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RNA nanoparticles based on phi29 3-way junction (3WJ) RNA motif have been used as drug carriers for various cancer types. The RNA nanoparticles are thermodynamically and biologically stable with 2′-fluoro modifications. The size of RNA nanoparticles ranges from ~8.0 to 20.0 nm leading to favorable PK/PD profiles. Moreover, the size range enables the penetration of nanoparticles into tumor tissues via passive targeting and allows for receptor-mediated active endocytosis when targeting ligands are included. The RNA nanoparticles are proven to be non-immunogenic with low toxicity. Furthermore, the hydrophilic RNA nanoparticles could significantly improve the solubility of small hydrophobic molecules conjugated to RNA nanoparticles.We first designed a new multivalent RNA nanoparticle harboring hepatocyte targeting ligands, one copy of miR122, and 24 copies of Paclitaxel for HCC treatment. The hepatocyte targeting ligands introduce tumor specificity to the RNA nanoparticles. The RNA nanoparticles carrying miR122 and PTX were delivered to the liver cancer cells efficiently via passive targeting and active receptor-mediated endocytosis by hepatocyte targeting ligands. The miR122 efficiently silenced the drug exporters and the oncogenic proteins. The synergistic effect between miR122 and PTX was confirmed by HSA (Highest Single Agent) synergy model. In vivo studies on mice xenografts revealed that the RNA nanoparticle predominantly accumulated in HCC tumor sites and efficiently inhibited the tumor growth after multiple IV injections. This research demonstrates the potential of the multivalent RNA nanoparticles to conquest liver cancer, a currently lethal disease.Next, we characterized the RNA nanoparticles' PK profile and biodistribution using radioactivetracers. Previous PK studies mainly relied on the use of fluorescent dye for in vivo imaging, and as a result, raised the concern of interference by nonspecific auto-fluorescence and matrix effects on fluorescence emission intensities. In this study, we compare the effects of fluorescent and radioactive markers on biodistribution. We quantitatively demonstrated that approximately 5% of radiolabeled therapeutic RNA nanoparticles accumulated in tumors between 4-8 hours after systemic injection into xenografted mice. The primary pathway for excretion and elimination of our nanoparticles was via kidney filtration. The 10-nm ligand-bearing RNA nanoparticles reached tumors within 30 minutes and were cleared from healthy organs after 1.5 hours while remaining in tumors for over 48 hours, which is the longest time tested so far. The high efficiency of tumor targeting, fast clearance and excretion from the body, and little to no accumulation in healthy organs further illustrate the high therapeutic potential of RNA nanoparticles in cancer treatment as delivery agents of siRNA, miRNA, or chemical drugs.We also utilized optical tweezers and in vivo fluorescence imaging technologies to discern the rubber-like property of RNA nanoparticles. RNA nanoarchitecture is stretchable and shrinkable by optical tweezer with multiple repeats while remaining intact. Compared to rigid nanoparticles, RNA nanoparticles display higher tumor-targeting abilities and less accumulation in non-target organs. Considering the controllable shape, size, rubbery property, and favorable PK profile, RNA holds great potential for cancer treatment options with targeted delivery.