The synthesis, in vitro, and in vivo The particles consist of a chainlike aggregation of iron oxide (IO) cores in a dextran coating. When conjugated with a tumor-targeting peptide, they interact more effectively with a tumor-based target in vitro relative to spherical nanoparticles. Untargeted NW display similar in vivo circulation times and enhanced passive accumulation in mouse xenograft tumors relative to untargeted spherical IO nanoparticles.