Multifunctional bilayered nanofibrous scaffold of chitosan/poly(caprolactone) enriched with simvastatin and thymoquinone for accelerated diabetic wound healing

Chronic diabetic wounds cause a significant clinical and economic burden, necessitating advanced dressings that mimic the extracellular matrix. Therefore, in this study, a multifunctional bilayer nanofibrous scaffold was developed to achieve biphasic drug release, comprising an upper chitosan (CS) layer for immediate release of thymoquinone (TQ) to provide antioxidant and antibacterial effects, and a lower poly(caprolactone) (PCL) layer for sustained release of simvastatin (ST) to promote anti-inflammatory and pro-angiogenic responses. In silico docking was employed as an exploratory tool to assess interactions of ST and TQ with VEGFR-2/3, MMP-9, and SOD. Placebo, 1%, and 2% ST/PCL-TQ/CS NFs were fabricated and comprehensively characterized, with the 2% formulation demonstrating optimal performance. The 2% ST/PCL-TQ/CS NF scaffold exhibited smooth and uniform fibers (264.6 ± 38.74 nm), high porosity (81.85 ± 10.70%), swelling capacity (159.09 ± 4.13% at 24 h), excellent wettability (10.9°), appropriate WVTR (2193.33 ± 44.64 g/m²/day), tensile strength (1.66 MPa), and controlled biodegradation (82.79 ± 3.63% over 20 days). Sustained in vitro drug release was observed for TQ (98.82 ± 0.85%) and ST (35.5 ± 1.54%) over 120 h. The scaffold demonstrated high cytocompatibility (>90% cell viability), enhanced fibroblast migration (>90% wound closure at 48 h), hemocompatibility (<5% hemolysis), strong antioxidant activity (71.26% ROS scavenging), and significant antibacterial efficacy (p < 0.0001). In vivo evaluation using an STZ-induced diabetic rat model revealed significantly accelerated wound healing (p < 0.0001). Collectively, the developed TQ- and ST-loaded bilayer nanofibrous scaffold shows strong potential for diabetic wound management.