Dynamic Actuation and Hierarchical Assembly of Iron Oxide-Coated DNA Origami

Deoxyribonucleic acid (DNA)-based nanomaterials can template growth of nanostructured films on their surfaces, generating complex morphologies. However, previous work has not explored the application of this approach to DNA nanostructures capable of large shape transformations. This study investigated the application of in situ reduction chemistries to dynamic DNA origami materials. Extending beyond past work using gold or silica, iron oxide nanostructures were grown on a variety of DNA origami geometries at different iron:DNA origami molar ratios (i.e., 25,000 to 1,000,000). Growth was visualized using transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS), which indicated the presence of electron dense iron oxide. Structures generally retained their geometric form factors, with some modifications observed in TEM. Structures formed at the highest ratios (i.e., 500,000 to 1,000,000) aggregated, providing an upper limit for this method. DNA origami nanostructures were programmed with single-stranded DNA (ssDNA) overhangs for binding complementary ssDNA-modified cargoes, inducing structural transformations, and for hierarchical assembly. Overhang functionality in coated structures was assessed by gold nanoparticle (AuNP) binding, actuation of two different DNA origami nanostructures, and polymerization into nanotube bundles. These findings indicate that the in situ reduction technique can be applied to dynamic DNA origami structures, retaining their capacity for large shape changes, and that overhangs presented by those structures retain functionality. This approach enables dynamic transformation of individual inorganic nanostructure shapes and assembly of units into larger, arrayed materials.