Multilayer pH-Responsive Hydrogels Fabricated via Two-Step Ionic Crosslinking: Towards Advanced Wound Dressing Materials

The design of hydrogel-based materials for wound care management requires the integration of multiple functionalities, including the capacity to maintain hydration, to prevent infection, and to adapt to the dynamic wound microenvironment. In this study, we fabricated innovative pH-reactive multilayer hydrogel patches based on ionically crosslinked alginate and incorporated with bioactive compounds, including Manuka honey, hyaluronic acid, and <i>Ribes nigrum</i> extract. The multilayer structure is coated with chitosan to improve water affinity and pH response. The patches are designed to respond to variable pH conditions typical of wound environments, with potential applicability to burn wounds. The hydrogel materials are characterized in terms of water content, swelling behavior, and water vapor transmission rate (WVTR). The chitosan-coated multilayer hydrogel exhibited high water uptake (swelling ratio up to 22.11 ± 0.25; water content 95.48 ± 0.05%) and controlled WVTR (~3450-3850 g/m²·day^-1), while degradation remained below 42% at pH 8 compared to >80% in single layers. Microstructural analysis is performed via optical microscopy to assess the morphology and uniformity of the multilayer system, while chemical characterization is conducted using Fourier-transform infrared (FTIR) spectroscopy. The results highlight the ability of the designed material to respond to pH variations and to accommodate bioactive agents within a structurally stable and hydrated network, suggesting its suitability for future investigations into controlled release applications.