Purpose Tumor cells can be effectively inactivated by heating\nmediated by magnetic nanoparticles. However, optimized\nnanomaterials to supply thermal stress inside the tumor remain\nto be identified. The present study investigates the therapeutic\neffects of magnetic hyperthermia induced by superparamagnetic\niron oxide nanoparticles on breast (MDA-MB-231) and pancreatic\ncancer (BxPC-3) xenografts in mice in vivo.\nMethods Superparamagnetic iron oxide nanoparticles, synthesized\neither via an aqueous (MF66; average core size 12 nm) or\nan organic route (OD15; average core size 15 nm) are analyzed\nin terms of their specific absorption rate (SAR), cell uptake and\ntheir effectivity in in vivo hyperthermia treatment.\nResults Exceptionally high SAR values ranging from 658�±\n53 W*gFe\n?1 for OD15 up to 900�±22 W*gFe\n?1 for MF66 were\ndetermined in an alternating magnetic field (AMF, H=15.4 kA*m?1\n(19 mT), f=435 kHz). Conversion of SAR values into systemindependent\nintrinsic loss power (ILP, 6.4�±0.5 nH*m2*kg?1\n(OD15) and 8.7�±0.2 nH*m2*kg?1 (MF66)) confirmed the markedly\nhigh heating potential compared to recently published data.\nMagnetic hyperthermia after intratumoral nanoparticle injection\nresults in dramatically reduced tumor volume in both cancer models,\nalthough the applied temperature dosages measured as CEM43T90\n(cumulative equivalent minutes at 43�°C) are only between 1 and\n24 min. Histological analysis of magnetic hyperthermia treated tumor\ntissue exhibit alterations in cell viability (apoptosis and necrosis) and\nshow a decreased cell proliferation.\nConclusions Concluding, the studied magnetic nanoparticles\nlead to extensive cell death in human tumor xenografts and are\nconsidered suitable platforms for future hyperthermic studies.
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