Ultrasmall superparamagnetic iron oxide nanoparticles and uses thereof

The present invention provides biomimetic contrast agents, dual functional contrast agents effective for therapeutic gene delivery and magnetic nanoparticles which comprise functionalized iron oxide nanoparticle cores, one of an inert gold layer, a layer of inert metal seeds or a silica layer and, optionally, one or both of an outer gold-silver nanoshell or a targeting ligand attached to the inert gold layer or the gold-silver nanoshell. Also provided are methods of in vivo magnetic resonance imaging, of treating primary or metastatic cancers or of ablating atherosclerotic plaque using the contrast agents and magnetic particles. In addition, kits comprising the biomimetic contrast agents, dual contrast agents and magnetic nanoparticles.