Degradation profiles of the poly(ε-caprolactone)/silk fibroin electrospinning membranes and their potential applications in tissue engineering

Degradation profiles are critical for the optimal application of electrospun polymer nanofibers in tissue regeneration, wound healing, and drug delivery systems. In this study, natural and synthetic polymers and their composites were subjected to in vivo transplantation and in vitro treatment with lipases, macrophages, and acetic acid to evaluate their degradation patterns. The effects of environmental stimulation, surface wettability, and polymer components on the degradation profiles of the electrospinning poly(ε-caprolactone)/silk fibroin (PCL/SF) nanofibers were first evaluated. In vivo degradation study demonstrated that bulk degradation, characterized by the transition from microfibers to nanofibers, and surface erosion, characterized by fusion between the microfibers or direct erosion from both ends of the microfibers, occurred in the electrospun membranes; however, bulk degradation dominated their overall degradation. Furthermore, the degradation rates of the electrospun PCL/SF membranes varied according to the composition, morphology, and surface wettability of the composite membranes. After the incorporation of silk fibroin (SF), the degradation rate of the SF/PCL composite membranes was faster, accompanied by larger values of weight loss and molecular weight (Mw) loss when compared with that of the pure poly(ε-caprolactone) (PCL) membrane, indicating a close relationship between degradation rate and hydrophilicity of the electrospinning membranes. The in vitro experimental results demonstrated that enzymes and oxidation partially resulted in the surface erosion of the PCL/SF microfibers. Consequently, bulk degradation and surface erosion coordinated with each other to enhance the hydrophilicity of the electrospinning membranes and accelerate the in vivo degradation.