Polyurethane-based bilayer wound dressing with snail mucin, Calendula extract, and zinc-doped carbon dots for enhanced therapeutic and antibacterial performance.

This study develops a bilayer wound dressing with enhanced antibacterial, mechanical, and biological properties, incorporating polyurethane, snail mucin, Calendula officinalis extract, and Zn-doped carbon dots. The bilayer system is designed as a multifunctional platform, achieved through electrospinning of core-shell nanofibers (core: polyurethane and Calendula extract; shell: polyvinyl alcohol and snail mucin) for the contact layer and a polyurethane foam for the top layer. Zn-doped carbon dots are incorporated into a porous polyurethane foam to improve antibacterial activity and mechanical integrity. Characterization of the dressing was conducted using FTIR, SEM, and TEM. Among the bilayer samples, the Bilayer containing 0.6 % Zn-doped CDs, exhibited the most favorable mechanical properties, with a balanced strength of 2.43 MPa and flexibility of 79.07 %, along with enhanced vapor permeability (2323.95 g/m2/day). Qualitative evaluation of wettability indicated improved hydrophilicity, promoting better moisture management for wound healing. It also demonstrated superior antibacterial effects, reducing S. aureus by 60 % and E. coli by 52 %. The contact layer showed promising results in drug release (64.83 % over 72 h), antioxidant activity (76.23 % at 72 h), and achieved nearly 100 % area closure in scratch assays during in vitro testing. The combination of good mechanical properties, satisfactory antibacterial activity, controlled release of therapeutic agents, and optimal moisture management makes this dressing an effective option for treating chronic wounds and preventing infections. These findings suggest the bilayer wound dressing as an advanced candidate for clinical applications in wound healing.