FABRICATION OF SILK FIBROIN AND FLUORESCENT SILK FIBROIN FIBERS VIA ELECTROSPINNING

Abstract

Fibroin, derived from cocoon, is a natural polymer used widely and increasingly in various fields. In recent years, the development of fluorescent fibroin has gained attention in the field of tissue engineering, because of its biocompatibility, oxygen and water vapor permeability, biodegradability, and ability to be tested non-invasively.  In this work, silk fibroin and fluorescent silk fibroin fibers were fabricated via electrospinning, a simple process through which continuous submicron fibers can be produced. Degummed silk was extracted by dissolving in calcium chloride solution. The fibroin powder was dissolved in formic acid to form 10, 12, and 14 wt.% solutions.  Fluorescent fibroin solutions were achieved with addition of fluoresceine sodium (FS) as fluorescent dye.  The fluorescent solutions were prepared at 10 wt.% fibroin with varying FS concentration at 0.1, 0.3, and 0.5 wt.%, and at 0.5 wt.% FS with varying fibroin concentration at 10, 12, and 14 wt.%.   The fibroin solutions were fabricated into fibers via electrospinning using an applied voltage of 20 kV.  The surface morphology of silk fibroin fibers and fluorescent fibroin fibers, observed by scanning electron microscope (SEM), showed long continuous fibers. The average fiber diameter, in sub-micron range, was found to increase with fibroin concentration. The fluorescence intensity observed by fluorescence spectrophotometer was found to increase with decreasing fluorescent dye concentration. The functional groups and chemical structure of silk fibroin fibers analyzed by infrared spectroscopy (IR) were not affected by the addition of the fluorescent dye.