DNA Nanotubes with Hydrophobic Environments: Toward New Platforms for Guest Encapsulation and Cellular Delivery.

Natural systems combine different supramolecular interactions in a hierarchical manner to build structures. In contrast, DNA nanotechnology relies almost exclusively on DNA base pairing for structure generation. Introducing other supramolecular interactions can expand the structural and functional range of DNA assemblies, but this requires an understanding of the interplay between these interactions. Here, an economic strategy to build DNA nanotubes functionalized with lipid-like polymers is reported. When these polymers are linked to the nanotube using a spacer, they fold inside to create a hydrophobic environment within the nanotube; the nanotube can encapsulate small molecules and conditionally release them when specific DNA strands are added, as monitored by single-molecule fluorescence microscopy. When the polymers are directly linked to the nanostructure without spacers, they interact intermolecularly to form a network of DNA bundles. This morphological switch can be directly observed using a strand displacement strategy. The two association modes result in different cellular uptake behavior. Nanotubes with internal hydrophobic association show dye-mediated mitochondrial colocalization inside cells; while the bundles disassemble into smaller polymer-coated structures that reduce the extent of nonspecific cellular uptake. This approach uncovers parameters to direct the hierarchical assembly of DNA nanostructures, and produces promising materials for targeted drug delivery.