Super paramagnetic iron oxide nanoparticles (SPIONs) coated with biocompatible materials are used for in vivo applications, such as contrast agent for magnetic resonance imaging (MRI), for tumor therapy or cardiovascular disease. Biomedical application requires the biocompatible SPION, which is stable and well dispersed in water at physiological pH or in physiological salinity. Many different approaches are used for generation of functionalized nanoparticles in order to obtain the required properties for biomedical uses. In order to obtain biocompatible SPION, SPIONs with size 15-25 nm have been synthesized and these SPIONs have been coated with poly (ethylenimine) (PEI), poly (vinyl alcohol) PVA and Pluronics p-123(PEG-PPG-PEG).High resolution Field Emission Scanning Electron Microscope FESEM, X-Ray diffraction studies, Fourier Transform Infra Red Spectroscopy FTIR, Laser Scattering Particle Size Analyzer and Vibrating Sample Magnetometer VSM were employed to investigate the morphological, crystalline and magnetic properties of nanoparticles. For biomedical applications such as MRI, drug-delivery and hyperthermia, the nanoparticles have to be biocompatible, have a large enough moment for targeting and display super paramagnetic behavior .Owing to their non-toxicity and strong magnetic susceptibility, magnetite and maghemite Nanoparticles have been extensively researched for biomedical applications. Below a certain Size (15 nm for magnetite), magnetite nanoparticles display super paramagnetic behavior with zero remanence and zero coercivity. Vibrating Sample Magnetometer studies were carried out to study the effect of phase transformations on the magnetic properties of the nanoparticles. The samples were analyzed by VSM at room temperature to find the saturation magnetization, Ms, remnant magnetization, Mr and coercivity, He of various polymer coated Iron Oxide nanoparticles. The poly (ethylenimine) coated iron oxide nanoparticles showed better results with low coercivity and low remnant field compared with uncoated and poly vinyl alcohol coated iron oxide nanoparticles. The PEI-coated iron oxide nanoparticles, PVA-coated particles and Pluronics -coated particles were found to be well dispersed in water as they have a hydrophilic outer surface containing hydroxyl and amine group. This hydrophilic outer surface will enhance their bio activity. Therefore they become a very good drug carrier for biomedical applications.

Key words: SPIONS, poly (ethylenimine), Pluronics p-123, Field Emission Scanning Electron Microscope, Vibrating Sample Magnetometer