Core-Shell Electrospun Fibers with an Improved Open Pore Structure for Size-Controlled Delivery of Nanoparticles

Electrospun fiber meshes with controlled drug delivery properties have great potential for applications such as wound dressings, tissue engineering, and cancer treatment. However, controlling the drug release, especially from core-shell fibers, remains the main challenge. In this study, core-shell fibers were developed with silver nanoparticles (Ag NPs, as an antibacterial agent) loaded inside the core. The fiber shell was composed of polycaprolactone (PCL, shell matrix), polyethylene glycol (PEG, porogen), and zinc oxide nanoparticles (ZnO NPs). ZnO NPs were used in this study to improve the structure of pores in the shell (which serve as a diffusion pathway for Ag NPs) and thus to control the release rate. ZnO NPs associated with PCL, resulting in the formation of the PEG phase deeper in the fiber shell during the electrospinning process. Moreover, the diffusion/release rate of Ag NPs from electrospun fibers was fine-tuned with variation in particle size. Fibers were loaded with three size compositions of 20, 110 nm, or a mix of the two Ag NPs inside the fiber core. Release studies showed fast, slow, and intermediate delivery rates obtained with the defined Ag NPs. Fine-tuned release of Ag NPs confirmed the formation of open pores within a stable shell structure because controlling the release rate was only possible through this well-defined release pathway. Furthermore, tensile strength analysis revealed excellent mechanical stability of the fibers after pore formation.