Biocompatible magnetic fluids are applied for medical diagnosis and therapy. In this work, magnetic particles were prepared and then were coated with various 2nd surfactants for obtaining the water-based magnetic fluids by chemical coprecipitation. Toxicity of each fluid sample was estimated using SpragueDawley rats. Finally, the used samples resulted in severe toxic reactions through in vitro, indicating that all samples can not be seen as biocompatible agents or suggesting the possibilities of another effects.1 Introduction Recently, the synthesis of magnetic materials in nanoscale has become a field of intense study due to the novel mesoscopic properties shown by particle dimension located in the transition region between atoms and bulk solids. Based on their unique physical, thermal, and mechanical properties, superparamagnetic nanoparticles offer a high potential for several applications in different areas such as ferrofluids, color imaging, magnetic refrigeration, detoxification of biological fluids, magnetically controlled transport of anti-cancer drugs, magnetic resonance imaging contrast enhancement and magnetic cell separation [1][2][3][4].A difficulty related to the nature of ferrofluids is that the nanoparticles with a large ratio of surfacearea to volume tend to agglomerate in order to reduce their surface energy by strong magnetic dipoledipole attraction between particles. Therefore, one of the main problems in producing stable magnetic fluid is to prevent the agglomeration during synthesis and coating processes [5]. Since ionic magnetic fluids are usually toxic materials, the coated layer using a biological molecule such as citrate would provide some protection against toxicity [6].Thus, the purpose of this work was to investigate the toxicity of each surfactant coated magnetic fluid through intravenous administration in Sprague-Dawley rats.

Doxorubicin-loaded magnetic particles with lecithin and polyethylene glycol as an interlayer were synthesized by multi-step process of high temperature thermal decomposition and ultrasonic, respectively. The change of particle size and the magnetic property were investigated for the estimation of the carrier characteristic with doxorubicin addition. And, the loading efficiency of drug and the loaded drug released fraction were discussed for the estimation of drug effect. Also, the remedial efficiency of adsorbed drug on the magnetic nanoparticle was investigated by comparing the cytotoxicity of tumor cell between bareand doxorubicin-loaded magnetic nanoparticles. And, in-vivo test was performed to estimate the effect of anticancer therapy by using C57BL/6 mice as an animal sample.

The monodispersed hydrophilic magnetic fluids with nanometric M‐ferrite (M=Cu, Co, Ca, Ni) particles were prepared by sonochemical method. The substituted amounts of M elements were analyzed with different x values by ICP‐AES quantitatively for MxFe3‐xO4 particles. The biological tests were performed to observe the proper dosage and the toxicity by using S.D. rat with different core sources. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)