Silk fibroin nanofiber. Electrospinning, properties, and structure

An electrospinning process was used to fabricate silk fibroin (SF) nanofiber nonwovens for wound dressing applications. The electrospinning of regenerated SF was performed with formic acid as a spinning solvent. For crystallization, as-spun SF nanofiber nonwovens were chemically treated with an aqueous methanol solution of 50%. The morphology, porosity and conformational structures of as-spun and chemically treated SF nanofibers were investigated by scanning electron microscopy (SEM), mercury porosimetry, wide angle X-Ray diffraction (WAXD), attenuated total reflectance infrared spectroscopy (ATR-IR), solid state C-13 CP/MAS nuclear magnetic resonance (NMR) spectroscopy. SEM micrograph showed that the electrospun SF nanofibers had an average diameter of 80 nm and a distribution in diameter ranging from 30 to 120 nm. The porosity of as-spun SF nanofiber nonwovens was 76.1%, indicating it was highly porous. Conformational transitions of the as-spun SF nanofibers from random coil to beta-sheet by aqueous methanol treatment occurred rapidly within 10 min, confirmed by solid-state C-13 NMR, ATR-IR, and X-Ray diffraction.