Biopolymer Composite Nanofibers Electrospun from Regenerated Silk Fibroin and PHBV: Fabrication Method, Morphology and Thermal Stability

Silk fibroin (SF) and polyhydroxyalkanoate (PHA) have received increasing attention in recent years because of their unique biodegradability and biocompatibility. Studies on SF or PHA-based materials that are intended for use as biomaterials have attracted great attention, but few studies have been conducted on SF/PHA composite materials. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymers with varying ratios of the 3-hydroxyvalerate (HV) component are the most widely used member of PHAs. In this study, SF/PHBV composite nanofibers were prepared by electrospinning. The stability of the mixed solution of SF/PHBV was explored first. Fourier transform infrared (FTIR) spectroscopy was used to study the composition of the precipitates caused by mixing the SF solution with the PHBV solution. The morphology of the electrospun SF/PHBV composite nanofibers was observed by scanning electron microscopy (SEM). The average diameters of the pure PHBV, pure SF, SF/PHBV (the content ratio of solute SF/PHBV (w/w) was 10/1), and SF/PHBV (the content ratio of solute SF/PHBV (w/w) was 4/1) nanofibers were 495.12 ± 82.27, 67.88 ± 14.52, 171.10 ± 40.38, and 149.70 ± 28.57 nm, respectively. To discuss the influence of the electrospinning parameters on the spinning stability and morphology of the electrospun SF/PHBV (10/1) composite nanofibers, a univariate analysis experiment was designed. When the applied voltage was 15 kV, the feeding rate was 0.3 mL/h, and the tip-to-collector distance was 13 cm, the spinning stability, uniformity and formability of the SF/PHBV (10/1) composite nanofibers were excellent. In addition to FTIR analysis, X-ray diffraction (XRD) was also used to explore the structure of the electrospun SF/PHBV composite nanofibers. As the content of PHBV increased, the crystallinity of the SF/PHBV composite nanofibers could be improved. The thermogravimetric analysis (TGA) results indicated that the thermal stability of SF was better than that of PHBV. As the content of PHBV increased, the thermal stability of the SF/PHBV composite nanofibers would decrease.