Preparation of electrospun silk fibroin nanofibers from solutions containing native silk fibrils

Electrospinning solutions containing native silk fibrils with varied diameter and length were firstly achieved by dissolving silk in CaCl2/Formic acid solvents. The structure of nanofibrils significantly improved the spinnability of electrospinning solution. The diameter of electrospun silk fibroin (SF) nanofibers increased from 40 nm to 1.8 mu m, which could be achieved through increasing the solution concentration from 2 to 10%, implying a good size control over a wide range in this process. The structure of SF nanofibers transferred from random coil to beta-sheet, before and after ethanol treatment, respectively. The mechanical properties of the SF nanofibers were improved significantly with stress and strain at break of 11.15 MPa and 7.66% in dry state, and 3.32 MPa and 174.0% in wet state. The strategy for preparing SF nanofibers with improved mechanical properties and fiber diameter control over a wide range provides benefits for the application of this material. (C) 2014 Wiley Periodicals, Inc.