Smart Hydrogels Bearing Transient Gel-Sol-Gel Transition Behavior Driven by a Biocompatible Chemical Fuel

Chemically fueled smart supramolecular gels have been of great interest because of their unique time-dependent properties. However, the vast majority of the already developed examples undergo fueled sol-gel-sol transition, where the gel materials possess nonlinear properties and usually involve the use of toxic chemical fuels, remarkably impeding their real-life applications. Here, we report on supramolecular hydrogels that show dynamic gel-sol-gel transition behavior driven by the consumption of biocompatible cyclodextrin (CD). The addition of CD converts the static hydrogels into sols, which are capable of returning to the original gel states through the spontaneous enzymatic hydrolysis of CD. The gel-sol-gel transition process is highly dynamic and tunable. Importantly, the system resides in a stable gel state after the depletion of the fuel, which would be beneficial for its functions. As an application, the hydrogel is used as a conceptual smart adhesive for fuel-controlled adhesion of model tissues. This work may contribute to the development of biocompatible non-equilibrium materials for high-tech applications, especially in the field of biomedicine.