Thin silk fibroin coating on electrospun fibers for sustained release of active compounds

Abstract

This study describes a method for producing a silk fibroin (SF) layer on fibrous structures formed by an amorphous polymer matrix for sustained drug diffusion. The presented model system is electrospun nanofibers of polycaprolactone (PCL) with ciprofloxacin (CIP). The nanofibers were covered with SF by immersion in its 0.2 wt% aqueous solution, which allows the forming on the nanofiber surface of a 50 nm layer. SF layer was crystallized by ethanol vapor and made SF insoluble in water for over 2 weeks due to an increase of β-sheet content in the protein secondary structure. SF does not affect the high surface-area-to-volume ratio of the fibers and makes them hydrophilic.The nanofibers reveal antibacterial properties against Gram-positive Staphylococcus aureus and -negative Klebsiella pneumoniae bacteria. The inhibition zone of bacteria growth after 24 h incubation is bigger for non-coated fibers indicating inhibition of the drug release by SF coating. Both kinds of fibers reveal the Fickian diffusion model of drug release, characterized by burst release for fibers non-covered with SF and sustained release for those covered with SF layer. The presented SF layer preparation method can facilitate the construction of future drug delivery systems and design materials with sustained release profiles.