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PurposeTumor cells can be effectively inactivated by heating mediated by magnetic nanoparticles. However, optimized nanomaterials to supply thermal stress inside the tumor remain to be identified. The present study investigates the therapeutic effects of magnetic hyperthermia induced by superparamagnetic iron oxide nanoparticles on breast (MDA-MB-231) and pancreatic cancer (BxPC-3) xenografts in mice in vivo.MethodsSuperparamagnetic iron oxide nanoparticles, synthesized either via an aqueous (MF66; average core size 12 nm) or an organic route (OD15; average core size 15 nm) are analyzed in terms of their specific absorption rate (SAR), cell uptake and their effectivity in in vivo hyperthermia treatment.ResultsExceptionally high SAR values ranging from 658 ± 53 W*gFe−1 for OD15 up to 900 ± 22 W*gFe−1 for MF66 were determined in an alternating magnetic field (AMF, H = 15.4 kA*m−1 (19 mT), f = 435 kHz). Conversion of SAR values into system-independent intrinsic loss power (ILP, 6.4 ± 0.5 nH*m2*kg−1 (OD15) and 8.7 ± 0.2 nH*m2*kg−1 (MF66)) confirmed the markedly high heating potential compared to recently published data. Magnetic hyperthermia after intratumoral nanoparticle injection results in dramatically reduced tumor volume in both cancer models, although the applied temperature dosages measured as CEM43T90 (cumulative equivalent minutes at 43°C) are only between 1 and 24 min. Histological analysis of magnetic hyperthermia treated tumor tissue exhibit alterations in cell viability (apoptosis and necrosis) and show a decreased cell proliferation.ConclusionsConcluding, the studied magnetic nanoparticles lead to extensive cell death in human tumor xenografts and are considered suitable platforms for future hyperthermic studies.Electronic supplementary materialThe online version of this article (doi:10.1007/s11095-014-1417-0) contains supplementary material, which is available to authorized users.

A detailed study of magnetization processes has been carried out on a new type of hard magnetic material. The material Nd3.8Fe73.3V3.9B18.0Si1.0 is unique among hard magnets due to the exchange coupling of two ferromagnetic materials, one of which is soft and the other hard. The combination of the two materials gives a composite material, with a high magnetic saturation and coercivity. The irreversible components of magnetization for the material were examined using the demagnetizing remanence curve (DCD) and the isothermal remanence curve (IRM) for the magnetizing case. The nature of the interactions in the material were also studied using the delta M plot obtained via the DCD and IRM remanence curves. The reversible components were obtained from the M-H loop data, Mrev=Mtot-Mirr. Measurements of magnetic time dependence have also been carried out to provide fluctuation field data, Hf, from which activation volumes of reversal, v, for various fields have been obtained. The mean activation field Ha, obtained by extrapolating the linear portion of the fluctuation field data to zero, is the same as the mean nucleation field Hn obtained from the reversible components, Mrev of the demagnetizing remanence curve. Assuming spherical volumes of reversal, the dimensions of the soft and hard phases, obtained from the mean volume of activation, v(Hn) are close to the critical dimensions of the soft and hard phases.

Measurements of time dependent magnetization have been made on samples of partially oriented and non-oriented barium ferrite recording media. From these data and complementary measurements of the irreversible susceptibility, the variation of the fluctuation fleld Xf with applied fleld hae been obtained. For the non-oriented sample the variation is quite broad whereas for the aligned case a rapid variation is found. These different types of behaviour are attributed to the marked differences in the interaction conflgurations in the two samples. The interaction in the samples have been characterised via the delta I technique.

We describe a method for the determination of the heating power of magnetic nanoparticle colloids which have potential for application in the remedial treatment of malignant and non-malignant tumours. The method is based upon a comparison between the heating power observed when the colloid is exposed to a radio frequency magnetic field and that which is observed using a resistive electrical heater. A new design of the measurement cell has been made which has the advantages of reducing or eliminating the effects of convection, ensuring the measurement is made in a magnetic field of known uniformity and that the heat losses in the system are constant and minimized under both magnetic and Joule heating.