Chemically reversible hydrogels: The dynamic reorganization of some cellular biopolymers in response to signals has inspired efforts to create artificial materials with similar properties. Freeman et al. created hydrogels based on peptide amphiphiles that can bear DNA strands that assemble into superstructures and that disassemble in response to chemical triggers. The addition of DNA conjugates induced transitions from micelles to fibers and bundles of fibers. The resulting hydrogels were used as an extracellular matrix mimic for cultured cells. Switching the hydrogel between states also switched astrocytes between their reactive and naïve phenotypes. Science , this issue p. 808

Sophisticated statistical mechanics approaches and human intuition have demonstrated the possibility of self-assembling complex lattices or finite-size constructs. However, attempts so far have mostly only been successful in silico and often fail in experiment because of unpredicted traps associated with kinetic slowing down (gelation, glass transition) and competing ordered structures. Theoretical predictions also face the difficulty of encoding the desired interparticle interaction potential with the experimentally available nano- and micrometer-sized particles. To overcome these issues, we combine SAT assembly (a patchy-particle interaction design algorithm based on constrained optimization) with coarse-grained simulations of DNA nanotechnology to experimentally realize trap-free self-assembly pathways. We use this approach to assemble a pyrochlore three-dimensional lattice, coveted for its promise in the construction of optical metamaterials, and characterize it with small-angle x-ray scattering and scanning electron microscopy visualization.

DNA and peptides are two of the most commonly used biomolecules for building self-assembling materials, but few ex-amples 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 bear-ing complementary strands into micrometer-long one-dimensional arrays. We probed the effect of number of coils on self-assembly and demonstrated the formation of self-assembled structures through multiple routes: one-post assembly, formation of dimers and trimers and an alternating copolymer of two different origami bundles, 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.