The present invention provides a biomimetic contrast agent comprising an amine-functionalized iron (II) oxide/iron(III) oxide nanoparticle core a targeting ligand attached to the nanoparticle core via a linker and an inert outer layer of a hydrophilic polymer conjugated to the targeting ligand and imaging methods using the biomimetic contrast agents. Also, provided is a dual functional contrast agent comprising a metal-doped iron (II) oxide/iron(III) oxide nanoparticle core, an inert layer of gold coating the nanoparticle core and a biodegradable cationic polymer linked thereto. The dual functional contrast agent is complexed to a therapeutic gene and when transfected into mesenchymal stem cells comprises a dual contrast agent and gene delivery system. In addition, methods of using the dual functional system are provided. Furthermore, kits comprising the biomimetic contrast agents and the dual contrast agent and gene delivery system are provided.
