Self-Healing Hydrogel with a Double Dynamic Network Comprising Imine and Borate Ester Linkages

A self-healing hydrogel enriched with properties from a double-dynamic network (DDN) that has been prepared via two dynamic linkages (imine and borate ester) by using a single polymeric cross-linker. The four-component Ugi reaction was used for easily synthesizing multifunctional poly(ethylene glycol) (MF-PEG) with a benzaldehyde group and phenylboronic acid group at each end of the chain. This MF-PEG simultaneously cross-linked with poly(vinyl alcohol) through the borate ester and glycol chitosan via an imine to generate a self-healing hydrogel with a unique DDN structure in seconds under mild conditions (pH ≈ 7, 25 °C). The prepared hydrogel showed enhanced strength and mucoadhesive abilities because of the complimentary interpenetrating dynamic networks. The DDN hydrogel showed satisfying biocompatibility and was further used in an in vivo mouse model. The hydrogel was injected to successfully deliver an antitumor drug and achieved a superior performance compared to traditional delivery methods. To the best of our knowledge, this is the first report of using the Ugi reaction to prepare a DDN self-healing hydrogel. We hereby propose a general strategy for the facile preparation of self-healing materials with improved properties. The strategy also opens a new avenue for synthesizing multifunctional/reinforced materials with the combination of dynamic chemistry and multicomponent reactions.