A Biomimetic Composite Bilayer Dressing Composed of Alginate and Fibroin for Enhancing Full-Thickness Wound Healing

Full-thickness skin wound dressings are critically important for acute cutaneous wound healing. In this study, a bilayer sheet originating from biological macromolecules, mimicking skin hierarchy structure is developed. This sheet is composed of a steady silk fibroin (SF)/sodium alginate (SA) composite scaffold as the bottom regenerative layer and a SA film as the protective top layer. Scanning electron microscope analysis revealed the thickness of the top layer is approximate to 25 mu m and is tightly adhered to the composite scaffold layer with interconnected pores (approximate to 150 mu m). The bilayer sheets are displayed suitable water uptake capacity and high stability in water. The mass retention percentage of the bilayer sheets is approximate to 50% during three weeks of PBS degradation in vitro. The tensile strength of the bilayer sheets is significantly increased from 13.41 +/- 3.75 kPa (single scaffold) to 59.81 +/- 5.98 kPa. The composite scaffolds are more conducive to the growth and proliferation of human dermal microvascular endothelial cells. The experiment results in vivo are demonstrated superior and faster epithelialization and dermal regeneration in the wound treated with bilayer sheets because the sheets are accelerated wound closure, reduced the inflammatory response, and promoted protein synthesis in the extracellular matrix and blood vessel ingrowth.