A Shape-Memory DNA-Based Hydrogel Exhibiting Two Internal Memories.

The synthesis of a shape-memory acrylamide-DNA hydrogel that includes two internal memories is introduced. The hydrogel is stabilized, at pH 7.0, by two different pH-responsive oligonucleotide crosslinking units. At pH 10.0, one of the T-A⋅T triplex DNA bridging units is dissociated, resulting in the dissociation of the hydrogel into a shapeless quasi-liquid state that includes the other oligonucleotide bridges as internal memory. Similarly, at pH 5.0, the second type of bridges is separated, through the formation of C-G⋅C(+) triplex units to yield the shapeless quasi-liquid state that includes the other oligonucleotide bridges as internal memory. By reversible pH triggering of the hydrogel between the values 10.0⇔7.0⇔5.0, the two internal memories cycle the material across shaped hydrogel and shapeless quasi-liquid states. The two memories enable the pH-dictated formation of two different hydrogel structures.