The unique electromagnetic and biologic properties of nanomaterials are being harnessed to build powerful new medical technologies. Particularly, there have been recently increasing interests in cancer nanotechnology, wherein nanomaterials play an important role in ultrasensitive imaging, targeting, and therapy of cancer. However, these nanomaterials typically function as individual units and are designed to independently perform their tasks. In this dissertation, new cooperative nanosystems consisting of two distinct nanomaterials that work together to target, identify, or treat tumors in vivo were studied. In the first two chapters, the synthesis of worm-shaped dextran-coated iron oxide nanoparticles (nanoworms, NW) exhibiting substantial in vivo circulation times and significant tumor targeting when coated with tumor-homing peptides were studied. NWs are also found to display a greater magnetic resonance (MR) response than the spherical nanoparticles. Next, two types of multifunctional nanoparticles were fabricated for simultaneous detection and treatment of cancer. Micellar hybrid nanoparticles (MHN) that contain magnetic nanoparticles, quantum dots, and an anti-cancer drug doxorubicin (DOX) within a single PEG-modified phospholipid micelle were first prepared. Simultaneous multimodal imaging (MR and fluorescence) and targeted drug delivery in vitro and in vivo was performed using DOX- incorporated targeted MHN. Secondly, luminescent porous silicon nanoparticles (LPSINP) that were drug-loadable, biodegradable and relatively non-toxic were prepared. In contrast to most inorganic nanomaterials, LPSINP were degraded in vivo in a relatively short time with no noticeable toxicity. The clearance and degradation of intravenously injected LPSINP in the bladder, liver, and spleen were established by whole-body fluorescence imaging. Finally, two types of cooperative nanomaterials systems to amplify targeting and deliver drugs efficiently to regions of tumor invasion were developed. Gold nanorods localized through vascular circulation to the tumor region, where they reported their location and converted near infrared (NIR) radiation to thermal energy. The local photothermal heating enabled to enhance tumor-specific drug release from thermally labile therapeutic liposomes or induce more binding sites for targeted therapeutic liposomes. The combination of local hyperthermia and chemotherapy in the cooperative nanosystems significantly enhanced therapeutic efficacy relative to individual therapies.

The incidence of adverse effects and pathogen resistance encountered with small molecule antibiotics is increasing. As such, there is mounting focus on immunogene therapy to augment the immune system's response to infection and accelerate healing. A major obstacle to in vivo gene delivery is that the primary uptake pathway, cellular endocytosis, results in extracellular excretion and lysosomal degradation of genetic material. Here we show a nanosystem that bypasses endocytosis and achieves potent gene knockdown efficacy. Porous silicon nanoparticles containing an outer sheath of homing peptides and fusogenic liposome selectively target macrophages and directly introduce an oligonucleotide payload into the cytosol. Highly effective knockdown of the proinflammatory macrophage marker IRF5 enhances the clearance capability of macrophages and improves survival in a mouse model of Staphyloccocus aureus pneumonia.