Importance of refrigeration time in the electrospinning of silk fibroin aqueous solutions

Refrigeration is a common method for preserving reconstituted silk fibroin (RSF) aqueous solutions during electrospinning experiments, but the effects of preservation time at 4 °C are still not well documented. In this work, we explore its effects on the viscosity, refractive index, and density values of RSF solutions at 19 wt%. Also, extensive characterization of the mechanical properties and fiber diameters of the resulting electrospun meshes are provided. Significant differences were found in elongation, Young´s modulus, and ultimate strength at different experimental times, and an increase in the viscosity values of the RSF solutions was detected for the first 12 days of storage. These solutions exhibited a continuous, slow gelation throughout the time in storage at 4 °C, and this phenomenon improved the performance of electrospinning after a certain period of refrigeration. The protocol used reduces the production cost of SF fiber-based scaffolds and avoids the use of harsh solvents and additives which could otherwise limit their use in potential biomedical applications.