Preparation and characterization of chitosan-based double-network hydrogels constructed with dopamine for improved mechanical and functional properties.

Chitosan (CS) is a naturally derived polysaccharide with intrinsic antibacterial activity, biocompatibility, and abundant reactive functional groups, making it attractive to develop multifunctional hydrogels. However, the practical application of CS hydrogels is often limited by insufficient functionality and structural tunability. In this study, a series of CS-based double-network hydrogels reinforced with acrylamide and dopamine, denoted as CS/p(AM/DA), were successfully prepared through combined chemical and physical crosslinking. CS served as the bioactive matrix, polyacrylamide formed the covalently crosslinked supporting network, and dopamine was introduced to generate polydopamine within the hydrogel system. The influence of dopamine incorporation on the rheological behavior, mechanical properties, structural features, swelling behavior, antibacterial activity, and antioxidant capacity was systematically investigated. All hydrogels exhibited typical elastic gel characteristics and retained satisfactory compressive properties. Structural analyses by FTIR, solid-state NMR, XRD, and SEM confirmed the formation of polydopamine and revealed changes in intermolecular interactions and internal morphology after dopamine incorporation. In addition, the hydrogels displayed pH-dependent swelling behavior. Functional evaluation showed that dopamine incorporation markedly enhanced antibacterial activity against Salmonella enterica and Listeria monocytogenes, as well as free radical scavenging capacity in DPPH and ABTS assays. Among all formulations, CS/p(AM/DA) with 0.75 mg/mL of dopamine exhibited the best balance of structural and bioactive performance. These findings demonstrate an effective strategy for engineering multifunctional CS-based hydrogels with enhanced antibacterial and antioxidant properties for food and biomedical applications.