Injectable Hydrogels With Modular Functionalities Enabled by Hydrazone Formation

ABSTRACT Injectable hydrogels have been recognized as an important class of soft materials for many enticing applications, yet it remains a challenge to program functions in one hydrogel substrate. Here, we report on dynamic hydrogels bearing injectable capacity and modular functionalities enabled by hydrazone formation. The hydrogel is generated by (cis, cis)‐cyclohexane‐1, 3, 5‐tricarbohydrazide ( H ) and aldehyde‐decorated hyaluronic acid (HA‐ A ) through hydrazone formation. Due to the intrinsic dynamic feature of hydrazone bonds, the hydrogels are capable of rapidly recovering against mechanical damage, which makes the hydrogels injectable. Importantly, the residual hydrazide groups in the hydrogel network allow for the incorporation of various molecular modules through hydrazone formation, enabling the hydrogels to have a variety of chemical functions. Moreover, relying on a hydrazone formation‐based self‐assembly system, we are even able to incorporate supramolecular nanofibers into the hydrogel network. The incorporation of supramolecular nanofibers increasing the plateau storage modulus from approximately 200 to 20 000 Pa and the yield strain from 180% to 360%, while preserving the injectable behavior. This work offers a simple approach for the development of injectable hydrogels with tunable functions for diverse applications such as drug delivery, tissue regeneration, and machine–human interfaces.