Biomimetic skin regeneration using a dual-layer scaffold/hydrogel: Polycaprolactone-gelatin electrospun scaffold incorporated with bromelain-silver nanoparticles and alginate hydrogel enriched with selenium-doped bioglass.

Skin regeneration remains a critical area of research due to the skin's pivotal roles in protection, sensation, and thermoregulation. This study introduces a novel biomimetic approach for enhancing skin regeneration by integrating a double-layered Polycaprolactone (PCL)-gelatin (Gel) electrospun scaffold containing Bromelain‑silver nanoparticles (Bro-AgNPs) with an alginate (Alg) hydrogel incorporating bioglass particles (BGPs) and selenium-doped BGPs (SeBGPs) as well as the injection of mesenchymal stem cells (MSCs) into wound edges. The Bro-AgNPs, incorporated into the scaffold, exhibited potent antimicrobial activity. The BGPs and SeBGPs promoted cell viability, achieving most cell proliferation at 20 % concentration in vitro. Physical characterization revealed that adding Bro-AgNPs increased the yield strength of the PCL-Gel-Bro-AgNPs scaffold to 1.59 ± 0.20 MPa compared to 1.30 ± 0.12 MPa for the PCL-Gel scaffold while maintaining comparable stiffness. Furthermore, the incorporation of BGPs and SeBGPs into Alg hydrogels reduced swelling ratios (after 24 h) to 162.1 ± 13.47 and 158.7 ± 15.25, and porosity to 72.82 ± 2.21 and 71.52 ± 2.76, respectively, compared to 208.8 ± 12.38 and 78.05 ± 2.60 % for Alg hydrogel. In vivo studies demonstrated that the SeBGPs + mesenchymal stem cells (MSCs) group achieved the highest wound closure at all experimental days. Histological evaluations on day 21 confirmed robust tissue regeneration, including thick epithelialization and well-organized collagen fibers, without inflammation. These findings demonstrate the composite's potential to support cellular activity, provide antimicrobial protection, and enhance mechanical properties, offering promise for clinical applications in skin tissue engineering.