a) Schematic representation of dynamic covalent crosslinks formed by combining biopolymers modified with either furan or maleimide groups. b) Hydroxypropyl chitin (HPC, black) modified with furan groups and combined with PEG-bismaleimide crosslinks for hydrogel formation. Immediately, a thermo-responsive physical hydrogel forms due to interactions between HPC molecules, and over time, reversible Diels-Alder crosslinks form to stabilize the hydrogel structure. Adapted from Bi, et al.296 Copyright, 2019 Elsevier.