The aim of this study was to create vector superparamagnetic nanoparticles for tumor cell visualization in vivo by magnetic resonance tomography. A method for obtaining superparamagnetic nanoparticles based on ferric oxide with the magnetic nucleus diameter of 12 ± 3 nm coated with BSA and forming stable water dispersions was developed. The structure and size of the nanoparticles were studied by transmissive electron microscopy, dynamic light scattering, and x-ray phase analysis. Their T2 relaxivity was comparable with that of the available commercial analog. Low cytotoxicity of these nanoparticles was demonstrated by MTT test on primary and immortalized cell cultures. The nanoparticles were vectorized by monoclonal antibodies to connexin 43 (Cx43). Specific binding of vectorized nanoparticles to C6 glioma Cx43-positive cell membranes was demonstrated. Hence, vector biocompatible nanoparticles with high relaxivity, fit for use as MRT contrast for the diagnosis of poorly differentiated gliomas, were created.