382154 DNA Nanotubes and Nanotapes Formed Via Self-Assembly of ssDNA-Amphiphiles
DNA is a popular material for constructing complex, multi-dimensional nanostructures due to its ability to organize via Watson-Crick base-pairing in a precise and predictable manner. Popular approaches to create nanostructures from DNA include DNA origami, DNA tile assembly, and DNA brick assembly, each of which rely on numerous strands of single-stranded DNA (ssDNA) with different and complimentary sequences to direct the DNA assembly process. These approaches and others have been used to create numerous structures including three-dimensional polyhedra, two-dimensional lattices, and nanoribbons and nanotubes. An alternate approach to direct the assembly of ssDNA is to conjugate a hydrophobic moiety (i.e., polymer or lipid) to the ssDNA to form an amphiphilic molecule that spontaneously self-assembles when added to aqueous solutions. It was recently shown by our group that the type of molecular spacer linking a ssDNA headgroup to a lipid-like molecule affects the amphiphile’s assembly and produces spherical micelles or bilayer nanotapes (flat or twisted) depending on the type of spacer used in the amphiphile design.
In this work we explore the impact of the ssDNA length and secondary structure on the self-assembly of ssDNA-amphiphiles using circular dichroism and cryo-transmission electron microscopy (cryoTEM). We found that ssDNA-amphiphiles with 10, 25, and 40 nucleotide ssDNA sequences form a variety of structures including spherical micelles, twisted or helical nanotapes, and nanotubes. Interestingly, our cryoTEM images capture for the first time ssDNA-amphiphile structures that are transitioning between nanotapes and nanotubes, which suggests an assembly mechanism that includes transitions from twisted nanotapes to helical nanotapes to ssDNA nanotubes. The ability to form structures of great interest, such as nanotubes, from a single ssDNA sequence in a simple way to the common DNA assembly techniques could be useful for DNA nanotechnology applications that can trade complexity in supramolecular structure for ease-of-design and a robust assembly process.