An injectable human hair-derived keratin-based bioadhesive sealant for nail bed tissue engineering: evaluation in a 3D nail bed wound model.

Nail bed defects caused by trauma or disease frequently result in nail plate loss, persistent pain, impaired hand function, and limited regenerative healing due to the highly specialized architecture of the nail bed. However, current treatment options are inadequate because they fail to simultaneously provide facile application, robust tissue adhesion, and regenerative support. Herein, we report KeratinGel, an injectable, biodegradable, and biocompatible human hair keratin-based tissue adhesive developed for nail bed repair. KeratinGel was engineered using a dual-cross-linking strategy that combined thiol-Michael addition and visible-light-induced photocross-linking, enabling rapid in situ gelation and stable integration into the tissue. To address the brittleness of keratin-based networks while maintaining cytocompatibility, reduced keratin (Keratin-SH), chosen for its biomimetic and bioactive properties, was incorporated into methacrylated gelatin (GelMA). The KeratinGel hydrogels were evaluated as tissue adhesives and sealants through lap shear, wound closure, and burst pressure tests. The adhesive and regenerative properties of KeratinGel were assessed using a novel three-dimensional (3D) in vitro nail bed wound model that mimics the layered cellular organization of the native tissue. Among the tested formulations, 5% KeratinGel exhibited the highest cytocompatibility, achieving approximately 80% cell viability. SEM and histological analyses confirmed a homogeneous cellular distribution and preservation of structural integrity. Ex vivo testing demonstrated formulation-dependent sealing performance, while keratin incorporation preserved comparable lap shear and wound closure strengths across the formulations. Gene expression analysis revealed the upregulation of MMP-3 and MMP-19, while p16 levels remained comparable to those in the control, indicating the absence of senescence-associated damage. Enhanced PCNA and KRT14 expression further underscored the regenerative potential of KeratinGel in nail-bed-tissue engineering.