DNA and peptides are two of the most commonly used biomolecules for building self-assembling materials, but few examples exist of hybrid nanostructures that contain both components. Here we report the modification of two peptides that comprise a coiled-coil heterodimer pair with unique DNA handles in order to link DNA origami nanostructures bearing complementary strands into micrometer-long one-dimensional arrays. We probed the effect of number of coils on self-assembly and demonstrated the formation of structures through multiple routes: one-pot assembly, formation of dimers and trimers and an alternating copolymer of two different origami structures, and stepwise assembly of purified structures with coiled-coil conjugates. Our results demonstrate the successful merging of two distinct self-assembly modes to create hybrid bionanomaterials expected to have a range of potential applications in the future.

Peptide–oligonucleotide conjugates (POCs) are covalent constructs that link a molecule like DNA to a synthetic peptide sequences.

The programmable synthesis of rationally engineered crystal architectures for the precise arrangement of molecular species is a foundational goal in nanotechnology, and DNA has become one of the most prominent molecules for the construction of these materials. In particular, branched DNA junctions have been used as the central building block for the assembly of 3D lattices. Here, crystallography is used to probe the effect of all 36 immobile Holliday junction sequences on self-assembling DNA crystals. Contrary to the established paradigm in the field, most junctions yield crystals, with some enhancing the resolution or resulting in unique crystal symmetries. Unexpectedly, even the sequence adjacent to the junction has a significant effect on the crystal assemblies. Six of the immobile junction sequences are completely resistant to crystallization and thus deemed “fatal,” and molecular dynamics simulations reveal that these junctions invariably lack two discrete ion binding sites that are pivotal for crystal formation. The structures and dynamics detailed here could be used to inform future designs of both crystals and DNA nanostructures more broadly, and have potential implications for the molecular engineering of applied nanoelectronics, nanophotonics, and catalysis within the crystalline context.

Biomaterials with dynamically tunable properties are critical for a range of applications in regenerative medicine and basic biology. In this work, we show the reversible control of gelatin methacrylate (GelMA) hydrogel stiffness through the use of DNA crosslinkers. We replaced some of the inter-GelMA crosslinks with double-stranded DNA, allowing for their removal via toeholdmediated strand displacement. The crosslinks could be restored by adding fresh dsDNA with complementary handles to the hydrogel. The elastic modulus (G') of the hydrogels could be tuned between 500 and 1000 Pa, reversibly, over two cycles without degradation of performance. By functionalizing the gels with a second DNA strand, it was possible to control the crosslink density and a model ligand in an orthogonal fashion with two different displacement strands. Our results demonstrate the potential for DNA to reversibly control both stiffness and ligand presentation in a protein-based hydrogel, and will be useful for teasing apart the spatiotemporal behavior of encapsulated cells.

The integration of proteins with DNA nanotechnology would enable materials with diverse applications in biology, medicine, and engineering. Here, we describe a method for the incorporation of bioactive fibronectin domain proteins with DNA nanostructures using two orthogonal coiled-coil peptides. One peptide from each coiledcoil pair is attached to a DNA origami cuboid in a multivalent fashion by attaching the peptides to DNA handles. These structures can then be assembled into one-dimensional arrays through the addition of a fibronectin domain linker genetically fused with the complementary peptides to those on the origami. We validate array formation using two different self-assembly protocols and characterize the fibers by atomic force and electron microscopy. Finally, we demonstrate that surfaces coated with the protein−DNA nanofibers can serve as biomaterial substrates for fibroblast adhesion and spreading with the nanofibers showing enhanced bioactivity compared to that of the monomeric protein.