Asymmetric composite wound dressing with hydrophobic flexible bandage and tissue-adhesive hydrogel for joints skin wound healing

The frequent bending leads to unstable connection between the joint wound and dressings, which increases the discomfort of patients. The current study developed an asymmetric wound dressing based the flexible bandage, whose one side was hydrophobic to protect the wound from the fluids in the environment, and the other side was the composite hydrogel based melatonin and polyacrylamide to adhere to the wound site and promote wound healing. The hydrophobic surface was constructed through spraying the paraffin/hexane solution for 40 times, then the surface with the water contact angle of 124.90° could hold the water droplet for 179.33s. The biocompatible composite hydrogel had good mechanical property with a high fracture strain of 1490.71% and adhesive property with 4.61 kPa to the porcine skin. It could also adhere to the skin and deform with the motion of joints. Moreover, a mouse full-thickness skin defect model was created to investigate the in vivo wound healing performance of the asymmetric wound dressing, the results showed that the hydrogel could promote the wound regeneration with higher wound closure rate (92.8%) than the dressing-free group (83.2%) after 2 weeks. Therefore, the asymmetric wound dressing is expected to be a competitive candidate in wound healing, especially for joint wounds.