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Research into multifunctional nanoparticles is focused on creating an agent for use in an all-in-one multimodal imaging system that includes diagnostic imaging, drug delivery, and therapeutic monitoring. We designed a new dual-modality tumor-targeting agent with a new tumor-targeting molecule, oleanolic acid (OA), which is derived from a natural compound and coupled with a macrocyclic chelating agent such as 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA), iron oxide nanoparticles (IONP), and radiolabeling components such as (68)Ga for dual-modality positron emission tomography (PET)/magnetic resonance imaging (MRI). We attempted to obtain fusion PET/MR images with the (68)Ga-NOTA-OA-IONP hybrid tumor-targeting imaging agent using colon cancer (HT-29) xenograft mice models. The HT-29 cancer cells showed high uptake of (68)Ga-NOTA-OA-IONP, which also had an inhibitory effect on the cells. Moreover, we obtained PET and MRI tumor images as well as fusion PET/MRI images of the tumors using (68)Ga-NOTA-OA-IONP. Therefore, the dual-modality cancer-targeting radiolabeled nanoparticle reported here is a potent imaging agent that is suitable for PET, MRI, and PET/MRI-based diagnosis of tumors; it also has the advantage of not only detecting tumor functionality, but also simultaneously aiding in tumor resolution.

Polo-like kinase 1 (Plk1) is a regulator of cell cycle progression during mitosis; it is overexpressed in many different tumors and has been implicated as a potential antimitotic target. Plks are characterized by the presence of a highly conserved C-terminal polo-box domain (PBD) that is involved in regulating kinase activity. The phosphopeptide Pro-Leu-His-Ser-p-Thr (PLHSpT) is a potent selective inhibitor of the PBD of human plk1 that acts by inducing mitotic arrest and apoptotic cell death in cancer cells. We synthesized cRGDyK-S-S-CPLHSpT to exploit the drug delivery and molecular imaging using positron emission tomography (PET). The peptide was blocked dramatically proliferation of tumor in vitro and in vivo. It was attempted to develop and show a tumor PET image with the radiolabeled-peptide. Here we showed the peptide is promising not only as an anticancer drug, but also as a radioligand for tumor diagnosis with PET. We expect that our contribution will provide new insights into the design of Plk1 peptide inhibitors and have significant implications for anticancer therapy and tumor diagnosis.