CO2-Switchable Self-Healing Host Guest Hydrogels

The use of natural compounds to construct reversible networks is an attractive strategy in biomaterials design. Our design is based on a host guest pair of natural compounds beta-cyclodextrin and cholic acid through the use of a cholic acid dimer tethered with a poly(ethylene glycol) spacer, which subsequently served as a guest cross-linker to afford a hydrogel with copolymers bearing beta-cydodextrin pendants. The hydrogel after incision self-heals rapidly under ambient atmosphere as observed and confirmed by rheological measurements. To endow the hydrogels with reversibility and responsiveness, the addition of a CO2-switchable guest of benzimidazole followed by alternating treatments with CO2 and N-2 leads to a reversible sol gel transition due to the dynamic complexation between the cholic acid and beta-cydodextrin units. The CO2 responsiveness and the natural origin of the constituents make these self-healing hydrogels attractive as smart biomaterials.