Multi-triggered Supramolecular DNA/Bipyridinium Dithienylethene Hydrogels Driven by Light, Redox, and Chemical Stimuli for Shape-Memory and Self-Healing Applications.

Multi-triggered DNA/bipyridinium dithienylethene (DTE) hybrid carboxymethyl cellulose (CMC)-based hydrogels are introduced. DTE exhibits cyclic and reversible photoisomerization properties, switching between the closed state (DTEc), the electron acceptor, and the open isomer (DTEo) that lacks electron acceptor properties. One system introduces a dual stimuli-responsive hydrogel containing CMC chains modified with electron donor dopamine sites and self-complementary nucleic acids. In the presence of DTEc and the CMC scaffold, a stiff hydrogel is formed, cooperatively stabilized by dopamine/DTEc donor-acceptor interactions and by duplex nucleic acids. The cyclic and reversible formation and dissociation of the supramolecular donor-acceptor interactions, through light-induced photoisomerization of DTE, or via oxidation and subsequent reduction of the dopamine sites, leads to hydrogels of switchable stiffness. Another system introduces a stimuli-responsive hydrogel triggered by one of three alternative signals. The stiff, multi-triggered hydrogel consists of CMC chains cross-linked by dopamine/DTEc donor-acceptor interactions, and by supramolecular K+-stabilized G-quadruplexes. The G-quadruplexes are reversibly separated in the presence of 18-crown-6 ether and reformed upon the addition of K+. The stiff hydrogel undergoes reversible transitions between high-stiffness and low-stiffness states triggered by light, redox agents, or K+/crown ether. The hybrid donor-acceptor/G-quadruplex cross-linked hydrogel shows shape-memory and self-healing features. By using three different triggers and two alternative memory-codes, e.g., the dopamine/DTEc or the K+-stabilized G-quadruplexes, the guided shape-memory function of the hydrogel matrices is demonstrated.