Rheology and programmable gelation of DNA tadpoles.

DNA origami is a powerful method to achieve nanoscale folded structures. DNA origami is typically employed to create precisely and tightly folded objects often in small quantities and studied at single molecule scale. Here, we use the DNA origami method to design and fold polymers with complex topologies, and study their rheology and viscoelastic properties in dense conditions. First, we designed and purified topologically distinct DNA nanostructures - linear, circular, and "tadpole" polymers - to evaluate how polymer architecture influences entanglement and rheology. Despite their distinct topologies, we observe that all constructs obeyed universal rheological scalings, likely due to their short length. However, upon thermal annealing in the bulk, the DNA polymers displayed significantly different behaviours. Our results suggest that DNA polymers could be used to engineer thermoresponsive behaviours in complex fluids by introducing reversible and topology-dependent crosslinking.