Orthogonal Dual-Triggered Shape-Memory DNA-Based Hydrogels

DNA-based shape-memory hydrogels revealing switchable shape recovery in the presence of two orthogonal triggers are described. In one system, a shaped DNA/acrylamide hydrogel is stabilized by duplex nucleic acids and pH-responsive cytosine-rich, i-motif, bridges. Separation of the i-motif bridges at pH 7.4 transforms the hydrogel into a quasi-liquid, shapeless state, that includes the duplex bridges as permanent shape-memory elements. Subjecting the quasi-liquid state to pH 5.0 or Ag⁺ions recovers the hydrogel shape, due to the stabilization of the hydrogel by i-motif or C-Ag⁺-C bridged i-motif. The cysteamine-induced transformation of the duplex/C-Ag⁺-C bridged i-motif hydrogel into a quasi-liquid shapeless state results in the recovery of the shaped hydrogel in the presence of H⁺or Ag⁺ions as triggers. In a second system, a shaped DNA/acrylamide hydrogel is generated by DNA duplexes and bridging Pb²⁺or Sr²⁺ions-stabilized G-quadruplex subunits. Subjecting the shaped hydrogel to the DOTA or KP ligands eliminates the Pb²⁺or Sr²⁺ions from the respective hydrogels, leading to shapeless, memory-containing, quasi-liquid states that restore the original shapes with Pb²⁺or Sr²⁺ions.