Periodic Reentrance Phase Transitions in DNA Origami Superlattices

Self-assembly of DNA origami polyhedral frames allows for the facile fabrication of designed ordered 3D nanomaterials. These DNA frames behave as patchy particles where short DNA extending from the vertices mediate directional inter-frame interactions. Frames with complementary DNA interactions assemble into superlattices with vertex-geometry dependent crystal phases. We discovered that linker mediated inter-frame interactions can change the coordination of DNA origami frames for the given frame geometry, effectively modifying frame valence. When frames are co-assembled with the complementary DNA linkers, crystalline superlattices of different phases are formed depending on the inter-frame coordination, as dictated by the linker motif. The combination of the frame geometry and linker molecular design dictate the resulting crystal structure. We show linker-mediated frames undergo a periodic reenterance phase transition with increasing linker length. The phenomenon was observed for frames with different geometry and exhibiting transitions between different phases, and the phase diagrams were mapped out. We provide a mechanistic understanding of the observed effect through a combination of experimental results from small-angle x-ray scattering and scanning electron microscopy, and computational simulation.