Multilayered electrospun membranes incorporating microspheres embedded nanofibers for enhanced wound healing

Multilayer membranes that coordinate the release of different drugs to match the various stages of wound healing while managing excessive tissue exudate represent a promising therapeutic approach. However, achieving precise control over the dual-drug release and effective absorption of excess tissue exudate remains a significant clinical challenge. This study employed a "nano-in-nano" microsphere-embedded fiber strategy to construct a multilayered dual drug delivery system (ML-DDS) via sequential electrospinning. The system comprises three layers: an outer fiber layer loaded with the antibacterial drug amikacin (Am), an intermediate layer of microspheres loaded with the anti-inflammatory drug quercetin (Qu) embedded within the fibers and an inner hydrophobic ethyl cellulose layer. Structural characterization showed that the intermediate layer had a diameter of approximately 500 nm with embedded microspheres predominantly ranging from 2.5 to 3.5 μm, while the inner EC fibers measured about 150 nm in diameter. The system leverages interfacial capillary forces to transport exudate from the hydrophobic layer to the drug-carrying layer. The water contact angles of the innermost hydrophobic layer and the outermost hydrophilic layer decrease to 0° within 40 s and 60 s, respectively. Drug release channels were formed after the ethyl cellulose layer absorbs water and swells. The release time of Am extended from 120 min in the single layer to 24 h in the ML-DDS. Both Qu and Am were continuously released in an amorphous form within 24 h through matrix erosion. ML-DDS up-regulated the expression of antioxidant-related metabolites, maintained mitochondrial function and promoted wound healing with a higher healing rate at day 14 compared to the control, along with enhanced collagen deposition, up-regulated CD31 expression, and reduced COX-2 levels. This study demonstrates that ML-DDS effectively integrates multilayered exudate management with controlled dual-drug delivery, providing a novel treatment strategy for skin wounds with excessive tissue exudate.