 kg ± 2.0 in 2003 and 2004, respectively). They were fed hay and concentrate ad libitum until they reached 42 to 48 kg body weight (BW) when they were slaughtered. Carcass traits were then evaluated. The average temperature in the cold environment was -7.49 and -4.74°C in 2003 and 2004, respectively, vs. +6.25 and +10.50°C, respectively, in the warm environment. There were no differences (P > 0.05) in growth performance and carcass traits between lambs raised in a cold or a warm environment. However, there was a tendency for lambs raised in a cold environment to have higher average daily gain (ADG) (P = 0.06) and to take less time to market (P = 0.09). Results suggest that it is possible to raise lambs in a cold environment without having any detrimental effect on performance and carcass quality. Key words: Lamb, environment, cold, performance, growth, carcass

Liquid chromatographic/mass spectrometric determination of biologically active alkaloids in extracts of Peschiera fuschiaefolia

Four alkaloids were isolated from an alcoholic extract of the bark from the stem of Peschiera fuschiaefolia. Two of these compounds, voacamine and voacamidine, are dimeric alkaloids which are thought to be responsible for the antimalarial activity of these extracts. The mass spectra and the response factors of these four compounds were obtained by liquid chromatography/mass spectrometry in the electrospray positive ionization mode. The concentrations of these alkaloids were measured in two different P. fuschiaefolia extracts. The ion chromatograms of the two extracts were compared on the basis of their [M + H](+) and [M + 2H](+2) ions characteristic of various alkaloids previously isolated from P. fuschiaefolia bark. The two extracts were found to differ mostly in the relative concentrations of the dimeric alkaloids.