IN-VIVO EVALUATION OF MAGNETITE NANOPARTICLES FOR USE AS A TUMOR CONTRAST AGENT IN MRI

Magnetite nanoparticles, coated by three different artificial polypept ides, were conjugated to an antibody specific to the carcinoembryonic antigen (CEA), To protect the particles from fast blood elimination, t he coats were modified by various sugars, polyethyleneglycol, albumin, and sialoproteins, respectively, The protective effect was determined by using a specific in vitro test and by analyzing the biodistributio n of the nanoparticles in nude mice grafted with CEA-tumors, In partic ular, a prolongation of the blood circulation time has been expected, if a natural modifier is attached to the coated nanoparticles. Althoug h the elimination rate could hardly be decreased by any modifiers, the tumor accumulation is slightly improved by using the specific sialopr otein glycophorin B. The usefulness of nanoparticles as image contrast agents is probably limited by their microdistribution within the tumo r tissue, The requirements for a contrast agent to be highly tissue sp ecific are discussed.