Electrospun polycaprolactone membranes as controlled delivery systems of polymyxin B for wound dressings applications

Electrospun polycaprolactone (PCL) nanofibrous membranes loaded with 2 2 % w/w polymyxin B (PMB) were developed as biodegradable antimicrobial wound dressings using two different solvent systems: organic (dichloromethane/dimethylformamide, OS) and acidic (acetic acid/formic acid, Acid). The choice of solvent significantly influenced fiber morphology, polymer crystallinity, mechanical properties, and drug-release kinetics. Both membranes exhibited well-defined bead-free nanofibers with diameters in the sub-micron range and porosity > 85 %. PMB release showed a marked initial burst within the first hour (≈ 35–55 % for OS membranes vs. ≈ 20–30 % for Acid membranes), followed by sustained diffusion over 7 days. Agar diffusion tests revealed strong antibacterial activity against Staphylococcus aureus (inhibition zone 1.5 mm for OS-PMB, growth inhibition under the sample for Acid-PMB) and Pseudomonas aeruginosa (5.0 mm and 0.6 mm, respectively), with no bacterial growth under any PMB-loaded samples. All membranes proved non-cytotoxic (> 80 % cell viability). The use of only two FDA-approved components, combined with a simple one-step electrospinning process and tunable release via solvent selection, offers a highly scalable and clinically translatable platform for the local delivery of polymyxin B in infected or at-risk wounds. ● Electrospun PCL membranes loaded with polymyxin B were developed as antimicrobial wound dressings. ● Solvent system (acidic vs. organic) strongly modulates fiber morphology and drug-release kinetics. ● Sustained release over 7 days with controllable initial burst and potent activity against S. aureus and P. aeruginosa. ● Excellent cytocompatibility and mechanical conformity for mobile wound sites. ● Simple two-component FDA-approved system highly suitable for scalable clinical translation.