Absorption Mechanisms of Poly I:C RNA Onto Zinc Oxide Nanoparticles: Maximizing The Payload

Development of stable RNA‐nanoparticle complexes will advance RNA therapeutics. Given the complexity of bionano interactions, it is crucial to develop efficient RNA loading techniques, to optimize RNA payload. Here we investigated the loading of anti‐cancer RNA (Poly I:C) using two different sizes of ZnO (14, 100 nm) and three different loading techniques; 1) Centrifugation, 2) Incubation 3) Reannealing. The amount of RNA binding per mg nanoparticle was quantitated using the absorption of RNA at 260 nm by UV‐visible absorption spectroscopy. In order to evaluate the number of binding sites and the binding kinetics, the samples were characterized by fluorescence spectroscopy using the modified Stern‐Volmer equation. In general, the RNA payload per mg nanoparticle was observed to be higher for 14 nm nanoparticles than the 100 nm due to larger surface area. Also, reannealing was most efficient with maximum payload of 20μg per mg of the 14 nm nanoparticles. Reannealing enhances the binding constant (k b = 6.8×10 3 g −1 L) as well as the number of binding sites (n = 5) available on the surface of ZnO for one RNA. Taken together the data suggest three different mechanisms of RNA interaction with nanoparticle: physisorption, aggregation, and chemisorption. TEM analysis confirms an RNA corona surrounding the nanoparticle. This is the first example we are aware of an RNA corona surrounding an un‐functionalized inorganic non‐polymeric nanoparticle. Based on our spectroscopy analysis comparing these three techniques, reannealing poly I:C to 14 nm ZnO nanoparticle, demonstrates the highest payload and suggests a possible process for designing the optimal delivery system. Support or Funding Information This work was supported by NCI 7R15CA139390‐03