Chia Seed Mucilage-Based Bilayer Sponges Containing Zinc Oxide Nanoparticles for Wound Dressing

Effective wound management requires dressings that not only protect against infection but also support tissue regeneration. In this work, we present a chia seed mucilage/poly(vinyl alcohol) (CSMP)-zinc oxide (ZnO) bilayer wound dressing composed of a dense CSMP-ZnO hydrofilm as the outer protective barrier and a porous CSMP-ZnO sponge as the inner absorbent layer. The CSMP-ZnO bilayer wound dressing is fabricated via oven-drying and freeze-drying techniques, enabling a clear functional division between the outer protective layer and the inner wound-contacting layer and resulting in a stable and well-integrated structure. Mechanical testing demonstrates that the bilayer design synergistically combines the strength of the hydrofilm and the flexibility of the sponge, leading to improved mechanical integrity compared with single-layer structures, while the incorporation of ZnO nanoparticles enhances antibacterial performance. Water vapor permeability and contact angle analyses indicate that the dressing maintains a moist wound environment and exhibits tunable wettability, which are favorable for wound exudate management. In vitro evaluation using normal human dermal fibroblasts confirms good biocompatibility at low ZnO concentrations, and inhibition zone assays demonstrate effective antibacterial activity against both Gram-positive and Gram-negative bacteria. Furthermore, in vivo assessment using a murine scald wound model shows that the CSMP-ZnO bilayer wound dressing accelerates wound closure and promotes re-epithelialization compared with untreated wounds. Overall, this study highlights the CSMP-ZnO bilayer wound dressing as a multifunctional platform that integrates mechanical support, moisture regulation, antibacterial protection, and biocompatibility for advanced wound care applications.