Influence of the protocol used for fibroin extraction on the mechanical properties and fiber sizes of electrospun silk mats

Silk fibroin (SF) was regenerated using three of the most common protocols described in the bibliography for the dissolution of raw SF (LiBr 9.3 M, CaCl2 50 wt.% or CaCl2:EtOH:H2O 1:2:8 in molar ratio). The integrity of regenerated SF in aqueous solution was analyzed by SDS-PAGE and different profiles of degradation were observed depending on the protocol used. This fact was found to affect also the aqueous solubility of the freeze dried protein. These different SFs were used to produce electrospun mats using SF solutions of SF 17 wt.% in 1,1,1,1′,1′,1′-hexafluoro-2-propanol (HFIP) and significant differences in fiber sizes, elongation and ultimate strength values were found. This work provides a global overview of the manner that different methods of SF extraction can affect the properties of electrospun SF-mats and consequently it should be considered depending on the use they are going to be made for.

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► Protocol employed to dissolve raw SF affects diameter of electrospun fibers.
► Mw of SF polypeptides plays an important role in the fiber sizes of the mats.
► The highest aqueous solubility of lyophilized SF is when it is dissolved in LiBr 9.3 M.