Copper peroxide-loaded lignin-based non-isocyanate polyurethane foam for wound repair applications

Wound healing is a complex process and the mechanism of the tissue repair process involves many complex steps: inflammation, proliferation, and maturation. Wounds can be divided into two main categories: acute and chronic wounds. Non-healing wounds usually follow a bacterial infection. Many types of materials on the market have been developed for use as wound dressings. Polyurethane foam for wound dressings has many advantages over other materials, especially for moderate wounds and drainage. In this study, lignin-based non-isocyanate polyurethane foams were prepared using a green route by oxygen alkylation modification of enzymatically dissolved lignin, cyclic carbonation and polymerization with diamines to add a blowing agent. By loading CuO₂ on the surface of the prepared lignin-based non-isocyanate polyurethane foam, a pH-responsive wound dressing, named lignin-based non-isocyanate polyurethane/copper peroxide composite foam (named NIPU foam-CuO₂), was prepared, which can specifically release the strong oxidizing OH under acidic conditions. The composite foam can effectively kill the bacteria in the wound. The test results proved that the composite foam has excellent mechanical properties, thermal stability, and biocompatibility. NIPU-foam-CuO₂ 100 mM inhibited two types of bacteria, Escherichia coli, and Staphylococcus aureus, by up to 98 % and 95 % within 8 h, respectively. It also shows excellent performance in promoting wound healing in organism experiments as well as in the subsequent histological staining. The lignin-based NIPU foams of this work exhibit remarkable innovation and unique properties in terms of environmental friendliness, performance and antimicrobial resistance. At the same time, we also mention potential problems such as drug resistance in the long-term use of NIPU-CuO₂ foams.