Assessment of the Efficacy of an LL-37-Encapsulated Keratin Hydrogel for the Treatment of Full-Thickness Wounds

Wound healing remains a burdensome healthcare problemdue to moistureloss and bacterial infection. Advanced hydrogel dressings can helpto resolve these issues by assisting and accelerating regenerativeprocesses such as cell migration and angiogenesis because of the similaritiesbetween their composition and structure with natural skin. In thisstudy, we aimed to develop a keratin-based hydrogel dressing and investigatethe impact of the delivery of LL-37 antimicrobial peptide using thishydrogel in treating full-thickness rat wounds. Therefore, oxidized(keratose) and reduced (kerateine) keratins were utilized to prepare10% (w/v) hydrogels with different ratios of keratose and kerateine.The mechanical properties of these hydrogels with compressive modulusof 6-32 kPa and tan delta <1 render them suitablefor wound healing applications. Also, sustained release of LL-37 fromthe keratin hydrogel was achieved, which can lead to superior woundhealing. In vitro studies confirmed that LL-37 containing25:75% of keratose/kerateine (L-KO25:KN75) would result in significantfibroblast proliferation (similar to 85% on day 7), adhesion (similar to 90cells/HPF), and migration (73% scratch closure after 12 h and completeclosure after 24 h). Also, L-KO25:KN75 is capable of eradicating bothGram-negative and Gram-positive bacteria after 18 h. According to in vivo assessment of L-KO25:KN75, wound closure at day21 was >98% and microvessel density (>30 vessels/HPF at day14) wassignificantly superior in comparison to other treatment groups. ThemRNA expression of VEGF and IL-6 was also increased in the L-KO25:KN75-treatedgroup and contributed to proper wound healing. Therefore, the LL-37-containingkeratin hydrogel ameliorated wound closure, and also angiogenesiswas enhanced as a result of LL-37 delivery. These results suggestedthat the L-KO25:KN75 hydrogel could be a sustainable substitute forskin tissue regeneration in medical applications.