The long term aim of this project is to develop a multifunctional nanomedicine platform for targeted delivery of nanoheaters and short inference RNA (siRNA) to cancerous tumors as well as the use of magnetic resonance imaging (MRI) as a noninvasive strategy to monitor the therapeutic outcome of the drug therapy. The main obstacle to siRNA therapy is in delivering RNA to the cytoplasm where it can guide sequence-specific mRNA degradation. It has been recognized that a prerequisite for the facile transport of siRNA through the cell membrane is their condensation to discrete nanoparticles. Furthermore, new methods for invasive and in-situ monitoring therapeutic responses of the RNAi are highly desirable for optimization of the therapeutic strategies. Superparamagnetic iron oxide (SPIO) nanoparticles exhibit superparamagnetic behavior, magnetizing strongly under an applied field, but retaining no permanent magnetism once the field is removed. Due to such intrinsic properties, increasing efforts have been devoted to the potential application of magnetic nanoparticles as nanoheaters for hypothermia therapy and as contrast agent for magnetic resonance imaging (MRI). In order to design efficient, multifunctional, and nontoxic siRNA delivery agents for cancer therapy, different sizes of SPIO nanoparticles were fabricated. The SPIO nanoparticle surface was modified so that the SPIO nanoparticles can efficiently provoke siRNA condensation and largely facilitate siRNA internalization into cancer cells. Modifying the surface of the formed siRNA complex with targeting peptides, the siRNAs can be specifically internalized by cancer cells and the internalized siRNAs can efficiently silence their targeting mRNA expression.