Rapid gelling, self-healing, and fluorescence-responsive chitosan hydrogels formed by dynamic covalent crosslinking

Chitosan hydrogels fabricated by covalent crosslinking exhibit tough mechanical properties and chemical stability. In this paper, debranched starch (DBS) is oxidized to dialdehyde debranched starch (DADBS), which is used as a new type of a crosslinking agent to prepare hydrogels. Chitosan hydrogels with excellent properties are prepared by dynamic Schiff-base crosslinking between the aldehyde groups in DADBS and the amino groups in chitosan. Hence, chitosan hydrogels exhibit a rapid gelation ability, with a gelation time of less than 30 s, and their storage modulus increases with the gelation time. By adjusting the molar ratio of the amino group of chitosan to the aldehyde group of DADBS and the reaction temperature, the hydrogels exhibit tunable elasticity and mechanical properties. Notably, scanning electron microscopy revealed the presence of 100-200 nm microgels in the hydrogel network, which could exert a strengthening effect on the mechanical properties of the hydrogels. In addition, chitosan hydrogels exhibit a rapid self-healing ability and remarkable fluorescence properties; also, they can be 3D printed in different shapes. Overall, the DADBS cross-linked chitosan hydrogels demonstrate potential applications in food, medicine, agriculture, and materials.