A nanostructured iron oxide (NanoFe 3 O 4 , particle size ca. 25 nm and roughness ca. 21 nm) film deposited onto a hydrolyzed indium-tin-oxide (ITO) coated glass plate has been used to immobilize cholesterol oxidase (ChOx) to fabricate an impedimetric cholesterol sensor. Electrochemical studies reveal that surface charged Fe 3 O 4 nanoparticles provide better conformation for ChOx loading resulting in enhanced electron transfer between ChOx and the electrode. Impedimetric response studies of the ChOx/NanoFe 3 O 4 /ITO bioelectrode exhibit improved linearity (2.5 -400 mg/dL), low detection limit (0.25 mg/dL), fast response time (25 s), high sensitivity (86 W/mg dL À1 /cm À2) and a low value of the Michaelis-Menten constant (K m , 0.8 mg/dL) with a regression coefficient of 0.997.

A phenomenological model for the asymmetric giant magnetoimpedance (GMI) in fieldannealed amorphous ribbons is developed. The effect of a surface crystalline layer on the GMI response is described in terms of an effective bias field appearing due to a coupling between the crystalline layer and amorphous phase. It is shown that the presence of the bias field changes drastically the GMI profile. At low frequencies, the domain-walls motion leads to a steplike change in the GMI response. At high frequencies, the domain-walls motion is damped, and the GMI profile exhibits asymmetric two-peak behavior. The calculated dependences are shown to be in a qualitative agreement with results of experimental studies of the asymmetric GMI in field-annealed Co-based amorphous ribbons.

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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.