Cobalt doped magnetite Co²⁺_0.1Fe²⁺_0.9Fe³⁺₂O₄ nanocrystals were synthesized chemically using simple one step
coprecipitation in the absence and presence of the magnetic field. The nanocrystals were characterized by
transmission electron microscopy (TEM), X-ray diffraction (XRD), magnetization studies by vibrational spectroscopy
magnetometer (VSM). The signal intensity of the prepared nanoparticles was measured by magnetic
resonance imaging (MRI). The cytotoxicity of the two samples versus W138 normal lung cells and AS49 lung
cancer cells was investigated by MTT assay, in vitro. The TEM images showed non-spherical and aggregated
nanoparticles, heterogeneously dispersed with 100 nm average size. The XRD and selected area electron diffraction
of the two samples revealed good crystallinity for both samples. The room temperature magnetization
curves demonstrate the general ferrimagnetic trend with a clear difference in the coercivity and the remanence
keeping the saturation magnetization nearly stable. The measured MR signal intensity was well-matched with
the result of the M-H loops where the sample prepared in the absence of the field was a promising T2 contrast
agent. Both samples have low cytotoxicity compared to Doxorubicin.