Kinetics of Lignin/Epigallocatechin Gallate Co-Release by Multiscale Structures of Dual-Dynamic Cross-Linked Hydrogels

The controlled-release hydrogel with dual-dynamic-bond networks provides superior tunability and stability through collaborative exchange mechanisms, which are often used for drug release. However, the impact of its multiscale structures involving various orientations and cross-linking densities on release kinetics is still poorly understood. Herein, a dual-dynamic-bond cross-linked hydrogel with tunable structures (orientation and cross-linking density) was developed, where the cross-linked network is formed by imine bonds between aminated lignin and oxidized carboxymethyl cellulose, as well as borate ester bonds between 3-aminophenylboronic acid-grafted sodium alginate and epigallocatechin gallate (EGCG). The results showed that the imine/borate ester cross-linked dual-network hydrogel exhibits pronounced pH responsiveness, enabling synergistic release of lignin and EGCG. Compared with the isotropic structures, the anisotropic hydrogel shows significantly faster release for lignin and EGCG along the aligned microchannels, which is attributed to the shortened mass-transfer pathways. In addition, driven by the stronger interfacial interaction of polar groups, the denser network attributed to the increased freeze-thaw cycles further accelerates the co-release of lignin and EGCG. The release process follows a non-Fickian diffusion mechanism and can be well described by the Korsmeyer-Peppas model. This work establishes a direct structure-release kinetics correlation, paving the way for the design of a dual-dynamic-bond hydrogel for precision delivery.