Abstract
A nanofabrication method for the production of flexible core-shell structured silk elastin nanofibers is presented, based on an all-aqueous coaxial electrospinning process. In this process, silk fibroin (SF) and silk-elastin-like protein polymer (SELP), both in aqueous solution, with high and low viscosity, respectively, were used as the inner (core) and outer (shell) layers of the nanofibers. The electrospinnable SF core solution served as a spinning aid for the nonelectrospinnable SELP shell solution. Uniform nanofibers with average diameter from 301 ± 108 nm to 408 ± 150 nm were obtained through adjusting the processing parameters. The core-shell structures of the nanofibers were confirmed by fluorescence and electron microscopy. In order to modulate the mechanical properties and provide stability in water, the as-spun SF-SELP nanofiber mats were treated with methanol vapor to induce β-sheet physical crosslinks. FTIR confirmed the conversion of the secondary structure from a random coil to β-sheets after the methanol treatment. Tensile tests of SF-SELP core-shell structured nanofibers showed good flexibility with elongation at break of 5.20% ± 0.57%, compared with SF nanofibers with an elongation at break of 1.38% ± 0.22%. The SF-SELP core-shell structured nanofibers should provide useful options to explore in the field of biomaterials due to the improved flexibility of the fibrous mats and the presence of a dynamic SELP layer on the outer surface.
Highlights
Electrospinning is a relatively simple and effective method for the production of uniform, continuous fibers with diameters ranging from the nanoscale to the microscale
A Petri dish containing 200 mL MeOH was placed in the bottom chamber of a sealed desiccator, while the silk fibroin (SF) and SF-silk-elastin-like protein polymer (SELP) fiber mats with aluminum foil were placed on a ceramic desiccator plate in the top chamber
The results suggested that in this coaxial electrospinning process, the SF solution served as a the strength of the electric field exceeded that required for the material, so that the lower viscosity shell spinning aid to successfully prepare nanofibers from nearly nonelectrospinnable SELP solution
Summary
Electrospinning is a relatively simple and effective method for the production of uniform, continuous fibers with diameters ranging from the nanoscale to the microscale These micro/nanofibers in the form of nonwoven mats have been used widely in various biotechnologies, such as wound healing, tissue engineering, and drug delivery [1,2]. The electrospinning of SELP-1020-A and SELP-59A from formic acid and aqueous solution has been recently described [21] These electrospun fiber mats showed no cytotoxicity and supported adhesion and proliferation of human skin fibroblasts. The objective was to produce SF-SELP core-shell structured nanofibers by using the core solution as a spinning aid to electrospin nonelectrospinnable shell solutions This method would serve as a roadmap for the fabrication of functional nanofibers using nonelectrospinnable materials, such as genetically designed functional peptides. The effects of coaxial electrospinning process parameters, such as the flow rate of the core and shell solutions, the applied voltage, and the resultant fiber diameters were investigated
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