Water-insoluble keratin nanofibres by electrospinning from water solutions

The electrospinning process is considered one of the most versatile and effective method for the production of continuous polymer-based nanofibrous media. The production of polymer nanofibers from water solution by electrospinning is considered green, up scalable and versatile. Unfortunately, few polymers with practical and technological application can be electrospun into nanofibers from water solutions because of the poor stability of the resulting nanofibers in a water environment. In this work, nanofibers were produced by electrospinning water solutions of a protein extracted from wool (i.e. keratin). Keratin is a protein characterized by a high amount of cysteine residues; it shows good solubility and processability in polar solvent such as formic acid. Keratin-based nanofibers produced by electrospinning enhance intrinsic properties of keratin in the binding of toxic substances such as formaldehyde, metal ions and dyes due to the nano-scale dimension, which increases the specific surface area. Moreover, keratin is biodegradable in vitro (by trypsin) and in vivo (in mice), and it support the growth and adhesion of fibroblasts and osteoblasts. In order to improve electrospinnability of keratin from water, poly(ethylene oxide) (PEO) was added to the solutions at the ratio keratin/PEO 70:30 as a sacrificial polymer. Resulting keratin-based nanofibers were made insoluble to water by a simple treatment at high temperature that induce cross-linking, expanding the range of applications of such a nano-material. It is demonstrated that PEO is almost completely washed out from nanofibers by simple soaking the membranes in water, and the resulting material maintains both nanofibrous structure and small-sized porosity. This technology can fabricate protein-based matrix suitable for the production of nanofibre membranes with functions useful in both biomedical and filtration applications. The dissemination of this work is supported through the 2BFUNTEX Project co-funded by the FP7 of the European Commission.